T.O. 33B-1-2 TECHNICAL MANUAL NONDESTRUCTIVE INSPECTION GENERAL PROCEDURES AND PROCESS CONTROLS (ATOS) DISTRIBUTION STATEMENT C: Distribution authorized to U.S. Government agencies and their contractors, Administrative or Operational Use, 31 August 1986. Refer other requests for this document to AFRL/MLS-OL, Tinker AFB, Oklahoma 73145-3317. WARNING: This document contains technical data whose export is restricted by the Arms Export Control Act (Title 22, U.S.C. 2751 et seq.) or the Export Administration Act of 1979, as amended, Title 50, U.S.C., App. 2401, et seq. Violation of these export-control laws is subject to severe criminal penalties. Dissemination of this document is controlled under DoD Directive 5230.25. HANDLING AND DESTRUCTION NOTICE: Destroy by any method that will prevent disclosure of contents or reconstruction of the document. Published under the authority of the Secretary of the Air Force 1 JUNE 2006
Transcript
T.O. 33B-1-2TECHNICAL MANUAL
NONDESTRUCTIVE INSPECTIONGENERAL PROCEDURES AND PROCESS CONTROLS
(ATOS)
DISTRIBUTION STATEMENT C: Distribution authorized to U.S. Government agencies and their contractors, Administrative or OperationalUse, 31 August 1986. Refer other requests for this document to AFRL/MLS-OL, Tinker AFB, Oklahoma 73145-3317.
WARNING: This document contains technical data whose export is restricted by the Arms Export Control Act (Title 22, U.S.C. 2751 et seq.) orthe Export Administration Act of 1979, as amended, Title 50, U.S.C., App. 2401, et seq. Violation of these export-control laws is subject tosevere criminal penalties. Dissemination of this document is controlled under DoD Directive 5230.25.
HANDLING AND DESTRUCTION NOTICE: Destroy by any method that will prevent disclosure of contents or reconstruction of the document.
Published under the authority of the Secretary of the Air Force
INTRODUCTION......................................................vii 2.2.1 Equipment and Materials Re-quired for Cracked-ChromePanel Test...............................................2-8
SAFETY SUMMARY................................................ix 2.2.2 Procedure for Cracked-ChromePanel Test...............................................2-8
2.2.3 Testing for Failed Penetrant.......................2-91 NONDESTRUCTIVE INSPECTION 2.2.4 Testing for Failed Emulsifier/Re-
METHODS, GENERAL INFORMA- mover .....................................................2-9TION.....................................................................1-1 2.2.5 Testing for Failed Developer .....................2-9
2.2.6 Lipophilic Penetrant Systems.....................2-92.2.7 Water Washable Penetrant Sys-SECTION I INTRODUCTION..............................1-1
tems ........................................................2-91.1.1 Purpose........................................................1-12.3 System Performance Test with the1.1.2 Scope...........................................................1-1
PSM Starburst Panel (Depot1.1.3 Format of Procedures .................................1-1Only) ......................................................2-91.1.4 Knowledge of NDI .....................................1-1
2.3.1 Procedure for Performing the1.1.5 NDI Points-of-Contact................................1-1PSM Starburst Panel Test....................2-10
2.3.2 Response of PSM Panels .........................2-10SECTION II PROCESS CONTROLS...................1-32.3.3 Reading PSM Starburst Indica-
tions ......................................................2-101.2 Process Controls .........................................1-32.3.4 Cleaning PSM Panels ...............................2-111.2.1 Reason for Controlling the Pro-2.4 Inspection Booth Checks..........................2-11cess .........................................................1-32.5 Surface Wetting Test ................................2-111.2.2 Scope of Process Control ...........................1-32.6 Penetrant Brightness Test - (DE-
POT ONLY) ........................................2-112 FLUORESCENT LIQUID PENETRANT2.6.1 Penetrant Rapid Brightness TestINSPECTION.......................................................2-1
(FIELD LABS) ....................................2-122.7 Testing Concentration of Water
SECTION I FLUORESCENT LIQUID Based (Method ‘‘A’’) Pene-PENETRANT INSPECTION GENER- trants.....................................................2-12AL PROCEDURE................................................2-1 2.8 Testing Lipophilic Emulsifier
spection General Procedure...................2-1 ty Test ..................................................2-132.1.1 Preparation of Part......................................2-1 2.9 Hydrophilic Remover Refractome-2.1.2 Penetrant Application Procedure................2-2 ter Test .................................................2-132.1.3 Penetrant Removal Procedure ....................2-3 2.9.1 Hydrophilic Remover Hydrometer2.1.4 Developer Application and Drying Test.......................................................2-14
4 EDDY CURRENT INSPECTION ...........................4-1tion Test ...............................................2-162.10.3 Water-Soluble Developer Concen-
tration Test ...........................................2-16SECTION I EDDY CURRENT INSPEC-2.10.4 Dry Developer Contamination
TION GENERAL PROCEDURE .......................4-1Test.......................................................2-162.11 Cleaning Procedure for Process
4.1 Eddy Current General Procedure ...............4-1Control Test Panels..............................2-174.1.1 Approved Equipment..................................4-12.12 Water Pressure and Temperature4.1.2 Eddy Current Scanning Tech-Check ...................................................2-17
niques .....................................................4-54.1.3 General Eddy Current Inspection3 FLUORESCENT MAGNETIC PARTICLE
SECTION II EDDY CURRENT PRO-CESS CONTROL PROCEDURES ...................4-56SECTION I FLUORESCENT MAGNET-
IC PARTICLE INSPECTION GENER-4.2 Eddy Current Process ControlAL PROCEDURE................................................3-1
Procedures ............................................4-564.2.1 General Process Control for Eddy3.1 General Magnetic Particle Proce-
Current Inspection Probes anddures .......................................................3-1Standards ..............................................4-563.1.1 Required Equipment and Materi-
4.2.2 Probe Test .................................................4-56als ...........................................................3-14.2.3 Slot Test....................................................4-573.1.2 Preparation of Part......................................3-1
3.1.3 Selecting Type of Magnetizing5 ULTRASONIC INSPECTION.................................5-1Current ...................................................3-2
3.1.4 Longitudinal Magnetization (CoilShots) .....................................................3-2 SECTION I ULTRASONIC INSPEC-
3.1.5 Longitudinal Magnetism Induced TION GENERAL PROCEDURE .......................5-1by Portable Yokes..................................3-6
3.1.6 Circular Magnetism Produced byDirect Contact ........................................3-7 SECTION II ULTRASONIC INSPEC-
3.1.7 Demagnetizing Test Parts.........................3-11 TION PROCESS CONTROL..............................5-23.1.8 Post-Cleaning Test Parts After
Magnetic Particle Inspection ...............3-12 5.1 Ultrasonic Inspection Process3.1.9 QQI Shims ................................................3-12 Control ...................................................5-23.1.10 Magnetic Particle Inspection Inter- 5.1.1 Procedure for Determining Verti-
pretation ...............................................3-12 cal Linearity Limits (ASTMBlocks) ...................................................5-2
SECTION II FLUORESCENT MAG- 5.1.2 Procedure for Determining Hori-NETIC PARTICLE PROCESS CON- zontal Linearity Limits (Type 2TROL PROCEDURES ......................................3-14 IIW Block) .............................................5-3
5.1.3 Procedure for Determining Inspec-3.2 System Effectiveness Check tion System Sensitivity (ASTM
for New Bulk Suspension....................3-18 alignment (Skew Angle)......................5-163.2.8 Particle Concentration Test ......................3-18
SECTION I RADIOGRAPHIC INSPEC- 6.1.3 Developer Testing.......................................6-2TION GENERAL PROCEDURE .......................6-1 6.1.4 Fixer Control...............................................6-3
6.1.5 Safelight Filter Check.................................6-36.1.6 Interlock Operational Check ......................6-3SECTION II RADIOGRAPHIC INSPEC-6.1.7 Survey Meter Operational Check...............6-3TION GENERAL PROCEDURE .......................6-2
LIST OF ILLUSTRATIONS
Number Title Page Number Title Page
3-1 Longitudinal Magnetization in a Coil ............ 3-2 4-13 Impedance Plane Response (with High3-2 Magnetic Field Produced by a Portable Pass Filter) from the 0.005 Inch
Yoke ........................................................... 3-7 Notch (4340 Steel) with Acceptable3-3 Circular Magnetic Field Produced by Signal-To-Noise ....................................... 4-21
Direct Contact ............................................ 3-8 4-14 Typical Lift-off Response with Phase3-4 Circular Magnetism Using a CBC ................. 3-9 Adjusted Correctly ................................... 4-253-5 Circular Magnetism Using a CBC on 4-15 Impedance Plane Display ............................. 4-26
Ring-Shaped Parts.................................... 3-10 4-16 Properly Calibrated Sweep Display ............. 4-263-6 Quantitative Quality Indicators (QQI) ......... 3-12 4-17 Acceptable Noise Level from Clean3-7 Ketos Ring .................................................... 3-15 Hole .......................................................... 4-273-8 Black Light Intensity .................................... 3-17 4-18 30% PTP Signal Requires Evaluation.......... 4-273-9 Centrifuge Tube ............................................ 3-19 4-19 Establishing Sync Zero Position of the4-1 Eddy Current Reference Standard.................. 4-3 Nortec Spitfire Scanner............................ 4-294-2 Alternate Surface Eddy Current Refer- 4-20 Establishing Sync Zero Position of the
ence Standard ............................................. 4-5 Nortec Minimite Scanner......................... 4-304-3 Required Scanning Directions ........................ 4-7 4-21 Establishing Top, Center Scanner Zero4-4 Scanning Around Fastener with Flush Position (Method B)................................. 4-30
Heads .......................................................... 4-8 4-22 Sweep Display with Alarm Gates ................ 4-314-5 Scanning Around Fastener with Pro- 4-23 Impedance Plane Display with Alarm
truding Heads ............................................. 4-9 Gates ......................................................... 4-324-6 Scanning Radii ................................................ 4-9 4-24 Split Screen Display with Sweep Dis-4-7 Signal Response from 0.020 inch Deep play Alarm Gates and Impedance
Notch in Aluminum ................................. 4-13 Plane Display Lift-off Limits .................. 4-334-8 Responses from 0.005, 0.010, and 0.020 4-25 Example of Crack Indication in Hole
inch Deep Notches (Aluminum) with with Noise Level Greater thanAcceptable Signal-to-Noise ..................... 4-14 30%Fsw .................................................... 4-34
4-9 Indication Exceeding 10% Vertical De- 4-26 Example of Excessive Noise in theflection...................................................... 4-15 Sweep Mode (Left) and in the Impe-
4-10 80% FSH Signal from a 0.020 Inch dance Plane Mode (Right) ....................... 4-34Deep Notch............................................... 4-18 4-27 Lift-off Response with Phase Adjusted
4-11 Impedance Plane Display of 80% Ptp Correctly ................................................... 4-38Signal from the 0.020 Inch Deep 4-28 Idealized Response Illustrating Mini-Notch ........................................................ 4-19 mum Separation Between Lift-off
4-12 Impedance Plane Response (without and EDM Notch Response ...................... 4-39High Pass Filter) from the 0.005 4-29 Properly Calibrated Sweep DisplayInch Notch (4340 Steel) with Ac- (Steel) ....................................................... 4-40ceptable Signal-To-Noise......................... 4-20
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T.O. 33B-1-2
4-30 Acceptable Noise Level from Clean 5-1 Use the Type 2 IIW Block to CheckHole (Steel) .............................................. 4-40 Horizontal Linearity ................................... 5-3
4-31 Signal from Hole Subject to Evaluation 5-2 Use Type 2 IIW Block to Check Back(Steel) ....................................................... 4-41 Surface Resolution ..................................... 5-5
4-32 SYNC Zero Position of the Nortec Spit- 5-3 Use a Type 2 IIW Block to Check En-fire Scanner (Steel) .................................. 4-43 try Surface Resolution ............................... 5-7
4-33 SYNC Zero Position of the Nortec 5-4 Straight Beam Distance CalibrationMiniMite Scanner (Steel)......................... 4-44 with IIW Block ........................................ 5-10
4-34 SYNC Zero Position (Method B) 5-5 Straight Beam Distance with Miniature(Steel) ....................................................... 4-44 Angle Beam Block................................... 5-11
4-35 Response from 0.030 Inch Interface 5-6 Angle Beam Distance Calibration withNotch with Phase at a 45 Degree IIW Block................................................. 5-13Angle ........................................................ 4-49 5-7 Angle Beam Distance Calibration with
4-36 Example of Properly Calibrated Sweep Miniature Angle Beam Block.................. 5-14Display (Titanium) ................................... 4-49 5-8 Point of Incidence Determination with
4-37 Example of Acceptable Noise Level IIW Block................................................. 5-15from Clean Hole. Noise Level Shall 5-9 Point of Incidence Determination withNot Exceed 10% FSH from Baseline ..... 4-50 Miniature Angle Beam Block.................. 5-16
4-38 Display of Signal from Hole That is 5-10 Beam Misalignment (Skew Angle) .............. 5-16Subject to Evaluation (Titanium) ............ 4-50 5-11 Skew Angle Measurement............................ 5-17
4-39 Establishing SYNC Zero Position of the 5-12 Angle Determination with Type 2 IIWNortec Spitfire Scanner (Titanium) ......... 4-52 Block......................................................... 5-18
4-40 Establishing SYNC Zero Position of the 5-13 Angle Determination with MiniatureNortec MiniMite Scanner (Titanium) ..... 4-53 Angle Beam Block................................... 5-18
4-41 Establishing SYNC Zero Position of theNortec Spitfire Scanner (Method C) ....... 4-53
LIST OF TABLES
Number Title Page Number Title Page
1-1 Frequency for Process Control ......................... 1-3 4-6 Settings Prior to Calibration for Surface2-1 Fluorescent Penetrant Advantages and Scanning of Steel Parts .............................. 4-16
Limitations.................................................... 2-1 4-7 Nortec 2000D Calibration Settings Scan-2-2 Material and Minimum Penetrant Sensi- ning of Aluminum Fastener Holes ............ 4-23
tivity Level ................................................... 2-2 4-8 Frequency Settings Fastener Hole Scan-2-3 Penetrant Dwell Times...................................... 2-3 ning of Aluminum, Non-Ferrous Al-2-4 Developer Dwell Times .................................... 2-5 loys, and Weakly Ferromagnetic3-1 Fluorescent Magnetic Particle Advan- Alloys.......................................................... 4-24
tages and Limitations ................................... 3-1 4-9 Filter Settings vs. Hole Diameter ................... 4-243-2 Coil Size vs. Maximum Part Diameter 4-10 Sweep Display Alarm Gate Settings .............. 4-31
for Bottom of Coil Shot............................... 3-3 4-11 Impedance Plane Display Alarm Gate3-3 Typical Current for Five-Turn Coil with Settings ....................................................... 4-31
Part at the Bottom of Coil ........................... 3-4 4-12 Settings Prior to Calibration of Nortec3-4 Ring Specimen Indications ............................. 3-15 2000D/2000D+ Fastener Hole Scan-3-5 Empirical Black Light Intensity Require- ning of Magnetic Steel Parts ..................... 4-36
ments at Various Ambient Light 4-13 Filter Settings vs. Hole Diameter ................... 4-37Levels for Portable Inspections ................. 3-18 4-14 Nortec 2000D Initial Calibration Settings
4-1 Reference Standard Materials ........................... 4-2 for Rotary Scanning of Fastener Holes4-2 Nortec 2000D Initial Settings for Deter- in Titanium Parts ........................................ 4-47
mining Lift-off Compensation ..................... 4-6 4-15 (Titanium) Filter Settings vs. Hole Diam-4-3 Nortec 2000D Inspection Frequencies by eter .............................................................. 4-47
5-5 Dead Zone Set-up ............................................. 5-7 5-8 Straight Beam Distance .................................. 5-105-6 Limits of Boundary Surface Resolution........... 5-8 5-9 Auto Calibration Procedures........................... 5-125-7 Auto Calibration Procedures............................. 5-8 5-10 Angle Beam Distance Calibration .................. 5-13
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T.O. 33B-1-2
INTRODUCTION
1. PURPOSE.
This manual provides information necessary for operating and maintaining the Non Destructive Inspection generalprocedures and process controls.
2. IMPROVEMENT REPORTS.
Recommendations for improvements to this technical order will be submitted on AFTO Form 22, Publication ChangeRequest, in accordance with TO 00-5-1. Complete forms will be forwarded to 448 MSUG/GBMUH, Tinker AFB, OK 73145.
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T.O. 33B-1-2
SAFETY SUMMARY
1. GENERAL SAFETY INSTRUCTIONS.
The following are general safety precautions and instructions individuals must understand and apply during many phases ofoperation and maintenance to ensure personal safety, health, and the protection of Air Force property. Portions of this may berepeated elsewhere in this publication for emphasis. Additional safety precautions are contained in AFOSH STD 91-110,AFOSH STD 91-501, and Army: AR 385-10 paragraph 1.
2. SHALL, SHOULD, MAY, AND WILL.
Use the word ‘‘SHALL’’ whenever a manual expresses a provision that is binding. Use ‘‘SHOULD’’ and ‘‘MAY’’ wheneverit is necessary to express non-mandatory provisions. ‘‘WILL’’ may be used to express a declaration purpose. It may benecessary to use ‘‘WILL’’ in cases where simple futurity is required (e.g., ‘‘Power for the meter WILL be supplied by theship’’).
3. WARNINGS, CAUTIONS, AND NOTES.
WARNING
This highlights an essential operating or maintenance procedure, practice, condition statement, etc., which if notstrictly observed, could result in injury to, or death of, personnel or long term health hazards.
CAUTION
This highlights an essential operating or maintenance procedure, practice, condition, statement, etc., which if notstrictly observed, could result in damage to, or destruction of, equipment or loss of mission effectiveness.
WARNINGS and CAUTIONS are used in this manual to highlight operating or maintenance procedures, practices,conditions, or statements considered essential to protection of personnel (WARNING) or equipment (CAUTION).WARNINGS and CAUTIONS immediately precede the step or procedure to which they apply. WARNINGS andCAUTIONS consist of four parts: a heading (WARNING, CAUTION, or Icon); a statement of the hazard, minimumprecautions, and possible result if disregarded. NOTEs may precede or follow the step or procedure, depending upon theinformation to be highlighted. The heading used and the definitions are as follows.
NOTE
This highlights an essential operating or maintenance procedure, condition, or statement.
4. HAZARDOUS MATERIALS WARNINGS.
Consult the Material Safety Data Sheets (MSDS) (Occupational Safety and Health Administration (OSHA) Form 20 orequivalent) for specific information on hazards, effects, and protective equipment requirements. If you do not have a MSDSfor the material involved, contact your supervisor, or the base Safety or Bioenvironmental Engineering Offices.
5. SAFETY PRECAUTIONS.
The following safety precautions SHALL be observed while performing procedures in this manual.
• CAUTION AROUND LIVE CIRCUITS. Operating personnel must observe safety regulations at all times. Do notreplace components or make adjustments inside equipment with the electrical supply turned on. Under certain conditions,such as residual charges on capacitors, danger may exist even when the power control is in the off position. To avoid injuries,always disconnect power, discharge and ground circuit before touching it. Adhere to all lockout/tag-out requirements.
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T.O. 33B-1-2
• DO NOT SERVICE ALONE. Under no circumstances should any persons perform maintenance on the equipmentexcept in the presence of someone who is capable of rendering aid.
• RESUSCITATION. Personnel working with or near high voltage SHALL be familiar with modern methods ofresuscitation. Such information may be obtained from the Director of Base Medical Services.
• FINGER RINGS AND OTHER JEWELRY. Remove rings, watches, and other metallic objects during all maintenanceactivity that may cause shock, burn, or other hazards. Snagged finger rings have caused many serious injuries.
• PERSONAL PROTECTIVE EQUIPMENT (PPE). The work center supervisor SHALL contact the Base Bioenviron-mental Office and/or the Base Safety Office for a list of approved protective clothing/equipment (gloves, apron, eyeprotection, etc.) for the chemicals, materials, and tools being used. Use nitrile, neoprene, or other protective gloves, aprons,and goggles. The Base Bioenvironmental Office SHALL approve these items in writing. PPE SHALL be worn when andwhere directed to do so by the Base Bioenvironmental Office.
• COMPRESSED AIR. Use of compressed air can create an environment of propelled foreign particles. Excessive airpressures MAY cause injury. NDI Labs typically use compressed air reduced to less than 30-psig and used with effectivechip guarding and personal protective equipment (PPE). Lab supervisors SHALL contact the local Wing Safety Office forguidance.
• PRECAUTIONS WITH EYEWEAR. Personnel who wear contact lenses shall identify this to their supervisor, refer tothe appropriate material safety data sheets (MSDS) for possible hazards involved in wearing contact lenses around chemicals,and abide by the guidance for that chemical. Photochromatic lenses (lenses that darken when exposed to sunlight orultraviolet light), sunglasses, and colored contacts reduce the visibility of fluorescent indications. This leads to the possibilityof faint indications not being seen by the inspector. Therefore, glasses with photochromatic lenses, sunglasses or coloredcontact lenses SHALL NOT be worn when performing fluorescent penetrant or fluorescent magnetic particle inspections.
• SAFETY WITH BLACK LIGHTS. Black light bulbs SHALL NOT be operated without proper filters. Cracked,chipped, or ill-fitting filters SHALL be replaced before using the lamp. Unfiltered ultraviolet radiation can be harmful to theeyes and skin. Prolonged direct exposure of hands to the filtered black light main beam may be harmful. Suitable glovesSHALL be worn when exposing hands to the main beam; UV-A filtering safety glasses, goggles, or face shields SHALL alsobe worn. A black light bulb heats the external surfaces of the lamp housing. The temperature of some operating black lightbulbs reaches 750°F (399°C) or more during operation. The temperature is not high enough to be visually apparent, but it ishigh enough to cause severe burns with even momentary contact of exposed body surfaces. Extreme care SHALL beexercised to prevent contacting the housing with any part of the body. These temperatures are also above the ignition or flashpoint of fuel vapors. These vapors WILL burst into flames if they contact the bulb. These black lights SHALL NOT beoperated when flammable vapors are present.
• SOLVENTS, CHEMICALS, AND OTHER TOXIC MATERIALS. Solvents used may contain aromatic, aliphatic, orhalogenated compounds. Many are flammable while others may decompose at elevated temperatures. Solvents SHALL bekept away from heat and open flames. Vapors also may be harmful to personnel, thus adequate ventilation SHALL be used.Contact with skin and eyes SHALL be avoided. Solvents SHALL NOT be ingested. Waste material disposal SHALL beaccording to applicable directives or as specified by the local Bioenvironmental Engineer/Environmental ManagementOffices. Keep cleaners/chemicals in approved safety containers and maintain minimum quantities. Some cleaners/chemicalsmay have an adverse effect on skin, eyes, and respiratory tract. Observe manufacturer’s WARNING labels; Material SafetyData Sheet (MSDS) instructions for proper handling, storage, and disposal; and current safety directives. Use cleaners/chemicals only in authorized areas. Discard soiled cloths into approved safety cans. Consult the local BioenvironmentalEngineer for specific protective equipment and ventilation requirements.
• USE OF RESPIRATORS. Dry developer particles are not toxic materials. However, like any solid foreign matter, theySHALL NOT be inhaled. Air cleaners, facemasks, or respirators may be required. The Base Bioenvironmental EngineerSHALL be consulted if the process generates airborne particles.
• EXPOSURE TO SF6 GAS. Exposure to excessive amounts of Sulphur Hexafluoride (SF6) gas can cause asphyxiationby displacing oxygen in the air. Care SHALL be taken not to release large quantities of SF6 gas into unvented work areas.The amount leaked into the air while performing normal X-ray tube repair does not create an asphyxiation hazard. When SF6is heated, it liberates hazardous fluorine gas into the air. This possibility of producing fluorine gas exists in most X-ray tubeheads. Precautions SHALL be taken to guard against the inhalation of the gas released from X-ray tubes that have beenenergized.
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T.O. 33B-1-2
• IMPROPER CLEANING PROCEDURES. Improper cleaning procedures/materials can cause severe damage to thematerial under inspection. Preparation of parts to include but not limited to paint removal and chemical etching SHALL beaccomplished by maintenance personnel who are properly trained, highly skilled, and experienced in those particularspecialties and are aware of the effects on the part/material due to the use of these chemicals and methods. T.O. 1-1-691applies to the Air Force, T.M. 1-1500-344-23 applies for the Army; and N.A. 01-1A-509 applies for the Navy and MarineCorps.
• PRECAUTIONS DURING RADIOGRAPHIC INSPECTIONS. Exposure to excessive X or gamma radiation isharmful to personnel and especially an unborn fetus. All applicable safety precautions SHALL be complied with. While mostX-ray equipment is designed to minimize the danger of exposure to direct or stray radiation, certain precautions SHALL beobserved. Failure to comply with safety procedures may result in serious injury to personnel. Coordinate all operationalchanges with the Base Radiation Safety Officer. Radiation protection requirements are discussed further in (see T.O. 33B-1-1) for additional safety information. (NAVY ONLY: Radiation safety guidance is provided by NAVSEA S040-AARAD-010.)
• PRECAUTIONS DURING PENETRANT INSPECTIONS. Penetrant inspection includes the use of black light andexposure to flammable chemicals that may affect skin, eyes, and respiratory tract. Care SHALL be exercised when using hotblack lights so as not to burn hands, arms, face, or other exposed body areas. Wear nitrile, neoprene, or other approved glovesand keep the insides of gloves clean when handling penetrant materials. When processing parts through chemicals in thestationary lines, chemical goggles, rubber apron, and protective gloves SHALL be worn. During times of portable inspection,a minimum of protective gloves and eye protection SHALL be worn. Consult your local Bioenvironmental and Safety officesfor further guidance. Ensure the Base Bioenvironmental Office performs an adequate surface area exhaust ventilationevaluation annually. When recommended by the Base Bioenvironmental Engineer, an approved respirator SHALL be wornwhen working in areas where adequate ventilation cannot be practically provided. The use of visible dye penetrant isPROHIBITED on engine, aircraft, and missile parts except for those with specific engineering approval for each inspection.
• Magnetic particle inspection includes exposure to chemicals, ultraviolet light, and electrical current. Rubber insulatingfloor matting, rated for the voltage of the equipment being worked on, SHALL be used in front of magnetic particle units.Care SHALL be exercised when using hot black lights so as not to burn hands, arms, face, or other exposed body areas. Wearnitrile, neoprene, or other approved gloves and keep the insides of gloves clean when handling magnetic particle materials.When processing parts through chemicals in the stationary lines, chemical goggles, rubber apron, and protective glovesSHALL be worn. During times of portable inspection, a minimum of protective gloves and eye protection SHALL be worn.Consult your local Bioenvironmental and Safety offices for further guidance. Ensure the Base Bioenvironmental Officeperforms an adequate surface area exhaust ventilation evaluation annually.
6. ACCESS TO SURFACES AND PART PREPARATION.
Access to aircraft surfaces (e.g. panel removal) requiring Nondestructive Inspection, SHALL be accomplished bymaintenance personnel who have properly documented training and are highly experienced in those particular specialties.Improper cleaning procedures/materials can cause severe damage to the material under inspection. Preparation of parts toinclude, but not limited to, paint removal and chemical etching SHALL be accomplished by maintenance personnel who areproperly trained, highly skilled, and experienced in those particular specialties and are aware of the effects on thepart/material due to the use of these chemicals and methods. T.O. 1-1-691 applies for the Air Force, T.M. 1-1500-344-23applies for the Army, and N.A. 01-1A-509 applies for the Navy and Marine Corps.
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T.O. 33B-1-2
CHAPTER 1NONDESTRUCTIVE INSPECTION METHODS, GENERAL INFORMATION
SECTION I INTRODUCTION
1.1 INTRODUCTION.
1.1.1 Purpose. Nondestructive Inspection (NDI) is the inspection of a structure or component in any manner that will notimpair its future usefulness. The purpose of the inspection may be to detect flaws, measure geometric characteristics,determine material structure or composition, or it may characterize physical, electrical, or thermal properties without causingany changes in the part. The five standard NDI disciplines include:
• Liquid Penetrant• Magnetic Particle• Eddy Current• Ultrasonic• Radiography
1.1.2 Scope. This publication contains general procedures and process controls for NDI methods and SHALL be usedonly when specific inspection instructions are not available and as test part geometry, material, coating, and surface finishpermits. It is intended that these general procedures be used as directed and with guidance from an NDI Level 3 or theengineering authority for the weapon system or commodity item being tested. The procedures in this manual can be used as astand-alone inspection instruction when T.O. 33B-1-2, T.O. 33B-1-1 or a MIL Standard is referenced as the inspectiondocument, or when no specific inspection criteria exist. The general procedures are written for use by an experience level 2 orequivalent (5-level) technician. In some instances, an experienced task certified level 1 or equivalent (3-level) technician caneffectively use the general procedures. It is recommended that an experienced level 2 or higher technician thoroughly reviewthe procedures with the task certified level 1 technician prior to approving use in an actual inspection. The process controlprocedures are written so that a level 1 or equivalent (3-level) technician can perform the checks with limited training andsupervision. Guidance for development of NDI procedures is contained in MIL-DTL-87929C, Appendix F. NDI procedurescontained in this manual are detailed step-by-step instructions with illustrations so a qualified NDI technician can perform therequired inspection. In addition, this manual provides some general safety guidance for NDI inspectors. Other safetyguidelines may apply and SHALL be used as required.
