Difference between screw vacuum pump and liquid ring vacuum pump

Screw vacuum pump is a kind of vacuum equipment which uses screw to produce power. The liquid ring vacuum pump is a kind of crude vacuum pump used to transport liquid. But for novices, they are often confused. What’s the difference between screw vacuum pump and liquid ring vacuum pump?

I. working principle:

1. Screw vacuum pump: the screw vacuum pump uses the left screw and the right screw which are meshed and do not contact with each other in the synchronous reverse rotation of the gear drive to make high-speed rotation. The screw grooves are divided into multiple spaces and formed into multiple stages by using the pump shell and the meshing screw. The gas is transmitted in the same grooves (cylindrical equal pitch), but there is no compression, only the screw structure at the end of the screw It can compress gas. A pressure gradient can be formed between different stages of the screw to disperse the pressure difference and increase the compression ratio. The performance of the pump is greatly influenced by the clearance and the speed of the pump.

2. Liquid ring vacuum pump: the rotor with multiple blades is installed in the pump shell eccentrically. When the impeller rotates, the liquid is thrown to the pump shell and forms a liquid ring concentric with the pump. The liquid ring forms a rotary variable volume vacuum pump with periodic volume change with the rotor and blades.

II. Vacuum degree:

1. The vacuum degree of screw pump can reach – 750mmhg, and the vacuum degree is relatively stable; the vacuum oil is generally air-cooled.

2. The vacuum degree of liquid ring vacuum pump can reach – 725mmhg. Due to the influence of the partial pressure of water vapor, the vacuum degree and suction capacity will change with the water temperature and air temperature. High working liquid temperature, high suction temperature, low vacuum degree, working liquid temperature

Degree, suction temperature high and low vacuum degree is high. Therefore, the system must provide chilled water and reduce the suction temperature of the pump.

screw vacuum pump

Unit configuration

III. unit configuration

1. The screw pump supplier provides the customer with a standard complete set of units, which can be used immediately after being transported to the customer’s site. The standard electric control box is the feature of screw pump. All kinds of operating conditions of vacuum unit can be displayed on the electric control box.

2. Liquid ring pump can be provided with single pump or complete set of units, and customers can choose freely. If the unit configuration is wrong, it may cause the working fluid of vacuum pump to return to the system. If there is no water protection when the single pump is running, the single vacuum pump will be damaged when the water is cut off.

IV. operation cost

1. The screw vacuum pump, like the screw air compressor, needs to be maintained in a fixed period (about 8000 hours of operation). The vacuum oil, oil filter, air inlet filter and exhaust filter shall be replaced. Under normal conditions, the operating efficiency of screw pump is 10-20 higher than that of liquid ring pump.

2. There is basically no need to replace any accessories for the liquid ring pump within 2-3 years.

V. operation conditions

1. Screw vacuum pump is not suitable for pumping gas with chemical reaction with pump oil and containing a lot of particle dust and water vapor.

2. Liquid ring vacuum pump allows the pumped gas to contain a large amount of water vapor and a small amount of solid particles, which is an unparalleled advantage of other types of vacuum pump Since the gas compression process is isothermal compression, the pump is suitable for pumping and pumping flammable, explosive and toxic gases.

6. Investment cost: the price of screw vacuum pump is about 30 higher than that of liquid ring pump.

7. Floor area: the floor area of liquid ring vacuum pump is 15 larger than that of screw pump.

The above is the difference between screw vacuum pump and liquid ring vacuum pump. You can select the appropriate vacuum pump equipment according to your own industry requirements.

liquid ring vacuum pump

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