failure analysis of ball valves worcester

8/10/2019 Failure Analysis of Ball Valves Worcester

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Worcester Control Valves

TP-12D-1

1. Look for misalignment of actuator, linkage, or handle. Need 0 to90 rotation. Stem must be perpendicular to bodyno side loads.

SOLUTION: Check for centrality of the actuator, coupling, stem andalignment of all brackets. Replace parts as necessary.Use dial indicator to measure stem perpendicularity.

2. Check body bolting torque; refer to IOM for correct torques. Torqueis for nonlubricated bolts.

SOLUTION: Using a calibrated torque wrench, check the torque ofbolts. Refer to attached chart or IOM.

3. Check flange bolting for proper insert compression. Body seal mustbe compressed for seat sealing. Slip-on flanges and thick rubbergaskets can affect performance of seal.

SOLUTION: Record location of piping supports, obtain photographsand make a sketch. Retorque flange bolts, record styleand type of gasket and flange. Discuss data withFlowserve personnel.

4. Normal torque when rotation 0 to 90 and back to 0. Measurestem torque to open and close. Listen for scraping noises whencycling; there must be no metal-to-metal galling. Compare data to

catalog ratings.

SOLUTION: Measure torque according to ratings, listen for noisesand replace metal parts as needed. Check air pressureat pneumatic actuator; make sure proper torque outputis available. Record air pressure at the actuator.

Failure Analysis of Ball Valves

Failure Analysis Of New Valves

Features to Evaluate if the Valve hasLeakage or High Torque:

TABLE OF CONTENTS

Analysis of New Valves . . . . . . . . . . . . . . . . 1

Analysis of Valves in Service . . . . . . . . . . . . . .

Photos of Valve Failures . . . . . . . . . . . . . . . . 8

Glossary of Valve Terms . . . . . . . . . . . . . . . 10

Bolt Dia. in/lb ft/lb Bolt Dia. in/lb ft/lb

!?4" 96 120 8 10 !?4" 72 94 6 8

%?16" 156 204 13 17 %?16" 120 144 10 12

#?8" 216 264 18 22 #?8" 192 216 16 18

\?16" 480 540 40 45 \?16" 336 384 28 32

!?2" 720 780 60 65 !?2" 504 522 42 46

Carbon Steel Bolts Stainless Steel and Alloy 20 Bolts


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2 Failure Analysis of Ball Valves TP-12D-1

5. Do a leak test on the valve. Pressure test from the other end of thevalve to evaluate second seat (not V-3 ball). If disassembling thevalve, mark the upstream and downstream seats and the twelveoclock position on each seat.

SOLUTION: Record leakage data using flow meter or countbubbles; determine if leakage is because of bad seatsor damaged ball. Return damaged seat to Flowserve forevaluation; replace soft seats as necessary.

6. Examine surfaces of the seat and ball for nicks and scratches.

SOLUTION: Using a fingernail test, determine if scratches areacceptable, or replace seats and metal parts ifnecessary. Note, if scratches can be felt on ball, thiswill cause leakage during normal use.

7. If the valve was cycled or tested at high pressure, there will be aburnishing or contact band from the ball to seat and back of theseat from the valve body.

SOLUTION: Determine if the contact is even. Full contact on seatmay mean over-pressuring of the valve. Check forproper assembly of the valve.Clean and repair parts asnecessary. Do not reuse bodyseal gaskets. Assure that the Sgasket is properly installed.This gasket is not reusable.

8. Evaluate the surface finishes on the seatand the ball. Look for porosity, cracks andimperfections. Contamination duringinstallation or improper handling can

cause leakage.

SOLUTION: Look at the orientation of theseat and sealing wearpath. Anydeformation of soft parts willrequire complete rebuilding ofthe valve. If there is anybending or metal deformation,a new valve is required.

9. Check if valve seat was properly assembled. Look for gaps betweenthe seat and valve body from oversized or undersized seats.

SOLUTION: Some small seats can be put in backwards preventingproper bolting of end caps and causing leakage.

