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What are Rotary Pumps?

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  • Written By: Katharine Swan
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  • Last Modified Date: 20 August 2016
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Positive displacement rotary pumps are pumps that move fluid using the principles of rotation. The vacuum created by the rotation of the pump captures and draws in the liquid. Rotary pumps are very efficient because they naturally remove air from the lines, eliminating the need to bleed the air from the lines manually.

Positive displacement rotary pumps also have their weaknesses. Because of the nature of the pump, the clearance between the rotating pump and the outer edge must be very close, requiring that the pumps rotate at a slow, steady speed. If the pumps are operated at high speeds, the fluids will cause erosion, much as ocean waves polish stones or erode rock into sand. Pumps that experience such erosion eventually show signs of enlarged clearances, which allow liquid to slip through and detract from the efficiency of the pump.

Positive displacement rotary pumps can be grouped into three main types. Gear pumps are the simplest type, consisting of two gears laid out side-by-side with their teeth enmeshed. The gears turn away from each other, creating a current that traps fluid between the teeth on the gears and the outer casing, eventually releasing the fluid on the discharge side of the pump as the teeth mesh and go around again. Many small teeth maintain a constant flow of fluid, while fewer, larger teeth create a tendency for the pump to discharge fluids in short, pulsing gushes.

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Screw pumps are a more complicated type of rotary pumps, featuring two screws with opposing thread —- that is, one screw turns clockwise, and the other counterclockwise. The screws are each mounted on shafts that run parallel to each other; the shafts also have gears on them that mesh with each other in order to turn the shafts together and keep everything in place. The turning of the screws, and consequently the shafts to which they are mounted, draws the fluid through the pump. As with other forms of rotary pumps, the clearance between moving parts and the pump's casing is minimal.

Moving vane pumps are the third type of rotary pumps, consisting of a cylindrical rotor encased in a similarly shaped housing. As the rotor turns, the vanes trap fluid between the rotor and the casing, drawing the fluid through the pump.

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anon273661
Post 6

Rotary pumps are pumps whose shafts have these sort of vanes which entrap fluids and enable them to transfer to another reservoir by means of volume reduction. Although rotary pumps are not limited to vanes, they can also be gears and operate on the same principle. The delivery is sort of pulsating.

Centrifugal pumps are used for non-viscous fluids, and use impellers to deliver fluids from one place to another using velocity methods. The delivery of fluid is continuous.

Reciprocating pumps are piston type pumps which operate similarly to an internal combustion engine, except that the fluids don't really ignite at all.

Ivan83
Post 4

It sounds like rotary pumps have to be calibrated perfectly in order to work at all. I have never seen one, but imagining it in my mind it seems like you would have to have a perfect fitting between all the parts in order to create the vacuum necessary to pump the water.

harbifw
Post 3

What is the use of spary arrestors, are they provided around glands of all rotary cargo pumps? thanks in advance

anon4025
Post 2

what are the difference between rotary,centrifugal,reciprocating pumps.

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