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GUIDELINE FOR INFRARED INSPECTION

OF ELECTRICAL AND MECHANICAL SYSTEMS

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tINFRASPECTION INSTITUTE

197,1 SHELBURNE ROAD, SUITE CSHELBURNE, VT 05482-7174 USA

PH: 802-98S2500 FAX: 802-985-2726

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FOREWORD

outlines the

o*iuiriGi.na pro""or.rr"" tor h.nloqraphi" infrared inspections' lt is one of the Guidelines

i"oL-""" ""0 "ip*ds upon the '1988 -document, Guidelines for Soecifvino and Performino

red lnsoections.

rr Guidelines available from the Infraspection Institute are:

Aoplicalion

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Temoerature Measurement

;e Guidelines reDresent the work of many practicing, infrared thermographers and other)rls. We acknoiledge them for their valuable contnbulrons'

Paul Grover. DirectorInfraspection I nstituteJanuary, 1993

Transmittance

Cameras

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)GUIDELINE FOR INFRARED INSPECTION

OF ELECTRICAL AND MECHANICAL SYSTEMS

TABLE OF CONTENTS

PART 1: GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 2

PAFIT 2: TEMPERATURE CFtITERIA FOR ELECTRICAL SYSTEMS. ...."." Page 7

I- eART 3' TEMeERATURE cRtrERlA FoR MEoHANIoAL SYSTEMS... ..... Page 1 1

pART4: REFERENCES.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 15

Firsl Edition, CoPyrighl 1993lnlrasDection Institute. Inc..1971 Shelbume Road, Suite C

Shelbume, VT 05482-7174 USAPH: 802-985-2500 FAX: 802-985-2726

This document mav be reproduced for personal use and not lor prolil, without charge,provided you include all of the copyrighl and address intormation listed above. Failure toinclude ttiis inlormation with any reproduction is an infringement of the copyright and subjectto legal action and consequences.

In no event shall Infraspection Institute be liable to anyone for sp€cial' collateral,t Incidental or consequehtial damages in conjunction with or arising lrom use of this

Guideline.

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) PART 1: GENERAL

1.0 Guideline Purposes

The purposes of this Guideline are lo:

1.1 provide a common documenl for the end user to specify infrared inspections and theinfrared thermographer to perform them.

1.2 list lhe joint responsibilities of the end user and the infrared fhermographer that, whencanied out, will result in the safest and highest.quality inspection for both.

1.3 outlinelhe specific content for documenting qualitative and quantitative inftaredInspecltons.

1.4 provide criteria for evaluating the severity of an exception.

2.0 Definitions

For the purpose of thiS Guideline,

2.1 a guideline is a sel of specitications which detine the purposes, scope and conlent otaproceoure.

E 2.2 qualitative infrared thermography is the practice of gathering information about astlucture, system, objecl or process by observing images of infrared radiation, andrecording and presenting lhat information.

2.3 quantitative infrared thermography is the practice of measuting temperatures of theobserved oatlems of intrared radiation.

2.4 the end user is the person requesting an infEred thermographic inspection.

2.5 an infrared inspection is lhe use of inhared imaging eguipment to provide specificlhermal information and relaled documeniation about a sfucture, system, object orDrocess,

2.6 an intrared thermographer is a person who performs and documents an infraredinspection.

2-7 a qualified assistant is a person provided and aulhorized by the end user to performlhe tasks required by lhe infrared lhermographer. Hey'she is knowledgeable of theopeEtion and history of the equipment to be inspected and is trained in all the safetypractices and rules of lhe end user-

2.8 an exception is an abnormally warm or cool @nnector, conduclor or component thatmay be a potential problem for lhe end user.

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I3.0 Scope of the Guideline

4.O Responsibilities of the lnfrared Thermographer

The purpose of an infrared inspeclion is to identiry and document exceptions in the enduseis eleclrical and/or mectranical systems.

3.1.1 In eleclrical systems, exceptions are usually caused by loose or deterioratedconnec{ions, short circlits, overloads, load imbalances or faulty, mismatchedor improperly-installed components.