1.1.3 Format of Procedures. Though MIL-DTL-87929C is a directive for NDI Work Packages, it provides the properformat for detailed/repetitive NDI procedures. To ensure continuity of inspections, all on and off equipment maintenanceNDI manuals (e.g. -9, -36, etc.) SHALL be written to adopt the special requirements of MIL-DTL-87929C into MIL-PRF-83495 when writing NDI procedures for these maintenance manuals. An individual qualified and certified to Level 3 inaccordance with NAS 410 in the inspection method being used, SHALL approve all written procedures.
1.1.4 Knowledge of NDI. NDI methods in the hands of a trained and experienced technician are capable of detectingflaws or defects with a high degree of accuracy and reliability. It is important maintenance-engineering personnel are fullyknowledgeable of the capabilities of each method but it is equally important they recognize the limitations of the methods.Rarely should an NDI method ever be considered conclusive. Often but not always, a defect indication detected by onemethod must be confirmed by another method to be considered reliable. The equipment is highly sensitive so the limits foracceptance and rejection are as much a part of an inspection as the method itself. As an example, ultrasonic inspection criteriamust be designed to overlook these ‘‘normal’’ indications and to discriminate in favor of the discontinuities that will affectthe service of the component.
1.1.5 NDI Points-of-Contact. To fully utilize the content of this Technical Order it may become necessary to contactmembers of the Air Force NDI engineering community for technical guidance. The following points-of-contact are current atthe time of publishing.
• Chief, Air Force NDI Program Office, AFRL/MLS-OL. DSN: 339-4322, Comm: 405-739-4322.
• ALC NDI Program Manager. Oklahoma City Air Logistics Center. DSN: 336-5008, Comm: 405-736-5008.
• ALC NDI Program Manager. Ogden Air Logistics Center. DSN: 586-4496, Comm: 801-586-4496.
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T.O. 33B-1-2
• ALC NDI Program Manager. Warner Robbins Air Logistics Center. DSN: 468-4489, Comm: 912-926-4489.
• NDI Field Program Manager. Air Force NDI Program Office, AFRL/MLS-OL. DSN: 339-3768, Comm: 405-739-3768.
• Technical Content Manager 33B series Technical Orders. Air Force NDI Program Office, AFRL/MLS-OL. DSN: 884-1880, Comm: 405-734-1880.
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SECTION II PROCESS CONTROLS
1.2 PROCESS CONTROLS.
NOTE
Specific process controls are discussed in section two of Chapter 2 through Chapter 6 of this manual.
1.2.1 Reason for Controlling the Process. Process control is an essential ingredient in achieving consistent and reliableresults with NDI inspections. A well regimented NDI process control program will not allow conditions to develop thatrender inspection methods as a source of misinformation. This misinformation may take two forms: 1) When NDI determinesa part is defective, when in truth it is not, resulting in a false call. This is a waste of resources and an unnecessary reduction inmission capability. 2) Even more dangerous is determining a part to be serviceable when in fact it is defective resulting in amissed call. Both forms of misinformation can be minimized through the implementation of effective process control.
1.2.2 Scope of Process Control. All aspects of these categories are interrelated. They have to be tuned to each other toachieve valid inspection results. If any one of these requirements is altered, the final outcome of the inspection will change,regardless of the inspector’s proficiency.
1.2.2.1 Process control is a general term used to encompass the actions and documentation required by establisheddirectives and logic. These controls are necessary for an NDI method to be effective in detecting conditions of interest (e.g.,cracks, foreign objects, corrosion, alignment of parts, and thickness of parts).
1.2.2.2 Areas that fall within the scope of process control are as follows:
• Training and the demonstrated practical skills of inspectors.• Inspection environment. (e.g., temperature, specific type and levels of light, safety, and human engineering.)• Material control. (e.g., serviceability of ultrasonic transducers, eddy current probes, penetrant materials, X-ray film and
chemicals, and magnetic particle suspensions.)• Equipment control. (e.g., operational and performance capability or Test Measurement Diagnostic Equipment
(TMDE)/user calibration.)• Written inspection instructions. (e.g., adequate, -9, -26, and -36 technical orders and Time Compliance Technical Orders
(TCTOs).)• Adherence to written inspection instructions. (e.g., distinguishing requirements dictated by specific NDI procedures
Radiography Inspection Interval ParaSafelight Fog Evaluation Initial install and requirements described 6.1
in indicated paragraphs
Interlock Functional Check Prior to X-ray operation 6.1.6
Interlock System Inspection 180 Days 6.1.6
Safe Light Filter Check Monthly 6.1.5
Fixer Control Monthly 6.1.4
Development Process Weekly 6.1.3
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CHAPTER 2FLUORESCENT LIQUID PENETRANT INSPECTION
SECTION I FLUORESCENT LIQUID PENETRANT INSPECTION GENERALPROCEDURE
2.1 FLUORESCENT LIQUID PENETRANT INSPECTION GENERAL PROCEDURE.
Fluorescent penetrant inspection is an effective method for detecting surface breaking discontinuities in metallic parts. It canprovide excellent detection sensitivity; however, the effectiveness of the method is highly dependent on strict control of theprocess. Penetrant material SHALL be listed on QPL SAE AMS 2644 and process control requirements must be followed.Black lights SHALL be capable of producing ultraviolet light intensity of at least 1000 micro-watt per square centimeter andSHALL NOT emit more than 2 ft-candles of white light. Ultraviolet and white-light measurements SHALL be measured 15inches from the lens. Ambient light conditions SHALL be as low as possible when performing inspections under black lightillumination. The ambient light SHALL NOT exceed 2 ft-candles in an inspection booth. Test part surfaces SHALL be freeof coatings and contaminants. Inspectors SHALL meet the training and certification requirements stated in paragraph 1.2 ofT.O. 33B-1-1.
Table 2-1. Fluorescent Penetrant Advantages and Limitations
Advantages Disadvantages/Limitations♦ Capable of complete coverage of complex ♦ Flaw opening must be open at the surface of test part
shapes
♦ Capable of detecting small surface discontinu- ♦ Surface condition must be relatively smooth and free ofities coatings and contaminants
♦ Is effective on ferrous and nonferrous metals ♦ Effectiveness is highly dependent on process control andand a variety of other materials cleanliness of inspection surface
♦ Inexpensive and requires less training than ♦ Surface coating removal procedures affect process sensi-other methods tivity (when possible coating removal SHOULD be lim-
ited to chemical stripping processes)
♦ Readily adaptable to large volume processing ♦ Cannot perform inspections with part temperature below40°F or above 125°F
2.1.1 Preparation of Part.
WARNING
• Due to the oily nature of most penetrants, they SHALL NOT be used on parts, such as assemblies, where theycannot be completely removed and will subsequently be exposed to gaseous or liquid oxygen. Oils, evenresidual quantities, may explode or burn very rapidly in the presence of oxygen. Only materials specificallyapproved for this application SHALL be used if penetrant inspection is required and complete removal of theresidue is not possible. The applicable Weapons System Technical Order and/or the responsible ALC NDIManager SHALL direct use of these materials.
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• Some penetrant materials may contain sulfur and/or halogen compounds (chlorides, fluorides, bromides, andiodides). These compounds may cause embrittlement or cracking of austenitic stainless steels if notcompletely removed prior to heat-treating or other high temperature exposure. Entrapped halogen compoundsmay also cause corrosion of titanium alloys if not completely removed after the inspection is completed andthe part is subjected to elevated temperatures. The applicable Weapons System Technical Order and/or theresponsible ALC NDI Manager SHALL direct use of these materials.
• All relevant safety equipment and procedures directed by Chapter 2 Section VIII of TO 33B-1-1 and AFOSHStandard 91-501 are required in this inspection procedure and SHALL be adhered to.
Correct part preparation is vital to consistent and effective penetrant inspection results. Coating removal SHALL beaccomplished IAW applicable Technical Order procedures and performed by trained and certified personnel.
CAUTION
• Chlorinated hydrocarbon solvents such as trichloroethylene, trichloroethane, carbon tetrachloride, and Freon(including its use in aerosol spray cans) SHALL NOT be used on titanium.
• Penetrant equipment contacting titanium such as parts-holding baskets SHALL NOT be coated with cadmium,lead, silver, or zinc.
• Failure to comply with these cautions could have a detrimental effect to the structural capabilities of thecomponents being prepared.
NOTE
When accomplishing penetrant inspections, the preferred finish removal method is chemical. If the finish must beremoved by mechanical means, it is recommended an acid etch (0.0004 inch minimum removal) be performedprior to penetrant inspection. Trained and qualified personnel SHALL perform acid etching IAW the applicable -3 series Technical Orders. Some organizations may require acid etching; consult the applicable Weapons SystemTechnical Order and/or the responsible Weapons System SPO.
a. Have all surface coatings removed from the area to be inspected as required. Anodized coatings SHALL NOT bestripped from aluminum alloys. Refer to the applicable -23 series Technical Orders and the Structural Maintenance orCorrosion Control Shop for coating removal procedures.
b. Perform a final wipe down of the part with a clean lint free cloth or paper towel dampened with an approved cleaner.
2.1.2 Penetrant Application Procedure. Penetrant methods C and D are the most common processes used at Air ForceNDI laboratories and are covered in this procedure. Methods A and B penetrant procedures SHALL NOT be used unlessspecific approval and instruction is provided by the Weapon System SPO or the ALC NDI Manager. Minimum penetrantsensitivity levels are shown in Table 2-2. Most NDI Laboratories will use level 3 (High) sensitivity penetrant materials intheir stationary penetrant process. Level 3 penetrant is generally adequate for most applications unless otherwise specified bytechnical order or engineering directive. If background fluorescence is noticeably high, a decrease in sensitivity level may berequired. Titanium and some rotating engine parts require and ultra high-level penetrant sensitivity, small amounts of variouspenetrants may need to be purchased to meet the requirements of all test part materials. Various sensitivity level penetrantscan easily be purchased in small quantities from any reliable NDI product distributor. Contact the appropriate ALC NDIManager for assistance.
Table 2-2. Material and Minimum Penetrant Sensitivity Level
Materials Penetrant Sensitivity LevelNonaircraft Rough Cast or Weld 2 (Medium or Normal)
Magnesium and Aluminum 3 (High)
Steels and Nickel Alloys 3 (High)
Titanium and some rotating engine parts 4 (Ultra High)
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a. Apply the penetrant to the inspection area by brushing, swabbing or spraying (method C) or brushing, swabbing,dipping, flowing or spraying (method D). Reapply penetrant as necessary to prevent the penetrant from drying duringthe dwell.
b. Allow penetrant to dwell for the minimum time defined in (see Table 2-3). The drain dwell mode is the preferredmethod of penetrant dwell; the immersion dwell mode is used as directed by a specific inspection instruction.
Table 2-3. Penetrant Dwell Times
Temperature 40 – 60°F MinimumService Induced Fatigue Cracks 60 minutes
Stress Corrosion Cracks 240 minutes
Temperature 60 – 125°F MinimumService Induced Fatigue Cracks 30 Minutes
Stress Corrosion Cracks 240 Minutes
2.1.3 Penetrant Removal Procedure. During the penetrant removal process, it is important to remove all the surfacepenetrant without removing penetrant contained in defects.
2.1.3.1 Method C (Solvent Wipe) Penetrant Removal.
CAUTION
The solvent-remover SHALL NOT be applied directly onto the inspection surface to remove excess penetrant.
a. Following the penetrant dwell period, the surface is wiped with a clean, dry lint-free cloth or towel to remove themajor portion of surface penetrant. The proper procedure is to make a single pass and then fold the cloth or towelover to provide a clean cloth surface for each wipe.
b. When the surface penetrant has been reduced to a minimum, remove any remaining residual penetrant using a cleanlint-free cloth or towel lightly moistened with an approved solvent remover. The amount of solvent applied to thecloth is critical. The cloth is only lightly moistened with the application of a fine spray of solvent. The cloth SHALLNOT be saturated by pouring, immersion, or excessive spraying.
c. A black light is used to examine the part surface during the intermediate and final wiping stages. The surface of therag should also be examined under black light during the final solvent wipe. If the rag shows more than a trace ofpenetrant, it is folded to expose a clean surface, remoistened with solvent, and again wiped across the part. This stepis repeated until the fluorescent background on the part is minimal and the rag shows little or no trace of penetrant.
d. After the solvent wipe, conduct a final wipe down with a clean dry cloth or towel to remove any residual solventremaining on the part surface.
2.1.3.2 Method D (Hydrophilic Remover) Penetrant Removal - Immersion.
CAUTION
The correct concentration of hydrophilic remover is critical to the Method D process. Consult the manufacturer’sguidelines for remover concentration criteria.
Penetrant removal for Method D immersion begins with a clean water rinse. Depending on the complexity of the test part, therinse should be between 30 and 120-seconds. Maintain a rinse angle of 45 to 70°, water temperature between 50 and 100°F,and water pressure below 40 psi.
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a. Following the pre-rinse, an immersion dwell in hydrophilic remover is used to remove the remaining surfacepenetrant. The remover is slightly agitated to allow fresh remover to be exposed to the part, this is usuallyaccomplished with low-pressure shop air at the bottom of the remover tank. Agitation can also be accomplished bygently stirring the test part in the remover. Dwell times will vary between 30 and 120-seconds. If a predetermineddwell time is not available for the in-use remover, start with a 30-second immersion dwell and then perform the rinse.If the background is unacceptable perform another 15-second immersion dwell then rinse and repeat the procedureuntil the part has acceptably low background fluorescence. Total remover immersion SHALL NOT exceed 120-seconds.
b. After the immersion dwell, rinse the remover and remaining surface penetrant from the part. Perform the rinse underblack light to the same criteria as the pre-rinse. Stop the rinse when background fluorescence is at a minimum. It isimportant to keep the immersion dwell and the water rinse to the lowest time possible and still obtain lowbackground fluorescence.
2.1.3.3 Method D (Hydrophilic Remover) Penetrant Removal – Spray.
CAUTION
The hydrophilic remover concentration SHALL NOT exceed 5-percent when using spray application
Penetrant removal for Method D spray begins with a clean water rinse. Depending on the complexity of the test part, the rinseshould be between 30 and 120-seconds. Maintain a rinse angle of 45 to 70°, water temperature between 50 and 100°F, andwater pressure below 40 psi.
a. Following the pre-rinse, use a garden sprayer to spray a 5-percent concentration of hydrophilic remover onto theinspection surface. Perform remover application under black light illumination to ensure optimum penetrant removal.Care must be taken not to over-remove the surface penetrant. Maximum remover spray time SHALL NOT exceed120 seconds. Use only the minimum spray time required to obtain low background fluorescence.
b. A final water-only spray is used to remove the hydrophilic remover from the surface. Depending on the complexityof the test part, the rinse should be between 30 and 120-seconds. Maintain a rinse angle of 45 to 70°, watertemperature between 50 and 100°F, and water pressure below 40 psi.
2.1.4 Developer Application and Drying Procedure. Developers are used to draw penetrant from discontinuities andspread it out over adjacent part surfaces increasing the visibility of the indication. Developers also provide a contrastingbackground for the penetrant material.
2.1.4.1 Dry Developer (Form a) Application.
WARNING
Dry developer particles are not toxic materials; however, inhalation should be avoided. Air cleaners, facemasks,or respirators may be required. The Base Bioenvironmental Engineer SHALL be consulted if the processgenerates airborne particles.
NOTE
• Dry developers SHALL NOT be used unless specifically approved by the applicable Weapons SystemTechnical Order and/or the responsible ALC NDI Manager.
• Dry developers SHALL NOT be applied to a part until the surface is thoroughly free of moisture. Thepresence of even a little moisture will interfere with the developer action and small flaws may be missed.
a. Dry the test part completely before applying dry developer.
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b. Dry developer is applied by blowing with a bulb type blower, immersing in a container, pouring the powder over thepart, use of a dust or fog chamber, or an electrostatic system.
c. Shake or carefully blow off (with bulb type blower) the excess developer, if using compressed air it SHALL bebelow 5-psig. For small areas, a bulb type blower is recommended.
d. Allow developer to dwell using the dwell times in (Table 2-4).
2.1.4.2 Water-soluble (Form b) Developer Application:. Water-soluble developer is the most commonly used devel-oper at Air Force NDI laboratories. It is the recommended developer for method D penetrants because it provides a betterbackground than dry or water suspended developers and does not require agitation.
a. Apply water-soluble developer by dipping or flowing. Allow the part to drain and rotate to prevent developerpooling.
b. Place the test part into a clean dryer oven with a temperature of 140°F or less. (Depots with automatic or semi-automatic systems SHOULD refer to the process order for the system or test part to set drying oven temperature.)Rotate the part as required to prevent developer pooling.
c. Remove the test part from the drying oven as soon as the part is completely dry.
d. Allow the developer to dwell. Dwell time begins when the test part is completely dry. (Refer to Table 2-4 fordeveloper dwell times.)
2.1.4.3 Water-Suspended (Form c) Developer Application:. Water-suspended developers are applied in the samemanner as water-soluble with one exception; suspended developers require thorough agitation prior to application to the testpart. Refer to paragraph 2.1.4.2 for procedures.
2.1.4.4 Nonaqueous (Form d) Developer Application:. Nonaqueous solvent-suspended developers are generallypackaged in aerosol spray cans. It is most often used in portable inspections but is also used in the bleed-back procedures formethods C and D. It provides an excellent background and is the most sensitive developer form.
NOTE
Nonaqueous developers SHALL NOT be applied to a part until the surface is thoroughly free of moisture. Thepresence of even a little moisture will interfere with the developer action and small flaws may be missed.
a. Ensure the test part is completely dry before applying nonaqueous developer.
b. Shake spray can thoroughly before use.
c. Spray a light even coat of developer over the inspection area.
d. Allow the developer to dwell. (Refer to Table 2-4 for developer dwell times.)
e. Inspect the test part after sufficient dwell.
NOTE
Test parts SHOULD NOT be exposed to high intensity black light during the developer dwell. Long exposure toblack light will cause penetrant indications to fade.
Table 2-4. Developer Dwell Times
Temperature 40 – 60°FNonaqueous Developer (Spray Cans) Minimum Maximum
Service Induced Fatigue Cracks 20 minutes 60 minutes
Stress-Corrosion Cracks 60 minutes 120 minutes
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Table 2-4. Developer Dwell Times - Continued
Temperature 40 – 60°FNonaqueous Developer (Spray Cans) Minimum Maximum
Aqueous Developer (Water Soluble andSuspendable) Minimum Maximum
Service Induced Fatigue Cracks 30 minutes 120 minutes
Stress-Corrosion Cracks 60 minutes 120 minutes
Dry Developer Minimum Maximum
Service Induced Fatigue Cracks 30 minutes 240 minutes
Stress-Corrosion Cracks 60 minutes 240 minutes
Temperature 60 – 125°FNonaqueous Developer (Spray Cans) Minimum Maximum
Service Induced Fatigue Cracks 10 minutes 30 minutes
Stress-Corrosion Cracks 30 minutes 60 minutes
Aqueous Developer (Water Soluble andSuspendable) Minimum Maximum
Service Induced Fatigue Cracks 15 minutes 60 minutes
Stress-Corrosion Cracks 30 minutes 120 minutes
Dry Developer Minimum Maximum
Service Induced Fatigue Cracks 15 minutes 120 minutes
Stress-Corrosion Cracks 30 minutes 240 minutes
2.1.5 Fluorescent Penetrant Interpretation. Fluorescent penetrant interpretation is done under blacklight illumination inan inspection booth or darkened area. Portable inspections may require a locally manufactured or purchased tent-likeapparatus made of dark cloth or canvas to reduce ambient light levels and enhance inspection sensitivity. Identify indicationsas linear or rounded and measure the largest dimension of the indication for comparison to acceptance criteria. A roundedindication has length that is less than 3 times its width. A linear indication has a length 3 or more times its width. Evaluateindications according to limits in technical data. If technical data is not specific or no technical data is available, consider alllinear indications relevant and rounded indications 1/16th of an inch or larger relevant for both aircraft and nonaircraft testparts.
2.1.5.1 Defects will generally be linear or aligned rounded or pinpoint indications resulting from:
2.1.5.2 Non-relevant indications will not be marked. These indications can be identified by using the bleed-back method(see paragraph 2.1.6). Non-relevant indications are generally:
2.1.5.3 Defects should be marked on the part surface with an approved marking pencil. Measure the defect and noteidentifying characteristics. Describe the defect in detail including its size (length), location, and orientation. Documentinspection findings IAW Air Force Instructions and local directives. An example of a good defect description is as follows:‘‘Method C penetrant inspection of welds on transfer case part number 128-6380. Crack noted and marked on the inlet tocase weld. The indication is sharp, well defined, bright, and linear. The defect is 2.125 inches long and runs down the centerof the weld crown.’’
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NOTE
Air Force NDI personnel SHALL NOT make serviceability determinations except as described in AFI 21-101(field units only). The role of the NDI inspector is normally limited to providing a detailed description of thedefect and its location. Disposition and repair responsibility for a flawed part or airframe lies with StructuralMaintenance personnel or the owning workcenter and the appropriate engineering authority.
2.1.6 Bleed-Back Method. The bleed-back method is used to evaluate discontinuities for relevance. Non-relevantindications such as scratches, nicks, and tool marks will generally not hold enough penetrant to redevelop indications afterthe initial indications have been removed. The following is a typical bleed-back procedure:
a. Use a clean dry cloth or paper towel to wipe the indication area.
b. Lightly dampen the corner of a clean cloth or cotton swab with an approved solvent remover. Carefully wipe theindication area once with the solvent dampened cloth or cotton swab. After the solvent has evaporated, examine thebare surface under black light illumination for evidence of the indication as it begins and continues to developwithout developer applied. Use of a 5-10X magnifier is recommended. If redevelopment of the indication occurs, it isbe considered a relevant indication.
c. If no indication is observed apply a light coat of nonaqueous (form d) developer.
d. Again, after the developer solvent has evaporated, carefully examine the surface under black light illumination forevidence of the indication as it begins and continues to develop with developer applied. Use of a 5-10X magnifier isrecommended. Allow a minimum redevelop time as defined in Table 2-4. If redevelopment of the indication occurs,it is considered a relevant indication. Non-relevant indication should not demonstrate any redevelopment.
2.1.7 Post Cleaning. Penetrant and developer residues SHALL be completely removed prior to reapplication of thesurface finish. Dry developers, as well as water soluble and suspendable developers, are removed easily with a warm waterrinse. Penetrants used in these processes are removed with warm water and an approved mild detergent. A soft bristled bushis effective for recessed areas, and around fasteners and other obstacles. When performing portable inspection, penetrant anddeveloper residues are removed by first wiping with a clean dry cloth or paper towel then wiping again with a cloth or papertowel dampened with an approved solvent.
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SECTION II FLUORESCENT LIQUID PENETRANT INSPECTION PROCESSCONTROL
2.2 SYSTEM PERFORMANCE TEST PROCEDURE - CRACKED-CHROME PANELS.
CAUTION
Use care in handling and storing the panels. Do not drop, hit, or place mechanical stress on the test panels. Do notattempt to bend or straighten the test panels. Do not expose the test panels to temperatures above 212°F (100°C).Thorough ultrasonic cleaning of cracked-chrome panels after each use is mandatory. The panels are easilydamaged by rough handling or when dropped. Damaged or degraded panels SHALL be immediately replaced.
The cracked-chrome panels are used to evaluate the liquid penetrant system’s performance. They provide a side-by-sidecomparison of in-use liquid penetrant materials with a reference standard of the same material that was set aside prior to thematerial being put into service. The cracked-chrome panels readily show small or gradual changes in penetrant materialsensitivity. Tests made with cracked-chrome panels do not provide useful information on background fluorescence caused bysurface roughness or the ability of a liquid penetrant to reveal small cracks in the presence of severe background fluorescencecaused by surface roughness or porosity.
2.2.1 Equipment and Materials Required for Cracked-Chrome Panel Test. Equipment and materials needed toperform the cracked-chrome panel test are listed below:
• In-use penetrant, remover, and developer.• Reference penetrant, remover, and developer.• Small glass or paper containers.• 2 each acid brushes or swabs.• 2 each cracked chrome panels. (Cracked-chrome panels are delivered from the manufacturer in sets of two. These panels
SHALL be used together and not substituted with any other panels. When one panel is damaged or degraded the wholeset SHALL be replaced.)
• Hydrophilic fluorescent liquid penetrant line and associated equipment. (The cracked-chrome panel may also beperformed with method A, B, and C penetrant material.) (See paragraph 2.2.6 thru paragraph 2.2.8)
2.2.2 Procedure for Cracked-Chrome Panel Test.
a. Wipe the cracked-chrome panels with a clean lint free cloth dampened with solvent. Allow to dry and examine underultra violet light. If residual penetrant is present, clean the panels in accordance with (see paragraph 2.11).
b. Pour a small quantity of working bath material and reference material in separate glass or paper containers. To avoidcontaminating the entire reference sample, the reference material SHALL NOT be applied to the cracked-chromepanel directly from its storage container.
c. Apply penetrant by brushing, swabbing, or flowing. Brushing or swabbing is preferred since it permits better controlover the quantity of penetrant applied. Use the working materials on one panel and the reference materials on theother. Use separate brushes or swabs for the working material and the reference. Allow the penetrant to dwell for 5-minutes.
d. Perform a pre-rinse of 20-seconds or less. Allow just enough time to remove the surface penetrant. (Coarse spray ofplain water at no more than 40 psi with a water temperature between 50 and 100°F)
e. Apply remover by immersing the panels in their correlating working bath and reference material. Removal time willbe very short, between 10- to 20-seconds.
f. Perform a final rinse of 20-seconds or less. (Coarse spray of plain water at no more than 40 psi with a watertemperature between 50 and 100°F)
g. Apply correlating working bath and reference developer by immersion, flowing, or spraying. (Ensure water-suspended developers are mixed well before applying.)
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h. Place in clean drying oven. Do not allow to sit in the dryer for an extended period, remove as soon as the panels aredry.
i. Allow developer to dwell for 5-minutes. The dwell begins after the panels are completely free of moisture.
j. Examine the panels side-by-side under black light, first noting the overall brightness and color of the indications.Second, examine each in detail by following individual indications across both panels. Note the presence, absence, ordiminishing of crack indications on the working bath panel as compared to the reference sample panel and observethe difference in continuity, size and color. Any distinct difference SHALL be cause for additional testing todetermine if the penetrant, remover, or the developer caused the difference in the indications.
2.2.3 Testing for Failed Penetrant. If the system performance test indicates a loss of sensitivity or brightness, use a setof clean, dry cracked-chrome panels to repeat the material test procedure (see paragraph 2.2.2) with the following changes:use the reference samples of remover and developer on both panels. If crack indications on the two panels show clearlyvisible differences in sensitivity, brightness or color, the penetrant SHALL be replaced.
2.2.4 Testing for Failed Emulsifier/Remover. If there is little or no difference in the crack indications during thepenetrant performance test, clean the panels and repeat the performance test procedure to test the emulsifier/remover. Usereference penetrant on both panels and apply the working sample of remover to one specimen and reference remover to theother panel at the appropriate point in the process. Apply reference developer to both panels. If crack indications on the twopanels show clearly visible differences in sensitivity, brightness or color, the remover SHALL be replaced.
2.2.5 Testing for Failed Developer. If there is little or no difference in the crack indications during the removerperformance test, clean the panels and repeat the performance test procedure to test the developer. Use reference penetrantand remover on both panels and apply the working developer to one panel and the reference developer to the other panel atthe appropriate point in the process. If crack indications on the two panels show clearly visible differences in sensitivity,brightness or color, the developer SHALL be replaced.
2.2.6 Lipophilic Penetrant Systems. The removal step is the only difference in performing the cracked-chrome paneltest on a lipophilic process. Simply skip step d in the procedure and modify step e so that the panels are immersed inemulsifier and immediately removed. Allow the emulsifier to dwell for 10 to 20 seconds and proceed to step f.
2.2.7 Water Washable Penetrant Systems. For water washable systems the remover and developer steps need to bemodified. Skip steps d and e, proceed to step f. Wash the panels as long as necessary to remove all visible penetrant. Do notover wash, the cracks on these panels are shallow and the trapped penetrant can be easily removed by over washing. Sinceaqueous developer cannot be used with water washable penetrants, a nonaqueous or a dry power developer must be used. Drythe panels in the drying oven and then spray a light even coat of nonaqueous developer on the panels or dip the panels in drypowder developer. Proceed to step i and finish the procedure.
2.2.8 Solvent Removable Penetrant Systems. Solvent removable penetrant systems (spray cans) do not require a 7-day system performance test because the materials are not subject to reuse or degradation. The cracked chrome panel test isrequired before a new batch of material is put into to service. The material previously used becomes the reference so it isimportant to test the new material before the old material is completely used up. The remover and developer steps need to bemodified; skip steps d, e, and f. The removal step is to wipe the panels with a separate clean dry cloth and then performanother wipe with a separate solvent dampened cloth, repeat the solvent wipe until no penetrant is visible. The developerapplication step is to spray a light even coat of nonaqueous developer on the panels. Proceed to step i and finish theprocedure.
2.3 SYSTEM PERFORMANCE TEST WITH THE PSM STARBURST PANEL (DEPOT ONLY).
The system performance test utilizing the PSM panel is a daily check of the entire penetrant system. The panel’s polishedhalf contains five star shaped cracks and is used to monitor changes in penetrant sensitivity, while the grit blasted half is usedto test the removal process of the penetrant system. The PSM panel test is ideally suited for high volume workloads becauseit can be processed directly in the working material along with the first batch of parts at the beginning of the workday.Because the panel is used strictly with in-use penetrant materials, no reference standards are needed. Facilities with automaticor semi-automatic penetrant systems that do not use traditional working bath tanks SHALL use the PSM panel solely as theirsystem performance test. Laboratories with traditional penetrant lines SHALL use the Cracked-Chrome Panel Test as theirsystem performance test but MAY use the PSM panel as an optional test.
