Failure Analysis of Connection Pipe between Boiler Drum and Upper Collecting Box
Shugen Xu · Pressure vessel Technology · 2008
A connection pipe between the boiler drum and upper collecting box exploded in a company.The chemical compositions,metallographic structure,and mechanical properties of the exploded pipe were first tested,and the experimental results show that the compositions and properties of the pipe steel accord with the requirements of boiler pipe steel 20.Furthermore,the macro-and micro-fracture appearances of the exploded pipe were observed,and many severe serried corrosion pits were found in the inner surface of the pipe,which is the basic reason to induce the accident.The research results further show that the severe corrosion of the pipe might be discovered during the nondestructive testing stage if the pipe thickness was measured after considering the pipe corrosion carefully.In addition,the connection pipe with severe serried corrosion pits must explode during the hydrostatic test if which were done strictly according to Periodic Inspection Rules of Boilers,and thus the disastrous accident might avoid.We suggest that the thickness measurement of the similar connection pipes must be strengthened,especially the connection pipes located in the area of the exploding one should be dissected when they have run close to or over 80,000 hours.Finally the hydrostatic test should be carried out according to Periodic Inspection Rules of Boilers strictly.