Smaller refrigeration compressors, usually under 3 horsepower, typically have splash-type lubrication systems without an oil pump. These compressors often have an oil scoop that flings oil throughout the compressor’s crankcase, causing an oil fog that lubricates the bearings, wrist pins, pistons, and rings.
However, larger compressors will have forced lubrication oiling systems. These compressors contain an oil pump located at the end of the compressor’s crankshaft. This oil pump is driven directly by the compressor’s crankshaft and rotates at the same RPMs as the compressor. The oil is forced under pressure through holes or oil galleys drilled in the crankshaft, piston rods, wristpins, and supporting bearing structures and surfaces. The oil then drops to the crankcase to again be picked up by the suction of the oil pump. Often, the oil is filtered by a fine mesh screen and then enters the suction of the oil pump to be pressurized and start the process over again.