Piston and diaphragm pumps operate under different principles and are each well-suited for different applications. It is important to understand the task a pump should perform to pick the appropriate pump for the job.

Operation

Piston pumps use multiple pistons rotating around an axis to create fluid flow. Each piston pushes fluid through the pump's output port as it extends. The piston draws in more fluid as it rotates and retracts and continuously repeats the cycle. Diaphragm pumps activate a flexible diaphragm that draws in fluid as the diaphragm raises and expels it when the diaphragm lowers.

Applications

Piston pumps are useful in moderate to high pressure applications. They are employed in circulatory hydraulic systems, where the same hydraulic fluid is continually reused. Diaphragm pumps work well in shallow water applications and usually pump fluid in and out of the pump, but do not circulate and reuse the fluid.

Considerations

Though piston pumps can provide high pressure, they must be used in complete liquid applications. Any solids or debris in the hydraulic fluid can damage the pump. Diaphragm pumps cannot produce the same amount of pressure or fluid flow as piston pumps, but they can efficiently pump liquids containing 25 percent or more solids.