Seat Leakage on Tilted Disc Check Valves

1
Seat Leakage on Tilted Disc Check Valves
2
Seat Leakage 24 TD Check Valve

• The problem consistently occurs with low spots in
  various areas of the seat
• Low spots are typically .004 _at_ 1030-1 and .004 _at_
  5-7 positions
• The seat is 5 degrees from vertical,  and it is
  inset from the Pressure Seal Area another _at_ 3-4
  inches
• The problematic TD Checks seem to range from 12
  to 24

3
16 TD Check Valve As Found

• Brief condition of the valve after the last
  disassembly and attempted repair (May 2003).
• A first feeler gage test showed
• 1) 0" at 1200 and
• 2) 0.002" at 300, 600 900.
• After cleaning and re-performing the feeler gage
  test these values changed to
• 1) 0" at 1200,
• 2) 0.002" at 600
• 3) 0.006" at 300 400, and
• 4) 0.003" at 900.
• It is postulated that this was due to the work
  performed in 1998

4
16 TD Check ValveAs left

• In 2003, the lapping plate and machine did not
  work well. The lapping machine was not powerful
  enough to drive the disc. As such part of the
  lapping had to be done by hand. As-left feeler
  gage test after machine/hand lapping was
• 1) 0.0015" at 300 400
• 2) 0.001" on remaining area
• Although these latest values appeared acceptable,
  it is suspected that the valve is still leaking
  based on system performance
• To prevent water hammer effect, the LPCS system
  is required to remain pressurized for a minimum
  of 5 minutes without the assistance of the keep
  fill pump. We are not able to achieve this
  requirement
• Volume lost is insignificant, however, the system
  would not remain pressurized to our satisfaction

5
Rectifying Tilted Disc Check Valve Seat Leakage

• Mount the pilot guide
• Slide Brace flush to seat aligning parallel with
  seat
• Remove Slide Brace when guide is fastened
• Slide assembly plate into bearing case
• Assembly plate connects pilot guide to drive head
• Bearing case allows movement to drive head with
  30 angle segments towards the seat

6
Final Set up to Lap 30 TD Check Valves
rectifying seat leakage removing Low Spots on
valve seat
30 Angle heads
30
Bearing Case
Parallel Bracket
Guide Pilot
Illustration
7
PW machine for major damage Warped valve seat
8

• Revolutionizing
• the Valve Repair Testing Industry