Flowserve 1878 Swing Check Valve - Manual (Page 8)

1878 Swing Check Valves FCD ADENIM0006-00
8
9.0 Maintenance Instructions
(Continued)
9.1.2 Reassembly (Continued)
The nut should be tightened evenly using a criss-cross pattern as shown in Figure 1. Tighten all of the nuts to
1/3 of the recommended value initially. Then repeat the sequence raising the torque to 2/3 of the full torque.
Finally, torque all the nuts to the recommended value following the criss-cross pattern. It is essential that the
flange faces remain parallel and all the bolting has uniform tension. Failure to achieve this may cause gasket
weepage when the joint is subjected to operating pressures and temperatures.
NOTE: As an extra aid to ensure proper bolt tightening, the valve bonnets have been permanently
marked with sequence numbers for bolt tightening.
9.2 Lapping Procedure
After the valve has been disassembled, a visual inspection of the seating surfaces of the Discs (004) and Seat Ring
(013) can be made to determine if lapping is necessary to remove any minor scratches on these parts prior to
assembling the valve. IF lapping is necessary, it may be accomplished in the following manner:
(1) Remove the Resilient Seat (306) (if equipped). Never lap the disc with the resilient seat in place.
(2) Place lapping compound between the Disc (004) and the Seat Ring (013) and, by hand, rotate the Disc (004)
in a circular motion against the Seat Ring. Check periodically for signs of defects. Repeat this process until
the defect is removed.
(3) A "medium" grade lapping compound should be used for the first and successive applications. A "fine" grade
compound similar to "Clover A Grit No. 280" should be used for the final lapping process.
9.3 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)
B. Leakage Between the Body (001) and Bonnet (002)
This would be a good indication that the Gasket (100) is worn out or damaged. Replacement of gaskets is set
forth in Para. 9.1. Another source of the trouble might be that the bonnet studs and nuts are loose - if this
should be the case - tighten them securely.