Pipe Fittings and Piping Auxiliaries

Pipe, Fittings, and Piping Auxiliaries Page 1

COURSE OBJECTIVES

COURSE TERMINAL OBJECTIVE

Given work control documents, the Apprentice Maintenance Mechanic will Install and Rework piping and piping auxiliaries, as demonstrated by passing a written examination with a minimum grade of 80% or better, and satisfactorily completing the Lab Practical Evaluation.

LESSON TERMINAL OBJECTIVE

Given a maintenance activity involving piping and/or tubing, the Apprentice Maintenance Mechanic will Describe the purpose, characteristics and properties of piping and tubing, as demonstrated by passing a written examination with a minimum grade of 80% or better.

LESSON ENABLING OBJECTIVES

EO01 State the purpose of piping systems.

EO02 Describe the basic fluid flow types and characteristics.

EO03 Describe how piping is identified.

EO04 State the differences between piping and tubing.


EO01 State The Purpose Of A Piping System

A piping system must be able to safely supply uncontaminated fluid at desired pressures and temperatures to the proper location.

Safely means the potential for personnel injury or equipment damage must be minimized.

Uncontaminated means the fluid will not get any unwanted impurities during the transfer process.

Fluid will be defined here (and throughout this course) as anything that will flow through a pipe. Primarily this refers to liquid and gas, but can also include slurries (solids suspended in liquid).

The pressures and temperatures must sometimes be controlled. This may mean that the fluid temperature is to be raised, or the temperature is to be lowered, or the temperature of something must be maintained constant. The fluid pressure may need to be raised, lowered, or stored for later use. These are all functions of a piping system.

There are two (2) basic types of fluid systems.

One is the open loop. It has both a source and a destination. The pressure within the system is primary controlled by the pressure at the source and/or the destination. Examples of an open system include the Circ water system (where the source and destination are sometimes the same location) and the Chemical addition systems.

The other fluid system type is the closed loop. It has no specific source or destination but rather the fluid recirculates in a loop. The pressure in a closed loop must be controlled by something within the system like a pressurizer. Examples of a closed loop include the Rx Coolant System, and the combined Main Steam, Condensate, and Feedwater systems.


EO02 Describe The Basic Fluid Flow Types And Characteristics

The basic types of fluid flow are laminar and turbulent.

In Laminar flow, the molecules move in even layers. The center layers (the one farthest from the pipe) move the fastest, and the outer layer (the one touching the pipe) virtually does not move.

In Turbulent flow, the molecules move somewhat randomly within the flowing fluid. The flow moves around like water does in a stream with lots of rock, not straight like it does through a concrete irrigation ditch.

Each of the types has characteristics unique to the flow type which make it more or less desirable for certain applications.

Laminar flow, being an even type of flow with the layered effect has less resistance to flow it’s like driving a car with a tail-wind. Because of this, you can use smaller diameter piping to achieve the same capacity to move fluid. However, the layers tend to insulate heat transfer to the next layer, so this type of flow is not good if heat transfer is desired. To create laminar flow requires smooth even surfaces of straight pipe because they are most likely to create the laminar flow. This requires greater care in fabrication and erection of the piping to both create and maintain the laminar flow within the pipe.

Turbulent flow is much better at heat transfer as the warmed (or cooled) molecules can move directly into the main stream of fluid rather than having to transfer the energy through layers. Turbulence also creates better mixing of two or more fluids. On the down side, it has a greater resistance to flow, like driving a car with a cross-wind or a head-wind. The turbulent flow also causes erosion of piping surfaces. Turbulent flow is caused by rough surfaces or protrusions on the piping surfaces, or changes in fluid direction as in corners and tees. Turbulence can be especially high when there is insufficient time for flow to become laminar before a 2nd change in direction such as when 2 elbows are very close together.

Piping systems must be designed and maintained to establish the desired flow type.

Erosion/Corrosion phenomena

(NRC IN 86-106)

At the Surry Power Station on Tuesday, December 9, 1986 at 2:20 p.m., both units were operating at full power when the 18" suction line to the main feedwater pump A for Unit 2 failed catastrophically. There were eight workers replacing thermal insulation on a nearby line. All were burned by flashing feedwater.

All eight were transported to area hospitals. Two workers were treated and released. Four of the remaining six workers subsequently died.

Upon evaluation of the failure, it was determined that erosion/corrosion or flow-assisted corrosion was the culprit. The corrosive action is initiated by the erosion of the protective

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metal oxide layer. Conditions which contributed to the failure in this case included piping design (2 elbows close together), fluid dynamics (the non-viscous fluid like high temperature water/steam more easily moves to turbulence), the piping material (the material was soft enough to be susceptible to the erosion and subject to corrosion in the base metal), and the water chemistry (insufficient corrosion inhibitor).

In addition to the immediate personnel injuries, there was the potential for greater problems because of the effects on the plant safety. Security card readers in the area failed, and three fire suppression systems (water, CO2 and Halon) were rendered out of service.

To follow up, in the September, 1988 outage, Surry inspected piping and discovered that pipe wall thinning had occurred more rapidly than expected. On the suction side of one of the main feedwater pumps, an elbow that was installed during the 1987 refueling outage lost 20% of its .500" wall in 1.2 years. This wall thinning was continuing in both safety and non-safety related piping.

Related SOER 87-3 Piping Failures In High Energy System Due To Erosion/Corrosion

Wall thinning in carbon steel pipes due to erosion/corrosion, has resulted in several pipe ruptures in high energy system greater than 200 degrees. Some of the conditions necessary to cause Erosion/Corrosion damage include:

• Susceptible pipe material such as carbon pipe

• Piping geometries that induce high local turbulence levels

• Flow restrictions (valves, nozzles)

• Other variables such a temp and water chemistry

Typically affected systems include the feedwater system, HP drains and extraction steam drains.

Actions at the plant

At the plant we evaluated the piping for the problems noted by INPO and engineering identified potential locations for erosion/corrosion damage. The most severe potential spots were calculated. If any changes are made in the system we would be required to reperform the analysis. Some seemingly minor changes which have created problems in the industry due to the lack of analysis include changing the normal flow rate or the system temperature.


