Roots pump water ring pump unit is widely used in the vacuum system of chemical industry, food sublimation drying, high altitude simulation test and so on. This type of combined units has roughly the following types.
Roots water ring unit classification:
(1) the roots pump water ring pump: the function of the water ring pump in the unit is to cause the preparatory vacuum for the roots pump, so the maximum allowable exhaust pressure of the water ring pump is required, that is to say, on the one hand, the ultimate vacuum of the water ring pump should be improved as far as possible. On the other hand, the maximum allowable exhaust pressure of the roots pump should also be improved. In general, the ultimate vacuum degree of the single level water ring pump is not high, and the pre vacuum of the roots pump produced in our country is high, so in fact, the single level water ring pump is not used as the front stage pump of the roots pump, and the double stage water ring pump which can improve the limit vacuum is used as the front stage pump, and the double stage water ring pump is used, and the unit can also be improved. The limit vacuum degree. The ultimate vacuum degree of a Roots pump is low, especially when it is combined with water ring pump, the limit of use range is limited, the limit vacuum degree of the whole unit may be lower, but if two roots pumps are used in series and then combined with water ring pump, the ultimate true space of the unit can be greatly improved. So in this type, it is usually seen that two roots pumps are connected in series, and then a two-stage water ring pump is used as the former pump.
(2) roots pump water ring pump air pump unit: even if a double stage water ring pump is used, the increase of the limit vacuum is only within a certain range, because it is limited by the saturated steam pressure of the water. The theoretical limit pressure of the water ring pump is the saturated vapor pressure of the water. In fact, the limiting pressure of a water ring pump is significantly higher than the saturated vapor pressure at the water temperature, if factors such as gas reflux are taken into account. In order to improve the limit vacuum of the front pump, the water ring pump and the atmospheric pump can also be used together. In this way, the ultimate vacuum of the series primary air pump can reach 20-30 Torr, and if the water ring pump and the secondary air pump are combined, the ultimate vacuum can reach 2-10 Torr.
(3) the roots pump water ring pump parallel mechanical vacuum pump: this unit is mainly used to deal with a large amount of water vapor, and the extreme vacuum is required for a higher vacuum system, for example, in the vacuum drying. In the vacuum system requiring large amount of water vapor, the use of water ring pump is more suitable, but the limit vacuum degree of the whole unit is low because of its low limit vacuum. Although the mechanical vacuum pump with higher limit vacuum is needed as the front-stage pump in the vacuum system with higher vacuum requirement. However, the water ring pump has a lot of power consumption, low efficiency and high noise. In a long time vacuum drying system, the water ring pump is very uneconomical for the roots pump of roots pump.roots-water-ring-unit-classification
Under the above circumstances, the pneumatic mechanical vacuum pump and the water ring pump can be connected in parallel as the front pump of roots pump. In vacuum drying, the water ring pump is pre-pumped until the water vapor is greatly reduced, then the pneumatic mechanical vacuum pump is started to cut off the water ring pump. If it takes a long time to complete the drying process, the required cooling water and power will be less.
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