The vacuum pump sealing water is taken from the closed-type water replenishment. In summer, the closed-type water temperature can reach up to 35°C. Therefore, in actual operation, the vacuum pump sealing water is difficult to guarantee a supercooling of 4.2°C. As the sealing water temperature approaches saturation, its pumping capacity continues to decrease until it is saturated and vaporized and loses its working ability.

The working pressure of the vacuum pump and the pressure of the condenser are a dynamic balance process. Regardless of the temperature of the circulating water, the suction pressure of the vacuum pump must be lower than the pressure of the condenser in order to pump out the non-condensable gas in the condenser. Therefore, the sealing water temperature of the vacuum pump must be lower than the saturation temperature corresponding to the exhaust steam pressure.

On July 17, 2009, a company's No. 3 unit experienced a vacuum drop. It was because the water in the gas-water separator was not changed in time, which caused the sealing water in the vacuum pump to vaporize. The test was conducted on the #2 machine A vacuum pump on July 30. The temperature of the separator was 16.2°C after adding 16°C cold water to the pump A. After starting the pump A, the temperature rose sharply to 24.5°C. As the temperature rises, the vacuum drops. When the water temperature is 30°C, the vacuum increases by about 1kPa, and the vacuum pump current increases by about 0.85A. When the working water temperature drops by 1℃, the vacuum increases by about 0.19kPa. It can be seen from this test that in summer working conditions, ensuring a lower temperature of the vacuum pump sealing water is an important means to ensure the vacuum of the vacuum unit.

Based on the above analysis, there are two ways to solve the cavitation problem of the vacuum pump: one is to reduce the water temperature, and the other is to reduce the vacuum of the condenser. According to the actual situation of the company, the cooling water or working fluid of the working fluid of the vacuum pump is modified, so as to not only improve the vacuum, but also solve the cavitation problem of the vacuum pump.