Page 280 - Reciprocating Compressors Operation Maintenance

Overhaul and Repair of Reciprocating Compressors 265

try to correct the leakage problem by tightening the jam screw, even to
the point of breaking the valve seat in the cylinder.
Another common cause of cylinder valve seat breaking is not backing
off the valve jam screws when the valve cover is unbolted. The cover is
commonly reinstalled using impact wrenches and with the jam screw not
backed off, too much force is put on the valve, causing the seat to crack.
If visual inspection indicates possible damage to a valve seat, a dye-
penetrant inspection should be done to determine if the seat is cracked.
When a valve seat is found damaged, steps should be taken immediately
to remachine the seat to restore the seating surface. This can be done by
the use of portable boring equipment. It may not be necessary to remove
the cylinder from the compressor.

GASKETS

When reassembling the compressor cylinder assembly, new gaskets
should be used throughout. It is particularly important to replace the gas-
kets for the front and rear heads, water jacket covers, clearance pockets,
and valve covers.
Proper materials must always be used. Room temperature vulcanizing
cement (RTV) or similar material should not be used in place of cut gas-
kets for any joint where fits are employed since the thickness of the RTV
will vary and cause misalignment. The only place where RTV may be
considered for use is on water jacket covers.

WATER JACKETS

After years of operation, water jackets become dirty and fouled, partic-
ularly if jacket water quality is not good and the jacket cooling effect
may have deteriorated considerably. The inside of the jacket walls may
be covered with sand, lime, or magnesium, which interferes with normal
heat transfer and cooling.
The solution to this problem is to clean not only the cylinder jackets
but also the water cooling passages in the front and rear heads. The only
way to effectively do this is by chemically cleaning. Figure 4-19 shows
the correct hook-up for chemically cleaning cylinders and jackets.
Chemical cleaning is recommended at every fourth or fifth overhaul
for normal water conditions and more frequently with inadequate water
conditions.