The Dynamics of Reciprocating Compressor Valve Springs
The valves in reciprocating compressors use springs to control the timing of the valve closing. These springs are subjected to dynamic loading by the motion of the valve element. The element motion is periodic but includes rapid acceleration and deceleration. It can therefore excite a wide range of frequencies in the spring. The resulting spring surge creates high stresses and is a major contributor to premature spring failure. Valvefailures are the most common reason for unscheduled compressor shutdowns. The valve springs are the most common source of these valve failures. Therefore, valve spring life is of utmost importance in attaining increased compressor reliability. This paper discusses two approaches to calculating the spring stresses caused by the surge. The first is an approximate method that considers only torsional deflection of the spring wire and neglects end coil effects. The second is a more complete analysis that uses both kinematics and FEA simultaneously to replicate the springs response to the dynamic loading. The results of the two methods are compared and their usefulness in preventing spring failures is discussed.