轻烃站原料气压缩机A机进气阀阀盖螺栓的断裂原因

Fracture Reason for Bolts of Inlet Valve Cover of Feed Gas A Compressor of Light Hydrocarbon Station

通过对某油田轻烃站原料气压缩机A机进气阀阀盖螺栓的断口形貌、化学成分、显微硬度、显微组织、受力情况等进行分析,讨论了螺栓失效的原因。结果表明:螺栓的断裂性质为疲劳断裂,疲劳裂纹在螺纹根部萌生;螺纹根部存在因加工不当而出现的缺口、凹坑等缺陷,缺陷处易产生应力集中而成为疲劳裂纹源,在压缩机工作时产生的交变应力作用下微裂纹扩展,并最终导致螺栓的断裂;建议在螺栓加工过程中,采用表面喷丸、渗碳、渗氮等工艺在螺纹根部表面引入残余应力,严格按照高强紧固件的热处理要求进行调质热处理,严格按照压缩机的使用要求紧固螺栓,并定期检查和更换螺栓。

The failure causes of the bolts of inlet valve cover of feed gas A compressor of light hydrocarbon station in an oilfield was investigated by the analysis of fracture morphology,chemical composition,microhardness,microstructure and stress condition.The results show that the fracture mode of bolts was fatigue fracture,and fatigue cracks originated from the thread root.The thread root had some defects such as notches and pits due to improper processing;the positions of defects generated stress concentration easily and became the fatigue crack initiation.Micro-cracks propagation occurred under the interaction of alternating stresses during the operation of compressor,and bolts eventually fractured.It was recommended to introduce residual stresses on the surface of thread root by surface peening,carburizing or nitriding,to carry out quenching and tempering heat treatment strictly following heat treatment requirements of high strength fastener,to tighten bolts strictly following operating requirements of compressor,and to inspect and replace bolts regularly.