Potential problem spots are periodically inspected ultrasonically for wall thickness. The results are trended to determine the timing for replacement requirements. The piping is then replaced as necessary.

Within a piping system these stresses exist in the following forms

Hoop Stress: A tensile stress around the circumference of the pipe due to internal pressure of the fluid.

Longitudinal Stress: A tensile stress caused by the pressure acting on the ends of the piping (Elbows, e.g.). This force tries to stretch the pipe.

Weight Stresses: Some tensile and some

compressive stresses exist simply from the weight of the piping and its contained fluid. The stresses are opposite (top to bottom) at the hangers from what they are between the hangers. Notice that some stresses are not designed into piping such as the weight of people stepping on them, the use of piping for rigging support, and the use of piping as an electrical cable pulling anchor. These could overstress and damage the piping.

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EO03 Describe How Piping Is Identified

Piping Identification

All piping is purchased with marking in ink by the manufacturer. For Q-class piping, the heat code marking must be transferred to any pieces of pipe which are cut off of the main piece. This transferred heat code must be etched with a vibro-etcher, not just painted on. All other required information should also be transferred to the new piece. This would include piping size, schedule or nominal wall thickness, and the Code to designate material type.

The following is a typical marking for piping, taken off of a pipe here at the plant.

ASTM-ASME SA106 GRADE-B 1 1/2

SCH 80 17-24’ 2500 PSI HTKT-2603 SEAMLESS USA GST

The piping Heat Number identifies the batch of the steel fabrication. This makes it possible to trace the piping material back to its original processing.

Other information which is often included in the markings are the Type of pipe (Seamed or Seamless), Piping lengths as manufactured, Pressure rating of piping, and Piping manufacturer.

Sizing of pipe (Diameter & wall thickness)

Pipe size is based on the nominal (approximate) inside diameter for 1/8" to 12" piping. For piping 14" or greater, it is based on the nominal outside diameter. The outside diameter is constant for a specified pipe size for all schedules (wall thicknesses). The inside diameter changes as the schedule changes.

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12”14”All

Sizes


EO04 State The Differences Between Piping And Tubing

The following items are a general comparison between piping and tubing.

• Tubing is essentially a specialized piping

• The geometric shape of both is essentially the same

• The manufacturing processes are similar

• Dimensional specifications will vary for tubing depending on the specialized service. Air conditioning and refrigeration are a different service than domestic water for example. There is not a single standardized schedule as there is for piping.

The primary specific difference between piping and tubing is the controlling dimensions. We can especially compare I.D. and O.D. controls.

• Piping is sized by nominal I.D. through 12”

• Tubing is sized by nominal O.D. through all sizes

Most tubing is required for specific purposes which require greater precision of manufacturing. Tubing outside diameter is generally more exacting than piping as is also the inside diameter.


Wall thickness specifications will vary depending on service usage. Using domestic water as an example, copper tubing has the following dimensional specs.

Type "M" Copper is light walled (for interior plumbing, heating and underground use). The wall thickness is .025” for 1/2” tubing.

Type "K" Copper is heavy walled (for house heating and normal water conditions). The wall thickness is .049” for 1/2” tubing,

Lengths of tubing are not standardized. Tubing lengths can be 3' to 300' depending upon customer requirement. Soft tubing can even come in coils of many hundreds of feet in length.

Tubing Identification

Most of the identification on tubing is the same as that on piping. It includes the Manufacturer’s name or trademark, the materials or specifications manufactured to, the pressure ratings, notation of seamed or seamless tubing, the heat number, and the tubing size. The tubing size is a little different, because it not only names the nominal O.D., but lists the specific I.D. or the wall thickness.

The following is an example of tubing marking from some tubing at the plant.

ASTROLUSTER BY TC-S SML. CD TP.304 .375 OD. X .065 MIN. WALL

HT. OA0260 Spec. ASTM A0213 A-655 CL.2 ANNEALED

The advantages identified here are generalities. They apply to most tubing and piping comparisons because they exemplify the qualities requested in tubing. Remember, tubing is simply specialized piping. Generally tubing has the following advantages over piping.

• Greater flexibility and fatigue resistance so it can be used where shock or repeated thermal expansion and contraction are required. , or for attaching piping runs (which have a lot of thermal growth) to a rigidly mounted instrument. Also for within homes, where water lines are repeatedly turned on and off.

Tubing minimizes joints. You can have long runs without joints to aid in flow characteristics. The flow characteristics are also improved by the closer tolerances and the improved surface finish generally used in tubing manufacturing,


LESSON 2 TERMINAL OBJECTIVE

Given a maintenance activity involving pipe and tube joints, the Apprentice Maintenance Mechanic will describe the type and identify the inspection, rework and makeup criteria for pipe and tube joints, as demonstrated by passing a written examination with a minimum grade of 80% or better.

LESSON 2 ENABLING OBJECTIVES

EO01 Describe the types of piping joints.

EO02 Identify the inspections performed on a welded joint

EO03 Describe the basic components of a flanged joint

EO04 Identify precautions when disassembling a flanged joint

EO05 Describe how to preload a joint using a torque wrench


E001 Describe types of Piping Joints

Threaded

Physical description: Threads are cut on the outside of the piping ends. Fittings are purchase, cut on the inside with threads. The threads are tapered, and the seal is created by the fit of the threads.

Uses and limitations: Various uses including domestic water, compressed air, and natural gas. It requires special tools to fabricate threads. It requires heavy walled piping to accept the thread depth without decreased the pressure rating. It is for medium pressure applications. It is very rigid, allowing no flexibility for misalignment or movement.

Flanged Joints

Physical description: A flat surface is on the ends of each pipe. A gasket is generally placed between the flat surfaces or flanges. They are held together with bolting material. The flange may be cast or forged integrally with the nozzle neck or vessel or pipe wall or it may be welded (called a Welded-Neck flange) to the pipe.

