Stress Analysis of Header Tube Seat Under Complex Service Conditions

Under flexible operation, the boilers of thermal power plants frequently start and stop, and load up and down, accompanied by alternating changes in temperature and load, resulting in frequent cracking of the header tube seat. This article uses the superheater header as a template to establish a finite element model containing the header, tube seat fillet welds, and tube joints. The temperature and stress fields of the tube seat during the process of load increase and decrease of the unit are analyzed. The results show that the temperature balance speed of the header is relatively slower during the load lifting process, while the tube joints balance more quickly. During the process of lifting and lowering the load, the maximum thermal stress in the tube seat area occurs at the weld bond line. The mechanical stress is mainly affected by the pressure fluctuations inside the tube.