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2.3.1 Procedure for Performing the PSM Starburst Panel Test.
NOTE
Facilities using automatic or semi-automatic systems SHALL process the PSM panel as they would a routine testpart. Times, temperatures, water and air pressures will vary accordingly. Consult the ALC NDI manger forspecific guidance.
a. Dip, brush, or spray the PSM panel with in-use penetrant. Use the same criteria as a test part with suspected fatiguecracks. Test at room temperature. (30-minute dwell time)
b. Pre-rinse the PSM panel. (Coarse spray of plain water at no more than 40 psi for 30- to 120-seconds with a watertemperature between 50 and 100°F)
c. Immerse or spray PSM panel in remover. Use the same remover time as used to process a normal part. (30 to 120seconds)
d. Perform the final rinse. (Same criteria as in step b)
e. Dip the PSM panel in developer. (If water suspended developer is used ensure the solution is mixed well beforedipping the panel.)
f. Place the PSM panel in the dryer oven and remove immediately once the panel is dry. (Dryer oven should bepreheated to 140°F or less; facilities using automatic or semiautomatic systems refer to the process order for dryeroven temperature.)
g. Let the panel dwell for 15-minutes.
h. Inspect and evaluate indications on the PSM panel.
2.3.2 Response of PSM Panels. PSM Panels are manufactured to provide a minimum number of indications for eachpenetrant sensitivity level. The panels SHALL show, as a minimum, the number of indications permitted during calibrationand listed as follows:
Minimum Number of Indications:
Sensitivity Level Number of Indications
Level 1 and 2 3 Indications
Level 3 4 Indications
Level 4 5 Indications
2.3.3 Reading PSM Starburst Indications. Examine the panel for the number of starburst indications as well as thebrightness of the indications. The PSM panel test is a flaw indication quality comparison from one test to another and theinspector must be able to observe a difference in the panel’s appearance. An increased background fluorescence, decrease inthe number of flaw indications, decrease in flaw indication definition, or decreases in brightness are all indicators of apenetrant process problem. For example if the developer is malfunctioning, crack centers may still be seen, but may not be asbright as normal. When using aqueous developers, the developer SHALL provide a uniform coating over the chrome surface.Failure of the aqueous developer to wet the chrome may mean the solution strength is low, or the wetting agent has degraded.Washability and background fluorescence must also be interpreted. The grit blasted side of the PSM panel is used for thispurpose. High and ultra-high sensitivity systems leave a fluorescent background on the panel’s grit blasted area. Othersystems may leave no background. Neither condition is alarming unless it represents a change from the normal systemperformance. Higher than normal background may indicate low remover concentration, short remover dwell time, or anineffective pre-wash. Lower than normal background may indicate high remover concentration, excessive remover dwelltime, or inadequate developer application. If a performance problem is noted, additional testing is required to determine thecause. For laboratories using a traditional hydrophilic penetrant line refer to (see paragraph 2.2.2) and perform the crackedchrome panel test to systematically eliminate each possible cause until the problem area is identified. For laboratories usingsemi-automatic are automatic systems each section of the system needs to be inspected to determine if the preset parametersare correct and all equipment is functioning normally.
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Ing. Omar Fabian
Resaltado
T.O. 33B-1-2
2.3.4 Cleaning PSM Panels. PSM Panels SHALL be thoroughly cleaned immediately after use in accordance with (seeparagraph 2.11). In addition, PSM panels SHALL be wiped with a clean, lint free, solvent dampened cloth and examinedunder ultra-violet light for residual penetrant prior to use. If residual penetrant is present, perform a thorough cleaning again.
NOTE
PSM panel indications will degrade with handling and repeated use. Gradual changes in indication appearanceare not readily noticed. Careful handling and thorough ultrasonic cleaning is mandatory.
2.4 INSPECTION BOOTH CHECKS.
NOTE
Inspection booth checks do not require documentation unless specifically stated else where in this TechnicalOrder or other directives. The frequency of the checks are at the supervisor’s discretion unless otherwise directedby this Technical Order.
The inspection booth and process SHALL be checked to verify the following:
a. Verify the inspection booth is of adequate size for the parts to be inspected.
b. Verify the booth is not used to store parts, consumables, or standards.
c. The inspection booth SHALL be cleaned frequently and background fluorescence from spilled penetrant kept to aminimum.
d. Black light bulbs and filters SHALL be kept clean and ambient light levels checked when filters or bulbs arereplaced.
e. Check black light intensity and document at least once each day or prior to use.
f. Inspect filters for fit and excessive dirt, developer, cracks, and chips.
g. Position black lights so they do not shine into the technician’s eyes.
2.5 SURFACE WETTING TEST.
a. Apply a small amount of penetrant with a cotton swab to the clean, shiny surface of commercially availablealuminum foil.
b. Allow penetrant to dwell for 10-minutes.
c. The penetrant should wet the surface and not retract or form beads.
2.6 PENETRANT BRIGHTNESS TEST - (DEPOT ONLY).
Perform this test on all Type I fluorescent penetrants as follows:
a. Pour 10 milliliters of IN-USE penetrant into a graduated cylinder. Allow the penetrant to drain down the insidecylinder walls. Add or remove penetrant as required to achieve exactly 10-milliliters. Clean the outside of thecylinder.
b. Fill the graduated cylinder to the 100 ml level with an acetone (Specification 0-A-51F). Stopper the cylinder andslowly invert the graduated cylinder several times to mix the contents. Do not shake or agitate the cylindervigorously.
c. Using tweezers, insert a quartered piece of filter paper into the cylinder mixture, withdraw the paper and set it asideto air dry for a minimum of 5-minutes.
d. Discard the contents of the graduated cylinder and clean the cylinder with an approved solvent (Specification O-C-265 or equal). Dry with clean filtered compressed air.
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e. Pour 10 ml of REFERENCE SAMPLE penetrant into the graduated cylinder. Allow the penetrant to drain down theinside cylinder walls. Add or remove penetrant as required to achieve exactly 10 ml. Clean the outside of thecylinder.
f. Fill the graduated cylinder to the 100 ml level with acetone. Stopper and slowly invert the graduated cylinder severaltimes to mix the contents. Do not shake or agitate the cylinder vigorously.
g. Using tweezers, insert a quartered piece of filter paper into the cylinder mixture, withdraw the paper and set it asideto air dry for a minimum time of 5-minutes.
h. When both filter papers (in-use and reference) are dry, compare the fluorescent brightness of the filter papers to eachother under black light. If a noticeable difference of fluorescent brightness is noted, the fluorescent properties of thein-use production line penetrant have deteriorated and the fluorescent sensitivity will probably not be acceptable.Follow accepted activity standards to process and perform additional testing or to discard the contaminated/degradedmaterial.
i. At the conclusion of the fluorescent brightness testing, rinse the cylinder with water, and clean with acetone. Drywith clean filtered compressed air.
2.6.1 Penetrant Rapid Brightness Test (FIELD LABS). A rough check of penetrant baths can be accomplished bycomparing their appearance on an absorbent material, preferably filter paper. Perform this test on all Type I fluorescentpenetrants as follows:
a. Place a drop of the working bath penetrant on the absorbent material, preferably the filter paper.
b. Place a second drop of penetrant from the reference standard on the same absorbent material near the drop from theworking bath.
c. When the two drops merge, examine under a black light for difference in color and brightness. If significantdifference in color and brightness is noted additional testing is required. (See paragraph 2.2.3)
2.7 TESTING CONCENTRATION OF WATER BASED (METHOD ‘‘A’’) PENETRANTS.
There is a small number of approved Method ‘‘A’’ penetrants currently containing water as a major component. The fewapproved water washable penetrants are formulated to provide a similar sensitivity performance as Method ‘‘B’’ or ‘‘D’’penetrants. Some savings may be realized in disposal cost of the more environmentally friendly penetrants. It should be notedthat any penetrant that has been in-use SHOULD be tested for contaminants prior to disposal. It is not unusual for hazardousmaterial, mainly heavy metals to build up in in-use penetrants from test parts and lubricants. Because water is a mainconstituent and evaporation losses may affect the penetrant performance, a periodic water concentration check is required.The refractometer method described in (see paragraph 2.9) SHALL be used to check concentration of water-based penetrantsin the absence of specific manufacturer procedures. If the manufacturer provides specific water concentration test proceduresthe manufacturer’s procedures SHALL take precedent.
2.8 TESTING LIPOPHILIC EMULSIFIER (METHOD ‘‘B’’).
Penetrant is an unavoidable contaminant of lipophilic emulsifier. It is carried into the emulsifier on the surface of parts whereit dissolves and is washed off during immersion and drain process. Since emulsifier and penetrant are capable of being mixedin all concentrations, even small quantities of fluorescent dye will cause the emulsifier to fluoresce. The fluorescentbrightness increases with increasing dye content, but it is impossible to visually estimate penetrant contamination byobservation of the tank surface. Emulsifier will continue to function when contaminated with penetrant; however, when thepenetrant concentration reaches a certain level the emulsification action slows and eventually stops. The penetrant materialspecification (SAE-AMS-2644) requires a 4-to-1 mixture of emulsifier to penetrant to leave no more residual backgroundthan the uncontaminated emulsifier.
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2.8.1 Lipophilic Emulsifier Removability Test.
NOTE
The annealed type 301 or 302 stainless steel panel may be locally manufactured. It is a two-inch by four-inch, 16-gauge (0.060) panel. The panel SHALL be ultrasonically cleaned or vapor degreased and grit blasted on bothsides using 100 mesh, aluminum oxide grit (not beads), using 60 psig air pressure, with the gun heldapproximately 18- inches from the panel surface. After blasting, the panel SHALL be ultrasonically cleaned inacetone or other suitable solvent. Ensure the panel is dry and free of residues after cleaning. Handle the panel bythe edges and protect it from contamination by wrapping in tissue paper.
Locally manufacture a simple stand large enough to hold the panel and maintain a 60° (±15°) angle. The stand will preventpooling during dwell.
2.8.1.1 The removability test requires using the annealed type 301 or 302 stainless steel panel. In-use lipophilic emulsifiersSHALL be periodically tested for contamination in accordance with (see Table 1-1). The process for performing theremovability test is as follows:
a. Immerse the panel in the working penetrant bath and allow it to drain for 10- minutes at approximately a 60° (±15°)angle.
b. After the 10-minute dwell, apply working bath emulsifier to one-half of the panel and reference standard emulsifierto the other half. Immersion is the preferred method of application because it is better controlled. Pouring may bedone but care must be taken to not mix or overlap the two emulsifiers.
c. Allow emulsifier to dwell for 2-minutes then wash for 60-seconds. Maintain an even distance and angle whenspraying the panel. Examine the panel for signs of fluorescent background after the rinse.
d. Apply developer and place in a clean dryer oven. Remove the panel as soon as it is dry.
e. Allow developer to dwell for 5-minutes.
f. Evaluate the panel under black light. A distinct difference in residual background indicates excess penetrantcontamination of the working bath lipophilic emulsifier. Should the emulsifier fail the contamination test, it SHALLbe replaced with fresh material.
NOTE
A portion of in-use emulsifier (25 to 50 percent) MAY be extracted from the tank and replaced with freshemulsifier. This procedure can be accomplished only one time in the service life of the emulsifier. A completechange out of the emulsifier is required once penetrant contamination again reaches unacceptable levels. Acontamination check SHALL be performed after a partial change out of emulsifier.
2.9 HYDROPHILIC REMOVER REFRACTOMETER TEST.
The refractometer test is the preferred method for measuring the concentration of hydrophilic remover baths. The test isperformed as follows:
a. Dip the plastic rod supplied with the refractometer into the in-use hydrophilic remover.
b. Raise the cover plate on the refractometer and place two or three drops of the test solution on the prism face. Closethe cover plate; making certain the test solution film completely covers the prism face.
c. Hold the refractometer close to a bright light source so light enters and illuminates the prism. Look through theeyepiece of the refractometer and read the Brix value (refractive index units) where the bright and dark areas meet.Adjust the position between the light source and the prism face to create a clearer meeting line.
d. Record the refractive index units as indicated. Using the manufacturer’s literature, determine the concentration of thetest sample from the refractive index value. Compare this value with the graph you created when mixing the bath.The working bath solution SHALL be within 5-percent of the required concentration. Adjustments are made byeither adding water or concentrate remover to bring the remover bath concentration to an acceptable level.
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e. When the test has been completed, clean the refractometer cover plate and prism face with a soft lint-free cloth.
2.9.1 Hydrophilic Remover Hydrometer Test. A hydrometer may be used if recommended by the manufacturer of thehydrophilic remover. The hydrometer test involves the use of a hydrometer to determine the concentration of a solution byspecific gravity. This method is very similar to the method used to check water-soluble and water-suspendable developers.When using the hydrometer, perform a water concentration test in accordance with the following procedure:
a. Mix a reference sample of new hydrophilic remover as recommended by the manufacturer in a 500 ml graduatedcylinder or similar container.
b. Using the hydrometer, check the concentration of the reference sample by noting its specific gravity and recordingthis reading.
c. Place the hydrometer in the working bath; read and record the test results. Compare the results of the referencestandard and the in-use remover. The in-use remover is adjusted to achieve a concentration within 5-percent of thereference standard test results.
2.9.2 Hydrophilic Remover Quick Test for Penetrant Contamination. The quick test will determine if penetrant ispresent in the remover in large enough quantities to become a possible contaminant. Perform this test by passing a black lightover the surface of the remover in the tank and visually examining it for signs of fluorescence. Penetrant is removed byskimming or absorbing the penetrant with a paper towel.
2.9.3 Hydrophilic Remover Performance Check.
NOTE
The immersion removal time cited in the following procedure is typical. Time will depend upon type ofpenetrant, type of remover, agitation, and remover concentration. The time SHALL be determined at each depotor field laboratory for each system involved. Trials SHALL be accomplished using fresh or uncontaminatedremover. The objective is to use the minimum time necessary to produce a background-free surface on theimmersion panel when the remover is uncontaminated.
A performance check will verify the concentration or contamination of used immersion hydrophilic remover baths. Residualpenetrant from parts disperse in the remover, can cause problems when performing a color comparison check and skew therefractive index when performing the refractometer test. Performance testing will usually indicate a problem with theremover bath (e.g., penetrant contamination, unacceptable concentration) well before a refractometer measurement willindicate a problem. The performance test involves processing the two annealed type 301 or 302 stainless steel panels withdifferent removal contact times and comparing the results using the following procedure:
a. Immerse the panels in the working penetrant bath and allow it to drain for 10- minutes at proximately a 60° (±15°)angle.
b. Process the first panel through a 10-second pre-rinse, 10-second drain, 20-second immersion in remover, 5-seconddrain, and 10-second rinse.
c. Process the second panel through the same cycle except double the immersion time to 40-seconds in the remover.Examine both panels under black light. When the remover is fresh and uncontaminated, neither panel should exhibitany background fluorescence. As the penetrant level in the remover starts to build up, the short immersion time panelwill begin to show some residual fluorescence while the longer immersion panel remains free of background. As theamount of penetrant in the remover continues to increase, the level of fluorescence on the short immersion panelstabilizes and the longer immersion panel begins to show some residual background. When the remover reaches itspenetrant tolerance limit, there will be negligible difference in fluorescence background on the two panels. Theremover SHALL be changed at this point.
d. Clean the panels by ultrasonically cleaning in acetone or other suitable solvent. Refer to (see paragraph 2.11) formore information on cleaning process control panels.
2.9.4 Hydrophilic Remover Background Fluorescence Check. If the performance check does not indicate removerdegradation, using the same panels, determine if penetrant is causing the background fluorescence by proceeding as follows:
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a. Immerse the panels in the working penetrant bath and allow it to drain for 10- minutes at approximately a 60° (±15°)angle.
b. Process the first panel using a 10-second pre-rinse, 10-second drain, 30-second immersion in the working bathremover, 5-second drain, and a 10-second rinse.
c. Process the second panel using the same procedures above, except this time use the reference remover.
d. Examine both panels under a black light.
e. If background fluorescence is present on both panels, the working bath penetrant is contaminated and SHALL bereplaced. If the panel processed with the reference remover is free of background fluorescence, and the other panelexhibits any background fluorescence, then the determination can be made that the working bath remover hasreached its penetrant tolerance limit and SHALL be replaced.
f. Ultrasonically clean the grit blasted panels using the cleaning process described in (see paragraph 2.11).
2.9.5 Hydrophilic Remover Spray Solution Test. Remover spray is normally used only once with the solution beingdisposed of after contact with the part. Contamination of the working solution is not a problem; however, the aspiratorinjection system requires frequent checks to ensure that the proper concentration is produced. Measure the concentration ofremover in the spray whenever the aspirator or water pressure valve is adjusted and at the intervals prescribed in (seeTable 1-1). A measurement is also taken whenever an unexplained change in background fluorescence occurs. Testhydrophilic spray remover as follows:
a. Check the hydrophilic remover touch-up spray concentration by one of the methods explained in (see paragraph 2.9and paragraph 2.9.1).
b. The concentration of the spray remover is much lower than immersion baths, and the results of the check will reflectthis change. Important items to remember are:
(1) If the hydrophilic remover touch-up spray is not of the same batch as used to generate the original concentrationversus refractive index graph, then a new graph needs to be plotted.
(2) Make sure the temperature of the touch-up remover is within the parameters of the instrument/graph being used orcompensated for.
2.9.5.1 The system concept for penetrant-material SHALL apply to the hydrophilic remover used in the touch-up step of thepenetrant inspection. The material being used in the immersion remover tank and the touch-up spray SHALL be of the samemanufacturer and qualified as a penetrant system listed in the qualified products list in accordance with QPL SAE AMS2644.
Prior to obtaining the hydrometer reading, fill the working solution to the proper working level (as previouslymeasured and marked), thoroughly agitate, and check the tank for caked particles on the bottom and in thecorners. Allow newly prepared solutions to set for 4-hours after mixing then agitate prior to testing. This agingperiod allows the developer particles to become wetted or saturated.
The reading from the hydrometer is compared to an accurate graph/conversion chart obtained from the supplier of thespecific developer. The process for performing a concentration test is as follows:
a. Place the hydrometer directly in the tank, ensuring it floats free, not touching the tank sides. The specific gravity isread from the scale on the hydrometer. It may be more convenient to take a sample from the tank using a long,narrow glass container such as a graduated cylinder, which is deep enough to float the hydrometer.
b. Compare the reading from the hydrometer to the graph of specific gravity and make adjustments to the developerconcentration as required. The developer concentration shall be maintained within 5-percent of the requiredconcentration.
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2.10.1 Water-Suspended (or Soluble) Developer Coating Uniformity Test. Water-suspended developers do notperform properly unless they wet the part surface and form a smooth, even coating once it dries. Lumpy or thick areas willhide small indications, while uncoated areas will not provide developer action. Poor wetting is usually due to the addition oftoo much water, which is used to replace water losses caused by drag-out or by developer wetting agents degrading overtime. Contamination by oily materials may also destroy the wetting agents. Use clean cracked-chrome panels and perform thecoating test as follows:
a. Apply the working bath developer to one half of the panel and the reference standard developer to the other half ofthe panel. (cracked chrome panel)
b. Inspect for signs of non-wetting, such as formation of beads and pulling away from edges or crack locations.
c. The panel SHALL then be dried and examined for even and complete developer coverage. If the panel exhibits signsof poor wetting or coverage perform the developer concentration check. If concentration is low add developer andretest. If the concentration is adequate and wetting and coverage is poor the wetting agent has degraded or thedeveloper is contaminated. Perform the developer penetrant contamination check or change the developer.
2.10.2 Water-Suspended (or Soluble) Developer Penetrant Contamination Test. Water-suspended developer mayalso become contaminated with penetrant. Check for fluorescent penetrant dye contamination by visual examination of thebath surface while passing a black light over it. Uncontaminated developer appears dull white while fluorescent dyecontamination will show up as specks of yellow-green, floating on the top of the bath. Low-levels of contamination can beskimmed off of the developer liquid surface. Baths that exhibit significant amounts of surface penetrant that cannot becompletely separated must be replaced.
There are a wide variety of materials available to formulate water-soluble developers; therefore, the specificgravity hydrometer readings versus concentration will vary more than they will for the water-suspendeddevelopers.
A specific gravity reading with a hydrometer is used to check the concentration of water-soluble developers. The supplier canprovide an accurate conversion chart for its particular developer. The process for performing a concentration test is asfollows:
a. Place the hydrometer directly in the tank, ensuring it floats free, not touching the tank sides. The specific gravity isread from the scale on the hydrometer. It may be more convenient to take a sample from the tank using a long,narrow glass container such as a graduated cylinder, which is deep enough to float the hydrometer.
b. Compare the reading from the hydrometer to the graph of specific gravity and make adjustments to the developerconcentration as required.
2.10.4 Dry Developer Contamination Test. Dry developers are periodically checked for evidence of contamination byperforming the following:
a. Test for penetrant contamination by examining the developer under black light, while stirring or mixing the dry-powder.
b. Visually examine for moisture while stirring or mixing the dry-powder and checking for evidence of clumps. It maybe possible to dry the powder if the water content is low by removing the lumps of developer and crushing it intoloose flakes. If it is not possible to restore the original consistency, the developer SHALL be discarded.
NOTE
For dry developer that is recycled, ten or more fluorescent specks observed under black light in a 4-inch (10-cm)diameter circle when a sample is spread into a thin layer on a clean flat surface, is unsatisfactory. Penetrantcontaminated dry developer SHALL be discarded.
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2.11 CLEANING PROCEDURE FOR PROCESS CONTROL TEST PANELS.
Process control panels (cracked-chrome panels, PSM panels, 301/302 stainless steel panels) SHALL be cleaned after use inaccordance with the following steps:
a. Clean the panels using soap and water and a soft natural bristle brush. Some handling or touching of the panelsurfaces may be necessary, but SHALL be kept to a minimum to reduce fingerprint contamination.
b. Ultrasonically clean the panels in isopropyl alcohol for 10-minutes.
c. Ultrasonically clean the panels in acetone for a minimum of 10-minutes. Acetone may not be available in alllaboratories; a 20-minute ultrasonic cleaning in isopropyl alcohol is acceptable substitute for the two 10-minutecleaning steps.
d. Allow the panels to air dry.
e. Examine the panels under black light for evidence of entrapped penetrant residues. If residues remain, repeat thecleaning process.
2.12 WATER PRESSURE AND TEMPERATURE CHECK.
Regular line pressure and water temperature is sufficient for penetrant inspections. Normal water line pressure is 10-40 psiand is checked prior to processing test parts or performing process control procedures. Normal line water temperaturebetween 50 and 100°F (10 and 37.8°C) is adequate for penetrant procedures and is checked prior to processing test parts orperforming process control tests.
NOTE
Black and white light process control requirements for Fluorescent Penetrant and Magnetic Particle are identical.Please refer to paragraph 3.2.6 for black and white light process control checks.
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T.O. 33B-1-2
CHAPTER 3FLUORESCENT MAGNETIC PARTICLE INSPECTION
SECTION I FLUORESCENT MAGNETIC PARTICLE INSPECTIONGENERAL PROCEDURE
3.1 GENERAL MAGNETIC PARTICLE PROCEDURES.
Fluorescent magnetic particle inspection can produce excellent results when performed correctly. Strict control of processconditions is essential for successful inspections. Magnetic particle material SHALL meet the requirements of AMS 2641,3045, or 3046, and successfully pass process control procedures prior to use. Black lights SHALL be capable of producingultraviolet light intensity of at least 1000-micro-watts per square centimeter at a distance of 15-inches. Ambient lightconditions SHALL be as low as possible when using black lights, not to exceed 2 foot-candles in an inspection booth. Testpart surfaces SHALL be free of thick or uneven coatings and contaminants. Inspectors SHALL meet the training andcertification requirements stated in paragraph 1.2 of T.O. 33B-1-1.
Table 3-1. Fluorescent Magnetic Particle Advantages and Limitations
Advantages Disadvantages/Limitations♦ Capable of complete coverage of simple ♦ Complex shaped parts with varying material thickness
shaped parts require multiple shots and may produce indications atcross-sections, dissimilar metals, plating breaks, andoverlaps
♦ Detects very small surface and some subsur- ♦ Surface condition must be relatively smooth and free offace discontinuities thick or uneven coatings and contaminants
♦ Effective on ferrous material ♦ Surface coating removal procedures affect process sensi-tivity (when possible SHOULD be limited to chemicalremoval processes)
♦ Inexpensive and requires less training than ♦ Cannot perform inspections on nonferrous materialother methods
♦ Readily adaptable to large volume processing
♦ In some cases requires less surface preparationthan Liquid Penetrant Inspections
3.1.1 Required Equipment and Materials. Material for Magnetic Particle Inspections must meet the requirements ofAMS 2641, 3045, or 3046, as applicable. Only fluorescent oil-suspended material SHALL be used for inspections performedusing the procedures in this Technical Order. Other materials such as powder or water-suspended vehicles both visible andfluorescent may be beneficial under unique circumstances and SHALL be approved for use on an individual application basisby the appropriate ALC NDI Manager. Stationary or portable equipment SHALL be listed in AS-455 or approved on anindividual application basis by the appropriate ALC NDI Manager.
3.1.2 Preparation of Part. Proper part preparation is essential to a successful magnetic particle procedure. Most parts willrequire coating removal. Paint or chrome plating thicker than 0.003 inches SHALL be removed. Ferromagnetic coatings suchas electroplated nickel greater than 0.001 inches SHALL be removed. All sealant SHALL be removed. If coatings arenonconductive, they SHALL be removed where electrical contact is made. A surface coating that is uneven, broken, ormarred SHALL be removed. Generally, light even coatings of primer do not require removal. All dirt, oil, or grease SHALLbe removed. Refer to the applicable -23 series Technical Order and the Structural Maintenance or Corrosion Control shop forcoating removal procedures.
3.1.2.1 Parts SHOULD be disassembled as much as practical to allow access to all part surfaces and to prevent magneticparticle indications from forming at press or close fitted areas.
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a. Demagnetize the test part to ensure any residual magnetic field does not affect the inspection procedure.
b. Perform a final wipe down of the part with a clean lint free cloth or paper towel dampened with an approved cleaner.
3.1.3 Selecting Type of Magnetizing Current. Selecting the type of current and method of application is critical to aneffective procedure. Alternating current (AC) is very effective for detecting defects open to the surface like fatigue cracks.AC SHALL NOT be used when test parameters, crack orientation, and test specimen construction are not known. AC is bestused with the wet continuous particle application method. Defects sought with AC must be open to the surface and mostsurface coating particularly plating must be removed. Direct current (DC) or more correctly, a rectified AC current (HWDC)is effective for locating both surface and subsurface defects and is used extensively on welds or when surface and/orsubsurface defects are sought. HWDC is the preferred magnetizing current for residual inspections but is most effective withthe wet continuous method of particle application.
3.1.4 Longitudinal Magnetization (Coil Shots).
CAUTION
Discontinuities can be difficult to detect when they propagate at angles less than 45° to the direction ofmagnetization. To ensure complete coverage of the test part each part SHALL be magnetized in at least twodirections at right angles to each other. This may be accomplished with circular magnetization in two or moredirections, or both circular and longitudinal magnetization, or longitudinal magnetization in two or moredirections.
Longitudinal magnetization utilizing a coil is frequently used in Air Force NDI laboratories on a variety of test parts. Themagnetic field produced will enter and exit the test part perpendicular to the direction the electrical current is passed throughthe coil. This produces an ideal situation for locating transverse indications. (see Figure 3-1) More precisely, if a bolt werelongitudinally magnetized in a coil the critical inspection areas would be under the head and between the threads as well asany transverse defect along the whole length of the bolt. On a tube-shaped part with a flanged end, the critical inspection areawould be the radius at the base of the flange and transverse discontinuities along the length of the tube. Longitudinalmagnetization SHOULD be performed after circular magnetization if a circular shot is required. Since the magnetic fieldenters and exits the test part it can be observed by field indicators and therefore any residual field can be removed duringdemagnetization.
Figure 3-1. Longitudinal Magnetization in a Coil
3.1.4.1 Cross-Sectional Area. The relationship between the cross-sectional area of the part and the cross-sectional areaof the coil will determine whether the part can be inspected within a coil by laying the part in the bottom, or by centering the
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part in the coil, and which formula will be used for estimating the amperage required. The cross-sectional area for the partand coil are determined as follows:
A = πr2
Where: A = Cross-sectional Area
π = 3.1416
r = radius (1/2 of the diameter)
The diameter of the part is the largest distance between any two points on the outside circumference.
Example: An 18-inch diameter coil is used to inspect a part having a 2-inch diameter
Area of Coil (18” diameter) Area of Part (2” diameter)
A = πr2 A = πr2
A = π(9)2 A = π(1)2
A = 254.46 sq. inches A = 3.14 sq. inches
3.1.4.1.1 When the cross-sectional area of the part is less than one-tenth of the cross-sectional area of the coil; the part ismagnetized lying in the bottom of the coil.
3.1.4.1.2 When the cross-sectional area of the part is greater than one-tenth of the cross-sectional area of the coil; the partmust be magnetized in the center of the coil.
3.1.4.1.3 The diameter of the largest part that can be magnetized lying in the bottom of a coil or placed next to the coil wallfor some typical coil sizes is listed in (see Table 3-2). For any given coil diameter, parts with diameters larger than thoselisted SHALL be magnetized by some other method, such as centering them in the coil, using a cable wrap, or using a largercoil.
