Effectively reduce the pump in the operation of cavitation damage method (2)
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1, into the pool
At the site of use, it is necessary and easy to view the flow of the influent into the pump where cavitation (including other failures) occurs. If the pool surface can see a strong vortex, should consider adding broken vortex.
In addition, the nozzle and the sink geometry should also be noted. Such as: nozzle from the pool wall is appropriate, whether there is a bubble into the pump suction tube.
Note that the pool water level is necessary to raise the water level into the pool can reduce or completely prevent cavitation.
Jietai pumping station on the water inlet transformation, erosion reduction of about 45%. Qilu Petrochemical Liu Kewang, Sun Jinghe and others in the import of circulating pump inlet vortex after the pump no longer occurs and the flow from the unstable 8500, 8000m3 / h, respectively, increased to a stable 9700,8200m3 / h.
2, water pipe
In addition to setting the import pipeline should try to make the pipeline loss is small (such as as few as possible elbow and valve), let the inlet pipe may not have higher than the pump inlet parts to prevent the tube of gas.
Chishui Natural Gas Fertilizer Plant in 1995 circulating pump imported rubber expansion to 1000mm, while the pipe is 800mm. To this end increased the exhaust pipe, to solve the pressure drop caused by the resistance to solve the cavitation problem.
3, adjust the pump flow
Wang Weidong, Xinjiang Electric Power Design Institute suggested that since the original formula used in China is derived from the former Soviet Union, the calculated value of its resistance is greater than the actual calculation of resistance should adopt a new formula. Otherwise, the pump is prone to cavitation at high flow rates (Northwest Power Technology 2000).
In the pump design selection and the actual deviation, the pump cavitation and economic operation can be solved by cutting the impeller, in order to achieve the purpose of eliminating cavitation and operating economy, this practice has proved to be effective.
4, the use of cited structure
The injection device corresponds in principle to a liquid-liquid jet pump. A high-pressure water is drawn at the pump outlet into the high-pressure water chamber as shown, and high-pressure water enters the suction pipe of the pump through the annular nozzle. The high-pressure water is mixed with the water in the suction pipe to exchange energy, and the energy of the mixed water after mixing is increased relative to the water energy of the original suction pipe so as to meet the required NPSH margin of the pump inlet.
Zhejiang University, Wu Yu, who introduced this (Zhejiang University master's degree thesis 2003), the paper describes the lead injection device back flow should be controlled between 2% -5%. Mr. Zhang Dehuang used a similar method in Changsha to test the multi-stage pump with 100 caliber and achieved remarkable results. The method is to use 1/2 tube to guide the water after the balance plate to the pump inlet, and the pump system's equipment NPSH is reduced by 0.5 ~ 0.8m.
Guo Dilong, Wuhan University, who introduced a jet - centrifugal pump device. This device is equivalent to the jet pump and centrifugal pump in series work on the suction pump is very effective, but generally not suitable for the pump in service transformation.
5, import qi
The method of supplementing gas does not prevent the cavitation of cavitation, but proper supplementing gas will reduce the damage to the side wall of the runner when the cavity is broken, and the added gas is like a layer of sponge to protect the side wall of the runner. This method is commonly used in water turbines and the like, but very little use is made of gas supplementing the pump due to the difficulty in grasping the gas supply.
Wuhan University of Water Conservancy and Electric Power Sun Shou, Yan Jinwen on the water vapor pump waterproofing research and achieved some results, but also pointed out: gas pump cavitation prevention and control, highly technical, only the gas flow, qi location and qi Way to negotiate, in order to achieve good results. Otherwise, the flow, lift and efficiency of the pump will drop a lot, causing adverse consequences. 
