Page 212 - Reciprocating Compressors Operation Maintenance

198 Reciprocating Compressors: Operation and Maintenance

STANDARD VALVE TYPE DOUBLE DECK VALVE TYPE
FIGURE 3-54. Suction valve uriloaders.

to the valve unloader mechanism. The proper setting is such that the end
of the diaphragm stem has a maximum of 14" clearance with the unloader
piston or fingers (in the case of the double-deck type) when these are in
their extreme upper positions assembled in the cylinder.
The following procedure is suggested in order to check and establish
the proper setting of the diaphragm stem with the unloader. Remove the
valve cover with the diaphragm head mounted thereon without loosening
the jam screw. Measure the distance the diaphragm stem projects beyond
the end of the jam screw. Also measure the distance, through the hole in
the unloader cylinder cover from the top of the cover to the top of the
piston or finger. These distances should be equal or the diaphragm stem
projection distance slightly less (Me" maximum).
If such a condition does not exist, the support studs should be adjusted,
lengthened or shortened, to obtain this condition. With this setting made,
the valve cover can be reinstalled. Upon reinstallation, the jam screw
should be loosened and retightened after the valve cover is securely
tightened on its seat gasket.
Whenever an unloading valve assembly is replaced in the cylinder suc-
tion port, the gasket should be in good condition and the valve should