17 - Combined lube and seal systems

Abstract

This chapter elaborates the different aspects of combined lube and seal systems. The function of a combined lube oil and seal oil system is to continuously provide clean lube oil and seal oil to each specified bearing and seal interface at the required differential pressure temperature and flow rate. It should be noted that some older types of combined lube and seal systems use the atmospheric seal to directly supply lube oil to the journal bearings of the compressor. In this case, there would not be an atmospheric seal drain rather the compressor journal bearing drain would include the flow from the atmospheric bushing. Preventive maintenance procedures on all combined lube and seal oil systems should include frequent oil checks of seal oil drainer for the exit of oil to confirm that oil being returned to the lube/seal reservoir will not deteriorate the total oil supply, and does not contain significant amounts of entrained vapor. High pressure applications typically require seal oil supply pressure in excess of 1000 psi. The additional cost of using a pressure breakdown system in this application would be prohibitive. Safety switches or transmitters are installed to prevent starting of a booster pump under low suction pressure conditions.