Air inlet and discharge valves are vital parts of a compressor and should receive careful attention. When these valves leak, the compressor capacity is reduced and results in an unbalanced stage pressure.

There are several symptoms which signify that an air valve is not functioning properly. A deviation from normal intercooler pressure may indicate a leaking or broken valve. A defective inlet valve above the intercooler will cause a rise in pressure in the intercooler, while a defective discharge valve below the intercooler will cause a decrease in the intercooler pressure. An unusu-ally hot valve cover is a sign of valve trouble.

Dirt is generally the cause of leaking valves.

The source of valve trouble can usually be traced to dirty intake air; the use of excessive or improper cylinder oil; or excessively high air temperature, resulting from faulty cooling. A periodic inspection and cleaning of valves and valve passages will minimize and perhaps prevent the occurrence of air valve troubles. The frequency for cleaning valves must be determined for each installation. The air valves are easily accessible and are removed by first loosening the valve cover plates. Then the valve and valve unloader, if installed, may be lifted out. Each valve should be marked so that it may later be returned to the same opening from which it was removed.

Dirt or carbon can usually be removed from valve parts without disassembling the valve. If disassembly is necessary, notice should be taken on how the various parts are arranged so that the proper relationship will be kept when the valve is reassembled. To remove carbon from valve parts, soak each part in kerosene and then brush or scrape lightly. After drying and reassembling the valve parts, test the valve action to be sure that the valve opens and closes freely.

Before air valves are replaced in a cylinder, inspect the gaskets. If the gaskets are made of materials other than copper, and are damaged, change them. Copper gaskets should always be replaced. Since it is often difficult to distinguish between suction and discharge valves, use extreme care when inserting valves in the cylinder. Make sure that suction valves open TOWARD, and discharge valves AWAY FROM, the center of the cylinder. Otherwise, serious damage or loss of capacity will result. If special locknuts are not pro-vided to seal against leakage at the threads of the valve setscrew, place a turn of solder or fuse wire around the screw and set down into a recess by the locking nut.