Thursday, September 18, 2008
Oil level monitoring controls
Maintaining proper oil level is of primary importance for a long compressor lifetime. Especially when paralleling compressors in compressor pack applications, maintaining sufficient oil in the compressor’s crankcase becomes difficult. A simple way of balancing the oil level in parallel compressor arrangements is the use of oil equilibrium lines. These systems are also referred to as passive systems. However, passive systems require individual tailoring for each application and they only perform satisfactorily under more or less constant operating conditions. Particularly in refrigeration applications with varying operating conditions and defrost cycles an active means of oil level management is a must in order to ensure reliable compressor operation. An additional benefit of active systems is that, apart from oil balancing, they normally also monitor the oil level and provide alarming capabilities. This is a particular benefit for scroll compressors which, due to the lack of an integral oil pump, do not have a differential oil pressure switch as conventional compressors have. The OMB is a self-contained system which provides both functions, oil level monitoring and oil level balancing, for active oil level management systems. The OMB system is applicable to low and high pressure oil management systems. Traditional oil level management systems work with a low pressure oil reservoir. The oil is kept at a pressure slightly above suction pressure by a differential pressure valve.
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