Table 3-2. Coil Size vs. Maximum Part Diameter for Bottom of Coil Shot
Coil Diameter (inches) Maximum Part Diameter (inches)8 2.5
12 3.8
15 4.7
18 5.7
20 6.3
24 7.6
3.1.4.2 Selecting the Correct Amperage for a Coil Shot. The useful magnetizing field produced from a coil extendsapproximately 6 to 9-inches to either side of the coil. For longer parts, one or more inspections are required along the lengthof the part, when repositioning longer parts in the coil allow a 3-inch overlap. The formulas are intended for parts with anL/D ratio (length divided by diameter) between 3 and 15. To inspect parts with an L/D ratio less than 3 consult the WeaponsSystem ALC NDI Manager. For parts with an L/D ratio greater than 15, use 15 as the value for the ratio.
3.1.4.2.1 Formula for Part Lying in Bottom of Coil. The following formula is used when the cross-sectional area of thepart is less than one-tenth the cross-sectional area of the coil(s) and is used whenever the part is lying in the bottom of thecoil, or is placed next to the coil wall during magnetization. If the part has hollow portions, replace D with Deff (seeparagraph 3.1.4.2.2).
I = KDNL
Where:
I = Current through coil (amperes)
K = 45,000 (a constant, ampere-turns)
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L = Length of the part (inches)
D = Diameter of the part (inches)
N = Number of turns in coil
Example: Determine the current required to longitudinally magnetize a steel part, 10-inches long with a diameter of 2-inches using a 12-inch diameter coil having 5 turns. To determine a cross-sectional area ratio between part and coil, refer to(see paragraph 3.1.4.1). Substituting the known values and doing the calculations gives:
I = 45000 x 25 x 10
I = 1800 amperes
Table 3-3. Typical Current for Five-Turn Coil with Part at the Bottom of Coil
Part length in Part Diameter in Ampere-Turns AmperesInches (L) Inches (D) L/D Ratio Required Required
12 3 4 11,250 2,250
12 2 6 7,500 1,500
16 2 8 5,625 1,125
10 1 10 4,500 900
18 1 1/2 12 3,750 750
14 1 14 3.214 643
3.1.4.2.2 Determining the Effective Diameter. For hollow and cylindrical test parts, the diameter of the test part issubstituted with the calculated effective diameter. Calculate the effective diameter as follows:
Example: Determine the effective diameter of a tube-shaped part with an outside diameter equal to 5-inches and an insidediameter of 4.5-inches.
3.1.4.3 Formula for Part in Center of Coil. This formula is used when the cross-sectional area of the part is greater thanone-tenth and less than one-half of the cross-sectional area of the coil(s).
I = KRN(6(L/D) – 5)
Where:
I = Current through coil (amperes)
K = 43,000 (a constant, ampere-turns)
R = Radius of coil (inches)
N = Number of turns in coil
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L = Length of part (inches)
D = Diameter of the part (inches)
The term 6(L/D)-5 is called the effective permeability.
Example: Determine the current needed to longitudinally magnetize a 12-inch long part with a diameter of 4-inches andusing a 5 turn, 12-inch diameter coil. To determine the cross-sectional area ratio between the part and the coil, refer to (Seeparagraph 3.1.4.1). If the part contains hollow portions, D should be replaced with Deff (See paragraph 3.1.4.2.2).
Substituting known values gives:
I = 43000 x 65(6(12/4) - 5)
I = 3969 amperes
3.1.4.4 Procedure for Inspecting Test Parts in Coil. Ensure the process controls on equipment and material have beenperformed prior to inspection. Ensure part preparation is completed and is satisfactory for effective magnetic particleinspection. All relevant safety equipment and procedures directed by Chapter 3 Section VIII of T.O. 33B-1-1 and AFOSHStandard 91-501 are required in this inspection procedure and SHALL be adhered too.
a. Calculate the cross-sectional area of the test part and the coil. From the calculation, determine the position in whichthe test part will lay in the coil. (See paragraph 3.1.4.1)
b. Calculate the required amperage. (See paragraph 3.1.4.2.1 or paragraph 3.1.4.3)
c. Clear the magnetic particle unit bench of any obstructions or debris.
d. Unlock and roll back the tailstock. Lock the tailstock down when it has cleared the area needed to perform theinspection.
e. Unlock and position the coil so that the inspector has easy access to both sides of the coil and has room to positionthe test part as required. Lock down the coil.
f. Set the unit for AC or DC (as required) operation in the coil configuration. Some units will have an Energize Masterswitch that needs to be pulled out to the ‘‘ON’’ position.
g. Place test part in the coil as required. (see Figure 3-1)
h. Set amperage at one-half of the calculated value for the test part.
(1) Initiate 2 shots in quick succession.
(2) Measure the field strength with a Hall-Effect probe gauss meter. Acceptable field strength is 30 to 60G forcontinuous particle applications and residual applications.
(3) Increase amperage by 10% and repeat procedure until an acceptable gauss reading is obtained.
(4) If a gauss meter is not available, use the same procedure with a QQI shim affixed to the test part in the area ofinterest (See paragraph 3.1.9). Use the wet continuous particle application method (spray or flow the suspensionover the test part, and then divert the suspension simultaneously or slightly before energizing the magneticcircuit). Inspect the QQI shim under black light illumination. When a bright and defined build-up of magneticparticles is observed, sufficient magnetic field strength is present to perform the inspection. (see paragraph3.2.1.1)
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NOTE
When performing inspections on multiple like items it is not necessary to use the QQI shims or the gauss meteron each individual test part. Once acceptable amperage has been selected, inspect like items at the settingsdetermined by the QQI test.
i. Place the test part in the coil. (see Figure 3-1)
(1) Perform a wet continuous particle application method (spray or flow the suspension over the test part then divertthe suspension simultaneously or slightly before energizing the magnetic circuit).
(2) Initiate 2 shots in quick succession.
(3) Examine the test part under black light illumination. This technique is most sensitive to transverse flaws.
j. Demagnetize the test part. (See paragraph 3.1.7.2)
k. Post-clean the test part. (See paragraph 3.1.8)
3.1.5 Longitudinal Magnetism Induced by Portable Yokes. Portable yokes, also known by trade names such as‘‘Parker Probes’’, provide a reliable induced magnetic field in test parts and are commonly used for inspection outside theshop environment. This equipment is easy to use and adequate when testing small castings or machine parts for surfacecracks and weld inspection. They induce a strong magnetic field into that portion of a part that lies between the poles or legsof the yoke. The induced field flows from one leg of the yoke to the other regardless of the style or leg configuration. Sinceno current is flowing through the part being subjected to inspection, it is impossible to overheat or burn the part.
NOTE
Magnetize the test part in 2 or more directions or use a circular shot to ensure 100% inspection coverage.
3.1.5.1 Procedure for Inspecting Test Parts with Portable Yoke. Ensure the process controls on equipment andmaterial have been performed prior to inspection. Ensure part preparation is completed and is satisfactory for effectivemagnetic particle inspection. All relevant safety equipment and procedures directed by Chapter 3 Section VIII of T.O. 33B-1-1 and AFOSH Standard 91-501 are required in this inspection procedure and SHALL be adhered too.
a. Place test part on a nonmagnetic surface.
b. Set the portable yoke for AC or DC (as required) operation and turn the field intensity thumb dial to full power.
c. Place the leg ends of the yoke on the part so that the intended inspection area lies between the leg poles. Energize theyoke for five (5) full seconds.
d. Use a field indicator to check for a residual field. If a half scale deflection is obtained the test part can be effectivelyinspected with magnetic particle procedures.
e. If the field indicator does not show the presence of a strong residual field place a QQI shim in the area of interest andperform a wet continuous particle application with the yoke energized at full power. (see paragraph 3.2.1.1)
(1) Observe the QQI shim under black light illumination. If a bright well-defined indication appears, the test part canbe inspected with the wet continuous method.
(2) If an indication does not appear, some other NDI method will be more appropriate for the test part.
NOTE
When performing inspections on multiple like items it is not necessary to use the QQI shims or gauss meter oneach individual test part. Once acceptable amperage has been selected, inspect like items at the settingsdetermined by the QQI test.
f. Place the leg ends of the yoke on the part so that the intended inspection area lies between the leg poles.
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g. Perform a wet continuous particle application with the yoke energized at full power.
h. Inspect the area under black light illumination. Note any defects present.
(1) Look for evidence of magnetic saturation.
(2) If the test part displays signs of magnetic saturation, demagnetize the part, turn the field intensity thumb dialcounter clockwise one-quarter turn and inspect again.
i. Turn the portable yoke 90 degrees, place the leg ends on the part and perform the application and inspectionprocedure again.
j. Repeat the procedure until 100% of the inspection area is completed.
k. Demagnetize the test part as required. (See paragraph 3.1.7)
l. Post-clean the test part. (See paragraph 3.1.8)
Figure 3-2. Magnetic Field Produced by a Portable Yoke
3.1.6 Circular Magnetism Produced by Direct Contact. Circular magnetization is used for the detection of radialdiscontinuities around edges of holes or openings in parts. It is also used for the detection of longitudinal discontinuities,which lie in the same direction as the current flow. This technique produces circular magnetization by passing electric currentthrough the part itself (see Figure 3-3). Direct contact is applied to parts by placing them directly between the headstock andtail stock. Lead faceplates and copper braid pads SHALL be used to prevent arcing, overheating, and splatter. Electricalcontact SHALL be as good as practicable to minimize over heating or arcing. Excessive heating at the contact points maynegatively affect the serviceability of the test part (e.g., burn the part; affect its temper, finish, etc.).
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Figure 3-3. Circular Magnetic Field Produced by Direct Contact
3.1.6.1 Direct Contact Method Amperage Calculation. Amperage selection for the direct contact method is simple andstraight forward, 300 to 800 amperes per inch of diameter. Generally, the lower (300 to 500 amperes) values produceadequate field strength for most applications.
3.1.6.1.1 Procedure for Direct Contact Circular Magnetization. Ensure the process controls on equipment and materialhave been performed prior to inspection. Ensure part preparation is completed and is satisfactory for effective magneticparticle inspection. All relevant safety equipment and procedures directed by Chapter 3 Section VIII of T.O. 33B-1-1 andAFOSH Standard 91-501 are required for this inspection procedure and SHALL be adhered too.
CAUTION
Precautions SHALL be taken to ensure that the electric current is not flowing while contacts are being applied orremoved and that excessive heating does not occur in the contact area. Prods are not authorized on aerospacecomponents and portable clamps SHALL only be used on aerospace components with direction and approval ofthe appropriate ALC NDI Manager.
a. Measure the diameter of the test part. Determine the amperage required to perform the inspection. Start with thelowest setting possible for a given test part.
b. Clear the magnetic particle unit’s bench area of any obstruction or debris.
c. Place a central bar conductor (CBC) between the headstock and tailstock. Lock down the tailstock.
d. Pour or spray the bath vehicle where the bar and contact pads meet. (Completely saturating the area is not necessary.)
e. Fully depress the foot switch to clamp the part firmly in place.
f. Set unit for AC or DC (as required) operation in the contact mode. Some units will have an Energize Master switchthat needs to be pulled out to the ‘‘ON’’ position.
g. Set the amperage potentiometer to the approximate setting required for the test part.
h. Initiate the contact shot. Note the amperage indicated on the ammeter. Adjust the potentiometer to achieve therequired output.
i. Initiate the contact shot again and verify the amperage indicated on the ammeter meets the setting requirements.
j. Fully depress the foot switch to release the CBC, and then remove the CBC.
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k. Place the part to be inspected between stocks. Adjust the tailstocks to accommodate the test part. Lock down thetailstock.
l. Pour or spray the bath vehicle where the part and contact pads meet. (Completely saturating the area is notnecessary.)
m. Fully depress the foot switch to clamp the part firmly in place.
n. Check the equipment setting to ensure correct configuration.
o. Place a QQI shim in the area of interest. (see paragraph 3.2.1.1)
p. Perform the wet continuous method of particle application. Spray or flow the suspension over the test part then divertthe suspension simultaneously or slightly before energizing the magnetic circuit. Initiate 2 shots in quick succession.
q. Inspect the QQI shim under black light illumination. When a bright and defined build-up of magnetic particles isobserved, sufficient magnetic field strength is present to perform the inspection.
r. Increase the amperage until a good indication is formed on the QQI.
NOTE
When performing inspections on multiple like items it is not necessary to use the QQI shims or gauss meter oneach individual test part. Once acceptable amperage has been selected, inspect like items at the settingsdetermined by the QQI test.
s. Perform the inspection with the equipment configuration and amperage derived from this procedure.
t. Demagnetize the test part as required. (See paragraph 3.1.7)
u. Post-clean the test part. (See paragraph 3.1.8)
3.1.6.2 Circular Magnetism Using a Central Bar Conductor (CBC). Circular magnetism induced with a CBC is anexcellent procedure to inspect the inside diameter of ring-shaped or cylindrical test parts. The effective field strengthdecreases the further from the CBC it extends. If the outside surface of the test part must be inspected and the direct contactmethod cannot be used, a CBC shot with DC will provide the most effective inspection using stationary equipment. AC is thepreferred current for inspecting the inside surface of ring-shaped or cylindrical test parts. Circular magnetism is sensitive tolongitudinal cracks as shown in (see Figure 3-4 and Figure 3-5) and is effective for inspecting radial cracks emitted for holesor other openings in the test part.
Figure 3-4. Circular Magnetism Using a CBC
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Figure 3-5. Circular Magnetism Using a CBC on Ring-Shaped Parts
3.1.6.2.1 Central Bar Conductor Method Amperage Calculation. The rule of thumb for a CBC shot varies from 100 to1000 amperes per inch of diameter. For the purpose of this inspection procedure, we will use the same value as the directcontact method, 300 to 800 amperes per inch of diameter. When the CBC is passed through a ring-shaped or cylindrical partand is placed against an inside wall of the part (offset central conductor), the diameter for amperage calculation is the sum ofthe diameter of the CBC plus twice the wall thickness.
Example: Inspect a 6-inch tube with a one-inch CBC, the wall thickness is 0.25-inch.
[1 + (0.25 + 0.25)]
= 1 + 0.5
= 1.5-inches of diameter
3.1.6.2.2 Effective Region of Inspection. The effective region of inspection when using an offset central bar conductoris equal to 4 times the diameter of the bar conductor. Effectively, a 1-inch CBC will yield a 4-inch inspection area; 2-incheson either side of the center of the CBC.
3.1.6.2.3 Procedure for Circular Magnetization using a CBC. Ensure the process controls on equipment and materialhave been performed prior to inspection. Ensure part preparation is completed and is satisfactory for effective magneticparticle inspection. All relevant safety equipment and procedures directed by Chapter 3 Section VIII of T.O. 33B-1-1 andAFOSH Standard 91-501 are required for this inspection procedure and SHALL be adhered to.
CAUTION
Precautions SHALL be taken to ensure that the electric current is not flowing while contacts are being applied orremoved and that excessive heating does not occur in the contact area.
a. Calculate the diameter of the test part. Determine the amperage required to perform the inspection. Start with thelowest setting possible for a given test part.
b. Clear the magnetic particle unit’s bench area of obstructions or other debris.
c. Place a central bar conductor between the headstock and tailstock. Lock down the tailstock.
d. Pour or spray the bath vehicle where the bar and contact pads meet. (Completely saturating the area is not necessary.)
e. Fully depress the foot switch to clamp the CBC firmly in place.
f. Set unit for AC or DC (as required) operation in the contact mode. Some units will have an Energize Master switchthat needs to be pulled out to the ‘‘ON’’ position.
g. Set the amperage potentiometer to the approximate setting required for the test part.
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h. Initiate the shot. Note the amperage indicated on the ammeter. Adjust the potentiometer to achieve the requiredoutput.
i. Initiate the shot again and verify the amperage indicated on the ammeter meets the setting requirements.
j. Fully depress the foot switch to release the CBC, and then remove the CBC.
k. Place the CBC through the part to be inspected and insert the CBC into the stocks. Adjust the tailstocks toaccommodate the test part and CBC. Lock down the tailstock.
l. Pour or spray the bath vehicle where the CBC and contact pads meet. (Completely saturating the area is notnecessary.)
m. Fully depress the foot switch to clamp the CBC firmly in place.
n. Check the equipment setting to ensure correct configuration.
o. Place a QQI shim in the area of interest. (see paragraph 3.2.1.1)
p. Perform the wet continuous method of particle application. Spray or flow the suspension over the test part then divertthe suspension simultaneously or slightly before energizing the magnetic circuit. Initiate 2 shots in quick succession.
q. Inspect the QQI shim under black light illumination. When a bright and defined build-up of magnetic particles isobserved, sufficient magnetic field strength is present to perform the inspection.
r. Increase the amperage until a good indication is formed on the QQI.
NOTE
When performing inspections on multiple like items it is not necessary to use the QQI shims or the gauss meteron each individual test part. Once acceptable amperage has been selected, inspect like items at the settingsdetermined by the QQI test.
s. Perform the inspection with the equipment configuration and amperage derived from this procedure.
t. Demagnetize the test part as required. (See paragraph 3.1.7)
u. Post-clean the test part. (See paragraph 3.1.8)
3.1.7 Demagnetizing Test Parts. Unless a specific instruction states demagnetization is not required, all aircraft testparts SHALL be demagnetized. All other test parts SHOULD be demagnetized each time the inspection procedure isperformed.
NOTE
It is recommended that all parts circularly magnetized be magnetized longitudinally at the same or higheramperage prior to demagnetization.
3.1.7.1 Demagnetization on Stationary Equipment Using AC.
a. Select AC, Coil, and Demag operation on the unit’s selector switches.
b. Turn the current control clockwise to 3/4 of scale or 10% greater than the magnetizing current used on the test part.
c. Initiate shot. During the AC Demag cycle the current is ramped down to zero in approximately 5 to 10 seconds.
d. Using a field indicator measure the ends of the test part. Residual field SHALL be two (2) increments or less on fieldindicators or three (3) gauss or less using a hall-effect gauss meter.
3.1.7.2 Demagnetization on Stationary Equipment Using DC.
a. Select DC, Coil, and Demag operation on the unit’s selector switches.
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b. Turn the current control clockwise to 3/4 of scale or 10% greater than the magnetizing current used on the test part.
c. Initiate shot. Output current will pulse at reversing polarities and decay to zero during it’s approximately 25 to 30second cycle.
d. Using a field indicator measure the ends of the test part. Residual field SHALL be two (2) increments or less on fieldindicators or three (3) gauss or less using a hall-effect gauss meter.
3.1.7.3 Demagnetization Using Portable Yokes. Portable yokes present some unique problems, if the part comes incontact with both legs of the yoke in the same general configuration as the magnetizing shot, the part can be magnetizedagain. AC is recommended for most demagnetization operations because the nature of alternating currents’ reversing currentflow will aid in the demagnetization of a test part.
a. Open the legs of the yoke so the test part can pass through it.
b. Hold the test part 1-foot from the yoke.
c. Slowly pass the part through the yoke legs and 3 to 5 feet beyond while the yoke is energized.
d. Turn the test part 90° and repeat the procedure.
e. If the test part is too large to handle in this way, follow the same basic procedures moving and rotating the yokeinstead of the test part.
f. Using a field indicator, measure the ends of the test part. Residual field SHALL be two (2) increments or less on fieldindicators or three (3) gauss or less using a hall-effect gauss meter.
3.1.8 Post-Cleaning Test Parts After Magnetic Particle Inspection. After the demagnetization operation has beenaccomplished, dip the test part in clean vehicle that does not contain magnetic particles. Check the test part under black lightillumination for fluorescence. Wipe down the test part with a clean cloth or paper towel dampened with an approved solvent.Dry with lowpressure shop air. After portable inspections, wipe the test part down with a clean dry cloth or paper towel.Perform a final wipe down with a clean cloth or paper towel dampened with an approved solvent. Check the test part underblack light illumination for excessive fluorescence.
3.1.9 QQI Shims. The QQI is a small, thin, metal shim, made of low carbon steel that contains artificial defects forestablishing or verifying MPI techniques. The artificial flaw is etched or machined on one side of the foil to various depthsbut usually 30% of the foil thickness. In use, the shims are firmly attached to the test part surface with the flawed side downagainst the test part in the area of interest. Tape is most commonly used and is placed on all four sides of the shim to preventmagnetic particle vehicle from seeping under the shim. The QQI SHOULD only be used with the wet continuous method ofparticle application.
Figure 3-6. Quantitative Quality Indicators (QQI)
3.1.10 Magnetic Particle Inspection Interpretation. Magnetic Particle interpretation is done under black light in aninspection booth or darkened area. Portable inspections may require a locally manufactured or purchased tent-like apparatusmade of dark cloth or canvas to reduce ambient light levels and enhance inspection sensitivity. Identify indications as linearor rounded and measure the largest dimension of the indication for comparison to acceptance criteria. A rounded indicationhas length that is less than 3 times its width. A linear indication has a length 3 or more times its width. Evaluate indicationsaccording to limits in technical data. If technical data is not specific or no technical data is available, consider all linearindications relevant and rounded indications 1/16th of an inch or larger relevant for both aircraft and nonaircraft test parts.
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3.1.10.1 Defects will generally be linear or aligned porosity type indications resulting from:
3.1.10.3 Defects should be marked on the part surface with an approved marking pencil. Measure the defect and noteidentifying characteristics. Describe the defect in detail including its location and orientation. Then document inspectionfindings IAW Air Force Instructions and local directives. An example of a good defect description is as follows: ‘‘Magneticparticle inspection of welds on transfer case part number 128-6380. Crack noted and marked on the inlet to case weld. Theindication is sharp, well defined, bright, and linear. The defect is 2.125 inches long and runs down the center of the weldcrown.’’
NOTE
Air Force NDI personnel SHALL NOT make serviceability determinations except as described in AFI 21-101(field units only). The role of the NDI inspector is normally limited to providing a detailed description of thedefect and its location. Disposition and repair responsibility for a flawed part or airframe lies with StructuralMaintenance personnel or the owning workcenter and the appropriate engineering authority.
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SECTION II FLUORESCENT MAGNETIC PARTICLE PROCESS CONTROLPROCEDURES
3.2 SYSTEM EFFECTIVENESS CHECK (KETOS RING).
NOTE
The prior to use or daily requirement for black light UV intensity check and particle concentration/suspensionsettling tests SHALL be performed and within limits prior to performing the system effectiveness check.
The Ketos ring has been the standard tool used by the Air Force to evaluate system effectiveness for some years now. Whileit is a useful tool, it has definite limitations. To realize the greatest sensitivity to change in the bath material, baseline theKETOS ring and the magnetic particle unit by recording the actual readings at each checkpoint in the test when the bath isnew. Compare subsequent test reading to the baseline to observe small changes immediately. Conduct the systemeffectiveness check as follows:
a. Check for residual magnetism by applying the magnetic particle bath, then wait 60-seconds for any indications toform. If any indications are present on the outer edge, the ring SHALL be demagnetized and the check repeated untilno indications are formed.
b. Place a one-inch central bar conductor (CBC) between the stocks and initiate the air cylinder to clamp the CBC intoplace. Set unit for AC operation in the contact mode. Adjust the current control until 1000 amps is displayed on thereadout.
c. Remove the CBC from the stocks and slide the Ketos ring onto the bar. Clamp the CBC into the stocks. Perform thewet continuous method of particle application at 1000 amperes (see Table 3-4). Wait 60-seconds for any indicationsto form on the outer edge of the Ketos ring. An indication should form above the first hole (see Figure 3-7).
d. Remove the CBC from the stocks and slide the Ketos ring off the bar. Place the CBC back into the stocks and initiatethe air cylinder to clamp it down.
e. Set the magnetic particle unit to DC operation in the contact mode. Adjust the current control until 1400 amperes isdisplayed on the readout.
f. Remove the CBC from the stocks and slide the Ketos ring onto the bar. Clamp the CBC into the stocks. Perform thewet continuous method of particle application at 1400 amperes (see Table 3-4). Wait 60-seconds for any indicationsto form on the outer edge of the Ketos ring. An indication should form above the third hole (see Figure 3-7).
g. Repeat step d, step e, and step f at 2500 and 3400 amperes, indications should appear above holes five and six (seeFigure 3-5).
Lack of indications at the proper holes may indicate a malfunctioning magnetic particle unit, a low particle concentra-tion, or a Ketos ring not in the annealed condition. The cause of the malfunction SHALL be determined with additionalprocess checks (e.g., amp indicator, concentration, etc,) and corrected prior to performing additional magnetic particleinspections with the deficient system.
NOTE
Ketos rings that are plated or corroded SHALL NOT be used. Corrosion and plating can cause false readings.
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Figure 3-7. Ketos Ring
Table 3-4. Ring Specimen Indications
Type of Suspension D.C. Amperage Minimum No. of Holes IndicatedNon-fluorescent 1400 3
2500 5
3400 6
Dry Powder 1400 4
2500 6
3400 7
Fluorescent 1400 3
2500 5
3400 6
A.C. Amperage
Non-fluorescent 1000 1
Dry Powder 1000 1
Fluorescent 1000 1
3.2.1 Quantitative Quality Indicators (QQI). Test specimen(s) used with QQIs offer a more versatile means of checkingsystem performance than afforded by the Ketos ring. The specimens can be real parts or designed to be representative of themost challenging inspection to be currently performed. This combination is capable of providing an adequate check on anymagnetic particle inspection system. Poor indications may require further process control evaluations to be performed (e.g.,amp indicator check, concentration check, etc.). Even though QQIs respond to the applied, not residual field, demagnetizationis necessary of the specimen(s) in order to remove the previously applied inspection media.
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3.2.1.1 Using the QQI.
CAUTION
Exercise care when using QQIs on curved surfaces. Excessive bending will damage a QQI. Usually the thinnerQQI will be used on curved surfaces; however they are fragile. The thicker QQI is less fragile, but can still bedamaged by excessive bending.
NOTE
Use of a QQI will require a second magnetic particle inspection (without the QQI) if the QQI is placed in an areawhere a crack may be present.
Thoroughly clean and dry the area where the QQI is placed. Use cleaning solvent, IAW MIL-C- 38736. Place the appropriateQQI in place with the slot side against the surface of the part and one axial groove parallel to the current direction. If the testpart has a very specific area of interest, place the QQI in this area. If the test part is a 100% coverage inspection, place theQQI in the least favorable inspectable location on the test part for that particular shot. In general, the 30-percent deep slot isadequate for most defects. Critical inspections may require the 15- percent deep slot; and rough castings or weldments mayrequire the 60-percent deep slot. Use transparent adhesive tape (e.g., Scotch brand 191, 471, or 600 series) to hold the QQI inplace. Apply the tape to all four edges to ensure good contact (with no air gap) and to prevent particles from getting under theQQI. The tape SHALL NOT cover the area of the QQI where the indications will form. Super glue may be used to provide afixed bond. Super glue can be removed by soaking in acetone. Conduct the inspection and observe the results under theappropriate lighting.
3.2.2 Cracked Parts. If available, the ultimate specimens for the performance tests are cracked parts. Poor indicationsmay require further process control evaluations to be performed (e.g., amp indicator check, concentration check, etc.). Theserequire careful handling to remain corrosion-free and retain their flaw size.
3.2.3 Amperage Indicator Check. Perform amperage indicator accuracy checks using a calibrated ammeter/shuntauthorized in AS-455. Authorization for any other ammeter/shunt SHALL be approved by the AF NDI Office. Operate theammeter/shunt in accordance with the commercial manufacturer’s operating instruction. DC amperage variations exceeding±10% of read-out value or ±60 amperes, whichever is greater, requires trouble shooting and maintenance action. ACamperage variations exceeding ±10% requires trouble shooting and maintenance action. Perform the amperage indicatorcheck on the range that is expected to be used. As a minimum, the amperage range used in the KETOS ring check SHALL betested.
3.2.4 Quick Break Test. The quick break test is accomplished to ensure an accurate decay rate, which is sufficient forquick break magnetization. A quick break tester is authorized in AS-455. Operate the quick break tester in accordance withthe commercial manufacturer’s operating instructions. Failure of the quick break test requires trouble shooting andmaintenance action. The quick break test SHALL be performed at intervals stated in (see Table 1-1).
3.2.4.1 Generic Quick Break Test Instructions. In the absence of a commercial manufacturer’s instruction, thefollowing procedure will be sufficient for the Magnaflux Quick Break Tester, Part Number 148335 or equivalent:
a. Clear the horizontal wet bench unit of all ferrous parts, rags, or other obstructions.
b. Retract the tailstock and lock it down so the operator has an unobstructed access to the coil.
c. Move the coil 12 to 18 inches from the headstock and lock it down.
d. Remove the copper bus bar and bracket from the quick break tester. Center the tester on the bottom surface of theinside diameter of the coil. The tester should be placed perpendicular to the coils with the studs facing up. If the studsare facing up and the indicating lamp is facing the tail stocks, the tester is in the correct position.
e. Set magnetic particle unit for DC operations at 2000 amperes in the coil mode.
f. Initiate the coil shot and observe the indicating lamp as the shot terminates. A flash of the lamp indicates a good‘‘quick-break.’’ Sometimes a flash may occur at the beginning and end of the shot; this is acceptable. The absence ofa flash indicates a malfunction in the circuitry of the magnetic particle unit.
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3.2.5 Dead Weight Check. The dead weight check is conducted on portable electromagnetic yokes (e.g., Parker Probes).Repair or replace equipment that fails the dead weight check. Perform the process control check as follows:
3.2.5.1 Locally manufacture test weights from SAE 4130 or 4340 steel. A 10-pound weight is required for AC operation,either a 30- or 50-pound weight is required for DC operation. (For more information on the manufacture of test weights, seeT.O. 33B-1-1)
a. Place the 10-pound weight on the floor. Set the portable magnetic particle unit to AC operation. Extend the legsstraight out and space the legs from three to six inches. Place the leg ends on the test weight and energize the unit.Lift the test weight off the ground. A portable magnetic particle unit must be able to hold suspended the ten-poundtest weight.
b. Place the 30-pound weight on the floor. Set the portable magnetic particle unit to DC operation. Extend the legsstraight out and space the legs from two to four inches. Place the leg ends on the test weight and energize the unit.Lift the test weight off the ground. A portable magnetic particle unit must be able to hold suspended the 30-poundtest weight. A 50-pound test weight and a four to six inch leg spread may also be used.
