A diaphragm pump, part of the positive displacement pump family, is a versatile and reliable pump that can be used across most industries where fluid transfer is required.  It uses a combination of the reciprocating action of a set of diaphragms and valves on either side of the body to pump fluid.

A diaphragm pump can either be mechanically driven with an electric motor or engine, or airoperated with compressed air. They can come in a range of materials including aluminum, cast iron, Hastelloy-C, Alloy 20, stainless steel, PVDF, polypropylene, and conductive polypropylene acetal, therefore ensuring that they can be made to suit a range of applications.

One key feature in the operation of a diaphragm pump is pulsation, that being, the alternation of suction and discharge resulting in liquid flowing intermittently through the pump. An injection syringe is a very basic form of diaphragm pump and is useful in illustrating this concept of pulsation in action.

Pulling the piston of the syringe back creates suction that pulls the liquid into the cylinder while pushing the piston forward discharges the liquid through the needle of the syringe (Figure 1).

Figure 1: Injection syringe.

In the same way, a diaphragm in a pump moves inward and outward toward the body, working in combination with the check valves to draw in and discharge the fluid out of the pump. Figure 2 below shows that without the check valve in place, air would simply flow into the cylinder when the piston is moved outward thereby preventing any suction.

Figure 2: Diaphragm with no check valve in place.

Figure 3 shows the check valve in place which serves to prevent fluid flowing into the cylinder. This creates a negative pressure within the cylinder and allows fluid to be drawn up from the bottom once the piston is moved outward.

Figure 3: Diaphragm with check valve in place.

Figure 4 shows the cylinder dispelling the liquid when the piston is pushed inward.

Figure 4: Diaphragm discharging fluid.

Figures 5 and 6 further help to illustrate the operation of a diaphragm pump that uses two check valves, one on the suction side and the other at the discharge side. These valves alternate between open and closed, working with the diaphragm to achieve suction and discharge.

Figure 5: Diaphragm pump suction.

Figure 6: Diaphragm pump discharging.












One of the many elements to consider when selecting a pump is the type and viscosity of the liquid being pumped. In general, a diaphragm pump is well-suited for use with a wide range of fluids, including high and low viscosity liquid, high and low dense liquids as well as clean and abrasive liquids.

This includes liquids such as volatile solvents, corrosive chemicals, viscous, shearsensitive foodstuffs, pharma products, sticky fluids, pharma products, dirty water, smaller solids, abrasive slurry, creams, oils, and gels.

While it is true that diaphragm pumps provide a versatile and reliable option when pumping highly viscous or dense fluids, ensuring you have the right pump for the right application involves a more thorough set of considerations. If in doubt, consult your pump supplier.

Article courtesy of Kelair Pumps Australia “When Pump Knowledge Matters” Phone 1300 789 466, or visit

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1 Comment

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  1. Nirmala Pumps 12 months ago

    This is very useful information. Diaphragm pumps are used in almost every industry that requires fluid transfer because they are so versatile. They are frequently used for dewatering or water removal in a variety of industries.

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