3.1.2 In mechanical systems, exceptions are usually caused by friction due to improperlubrication, misalignment, wom components or mechanical loading anomalies.Exceptions in insulation systems are usually caused by missing or deterioratedmalerials, improper installation or insumcient amounts of material.

Providing opinions about the causes of these pattems, the integrity of the system orrecommendations for correclive aclions require knowledge and skills beyond those ofinfrared thermography.

3.2.1 lnfrared thermography will be presented as an inspedion technique to galherand presenl information about the system at a specific time.

3.2.2 Infrared thermography will not be promoted as a rcmedial measure.

3.2.3 An infared insoec{ion of elec{rical and mechanical svstems does not assureproper operatibn of suctr equipment. Other tests ana proper mainlenance arenecessary lo assure their reliable performance.

This Guideline supports -lhe procedures and specifications stated in NETA lvtTs-19891and MIL-STB-2194 (SH)'. However, compliance with this Guideline is independent ofcompliance wilh any other standard.

3.1

3.2

4.1

4.2

4.3

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Infrared inspec{ions will be performed when environmental and physical conditions suchas solar gain, wind, surface and atmospheric moisture and heat transfer are favorable togathering accuraie data.

The infrared thermographer will have sufficient knowledge of the components,conslruclion and theory of electrical and/or mechanical syslems to understand theobserved oattems of radiation

The infraredlhermg=grapher will use thermal imaging and/or measurement equipmentwith c€pabilities sufficient to meet the inspec{ion requirements.

The infrared thermographer will be accompanied by a qualified assistant who isknowledgeable of the equipment being inspeded.

Unless he/she is a licensed electrician, professional engineer, or has other equivalentqualifications, the inlrared thermographer will not perfoim any tasks that are nbrma ydone bylhese personnel. Unless so qualified and authorized by the end user, theInrareo tnermograpner

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4.5.1 will nol remove or replace covers or open or close cabinets containjng electrical ormechanical eouioment.

4.5.2 will nol measure eleclric loads of the eouiDment_

4.5.3 will. nol touch any inspected equipment and will maintain a safe distance f romsucn equrpmenr.

4.5.4 will comply with the satety practices and rules ot the end user.

4.6 When performing quantitative inlrared inspections, the infrared thermographer willassure that all temperature-measuring equipment meets the manufacttrers' standardspecif ications tor accuracy.

4.7 Allet repai, and when requested by the end user, each exception should be re-insDectedlo assure that its operating temperature is normal and the potential problem correcied.

5.0 Responsibilities'ot the End Uset

5.1 The end usdr willprovide or_help develop an inventory list of the equipment to beinspected in a logical and efficient route through the tacility.

5.2 The end user_will provide a qualified assistant(s) who is knowtedgeable ot the operationand history of the equipment to be inspected. This person(s) wilfaccompany the infraredthermographer during the inspection and, unless speci{ied otherwise, wiit be aualilied andauthorized by the end user to:

5.2.1 obtain authorizatjons necessary to gain access to the equipment to be inspectedand will notity operations personnel of the inspection activities.

5.2.2 open and/or remove allnecessary covers of cabinets and enclosures containinothe equipment to be inspected.

5.2.3 close and/or replace these cabinet and enclosure covers immediately alterinspection by the inlrared thermographer.

5.2.4 assure that the equipment to be inspected is under adequate load, createsatisfactory loadswhen necessary, and allow sufficient time tor recenly-energzedequipment to produce stable thermal patterns.

5.2.5 measure electric loads when requested by the infrared thermographer.

5.3 The end user takes full responsibility tor consequences resutting lrom actions taken, ornot taken, as_a result ol inlormation provided by an intrared inspection.

5.4 Alter repair, each exception.should be re-inspected to assure that its operatingfemperature is normal and the potential problem corrected.

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6.0 Documentation

6.1 The lhermographer will provide documentalion for all infrared inspections. Thefollowing information will be included in a written reporl to the end usen

0.1.1 the name and any valid certification level(s) and number(s) of the inharedthermographer.