Figure 3-8. Black Light Intensity
3.2.6 UV-A Black Light Intensity and Ambient Light Requirements.
CAUTION
When performing portable fluorescent magnetic particle inspection, a dark colored canvas or photographers blackcloth SHALL be used to darken the area during the examination. A portable fluorescent magnetic particleinspection SHALL NOT be performed in ambient conditions, lighting conditions above 20 foot-candles. Blacklights SHALL be directed away from the eyes and gloves SHALL be worn to protect the skin from exposure toultraviolet light. Any glove approved for use in magnetic particle or liquid penetrant inspections will provideadequate protection to the skin from ultraviolet light. Ultraviolet light filtering safety eyewear SHALL be used toprevent potential detrimental health effects.
Black lights SHALL be tested with an approved and calibrated UV-A digital radiometer at intervals required in (Table 1-1).The intensity SHALL be at least 1000-micro-watts per square centimeter (µW/cm2) measured at a distance of 15 inches fromthe face of the black light filter lens. The UV-A digital radiometer is calibrated in accordance with T.O. 33K-1-100-CD-1.
3.2.6.1 Excessive Ambient White Light. There are two white light tests that must be performed to maintain a goodinspection system, each individual black light is tested for white light output and a collective test is performed for inspection
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booths. The inspection booth test measures ambient white light from all sources including white light emitted from blacklights and reflected white light from areas adjacent to the inspection booth. The individual black light test measures whitelight emitted directly from the black light. The white light tests are performed with an approved and calibrated photometer atintervals directed in (see Table 1-1). The white light photometer is calibrated in accordance with TO 33K-1-100-CD-1. Forstationary inspections (laboratory inspection booths), the ambient white light SHALL NOT exceed 2 foot-candles. Theindividual black light test is accomplished in a fully darkened booth with the tested black light on and all others off. Thecheck is similar to the UV-A test with the sensor 15-inches from the black light filter lens. The collective test is performed inthe inspection booth with all black lights normally used in the booth turned on. The photometer sensor is placed in the areawhere parts are normally inspected. The acceptance criteria for both tests are the same; no more than 2 foot-candles of whitelight is allowed. For portable inspections, where ambient light conditions cannot be controlled below 2 foot-candles, higherUV-A intensities at the inspection surfaces are required. The minimum UV-A intensity under varying ambient light levels(see Table 3-5). Values of 3,000 µW/cm2 can be achieved with acceptable black light sources by moving the source closerthan 15-inches to the part, yet leaving sufficient space to observe the specific area of interest.
Table 3-5. Empirical Black Light Intensity Requirements at Various Ambient Light Levels for PortableInspections
2 to 10 Dark-to-dim interiors such as warehouses or 3000storage areas
10 to 20 Dim interiors 5000
3.2.7 Fluorescent Background Check for New Bulk Suspension. A fluorescent background check SHALL beaccomplished on vehicle material used in the fluorescent magnetic particle inspection method if conformance to DOD-F-87935 is in question. One procedure for checking the background is as follows:
a. Obtain a clean glass tube of sufficient length to reach from the middle of the bulk vehicle container to at least 6-inches above the container opening when it is in the vertical position.
b. Insert the tube slowly into the bulk vehicle.
c. Place thumb over protruding end of the glass tube and remove the tube from the container.
d. Illuminate vehicle in the glass tube with a black light in a darkened area.
e. If vehicle does not fluoresce, proceed with its use. If the vehicle fluoresces, determine the fluorescence in accordancewith the appropriate section of DOD-F-87935. Dispose of vehicle not conforming to DOD-F-87935.
3.2.8 Particle Concentration Test.
NOTE
Prior to adding the magnetic particles to the vehicle, the particles SHALL be demagnetized to eliminate anyclumping that may have developed during storage due to magnetization.
The following procedure is used to determine the concentration of magnetic particles and to check for the accumulation ofdirt or other contaminants in a suspension. The equipment required is a 100-cubic centimeters (cc) or 100-milliliters (ml)pear-shaped, graduated centrifuge tube and nonferrous stand (see Figure 3-9). The difference between milliliters (ml) andcubic centimeters (cc) in this case is negligible, and the two terms are used interchangeably for this paragraph.
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Figure 3-9. Centrifuge Tube
a. Thoroughly agitate the suspension.
b. Run suspension through the hose and nozzle for at least 1-minute. This is to ensure the suspension in the hose is freshand agitated.
c. Fill the 100 cc (100 ml) centrifuge tube with agitated suspension using the hose.
d. Demagnetize the suspension in the tube to reduce clumping.
e. Place the centrifuge tube in its non-ferromagnetic stand, and allow the suspension to set on a vibration free surfacefor:
• 1-hour for oil baths, OR• 30-minutes for water baths.
f. Observe the total level (concentration) of settled particles at the end of the settling period. The level of contaminantsis subtracted from the total concentration to obtain the current concentration of particles.
NOTE
Besides the magnetic particles, dirt in the bath will also settle out and usually show as a separate layer on top ofthe particles. The layer of dirt and lint is usually easily distinguishable, since it is of a different color and texturefrom the particles. Also easily distinguishable are iron peening shot and blasting grit; both will settle faster andlie beneath the magnetic particles.
g. If the concentration of magnetic particles is above or below the range required, correct by adding vehicle or magneticparticle powder respectively. Visible magnetic particle bath concentrations SHALL be: 1.2 to 2.4 milliliters (ml) ofparticles per 100 ml of vehicle. The optimum range is 1.5 to 2.0 ml/100 ml. Fluorescent magnetic particle bath
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concentrations SHALL be: 0.1 to 0.4 ml of particles per 100 ml of vehicle. The optimum range is 0.15 to 0.20 ml/100ml. Repeat step a through step f of the settling test after making corrections.
h. Return contents of centrifuge tube to the in-use bath, and clean the tube prior to next test.
NOTE
Part processing and/or process control inspections SHALL NOT be accomplished prior to the full 1-hour (or 30-minute) time limit passing and the bath has been approved for daily use. The suspension concentration SHALLbe within T.O. limits prior to use.
3.2.9 Vehicle Fluorescence Check. The settling test (see paragraph 3.2.8) for particle concentration can also be used tojudge vehicle fluorescence and is readily performed at a stationary unit. It is not as accurate as the laboratory test but isreasonably quantitative and reproducible. It can be easily standardized with the material in use, and is quite satisfactory as adaily guide for the inspector. The following procedure is used to perform the vehicle fluorescence check after the steps in thesettling test are completed.
a. Illuminate the suspension in the centrifuge tube with black light in a darkened area. Only the particle layer willfluoresce. Dirt, lint, etc. will usually settle more slowly than the particles and may be seen as a non-fluorescent bandor strip toward the top of the particle layer. For particle concentration (see paragraph 3.2.8) determination, this layerof dirt SHALL be carefully excluded from the total volume read. Dirt accumulation that exceeds 30-percent of thetotal volume of the particle requires replacement of the bath.
b. Fluorescence in the liquid may indicate bath breakdown (fluorescent pigmentation being stripped from the magneticparticles or fine magnetic particles remaining suspended in the vehicle). If the vehicle fluoresces excessively, placethe centrifuge tube in its stand with a horseshoe magnet in contact with the centrifuge tube and let sit on a vibrationfree surface for 1-hour for oil baths and 30-minutes for water baths. Illuminate the vehicle in the centrifuge tube withblack light in a darkened area. If the vehicle’s fluorescence is reduced or eliminated, the cause of the fluorescence isfine magnetic particles remaining suspended. If the level of fluorescence remains at the same level, the fluorescentpigmentation has been stripped from the magnetic particles and the bath requires replacement.
c. If it is determined the cause of the excessive suspension fluorescence is fine magnetic particles remaining in thevehicle, and they interfere with the results of the system effectiveness check (see paragraph 3.2); attempt to removethem from the holding tank’s magnetic particle bath. This can be done with magnets. Allow the magnetic particlebath in the holding tank to settle (not agitated) for 40-minutes. Place the magnets in the magnetic particle bath, takingcare not to place them so deep they will attract the particles that have settled out of suspension. The length of time ornumber of times that the magnets will have to be cleaned of particles and submerged is dependent upon theseriousness of the problem. The bath SHALL be able to pass the system effectiveness check (see paragraph 3.2),after the removal of as many suspended particles as possible or be replaced.
d. If a magnet was used to remove fine magnetic particles from suspension in the centrifuge tube, the suspensionSHALL be demagnetized prior to being poured back into the magnetic particle machine.
e. Clean the inside of the centrifuge tube to eliminate residual fluorescence remaining after each use.
3.2.10 Acidity Test. The acidity of a water bath SHALL be checked weekly (water baths only). The pH of the water bathSHALL be between 6 and 10. If the parts being inspected have a residual solvent film, more wetting agent is required so theparts’ surface will be completely wetted. Breaking of the bath into rivulets as it is applied over a part is an indication anadditional wetting agent is required or the part requires further cleaning.
3.2.11 Water Break Test. Conduct a water break test daily (water baths only) using a clean specimen or part having thesmoothest surface finish to be inspected. Flood the specimen with bath and examined once flooding has stopped. If a smoothcontinuous film of bath forms over the entire surface, sufficient wetting agent is present. Reference SHALL be made to themanufacturer’s recommendations for the correct quantity of wetting agent to be added.
3.2.12 Field Indicator Check. Performance requires a bar magnet or magnet with a north and south pole. Hold the in-usefield indicator next to one end of the magnet; a full-scale deflection in one direction should be observed. Move the indicatoraway from the magnet and note the return to ‘‘0’’ or centerline. Hold the indicator next to the opposite end of the bar magnet,note a full-scale deflection in the opposite end of the scale. Move the indicator away from the magnet and note the return tozero. If proper deflections are observed, then field indicator is serviceable.
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CHAPTER 4EDDY CURRENT INSPECTION
SECTION I EDDY CURRENT INSPECTION GENERAL PROCEDURE
4.1 EDDY CURRENT GENERAL PROCEDURE.
The following eddy current general practice is to be used in conjunction with part specific eddy current procedures or whenpart specific eddy current procedures do not exist. Section 4.1 defines the approved equipment and standards. Section 4.2provides guidance on scanning methods for general manual surface eddy current inspection including lift-off compensationwhen inspection components with nonconductive coatings applied. Section 4.3 provides detailed procedures for performingsurface and bolt hole inspection of ferromagnetic, weakly ferromagnetic and non ferromagnetic materials. Part specificprocedures SHALL take precedence over this general practice. For eddy current general theory refer to T.O. 33B-1-1.
4.1.1 Approved Equipment.
4.1.1.1 Eddy current instrument: Staveley Nortec 2000D, NSN 6635-01-455-9520 or equivalent.
4.1.1.2 Probe: Probe specifications SHALL be identified in the part specific procedure where a specific procedures exists.Probe substitutions will be necessary for conversion from legacy equipment (e.g., ED-520, HT-100) to the Nortec 2000Dseries. The following specifications are mandatory for all probe substitutions:
• Connectivity: Substitute probes shall connect directly to the Nortec 2000D without use of any adapter (e.g. P/N9522106.02). The Nortec 2000D probe cable connector is a type, 16-pin Lemo.
• Frequency: Substitute probes shall operate within the frequency range specified in the existing procedure or genericfrequency Table 4-3 when specific procedures are inadequate or do not exist.
• Coil Shielding: Manual surface probes and automated bolt hole probes shall be shielded unless otherwise specified.• Coil/Probe Size: Substitute probe coil/probe diameter shall be equal to the diameter specified in the existing procedure or
1/8th-inch for general surface inspection where specific procedures are inadequate or do not exist.• Configuration (length, drop, etc.): As directed by existing procedure or engineering directive. If no guidance is available
it is the Inspectors’ choice but must be sufficient to effectively complete the required inspection.• Coil Types for Surface Inspection: Unless otherwise specified by the existing procedure, an absolute/bridge or
absolute/reflection coil type arrangement is recommended. It is preferred that the reference coil be contained within theprobe housing. However, a 16- pin lemo cable that contains the reference coil will allow for use of absolute legacy typeprobes and is authorized if all other procedural requirements are met. Use of a cable manufactured by the probemanufacturer is preferred in order to achieve optimum coil impedance matching.
• Automated Fastener Hole Inspection: The probes shall be shielded, differential/reflection.• Approved Scanners: Nortec Spitfire, Minimite, and RA/19
NOTE
Each probe manufacturer may have their own definitions of probe coil arrangements. Inpectors unsure of thecoil/probe required in this procedure, consult with the manufacturer and/or ALC-NDI Engineering.
4.1.1.3 Standard: Unless otherwise identified in the part specific procedure, the Aluminum Air Force General Purpose EddyCurrent Standard, NSN 6635-01-092-5129 SHALL be used when inspecting aluminum parts. The Navy General PurposeEddy Current Standard meets all requirements and is acceptable for use when ever the Air Force Standard is called out. Neworders against NSN 6635-01-092-5129 will be filled with the Navy Standard. For inspection of other materials, use the AirForce or Navy General Purpose Eddy Current Standard configuration made of the same part material or use the alloysdefined in Table 4-1. For surface eddy current inspection, an acceptable alternate reference standard configuration is shownin (see Figure 4-2).
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Table 4-1. Reference Standard Materials
Part Material StandardAll Magnetic Steel Alloys 4340 Steel
Aluminum 7075-T6
Inconel Alloys Inconel 718
Stainless Steel PH13-8MO
Titanium Ti-6AL-4V
4.1.1.4 Teflon tape: It is required that teflon tape be applied to the contact surface of the probes to protect the probe tip fromexcessive wear and damage and to reduce probe noise. P/N 3M 5480 or equivalent, maximum thickness 0.005”.
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Figure 4-1. Eddy Current Reference Standard (Sheet 1 of 2)
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Figure 4-1. Eddy Current Reference Standard (Sheet 2)
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Figure 4-2. Alternate Surface Eddy Current Reference Standard
4.1.2 Eddy Current Scanning Techniques. Eddy current inspection procedures throughout this manual containinstructions that are specifically defined in the following paragraphs.
4.1.2.1 Manual Surface Inspection.
4.1.2.1.1 Coating Lift-off Compensation. For inspections performed over painted surfaces, liftoff caused by the paintthickness affects sensitivity and requires compensation during instrument standardization. To compensate for the increasedlift-off the appropriate thickness of nonconductive material (plastic shims, paper, etc.) SHALL be placed between the probeand standard during the standardization process unless otherwise specified by the part specific procedure. Determine theappropriate thickness of non-conductive shim by either using a dedicated non-conductive coating thickness gauge or usingthe procedure as follows:
WARNING
Coating thickness on the inspection surface greater than 0.010 inch (10 mils) thick will significantly reduceinspection sensitivity and can result in failure to detect cracks.
a. Set the instrument to ‘‘DEFAULT’’ settings by performing the steps as follows:
(1) Select the SETUP MENU.
(2) Select DEFAULT and press ENTER.
(3) Select LD DEFLT and press ENTER.
(4) Rotate the Smartknob until ‘‘CONFIRM’’ appears on the lower left side of the display and press ENTER.
b. Adjust the instrument settings to those defined in (Table 4-2).
c. Place the probe onto the surface to be inspected and NULL the instrument. Hold probe still until nulling is complete.The flying-dot should be located at 50% vertical and 50% horizontal screen position when nulling is complete.
d. Repeatedly place the probe on and off the inspection surface to generate a lift-off response. Adjust the phase ANGLEuntil a substantially horizontal, right-to-left lift-off signal is achieved.
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NOTE
The lift-off response should move off the left side of the display when the probe is lifted off the part. If it doesnot, check the inspection frequency, and if required, increase the GAIN until the lift-off signal moves off thescreen.
e. NULL the probe on the inspection surface. Hold the probe still until nulling is complete. The flying-dot should belocated at 50% Full Screen Height (FSH) and 50% Full Screen Width (FSW) when nulling is complete.
f. Without re-nulling, place the probe on the reference standard. Compare the horizontal position of the dot when theprobe is placed on the reference standard to the horizontal position of the dot when the probe is place on the surfaceto be inspected. If the flying dot horizontal positions are within three major horizontal divisions, 30% Full ScreenWidth (FSW), then lift-off compensation is not required. If the flying dot is greater than three major horizontaldivisions from the null point then proceed to the step g.
NOTE
The vertical position of the flying dot is not of concern as the reference standard and part under test may havedifferent conductivity values.
g. Insert nonconductive shims between the probe and reference standard until the flying-dot is between 50% and 70%FSW.
h. If the total shim thickness exceeds 0.010 inch (10 mils) then the coating SHALL be removed before the inspection isperformed.
i. If the total shim thickness is 0.010 inch (10 mils) or less then place shims, of the thickness established in step g, onthe reference standard for all phases of inspection standardization.
Table 4-2. Nortec 2000D Initial Settings for Determining Lift-off Compensation
Soft Key Description/Setting Soft Key Description/SettingMAIN MENU SETUP MENU
FREQ FREQUENCY 1/See Table 4-3 1 FREQ/SINGLE
FREQ FREQUENCY 2/OFF 4 PRB DR/MID
H-GAIN HORIZ. GAIN/60.0 dB N/A N/A
V-GAIN VERT. GAIN/60.0 dB N/A N/A
ANGLE ANGLE/70° N/A N/A
FILTER MENU N/A N/A
LPF LP FILTER/100 N/A N/A
HPF HP FILTER/OFF N/A N/A
CONT CONT NULL/OFF N/A N/A
DISPLAY MENU N/A N/A
SWEEP SWEEP/OFF N/A N/A
V-POS V-POS/50% N/A N/A
H-POS H-POS/50% N/A N/A
SCREEN MENU N/A N/A
PERSIST PERSIST/OFF N/A N/A
DISP ERS DISP ERASE/OFF N/A N/A
SWPERS OFF N/A N/A
DOT/BOX DOT N/A N/A
GRATICLE ON N/A N/A
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Table 4-3. Nortec 2000D Inspection Frequencies by Material
Material Alloy Frequency300 and 400 Series Stainless 500 kHz - 1 MHz
Magnetic Steels 200 - 500 KHz
Aluminum 200 - 500 kHz
Inconel Alloys 1 - 2 MHz
Nickel Alloys 1 - 2 MHz
Titanium 2 MHz
4.1.2.1.2 Manual Surface Eddy Current Inspection Scanning Techniques.
4.1.2.1.2.1 General Surface Inspection. Scan the surface to be inspected. Where the direction of cracking is known,scan perpendicular to the direction of cracking. Where the direction of cracking is not known, recommend scanning in the 0,45 and 90 degree directions. (see Figure 4-3) A scanning index shall be selected to ensure 100% coverage of the inspectionarea. An acceptable method for ensuring inspection coverage is to coat the inspection with nonaqueous developer and usingthe trail of probe to indicate coverage. Non-metallic, straight edge, templates, or edge guides should be used to guide the testprobe along edges to stabilize the edge effect on the probe.
Figure 4-3. Required Scanning Directions
4.1.2.1.2.2 Surface Inspection Around Flush Fasteners. Scan around the entire circumference of the fastener. Positionthe probe’s coil immediately outside the edge of the fastener head. Maintaining a constant yet minimal distance is required to
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maintain sensitivity to cracks propagating from the fastener hole. A circle template made of non-conductive material shouldbe used if part geometry allows. (see Figure 4-4)
NOTE
Special care must be taken by the inspector to ensure that the probe position is perpendicular to the inspectionsurface and the template is centered to avoid lift-off and edge effects during scanning. The ability to hold theprobe steady and perpendicular during scanning depends on attentiveness, competence, and experience of theinspector.
Figure 4-4. Scanning Around Fastener with Flush Heads
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4.1.2.1.2.3 Surface Inspection Around Protruding Fastener Heads. Scan around the entire circumference of thefastener, positioning the probe’s coil adjacent yet in contact with the side of the fastener. Using the fastener as a guide,maintain a positive pressure against the fastener head for detection of cracks protruding from under the fastener head. (seeFigure 4-5) Re-nulling may be required on the component being inspected due to minor conductivity variations between thepart and standard.
Figure 4-5. Scanning Around Fastener with Protruding Heads
4.1.2.1.2.4 Surface Inspection of Radii. When the direction of cracking is known, scan perpendicular to the direction ofcracking. If the cracking direction is not known, scan the radius in both the longitudinal and transverse direction whilemaintaining the coil perpendicular to the inspection surface. (see Figure 4-6) A scanning index in both the longitudinal andtransverse directions shall be selected to ensure complete coverage of the area to be inspected, index spacing shall be selectedto ensure 100% coverage of the inspection area. Index spacing at a maximum 1/2 probe diameter is recommended.
Figure 4-6. Scanning Radii
4.1.2.1.2.5 Scanning Between Fasteners. Scanning between fasteners is identical to scanning around fasteners,however, if the fasteners are too close to allow effective signal interpretation, scan around the perimeter of the fasteners.
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4.1.2.1.2.6 Scanning Edges. Scan part or panel edges using shielded surface probes to reduce edge effect. Nonconduc-tive straight edge or edge guides should be used when part geometry allows. Null with the probe on the edge to minimizeedge effect.
4.1.3 General Eddy Current Inspection Procedures.
4.1.3.1 General Information. These procedures prescribe general set-up, calibration and inspection requirements for eddycurrent instrument standardization and inspection. These instructions are to be used in conjunction with the part specificprocedures when they exist. The part specific procedures take priority. If the part specific procedure does not provideguidance or does not exist, this procedure can be used as a stand-alone procedure by an experienced task certified technicianfor general surface scan requirements. If conditions exist that are not adequately covered contact the appropriate ALC NDIManager for specific guidance.
4.1.3.2 Part Preparation.
4.1.3.2.1 When conducting eddy current inspections near fuel tank areas, the aircraft must be defueled and purged. Followthe aircraft specific tech data for defuel and purge instructions.
CAUTION
Surfaces shall be clear of any residue which might interfere with inspection or damage inspection equipment.
4.1.3.2.2 Nonconductive coatings (i.e., paint) in excess of 0.010 inch thick or having wide variation in thickness shall beremoved from the inspection area prior to inspection. All sealant SHALL be removed.
WARNING
Solvents are hazardous material. Handle in compliance with applicable Material Safety Data Sheet (MSDS) andlocally approved instructions. Check the weapon specific tech data for approved solvents.
4.1.3.2.3 Remove soils, dirt, grease and other debris which might interfere with inspection or damage inspection equipment.If necessary, clean area with approved solvent.
4.1.3.3 Equipment Preparation.
a. Connect eddy current unit to power source if necessary.
b. Where possible, all probe coils should be protected by a layer of tape (Teflon or equivalent) with a maximumthickness of 5 mils (0.005 inch).
c. The part to be inspected, calibration standard, inspection unit and probe must be at ambient temperature to assure thatvalid test data is obtained.
d. Periodically during the inspection and following the completion of all inspections, rescan the calibration standard toensure the instrument remains within calibration limits. The time between standardizations SHALL NOT exceed 10-minutes. If the original sensitivity requirements are not met following any reference standard rescan, all inspectionsaccomplished since the last successful scan SHALL be reaccomplished.
4.1.3.4 General Procedure for Manual Surface Eddy Current Inspection of Aluminum, Nonferromagnetic Parts, and WeaklyFerromagnetic Parts Using the Staveley Nortec 2000D.
4.1.3.4.1 Equipment Setup.
4.1.3.4.1.1 Establishing Lift-Off Compensation
a. Attach the probe and cable to the instrument as required. Apply Teflon tape to the probe as required.
b. If the part to be inspected is painted, determine the required lift-off compensation to use during standardization byfollowing the procedure in paragraph 4.1.2.1.1. If the part is not painted proceed to paragraph 4.1.3.4.1.2.
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4.1.3.4.1.2 Stored Setups
a. Recall the program and verify the set-up parameters match those listed in Table 4-4.
b. Proceed to paragraph 4.1.3.4.2.
4.1.3.4.1.3 If the setup has not been stored in instrument memory, proceed as follows:
a. Set the instrument to ‘‘DEFAULT’’ settings by performing the steps as follows:
(1) Select the SETUP MENU.
(2) Select DEFAULT and press ENTER.
(3) Select LD DEFLT and press ENTER.
(4) Rotate the Smartknob until ‘‘CONFIRM’’ appears on the lower left side of the display and press ENTER.
b. Adjust equipment settings per Table 4-4. Minor adjustments to these settings are allowable as necessary to achieveoptimum signal characteristics.
c. Set FREQUENCY per specific procedure requirements. If no frequency is specified, use the appropriate frequency asdefined in Table 4-5.
NOTE
Teflon tape may need to be replaced periodically. Always confirm unit standardization responses to the referencestandard notches after the tape is replaced. It is critical to ensure that tape is applied correctly and used in all stepsof this procedure especially when inspecting the part and the instrument is displaying corner noise that can beconfused with crack-like indications.
Table 4-4. Nortec 2000D Settings for Surface Scan of Aluminum
Soft Key Description/Setting Soft Key Description/SettingMAIN MENU SETUP MENU
FREQ FREQUENCY 1/See 1 FREQ/SINGLETable 4-5
FREQ FREQUENCY 2/OFF 4 PRB DR/MID
H-GAIN HORIZ. GAIN/60.0 dB N/A N/A
V-GAIN VERT. GAIN/75.0 dB N/A N/A
ANGLE ANGLE/70° N/A N/A
FILTER MENU N/A N/A
LPF LP FILTER/100 N/A N/A
HPF HP FILTER/OFF N/A N/A
CONT CONT NULL/OFF N/A N/A
DISPLAY MENU N/A N/A
SWEEP SWEEP/OFF N/A N/A
V-POS V-POS/10% N/A N/A
H-POS H-POS/80% N/A N/A
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Table 4-4. Nortec 2000D Settings for Surface Scan of Aluminum - Continued
Soft Key Description/Setting Soft Key Description/SettingSCREEN MENU N/A N/A
PERSIST PERSIST/OFF N/A N/A
DISP ERS DISP ERASE/OFF N/A N/A
GRATICLE ON N/A N/A
DOT/BOX DOT N/A N/A
Table 4-5. Nortec 2000D Inspection Frequencies
Material Alloy FrequencyAluminum 200 kHz
Titanium 2 MHz
Inconel Alloys 1 - 2 MHz
Nickel Alloys 1 - 2 MHz
300 and 400 Series Stainless 500 kHz - 1 MHz
Magnetic Steels 200 - 500 kHZ
4.1.3.4.2 Standardization for Surface Inspection.
NOTE
If nonconductive shims are required for lift-off compensation then the shims shall be placed on the referencestandard during phase adjustment, nulling and establishing sensitivity.
a. Allow the part, reference standard, probe and eddy-current instrument to reach ambient temperature to ensure valid,repeatable inspection results.
b. Place probe on the calibration standard surface so the coil is a minimum of twice the probe diameter from all notchesand edges. Press the NULL key. Hold the probe still until ‘‘Nulling’’ is complete.
c. Repeatedly place the probe on and off the reference standard, at least two probe diameters away from all notches andedges, to generate a lift-off response. Adjust the phase ANGLE until a substantially horizontal, right-to-left, lift-offsignal is achieved.
d. With the appropriate thickness of nonconductive shims placed on the reference standard (if required), place probe onthe standard surface so the coil is a minimum of twice the probe diameter from all notches and edges.
e. Press the NULL key. Hold the probe still until nulling is complete.
f. While repeatedly scanning across the 0.020 inch deep notch adjust the GAIN until a signal trace of 80% Full ScreenHeight (FSH) deflection is obtained from the notch (see Figure 4-7). Decrease the H-GAIN if the notch signal goesoff the left side of the display.
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Figure 4-7. Signal Response from 0.020 inch Deep Notch in Aluminum
4.1.3.4.3 Sensitivity Check.
NOTE
If the GAIN maximum limit is reached without achieving the specified deflection, check the lift-off phase angleto ensure it is horizontal. Adjust ANGLE if necessary and reaccomplish standardization. If the required deflectionstill cannot be achieved change the Probe Drive (PRB DR) to HIGH and repeat standardization. If the requireddeflection still cannot be achieved or the noise is excessive change probe or cable as required.
The step is required when using the Air Force General Purpose Reference Standard. With the appropriate thickness ofnonconductive shim in place, scan over the 0.005 inch deep, 0.010 inch deep and 0.020 inch deep reference notches. Thethree responses should appear similar to (see Figure 4-8). The response from the 0.005 inch deep notch should produce aminimum 5% FSH vertical response and should be clearly discernible from the baseline noise. If these responses are notachieved, check the instrument set-up and repeat the standardization procedure. If after restandardization this sensitivity stillcannot be achieved, select a different probe and repeat the standardization.
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Figure 4-8. Responses from 0.005, 0.010, and 0.020 inch Deep Notches (Aluminum) with AcceptableSignal-to-Noise
4.1.3.4.4 Inspection.
a. Place the probe on the part to be inspected. The probe coil should be at least two probe diameters away from thenearest edge. Ensure good contact between the coil and part.
b. Press the NULL key and hold the probe still until nulling is complete. Periodic nulling may be necessary duringinspection to maintain the baseline at 10% FSH and 80% FSW.
NOTE
The screen trace or ‘‘flying dot’’ can drift up to 2 major divisions in 15 minutes or less when the Nortec 2000D isinitially powered up. Recommend a warm-up period of at least 10 minutes prior to inspection.
c. Scan the inspection area. Use the same scan speed as used during calibration. If numerous scan lines are required,index 1/2 the probe diameter between scan lines to ensure full coverage, unless otherwise specified. Watch forindications on the display similar to those obtained during calibration. If specific scan instructions are not provideduse the appropriate scan technique defined in (see paragraph 4.1.2.1.2).