Uses and limitations: They can be used in very high pressure applications. Piping material where it connects to the flange can be as heavy as desired. The neck can taper almost to the pipe-wall thickness. It is very rigid with no misalignment or axial flexibility.


EO02 Describe How To Make Up A Threaded Type Joint

Physical Description of Piping Threads

The following three terms are used in describing the threads.

Crest - Top of the thread

Root - Bottom of the valley between two threads

Truncation - Truncation is the flattened area of the crest and the root. It reduces the stress points naturally created by the geometry of threads.

Threads are cut on the O.D. of the pipe & I.D. of fittings. These threads are tapered to the same angle on both the pipe and the fitting. The fittings will be purchased already threaded. All the threads must be smooth, clean and properly cut to provide a perfect fit.

Cutting Pipe Threads

Pipe must be threaded by hand or with a machine. The cut is made with a “die” which is fitted with 4 to 6 thread “chasers” which are the cutting tool inserts. The front or cutting edge of chasers must be facing the right way. For steel pipe, the lip angle on the leading edge will be 15º to 20º. The lip angle is the angle between the front face of the chaser and the actual cutting edge.

The four (or six) chasers are not identical. They are numbered 1 though 4 (or 1-6) to get them in order. They must contact the same point on the piping in reverse numbered order as the threads are being cut. They will appear numbered clockwise when viewed from the narrow end.

Cut the threads. Begin with the unthreaded side of the die (the chaser and head assembly) so the threads will be straight. Apply cutting fluid during the cutting. Stop cutting when the die is fully threaded onto the pipe. No more than one thread should go through the die.


Thread Cutting Oil

Cutting oil provides cooling to the cutting surfaces and lubricates the dies or chaser. It also assists in chip removal.

Checking the cut threads

Ream out any burrs which may have formed on the inside during the cutting process. Ensure no chips remain on the pipe prior to connecting the piping. Use a fitting and hand thread onto the pipe to verify the pipe is properly cut and to clean the threads.

Joining Threaded Pipe

This is a general description of the process. Apply thread sealant to male pipe threads. Begin making up the joint by hand to determine the proper thread engagement. Finish tightening the joint using a wrench. You should have 3 to 4 partially cut threads exposed.

Pipe Thread Sealants

You must exercise precautions when applying sealants to piping joint. Some sealant has mixed with the process fluid or with contaminants to cause failure of equipment in the past. One example is with the air check valves on the MSIVs & FWIVs. Fyrquel & thread sealant combined to cause several of the check valves to fail.

To help prevent the above problem, DO NOT apply sealant to the last 2 threads on the end of the pipe and ensure the sealant is compatible with the process fluid.

Some common sealants include:

• “Pipe dope”: This is a pasty thread sealant which hardens. It is made by various manufacturers under different names and chemical makeups.

• Teflon tape: This is not for general use. The CUP requirements states: is not for use in the containment building or the fuel building or in contact with the process fluids in the FW, SG, MS, CD, etc. systems. See the MSDS for the specific precautions if in doubt.


EO03 Describe The Basic Components Of A Flanged Joint

A flanged joint is one with two flat surfaces perpendicular to the piping axis (flanges). They are held together tightly enough (by bolting material) to create a seal. They may have a material between them to facilitate the seal (a gasket).

A flanged joint is used to create a good, high-pressure joint. It is easy to install and remove components by breaking the flanged joints. By using flanged, you are able to have an inexpensive, removable joint for most applications.

Types of Flanges

Loose-type flanges

Slip-on: A flange ring is slipped over the pipe from the opposite end or prior to welding on a lip. The flange pushes against the lip to create the force for sealing. Generally the sealing surface of this type is at the lip rather than the flange.

Threaded: The flange threads onto the pipe in this type. The sealing surface would generally be the flanges themselves. The threads would be part of the system integrity also because they are inside the sealing surface boundary.

SLIP-ON FLANGES, BOTH SIDES

SLIP-ON FLANGE TO FLANGE FITTING


Integral flanges

Forged/cast: In this type, the flange is fabricated as a part of the pipe during manufacturing. It involves somewhat high manufacturing costs. The lengths of pipe are inflexible, so the final joint would require a different style.

Welded: This flange is welded onto the pipe section. It has the characteristics of the forged/cast-type for strength and rigidity. It is more flexible in dimension because the pipe can be cut to length first before attaching the flange.

Types of flange faces

With the Flat Faced (FF) or Plain Face flange, the entire face is flat like plate steel. It generally uses a “full-faced” gasket to seal.

With the Raised Face flange, the gasket seating surface is raised above the surface of the flange. The gasket sealing area only includes the raised face area, not the bolt hole area.

The Male-Female (or tongue & groove) has one male flange face (has a raised portion) and one female flange face (inset portion). The two flanges mate with a gasket between the sealing surfaces.

There are two types of flange face surfaces-

The smooth surface has minimal tooling marks, or may even be lapped or stoned smooth. This surface is generally used with metal gaskets and is the only surface that can be used with a metal-to-metal seal without a gasket (some turbine nozzle housings e.g.).

The serrated finish has intentional tooling marks to aid in gasket retention. The tooling may be a phonograph finish - a continuous spiral throughout the entire flange face. It could also be concentric rings which are evenly spaced circles. The serrated finish is the most common. The raised sections are generally not more than .050” high.

F L A T F A C E D F L A N G E

R A I S E D F A C E F L A N G E

T O N G U E A N D G R O O V E F L A N G E


Gaskets

Gaskets are used to create an inexpensive, fluid-tight seal. They eliminate the need for the perfect surfaces which would be required to seal with a metal-to-metal fit.

A gasket should have the following properties.

• Conformability (Malleability): Pliable enough to conform completely with both large and small imperfections in joint surfaces.

• Elasticity: Ability to expand and contract under pressure, thermal and/or other loads.

• Compatibility with internal and external environment: Can resist chemical attack by contained fluids or outside environment.

• Strength: Ability to accept high clamping forces and hold back the internal pressures without failing structurally.

