Technology today is such that it is possible to complete very complex engineering feats with the push of a button on a computer. In many ways, this is good; however, in some cases, the basic engineering underpinnings are not completely understood. This short course will explain from the ground up how reciprocating compressors are sized and clearanced to meet the specific needs of the pipeline operator. It will explain how to calculate clearance, capacity, compressibility, rod load, unloading, valve and parasitic losses and other related compressor terms. A discussion of P-V curves, horsepower, pulsation and rod reversal will also be provided.