6.1.2 the name and address of the end user.

6. 1.3 the name(s) of the assistanl(s) accompanying the infrared thermographer duringthe inspection.

6.1.4 the manufaclurer: modeland serial number of lhe infrared equipment used.

6.1.5 a list of all the equipment inspected and notations of the equipment notinspected on lhe inventory lisl

6. |.6 the date(s) of the inspection and rvhen lhe report was prepared.

6.2 \rvhen performing a qualitative infrared inspeclion, the infrared thermographet willprovide the following information for each exception identified:

6.2.1 the e)€c1 location of the exception.

6.2.2 a description of lhe exception such as its sllnificanl nameplate data, phase orcircuit number, raled voltrage, amperage raling and/or rotalion speed.

6.2.3 lvhen significanl, the environmental conditions sunounding the exceptionincluding the air temperature, wind speed and direclion, and the sky conditions.

6.2.4 hardcopies of a thermal image (thermogram) and conesponding visible'light imageof the exceplion.

6.2.5 the field-of-view of the infrared camera lens.

6.2.6 notation ofany windows, filters or external oplics used.

6.2.7 if desired, a subjeclive evaluation rating provided by the qualified assistant and/orend user representative, of the importance of the exception to the safe andcontinuous operation of the system.

6.2.8 any other informalion or special conditions lvhich may affect the results,repeatability or interpretiation of the exception-

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6.3 When performing.a quantitative.infrared_ inspection, the infrared thermographer willprovide the following additional information:

6-3.1 the distance from the infrared camera to the exception.

6-3-2 whenev€r possible, the maximum rated load of the exception and its measuredload al the time ot the inspeclion and

6.3.3 the percentage road on rhe exception, carcurated by dividing its measured toad bythe rated load-

6-3.4 the emissivlty,_reflecled temperature and rransmission varues used to carcurale rhelempeEture of lhe exception._

6.3.5 when gsing delta,T-temperature.criteria, the surface temperature o, the exceptionand of a defined reference and their temperature OmeiericJ oi6.3.6 when using absorute temperalure criteria, the surface lempe'ture otthe exceprionand the standard and lhe standard tempdrature(s) releren'ced-

6.3.7 if desired, an evaluation of the lemperature ieverity of the exceptton.

6.3.8 if^de^sjre4 -a^r-"1?ir_plgllyFlirq forlhe exception based on its subjeclive rating,remperature seventy ratlng or an ave|:tge of both.

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PART 2: TEMPERATURE CRITERIA FOR ELECTRICAL SYSTEMS

Delta-T Criteria

7.1 The infi'ared thermographer may use the following dett+T (temperature d,[.rqlcg)' critlti. to uvaiuate ifie iemperati.rre severity of anlxception. These deltaT criteria arereoorled as the temDeraturb rise of the exc-eption above the temperature of a definedreierence, which is iypically the ambient air temperature, a similar component under lhesame condilions or lhe maiimum allowable temperature of the component

N.E.T.A Maintenance Testino Soecificationsl, for eleclrical equipment

1) 1 to 3C": possible deficiency and waranls invesligalion.2) 4 to 15C": indicates deficienc]4 repair as time permits.3) 16C" and above: indicates major deficienq4 repair immediately.

Militarv Standard'�, for elec{rical equipment

1) 10 io 25C': comoonent failure unlikely but correciive measure required at next' scfieduled rotdine maintenance Deriod or as scheduling permits.

2) 25 to 40C': component failure probable unless conected.3) 40 to 70C': comoonent failure almost certain unless cotrected.4i ToCf and abovei component failure imminent stop survey. Inform cognizant

officers.

Experience-Based.3 for elec{rical and/or mechanical equipment

Any delta-T classification system based on experience, such as the following3:

1) O to 1oC': conective measures should be taken at the next maintenance period.2i 10 to 2OC1 conedive measures required as scheduling permits.3) 20 to 40C': coneclive measures required ASAP.4) 40Cl and above: conective measures required immediately.