4.1.3.4.5 Evaluation, Marking, and Reporting.
4.1.3.4.5.1 Any vertical signal trace that is distinguishable (separated) from the background noise and not caused by lift-offor part geometry shall warrant further examination and rescanning of the area of interest.
a. Mark all repeatable crack-like indications equal to or greater than 10% vertical deflection (see Figure 4-8) above thebaseline/null point. These areas require evaluation with the part specific back-up procedure. If the part specificprocedure does not specify a backup procedure (see paragraph 4.1.3.4.7).
b. Any repeatable crack-like indication equal to or greater than 10% FSH above the lift-off baseline that has beenverified by the appropriate backup method shall be marked and documented IAW the appropriate AF Instruction andlocal directives. Enter the percent vertical screen deflection and identify the defect location in the inspection record.
4.1.3.4.6 Post-Inspection Standardization. Place the probe on the standard. Ensure firm contact is maintained betweenthe coil, shim (if used), tape (if used), and standard.
a. Ensure the coil is a minimum of two probe diameters from the notch and the nearest edge.
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b. Press the NULL key. Hold the probe on the standard until nulling is complete.
c. With the appropriate thickness of shims in place, repeatedly scan across the 0.020 inch deep reference notch. Thedeflection above the baseline must be between 70% and 90% FSH. If the deflection is below 70% FSH then allinspections performed since the last standardization must be repeated. If the deflection is above 90% then all suspectindications identified since the last standardization must be reevaluated.
4.1.3.4.7 Backup Procedure. If the part specific procedure does not specify a backup procedure it is recommended thatthe indication be verified by a second inspector. Repeat standardization and have a second inspector verify the indication. Ifavailable, separate equipment and probes should also be used for each independent inspection. If the defect indication is notconfirmed, proceed to system securing.
4.1.3.5 General Procedure for Manual Surface Eddy Current Inspection of Steel Parts Using the Staveley Nortec2000D.
4.1.3.5.1 Equipment Preparation.
4.1.3.5.1.1 Establishing Lift-off Compensation.
a. Attach the probe and cable as required. (See paragraph 4.1 for probe requirements). Apply Teflon tape to the probe asrequired.
b. If the part to be inspected is painted, determine the required lift-off compensation to use during standardization byfollowing the procedure in (see paragraph 4.1.2.1.1). If the part is not painted proceed to (see paragraph 4.1.3.5.1.2).
4.1.3.5.1.2 Stored Setups.
a. Recall the program and verify the set-up parameters match those listed in (see Table 4-6).
b. Proceed to paragraph 4.1.3.5.2.
4.1.3.5.1.3 If the setup has not been stored in instrument memory, proceed as follows:
a. Set the instrument to ‘‘DEFAULT’’ settings. (Refer to the equipment operator’s manual for specific instructions onestablishing default settings).
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b. Adjust equipment settings per (see Table 4-6). Minor adjustments to these settings are allowable as necessary toachieve optimum signal characteristics.
c. Set FREQUENCY per specific procedure requirements. If no frequency is specified, use the appropriate frequency asdefined in (see Table 4-6).
NOTE
Teflon tape may need to be replaced periodically. Always confirm unit standardization responses to the referencestandard notches after the tape is replaced. It is critical to ensure that tape is applied correctly and used in all stepsof this procedure especially when inspecting the part and the instrument is displaying corner noise that can beconfused with crack-like indications.
Table 4-6. Settings Prior to Calibration for Surface Scanning of Steel Parts
Soft Key Description/Setting Soft Key Description/SettingMAIN MENU SETUP MENU
FREQ FREQUENCY 1/200Khz to 1 FREQ/SINGLE500Khz
FREQ FREQUENCY 2/OFF 4 PRB DRV / MID
H-GAIN HORIZ. GAIN/50.0 dB N/A N/A
V-GAIN VERT. GAIN/70.00 dB N/A N/A
ANGLE ANGLE/0° N/A N/A
FILTER MENU N/A N/A
LPF LP FILTER/30 N/A N/A
HPF HP FILTER/0 N/A N/A
CONT CONT NULL/OFF N/A N/A
DISPLAY MENU N/A N/A
SWEEP SWEEP/OFF N/A N/A
V-POS V-POS/10% N/A N/A
H-POS H-POS/50% N/A N/A
SCREEN MENU N/A N/A
PERSIST PERSIST/OFF N/A N/A
DISP ERS DISP ERASE/5.0 s N/A N/A
GRATICULE ON N/A N/A
DOT/BOX DOT N/A N/A
4.1.3.5.2 Standardization for Surface Inspection of Magnetic Steel.
NOTE
If a nonconductive shims are required for lift-off compensation then the shims shall be placed on the referencestandard during phase adjustment, nulling and establishing sensitivity. If it is difficult at this point to obtain astable liftoff signal, frequent nulling is required. The lift-off signal will not be completely stable.
a. Allow the part, reference standard, probe and eddy current instrument to reach ambient temperature to ensure valid,repeatable inspection results.
b. Place probe on the calibration standard surface so the coil is a minimum of twice the probe diameter from all notchesand edges. Press the NULL key. Hold the probe still until ‘‘Nulling’’ is complete.
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c. Repeatedly place the probe on and off the reference standard, at least two probe diameters away from all EDMnotches and edges, to generate a lift-off response. Adjust the phase ANGLE until a substantially horizontal, right-to-left, lift-off signal is achieved.
NOTE
• Variations in magnetic permeability may result in excessive noise during standardization. If this isencountered demagnetization of the part may aid in reducing signal noise. Refer to Chapter 3, paragraph3.1.7.3 Demagnetization Using Portable Yokes for guidance.
• If excessive noise is encountered and demagnetization has not reduced the noise to an acceptable level ordemagnetization is not possible, it is permissible to utilize High Pass filtering to stabilize the signal. Amaximum High Pass filter set at 2 is permitted.
d. With the appropriate thickness of nonconductive shims placed on the reference standard (if required), place probe onthe standard surface so the coil is a minimum of twice the probe diameter from all notches and edges.
(1) Press the NULL key. Hold the probe still until nulling is complete.
(2) While repeatedly scanning across the 0.020” deep notch adjust the GAIN until an 80% vertical response isobtained from the notch. The horizontal null position is located at 50% to ensure notch response remains onscreen. (see Figure 4-10).
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Figure 4-10. 80% FSH Signal from a 0.020 Inch Deep Notch
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CAUTION
The HP filter SHALL NOT exceed 2 Hz and the LP filter shall not be less than 30 Hz or unacceptable signalsuppression may result.
e. If High Pass filtering is required to stabilize the signal, set the HP FILTER to ‘‘2’’ then perform the following steps:
NOTE
The use of HP filtration will result in a positive and negative (figure eight) signal presentation on the instrumentscreen.
(1) From the DISPLAY MENU, set the V-POS (vertical position) to 50%.
(2) With the appropriate thickness of nonconductive shims placed on the reference standard (if required), place probeon the standard surface so the coil is a minimum of twice the probe diameter from all notches and edges.
(3) Press the NULL key. Hold the probe still until nulling is complete.
(4) While repeatedly scanning across the 0.020” deep notch at a rate of 0.5-1.0 inches per second, adjust the GAINuntil an 80% vertical Peak-to-Peak (PTP) response is obtained from the notch. (see Figure 4-11).
Figure 4-11. Impedance Plane Display of 80% Ptp Signal from the 0.020 Inch Deep Notch
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4.1.3.5.3 Sensitivity Check.
CAUTION
Scanning speed is critical when using HPF. HPF is necessary to stabilize the signal on magnetic materials.However, HPF is very sensitive to inadequate scanning speed, which can suppress crack signals. Ensure a 0.5-1.0inch per second scanning speed is maintained during calibration and inspection to prevent suppressing notch andcrack signals. It is helpful to practice the scanning speed during calibration.
With the appropriate thickness of nonconductive shim in place, scan over the 0.005 inch deep reference notch. The responsefrom the notch should be clearly distinguishable from the baseline noise and produce a minimum 20% FSH response (20%PTP with High Pass filtering). (See Figure 4-12 and Figure 4-13) If this response is not achieved, check the instrument set-upand repeat the standardization procedure. If after restandardization this sensitivity still cannot be achieved, select a differentprobe and repeat the standardization.
Figure 4-12. Impedance Plane Response (without High Pass Filter) from the 0.005 Inch Notch (4340 Steel) withAcceptable Signal-To-Noise
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Figure 4-13. Impedance Plane Response (with High Pass Filter) from the 0.005 Inch Notch (4340 Steel) withAcceptable Signal-To-Noise
4.1.3.5.4 Inspection.
a. Place the probe on the part to be inspected. The probe coil should be at least two probe diameters away from thenearest edge. Ensure good contact between the coil and part.
b. Scan the inspection area. Use a similar scan speed as used during calibration. If numerous scan lines are required,index 1/2 the probe coil diameter between scan lines to ensure full coverage. Watch for indications on the displaysimilar to those obtained during calibration. Ensure a scanning speed of 0.5-1.0 per second is maintained. If specificscan instructions are not provided use the appropriate scan technique defined in (see paragraph 4.1.2.1.2).
c. During the inspection (10-minute intervals) and following the completion of all inspections, rescan the calibrationstandard to ensure the instrument remains within calibration limits. With the appropriate thickness of shims in place,repeatedly scan across the 0.020 inch deep reference notch. The deflection above the baseline must be between 70%and 90% FSH (70% and 90% PTP with HP filter). If the deflection is below 70% FSH then all inspections performedsince the last standardization must be repeated. If the deflection is above 90% then all suspect indications identifiedsince the last standardization must be reevaluated.
4.1.3.5.5 Evaluation, Marking, and Reporting.
a. With an approved marking pencil, mark all repeatable crack-like indications distinguishable (separated) frombackground noise. (see Figure 4-12 or Figure 4-13)
b. Evaluate all marked indications with the part specific back-up procedure. If the part specific procedure does notspecify a back-up procedure (see paragraph 4.1.3.5.7).
c. Report any repeatable crack-like indication obtained during the back-up procedure inspection that exceed two timesthe background noise level amplitude or 20% deflection if the noise is near zero. Enter the percent screen deflectionand defect location in the inspection record.
4.1.3.5.6 Post-Inspection Standardization.
a. Place the probe on the standard. Ensure firm contact is maintained between the coil, shim (if used), tape (if used),and standard.
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b. Ensure the coil is a minimum of two probe diameters from the notch and the nearest edge.
c. Press the NULL key. Hold the probe on the standard until nulling is complete.
d. With the appropriate thickness of shims in place, repeatedly scan across the 0.020 inch deep reference notch. Thedeflection above the baseline must be between 70% and 90% FSH. If the deflection is below 70% FSH then allinspections performed since the last standardization must be repeated. If the deflection is above 90% then all suspectindications identified since the last standardization must be reevaluated.
4.1.3.5.7 Backup Procedure. If the part specific procedure does not specify a backup procedure, evaluate all markedindications as follows: Recalibrate per (see paragraph 4.1.3.5.2) and perform a redundant inspection of all areas exhibitingsuspect indications. A redundant inspection is defined as an inspection performed by a second individual. Each independentinspection shall include a separate setup and calibration of the equipment. If available, separate equipment and probes shouldalso be used for each independent inspection. If no defect is suspected or confirmed, proceed to system securing.
4.1.3.6 General Procedure for Rotary Fastener Hole Eddy Current Inspection of Aluminum, Non-ferrous andWeakly Ferromagnetic Parts Using the Staveley Nortec 2000D/2000D+ with a MiniMite, Spitfire and RA/19Scanners.
NOTE
This procedure does not apply to titanium alloys. Refer to Section 4.1.8 for specific procedures to be used forrotary fastener hole inspection of titanium alloys.
4.1.3.6.1 Equipment Preparation.
a. Ensure part, reference standard and probe are at ambient temperature to ensure valid, repeatable inspection results.
b. Select the probe for best fit in the hole to be inspected. When inserted into the hole, the probe should be in intimatecontact with the inner diameter but still rotate easily.
c. Application of Teflon tape (5 mils maximum thickness) to the probe is required to reduce probe wear and signalnoise caused by scanning rough surfaces and hole edges. Wrap the tape over the coil and through the probe split. Donot wrap the tape completely around the probe split.
NOTE
The Teflon tape may need to be replaced periodically. Always confirm unit standardization responses to thereference standard notches after the tape is replaced. It is critical to ensure that tape is applied correctly and usedin all steps of this procedure.
d. Connect the probe to the scanner and connect the scanner cable to the scanner and eddycurrent unit.
4.1.3.6.1.1 Stored Setups.
a. Recall the program. Verify the settings match those listed in Table 4-7.
b. Proceed to paragraph 4.1.3.6.2.
4.1.3.6.1.2 If the setup has not been stored in instrument memory, proceed as follows:
a. Set the instrument to ‘‘DEFAULT’’ settings by performing the steps as follows:
(1) Select the SETUP MENU.
(2) Select DEFAULT and press ENTER.
(3) Select LD DEFLT and press ENTER.
(4) Rotate the Smartknob until ‘‘CONFIRM’’ appears on the lower left side of the display and press ENTER.
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b. Adjust equipment settings per Table 4-7. Minor adjustment to these settings are allowed as necessary to achieveoptimum signal characteristics.
c. Set the FREQUENCY in accordance with the part specific procedure. If no frequency is specified, use the probefrequency as specified in Table 4-8 for the specific material to be inspected. For all other materials contact the AirLogistics Center NDI Manager.
d. Note the hole diameter to be inspected and adjust the Low Pass Filter (LP FILTER) and High Pass Filter (HPFILTER) to the values shown in Table 4-9.
Soft Key Description/Setting Soft Key Description/SettingMAIN MENU SETUP MENU
FREQ FREQUENCY 1/(See 1 FREQ/SINGLETable 4-8)
FREQ FREQUENCY 2/OFF 4 PRB DRV/MID
H-GAIN HORIZ. GAIN/65.0 dB
V-GAIN VERT. GAIN/65.00 dB
ANGLE ANGLE/0°FILTER MENU SPECIAL MENU
CONT CONT NULL/OFF RPM SCAN RPM/1500
DISPLAY MENU SYNC ANG 0
SWEEP SWEEP/OFF
V-POS V-POS/50%
H-POS H-POS/50%
SCREEN MENU
PERSIST PERSIST/OFF
DISP ERS DISP ERASE/0.2 s
GRATICULE ON
DOT/BOX DOT
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Table 4-8. Frequency Settings Fastener Hole Scanning of Aluminum, Non-Ferrous Alloys, and WeaklyFerromagnetic Alloys
Material Alloy FrequencyAluminum 200 KHz - 500 KHz
300 and 400 Series Stainless 500 KHz - 1 MHz
Magnetic Steel 200 - 500 KHz
Nickel Alloys 1 - 2 MHz
Magnesium 500 KHz
Inconel Alloys 1 MHz - 2 MHz
NOTE
In cases where a frequency range is provided, high frequencies will provide more sensitivity to cracks, while lowfrequencies will produce lower noise levels during inspection.
NOTE: Filters may be adjusted +/-50Hz to improve symmetry of notch response.
4.1.3.6.2 Standardization for Rotary Fastener Hole Inspection of Aluminum, Selected Nonferromagnetic andWeakly Ferromagnetic Parts.
NOTE
This procedure was developed using a differential/reflection, fastener hole probe, 100KHz- 2MHz. Thedifferential/reflection coil design will portray a negative and positive (figure eight) signal response on theimpedance plane display of the instrument.
a. With the scanner turned off, insert the probe into the appropriate size hole in the reference standard. The probeshould fit snug in the hole without binding. Verify the coil is 90° away from the corner notch and away from holeedges and press NULL. Hold the probe still until nulling is complete.
b. Remove the probe from the hole.
c. With the SWEEP turned OFF, hold the scanner so that the probe is parallel to the reference standard. Place the coil incontact with a flat area of the reference standard at least 1/4 inch away from any edge or notch. Turn the scanner onwhile the coil makes contact with the reference standard to generate a liftoff signal.
d. Adjust the phase rotation by pressing the ANGLE key and rotating the Smartknob to achieve a substantiallyhorizontal liftoff signal. See Figure 4-14.
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Figure 4-14. Typical Lift-off Response with Phase Adjusted Correctly
e. Turn the scanner on and insert the rotating probe into the appropriate hole size in the reference standard and locatethe 0.030 inch corner notch located at the interface of the first and second layers. Maximize the reference notchsignal.
f. Adjust the Vertical GAIN (V-GAIN) and Horizontal GAIN (H-GAIN) independently to place the entire notchresponse on the screen at a 45 degree angle (1:1 slope), spanning 80% FSH and 80% FSW. (See Figure 4-15). Notchpeak-to-peak response at 80% FSH and 80% FSW (45 degrees). The lift-off may not be visible.
g. Return to the DISPLAY menu. Press the SWEEP key twice to enter the ‘‘SWEEP EXTRN’’ mode. The instrument isnow in sweep mode.
h. If the sweep signal is centered at 50% FSH, proceed to step k.
i. With the scanner turned off, insert the probe into the appropriate size hole in the reference standard. The probeshould fit snug in the hole without binding. Verify the coil is 90° away from the corner notch and away from holeedges and press NULL. Hold the probe still until nulling is complete.
j. Remove the probe from the hole.
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Figure 4-15. Impedance Plane Display
Figure 4-16. Properly Calibrated Sweep Display
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Figure 4-17. Acceptable Noise Level from Clean Hole
Figure 4-18. 30% PTP Signal Requires Evaluation
k. Turn the scanner on and reinsert into the reference standard hole. Maximize the signal from the 0.030 inch interfacenotch. Push the GAIN button and adjust the GAIN (both horizontal and vertical gains will be adjustedsimultaneously) as necessary to obtain an 80% Peak-to-Peak (PTP) signal from the notch. The notch signal shouldappear narrow and nearly symmetric above and below the baseline as shown in Figure 4-16.
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l. Ensure the signal response from good areas of the hole is relatively smooth across the sweep display. Noise level ingood areas shall be no more than 10% negative or positive from the baseline. See Figure 4-17.
m. If the noise level is less than 10% from the baseline or less, proceed to paragraph 4.1.3.6.3
n. If noise signals greater than 10% from the baseline appear, repeat standardization procedure. If the noise levelremains excessive after repeated standardization, perform the following steps:
(1) Recheck probe fit.
(2) Remove probe from scanner and check for inherent scanner and cable noise.
(3) Replace the probe, cable or scanner that is causing the noise and repeat standardization per section 4.1.3.6.2.
4.1.3.6.3 Determining Maximum Index Speed.
a. Insert the probe into the appropriate hole in the reference standard and locate the 0.030 inch interface notch at theinterface of the first and second layers.
b. Monitor the display while moving the probe in and out over the interface notch.
NOTE
The maximum speed that the probe can be moved through the hole is the rate of probe travel that alwaysidentifies the notch and does not cause a reduction of the peak in signal height from 80% FSH PTP.
c. Gradually increase the probe travel speed until the peak height of the notch response begins to decrease below 80%FSH PTP. This is the maximum probe travel speed.
4.1.3.6.4 Identifying the Scanner Zero or Scan Origin. Establish the scanner zero or scan origin by using one of thefollowing methods:
4.1.3.6.4.1 Method A: Setting the Scanner Sync Zero Position.
a. Visually locate the notch on the top surface of the reference standard.
b. Insert the probe into the appropriate hole in the reference standard and rotate the scanner housing until the red LEDalarm indicator on the side of the scanner housing is pointed at the physical position of the notch on the standard asshown in Figure 4-19 and Figure 4-20.
c. Turn on the scanner and adjust the SYNC ANGLE in the SPECIAL menu screen until the trailing edge of the notchindication is displayed on the left side of the screen with the leading edge of the indication positioned on the rightside of the screen (split-signal) as shown in Figure 4-19.
NOTE
An acceptable alternate approach is to place the notch signal in the center of the screen and use this position asthe scanner zero.
4.1.3.6.4.2 Method B: Locating Sweep Crossing for Scanner/Notch Alignment.
a. Visually locate the notch on the top surface of the reference standard.
b. Insert the rotating probe into the appropriate hole in the reference standard until the maximum signal is obtainedfrom the notch.
c. Rotate the scanner until the top, center of the scanner is in line with the notch.
d. Note the point at the center of the notch signal crosses the sweep baseline. This is scanner zero as shown inFigure 4-21.
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e. Locate crack position by rotating the scanner until crack signal appears at the scanner zero location. Crack will be inline with the top, center of the scanner.
Figure 4-19. Establishing Sync Zero Position of the Nortec Spitfire Scanner
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Figure 4-20. Establishing Sync Zero Position of the Nortec Minimite Scanner
Figure 4-21. Establishing Top, Center Scanner Zero Position (Method B)
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4.1.3.6.5 Alarm Setting
4.1.3.6.5.1 Nortec 2000D.
a. With the display in the sweep mode (SWEEP/EXTRN), press DISP/ALARM to set the sweep display ALARM tothe settings in Table 4-10. See Figure 4-22.
Table 4-10. Sweep Display Alarm Gate Settings
TYPE SWEEP
+/-/OFF NEGATIVE
TOP 65.0%
BOTTOM 35.0%
Figure 4-22. Sweep Display with Alarm Gates
b. Return to the DISPLAY menu. Press the SWEEP key to turn the display to SWEEP/OFF. The display should now bein the impedance plane mode. Set the impedance plane display ALARM to settings in Table 4-11. See Figure 4-23.
Figure 4-23. Impedance Plane Display with Alarm Gates
4.1.3.6.5.2 Nortec 2000D+.
a. Return to the DISPLAY menu. Press the SWEEP key to turn the display mode to EXT SPLT mode. The displayshould now be in the split screen mode (sweep display on the left and impedance plane display on the right. SetALARM to settings in Table 4-10 (left side of screen). See Figure 4-24, left side.
NOTE
The Nortec 2000D+ will only allow alarm settings on the sweep half of the display in the split screen mode.
b. With a grease pencil, mark two vertical lines on the impedance plane half of the display (right side), one at 35% FSWand the second at 65% FSW. The lines must pass through the 50% FSH baseline. See Figure 4-24, right side. Thisdefines the limits for lift-off induced noise.
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Figure 4-24. Split Screen Display with Sweep Display Alarm Gates and Impedance Plane Display Lift-off Limits
4.1.3.6.6 Inspection.
NOTE
• Standardization should be verified at least once every 10 minutes or every 30 holes, whichever comes first. Ifthe notch signal does not provide 70-90% vertical PTP deflection repeat the standardization IAW paragraph4.1.3.6.2 and repeat the inspection.
• All holes SHOULD be cleaned with a tool such as a flex hone prior to inspection.
a. Visually verify the hole surface condition will not damage the probe during inspection and is void of any foreignmaterial (e.g. grease, sealant, metal shavings).
b. Enter data available to this point on an inspection record, if required. Enter additional data in record as it is obtained.
c. With the scanner off, check probe fit in the holes to be inspected. The fit should approximate the fit in the referencestandard. Remove the probe from the hole.
4.1.3.6.6.1 Inspection with the Nortec 2000D.
a. With the SWEEP mode OFF (impedance plane display), turn on the scanner and reinsert the probe in the hole.Inspect by slowly pushing the probe through the entire hole then pulling the probe slowly back through the hole. Theprobe must be kept perpendicular to the part surface during scanning. Repeat a minimum of twice for each hole to beinspected.
b. The hole is considered uninspectable if the general surface condition causes noise signals greater than 10% above orbelow the baseline on the sweep display. (See Figure 4-26). Additional hole preparation and cleaning may berequired prior to reinspection.
c. Indications on the impedance plane appearing near the same phase angle as the calibration notch (upper left or lowerright quadrant of display) and exceed 30% FSH from the baseline (see Figure 4-25) proceed to paragraph 4.1.3.6.7.For all other indications exceeding the inspection gates, proceed to paragraph 4.1.3.6.10 for disposition.
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Figure 4-25. Example of Crack Indication in Hole with Noise Level Greater than 30%Fsw
Figure 4-26. Example of Excessive Noise in the Sweep Mode (Left) and in the Impedance Plane Mode (Right)
4.1.3.6.6.2 Inspection with the Nortec 2000D+.
a. Return to the DISPLAY menu. Press the SWEEP key to turn the display to EXT SPLT mode. The display shouldnow be in the split screen mode (sweep display on the left and impedance plane display on the right.
b. Turn on the scanner and reinsert the probe in the hole. Inspect by slowly pushing the probe through the entire holethen pulling the probe slowly back through the hole. The probe must be kept perpendicular to the part surface duringscanning.
c. The hole is considered uninspectable if the general surface condition causes noise signals greater than 10% above orbelow the baseline on the sweep display (see Figure 4-27). Hole preparation and cleaning may be required prior toreinspection.
d. Indications on the impedance plane appearing near the same phase angle as the calibration notch and exceed 30%FSH from the baseline (see Figure 4-24) proceed to paragraph 4.1.3.6.7. For all other indications which exceed theinspection gates, proceed to 4.1.3.6.10 for disposition.
4.1.3.6.7 Indication Evaluation, Marking, and Recording.
a. Any repeatable indication above the background noise, exhibits a vertical response greater than 30% vertical PTP inthe sweep display (Figure 4-25) and exhibits a phase response similar to the reference notch when viewed in the
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impedance plane display (Figure 4-25), shall be considered a possible crack. This SHALL be considered a crack evenwith lift-off noise greater than 30% FSW.
b. Mark all repeatable crack indications with an approved marker per paragraph 4.1.3.6.8 and paragraph 4.1.3.6.9.
c. Verify the instrument standardization after the detection of a crack indication by performing a sensitivity check of theunit as follows:
(1) Insert the probe into the appropriate reference standard hole and maximize the signal response received from thereference notch.
(2) The notch signal should exhibit a vertical signal within 70% - 90% PTP. If it does then the defect indicationSHALL be considered valid and recorded.
(3) If the notch signal does not provide the required 70% - 90% vertical PTP deflection then repeat thestandardization in accordance with paragraph 4.1.3.6.2 and repeat the inspection.
4.1.3.6.8 Identifying the Circumferential Location of an Indication.
a. Observe the indication in the sweep mode. Maximize the indication response.
b. Identify the radial location by rotating the scanner to bring the displayed indication to the sweep line zero positionthat was identified in paragraph 4.1.3.6.4.
c. Using an approved marker, place a mark on the part surface in line with the scanner zero point.
4.1.3.6.9 Identifying the Length of a Crack-Like Indication Down the Bore of a Hole (If Required).
a. Without covering the face of the probe, wrap the probe shaft with a piece of masking tape.
b. Hold an approved fine-tipped marker parallel to the part surface with the marking point pointing toward the probeshaft.
c. Observe the indication in the sweep mode.
d. Insert the probe into the hole containing the crack-like indication.
e. As the probe is scanned through the hole use the marker to make a mark on the masking tape when the crackindication first reaches 30% FSH PTP.
f. Continue to scan in the hole. Use the marker to make a second mark on the masking tape when the indication heightdrops back to 30% FSH PTP.
g. Determine the indication length by measuring the distance between the marks on the masking tape. Use a ruler withthe appropriate scale.
4.1.3.6.10 Backup Procedures and Disposition of Non-Crack Indications. Indications with a phase response differentfrom the reference notch exhibiting greater than 30% vertical PTP response indicate hole contamination or damage.Additional hole preparation, reaming and/or cleaning may be required prior to reinspection.
a. If horizontal lift-off is greater than 30% FSW on the impedance display check for out-of-round condition or interfacenoise (see Figure 4-26). If allowed, have the hole reamed and then reinspect. Multi-layer structures may createirrelevant noise.
b. If no specific back-up procedure is available, verify crack indication using a another inspector and set-up. If possible,use different equipment and probes.
4.1.3.7 General Procedure for Rotary Fastener Hole Eddy Current Inspection of Magnetic Steel Parts Using theStaveley NORTEC-2000D/2000D+ With a MiniMite, Spitfire or RA/19 Scanners.
4.1.3.7.1 Equipment Preparation.
a. Ensure part, reference standard and probe are at ambient temperature to ensure valid, repeatable inspection results.
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b. Select the probe for best fit in the hole to be inspected. When inserted into the hole the probe should be in intimatecontact with the inner diameter but still rotate easily.
c. Application of Teflon tape to the probe is required (5 mils maximum thickness) to reduce probe wear and signalnoise caused by scanning rough surfaces. Wrap the tape over the coil and through the probe split. Do not wrap thetape completely around the probe split.
NOTE
• Teflon tape may need to be replaced periodically. Always confirm unit standardization responses to thereference standard notches after the tape is replaced. It is critical to ensure that tape is applied correctly andused in all steps of this procedure especially when inspecting the part and the instrument is displaying cornernoise that can be confused with crack-like indications.
• Some ferromagnetic materials may exhibit excessive noise due to variations in magnetic permeability. If thisis encountered, demagnetization of the part, before inspection, may help reduce the noise to acceptable levels.
d. Connect the probe to the scanner and connect the scanner cable to the scanner and eddycurrent unit.
4.1.3.7.1.1 Stored Setups.
a. Recall the program. Verify the settings match those listed in Table 4-12.
b. Perform standardization per paragraph 4.1.3.7.2.
4.1.3.7.1.2 If the setup has not been stored in instrument memory, proceed as follows:
a. Set the instrument to ‘‘DEFAULT’’ settings by performing the steps as follows:
(1) Select the SETUP MENU.
(2) Select DEFAULT and press ENTER.
(3) Select LD DEFLT and press ENTER.
