Piston rod fracture in natural gas process compressors for underground gas storage: A comprehensive case study

The reliable operation of process gas compressors is critical in the operation of underground gas storage (UGS). The piston rod is a critical moving part of the compressor, whose fracture can lead to serious consequences, including gas leakage or explosion. In this study, simulation and experimental investigations are carried out to analyse the factors contributing to the fracture failure of the piston rod in an actual engineering case in a UGS. Firstly, a three-dimensional computational fluid dynamics model is developed to elucidate the mechanism by which liquidcarry compression imposes significant piston rod overload. It is also established to capture the dynamic pressure changes in the compression cylinder during gas-liquid two-phase compression. A finite element model is then constructed, allowing analysis of the stress distribution of the piston rod in conjunction with the liquid -carry load patterns. Next, the crack propagation of the piston rod is analysed to unveil its effect on the service life during liquid -carry overload conditions. Finally, fracture analysis is performed on the actual fractured components to conclusively determine the root cause of this accident. The objective of this investigation was to enhance the comprehension of potential risks and causative factors leading to the fracture of compressor piston rods, which hope to contribute valuable insights and theoretical fundamentals towards the safety and maintenance of UGS.