Compressor Operating Conditions & Loading: A Torsional Perspective
A gas compression system's torsional response is very sensitive to the reciprocating compressor configuration and operating conditions. Simply changing the shaft speed, unloading a cylinder, repositioning a cylinder throw on the crankshaft, or accepting different gas conditions can significantly affect the system torsional response and corresponding shaft stresses. If a reciprocating compressor system is subjected to a range of demand or field gas conditions and is operated in various loading configurations, the torsional response and shaft stresses at each compressor operating point must be acceptable. Since it is not generally feasible to calculate the torsional response at each operating point, appropriate torsional design cases must be determined. Case studies and basic torsional vibration theory provide insight to the sensitivity of a system's torsional response to operating conditions and loading. Compressor performance simulations illustrate the relative influence which different operating conditions and loading have on the systems' torsional response and shaft stresses. Guidelines for determining the torsional design cases are defined.