(4) Rotate the Smartknob until ‘‘CONFIRM’’ appears on the lower left side of the display and press ENTER.
b. Adjust equipment settings (see Table 4-12). Minor adjustments to these settings are allowable as necessary to achieveoptimum signal characteristics.
c. Set FREQUENCY per specific procedure requirements. If no frequency is specified, use 500 KHz for 4000 seriessteels. For all other types of steel contact the Air Logisitics Center NDI Manager. Minor adjustments from thisguideline are allowable as necessary to achieve optimum signal characteristics.
d. Note the hole diameter to be inspected and adjust the Low Pass Filter and High Pass Filter to the values shown inTable 4-13.
Table 4-12. Settings Prior to Calibration of Nortec 2000D/2000D+ Fastener Hole Scanning of Magnetic SteelParts
Soft Key Description/Setting Soft Key Description/SettingMAIN MENU SETUP MENU
FREQ FREQUENCY 1/500KHz 1 FREQ/SINGLE
FREQ FREQUENCY 2/OFF 4 PRB DRV/MID
H-GAIN HORIZ. GAIN/65.0 dB
SPECIAL MENU
V-GAIN VERT. GAIN/65.0 dB RPM MiniMite and Spitfire
SCAN RPM/1500
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Table 4-12. Settings Prior to Calibration of Nortec 2000D/2000D+ Fastener Hole Scanning of Magnetic SteelParts - Continued
NOTE: Filters may be adjusted +or-50Hz to improve symmetry of notch response.
4.1.3.7.2 Standardization for Rotary Fastener Hole Inspection of Magnetic Steel Parts.
NOTE
This procedure was developed using a differential/reflection, fastener hole probe, 100KHz-1MHz. The differen-tial/reflection coil design will portray a negative and positive (figure eight) signal response on the impedanceplane display of the instrument.
a. With the scanner turned off, insert the probe into the appropriate size hole in the reference standard. The probeshould fit snug in the hole while rotating freely without binding. Verify the coil is 90º away from the notches andaway from hole edges and press NULL. Hold the probe still until nulling is complete.
b. Remove the probe from the hole.
c. With the SWEEP turned OFF, hold the scanner so that the probe is parallel to the reference standard. Place the coil incontact with a flat area of the reference standard at least 1/4 inch away from any edge or notch. Turn the scanner onwhile the coil makes contact with the reference standard to generate a liftoff signal.
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Figure 4-27. Lift-off Response with Phase Adjusted Correctly
d. Adjust the phase rotation by pressing the ANGLE key and rotating the Smartknob to achieve a substantiallyhorizontal lift-off signal. (See Figure 4-27). The lift signal may appear slightly different from that in the figure, butshould be horizontal.
e. Turn the scanner on and insert the probe into the appropriate size hole in the reference standard and locate the 0.030-inch corner notch located at the interface of the first and second layers.
f. Adjust the GAIN to place the entire notch response on the screen. Ensure the signal from the notch is separated fromthe lift-off signal by a minimum slope of 1:2 (Y:X) (30 degrees). (See Figure 4-28).
g. If the notch response does not provide at least a 1:2 separation from the lift-off, check to be sure the lift-off responseis horizontal. If the lift-off response is horizontal yet the notch response does not provide at least a 1:2 (Y:X) slope,select a different probe and repeat the standardization.
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Figure 4-28. Idealized Response Illustrating Minimum Separation Between Lift-off and EDM Notch Response
h. Return to the DISPLAY menu. Press the SWEEP key twice to enter the ‘‘SWEEP EXTRN’’ mode.
i. If the sweep signal is centered at 50% FSH, proceed to step a.
j. With the scanner turned off, insert the probe into the appropriate size hole in the reference standard. The probeshould fit snug in the hole while rotating freely without binding. Verify the coil is 90º away from the notches andaway from hole edges and press NULL. Hold the probe still until nulling is complete.
k. Remove the probe from the hole.
l. Turn the scanner on and reinsert into the reference standard hole. Maximize the signal from the 0.030 inch interfacenotch. Push the GAIN button and adjust the GAIN (both horizontal and vertical gains will be adjustedsimultaneously) as necessary to obtain an 80% Peak-to-Peak (PTP) signal from the notch. The notch signal shouldappear narrow and nearly symmetric above and below the baseline as shown in (Figure 4-29).
Figure 4-30. Acceptable Noise Level from Clean Hole (Steel)
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Figure 4-31. Signal from Hole Subject to Evaluation (Steel)
m. Ensure the signal from good areas of the notched hole, are relatively smooth across the sweep display. Noise level ingood areas shall be no more than 10% negative or positive from the baseline. (See Figure 4-30)
n. If the noise level is less than 10% from the baseline, proceed to paragraph 4.1.3.7.3.
o. If the noise level is greater than 10% from the baseline, repeat standardization procedure. If the noise level remainsabove 10% from the baseline after repeated standardization, perform the following steps:
(1) Recheck probe fit.
(2) Remove probe from scanner and check for inherent scanner and cable noise.
(3) Replace the probe, cable or scanner that is causing the noise and repeat standardization procedure.
4.1.3.7.3 Determining Maximum Index Speed.
a. Insert the probe into the appropriate hole in the reference standard and locate the notch at the interface of the first andsecond layers.
b. Monitor the display while moving the probe in and out over the interface notch.
NOTE
The maximum speed that the probe can be moved through the hole is the rate of probe travel that alwaysidentifies the notch and does not cause a reduction the peak in signal height from 80% vertical PTP.
c. Gradually increase the probe travel speed until the peak height of the notch response begins to decrease below 80%vertical PTP. This is the maximum probe travel speed.
4.1.3.7.4 Identifying the Scanner Zero or Scan Sweep Origin. Establish the scanner zero or scan origin by using oneof the following methods:
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4.1.3.7.4.1 Method A: Setting the Sync Zero Position.
a. Visually locate the notch on the top surface of the reference standard.
b. Insert the probe into the appropriate hole in the reference standard and rotate the scanner housing until the red LEDalarm indicator on the side of the scanner housing is pointed at the physical position of the notch on the standard asshown in (Figure 4-32 and Figure 4-33).
c. Turn on the scanner and adjust the SYNC ANGLE in the SPECIAL menu screen until the trailing edge of the notchindication is displayed on the left side of the screen with the leading edge of the indication positioned on the rightside of the screen (split-signal) as shown in (Figure 4-32).
NOTE
An acceptable alternate approach is to place the notch signal in the center of the screen and use this position asthe scanner zero.
4.1.3.7.4.2 Method B: Locating Sweep Crossing for Scanner/Notch Alignment.
a. Visually locate the notch on the top surface of the reference standard.
b. Insert the rotating probe into the appropriate hole in the reference standard until the maximum signal is obtainedfrom the notch.
c. Rotate the scanner until the top, center of the scanner is in line with the notch.
d. Note the point at the center of the notch signal crosses the sweep baseline. This is scanner zero as shown in(Figure 4-34).
e. Locate crack position by rotating the scanner until crack signal appears at the scanner zero location. Crack will be inline with the top, center of the scanner.
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Figure 4-32. SYNC Zero Position of the Nortec Spitfire Scanner (Steel)
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Figure 4-33. SYNC Zero Position of the Nortec MiniMite Scanner (Steel)
Figure 4-34. SYNC Zero Position (Method B) (Steel)
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4.1.3.7.5 Alarm Settings. Alarm use is optional unless otherwise specified in the procedure. See the operator’s manualfor alarm setting instructions.
4.1.3.7.6 Inspection.
NOTE
• Standardization of the unit should be verified at least every 10 minutes or after inspection of 30 holeswhichever is sooner. If standardization check sensitivity is not at least 70% of PTP all inspectionsaccomplished since the last successful calibration check must be repeated.
• Some ferromagnetic materials may exhibit excessive noise due to variations in magnetic permeability.Demagnetizing the part before inspection may help reduce the noise to acceptable levels.
a. Visually verify the hole surface condition will not damage the probe during inspection and is void of any foreignmaterial (e.g. grease, sealant, metal shavings). All holes SHOULD be cleaned with a tool such as a flex hone prior toinspection.
b. Enter data available to this point on an inspection record, if required. Enter additional data in record as it is obtained.
c. Press SWEEP so SWEEP EXTRN appears in the display. This indicates the inspection is being performed in thesweep mode.
d. With scanner off, check probe fit in the holes to be inspected. The fit should approximate the fit in the calibrationstandard.
e. Turn on the scanner and reinsert the probe in the hole. Inspect the hole by slowly pushing the probe through theentire hole and then pulling the probe slowly back through the hole. The probe must be kept perpendicular to the partsurface during scanning. Repeat a minimum of twice for each hole to be inspected.
f. The hole is considered uninspectable if the general surface condition causes noise signals greater than 10% above orbelow the baseline on the sweep display. (See Figure 4-30) Additional hole preparation and cleaning may be requiredprior to reinspection.
4.1.3.7.7 Indication Evaluation, Marking, and Recording.
a. Any repeatable indication above the background noise that exhibits a vertical response equal to or greater than 30%vertical PTP (See Figure 4-31) and appears similar the signal obtained from the reference standard shall beconsidered a possible crack.
b. Using an approved marker, mark all repeatable crack-like indications. (see paragraph 4.1.3.7.8 and paragraph4.1.3.7.9)
c. Verify the instrument standardization after the detection of a crack indication by performing a sensitivity check of theunit as follows:
(1) Insert the probe into the appropriate reference standard hole and maximize the signal response received from thenotch.
(2) The maximized notch signal should exhibit a vertical signal 70% - 90% PTP. If it does, then the defect indicationSHALL be considered valid and recorded.
(3) If notch signal does not provide the required 70% - 90% vertical PTP deflection then repeat the standardization inaccordance with paragraph 4.1.3.7.2 and repeat the inspection.
4.1.3.7.8 Identifying the Circumferential Location of an Indication.
a. Maximize the indication response.
b. Identify the radial location by rotating the scanner to bring the displayed indication to the sweep line zero position(left side of screen).
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c. Using an approved marker, place a mark on the part surface in line with the scanner zero point that was identified in(see paragraph 4.1.3.6.4).
4.1.3.7.9 Identifying the Length of a Crack-Like Indication Down the Bore of a Hole (If Required).
a. Without covering the face of the probe, wrap the probe shaft with a piece of masking tape.
b. Hold an approved fine-tipped marker parallel to the part surface with the marking point pointing toward the probeshaft.
c. Insert the probe into the hole containing the crack-like indication.
d. As the probe is scanned through the hole, use the marker to make a mark on the masking tape when the crackindication first reaches 30% FSH PTP.
e. Continue to scan in the hole. Use the marker to make a second mark on the masking tape when the indication heightdrops back to 30% FSH PTP.
f. Determine the indication length by measuring the distance between the marks on the masking tape. Use a ruler withthe appropriate scale.
4.1.3.7.10 Backup Procedure. If the part specific procedure does not specify a backup procedure it is recommended thatthe indication be verified by a second inspector. Repeat standardization per (paragraph 4.1.3.7.2) and have a second inspectorverify the indication. If available, separate equipment and probes should also be used for each independent inspection. If thedefect indication is not confirmed, proceed to system securing.
4.1.3.8 General Procedure for Rotary Fastener Hole Eddy Current Inspection of Titanium Parts Using the StaveleyNortec 2000D with a Minimite, Spitfire, and RA/19 Scanners.
4.1.3.8.1 Equipment Preparation.
a. Ensure part, reference standard and probes are at ambient temperature to ensure valid, repeatable inspection results.
b. Select the probe for best fit in the hole to be inspected. When inserted into the hole, the probe should be in intimatecontact with the inner diameter but still rotate easily.
c. Application of Teflon tape (5 mils maximum thickness) to the probe is required to reduce probe wear and signalnoise caused by scanning rough surfaces and hole edges. Wrap the tape over the coil and through the probe split. Donot wrap the tape completely around the probe split.
NOTE
The Teflon tape may need to be replaced periodically. Always confirm unit standardization responses to thereference standard notches after the tape is replaced. It is critical to ensure that tape is applied correctly and usedin all steps of this procedure.
d. Connect the probe to the scanner and connect the scanner cable to the scanner and eddycurrent unit.
4.1.3.8.1.1 Stored Setups.
a. Recall the program. Verify the settings match those listed in Table 4-14.
b. Proceed to paragraph 4.1.3.8.2
4.1.3.8.1.2 If the setup has not been stored in instrument memory, proceed as follows:
a. Set the instrument to ‘‘DEFAULT’’ settings by performing the steps as follows:
(1) Select the SETUP MENU.
(2) Select DEFAULT and press ENTER.
(3) Select LD DEFLT and press ENTER.
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(4) Rotate the Smartknob until ‘‘CONFIRM’’ appears on the lower left side of the display and press ENTER.
b. Adjust equipment settings per Table 4-14. Minor adjustment to these settings are allowed as necessary to achieveoptimum signal characteristics.
c. Set the FREQUENCY in accordance with the part specific procedure. If no frequency is specified, use 2 MHz.
d. Note the hole diameter to be inspected and adjust the Low Pass Filter (LP FILTER) and High Pass Filter (HPFILTER) to the values shown in Table 4-15.
Table 4-14. Nortec 2000D Initial Calibration Settings for Rotary Scanning of Fastener Holes in Titanium Parts
Soft Key Description/Setting Soft Key Description/SettingMAIN MENU SETUP MENU
FREQ FREQUENCY 1/2MHz 1 FREQ/SINGLE
FREQ FREQUENCY 2/OFF 4 PRB DRV/MID
H-GAIN HORIZ. GAIN/65.0 dB
V-GAIN VERT. GAIN/65.0 dB
ANGLE 0°FILTER MENU (See
Table 4-14 for filter set-tings) SPECIAL MENU
CONT CONT NULL/OFF RPM MiniMite and SpitfireScanners
SCAN RPM/1500
R/A 19 Scanner
SCAN RPM/1200
DISPLAY MENU SYNC ANG 0
SWEEP SWEEP/OFF
V-POS 50%
H-POS 50%
SCREEN MENU
PERSIST PERSIST/OFF
DISP ERS DISP ERASE/0.2 s
GRATICULE ON
DOT/BOX DOT
Table 4-15. (Titanium) Filter Settings vs. Hole Diameter
NOTE: Filters may be adjusted +/-50Hz to improve symmetry of notch response.
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4.1.3.8.2 Standardization for Rotary Fastener Hole Inspection of Titanium Parts.
NOTE
This procedure was developed using a differential/reflection, fastener hole probe, 500KHz-2MHz. The differen-tial/reflection coil design will portray a negative and positive (figure eight) signal response on the impedanceplane display.
a. With the scanner turned off, insert the probe into the appropriate size hole in the reference standard. The probeshould fit snug in the hole without binding. Verify the coil is 90° away from the corner notch and away from holeedges and press NULL. Hold the probe still until nulling is complete.
b. Remove the probe from the hole. With the SWEEP turned OFF, hold the scanner so that the probe is parallel to thesurface of the reference standard. Place the coil in contact with a flat area of the reference standard at least 1/4 inchaway from any edge or notch. Turn the scanner on while the coil makes contact with the reference standard togenerate a liftoff signal.
c. Adjust the phase rotation by pressing the ANGLE key and rotating the Smartknob to achieve a substantiallyhorizontal liftoff signal.
NOTE
Titanium will exhibit very little phase separation between the lift-off and defect responses.
d. Turn the scanner on and insert the rotating probe into the appropriate hole size in the reference standard and locatethe 0.030 inch corner notch located at the interface of the first and second layers.
e. Adjust the GAIN to place the entire notch response on the screen.
f. Adjust the PHASE until the notch response is at a 45 degree angle from the top left corner of the display down to thebottom right corner of the display. (See Figure 4-35)
g. Return to the DISPLAY menu. Press the SWEEP key twice to enter the ‘‘SWEEP EXTRN’’ mode. The instrument isnow in sweep mode.
h. If the sweep signal is centered at 50% FSH, proceed to step k.
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Figure 4-35. Response from 0.030 Inch Interface Notch with Phase at a 45 Degree Angle
Figure 4-36. Example of Properly Calibrated Sweep Display (Titanium)
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Figure 4-37. Example of Acceptable Noise Level from Clean Hole. Noise Level Shall Not Exceed 10% FSH fromBaseline
Figure 4-38. Display of Signal from Hole That is Subject to Evaluation (Titanium)
i. With the scanner turned off, insert the probe into the appropriate size hole in the reference standard. The probeshould fit snug in the hole while rotating freely without binding. Verify the coil is 90º away from the notches andaway from hole edges and press NULL. Hold the probe still until nulling is complete.
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j. Remove the probe from the hole.
k. Turn the scanner on and reinsert into the reference standard hole. Maximize the signal from the 0.030 inch interfacenotch. Push the GAIN button and adjust the GAIN (both horizontal and vertical gains will be adjustedsimultaneously) as necessary to obtain an 80% Peak-to-Peak (PTP) signal from the notch. The notch signal shouldappear narrow and nearly symmetric above and below the baseline as shown in Figure 4-36.
l. Ensure the signal response from good areas of the hole is relatively smooth across the sweep display. Noise level ingood areas shall be no more than 10% negative or positive from the baseline. See Figure 4-37.
m. If the noise level is 10% or less from the baseline, proceed to paragraph 4.1.3.8.3.
n. If noise signals greater than 10% from the baseline appear, repeat standardization per paragraph 4.1.3.8.2. If the noiselevel remains excessive after repeated standardization, perform the following steps:
(1) Recheck probe fit.
(2) Remove probe from scanner and check for inherent scanner and cable noise.
(3) Replace the probe, cable or scanner that is causing the noise and repeat standardization per paragraph 4.1.3.8.2.
4.1.3.8.3 Determining Maximum Index Speed.
a. Insert the probe into the appropriate hole in the reference standard and locate the 0.030 inch notch at the interface ofthe first and second layers.
b. Monitor the display while moving the probe in and out over the interface notch.
NOTE
The maximum speed that the probe can be moved through the hole is the rate of probe travel that alwaysidentifies the notch and does not cause a reduction the peak in signal height from 80% FSH PTP.
c. Gradually increase the probe travel speed until the peak height of the notch response begins to decrease below 80%FSH PTP. This is the maximum probe travel speed.
4.1.3.8.4 Identifying the Scanner Zero or Scan Origin. Establish the scanner zero or scan origin by using one of thefollowing methods:
4.1.3.8.4.1 Method A: Setting the scanner Sync Zero position.
a. Visually locate the notch on the top surface of the reference standard.
b. Insert the probe into the appropriate hole in the reference standard and rotate the scanner housing until the red LEDalarm indicator on the side of the scanner housing is pointed at the physical position of the notch on the standard asshown in (See Figure 4-39 and Figure 4-40).
c. Turn on the scanner and adjust the SYNC ANGLE in the SPECIAL menu screen until the trailing edge of the notchindication is displayed on the left side of the screen with the leading edge of the indication positioned on the rightside of the screen (split-signal) as shown in (see Figure 4-39).
NOTE
An acceptable alternate approach is to place the notch signal in the center of the screen and use this position asthe scanner zero.
4.1.3.8.4.2 Method B: Locating Sweep Crossing for Scanner/Notch Alignment.
a. Visually locate the notch on the top surface of the reference standard.
b. Insert the rotating probe into the appropriate hole in the reference standard until the maximum signal is obtainedfrom the notch.
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c. Rotate the scanner until the top, center of the scanner is in line with the notch.
d. Note the point at the center of the notch signal crosses the sweep baseline. This is scanner zero as shown inFigure 4-41.
e. Locate crack position by rotating the scanner until crack signal appears at the scanner zero location. Crack will be inline with the top, center of the scanner.
Figure 4-39. Establishing SYNC Zero Position of the Nortec Spitfire Scanner (Titanium)
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Figure 4-40. Establishing SYNC Zero Position of the Nortec MiniMite Scanner (Titanium)
Figure 4-41. Establishing SYNC Zero Position of the Nortec Spitfire Scanner (Method C)
4.1.3.8.5 Alarm Setting. Alarm use is optional. Refer to the operator manual or part specific procedures for alarm settinginstructions.
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4.1.3.8.6 Inspection.
NOTE
• Standardization of the unit should be verified at least once every 10 minutes or every 30 holes, whichevercomes first. If the interface notch signal does not provide the required 70-90% vertical PTP deflection thenrepeat standardization and inspection of all holes done since the last good calibration check.
• The surface condition of the hole can affect the inspection result. This procedure assumes that the bore isessentially round and smooth. The hole is considered uninspectable if the general surface condition causesnoise signals greater than 10% from the baseline during scanning. Application of Teflon tape over the probecoils may help reduce excessive noise.
a. Visually verify the hole surface condition will not damage the probe during inspection and is void of any foreignmaterial (e.g. grease, sealant, metal shavings).
b. Enter data available to this point on an inspection record, if required. Enter additional data in record as it is obtained.
c. With the scanner off, check probe fit in the holes to be inspected. The fit should approximate the fit in the referencestandard. Remove the probe from the hole.
d. Turn on the scanner and reinsert the probe in the hole. Inspect by slowly pushing the probe through the entire holethen pulling the probe slowly back through the hole. The probe must be kept perpendicular to the part surface duringscanning. The hole is considered uninspectable if the general surface condition causes noise signals than 10% aboveor below the baseline on the sweep display (see Figure 4-37) Additional hole preparation and cleaning may berequired prior to reinspection. Repeat a minimum of twice for each hole to be inspected.
4.1.3.8.7 Indication Evaluation, Marking, and Recording.
4.1.3.8.7.1 Any repeatable indication above the background noise, exhibits a vertical response greater than 30% verticalPTP (See Figure 4-38) and appears similar to that obtained from the reference standard shall be considered a possible crack.
a. Using an approved marker, mark all repeatable crack-like indications.
b. Verify the instrument standardization after the detection of a crack indication by performing a sensitivity check of theunit as follows:
(1) Insert the probe into the appropriate reference standard hole and maximize the signal response received from thereference notch.
(2) The notch signal should exhibit a vertical signal within 70% - 90% PTP. If it does then the defect indicationSHALL be considered valid and recorded.
(3) If the notch signal does not provide the required 70% - 90% vertical PTP deflection then repeat thestandardization in accordance with paragraph 4.1.3.8.2 and repeat the inspection.
4.1.3.8.8 Identifying the Circumferential Location of an Indication.
a. Maximize the indication response.
b. Identify the radial location by rotating the scanner to bring the displayed indication to the sweep line zero position(left side of screen).
c. Using an approved marker, place a mark on the part surface in line with the scanner zero point that was identified inparagraph 4.1.3.5.4.
4.1.3.8.9 Identifying the Length of a Crack-Like Indication Down the Bore of a Hole (If Required).
a. Without covering the face of the probe, wrap the probe shaft with a piece of masking tape.
b. Hold an approved fine-tipped marker parallel to the part surface with the marking point pointing toward the probeshaft.
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c. Insert the probe into the hole containing the crack-like indication.
d. As the probe is scanned through the hole use the marker to make a mark on the masking tape when the crackindication first reaches 30% FSH PTP.
e. Continue to scan in the hole. Use the marker to make a second mark on the masking tape when the indication heightdrops back to 30% FSH PTP.
f. Determine the indication length by measuring the distance between the marks on the masking tape. Use a ruler withthe appropriate scale.
4.1.3.8.10 Backup Procedure. If the part specific procedure does not specify a backup procedure it is recommended thatthe indication be verified by a second inspector. Repeat standardization per paragraph 4.1.3.8.2 and have a second inspectorverify the indication. If available, separate equipment and probes should also be used for each independent inspection. If thedefect indication is not confirmed, proceed to system securing.
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SECTION II EDDY CURRENT PROCESS CONTROL PROCEDURES
4.2 EDDY CURRENT PROCESS CONTROL PROCEDURES.
4.2.1 General Process Control for Eddy Current Inspection Probes and Standards. For maximum reliability in ET,a high signal-to-noise ratio is desired. No specific signal-to-noise ratio is mandatory, but a minimum of 3-to-1 is desirable forflaw detection.
4.2.2 Probe Test. The following steps are designed for testing in-use surface eddy current probes 1/8-inch or smaller:
a. Attach probe and cable to the proper connector.
b. Place Teflon tape across the four surface slots on the Air Force general purpose eddy current standard.
c. Turn on the unit by pressing the green circular button. When the unit is first turned on it will display the‘‘DIAGNOSTICS’’ self-test and the last setup program that was used.
NOTE
Step d - step j loads the ‘‘DEFAULT’’ program.
d. Press the [SETUP/SPECIAL] button until the ‘‘set up’’ menu appears. The ‘‘setup’’ menu displays REPORTCLOCK DEFAULT in the top row.
e. Press the 3rd soft key [ ] until DEFAULT is highlighted.
f. Press the [ENTER] button.
g. Press the 4th soft key [ ] to select LD DEFLT. There should be 3 highlighted areas: LD DEFLT lower right sideabove the 4th soft key [ ], LD DEFLT 4th row in right column, and DEFAULT above 5th soft key [ ].
h. Press the [ENTER] button.
NOTE
A 4th highlighted LD DEFLT will be displayed above the function row. To the right of the highlighted LDDEFLT there will be either CANCEL or CONFIRM.
i. Rotate the SMARTKNOB until it reads CONFIRM.
j. Press the [ENTER] button.
NOTE
The ‘‘DEFAULT’’ program is now loaded. The MAIN menu display should be in ‘‘flying dot’’ mode. Thefollowing values should be displayed.
FREQUENCY 100 kHz
ANGLE 0°H-GAIN 40.0 dB
V-GAIN 40.0 dB
PROBE DRIVE MID
k. FREQUENCY should be highlighted; if not, press 1st soft key [ ].
l. Rotate SMARTKNOB to set the minimum frequency identified on the probe.
m. Press the 3rd soft key [ ].
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NOTE
GAIN should be highlighted above the soft key and both the H-GAIN and V-GAIN should be highlighted on theright side.
n. Rotate the SMARTKNOB to set the gain at 50 dB horizontal and 50 dB vertical.
o. Place the probe on the Teflon tape away from slot and ‘‘null’’ the instrument by pressing the [NULL] button.
p. Press the [ERASE] button.
NOTE
After ‘‘nulling’’ the instrument it is always a good practice to press the [ERASE] button after pressing the[NULL]button. This clears the display and places the ‘‘flying dot’’ at the center position.
q. Press the 2nd soft key [ ]. ANGLE should be highlighted in two places.
r. Scan over the 0.050 inch slot while rotating the SMARTKNOB to adjust phase angle. The ‘‘flying dot’’ should berotated to a vertical position.
s. Press the 3rd soft key [ ]. (See step m note)
t. While scanning the 0.050 inch slot, rotate the SMARTKNOB until the response from the crack moves the dot exactlythree square divisions. To improve gain control use the [ERASE] button occasionally to clear the display.
u. Record the gain setting for that frequency.
v. Repeat the step k through step u to achieve a low, medium (pick a number that is between the low and high), andhigh frequency reading for each probe. {e.g., 60.3 at 50 kHz for a low frequency. 53.2 at 200 kHz and 59.6 at 500kHz}
NOTE
Some probes have their frequency range (low to high frequencies) identified on the probe handle. Others maynot. If the probe frequency range is not identified, use 200 kHz, 500 kHz, or 1 MHz. The “flying dot” will notbehave properly when the probe’s frequency range is exceeded (either low or high). The dot should be relativelystable after “nulling” the instrument. There should be a definite response displayed when the 0.050 inch slot isscanned. If not, try another frequency. The optimum frequency for the probe is the frequency with the lowest gainsetting and highest signal response.
Probes shall be tested after receiving them and periodically thereafter. If the gain settings are off by 20 percent or morethe next time you test the probe, it should be replaced.
4.2.3 Slot Test. Attach probe and cable to the proper connector.
a. Place Teflon tape across the four surface slots on the Air Force general purpose eddy current standard.
b. Turn on the unit by pressing the green circular button. When the unit is first turned on it will display the‘‘DIAGNOSTICS’’ self test and the last setup program that was used.
NOTE
Step c - i loads the ‘‘DEFAULT’’ program.
c. Press the [SETUP/SPECIAL] button until the ‘‘set-up’’ menu appears. The ‘‘setup’’ menu displays REPORTCLOCK DEFAULT in the top row.
d. Press the 3rd soft key [ ] until DEFAULT is highlighted.
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e. Press the [ENTER] button.
f. Press the 4th soft key [ ] to select LD DEFLT. There should be 3 highlighted areas: LD DEFLT lower right sideabove the 4th soft key [ ], LD DEFLT 4th row in right column, and DEFAULT above 5th soft key [ ].
g. Press the [ENTER] button.
NOTE
A 4th highlighted LD DEFLT will be displayed above the function row. To the right of the highlighted LDDEFLT there will be either CANCEL or CONFIRM.
h. Rotate the SMARTKNOB till it reads CONFIRM.
i. Press the [ENTER] button.
NOTE
The ‘‘DEFAULT’’ program is now loaded. The MAIN menu display should be in ‘‘flying dot’’ mode. Thefollowing values should be displayed.
FREQUENCY 100 kHz
ANGLE 0°H-GAIN 40.0 dB
V-GAIN 40.0 dB
PROBE DRIVE MID
j. FREQUENCY should be highlighted; if not, press 1st soft key [ ].
k. Rotate SMARTKNOB to set the frequency at 500 kHz.
l. Press the 3rd soft key [ ].
NOTE
GAIN should be highlighted above the soft key and both the H-GAIN and V-GAIN should be highlighted on theright side.
m. Rotate the SMARTKNOB to set the gain at 50 dB horizontal and 50 dB vertical.
n. Place the probe on the Teflon tape away from slot and ‘‘null’’ the instrument by pressing the [NULL] button.
o. Press the [ERASE] button.