Motor Coresr (on test bencfi, not in service):

1) o to loco: no exception likely.2) | 0 to 20C': possible exception, consult motor core test data.3) 2oC9 and above: exception likely.

Absolute Temperature Criteria

8.1 The infrared thermographer may use absolute temperature criteria based on the followingANSI, IEEE and NEMA or other standards to idenlify electrical system exceptions.

8.2 All temperatures of the following slandards are specified in Celsius as follows:

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AmbienVRated Rise/Maximum Allowable

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When the exception is healing several adjacenl componenls, lhe lowest temperaturecomponent specification should be used.

Example: You are inspecling a heating lerminalthat connects an insulatedconductor to a circuit breaker. The component with the lowest temDeralurespecification should be used

When sevelal ditferenl temperatures for similar equipment are given in the referencedsrirndards, tne towest tem.peratures (most conseryative) are listed, lf an exceptiontemperature exceeds the lisled maximum allowable absolute temperature limit; it couldb^e operatjng a.t a temp€ralure lover than a higher (less conservative) specificaiion.uonsutl Ine relerenceo sEndard(s).

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8.5 When lhe infrared thermographer is unable to determine the class of insulation orequipment being ins_pected, hey'she should use the lowest temperature (mostmnservative) specifi cation wilhin lhe component grouping.

Example: You are inspecting an insutated wire thal has no visible markinos.Use the lowest lemperature specification for any conductor insulation.

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8.6 Unless noted.otheMise, lhese -absolute lemperature crileria are based on equipmentoperating at the qtated ambient temperature and at .l OO% of their rated load, fhefollowing formula'can be applied to these absolute temoerature criteria to oive aconected maximum allo\,\Eble temperature (l"Max""") foi the reduced operjting load andactual ambient temperature of the exceDtion:

Tmax* : (T,hdd"J(4JA.,.)' " + Tamb*

Tmax* = conecled maximum allowable temperature

T.bd,8. = raled temperalure rise (from standard)

A,* = measured load, in amperes

A,"l"d = rated load, in amperes

Tamb@ = measured ambient temperature

8.7 Absolute TempeEture Criteria:

Conductors (lowest temperature criteria):

Bare conduclors6,.in ftee air----.......--..,Eare oonouclors, tn endosure........--- -.------.....4U3On0Bare conducloE, enclosure surface.. .....-.---...4Ot2Ot6O

Insulated conductorsT, in free air-.--....- .---------.30/30/60Insulated conductors, in enclosure-.--.. ...........30/30/60lnsufated conductors, enclosure surface.........,...,......--................-3Ol2Ol5OInsulated conductors, in sun.--..........--. ..........-50/10160

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Conductor Insulationst:

T,TWR,RWRU..... ...........30/30/60THWPofyethylene,XHHqRH-RW..... ..............30t45ft5Vamished Cambric. ............3U47mPaper Lead............ ............-30/50/80Vamished Polyester.......-.----..---........... .-.-.-.....30/55/85THH,Cross Linked Polyethylene,EthylenePropylene ---.---....30/60/90Silicone Rubber..... ..---..--...301951125

Connectors and Termin?lions (lowest temperature criteria):

Metafslo, silver or silver alloy-............... ...........4O14O1aOMetals, copper, copper alloy or a1uminum.....................................40/50/90Metals, afuminum a11oy......................... ..-...-...521531105

Overcunent Devicess (lowest temperature criteria):

Ciranit breakers. molded case.......,.. ................40120160Cirqrit breakers, all others.....,.......,..... .............408OnOFuses..................... -.........--4U30ftO

and Suoportsro (lowest lemperature criteria)...,..............................4OgonO

Bushinosrl (lowest lemperature criteria):

Transformer, lower end............... .....................40/55/95Cirojit breaker, lower end..........,.... .................40/40/80Exlemaf terminal... .............40130170

Coils and Relavssrl

Class 90................ .............40/50/90class 105.............. .............40/65/i 05Class 130.............. .............40/90/130Class 155.............. -.-.-........4on1 15sClass | 80.....-........ ............4Ot't4OnAOcfass 220.............. .............4onaot22oAC Motors. Field Wndinosr3:

1.0O SF, class A... .....-.......40/60/i OO'f.00 SF, cfass 8.... .............4Ot8Ot12O1.00 SF, class F..... ............4\t.t15t1451.00 SF, cfass H.... ............4)t125t1651.15 SF, class 8.... -.----.......40/90/.1301.15 SF, cfass F.... -------......40t'l1st1ss

Note: Casing temperatures may be lower lhan these specified windings temperatures.

