Flowserve 800 Piston Lift Check Valve - Manual (Page 10)

9.0 MAINTENANCE INSTRUCTIONS (Continued)
9.3.3 Resilient Seat Assembly (if so equipped)
a) Carefully place the resilient seat over the disc.
b) Reassembly of the balance of the assembly is the reverse of that
described in 9.1.3.
c) Use nuclear grade thread lubricant on the threads, making sure that
it does not come in contact with the resilient seat material.
d) The disc skirt (005) is to be screwed firmly against the disc (004)
shoulder prior to installing the retaining ring (245).
9.3.4 Reassembly of the valve is accomplished by inserting the disc or disc
assembly (004) and spring (429), followed by the bonnet (002) and
pressure seal gasket (030). Use a nuclear grade thread lubricant on the
threads, making sure that it does not come in contact with the resilient seat
material. Then screw in the gasket retainer (033). The bonnet capscrew
(216) is then threaded into the bonnet through the hole in the retainer
(033). A maximum of 5 ft-lbs of torque should be exerted on the bonnet
capscrew. Insert the anti-rotation pin (258) in hole in top of the body
(001).
NOTE: Consolidation of graphite during initial system pressurization is normal
and will often cause the bonnet capscrew to become finger tight or
even loose.
9.3.5 Retorque the bonnet capscrew to 50 to 60 inch-lbs. when the system is
initially pressurized to ensure that the bonnets will not move out of the
sealed position when the pressure is relieved.
9.4 Trouble Shooting
A. Leakage Between the Disc (004) and Seat Ring (013)
This could be an indication that there is foreign matter on the
seating surfaces.
Disassemble the valve and remove the source of the trouble. If no
foreign matter is found, inspect the seating surfaces of the valve for
signs of a scarred or damaged seat - in which case the seating
surfaces of the Disc (004) and Seat Ring (013) should be lapped
until no visible defects remain. (Refer to Para. 9.2)