10. Evaluate the metal surface finish: radial scratches, chatter,smearing, tearing or improper machining.

SOLUTION: Inspect machined surfaces for drag lines that couldcause scratches to stem seals, and for impropersurface finish on the pipe ends which could causeleaking behind the seats. Replace parts as necessary.

11. Look for evidence of porosity or void in the metal parts.

SOLUTION: Any porosity or voids that could cause seal or seatleakage means metal parts have to be replaced.

Flow Control Division


Failure Analysis of New Valves


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TP-12D-1 Failure Analysis of Ball Valves 3



1A?f" 2" Size Top-MountValves Shown

12. Stem nut and locking nut should be properly adjusted for zero-leak stem seal. Look for rough marks inside stem bore orpossible galling. Evaluate thrust washer and stem seal fortearing or deformation.

SOLUTION: Check that the stem seal nuts have been properlyadjusted by flattening out the Belleville washers andback off 1/6 turn. Automated valves require a doublelocknut, MP44 valves and V51 use heavy, singlelocknut. Check that washers are not cracked ormissing.

13. Missing parts or bent mounting kits can side load the stem orreduce actuator torque.

SOLUTION: Check centrality and alignment of the actuator andstem. Replace parts as necessary. Look for use ofproper coupling and slop between stem and couplingand ball and stem for proper closing of the valve.

Material Color

Polyfill Black

Peek Tan

Graphite Silver Gray

Carbon-Filled PTFE Black

UHMWPE Opaque White

Delrin Brown

Filled TFE Off-White

Color Chart for Various Stem Component Materials


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NOTE: Assure all system pressure is zero and fluids are drained fromvalve before loosening any bolts. If fluids are dangerous, performproper cleaning before valve is removed.

1. Review same causes as new valve.

SOLUTION: Record all process conditions and try to determine thedate and where the valve was bought.

2. Look for start-up problems such as weld splatter, dirt, scratches,impingement of fluids and contamination forced into the seats or ball.

SOLUTION: Clean the valve, inspect all parts, polish ball, ifpossible, rebuild and replace soft parts. No pipingcompound should be in the valve.

3. Verify seats were made by Worcester Controls and properly installed.

SOLUTION: Return damaged seat and soft parts to Flowserve for

evaluation. Rebuild with authorized Worcester parts.Use proper lubricants per IOMs.

4. Evaluate if the valve is new or has been reworked and remachinedby customer.

SOLUTION: Determine if there has been welding or painting whichwould indicate rework of the valve. Look for counterfeitvalves with improper components. Determine ifalterations have damaged valve.

5. Evidence of metal corrosion or improper seat/seal selection forapplication. Record pressure, temperature, media and relevantinformation for analyzing failure. Record pressure at shutoff andthrottling pressure drop.

SOLUTION: Evaluate the extent of corrosion, re-evaluate materialselections, replace complete valve if necessary. Reviewdate of installation and discuss application withFlowserve personnel.

6. Look for possible leak paths through stem seals, betweenball and seat, behind seat and possible wire drawingof sealing surfaces. Document location of leakage.

SOLUTION: Determine where there is a leak path.Replace soft parts. If there is wiredrawing or damage to the pipe ends orball, replace valve as needed.

7. Verify if hydrotesting of the valve was done in the closed position.Pressure over 110% of maximum ratings will damage seat.Determine if start-up testing was performed on valves. Find out ifthe valve was hydrotested and then exposed to freezing

temperaturescavity pressure due to ice can bend metal parts.

SOLUTION: Verify temperature, possible system hydrotest andmisapplication of the valve. Use V3 vented ball, ifnecessary, to prevent deformation of the seats.Evaluate flatness of pipe ends with straight edge. Nodeformation is allowed. Replace valve if necessary.

8. Thermal Effects: If valve is closed and full of liquid (1 temperaturerise equals 100 psi in trapped cavity) look for evidence ofdeformation of seats, body seals, or pressure vessel.

SOLUTION: Check for thread damage or deformation of the bodybolts, seats or seals at pipe ends. Replace components

as needed.




Valve Shown inClosed Position,

No Pressure

1A?f" 2" Top Mount Valves Shown

Failure Analysis of Used Valves


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9. Crushed ball downstream seat due to water hammer, over-pressurization or piping stress can bend metal parts or deformseats and/or balls.

