Page 228 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

210 Major Process Equipment Maintenance and Repair

One should watch that ported plates are located on guard so that
locating dowels are on each side of “land” between milled ports on
plates. Dowels prevent plate from rotating (Figure 5-13). When an
indexing dowel is used, the dowel must be aligned with index hole
in valve plate to prevent plate rotation.
4. For suction valves, hold plates in position on the guard (10) with
special valve clips or T-bolts and install the valve seat (1 1) over
stud (7) onto the guard. For discharge valves, install valve guard
(10) over stud (7) onto valve seat (11). Alignment dowel (9) in
guard (10) must align with hole in seat (1 1).
5. Install Drake locknut (8) on valve stud finger-tight and remove spe-
cial clips or T-bolts. Tighten Drake locknut as recommended in
parts list drawing if given, or per manufacturer’s torque recommen-
dations.
6. Check valve plate operation by inserting a screwdriver or similar
tool through the valve seat ports, forcing the valve plates off the
seat. Repeat this at several points on each plate to assure that plates
are free to open and close. Failure of the plate to unseat indicates
that plate is not aligned with dowels in guard, and the valve must be
disassembled.
7. Install assembled valve in cylinder.
Imrullurion of the valves in the cylinder must be executed with the
greatest care. Do not install a suction valve in a discharge pocket or vice
versa. Such an installation could result in excessive internal cylinder
pressures , creating an extremely hazardous condition.
One should proceed as follows:

1. Install a gasket on the valve seat or guard.
2. Carefully enter the valve into the cylinder pocket. Special tools are
available for lifting and installing large valves.
3. Single deck valves are usually installed with the cage. Double deck
valves and gas-operated plug-type unloader valves require installa-
tion of the cage after the valve is located in the pocket unless valve
is threaded into cage or cage is part of valve assembly.
4. With the valve and cage installed, tighten two set screws near the
top of the cage to hold the assembly in position. Do not tighten the
set screws excessively; this will damage the cylinder pocket. Safety
wire the set screws to prevent loosening during operation.
5. Place a gasket on the cage and install the valve cap, clearance bottle
or unloader bonnet. Tighten nuts to parts list drawing specifica-
tions, if given, or refer to torque recommendations.
6. Some valve caps may have the 45 O chamfer while some may have a
“J” groove seal. Neither design should be over-tightened, but with