of the rod and the crank pin bearing boxes; (2)by adding or removing shims between piston andsocket type wrist pin boxes; (3) by screwing in orbacking out the wrist pin adapter, in compressorshaving a threaded wrist pin adapter; (4) by turn-ing the piston rod in or out of the cross head, indouble-acting pistons equipped with piston rodand cross head. In some compressors, the pistonclearance is nonadjustable.Control DevicesBecause of the great variety of control,regulating, and unloading devices used with com-pressors, detailed instructions on their adjustmentand maintenance must be obtained frommanufacturers’ technical manuals.When a control valve fails to work properly,disassembly and a thorough cleaning is usuallynecessary. Some control valves are fitted withfilters filled with sponge or woolen yarn, to pre-vent dust and grit from being carried into the valvechamber and to remove gummy deposits whichcome from the oil used in the compressorcylinders. Replace the filter element with thespecified material each time a valve is cleaned.WARNING: DO NOT use cotton as a filterelement because it will pack down and stop theair flow.Since relief valves are essential for the safeoperation of a compressed air system, they mustbe kept in satisfactory working condition at alltimes. Relief valves should be set as specified bythe manufacturer, and tested by hand each timethe compressor is started. Periodically, the set-ting of relief valves should be checked by raisingthe pressure in the space which they serve.Lubricating and Cooling SystemsThe maintenance procedures for lubricatingand cooling systems in air compressors are similarto the procedures used for lubricating and cool-ing systems in internal combustion engines. Forair-cooled compressors, steps must be taken tokeep the cooling fins clean. Oil and dust act asinsulators and, if allowed to collect on the fins,will prevent heat transfer.In general, the lubricating system of a com-pressor will give you little trouble if the follow-ing steps are taken:1. Keep the reservoir oil at the prescribed levelin order to maintain proper oil temperature.2. Change crankcase oil periodically, flush thecrankcase, and clean the oil filter.3. Maintain proper lube oil pressure by keep-ing the oil pump in good working condition andby adjusting the bypass relief valve.4. Keep the oil cooler free from leaks to pre-vent oil contamination and emulsification.5. Inspect cylinder lubricators.a. When Navy Symbol 9000 series oil isused for compressor cylinder lubrication, the sightflow indicators should be filled with glycerinealone.b. When Navy Symbol 2000 series oil isused for cylinder lubrication, the sight flow in-dicators should be filled with a mixture of 50%distilled water and 50% glycerine.6. Keep the lubricator in proper adjustmentfor the specified quantity of oil feed.The general requirements for care andmaintenance of compressor cooling systems areas follows:1. Intercoolers and aftercoolers should be in-spected periodically.2. Collections of gummy oils or tarrysubstances on the sides of cooler tubes should beremoved by washing the tube nests with a cuttingsolution. Be sure that the nests are completely drybefore reassembly.3. Any leaks in tube nests must be repaired;otherwise, water will leak into the compressorwhile it is secured, and air will leak into the waterside during operation.If during operation, a water relief valve on thecoolers blows while the cooling water pressure isnormal, it is evident that a tube in the cooler isruptured. The compressor should be secured im-mediately and the tube plugged, if possible.4. Cylinder water jackets should be inspectedand cleaned periodically with a cleaning nozzle.ENGINEMAN 1 & C7-4
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