SOLUTION: Measure roundness of the ball, flatness of the pipe

ends, replace valve if damage has occurred.10. Ball off-center, during assembly or improper stem adjustment can

force stem down into ball. Proper assembly of valve, to salesdrawing or IOM. Wrong stem-to-ball engagement can yield themetal parts or ball wont cycle. Improper or missing stem sealscan affect stem engagement.

SOLUTION: Check the ball-stem engagement. Look for bent stemsand deformation of the ball or damage to the metalparts. Assure correct assembly of parts.

11. Cold flow of the seat due to excessive temperature pressure orexceeding allowable throttling pressure drop.

SOLUTION: Check the proper closed position of the valve. Evaluatethe torque of the valve, the operator output torque andreplace valve if necessary, or use large actuators.

12. Popcorning, polymerization or deformation of the seat due tomedia absorbed into the material and mechanically expanded.

SOLUTION: Return seats to Flowserve for evaluation. Clean valve,replace seats and seals, and consult with factory, ifpossible, to upgrade to alternate material such as FEP,High-per Fill, etc.

Average Penetration Rate Per Year

Code Mils Inches m

< 2 0.002 50 < 20 0.020 508

{ 20 50 0.020 0.050 508 1,270

X > 50 0.050 1,270

Footnotes for Data Squares1. Pitting2. Stress Corrosion Cracking3. Intergranular Attack4. Crevice Attack

Corrosion Allowance




EndPlug

Cavity FillerSeats

S.S. Ring

(split)Valve Body

(special profile)

S.S. Ring

(solid)BodySeal


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13. Look for rust or dirt and location of sealing band. Evaluate if therelief slots are plugged and not functioning properly. May needV-3 ball relief.

SOLUTION: Look for the sealing path of the body seal, seats and

stem seals. Replace soft parts if needed. Ifdeformation or damage to metal occurs, replace valve.

14. 360 ridge in the downstream seat could indicateoverpressurization or hydraulic water hammer.

SOLUTION: Refer to examples of seat failures in attacheddocument. Replace parts as needed. If metal parts aredamaged, replace valve.

15. Fold over where the seat has been extruded due to impropersupport during cryogenic cool down or high temperature withimproper ball position. Exceeding allowable pressure drops.

NOTE: Ball must be fully open or fully closed while being cooled

to cryogenic temperatures.

SOLUTION: Check for ball stem alignment, replace the seats.Check actuator mounting; review torque of the valveusing attached ratings.

16. Impingement or erosion damage to the seat.

SOLUTION: Replace seats. If damage occurs to metal parts,replace valve.

17. Partial support. If valve is assembled with the valve not fullyclosed, damage occurs to the seat. Look for twisted stem orimproper top works.

SOLUTION: Check that the valve was properly assembled, the

rotation of the valve to its closed position and properactuator sizing.

18. Distortion of the seat due to thermal expansion. V-3 portingmaybe required. Upgrade to stronger seat.

SOLUTION: Replace seats as needed. If metal damage hasoccurred, replace valve. See photos of seat damageon pages 8 and 9.

19. Wire drawing, backside or between the ball and seat. High-pressuresteam or throttling pressure drop. Do not throttle below 15 onclean service. Consult factory for steam or slurry applications.

SOLUTION: Refer to throttling pressure drop, pressure temperature

ratings, and discuss application with factory.20. Seats that are cracked or broken due to thermal shock or

misapplication.

SOLUTION: Record process conditions, upgrade to a strongerseat, and replace valve if misapplied.

21. Body seals can be pinched between body and pipe end duringassembly or repair. Use lubrication to help body seal when bolted.

SOLUTION: Check the proper assembly of the body seals, butmost body seals are not reusable.



High differential acrossseat sucks seat out of cavity Ball Impingement Flattened

Area

Ball will contact seatduring closure, causing

further damage

UpstreamSeat

DownstreamSeat

Pressure

Distance Along Pipe

1234

Flow through a partially open ball valve. Possible flowconditions are:

pv at 1: Flashing downstream of ballpv at 2: Cavitation in ball, flashing downstream of ballpv at 3: Cavitation downstream of ballpv at 4: No vapor formations

Fluid Condition ft/s m/s

Liquid Normal 5 10 1.5 3Maximum 40 50 12 15

Gas Typical 250 400 (


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22. S-gaskets in backwards, or scraped at installation of center sec.

