Reasons for Cracking of Nozzle Socket of Hot Section Drain Pipe of a660 MW Ultra-supercritical Unit

LIU Ming; LIU Qi; BAI Jia; CHEN Rui

doi:10.11973/jxgccl202102016

Materials and Mechanical Engineering > 2021 > 45(2): 90-95. > DOI: 10.11973/jxgccl202102016

LIU Ming, LIU Qi, BAI Jia, CHEN Rui. Reasons for Cracking of Nozzle Socket of Hot Section Drain Pipe of a660 MW Ultra-supercritical Unit[J]. Materials and Mechanical Engineering, 2021, 45(2): 90-95. DOI: 10.11973/jxgccl202102016

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Reasons for Cracking of Nozzle Socket of Hot Section Drain Pipe of a660 MW Ultra-supercritical Unit

1. Huadian Electric Power Research Institute Co., Ltd., Hangzhou 310030, China;
2. Hubei Huadian Jiangling Power Generation Co., Ltd., Jingzhou 434000, China

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Received Date: March 22, 2020
Revised Date: January 14, 2021

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Abstract

Abstract

After short operation of the 660 MW ultra-supercritical unit of a thermal power plant, the nozzle socket of the drain pipe cracked in the hot section, causing steam leakage. The chemical composition, hardness and microstructure of the nozzle socket were analyzed. A three-dimensional solid model was established according to the actual layout of the pipe, and the force of the structure was simulated and analyzed by the thermo-solid coupling finite element method. The results show that the chemical composition, hardness, and microstructure of the nozzle socket met the requirements. The maximum stress obtained by the finite element simulation was located at the lower edge of the connection weld between the nozzle socket and the main pipe, which was consistent with the actual cracking position. The cracking was due to the limited ability of the drain pipe to absorb deformation, and the higher tensile stresses in the nozzle socket area induced by the blocked thermal expansion of the pipe because of the unreasonable pipe layout. After adding a U-shaped expansion bend to enhance the flexibility of the pipe and reduce the structural stress, the nozzle socket of the drain pipe did not crack during operation for about 1 a.
- nozzle socket,
- crack,
- drain pipe,
- thermal expansion,
- thermo-mechanical coupling

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Reasons for Cracking of Nozzle Socket of Hot Section Drain Pipe of a660 MW Ultra-supercritical Unit

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