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A Brief Overview Of Hydraulic Pumps

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Hydraulic pumps are used in situations where it’s necessary to move fluids. These devices are not limited to water. All sorts of liquids are moved in this way. Gasoline and oil, milk at the dairy, and even blood during dialysis are all pumped fluids.

Three are several different types of hydraulic pumps available on the market, and the type to use depends largely on budget and application. They generally fall into three main categories: gear pumps, vane pumps, and piston pumps.

A gear pump uses one or more rotating gears, where the spaces between the teeth act as chambers that trap fluid and force it from the intake to the output of the pump.  External gear pumps use gears with teeth that terminate along the wall of the pump, trapping fluid in the chambers created between the teeth.  An internal gear pump uses a hollow outer gear with teeth on the interior surface. An internal gear moves the outer gear, pushing fluid as the combination turns.


Another variation of the gear pump is a design based on worm screws. These are sometimes called screw pumps and are based on the concept of the Archimedes’ screw. A rod is threaded much like a typical screw fastener. When the screw turns, it drives any fluid along the axis of the screw until it emerged from the other end. These are quiet pumps, but not very efficient.

A vane pump consists of a rotor and vanes, which trap fluid between them. This type of pump will run quieter than a gear pump and give a more consistent flow instead of the pulsed flow typical with a gear pump.

Finally, piston pumps use moving pistons to draw fluid through the intake and into a chamber, and then through an output. The action is controlled by a swashplate, which moves the pistons. The inline axial pump is a very common and adaptable pump good for many purposes and is completely reversible. Another type called a radial piston pump, is a good solution for high-pressure low volume situations.  An off-center rotating cam is used to move an array of pistons located in a circle around a chamber that acts as a reservoir.  This type of pump is also reversible.

One other type of pump is the Peristaltic pump, which uses a cam with rollers to compress tubing along its circumference. As the cam moves, rollers push fluid along the tubing. This type of pump is often used when pumping blood.