Page 226 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

208 Major Process Equipment Maintenance and Repair

Valve plates can be installed with either side facing the valve seat.
Valve plate failure always results in breakage and new plates must
be installed.
Damped valve plates must be checked for freedom of movement
and clearance in the guard grooves and channel valve plates must be
checked on the guard ribs. Rotate each plate one full revolution. If
plates do not turn freely they must not be used. After assembly of
the damped plate into the guard, move the plate sideways as far as it
will go. The clearance at any point between plate and guard should
not exceed .011 in.
After assembly of the channel plate over the guard rib, move the
channel sideways as far as it will go. The clearance at any point
between guard rib and channel should not exceed .007 in.
One reputable compressor valve repair shop offers the following in-
spection service:

1. Each valve is identified.
2. Each valve is dismantled and inspected for wear or breakage. An
inspection report is issued.
3. Seats, guards, bolts, etc. are cleaned with a vapor blaster.
4. Seats and guards are inspected for cracks.
5. Seats and guards are remachined to OEM* specifications and, if
necessary, metalized before machining. Seats are lapped or concen-
trically ground.
6. Each valve is assembled. Only OEM parts are used.
7. Each valve is function tested, plus two leakage tests: (a) liquid-fill,
observe for 1.5 minutes and slots of seat must still be half full (b)
connect to metered air supply system.
8. If the valve contains steel parts subject to corrosion, it is dipped into
rust-preventing oil and wrapped.
9. Each valve is identified by a sticker on the wrapping.

Reassembly of the valve takes place in the following order:

1. Replace valve stud bolt-if removed-by turning it firmly into
guard (suction valve) , or seat (discharge valve).
2. Reassemble the valve by first inserting springs in recess in guard.
3. Position valve plates (4 and 5) on springs (13) and depress plates. Hold
plates and springs in place by installing special valve plate clips. See
Figure 5-12-or, if special retaining T-bolts are used, see Figure 5-13.

* Original Equipment Manufacturer