Tube burst and straight tube deformation occurred on T91 steel pipes in front plane and TP347H steel pipes at outlet of the high temperature reheater in a power plant

respectively.Thus

several tests were conducted to find out the reasons

such as field investigation

macro-morphology observation

chemical composition analysis

metallographic observation

hardness tests

room-temperature and high temperature tensile tests.The results showed that the tube burst was due to crack in fillet weld where the hanger plate was connected to the base material.The crack was induced by high hardness of fillet weld of the hanger plate

high welding criterion

improper welding structure design and PWHT process.Moreover

it was also promoted by tube panel stress related to the tube system structure design.The curvature of the straight tube at outlet of the high-temperature reheater was related to the tube panel constraint and low high-temperature strength of TP347H steel.