Search Results (2)

Ensuring the reliability of process gas compressors is critical for underground gas storage, as piston rod fractures can lead to serious accidents, such as natural gas leaks or explosions. On-time monitoring and early detection play a vital role in preventing catastrophic consequences, minimising costs, and reducing production losses due to unplanned downtime. This study presents a novel accelerated life-testing method designed to replicate the fracture events of reciprocating compressor piston rods. By accelerating the induced crack initiation and propagation to the final fracture, comprehensive analyses of the fracture results are performed to reveal the piston rod fracture mechanism and the resulting secondary damage to the unit. The research further presents an innovative approach for identifying piston rod crack propagation by means of acoustic emission. Through kinetic analysis and time–frequency domain analysis, the study elucidates two mechanisms responsible for triggering crack signals during the compressor operation: the contact impact between the crosshead pin and the bearing due to the piston rod load reversal, and crack propagation occurring before the maximum tensile load is reached. In addition, the study identifies the piston rod crack expansion signal frequency band and achieves a high-sensitivity identification of crack dynamic growth by extracting signal sub-band features associated with crack propagation. Then, a prediction model of the fatigue crack growth rate was established based on the AE energy release rate, which provides a quantitative assessment of dynamic crack propagation during compression. This method aims to provide a maintenance strategy for piston rod fractures, thereby increasing the operational safety of critical dynamic equipment in underground gas storage. Full article

The piston rod of the hydraulic jack was a kind of artillery alloy structural steel of 40Cr and its surface was the chromium plating layer. The piston rod worked for a while; the defects of corrosion pit and peeling appeared on the chromium layer. A stereo-microscope, metallographic microscope, and scanning electron microscope (SEM) were used to observe the macromorphology, micromorphology, and microstructure of the failed parts. The composition analysis was performed by the energy dispersive spectroscopy (EDS), and a Vickers hardness tester was used to measure the hardness. The results showed that pores and penetrating cracks existed in the chromium layer, leading to the corrosion medium invading the interface and forming a corrosion source. Then, the corrosion intensified, resulting in the bubbling, cracking, and peeling of the chromium layer. More O and minor S elements were detected in the corrosion pit. Finally, the fracture of the chromium layer was a 45° angle destruction mode. The peeling of the chromium layer was caused by the pores and microcracks, working medium, and poor working environment. Some suggestions were put forward to prevent the peeling of the chromium layer. Full article