Abstract: An apparatus for monitoring the condition of a pressure relief safety valve, which has a magnetic ball shiftable from a home position by fluid under pressure when the relief valve opens, and an adjacent sensor responsive to shifting of the ball to provide a signal representing an open valve.

Abstract: A compressor oil management and separation system for refrigeration installations, including a main oil storage tank, a pump, valves and remote control means for selectively directing oil from the tank to any one or more of several compressors. Oil separation units are connected for collecting oil from low pressure refrigerant and delivering such separated oil to the tank for reuse or disposal. Each oil separation unit includes a collection vessel, valves for selectively alternately connecting the vessel with low pressure refrigerant and the tank, and means for increasing pressure within the vessel for forcing oil toward the tank.