废热锅炉与乙烯裂解炉出口管连接法兰泄漏原因探讨

Discussion on Leakage Reason of Flange Connectting Outlet Pipe of Ethylene Cracking Furnace with Waste Heat Boiler

针对废热锅炉与乙烯裂解炉出口管连接法兰经常出现泄漏的问题,对法兰外表面温度进行了测量,并采用有限元分析软件ANSYSY模拟了裂解炉炉管对法兰的作用力。由法兰测量温度计算出螺栓的热应力较大,同时发现法兰存在着明显的周向温差,这些因素会严重影响法兰的密封性能。数值模拟结果表明:炉管对法兰的作用力主要是沿Y方向上的拉力和绕Z轴的弯矩。操作时螺栓的热应力与辐射段炉管对法兰作用力引起的螺栓最大附加应力之和过大,因此,在法兰、垫片和螺栓设计时必须重视这些影响因素。螺栓套筒可以起到补偿螺栓热应力的作用,当螺栓和套筒做成等截面、同材料、同温度、等长度时,螺栓在有套筒时承受的附加热应力仅为无套筒时的1/3。采用套筒可以有效改善法兰密封性能,具有实际意义。

To solve the sealing problem of the flange connectting the ethylene cracking furnace with the waste heat boiler,the surface temperature of the flange was measured,and the finite element analysis software ANSYS was used to simulate the additional force that the outlet pipe acted on the flange in this paper.There is a big temperature stress calculated from the measured surface temperature,and there is a clear difference in circumferential temperature of the flange.These factors affect the sealing performance.Numerical simulation shows that the additional forces are mainly Fy and Mz.Since the additional stress caused by the temperature stress and additional force is large,they must be taken seriously.Bolt sleeve plays a role of compensation of thermal stress,and the temperature stress can be reduced to 1/3 when adding a sleeve which has the same material,temperature and length with the bolt.It can be used to improve the flange sealing performance effectively with practical significance.