供汽管道法兰反复泄漏原因分析及处理

Cause analysis and improvement measures of repeated flange leakage in steam supply piping

某电厂供汽管道投产后多组电动闸阀法兰较短时间内发生泄漏,虽采取带压堵漏及更换法兰等措施,泄漏仍频繁发生。对此,本文采用CAESARⅡ2011软件建立了供汽管道应力计算模型,并根据当量压力法与临界弯矩法计算了法兰当量压力和弯矩,结果表明:管道最大一次、二次应力均在允许范围内,法兰当量压力和弯矩均超过设计压力和临界弯矩;管道布置结构引起的法兰处轴向力及弯矩过大是导致泄漏的根本原因。通过采取新增限位支架、改变固定支吊架位置及将限位支架改造为带间隙限位支架等措施,增加了管道的柔性,从而有效降低了法兰处的轴向力与弯矩。该方案实施一年多法兰未再发生泄漏事故。

Leakage occurred in multiple electric gate valve flanges within a short time after the heating pipes were put into service in a power plant.The leakage still occurred frequently although some measures were taken,like pressure seal and flange replacement.To solve this problem,the CAESARⅡ2011software were applied to establish the stress calculation model for the heating pipes.Moreover,the equivalent stress and bending moment of the flange were calculated by the equivalent stress method and critical bending moment method.The results show the maximum primary and secondary stress of the pipeline were all within the permissible range,while the equivalent stress and bending moment of the flange exceeded the allowable value.On the basis of calculation and analysis,we can draw the conclusion that oversize axial force and external bending moment on the flange of piping layout were the ultimate reason for flanges leakage.After some measures were taken to increase the flexibility of the piping,such as adding the stopper support,modifying position of the fixed hanging bracket and changing the stopper support with no gap into with gap,the axial force and external bending moment were reduced,and no leakage occurred after one year＇s operation.