Because of the great variety of control, regulating, and unloading devices used with compressors, detailed instructions on their adjustment and maintenance must be obtained from manufacturers technical manuals.

When a control valve fails to work properly, disassembly and a thorough cleaning is usually necessary. Some control valves are fitted with filters filled with sponge or woolen yarn, to pre-vent dust and grit from being carried into the valve chamber and to remove gummy deposits which come from the oil used in the compressor cylinders. Replace the filter element with the specified material each time a valve is cleaned. WARNING: DO NOT use cotton as a filter element because it will pack down and stop the air flow.

Since relief valves are essential for the safe operation of a compressed air system, they must be kept in satisfactory working condition at all times. Relief valves should be set as specified by the manufacturer, and tested by hand each time the compressor is started. Periodically, the set-ting of relief valves should be checked by raising the pressure in the space which they serve.