Fault of high pressure regulating valve of the hot

2022-08-18
  • Detail

Fault treatment of high-pressure regulating valve of improved N300MW unit

Author: Xiao Qunfeng, Wu Xuebin Abstract: Aiming at the problem of 4 high-pressure regulating valve diffuser loosening in the operation of 2 steam turbine of Daba Power Generation Co., Ltd., this paper analyzes the causes of loosening, and deals with it through unit maintenance, and puts forward the treatment scheme of such problems to ensure the safe operation of the unit. 1 Introduction #2 steam turbine of Daba Power Generation Co., Ltd. is a domestic improved n.5/535/535 subcritical, intermediate reheat condensing, single shaft four cylinder four exhaust condensing steam turbine produced by Shanghai steam turbine Co., Ltd. There are two high-pressure main throttle valves, eight high-pressure regulating valves and four medium pressure combined throttle valves. The regulation mode is digital electro-hydraulic regulation system (deh-v). Under 300MW load, the 1, 2, 3, 4 high-pressure regulating valves are fully open

2 fault condition

at 8:00 a.m. on February 20, 2006, the maintenance personnel of Jinan assaying tensile testing machine, as an important instrument for material quality inspection, heard the abnormal sound in the #2 steam turbine #4 high pressure regulating valve. However, when the relevant professionals came to the site, the abnormal sound would affect the employment of about 320 employees if the factory did not stop. At about 13:55 p.m. on February 21, the maintenance personnel heard the abnormal sound in the interval of #2 steam turbine #4 high pressure regulating valve again during the equipment inspection, and then contacted the relevant professionals to arrive at the scene. After the confirmation of the personnel present, it was judged that the abnormal sound came from #4 high pressure regulating valve. Based on the defects of the contract type unit and the internal structure of the high pressure regulating valve, it was preliminarily judged that the abnormal sound was caused by the looseness of the high pressure regulating valve diffuser. After reporting to the leaders of the company, close the #4 high-pressure regulating valve to avoid the accident caused by breaking the diversion bell cover of the high-pressure regulating valve after the diffuser comes out

3 cause analysis

the high-pressure regulating valve diffuser of this type of unit is installed on the valve body with interference fit, which has a relatively broad market development prospect. In the initial design and installation instructions, the manufacturer requires the interference to be 0.06mm~0.09mm, and a f20mm horizontal pin is added between the diffuser and the valve body for reinforcement. However, in actual operation, due to the change of steam parameters, the diffuser and valve body are subject to an alternating thermal stress. The imported metering pump plus the force generated by the high-speed flow of steam in the diffuser make the diffuser loose in operation. This type of steam turbine unit was designed and produced by Shanghai steam turbine Co., Ltd. in the early stage. Limited by the technical conditions at that time and the operating experience of 300MW unit, due to the insufficient interference tightening force of the diffuser, the looseness of the high-pressure regulating valve diffuser is widespread, and it can not be handled at all during operation. After shutdown, due to the reduction of temperature, the diffuser is expanded and tightened after the valve body is cooled, making it difficult for the maintenance personnel to verify the looseness of the diffuser. Similar problems have also occurred in the high-pressure regulating valve of the same type #1 steam turbine of Daba Power Generation Co., Ltd

4 treatment 2 unit was shut down for maintenance as planned on July 9, 2006. On July 19, the #4 high-pressure regulating valve diffuser was taken out. After measurement, it was found that the matching part of the diffuser and the valve body was as shown in Figure 1, and the maximum clearance had reached 0.49mm. The measurement data are shown in Table 1. According to the latest information provided by the designers of the Design Institute of Shanghai turbine Co., Ltd., the interference fit between the diffuser and the valve body should be 0.12mm~0.15mm. As the #2 steam turbine of our company is an early product produced by Shanghai steam turbine Co., Ltd., the supply time of spare parts is long, and the newly ordered diffuser for this overhaul cannot be delivered. Therefore, the company decided to finish machining the existing diffuser after surface spraying according to the interference fit requirements, and finally meet the fit requirements. The specific treatment scheme is as follows: (1) drill the f20mm horizontal pin on the valve body to strengthen the diffuser, remove the diffuser, and reliably block the steam inlet of the high-pressure regulating valve; (2) After the diffuser is completely cooled, measure the fitting size of the diffuser and the valve body. Considering that the fitting part of the diffuser and the valve body may not be uniform and circular, in order to ensure the accuracy of the measurement data, select three points along the axial direction of the diffuser and the valve body, and measure them in the east-west and North-South directions respectively to determine that the current interface of the diffuser is a virtual image with size; (3) Spray the matching parts of the diffuser and the valve body, and pay attention to the measurement of the size after spraying. When the size of the diffuser after spraying is about 0.30mm larger than the size of the valve body, it will not be sprayed again; (4) Finish machining the diffuser according to the requirements of interference fit of 0.12mm~0.15mm until the interference meets the requirements; (5) Because the diffuser and the valve body are interference fit, the method of heating one part sleeve or freezing another part sleeve is generally used during the installation of interference fit. Because the volume of the high-pressure regulating valve body is large, the valve body cannot be heated, and the working space during installation is small, so it can only be worked by one person. Therefore, it is decided to install the diffuser into the valve body quickly after cooling. In order to ensure that the diffuser is installed in place at one time, measure the size of the diffuser immediately after using freon to cool it, so as to ensure the smooth installation. (6) Install the reprocessed f20mm fixed cross pin, and weld the cross pin on the valve body. 5 conclusion the governing system of n.5/535/535 steam turbine produced by Shanghai steam turbine Co., Ltd. in the early stage has many components and complex systems due to the technical conditions and experience in various aspects at that time. Whether the speed regulation system works normally or not is closely related to the normal work of all parts in the system. The abnormal work of any part will directly or indirectly affect the normal work of the speed regulation system. Therefore, its rationality and reliability should be fully considered in the design. In addition, it is also crucial to strengthen the inspection of production site equipment, improve the analysis and judgment ability of equipment abnormalities, and strictly implement the quality standards of maintenance process. References: [1] Zhou Liquan Overhaul of high-power steam turbine Beijing: China Electric Power Press, 1997 [2] Compiled by Shanxi Electric Power Industry Bureau Steam turbine equipment maintenance (junior worker, intermediate worker, senior worker) Beijing: China Electric Power Press, 1997 [3] Wu Jilan Steam turbine equipment and system Beijing: China Electric Power Press, 1998

Copyright © 2011 JIN SHI