GREASE AND OIL COOLING
Although small compressors may be able to provide adequate lubrication of the moving parts splash lubrication, almost all piston compressors used in industrial refrigeration practices provided with forced lubrication. Positive-displacement pump draws the oil from the crankcase and supplies oil for bearings, cylinder walls and shaft seal, many compressors. Most pumps are driven compressor off shaft and some irreversible, which fixes the necessary direction of rotation of the compressor.
Several auxiliary system of lubrication of the compressor oil heater, crankcase heater, the separator for oil removal of the discharge gas, security and cutouts. Especially on large compressors, oil passed through a water-cooled heat exchanger where it is cooled by oil. The rate of water flow for cooling requires about 10 l/min (several gallons per minute). Another recommendation is to install water-water flow such that the outlet water temperature of about 45C (113F), and then rely on the compressor manufacturer provided cooler is large enough to support a satisfactory temperature oil this flow rate.
Typical oil temperature during operation is 50C (122F).
The crankcase heaters automatically come into service during shutdown of the compressor. If oil is allowed to become cool during shutdown, the refrigerantespecially halocarbonswill be dissolved in the oil. After downloading the refrigerant boils off, causing oil foaming and possibly oil run from the compressor.
Type of oil separator is traditionally on the discharge line of reciprocating compressors of a small ship with sharp changes of direction of the oil-Laden refrigerant individual drops of oil, which are then periodically returned to the compressor crankcase. The oil concentration, leaving this type of the separator in the range from 50 to 80 packs / minute. When oil-injected screw compressors appeared they required a much more efficient separator, so the Association type, which is discussed in more detail in Chapter 5, was developed. Association separator reduces the concentration of oil about 5 ppm. This type of separator is also now available for reciprocating compressors and is quite widely used and new installations.
Typical security cuts associated with the oil system are those that shut off the compressor at high oil temperature or low oil pressure happen. Oil pressure cutout usually feels differential pressure pump, which, as a rule, should be higher than about 100 kPa (15 psi)...
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