TP-12D-1

Worcester Control Valves

Failure Analysis of Ball Valves Failure Analysis Of New Valves Features to Evaluate if the Valve has Leakage or High Torque: 1. Look for misalignment of actuator, linkage, or handle. Need 0° to 90° rotation. Stem must be perpendicular to body—no side loads.

Carbon Steel Bolts Bolt Dia.

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

Stainless Steel and Alloy 20 Bolts

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

2. Check body bolting torque; refer to IOM for correct torques. Torque is for nonlubricated bolts. SOLUTION: Using a calibrated torque wrench, check the torque of bolts. Refer to attached chart or IOM. 3. Check flange bolting for proper insert compression. Body seal must be compressed for seat sealing. Slip-on flanges and thick rubber gaskets can affect performance of seal. SOLUTION: Record location of piping supports, obtain photographs and make a sketch. Retorque flange bolts, record style and type of gasket and flange. Discuss data with Flowserve personnel. 4. Normal torque when rotation 0° to 90° and back to 0°. Measure stem torque to open and close. Listen for scraping noises when cycling; there must be no metal-to-metal galling. Compare data to catalog ratings.

TABLE OF CONTENTS Analysis of New Valves . . . . . . . . . . . . . . . . 1 Analysis of Valves in Service . . . . . . . . . . . . . . Photos of Valve Failures . . . . . . . . . . . . . . . . 8 Glossary of Valve Terms . . . . . . . . . . . . . . . 10

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

Flow Control Division

Worcester Control Valves Failure Analysis of New Valves 5. Do a leak test on the valve. Pressure test from the other end of the valve to evaluate second seat (not V-3 ball). If disassembling the valve, mark the upstream and downstream seats and the twelve o’clock position on each seat. SOLUTION: Record leakage data using flow meter or count bubbles; determine if leakage is because of bad seats or damaged ball. Return damaged seat to Flowserve for evaluation; 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 are acceptable, or replace seats and metal parts if necessary. Note, if scratches can be felt on ball, this will cause leakage during normal use. 7. If the valve was cycled or tested at high pressure, there will be a burnishing or contact band from the ball to seat and back of the seat from the valve body. SOLUTION: Determine if the contact is even. Full contact on seat may mean over-pressuring of the valve. Check for proper assembly of the valve. Clean and repair parts as necessary. Do not reuse body seal gaskets. Assure that the S gasket is properly installed. This gasket is not reusable. 8. Evaluate the surface finishes on the seat and the ball. Look for porosity, cracks and imperfections. Contamination during installation or improper handling can cause leakage. SOLUTION: Look at the orientation of the seat and sealing wearpath. Any deformation of soft parts will require complete rebuilding of the valve. If there is any bending or metal deformation, a new valve is required. 9. Check if valve seat was properly assembled. Look for gaps between the seat and valve body from oversized or undersized seats. SOLUTION: Some small seats can be put in backwards preventing proper 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 could cause scratches to stem seals, and for improper surface finish on the pipe ends which could cause leaking 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 seat leakage means metal parts have to be replaced.

2

Failure Analysis of Ball Valves

TP-12D-1

Flow Control Division

Worcester Control Valves 12. Stem nut and locking nut should be properly adjusted for zeroleak stem seal. Look for rough marks inside stem bore or possible galling. Evaluate thrust washer and stem seal for tearing or deformation.

Color Chart for Various Stem Component Materials

SOLUTION: Check that the stem seal nuts have been properly adjusted by flattening out the Belleville washers and back off 1/6 turn. Automated valves require a double locknut, MP44 valves and V51 use heavy, single locknut. Check that washers are not cracked or missing.

Material

Color

Polyfill

Black

Peek

Tan

Graphite

Silver Gray

Carbon-Filled PTFE

Black

UHMWPE

Opaque White

Delrin

Brown

Filled TFE

Off-White

13. Missing parts or bent mounting kits can side load the stem or reduce actuator torque. SOLUTION: Check centrality and alignment of the actuator and stem. Replace parts as necessary. Look for use of proper coupling and slop between stem and coupling and ball and stem for proper closing of the valve.

1A?f" – 2" Size Top-Mount Valves Shown

TP-12D-1

Failure Analysis of Ball Valves

3

Flow Control Division

Worcester Control Valves Failure Analysis of Used Valves NOTE: Assure all system pressure is zero and fluids are drained from valve before loosening any bolts. If fluids are dangerous, perform proper cleaning before valve is removed. 1. Review same causes as new valve. SOLUTION: Record all process conditions and try to determine the date 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, if possible, rebuild and replace soft parts. No piping compound should be in the valve.

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 if the valve was hydrotested and then exposed to freezing temperatures—cavity pressure due to ice can bend metal parts. SOLUTION: Verify temperature, possible system hydrotest and misapplication of the valve. Use V3 vented ball, if necessary, to prevent deformation of the seats. Evaluate flatness of pipe ends with straight edge. No deformation is allowed. Replace valve if necessary. 8. Thermal Effects: If valve is closed and full of liquid (1° temperature rise equals 100 psi in trapped cavity) look for evidence of deformation of seats, body seals, or pressure vessel.

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.

SOLUTION: Check for thread damage or deformation of the body bolts, seats or seals at pipe ends. Replace components as needed.

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

1A?f" – 2" Top Mount Valves Shown

SOLUTION: Determine if there has been welding or painting which would indicate rework of the valve. Look for counterfeit valves with improper components. Determine if alterations have damaged valve. 5. Evidence of metal corrosion or improper seat/seal selection for application. Record pressure, temperature, media and relevant information for analyzing failure. Record pressure at shutoff and throttling pressure drop. SOLUTION: Evaluate the extent of corrosion, re-evaluate material selections, replace complete valve if necessary. Review date of installation and discuss application with Flowserve personnel. 6. Look for possible leak paths through stem seals, between ball and seat, behind seat and possible “wire drawing” of sealing surfaces. Document location of leakage. SOLUTION: Determine where there is a leak path. Replace soft parts. If there is wire drawing or damage to the pipe ends or ball, replace valve as needed. Valve Shown in Closed Position, No Pressure

4

Failure Analysis of Ball Valves

TP-12D-1

Flow Control Division

Worcester Control Valves 9. Crushed ball downstream seat due to water hammer, overpressurization or piping stress can bend metal parts or deform seats and/or balls.

Corrosion Allowance Average Penetration Rate Per Year Code

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 sales drawing or IOM. Wrong stem-to-ball engagement can yield the metal parts or ball won’t cycle. Improper or missing stem seals can affect stem engagement. SOLUTION: Check the ball-stem engagement. Look for bent stems and deformation of the ball or damage to the metal parts. Assure correct assembly of parts.

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Mils

Inches

µm