The following are some of the basic gasket types and their uses

Non-Metallic

Non-metallic gaskets are made of a composition material, paper, vegetable fiber, synthetic material, asbestos, cork, elastomeric or plastic, rubbers, and teflon.

Some of our gasket material in the past has contained asbestos. We are replacing all of these with non-asbestos types as they are removed for maintenance.

Our procedures identify some of the non-metallic types as Soft Gaskets. These gaskets are those that can be extruded under light loads such as a strong finger pressure or low clamping. The following two fall into this category.

The cork gasket is used with oil and solvent systems up to 212° F. (an oil filter casing e.g.)

The elastomeric or plastic encompasses a wide range of non-metallic materials. They include rubber where applications require light bolt loading, reinforced rubber (with wire or cotton fiber) which can greatly increase the strength, plastics where temperatures or corrosive action of chemicals destroy natural or synthetic rubbers, and Teflon (Polytetra-fluroroethylene) which is good for temperatures up to 480° F.


Metallic

The common types of metallic gaskets are plain metal and corrugated metal.

Metallic gaskets are generally made of softer materials like Lead, Silver, Copper, Platinum, Nickel, and Aluminum. Metal gaskets are used for applications what have extreme pressures and temperatures.

The plain metal gasket requires the highest bolting preload. The decreased contact area of corrugated gasket allows for creating a seal with a lower preload.

The Spiral Wound gasket is a combination of metallic and composition. A continuous strip of preformed metal is wound spirally from inside to outside, with a filler cushion between each ply. This type of gasket is used for high temperature and pressure and joints with shock and vibration problems. Some spiral wound gaskets have a backing plate, a metal retainer located around the perimeter, to center the gasket and prevent lateral expansion of the gasket when it's compressed. The backing plate also increases the overall strength of the gasket assembly. The most common material used as a filler in the spiral would gasket used to be asbestos. We are replacing these with non-asbestos filler material.

C O R R U G A T E D G A S K E T

O T H E R C O N F I G U R A T I O N S

F L E X I T A L L I C

2 3 - 4 - 6 0 0A P I - 6

0 1 - 3 0 4T E

F

T r a d e m a r k

N o m i n a l P i p e S i z e

P r e s s u r e R a t i n gS p e c i f i c a t i o n

W i n d i n gM e t a l

F i l l e r M a t e r i a l ( I f n o tC a n a d i a n A s b e s t o s )

C e n t e r i n g L o o p s

R e i n f o r c i n g R i n g


Seal Rings ("O"-Rings)

This is a type of gasket rather than a material. They are generally made of an elastomeric or metallic material. In this gasket, the system fluid supplies the sealing force by pressing the gasket against its seating surface. The initial force required to seat the gasket so that pressure can begin to increase is very low.

The O-ring has some advantages. It can provide sealing at very high pressures. The MSIV, for example, has several rings that seal at pressures of 6,000 psi both with and without the use of a backing ring using a Viton rubber material. The Reactor Head uses a metal O-ring that seals at 2,500 without a backing ring. O-rings are easy to use and relatively insensitive to the flange finish.

Bolting Material

The basic bolting material includes Studs (or Bolts), Nuts, and Washers. They are used to apply the force to create the seal at the flange interface. The bolting must be tightened evenly for even gasket compression to create the seal.

The bolting material must be the proper material as illustrated in the following events.

SOER 84-05 & related IN 86-108, Supplement 3

At Oconee 2 & 3 and Fort Calhoun, Boric Acid Corrosion due to gasket leaks caused degradation of Reactor Coolant Pump closure studs. Three studs ea. on two different pumps had diameters reduced from 3½" down to between 1-1½" by the Boric Acid corrosion.

At Maine Yankee, 6 of 20 S/G studs were broken while removing the manway cover. Five additional studs were cracked.

At Calvert Cliffs, three nuts on an incore instrumentation flange were corroded by boric acid leaking past the flange gasket. Subsequent inspection found another assembly with 3 nuts corroded. One was completely missing and the stud had dropped out.

At Three Mile Island I, a small leak on the pressurizer spray valve was found. Tightening of the flange increased the leak size to 3 gpm. After isolating, continuing attempts to tighten caused the stud to break. Two other studs on the flange were then found to already be broken and a 4th was severely damaged. ASTM A193 Grade B7 studs used.


With the plant shut down and RC temp at 125°F, a San Onofre Control Room operator was attempting to change valve positions in the shutdown cooling system and found that an isolation valve was stuck in the closed position. Mechanics were sent in to manually open the valve with a pipe wrench. During the attempt, the packing follower plate was dislodged when the carbon steel hold down bolts, corroded by boric acid leakage, failed. The packing then extruded due to the 350 psig system pressure. A leak of 60 to 100 GPM developed spilling 18,000 gallons of reactor coolant to the floor of containment

At The plant, the anchor bolts for whip restrains in the containment building cracked during normal handling. A representative sample of the anchor bolts in the warehouse indicated that 36% of the bolts fell outside the hardness specifications. This indicated a lack of control by the manufacturers.

These events were significant in that improper bolts had lead to significant failures in the power plants, including failure of reactor coolant system pressure boundary bolts. Boric acid corrosion can be at a very high rate, up to 1.65"/yr. in high temperature environments. At 200º, oxygenated Boric Acid (like 15% Boric Acid leaking on a 210º pipe) can corrode at the rate of .4” per month.

To correction this problem, we are using corrosion resistant materials, correcting leaks promptly, and using the proper material for the system.

As we identified earlier, to ensure we use the proper material, we use the Work Order which derives its material list from the Piping Material Classification Sheets (13-P-ZZG-012). The Work Order will agree with the classification sheets or have an engineering evaluation. The Engineering evaluation documents could also identify correct material.