SOLUTION: Properly orient the S gaskets. On the welded pipeends, do not reuse on butt weld and socket weldseals. The initial body seals are rubber. These should

be replaced with metal S gaskets.23. Graphite seat seals cracked or sheared from use of improper

lubrication to assemble.

SOLUTION: Replace seats and body seals. Use proper lubrication.Do not reuse seat seal or body seals.

24. Pipe stress can bend valve, causing seat or body seal failure. Lookfor misalignment when valve is removed and record distance frompiping support.

SOLUTION: Get photo or measure piping support to determine ifpipe ends are being damaged or body bolts are beingdeformed.

25. Do not use schedule 80 or 160 pipe without special pipe ends orconsulting factory.

26. Evaluate seat for arc-shaped deformation which indicatesimproper ball closing.

NOTE: Full port valves 2" to 8" and reduced port valves 3" to 8"now use a new seat design with cavity relieving seats (CPP).




1A?s" 2" Top-Mount ValvesShown

Annular Groove

Feeder Groove

Contact Area

ContactArea

Contact Area

ContactArea

Assembled Condition(zero differential)

Cavity Pressure Condition(zero differential)

Cavity Pressure Relieving Seat


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A. Abrasive particles imbedded in the soft seats scratching both theseat and ball. Results in high torque, leakage and damage to themetal parts of the valves.

SOLUTION: Use harder seats and polyond the ball. Alternate is touse a more abrasive-resistant seat such as rubber orultra-high molecular weight polyethylene. Improvecleaning of system at start-up.

B. High temperature softening of the seat. Failure occurred onupstream seat, foldover due to the pressure distribution across theseat and partial support of an open ball.

SOLUTION: Use seat materials with higher temperature capabilitiessuch as the X, Alpha or Gamma. Review the service conditions andthe allowable throttling drop according to the catalog ratings.

C. This is a combination of erosion and corrosion due to excessivethrottling pressure drops. Solid particles in the flow may also causethis erosion.

SOLUTION: Review the sizing of the valve to make sure you areusing larger ball openings and staying above 15%open. Review the flow conditions for cavitation orflashing and try to locate the valve where it is takingless throttling pressure drop. If the media iscontaminated, try to use lower line velocities acrossthe valve to reduce the demonstrated wear.

D. This seat has been exposed to high temperatures and extremelyhigh cavity pressures. Usually this occurs when condensate orliquids are trapped in the valve and then heated up, and over-pressure then deforms the seat.

SOLUTION: Use the V3 cavity pressure relief and stronger seatmaterials.




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E. An example of where the ball has not fully closed. The high-velocity

fluid flow across the valve wire draws the seat and distorts thematerial. In closer examination you can see that the seat hasrotated in the valve cavity and foldover and damage has begun tooccur in more than one spot. Generally this could be attributed to:improper actuator mounting, slop between the ball and stem,wrong coupling or using the wrong parts. Another cause could betwisting of the stem due to extremely high torque or improperactuator/valve sizing.

F. This seat has been exposed to extremely high temperatures andextruded due to cavity pressure or fluid flow.

SOLUTION: Install seats of high-pressure/temperature capability,resize the valve to make sure it is within thepressure/temperature curve and is not exceedingcatalog throttling drops.




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Cavitation:The formation and collapse of bubbles when high velocity fluid flowsthrough a valve and the liquid goes below the vapor pressure.

Cavity Pressure:Cavity pressure can occur in the open or closed valve where liquid istrapped around the OD of the ball or inside the valve cavity. This isvery critical in cryogenic valves, but can also occur with temperaturerise of liquids or steam condensate.

Centrality:This is the alignment of two concentric circles, such as the ball andstem or the seats and body. If improperly aligned, there can beuneven forces for sealing or rotation of the valve.

