CAUSES ANALYSIS OF CRACKS AT A PREHYDROGENATION REACTOR WELDS

摘要

The cylinder of prehydrogenaton reactor of a refinery was made of complex steel plate, the material of base layer is SA387Gr11C12, and that of over layer is SA240TP321. after about 4 years service, many inner cracks were founded at the circumference welds of the prehydrogenating reactor cylinder by non-destructive inspection. The cracks were 35～50mm long, they all propagated along the vertical direction to the welds. In order to explore the crack causes, the chemical composition of base layer and the over layer were examined，the heat treatment process and weld process parameters of the reactor were analyzed, the sensitive index of the weld cracks of the reactor cylinder materials were calculated. It was concluded that the major factors of the weld crack of the cylinder were: lack of enough time for the high temperature temper insulation; bigger sensitive index of the weld cracks of the reactor cylinder; not high enough preheating temperature before welding and the weld complexity of base layer and over layer. Some heat treatment and weld process parameters were proposed for the reference of the similar reactors.