MMM testing and failure analysis of fastening bolts on reciprocating compressor cylinder cover

To avoid the serious accidents caused by the failure fastening bolts on reciprocating compressor cylinder cover, a new nondestructive testing (NDT) technology, metal magnetic memory (MMM) testing, was applied to safety evaluating and failure analyzing for the fastening bolts. Based on the dynamic stress calculation of the failure bolts, MMM testing was carried out at workshop. Given are the MMM stress distribution characteristics of the failure bolts and fracture faces. It has been found that the MMM signal variation amplitude of the crack transition zone in the fracture surface is minimal, that of the crack initiation zone is in the middle, and that of the tear fracture zone is maximal. The failure reasons were analyzed with MMM effect. The results of the metallographic examination showed that the validity and feasibility of MMM testing and failure analysis. This means MMM technology is a new, fast and validity method of failure analysis.