Saturday, January 4, 2020

Difference between screw pump and gear pump

Screw pump.   

Screw pumps have a better suction capability and therefore work much better in a long pipeline, for more viscous oils and when air is present in the fluid.
A gear pump's suction capacity is usually less than an equivalent screw pump, making it less efficient under difficult suction.

The screw elements inside the pump have a smaller diameter than gears (for the same capacity), producing less turbulence in the fluid for smoother pumping.
Gears need a large diameter for the requested capacity and therefore produce more pulsations in the fluid discharge.
Screw pumps are able to work at a higher motor speed (3000-3500 RPM).

Due to the larger gears, rotation speed is limited. If you increase the RPM, the pump loses suction.

The screw pump design has better mechanical efficiency as it uses less power for the same capacity relative to a gear pump, thus saving energy costs. 
The motor in gear pumps use higher power for the same capacity as a screw pump, resulting in increased energy costs and a larger motor required. 
The operation of a screw pump is much softer with less pulsations, less noise and fewer vibrations, meaning longer lifespan.
Gear pumps are noisier, more turbulent and cause more vibrations for the pump and pipework to withstand causing a lower working life. 

Screw pumps typically have a smaller footprint, making them better when space is an issue.

As they generally have a larger footprint, they aren't as good for installations where room is limited.
Internal components such as the screws generally need to be replaced at the same time to ensure efficient operation, making them quite expensive to maintain.
Internal components are often cheaper than those in a screw pump, however as bushes and bearings are in the pumped liquid they are more subject to wear.

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