Liquid ring vacuum pump is an ideal equipment for suction of wet mixed gas and micro droplet gas. The pump has standard material configuration, all cast iron material or 316SS stainless steel material configuration. Liquid ring vacuum pump is usually water-cooled system, air-cooled system for selection.
The whole engineering system solution includes instrument, control device, pipeline and valve, working fluid recycling system and working fluid recycling system.
The suction pressure of liquid ring vacuum pump can be as low as 4 Torr (5.3 mbar a). However, the working performance under low pressure is limited by the saturation and vapor pressure of the working fluid, which can be water, oil or process fluid.
With the rapid development of science and technology, the oil seal vacuum pump has been incompetent in many application fields and replaced by the dry vacuum pump. But in the common industrial fields, such as food processing, electrical manufacturing, chemical medicine and other industries, liquid ring vacuum pump is still the most suitable product because of its low cost, convenient use and low maintenance cost.
However, when liquid ring vacuum pump is used to remove water vapor, some problems often arise. If the lubricating oil of vacuum pump is emulsified and deteriorated, it can not reach the required working pressure. Even the vacuum pump body and rotor are seriously rusted, and the whole machine is scrapped. The main reason for this situation is that I don’t know the principle of liquid ring vacuum pump to pump out (water) steam very well and neglect the maintenance of vacuum pump.
In this paper, the principle and method of water vapor extraction by liquid ring vacuum pump are discussed. According to the practical experience, some correct methods in the use and maintenance of vacuum pump are put forward.
Liquid ring vacuum pump is widely used in vacuum packaging, degassing, drying, impregnation and other equipment. If the pumped gas is air, the oil seal vacuum pump equipped with exhaust filter and intake check valve is very suitable. However, the extracted gas contains steam. When condensable gas is available, the use environment of vacuum pump becomes quite bad. Some people mistakenly think that the vacuum pump is an air pump. As long as it is sucked in, it can be discharged. In fact, this is not the case.
If the steam cannot be effectively removed to discharge the steam from the pump cavity, the steam will condense in the pump cavity. This will lead to the emulsification and deterioration of the lubricating oil of vacuum pump, which will seriously affect the limit pressure that the vacuum pump can reach, reduce the lubricating performance, increase the wear, and fail to work normally, and even cause serious corrosion of the pump body and rotor and other parts, resulting in the scrapping of the whole machine.
Only a vacuum pump with an air ballast valve can pump pure steam. The capacity of vacuum pump to remove steam can be expressed by the maximum allowable pressure of water steam. The ability of steam extraction can be effectively improved by increasing the gas ballast, increasing the working temperature and reducing the exhaust pressure.
Installing condenser on vacuum pipeline is a very effective way to solve the problem of water vapor. In practice, a large part of the problems are caused by improper maintenance. According to the amount of steam to be pumped, choose a reasonable vacuum pump, coupled with the correct maintenance, the problem of water vapor will be solved.
1. Gas ballast device
If the pressure of a liquid at a certain temperature is lower than its saturated vapor pressure, it will evaporate and become a vapor, which is a condensable gas. However, when the pressure is greater than the saturated steam pressure, the steam will condense into liquid.
The operating temperature of liquid ring vacuum pump is generally 70-800c, and the saturated pressure of water vapor is about 400hpa. When the extracted gas is completely water vapor, when the water vapor is compressed to 400 hPa, the exhaust pressure is far from 1333 HPA, and the water vapor begins to condense into liquid. The water vapor can not be discharged by the vacuum pump, and all condenses in the vacuum pump. Therefore, the ordinary vacuum pump without any device can not discharge pure steam from the pump cavity. However, as long as the partial pressure of water vapor in the compression process is less than its saturation pressure, the steam can be discharged from the pump cavity.
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