By Ali Ghanbariannaeeni, Lloyd’s Register EMEA and Ghazalehsadat Ghazanfarihashemi, AMEC Group Ltd. |
Pressure variations resulting from the oscillatory flow patterns found in positive-displacement machinery, especially reciprocating compressors, are referred to as “pulsations.” Found in both liquid- and gas-handling systems, pulsations are a common phenomenon in the chemical processing industries (CPI). Operational problems associated with pulsations include resonance conditions, high vibrations, degradation of support systems and increased risk for fatigue failures caused by dynamic forces. To avoid potential pulsation-related problems in reciprocating compressors and piping systems, there are two design considerations that must be taken into account. The first focuses on minimizing the magnitude of the harmonic forcing functions. The second method examines physical modifications to the piping support or piping layout to mitigate issues related to natural frequencies and harmonics. This article covers the first method in detail.
FIGURE 1. Pressure variations are shown for the inlet and outlet of a reciprocating compressor
FIGURE 2. A compressor’s piston-displacement function over one shaft rotation is shown. The piston- displacement characteristics of a compressor affect the flow-pulse…