NOTE
After ‘‘nulling’’ the instrument it is always a good practice to press the [ERASE] button after pressing the[NULL]button. This clears the display and places the flying dot at the center position.
p. Press the 2nd soft key [ ]. ANGLE should be highlighted in two places.
q. Scan over the 0.050 inch slot while rotating the SMARTKNOB to adjust phase angle. The ‘‘flying dot’’ should berotated to a vertical position.
r. Press the 3rd soft key [ ]. (See paragraph 4.2.3, step n note)
s. While scanning the 0.050 inch slot, rotate the SMARTKNOB until the response from the crack moves the dot exactlythree square divisions. To improve gain control, use the [ERASE] button occasionally to clear the display.
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t. Place a straight edge (ruler, triangle edge, etc) adjacent to and inline with the notch so that the probe’s center is onthe center of the notch.
u. Press the [ERASE] button so that the dot is showing at three divisions.
v. Move the probe down the slot lengthwise using the straight edge as a guide.
w. The dot should not move more than 1/10th of a division until it comes to the edge of the standard or the edge of theslot (Edge Effect).
x. Repeat the step m through step u (see paragraph 4.2.3) for the 0.020, 0.010, and 0.005 slots. Remember the gain willhave to be increased to align the dot at three divisions.
NOTE
For the 0.005″slot, use one division instead of three divisions. The aluminium general purpose eddy currentstandard SHALL be tested whenever the slots appear to be worn.
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T.O. 33B-1-2
CHAPTER 5ULTRASONIC INSPECTION
SECTION I ULTRASONIC INSPECTION GENERAL PROCEDURE
(NOT APPLICABLE)
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SECTION II ULTRASONIC INSPECTION PROCESS CONTROL
5.1 ULTRASONIC INSPECTION PROCESS CONTROL.
NOTE
Ultrasonic process control checks are intended for general purpose transducers and centrally procured ultrasonicinstruments. Manufactures’ recommended process control checks SHOULD be used for special purposetransducers and ultrasonic instruments. For guidance contact the appropriate ALC NDI Manager.
Gain: 40 dB starting point Gain: 40 dB starting point Gain: 40 dB starting point
Range: 10.00 Frequency: Select Best Pulser: Single
MTL Vel: Refer to Auto-Cal Damping: 50 Reject: 0
Delay: 0.00 Rectif: Full Rep-Rate: High
GateA-THRSH: 10%
A-Start: 2.500
A-Width: 0.750
Leave remaining function keys set as they are
Calibration Procedures paragraph 5.1.1
1) Utilize three blocks with 3/64, 5/64, and 8/64 FBH with 3″ metal travel distance
2) Place the transducer on the 5/64 FBH block and set to 35% amplitude
3) Go to the 3/64 FBH and the amplitude should be 10-16%
4) Then go to the 8/64 FBH and the amplitude should be 85-95%
5.1.1 Procedure for Determining Vertical Linearity Limits (ASTM Blocks).
a. (Table 5-1) contains the set-up for the USN-52 ultrasonic unit, the instrument may need to be adjusted to obtain therequired screen presentation.
b. Use three ASTM blocks with 3-inch metal travel distances, one each with a 3/64, 5/64, and 8/64-inch diameter flat-bottom hole (FBH).
c. Move the search unit over the surface of the 5/64-inch FBH block until a maximum response is obtained from theFBH. Make sure that the reject control and filters are in the ‘‘off’’ or minimum positions. Adjust the instrument gaincontrol until the FBH signal is 35-percent of vertical screen height on the CRT.
d. Leave the gain fixed, maximize the FBH signal on the 3/64 and 8/64 FBH blocks. Record the FBH signal amplitudes.
e. If the instrument is linear, the signals from the 3/64 and 8/64 FBH’s will be 13% ±3% and 90% ±5% of saturationrespectively. Thus, a 3/64 FBH signal between 10% and 16% of saturation is considered linear; an 8/64 FBH signalbetween 85% and 95% of saturation is considered linear.
f. Instruments not linear (within the above limits) SHALL be repaired or replaced.
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5.1.2 Procedure for Determining Horizontal Linearity Limits (Type 2 IIW Block). In lieu of any specific linearityrequirement, the horizontal linearity MAY be checked as follows:
a. Table (5-2) contains the set-up for the USN-52 ultrasonic unit, the instrument may need to be adjusted to obtain therequired screen presentation.
b. Use the IIW block and a straight beam transducer (see Figure 5-1).
Figure 5-1. Use the Type 2 IIW Block to Check Horizontal Linearity
c. Place the transducer on the IIW block and adjust the gain so that the first back reflection achieves 95% full screenheight and the range to obtain six back reflections on the display screen. The first back reflection SHOULD belocated at the left side of the base line (the initial pulse SHOULD be off the screen), and the 6th back reflectionSHOULD be located at the right side of the base line.
d. Measure the distance between the leading edge of adjacent back reflections. Ideal horizontal linearity will beindicated by an equal distance between the leading edges of subsequent back reflections. If all the values are equalwithin 3.0% of the full scale width, the instrument is considered linear in the horizontal direction.
e. Instruments not linear within the above limits SHALL be repaired or replaced.
Table 5-2. Horizontal Linearity
Horizontal Linearity (IIW)Basic Receiver PulserGain: 30 dB Gain: 30 dB Gain: 30 dB
Range: 10.00 Frequency: 2-8 Pulser: Single
MTL Vel: Refer to Auto- Damping: 50 Reject: 0Cal
Delay: 0.000 Rectif: Full Rep-Rate: High
GateGain: 30 dB
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Table 5-2. Horizontal Linearity - Continued
Horizontal Linearity (IIW)A-THRSH: 20%
A-Start: Move as needed
A-Width: 1.000
Leave remaining function keys set as they are
Calibration Proceduresparagraph 5.1.2
1) Lay IIW block flat
2) Place the transducer on standard; the indication should go thru gate
3) Use the delay function to move IP off screen and the first back reflection to the IP position (zero on the horizontalzero/trace line)
4) Adjust the gain to get 6 indications
5) Use the ‘‘A-START’’ key to read the distance for each indication. They should be 1″ apart. Note: The ‘‘B’’ gatemay be used for measurement between multiples
5.1.3 Procedure for Determining Inspection System Sensitivity (ASTM Blocks).
NOTE
• The 1 MHz and 15 MHz requirements are applicable only when these frequencies are to be used; they are notspecific requirements for all instruments.
• Unless otherwise specified in a detailed procedure, use the ASTM reference blocks with flatbottom holes(FBH). The FBH, which SHOULD be detectable with the respective frequencies, are shown in (seeTable 5-3).
a. (Table 5-1) contains the set-up for the USN-52 ultrasonic unit, the instrument may need to be adjusted to obtain therequired screen presentation.
b. Select the ASTM block with the appropriate FBH at a depth of 3-inches. (Table 5-3) shows compensation values.When the 3/64 FBH and the 5/64 FBH are used in place of the 2/64 and 4/64 respectively. For example: When usingthe 3/64 FBH instead of the 2/64, the equipment gain must be increased 7dB to obtain the same inspectionsensitivity. The increase in gain will cause the signal height to exceed 60-percent screen height.
c. Obtain a peak signal from the appropriate FBH.
Table 5-3. Minimum Sensitivity Requirements
Frequency (MHz) 1 2.25 2.25 5 5
FBH Size (inch/64) 8 5 4 3 2
dB Compensation N/A +4 N/A +7 N/A
d. Adjust the Gain control of the instrument until the discontinuity indication is 60-percent of full screen height.
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e. Notice the baseline noise in the test region (adjacent to the FBH indication). The noise SHOULD be no higher than20-percent of full screen height. The noise threshold does not change when using ASTM blocks requiring additionalgain.
f. When a reference standard, specified by a detailed inspection procedure, is used the minimum signal-to-noise ratio isalso 3 to 1.
g. If the inspection system does not meet these sensitivity requirements, the transducer and/or cable SHALL be replacedand the sensitivity checked again. If the inspection system still does not meet the above requirements, the instrumentSHALL be repaired or replaced.
5.1.4 Checking Resolution (Type 2 IIW Block). When no resolution is specified, the following procedures is used tocheck resolution:
5.1.4.1 Back Surface Resolution (Figure 5-2)(2.25 MHz only).
a. (See Table 5-4) contains the set-up for the USN-52 ultrasonic unit, the instrument may need to be adjusted to obtainthe required screen presentation.
b. Position the transducer on a Type 2 IIW block, and peak the signal from reflector A.
c. Maximize the separation of the signals from the reflectors A, B, and C.
d. Evaluate the resolution by matching the signal patterns. Good resolution is indicated by the respective signalsreturning to the baseline.
e. If a test system with a 2.25 MHz search unit does not meet these resolution requirements, the transducer and/or cableSHALL be replaced and the resolution checked again. If the inspection system still does not meet the aboverequirements, the instrument SHALL be repaired or replaced.
Figure 5-2. Use Type 2 IIW Block to Check Back Surface Resolution
a. (See Table 5-4) contains the set-up for the USN-52 ultrasonic unit, the instrument may need to be adjusted to obtainthe required screen presentation.
b. Position the transducer on an IIW block at P-1 or P-2 as shown in (see Figure 5-3). P-1 gives 0.2-inch metal traveldistance to the edge of the large hole. P-2 gives 0.4-inch metal travel distance.
c. Maximize the separation between the initial pulse and the hole signal. Evaluate the signal pattern according to thecriteria given in (see Figure 5-3).
d. Check that the signal of the hole is actually the indication of the first echo from the hole by noting the position of thehole signal on the calibrated distance scale of the waveform display. The distance SHOULD be the actual depth ofthe hole.
e. The first echo from the edge of the hole SHALL be completely separate from the initial pulse. The initial pulseSHALL return to the baseline, as shown in the ‘‘good’’ example of (see Figure 5-3), for the following conditions:
• 10 MHz: Good at P-1 and P-2.• 5 MHz: Good at P-2.• 2.25 MHz: Good at P-2.
f. If the first echo from the edge of the hole is not completely separate from the initial pulse as required above, thetransducer and/or cable SHALL be replaced and the dead zone checked again. If the inspection system still does notmeet the above requirements, the instrument SHALL be repaired or replaced.
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Figure 5-3. Use a Type 2 IIW Block to Check Entry Surface Resolution
Table 5-5. Dead Zone Set-up
ASTM Block Dead Zone (Entry Surface Resolution)Basic Receiver Pulser
Gain: 30 dB starting point Gain: 30 dB starting point Gain: 30 dB starting point
Range: 2.500 Frequency: 2-8 Pulser: Single
MTL Vel: Refer to Auto-Cal Damping: 50 Reject: 0
Delay: 0.00 Rectif: Full Rep-Rate: High
GateGain: 30 dB starting point
A-THRSH: 20%
A-Start: 0.200
A-Width: 0.200
Leave remaining function keys set as they are
Calibration Proceduresparagraph 5.1.4.3
1) Pick the block that matches the frequency of transducer you are using (see Table 5-6)
2) Place transducer on the block over the flat bottom hole (FBH)
3) Look for the FBH signal between the initial pulse (IP) and back reflection (BR). The FBH should be complete andseparate indication. (See Figure 5-3)
4) Adjust the gain to get 6 indications
5) Use the ‘‘A-START’’ key to read the distance for each indication. They should be 1″ apart. Note: The ‘‘B’’ gatemay be used for measurement between multiples
Back Surface Resolution in Aluminum (inch) 0.5 0.3 0.2 0.1 0.1
5.1.4.3 Entry Surface Resolution (ASTM Blocks).
a. (See Table 5-5) contains the set-up for the USN-52 ultrasonic unit, the instrument may need to be adjusted to obtainthe required screen presentation.
b. Use an ASTM block with a #5 FBH or other size if specified. Choose a block with a metal travel distance accordingto the frequency being used (see Table 5-6).
c. Maximize the separation between the initial pulse and the signal from the hole.
d. Check that the signal from the hole is actually the indication of the first echo from the hole by noting the position ofthe signal from the hole on the calibrated distance scale of the waveform display. The distance SHOULD be theactual depth of the hole.
e. Evaluate the waveform patterns.
5.1.5 A-Scan Straight Beam Distance Calibration.
Table 5-7. Auto Calibration Procedures
AUTO CAL PROCEDURES:ASTM BLOCKS1) COLD BOOT UNIT
2) SELECT LOWER LEVEL MENU WITH WHITE UP/DOWN ARROW
3) TOGGLE THRU LOWER LEVEL MENU UNTIL YOU SEE THE AUTO CAL COLUMN
4) SELECT:
A. Auto-Cal: On
B. Gate Logic: Positive
C. Measure: 0-1st
D. TOF: Flank
INSTRUMENT SETTINGS
BASIC RECEIVER PULSERGain: 30 dB Gain: 30 dB Gain: 30 dB
Range: 5.000 Frequency: 2-8 MHz Pulser: Single
Mtl-Vel: (self-adjust) Damping: 50 Reject: 0
Delay: 0.000 Rectif: Full Rep-Rate: High
GATE S-CAL MEMGain: 30 dB Gain: 30 dB Gain: 30 dB
A-Thrsh: 20% Cal: Recall: Off
A-Start: 0.700 A-Start: 0.700 Set:#1
A-Width: 4.500 S-Ref: 1.000 Store: Off
TCGGain: 30 dB
DAC/TCG: Off
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Table 5-7. Auto Calibration Procedures - Continued
AUTO CAL PROCEDURES:ASTM BLOCKSA-Start: 0.700
DAC Echo: 0
6) Select S-Cal menu
7) Press Cal left/right key simultaneously, ″REC 0″ will appear
8) Confirm S-Ref thickness is one inches (1.0″) and select your 0025 ASTM Block
9) Place transducer on standard, ensure that the back reflection goes thru gate by adjusting gain and move probe asneeded to maximize signal.
10) Press the right arrow key next to cal, ″REC 0″ will change to ″REC 1″ and S-Ref will change to 4.000 inches
11) Adjust S-Ref thickness to 3.75″ and select 0300 ASTM block
12) Place transducer on standard again, ensuring that back reflection passes thru gate, adjust gain as needed.
13) Press the right key next to Cal twice, and the unit will calculate the material velocity, and zero, probe delay(record settings for future use)
a. (See Table 5-7) contains the set-up for the USN-52 ultrasonic unit using the ASTM blocks. Adjust the range toaccommodate the IIW block; the instrument may need to be adjusted to obtain the required screen presentation.
b. Position the search unit on an IIW block at P-1, P-2 or P-3 as shown in (see Figure 5-4). The distance betweenmultiple back reflections is as follows:
• 1.00 inch at P-1.• 4.00 inch at P-2.• 8.00 inch at P-3.
c. Set the time base for the applicable distance calibration. Example: see display screens for various distancecalibrations are shown in (see Figure 5-4).
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Figure 5-4. Straight Beam Distance Calibration with IIW Block
Gain: 30 dB starting point Gain: 30 dB starting point Gain: 30 dB starting point
Range: 5.00 Frequency: 2-8 Pulser: Single
MTL Vel: Refer to Auto-Cal Damping: 50 Reject: 0
Delay: 0.00 Rectif: Full Rep-Rate: High
GateGain: 30 dB starting point
A-THRSH: 20%
A-Start: Move as needed
A-Width: 1.000
Leave remaining function keys set as they are
Calibration Proceduresparagraph 5.1.5.3
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Table 5-8. Straight Beam Distance - Continued
ASTM Block Straight Beam Distance Calibration1) Select the 7075-05-0025 block
2) IP=0 BR=1.0
3) Look at multiples and count. You should have a multiple every 1.0″4) Adjust the gain until you have four indications from back wall. Move A-START to read each distance
a. (See Table 5-7 or Table 5-8) contains the set-up for the USN-52 ultrasonic unit, the instrument may need to beadjusted to obtain the required screen presentation.
b. Position the transducer on the miniature block at P-1 or P-2 as shown in (see Figure 5-5). The distance betweenmultiple back reflections is as follows:
c. Set the time base for the applicable distance calibration.
• 0.250 inch at P-1.• 1.000 inch at P-2.
Figure 5-5. Straight Beam Distance with Miniature Angle Beam Block
5.1.5.3 Straight Beam Distance Calibration (ASTM Blocks). (See Table 5-7) contains the set-up for the USN-52ultrasonic unit, the instrument may need to be adjusted to obtain the required screen presentation.
5.1.5.3.1 Distance calibration MAY be performed using multiple reflections from the FBH or the back surfaces of ASTMblocks. The procedures are identical to the procedures outlined above using the Type 2 IIW block and the miniature anglebeam block.
This procedure works with all commonly used angles.
a. (See Table 5-9) contains the set-up for the USN-52 ultrasonic unit, the instrument may need to be adjusted to obtainthe required screen presentation.
b. Position the transducer at P-1 (see Figure 5-6) and adjust the location of the transducer to be directed at radius R-2.Peak the signal from radius R-2 by sliding the transducer toward and away from R-2 until the signal reachesmaximum amplitude. Use DELAY control to position the peaked signal to the appropriate location on the horizontalbaseline. Using the RANGE control, repeat these steps until the peaked signals from R-2 and R-4 are located at therequired positions on the baseline. Repeat these steps until the peaked signals from R-2 and R-4 are located at therequired positions on the baseline.
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c. This method works for 45 degree transducers only: position the transducer along scale ‘‘C’’ and obtain a peak signalfrom the hole as shown in (see Figure 5-6). Distance is read directly off the scale. P-2 shows 2.5-inches; P-3 shows5-inches.
Table 5-9. Auto Calibration Procedures
AUTO CAL PROCEDURES:ANGLE BEAM TESTING I/W
1) COLD BOOT UNIT
2) SELECT LOWER LEVEL MENU WITH WHITE UP/DOWN ARROW
3) TOGGLE THRU LOWER LEVEL MENU UNTIL YOU SEE THE AUTO CAL COLUMN
4) SELECT:
A. Auto-Cal: On
B. Gate Logic: Positive
C. Measure: 0-1st
D. TOF: Flank
5) THEN TOGGLE TO ANGLE COLUMN:
A. Angle: 45.0
B. Thickness: 4.000 in.
C. X-Value: 0.563
D. O-Diam: Infinity
INSTRUMENT SETTINGS
BASIC RECEIVER PULSERGain: 40 dB Gain: 40 dB Gain: 40 dB
Range: 5.000 Frequency: 2-8 MHz Pulser: Single
Mtl-Vel: 0.1320 Damping: 50 Reject: 0
Delay: 0.000 Rectif: Full Rep-Rate: High
GATE S-CAL MEMGain: 40 dB Gain: 40 dB Gain: 40 dB
A-Thrsh: 20% Cal: Recall: Off
A-Start: 1.000 A-Start: 1.000 Set:#1
A-Width: 3.750 S-Ref: 2.000 Store: Off
TCGGain: 40 dB
DAC/TCG: Off
A-Start: 1.000
DAC Echo: 0
6) Select S-Cal menu
7) Press Cal left/right key simultaneously, ″REC 0″ will appear.
8) Confirm S-Ref thickness is two inches (2.0″) and select IIW standard.
9) Place transducer on standard as shown in (Figure 5-6) to pick up 2-inch reflector. Ensure the back reflection goesthru the gate by adjusting the gain.
10) Press the right arrow key next to cal, ″REC 0″ will change to ″REC 1″ and S-Ref will change to 4.000 inches
11) Confirm S-Ref thickness is 4-inches (4.0″).
12) Place transducer on standard again, ensuring that back reflection passes thru gate, adjust gain as needed.
13) Press the right key next to Cal twice, and the unit will calculate the material velocity, and zero, probe delay(record settings for future use).
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Figure 5-6. Angle Beam Distance Calibration with IIW Block
Table 5-10. Angle Beam Distance Calibration
Angle Beam Distance Calibration IIW
Calibration Proceduresparagraph 5.1.6
1) Leave function keys set as they are from auto calibration procedures, confirm distance calibration.
2) NOTE: Use position P-1 to show amplitude signals from R-2, and R-4 only. Always expect a high P-Delay due tolucite wedge.
Angle Beam Point of Incidence IIW
Calibration Proceduresparagraph 5.1.7
1) Leave function keys set as they are from auto calibration procedures, and follow procedures to mark point ofincidence.
Angle Beam Angle Determination IIW
Calibration Proceduresparagraph 5.1.8
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Table 5-10. Angle Beam Distance Calibration - Continued
1) Leave function keys set as they are from auto calibration procedures, and confirm angle beam angle determination.
5.1.6.1 Angle Beam Distance Calibration (Miniature Angle Beam Block). This procedure works with angles over 45degrees.
a. (See Table 5-9 and Table 5-10) contains the set-up for the USN-52 ultrasonic unit; the instrument may need to beadjusted to obtain the required screen presentation.
b. Position the transducer at P-1 and then P-2 as shown in (see Figure 5-7). Obtain peak signals from R-1 and then fromR-2.
CAUTION
Ensure you are using the proper transducer and standard matched for the material you wish to inspect.
c. The angle beam metal travel at P-1 is 1-inch; at P-2, it is 2-inches.
5.1.7 Angle Beam Point-of-Incidence (Type 2 IIW Block). The point-of-incidence is defined as the center point of thesound beam exiting the transducer wedge. It is usually indicated by a mark on the side of the wedge at the point where animaginary line through the exit point of the beam intersects the side of the wedge.
a. (See Table 5-9 and Table 5-10) contains the set-up for the USN-52 ultrasonic unit; the instrument may need to beadjusted to obtain the required screen presentation.
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b. Move the transducer back and forth from the curved surface at R-4 (see Figure 5-8) until the peak signal from R-4 isobtained.
c. The transducer point-of-incidence now coincides with the line marked ‘‘0’’ on the block. Mark the point-of-incidence on the side of the search unit.
NOTE
Marking (etching) by mechanical means MAY damage the sensitive transducer.
Figure 5-8. Point of Incidence Determination with IIW Block
5.1.7.1 Angle Beam Point of Incidence (Miniature Angle Beam Block).
NOTE
The point-of-incidence as determined in accordance with these procedures MAY NOT correspond with the point-of-incidence placed on the transducer by the transducer manufacturer. Once the point-of-incidence is located andmarked on the transducer, distance determinations shall be done using reference blocks made of the samematerial as that to be inspected, or a material of approximately the same shear wave velocity if the same materialis not available. For example, if inspecting titanium, an aluminum block may be used if a titanium referenceblock is not available.
a. (Table 5-9) contains the set-up for the USN-52 ultrasonic unit, the instrument may need to be adjusted to obtain therequired screen presentation.
b. Move the transducer back and forth from the curved surface at R-2 (see Figure 5-9) until the peak signal from R-2 isobtained. Once the point-of-incidence is located and marked on the transducer, distance determinations shall be doneusing reference blocks made of the same material as that to be inspected, or a material of approximately the sameshear wave velocity, if the same material is not available. For example, if inspecting titanium, an aluminum blockmay be used if a titanium reference block is not available.
c. The transducer point-of-incidence now coincides with the line marked ‘‘0’’ on the block. Mark the point-of-incidence on the side of the transducer.
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Figure 5-9. Point of Incidence Determination with Miniature Angle Beam Block
5.1.8 Determining Angle Beam Misalignment (Skew Angle). Skew angle is a measure of the misalignment anglebetween the ultrasonic beam and the search units’ axis of symmetry (see Figure 5-10).
a. (Table 5-9) contains the set-up for the USN-52 ultrasonic unit; the instrument may need to be adjusted to obtain therequired screen presentation.
b. Place the Type 2 IIW block flat on the side and adjust the search unit to maximize the echo from the other corner ofthe block (see Figure 5-11). The corner of the block where there are no scale engravings SHALL be used.
c. Place a protractor on the block, as shown in (see Figure 5-11) and measure the skew angle. The skew angle of newand used ultrasonic transducers SHALL be maintained within 2-degrees of the probe symmetry axis.
a. (Table 5-9) contains the set-up for the USN-52 ultrasonic unit, the instrument may need to be adjusted to obtain therequired screen presentation.
b. Position the transducer on scale ‘‘A’’ or ‘‘B’’ as shown in (see Figure 5-12). Move the transducer back and forthuntil the peak signal from the hole is obtained.
c. Read the refracted angle from the position on scale ‘‘A’’ or ‘‘B’’ coinciding with the point-of-incidence. In (seeFigure 5-12), P-1 shows 60°; and P-2 shows 45°. The refracted angle SHALL be + or - 2-degrees of the originaldesign.
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Figure 5-12. Angle Determination with Type 2 IIW Block
a. (Table 5-9) contains the set-up for the USN-52 ultrasonic unit, the instrument may need to be adjusted to obtain therequired screen presentation.
b. Position the transducer on scale ‘‘A’’ or ‘‘B’’ as shown in (see Figure 5-12). Move the transducer back and forthuntil the peak signal from the hole is obtained.
c. Read the refracted angle from the position on scale ‘‘A’’ or ‘‘B’’ coinciding with the point-of-incidence. (seeFigure 5-13) (and P-2 shows 700)
d. Angle beam determination can also be done with the miniature angle beam block (see Figure 5-13).
Figure 5-13. Angle Determination with Miniature Angle Beam Block
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CHAPTER 6RADIOGRAPHIC INSPECTION
SECTION I RADIOGRAPHIC INSPECTION GENERAL PROCEDURE
(NOT APPLICABLE)
6-1
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SECTION II RADIOGRAPHIC INSPECTION GENERAL PROCEDURE
6.1 RADIOGRAPHIC INSPECTION PROCESS CONTROL.
6.1.1 Individual Safelight Evaluation Check.
a. X-ray a piece of 14x17 Class 4 X-ray film until a 1.5 density is achieved. Note the distance, time, kVp, and mA used.Expose another piece of the same type of film for use in the safelight test and leave unopened until ready to performthe test. (Class 4 = Kodak AA, Fuji IX100, or Agfa D7)
b. Turn off, disconnect, or remove all safe lights from the dark room except the one to be tested.
c. Turn off remaining safelight and open the exposed 14x17-inch sheet of class 4 film in complete darkness.
d. Cover the entire sheet of film with cardboard or other like type of material; place it in the working area at least fourfeet under the safelight.
e. Uncover 2.5-inch section of film, turn on the safelight and expose it to the safelight for 6-minutes. After 6-minutes,uncover another 2.5-inch and expose for 3- minutes. Repeat the procedure for 1-minute, 30 seconds, and 15 seconds.Be sure to leave the last section covered and completely unexposed.
f. Turn off safelight and develop the film in complete darkness.
g. Take density reading for all the sections on the X-ray film and compare to the last, unexposed section. The sectionwith the least amount of measurable density change is the maximum allowable time undeveloped film may beexposed to this safelight. If that time is less than 4-minutes and 45-seconds, the safelight does not meet minimumrequirements.
6.1.2 Collective Safelight Check.
a. Follow the above procedures with the following exceptions: turn on all the safelights in the exposure room whenperforming step e and expose the film to safelight at the location where film is normally opened.
b. If the test results do not meet minimum criteria, follow the guidance below.
(1) Replace safelight filters that are faded, cracked, scratched, not designated for industrial radiographic film, or donot fit properly.
(2) Replace safelight bulbs exceeding the wattage recommended by the manufacturer.
(3) Replace unserviceable safelights, such as those emitting ambient light.
(4) Eliminate or reconfigure uncontrollable ambient light sources such as doorways, ventilating and heatingducts/vents, faulty film pass through box, building structural cracks, and holes around pipes and electrical wiring.
(5) In the event the individual safelight tests are all within acceptable tolerance, but the collective safelight test isunacceptable, investigate the validity of the individual safelight tests. If the results of these tests are correct,reduce the number of safelights in the darkroom.
6.1.3 Developer Testing.
a. Expose a piece of class 4 film and a step wedge to X-rays. (Class 4 film = Kodak AA, FUJI IX100, AFGA D7) Fivesheets of X-ray film may be exposed at the same time when using a steel wedge and three sheets when an aluminumwedge is used. Expose the film sufficiently to present the whole range of densities from the step wedge.
b. Cut the film into thin strips and seal securely to prevent exposure to light.
c. Process the first strip with fresh developer. Save the strip to use as a reference.
d. Once a week during the life of the developer, process another strip and compare the resulting density reading with thereference strip.
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e. If a variation in excess of 0.3 density units occurs, the developer will need to be changed.
f. Repeat the process each time the developer is changed.
6.1.4 Fixer Control. Fixer control is a measurement of the replenishment rate of an automatic processor. Follow theinstructions in the owner’s manual for making this measurement. Generally, a graduated cylinder is used to capture the fixerbeing pumped into the tank while processing one piece of 14x17 film. The amount should measure between 170 and 190 ml.
6.1.5 Safelight Filter Check. Check safelight filters for fading, cracks, crazed, improper fit, scratched, or filters notdesignated for industrial radiographic film. Replace filters as required.
6.1.6 Interlock Operational Check. An inspection of the x-ray interlock system is required daily if the X-ray facility isused every day. For facilities not used every day a prior to use inspection is required. The interlock operational check SHALLbe performed at least every six-months for seldom-used facilities. AFTO form 135 may be used to document the interlockoperational check. The operational check will include as a minimum the following checklist items:
• Do all interlock door switches stop X-ray production if the door is opened?• Are all rotating beacons operational?• Does the audible alarm sound for 20 seconds prior to X-ray emission?• Are all emergency stop buttons unobstructed and operational?• Is the shielded radiation utilization log current? Does it include a facility survey, local operating procedures, emergency
procedures, and ORMs within arms reach of the console?• Does all personnel involved with X-ray operations have a TLD and a PAD, DAD, or equivalent approved direct reading
dosimeter affixed to the trunk of the body and outside of their clothing?• Does the shielded facility have legible and unobstructed warning signs inside and outside?• Is at least one calibrated and operable survey meter ready for X-ray operations?• Has the AFTO form 140 been documented for the battery and operational check?
6.1.7 Survey Meter Operational Check. The survey meter SHALL be checked by the user with a radiation check sourceprior to the first monitoring operation of the day, and at two-week intervals for instruments not in daily use.