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DC Motors and Generators. Windings'3:

1.00 SF, class A..... ............40nU1101.00 SF, cfass 8..... ............40110011401.OO SF, class F..... ......---..40/130/1701-oO SF. ctass H.... ...........-.401155/195

1-25 SF (2hr), class 8................... -......--.--.......4O14O42O1.25 SF (2hr), class F.......-........... ...................40/1'10/'150

Note: Casing temperatures may be lower than these specitied windings temperatures.

Cylindrical Rotor Synchronous Generators. Air Cooled. Casino'3:

Class B.................. -----........4OnOn1OClass F.............-.-.- -...........40/90/130Class H-................. -.--.......4O1'l' lOl15O

Transformers, Distribulion and Powerr'r5r5:

Dry type, class 105, windings......... .................30/55/85DrV tirbe. class 150. windinqs.....-... .................30/80/110Drlti,be.ctass'l85.windinas......... .................30/115/145Drl tlbe, class 220, windin9s............... ...........30/150/180

Oil cooled,55C" rise, casin9................ ............30/55/85Oil cooled, 65Co rise, casing.... .......................30/65/95

Notes: 1. OiFcooled casing temperatures measured near top of liquid in main tank2. Most 55C" rise transformer built before 1962.3. For specialty transformers (other than power and distribution) or other

liqui&cooled equipment, as specilied on lhe nameplate.

8.8 A detla.T criteria system may be used in conjunction with these absolute temp€ratutecriteria to rate the t'emperatuie severity of an exceplion above the maximum allowabletempeEture. Use the delta-T crileria listed in section 7.1.

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PART 3: TEMPERATURE CR|TER|A FOR MECHANTCAL SYSTEMS

9.0 Delta-T Criteria

9-1 The infrared thermographer may use detta-T (lemperature difference) cdteria to rate thetemperature severity of mecfranical system exceptions. These delta-T siteria areusually-reported as the temperalure rise of the exception above the tempeialure of adefined reference. Use lhe della-T c.iteria listed in sec{ion 7.1.

9.2 By taking multiple measurements over time of similar components under similaroperating and environmental condilions. statistical analysis can be used lo setoperational limits for trending and predicting the temperatu're performance of thesecomponents.

10.0 Absolute Temperature Criteria

10.1 The infraredihermographer may use absolute maimum allowable temperature criteriabased on published standards to identry mechanical system exceptioni.

10.2 When an exception is heating severaladjacent system components, the componenthaving the lowest lemperature specification should be referenced.

E)€mple: You are inspecting a bearing of a motor. The applicable adiacentsystem components are the seals and the lubricant The component (bearing,seals or lubricant) having lhe lowesl lemperature specificalion'should bereferenced.

Note: In most cases, lhe lubricant will have the lowest temperature specification.

10.3 When unable to determine the type of bearing, lubricanl or seal, the inft.aredthermographer should use the lowest component temperature specification within theapplicable group.

E)€mple:.You are inspecting a bearing. you identify the bearing and lubricanttypes and temperalure limits, but you do not know the type of seal. From thelist, selec{ the lowest applicable temperature specificati6ir for any seal.Compare your measured bearing teinperature-to the lowest of ttie threecomponenl temperatures (the bearing, lubricant and seal).

'| 0.4 The infrared thermographer often cannot direc{ly measure the surfac€s of lhecrmponents in lhese specification lists. Care and qood iudoment must be used whenapplying these specifications to actual field temperatureheEsurements.

10.5 Unless.noted, temperature specifications are based on equipment operating at 1Oo% oftheir rated load/speed. All temoeratures are in Celsius-

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