16 comparisons among oil screw vacuum pump, liquid ring pump and rotary vane pump

screw vacuum pump

Oil-Sealed Screw Vacuum Pump

twin-screw screw vacuum pump

Liquid Ring Vacuum Pump

liquid ring pump

Rotary Vane Vacuum Pump

rotary vane pump

• Drive Mode

Variable-frequency drive (VFD)

Direct drive by power frequency or belt drive

Direct drive by power frequency

• Electric Motor

PM synchronous motor with inverter

Efficiency class: IE4 (super premium efficiency)

3-phase asynchronous motor

1-phase/3-phase asynchronous motor

• Sealing

Oil sealed

Water/liquid sealed

Oil sealed

• Lubricating

Full synthetic oil with replacement interval of 4000 – 8000 hours

Only grease for bearings / oil cup

Mostly mineral oil

• Cooling

Air cooled or water cooled. 

No secondary contamination thanks to no direct contact between cooling air/water and pumping gas.

Water cooled. 

A water system (even a chilled water system) is required.

Air cooled. 

The working condition in the room is affected by direct heat dissipation.

• Vacuum Filter at Inlet

5μ filter is integrated as default.

Extra installation required.

Extra installation required.

• Smart Control System

Built-in smart controller.

6” color touch screen and friendly interface.

Target values can be set.

Stable vacuum output.

Extra installation required.

Usually only for ON and OFF control.

Extra installation required.

Usually only for ON and OFF control.

• Starter Cabinet


Siemens contactor, star-delta buck start

Extra installation required.

Usually a star-delta starter cabinet at power frequency.

Extra installation required.

• Inverter

Installed as default inside.

Usually extra installation required, outside.

Extra installation required, outside.

• Vacuum Measuring

Built-in vacuum pressure and temperature inspection for logic control and protection.

Extra installation of vacuum gauge required.

Extra installation of vacuum gauge required.

• Efficiency

The efficiency is much higher than liquid ring and rotary vane pump.

It is not affected by ambient and water temperature.

Low efficiency.

To achieve its best efficiency, expensive chilled water shall be used as circulating water. The performance will drop sharply after the pump operates for just a few years.

The efficiency is lower  than screw pump.

The shaft power is usually much higher than nominated motor power on the nameplate.

• Exhausting

Oil mist is less than 3ppm, eco-friendly oil exhaust.

Exhaust with water mist. Small-sized liquid ring pump makes direct exhaust in the room.

Oil mist can be observed visually. High oil content easily pollutes the environment.

• Reliability

No change in radial load during twin-screw rotation.

SKF bearings to ensure reliability.

Designed service life of 100,000 hours.

Ball bearings used. Overhaul is needed after 3 – 5 years.

It’s required to replace the rotor in case of serious cavitation.

Overhaul is needed after 3 – 5 years.

• Reliability

Anti-vibration design and fully enclosed metal box to achieve lower noise.

No sound isolation design.

No sound isolation design.

• Footprint

The single machine is big. Considering the power and performance, it’s space saving.

The pump is quite big. Some pumps have a large footprint.

The pump is smaller. However, the total footprint could be not to achieve the same performance.

• Metal box

All auxiliary parts are included in the box.


Good protection.

Not available. Onsite installation required.

Not available.

Click to learn more about oil sealed screw vacuum pump and rotary vane vacuum pump.

Coolink, a TOP 3 Global HVAC Vacuum Pump Manufacturer & Quality Industrial Vacuum Pump Supplier from China

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