CRDR 2-8-0033 documents a case where the material classification sheets were not used. A valve with Teflon lining was being installed in an acid line. The resulting acid leak from this installation revealed a number of concerns. One was that there was no gasket installed. The maintenance techs felt there was sufficient gasket material in the Teflon lined piping and valve. The Piping Material Classification sheets, however, identified “envelope gaskets” for this installation. The envelope gaskets were not installed. Although this was not the primary cause of the leak that occurred on this occasion, it could well have contributed to a leak at a later date

Your experience is also important. When parts are disassembled for PMs or repair, they should be inspected. Parts with premature wear or deterioration should raise a question to your mind. Note the parts problems and save them for equipment root cause failure analysis (ERCFA) by engineering. Sometimes the installed material is not the most compatible. The only way we can know this is through the ERCFA method.


An example of incompatibility is documented in SEN 190. A leaking Pressurizer spray line control valve was noticed on startup at Davis-Besse in May, 1998. An evaluation concluded it would be no problem in the short-term because there was no susceptible material. As a precaution, monthly inspections during operation were conducted. They showed no change in leak rate from the packing. On September 1, a body-to-bonnet nut was found missing. It was concluded that a contract worker must have removed it when installing a seal injection fitting. No attempt was made to remove the boric acid crystals from the valve. A 2nd nut was found missing on September 9. This time they investigated why. It was discovered that 3 carbon steel nuts were inadvertently installed on the body-to-bonnet flange. The three nuts were dissolved by the Boric acid by 100%, 93%, and 29% of their original size. Two other nuts were also found to be magnetic, but not dissolved. Testing showed they were 410 stainless steel nuts, not susceptible to Boric Acid corrosion. 410 stainless steel is, however, magnetic, so that is not a perfect test of susceptible materials.

Material identification on bolting material:

The easiest way may be to read the head of the bolt and compare it to a chart. The markings on the bolt indicate a material specification. Charts are available for the purpose of reading the codes on the bolts. Any interchangeability of specifications and codes would require an engineering evaluation. The substitution of higher number grades does NOT mean you have a better material for the job. It may not meet all the criteria needed as well.

Larger bolts and nuts may contain a Heat Code, which can be traced to the material if they are ‘Q’ class. This Q-class bolting requires certification sheets. The documentation from the warehouse is sufficient for us to verify bolting material.

G r a d eS A E

012

3

5

5 . 2

7

8

8 . 2

T e n s i l eS t r e n g t h

5 5 , 0 0 0 p s i

1 0 0 , 0 0 0 p s i

1 0 5 , 0 0 0 p s i

1 2 0 , 0 0 0 p s i

1 3 3 , 0 0 0 p s i

1 5 0 , 0 0 0 p s i


EO04 Identify precautions when disassembling a flanged joint

The basic prerequisites for flange disassembly are:

• Be able to verify flange location . Flanges are not always labeled, so you may need to read the isometric drawings to find the exact location. Manway locations should be identified. For any of these, use the STAR principle and verify the proper location.

• Check for signs of leakage . This should be done before disassembly as part of any root cause potential. Check for wetness of the insulation or flange joint, signs of leakage on the surfaces below the flange, or signs of leakage on the bottom of the joint itself.

• Inspect condition of studs, nuts, and washers to ensure they are free of burrs, nicks, etc. which could make it difficult to remove the nuts safely. If not satisfactory, you may need to take extra precautions. For example, you may need tools for cutting or breaking bolts and nuts. You may need to set up to capture flying or falling debris (broken nuts/bolts) to protect yourself and nearby workers and/or equipment. Also, be sure to take extra precautions for ensuring the system is depressurized.

• Verify piping is depressurized . Use vents and drains where possible. Check pressure gages if available. If you are not able to personally verify the piping or equipment is depressurized, you must take extra precautions while disassembling

The disassembly of the flange should include the following steps.

Loosening the bolts. It is a good practice to loosen all bolts prior to removing. This will ensure flange integrity if pressure still exists. Ensure the path of spray is clear or contained. The spray will generally be perpendicular to the pipe axis. Wait for all pressure to be released before continuing with the disassembly.

NOTE: If bolts are loose and nothing comes out, don’t assume there is not pressure. Carefully pry the flanges apart to ensure any pressure would be released.

Remove bolting material, Bag and tag it. If there is a “pipe strain” (a stress on the joint) you may need to relieve this with chainfalls or come-alongs prior to removing the bolting. Do not simply hammer them out as this will damage the bolts and possible cause injury when the stress is relieved.

Remove the gasket material to prevent it falling out. Be sure to check the type of material using Piping Materials Classification sheets, the planner, old work orders, C & I numbers or APN, and visually. If it is suspected of being asbestos, you must be asbestos worker qualified to continue. If the gasket is stuck to one side, it can be removed later. If there is evidence of damage from normal use, bag and quarantine the material for possible root cause failure analysis and contact the foreman.


Open the flange, then clean and inspect it. The seating surfaces must be cleaned of residual gasket material to be ready for inspection.

Inspect for damage to flange faces. Radial cuts are the most likely to create a leak path, so be especially aware of them. Perform whatever work is allowed done under the work document to make the surface ready for reassembly. Take care not to exceed the limitations of the work document without modification to the document.

Verify alignment of flanges for reassembly.

Verify condition of the nut running surface. It should be machined smooth for a nut or washer so it will not adversely affect the nut tightening.


EO05 Describe How To Preload A Joint Using A Torque Wrench

The following identifies the general requirements prior to making up the flanged joint.

• Inspect the condition of the nuts and studs . The threads must be free of burrs, nicks, etc. Broken threads or cracks would weaken the bolt strength.

• Clean threads as needed by brushing, using approved solvents, or running a tap or die down the threads to clean them up. To verify thread condition you should run a nut down the stud/bolt.

• Lightly lubricate the threads with an approved lubricant. Don’t over-lubricate.

• Determine the bolting pattern and the number and locations of the bolts if necessary.

To make up the joint, the following steps are performed.

• Install enough bolts to hold the gasket in place, and then install the gasket. Ensure the gasket surface meets the flange sealing area fully, then install the remaining studs with the washers and nuts and run the nuts down snug.

