What is a Piston Pump?

shutterstock_162625754WEBWhat is a Piston Pump?

A piston pump is a type of reciprocating pump that moves and pressurizes fluid by using one or more reciprocating pistons. Three main components can always be found in every piston pump; a piston, a crank, and inlet and outlet valves. The piston is the main source for allowing the liquid to flow in and out through the valves. Attached to the motor, the crank will move in a rotational fashion allowing the repetitive back and forth movement of the piston. Finally, each piston pump will have an inlet and outlet valve. These two valves allow for the liquid or gas to enter and exit the cylinder.
Drawing its powers from an electric motor, internal combustion engine, or less advanced options like hand, wind, or flowing water, pistons will first move in an upward fashion that allows the liquid or gas to be drawn in from its inlet valve. Once the cylinder is filled, a downward motion by the piston will occur. This downward motion will increase the pressure on the outlet valve, which in turn opens and allows the liquid or gas to exit the cylinder at a high-pressure rate. Once the maximum extension of the piston is reached a repetitive back and forth motion will occur due to the rotational movement of the crank.

shutterstock_1113704876WEBThe two basic types of piston pumps are a lift pump and a force pump. A lift pump operates with the upstroke of the piston drawing water into the lower part of the cylinder from the inlet valve. On the downstroke, water passes through valves set in the piston into the upper part of the cylinder. Then a second upstroke occurs allowing the medium in the cylinder to discharge from the upper part of the cylinder via a spout.

With one slight difference, a force pump operates in a similar fashion as a lift pump. Once again through the inlet valve, the upstroke of the piston draws water into the cylinder. Then, only needing another downstroke, the water is discharged through the outlet valve into the outlet pipe. The difference between the lift and force pump is that the lift pump needs a final upstroke to force the medium out of the pump. A force pump only needs one upstroke to allow the water in and one downstroke to force the medium out. As the name implies, the lift pump is lifting the medium out with a second upstroke, while the force pump is forcing the medium out through a downstroke.

More advanced options are available when it comes to piston pumps. The two most common are axial piston pumps and radial piston pumps. The axial piston pump is a positive displacement pump and one of the most versatile piston pumps available. It can be arranged as a pump or a motor, depending upon the application. Coupled with a choice of control mechanisms, the axial piston pump can be applied to a variety of tasks. The basic design provides an efficient delivery of power, which has led to an increasing number being specified in favor of fixed displacement gear or vane pumps.

Unlike common piston pumps, pumps such as a lift or force pump that can be operated by one piston. The axial piston pump has multiple pistons in a circular array within a cylinder block. This circular array of pistons rotates against an angled or fixed swash plate. As the rotary group turns, the pistons are pushed forwards and backwards. A grooved timing plate at the top of the pistons controls the way the fluid is drawn through the suction side of the pump and out through the pressure side.

shutterstock_1486872638WEBLike the axial piston pump, the radial piston pump operates with multiple pistons. However, it differs from all the others by its pistons being arranged radially around the drive shaft. As the shaft rotates, the connecting rods push the pistons back and forth in the cylinders to develop the pumping action. After a rotation angle of 180 degrees, the work is completed, and the workspace of the piston is filled with the moved medium which can now be discharged out of the outlet valves.

A radial piston pump can be used with various hydraulic fluids such as mineral oil, biodegradable oil, oil in water, water-glycol, synthetic ester or cutting emulsion. A radial piston pump is commonly used for the following applications; machine tools, high pressure units, test rigs, automotive transmissions, plastic and powder injection molding, and wind energy.

There are many more forms of piston pumps. Regardless of the type, all have one common goal in mind; to move and pressurize fluids. With this ability to move and pressurize fluids, piston pumps can power heavy machinery. The heavy machines they are powering can be found in industries like oil production or food processing. For smaller simpler versions of piston pumps, they can power things such as a power washer or paint sprayer.


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