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| DOI：10.13522/j.cnki.ggps.2023582 |
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| Research on the water hammer protection system of the combination of axial flow check valve and water hammer relief valve |
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LIU Can, WANG Yongning, FAN Zheng, LIU Wei
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1. Gansu Water Resources and Hydropower Survey and Design Research Institute Co., Ltd, Lanzhou 730000, China;
2. Qingyang Yanhuanding Yanghuang Continuation Project Construction Management Bureau, Qingyang 745000, China
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| Abstract: |
| 【Objective】 To reduce the adverse effects of water hammer on the buildings in long-distance high-lift water conveyance projects, and to ensure the safety of pipelines buildings. 【Method】 Based on the transient flow theory and the characteristic line method combined with the mathematical model of water column separation, and considering the boundary conditions of water hammer protection equipment, the hydraulic simulation software was used to calculate the water hammer hydraulic. The traditional “one-way surge tank + air valve” and “water hammer relief valve + axial flow check valve + air valve” two water hammer protection measures were numerically calculated and compared to verify the protection effect of the water hammer protection system combined with the axial flow check valve and the water hammer relief valve. 【Result】 After calculation and verification of many years of operation in the later actual project, it was shown that in the long-distance high-lift water conveyance project, the two water hammer protection schemes have certain protective effects on the high-pressure and negative-pressure water hammer of the pipeline under the accident pump shutdown. The protective measures of “one-way surge tank + air valve” can reduce the negative pressure in the pipeline from the vaporized negative pressure -8.4 m to the head pressure of -6.9 m, and the maximum positive pressure of the pipeline is reduced from 4.25 Mpa to 2.98 Mpa. However, if we want to continue to reduce the negative pressure of the pipeline, we need to increase the number of surge tanks and increase the project investment, and there is no economic advantage. The water hammer protection measures of “water hammer relief valve + axial flow check valve + air valve” can effectively protect the high and low pressure water hammer and pump backflow caused by pump stoppage. The negative pressure in the pipeline is reduced from the vaporized negative pressure to the -5 m head pressure, so that the maximum pressure in the system is reduced from 4.25 Mpa to 3.0 Mpa, and the maximum pressure in the pipeline is controlled within 1.2 times of the steady-state pressure. 【Conclusion】 Years of operation after the completion of the project has verified that the water hammer protection system only needs to set up a water hammer relief valve and an axial flow check valve in the water conveyance system to achieve effective protection against high and low pressure water hammer caused by pump shutdown and pump backflow and other issues. It has the same reliability and higher economy, and can provide a basis for the design of water hammer in similar projects. |
| Key words: long-distance high-lift water conveyance project; water hammer hydraulic simulation calculation; axial flow check valve |
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