• Use the specified torquing pattern. This involves the “criss-cross” pattern generally. This helps ensure the flanges will pull down evenly. The flanges should be somewhat aligned prior to bolt-up. Some force may need to be applied to align the flanges if a pipe strain existed, but this should be minimized.

How much of the specified torque is applied to the bolt tensioning?

N U T - T O - F L A N G E F R I C T I O N

B O L T T E N S I O N

1 0 %

5 0 % 4 0 %

T H R E A DF R I C T I O N


• Torque the fasteners in steps. Why multiple passes? Torqued joints are susceptible to Elastic Interactions. Multiple passes minimize the effect of these elastic interactions. A minimum of 4 steps is required. For example, 100 ft-lbs would require 1st 25, then 50, then 75, then 100. A fifth pass is also required (an extra pass at 100%) to ensure fasteners have not loosened due to elastic interaction and relaxation. Additional “check passes” may also be required.

• Determine torque value. If a torque range is given, the procedure requires that the torque be done at the mid-point of that range or the next closest value higher that can be achieved. If a specific torque value is given, the procedure requires that the torque be done at that value, + 10%, -0%.

• Use specified patterns. The general pattern is a “criss-cross” pattern. It ensures the flanges are pulled down evenly.

• Ensure proper thread engagement when complete. This means the stud or bolt is fully engaged with the nut for standard nut and stud arrangements. For a blind hole, it requires 1 bolt diameter of engagement into the hole.

There are other practices that can improve the accuracy of torquing.

• Using hardened washers under the nut. This is required by some codes, but is also recommended where it may not be required. This is the number one variable which can most affect the torque to preload relationship.

• Ensure the nuts are not on backwards. The raised lettering should be out (readable). This is the number 2 variable.

• Properly lubricated the fasteners. This means we should use the recommended lubricant in the proper amount.

• Ensure flanges are aligned prior to bolting them up. You may need to measure the flange gap to ensure the faces are parallel. A 3° misalignment can significantly affect the stud tension.

F u l l T h r e a dE n g a g e m e n t

O n e B o l tD i a m e t e r

C h a m f e r r e dS t u d


• When torquing soft-gasketed joints, extra precautions should be taken to ensure the compression is even. The procedure requires that you take the nuts up snug then turn them ½ turn at a time until there is movement of the gasket, then complete the pass so all nuts are tightened evenly.

• Some gaskets are not considered soft gaskets, but will cold flow (deform considerably under pressure after tightening). Wait at least 15 minutes on this type of gasket, then re-torque to the final value.

Unlubricated Lubricated

0º

Nut Normal

3º

Nut Normal

3º

Nut Reversed

0º

Nut Normal

3º

Nut Normal

3º

Nut Reversed

w/o Washer 6,500 6,100 5,400 9,600 9,200 7,200

w/ Washer 6,900 6,500 6,300 10,100 10,000 9,200

When we had an acid spill of about 1,000 gallons, a contributing cause was the improper bolt up of the flanges. The piping and flanges are lined with a plastic material. After torquing, this material will “cold flow” or continue to relax for a considerable time. It should have been retorqued the following day but was not. The relaxation on this type of material can be considerable.


LESSON 3 TERMINAL OBJECTIVE

Given a maintenance activity involving tubing and tube joints, the Apprentice Maintenance Mechanic will Describe the installation and rework methods, as demonstrated by passing a written examination with a minimum grade of 80% or better


EO01 Describe the types of tubing joints.

EO02 Describe the makeup, to include cutting, bending and installation, of tubing runs.

EO03 State the rework and makeup criteria for a compression type joint.


EO01 Describe the types of tubing joints.

There are three basic types of Tubing Joints. The soldered joint has already been addressed in lesson 2. The two remaining types are as follows:

Flared tubing joint

There are single (standard) flare and double flare joints. Double flare joints are normally used to prevent joint leakage caused by tightening nuts too severely or by frequent remaking of the joint. They can also be found on very thin-walled tubing. Double flare joints are commonly used on fuel and hydraulic lines.

Compression tubing joints

There are several styles from many manufacturers. For this class, we will only discuss Parker-Hannifin and Swagelok since they are the most commonly used. Both styles use ferrules that are swaged into the tubing to make the compression joint. One difference in the Swagelok is that it uses a 2-piece ferrule.

EO02 Describe the makeup, to include cutting, bending and installation, of tubing runs.

Laying Out the Run

Determine the length of tubing needed to makeup the tubing run. When making a run, the proper installation of the run must be considered. After determining the run layout, measure the length from bend to bend and total the number. Subtract one tube diameter for each 90° bend in the run, and 1/2 the diameter for each 45° bend. This is called "stretch", and results from the bends cutting the corners. This final number will give you the minimum tubing length required. It is always a good idea to make the final length cut after making all bends.

135

4”

4” 4”

8”

90°

90°

1/2 tubing


Cutting Tubing

Cut the tubing end and prep it by first selecting the proper tubing cutter. Very large tubing is cut using a pipe cutter, normally a two wheel cutter is used for metal tube.

Inspect the cutting wheel for damage, if it's bad, replace. On Q-class stainless steel, use a new wheel or one restricted for stainless steel use only. This will help prevent contamination of materials that could create a corrosive condition.

Tighten the cutter on the tubing until the wheel makes contact. Begin cutting by tightening the cutter and rotating it around the tubing. Don't over tighten the cutter, because although the excessive pressure on the cutter makes a quick cut, it creates a larger burr and work hardens the tube metal. This promotes cracking in flared applications. Be sure to ease up when the cut is almost complete.

A fine tooth bladed hacksaw can also be used to cut tubing. Take care to make a square cut.

Prepare the end of the tubing

After completing the cut, deburr the tubing O.D. & I.D. with a reamer, emery cloth, or fine file. Most tubing cutters have an I.D. deburring reamer on them, insure you don't ream beyond the tubing base diameters. You can also use tubing reamers made for both inside and outside reaming.

If making up a flared tubing run, the end of the tubing should be radiused slightly to prevent splitting.