Contact Band:

When a valve is sealing there is an area of impression between theseat and ball and the back side of the seat. This should beapproximately one third of the seat width. Full contact band is anindication that the valve has been over-pressurized and the seatdamaged.

Cold Flow:When the ball is pushed into the downstream seat, it may go beyondthe elastic limit of the Teflon. Excessive exposures at high pressurecan yield the seat and cause catastrophic failure.

Drag Lines:This can occur in the area of the stem seal or in the back of the bodyduring the machining. A broken toll or machine burr can cause aspiral cut, which affects sealing of the valve.

Fingernail Test:Rub the edge of your fingernail across a scratch. If the scratch can befelt this is sufficient damage to affect sealing and wearing of theseats. Metal parts should be buffed or replaced.

Flashing:When fluid flow goes through an orifice, a pressure drop occurs. Ifthe fluids go below the vapor pressure, bubbles will form and causeflashing.

Galling:When dissimilar metals or metals of unequal hardness are rubbedtogether, the softer metal starts to wear, and parts of the metal scoreand tear, damaging the sealing surface.

Popcorning:In the manufacturing of Teflon there are slight microscopic voidswithin the material. Monomer or plastics in the liquid state willmigrate into these pores, and when they change into a solid, there ismechanical deformation of the seat.

Porosity:Small holes in the seats or metal parts where media can leak veryslowly, causing external leakage or contamination back into theprocess.

S Gaskets:316 Stainless Steel metal gaskets used for body seals. These arecovered with Teflon or graphite.

Surface Finish:This is the machined surface of a part which gives you a static ordynamic seal. Centrality, flatness, smoothness and type of finish arevery important to the cycle life and zero-leak capability of the valve.

Throttling Pressure Drop:The difference between the upstream and downstream pressure. Asthe valve closes and the orifice between the ball and the seat getssmaller, pressure drop increases. Ratings are established both forthrottling services and steam.

V3 Option:

In valves where the possibility of cavity pressure can occur, a smallhole is drilled on the upstream side of the ball to give venting of theball. In addition, there is a second hole below the stem of the valve torelieve cavity pressure around the backside of an open valve. To getbidirectional sealing, the one-piece seat is necessary, but cannot beused on steam or cryogenic fluids.

Wire Drawing:When a valve has been damaged due to scratching or excessivethrottling drops, the high-velocity fluid cuts through the soft seat,causing a wear pattern which quickly destroys the seats.



Glossary

Trouble Analysis for Valves


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Flowserve Corporation has established industry leadership in the design and manufacture of its products. When properly selected, this Flowserve product is designed to perform its intended functionsafely during its useful life. However, the purchaser or user of Flowserve products should be aware that Flowserve products might be used in numerous applications under a wide variety of industrialservice conditions. Although Flowserve can (and often does) provide general guidelines, it cannot provide specific data and warnings for all possible applications. The purchaser/user must therefore

assume the ultimate responsibility for the proper sizing and selection, installation, operation, and maintenance of Flowserve products. The purchaser/user should read and understand the InstallationOperation Maintenance (IOM) instructions included with the product, and train its employees and contractors in the safe use of Flowserve products in connection with the specific application.

While the information and specifications contained in this literature are believed to be accurate, they are supplied for informative purposes only and should not be considered certified or as a guarantee ofsatisfactory results by reliance thereon. Nothing contained herein is to be construed as a warranty or guarantee, express or implied, regarding any matter with respect to this product. Because Flowserveis continually improving and upgrading its product design, the specifications, dimensions and information contained herein are subject to change without notice. Should any question arise concerningthese provisions, the purchaser/user should contact Flowserve Corporation at any one of its worldwide operations or offices.

For more information about Flowserve Corporation, contact www.flowserve.com or call USA 1-800-225-6989.

FLOWSERVE CORPORATIONFLOW CONTROL DIVISION1978 Foreman DriveCookeville, Tennessee 38501 USAPhone: 931 432 4021Facsimile: 931 432 3105www.flowserve.com

2003 Fl s C ti I i T s USA Fl s d W st C t ls ist d t d ks f Fl s C ti TP 12D 1 6/03 P i t d i USA

failure analysis of ball valves worcester

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