Reciprocating compressors are positive-displacement types having one or more cylinders. Each cylinder is fitted with a piston driven by a crankshaft through a connecting rod. As the name implies, compressors within this classification displace a fixed volume of air or gas with each complete cycle of the compressor. This machine is more difficult to analyze because of the combined rotational and linear motions that are required to increase the discharge pressure hence increase the difficulty to investigate the vibration problems. These unique operating dynamics combine rotating and linear motions that generate complex vibration signatures.