Bending Tubing

To start the bending process, mark the tubing. All measurements are to the tube centerlines. For bends of 90° and less, measure to the intersection of the tube axis centerlines and mark the tube. This is the standard dimensioning for most drawings.

For bends over 90º, measure to the tangent of the bend that is perpendicular to the upstream leg and mark the tube. This is not the standard dimensioning for the drawings.

If precision is needed, use a ferrule and a sharp pencil to mark the tubing all the way around. Do NOT scribe a line on tubing. Scratches create points where corrosion and stress can weaken the tube.

It is also a good practice to mark a bending plane reference mark opposite the direction of the bend.


Using the bending tool

Correct placement of the tube in the bender is critical to a proper bend.

For bends of 90° and less, a line tangent to the tube bender's radius block, at the desired angle, must intersect the tube centerline at the length mark. For bends of greater than 90°, line up to the 90° mark. Most tubing benders have marks on them to identify standard bend angles.

The bending plane reference mark must be directly opposite the bender's radius block.

Make the bend, being careful not to over bend, but allowing for springback. Springback is approximately 3° for each 90° of bend. It will be less for soft copper tubing.

Always bend in the same direction, such that the "stretch" will not get trapped. If you must reverse your bend direction, subtract one tube diameter for a 90° and 1/2 a diameter for a 45° from your length mark then line up the normal 90º mark with the revised mark. Most tubing benders have an R mark for reverse bending of 90º which have already done the subtraction for you.

Tubing Stretch

These rules for stretch values are approximate. A Tubing Gain Chart has the actual stretch values based on the radius block size of the bender. For maximum accuracy, because of the variations in stretch with different material, Always test bend a piece of tubing first to find the actual "stretch" for your bends.

If pre-marking all the bends of a run, you must subtract the stretch from previous bends for each length mark after the first.

Tangent to 45º

Cutting dimension line

Cutting dimension line

45º 90º


EO04 State the rework and makeup criteria for a compression type joint.

There are 2 main manufacturers of compression type fittings that we use here at The plant, Parker-Hannifin and Swagelok. It is very important to ensure that the joint you are assembling contains only parts required for that manufacturer’s fitting. For this course we will only discuss the Swaglok brand of compression fittings.

General Instructions

The following general suggestions should help you obtain safe, trouble free performance from these Swagelok fittings.

• Avoid combining or mixing materials or fitting components from various manufacturers.

• Ensure that when the joint is assembled, that the parts are installed in the correct order.

• Never turn the fitting body, hold the body and turn the nut.

Some additional tubing considerations are:

• Tubing material should always be softer than the fitting material. For example: Stainless steel is harder than brass. Stainless steel tubing therefore should never be used with brass fittings. When tubing or fittings are made of the same material, the tubing must be fully annealed (heat treated for softening).

• Use an insert on soft or pliable plastic tubing.

• Inspect tubing for depressions, scratches, raised portions or other surface defects that will be difficult to seal.

• Tubing which is oval will not easily fit thru fitting nuts, ferrules or bodies and should never be forced into the fitting.

CRDR 3-2-0146: U3 Airline Cracked Where it Connects to Valve, 4/23/92

On 4/23/92, the copper line to valve 3JEDNLV0604 failed in reverse-bending fatigue due to normal service vibration. The failure occurred near the fitting connection, which is considered a region of maximum stress. This condition was further enhanced by a cut created during the installation of the Swagelok fitting as a result of poor installation practice.

To prevent the Oconee type of event from occurring here at THE PLANT, and to help eliminate CRDR 3-2-0146 type events, the proper assembly steps must be followed when assembling Swagelok fittings.

Making Up the Joint

Information presented is based on current vendor information and may be precluded by special instructions in a particular work order package.


MAKEUP INSTRUCTIONS: 1/4 - 1"

Insert the tubing into the tube fitting. Make sure that the tubing rests on the shoulder of the fitting. Tighten the nut finger tight.

Before putting a wrench on the nut, scribe/mark the nut in the 6 o'clock position. A marker may be used. DO NOT scribe the tubing as this would violate spec 13-JN-702.

Hold the fitting body steady with a backup wrench and tighten the nut 1¼ turns. Watch the scribe mark, make one complete revolution and continue to the 9 o'clock position. With the scribe or marker indication, it is easier to see the 1¼ turns.

Makeup Instructions for 1/16", 1/8" and 3/16" size tube fittings, only 3/4 turn from finger tight is necessary.

Pre-swaging tubing:

Pre-swaging is advantageous where field conditions are either cramped or where ladders must be used (making joint assembly difficult). When preswaging, oversized or very soft tubing may occasionally stick in the tool after pull-up. (Oversized means that it may be on the high side of any given ASTM diameter tolerance (.280 vice .250)). If this happens, remove the tube by gently rocking back and forth. DO NOT TURN the tube with pliers or other tools since this may damage the sealing surfaces.

PRE-SWAGE INSTRUCTIONS:

Assemble the nut and ferrules to the preswaging tool. Insert the tubing through the ferrules until it bottoms in the pre-swaging tool and tighten the nut finger tight.

Tighten the nut according to the initial installation instructions (1 ¼ turns), then remove from the preswaging tool.

The field connection can now be made by following the Re-tightening Instructions.

Retightening instructions:

Insert the used or preswaged ferrules into the fitting until the front ferrule seats in the fitting and the tubing is bottomed against the shoulder of the body. Tighten the nut by hand.

Rotate the nut about 1/4 turn with a wrench (or to the original 1-1/4 position) then snug slightly with the wrench.


Key points to remember

• The tube should always be inserted fully into the fitting.

• The fitting parts should be installed in the correct order.

• The fitting should always be tightened the appropriate amount.

• Never twist a tube when disassembling it

CRDR 2-2-0272, Tubing Depressurization

Although this event happened to I & C, the potential exists for the mechanic to do the same.

