Often, compressors in the refrigeration and air conditioning fields have forced oiling systems. These compressors are usually over 5 horsepower (hp). They contain an oil pump located at the end of the compressor’s crankshaft (Figure 1).
The oil pump is actually keyed into the compressor’s crankshaft, which supplies power to turn the oil pump (Figure 2). Oil pumps can be of the gear (Figure 3) or eccentric type. The star gear in this type of pump actually squeezes the oil to a higher pressure. The added pressure that the star gear puts into the oil can be referred to as the net oil pressure. (Figure 4 shows the star gear disassembled from the oil pump and out of its seat within the oil pump.)