Working Principle
Roots Water Ring Vacuum Unit It is more advantageous to use a water ring pump as a front pump than other vacuum pumps. It overcomes the disadvantages of the ultimate pressure difference when a single water ring pump is used (the ultimate pressure of the unit is much higher than that of the water ring pump) and the low pumping rate under a certain pressure, while retaining the advantages of the Roots pump that it can work quickly and has a large pumping rate. It is especially suitable for pumping out a large amount of condensable steam, especially when the gas ballast oil seal mechanical vacuum pump is not capable of removing condensable steam, or the solvent used can deteriorate the pump oil and affect the performance, or the vacuum system does not allow oil pollution. When equipped with explosion-proof motors and electrical appliances and complying with the corresponding safety regulations, flammable and explosive gases can also be pumped out. Therefore, Roots pump-water ring pump units are widely used in vacuum distillation, vacuum evaporation, dehydration crystallization in the chemical industry; freeze drying in the food industry; vacuum drying in the pharmaceutical industry; polyester chips in the textile industry; high-altitude simulation tests, etc. vacuum systems.

▲ Water Ring Vacuum Pump
In general, it is more advantageous to use a water ring pump as a fore-stage pump for Roots vacuum units than other vacuum pumps. This is mainly because it can remove a large amount of condensable steam, especially when the gas-ballast oil-sealed mechanical vacuum pump is not capable of removing condensable steam, or the solvent used can deteriorate the pump oil and affect performance, or when the vacuum system does not allow oil pollution.
System Type
Roots pump-water ring pump units are widely used in vacuum systems such as chemical industry, food sublimation drying, and high-altitude simulation tests. There are roughly the following types of such combined units
- Roots pump-water ring pump
The role of the water ring pump in the unit is to create the preparatory vacuum required by the Roots pump, so the maximum allowable exhaust pressure of the water ring pump is required, that is, on the one hand, the ultimate vacuum of the water ring pump should be increased as much as possible, and on the other hand, the maximum allowable exhaust pressure of the Roots pump should be increased.
Generally, the ultimate vacuum of a single-stage water ring pump is not high, and the pre-vacuum required by the Roots pump produced in my country is relatively high. Therefore, in fact, a single-stage water ring pump is not used as the front pump of the Roots pump, but a two-stage water ring pump that can improve the ultimate vacuum is used as the front pump. The use of a two-stage water ring pump can also improve the ultimate vacuum of the unit.
The ultimate vacuum of a Roots pump is low, especially when it is combined with a water ring pump, the scope of use is limited, and the ultimate vacuum of the entire unit may be lower, but if two Roots pumps are connected in series and then combined with a water ring pump, the ultimate vacuum of the unit can be greatly improved.
Therefore, 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 a front pump to form a unit. - Roots pump-water ring pump-atmospheric pump system
Even if a two-stage water ring pump is used, the improvement of the ultimate vacuum is only within a certain range, because it is limited by the saturated vapor pressure of water. The theoretical ultimate pressure of a water ring pump is the saturated vapor pressure of water. If the influence of factors such as gas reflux is considered, the ultimate pressure of the water ring pump is actually significantly higher than the saturated steam pressure at the water temperature. In order to increase the ultimate vacuum of the fore-stage pump, the water ring pump can also be used in combination with an atmospheric pump.
In this way, the ultimate vacuum after the first-stage atmospheric pump is connected in series can reach 20~30Torr. If the water ring pump is combined with a second-stage atmospheric pump, the ultimate vacuum can reach 2~10Torr. - Roots pump-water ring pump parallel mechanical vacuum pump
This unit is mainly used for vacuum systems that need to handle a large amount of water vapor and have high ultimate vacuum requirements, such as in vacuum drying.
In vacuum systems that require the handling of a large amount of water vapor, it is more appropriate to use a water ring pump, but because its ultimate vacuum is not high, the ultimate vacuum of the entire unit is low. Although in vacuum systems that require a higher vacuum, a mechanical vacuum pump with a higher ultimate vacuum is required as a fore-stage pump. However, due to the high power consumption, low efficiency and high noise of the water ring pump, it is not economical to use a water ring pump as a fore-stage pump for a Roots pump in a vacuum drying system that requires a long time.
In the above case, the gas ballast mechanical vacuum pump and the water ring pump can be connected in parallel as the front pump of the Roots pump. When vacuum drying, the water ring pump is used for pre-pumping until the water vapor is greatly reduced, and then the gas ballast mechanical vacuum pump is started and the water ring pump is cut off. If it takes a long time to complete the drying, the required cooling water and power are less.
Model | Max.Pressure | Max. Air Volume | Power | Speed | Water Consumption | Noise |
Mbar(Pa) | M3/min | KW | Rpm | L/min | dB(A) | |
2060 | 33(3300) | 0.45 | 0.87 | 2880 | ~2 | 62 |
2061 | 33(3300) | 0.87 | 1.45 | 2880 | ~2 | 65 |
2070 | 33(3300) | 1.33 | 2.35 | 2880 | ~2.5 | 66 |
2071 | 33(3300) | 1.83 | 3.85 | 2880 | ~4.2 | 72 |
5110 | 33(3300) | 2.75 | 4 | 1450 | ~7 | 63 |
5111 | 33(3300) | 3.83 | 5.5 | 1450 | ~8.5 | 68 |
5121 | 33(3300) | 4.68 | 7.5 | 1450 | ~10 | 69 |
5131 | 33(3300) | 6.68 | 11 | 1450 | ~15 | 73 |
5161 | 33(3300) | 8.3 | 15 | 970 | ~20 | 74 |
6110 | 33(3300) | 2.75 | 4 | 1450 | ~7 | 63 |
6111 | 33(3300) | 3.83 | 5.5 | 1450 | ~8.5 | 68 |
6121 | 33(3300) | 4.68 | 7.5 | 1450 | ~10 | 69 |
6131 | 33(3300) | 6.68 | 11 | 1450 | ~15 | 73 |
6161 | 33(3300) | 8.3 | 15 | 970 | ~20 | 74 |
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