The pressure transmitter on MSIV accumulator was isolated. The fitting was then loosened on bottom of transmitter to bleed the pressure (over 3,000 psi). After the nut was loosened about 1/2 turn, the tubing blew out, making a sound like a rifle or shotgun blast. This bent the tubing into an "S" shape.

An investigation showed that this method to bleed pressure was a common practice among I & C technicians. This was also not the first instance of failure on the accumulator fittings. It was classified as a close call accident.

Analysis

The vendor instructions for these type of fittings read, "Do not bleed down system by loosening a fitting." The reason is that once the fitting is loosened, it no longer has the same holding power on the tubing. Why wasn’t this type of failure more common? Most likely because the pressures are not as high in other systems. Remember, the MSIV fitting still has over 3,000 psi on it until it is bled off.

Corrections in methods/design

The practice of bleeding pressure by loosening a fitting was to be discontinued immediately. Other places to bleed pressure must be located such as vent and drain valves installed on instruments if installed. Use panel drain valves where available. If installations without bleed connections exist, they will require modification. Bleeder fittings are to be installed.

RCPR 1-91-050: Contaminated Fitting Found on Non-contaminated System, Unit 1, 6/6/91

Two fittings, with levels of 1000 to 3000 DPM of fixed contamination, were found during a plant tour. These fittings, identified as radioactive material, were marked with purple paint and connected to non-contaminated systems (IA and DS). The fittings were removed by operations.

An investigation revealed two things: That there are no restrictions on the use of purple painted fittings inside the RCA and that no guidance is given in training either on any restrictions or on the use of purple painted fittings.


Procedure now says we "should not be used" in non-contaminated systems. The use of radioactive hoses or fittings on non-contaminated systems is not considered a sound practice. As a result, gang boxes are set up in the RCA to segregated storage of radioactive hoses and fittings.

Ensure that only non-contaminated fittings are used on/in non-contaminated systems. If the job you are working on requires the use of such fittings, RP will be contacted to evaluate the requested use, prior to any installation.


LESSON 4 ERMINAL OBJECTIVE

Given piping materials and work control documents, the Apprentice Maintenance Mechanic will fabricate and assemble piping and tubing as demonstrated by satisfactorily completing the Laboratory Practical Evaluation.


EO01 Calculate cut lengths for piping installation

EO02 Make up compression type tubing connections.

EO03 Make up flange type piping connection per work control documents.

EO04 Bend tubing as indicated by drawing


EO01 Calculate cut lengths for piping installation

Piping runs will sometimes require that you connect two pipes together when they are offset from each other. This requires a calculation to determine the dimensions of the piping length along the travel and the opening to fit the piping and its fittings in. The basis of this calculation is the math of the right triangle.

Right Triangle Fundamentals

A right triangle contains one 90º angle and two complimentary angles that add up to 90º. The longest side of a right triangle is opposite the 90º right angle, and is called the hypotenuse. The relationship between the hypotenuse and the two shorter sides is as follows.

If you square the length of each of shorter sides and add them together, their sum equals the length of the hypotenuse squared. Mathematically,

C is the hypotenuse and A and B are the shorter sides of the triangle (Pythagorean Theorem)

Example: the familiar 3 x 4 x 5 right triangle.

A = 16; B = 9; C = 16 + 9 = 25 = 52

If the right triangle has equal length shorter sides, the complementary angles must be equal. Since they add up to 90°, they must be 45° each. If we pick a right triangle with both shorter sides 1" in length and use the relationships we just covered, then the length of the hypotenuse is the square root of 1 + 1 or the square root of 2 or 1.414 and, the complementary angles are 45º.

This tells us that if our pipe has a 45° offset, the ratio of the set to the travel is 1.414.

The “travel” of the pipe offset is the hypotenuse of our right triangle. 1.414 is the multiplier. The accompanying table has used the same process to identify different offset angles like 30º, 60º, 22½º etc.

You can also use trigonometry and set the length of the triangle side opposite the desired angle to 1". This will require knowledge of the Sine, Cosine, and Tangent functions on the calculator.

Sin θ = Length of the opposite side divided by the hypotenuse, where θ is the angle. If we set the side opposite the angle to 1" and solve for the hypotenuse (travel), the hypotenuse = 1/ sin θ = multiplier. For basic angles, we can use the chart.

CB

A

A2 + B2 = C2


Calculating travel and run using the chart

The set and travel distances determined so far, are along the center line of the pipe. If fittings are used to join the piping, we must account for their length when calculating desired pipe lengths. Fitting lengths are subtracted from the travel and added to the run distances.

Let’s use socket welds as an example. Dimension A on the chart is the dimension from the centerline to the bottom of the socket. This is extra length the piping does not have to fill. If socket weld fittings are used we would also have to account for any pull back required. Normally a 1/32" to 1/16" gap (pull back) is required at the bottom of the socket to allow for thermal expansion and contraction.

E


O02 Make up compression type tubing connections

Preparation of tubing

• Select the proper size and style fittings needed.

• Cut a short length of tubing and prep the end of the tubing for the compression fitting.

Installing the fitting

• Properly install the tubing nut and ferrules onto the tubing. Hand tighten the fitting, then tighten according to initial installation instructions.


EO03 Make up flange type piping connections per work control documents.

Inspect the flange face

The flange has a raised face. Inspect the flanges, gasket, and fasteners.

Assemble and tighten one pass

Tighten flange fasteners IAW work control documents. Verify the flange is taken down evenly. [This will be done by the instructor.]


EO04 Bend tubing as indicated by drawing

Cut length of tubing

Calculate the tubing length using the drawing provided. Unroll and cut the tubing. If desired, you can stretch and straighten the tubing prior to bending. You must have no more than 2” extra in your calculated length. [Instructor to verify.]

Mark bend locations

Start at one end and mark all locations. You may want to mark all around at each length so the mark is not hidden when in the bending tool. If desired, mark the opposite bend direction also as per lesson 4 instructions.

Bend the tubing

Start at one end and bend. Perform at least one reverse bend. All dimensions must be within ½”. [Instructor to verify.]

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Pipe Fittings and Piping Auxiliaries

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