What are Diaphragm Pumps, And What Are They Used for?

Diaphragm Pumps


The need to transport water from rivers and streams for use in the home and elsewhere posed a challenge for ancient civilisations. This simple but essential task often occupied early humans for a significant part of each day. Inevitably, they developed ways to make the job quicker and less laborious, using devices like the shadoof and the iconic Archimedes screw. These ancient machines were the distant precursors of the many different devices used to transport water and other liquids today, including sophisticated diaphragm pumps.

Today, although pumping equipment is available in hundreds of different designs, most depend on one of two mechanical principles for their operation. These are centrifugal force and positive displacement. The former type employs the effect of a rapidly rotating component similar to a ship’s propeller. However, while the latter pushes water away from the boat, the modified design causes water to be drawn into the device, thus acting, instead, as an impeller. Some centrifugal units employ two or more impellers to provide increased suction power. By contrast, there are several ways to generate positive displacement, and diaphragm pumps are just one example of how this principle has been applied to transport liquids.


How do Diaphragm Pumps work?

As their name implies, these devices depend upon the displacement of a flexible diaphragm to draw in and expel their contents. Two methods are commonly employed to create the necessary movements. The first of these involves the reciprocating action of a motor-driven piston. As the piston withdraws, it creates a vacuum, which, in turn, pulls the flexible material inwards. That inward movement produces suction on the other side of the diaphragm, opening the inlet valve, closing the exit valve and causing the diaphragm pump chamber to fill with liquid. The return stroke creates pressure in the chamber, closing the inlet valve and expelling the pressurised fluid through the now open exit valve.

These piston-operated units have numerous applications. They are well-suited for transporting aggressive and toxic loads, and especially for handling abrasive slurries that contain a higher percentage of solids. Chemical plants, mines, pharmaceutical companies, food and drink producers and the oil and gas industry all employ these devices extensively in their operations. Because their action produces equal, discreet volumes of fluid, piston-operated diaphragm pumps can also offer the user a precision dosing solution.

An alternative design employs a pair of pump chambers, each sealed by a separate diaphragm. It is frequently powered by compressed air rather than an electric motor. There is one significant advantage of employing his type of unit. In contrast to the pulsed output of the piston-driven type, its effect is to create a continuous stream of liquid. The action of valves that regulate the movement of the compressed air on others that control the flow of fluid is responsible for the smooth operation of these double-diaphragm pumps. Let’s examine how that works.

Air entering the device causes a centrally-located distribution device to deliver it to one of the chambers while opening a valve that allows air to vent from the second chamber. The two diaphragms are joined by a connecting rod. Consequently, as the air compresses one of these, the rod pulls on the other, causing it to expand. The expanded chamber draws liquid in while the compressed chamber expels its contents. Each action opens or closes the appropriate inlet and outlet valves as necessary.


The Benefits of Acquiring Diaphragm Pumps

One of the main benefits of diaphragm pumps is that their contents only have direct contact with a few components. When using suitably robust materials to produce those more vulnerable parts, these devices offer an ideal option for handling the aggressive fluids used routinely across a broad range of industries. Stainless steel, superalloys of iron, such as Hastelloy, polyethylene and other plastics are commonly used in their manufacture.

In addition to handling corrosive chemicals and volatile solvents, the manufacturers can configure these devices to overcome many common industrial challenges. These include pumping viscous oils, creams, smaller solids, gels and abrasive slurries, confirming the exceptional versatility of the diaphragm pump.

In light of the diversity of these devices, choosing the best one for a given task can be critical. It is, therefore, advisable to seek professional advice rather than risk a costly mistake. For reliable guidance, and superior products, most South Africans turn to Prochem. The company is a leading manufacturer and supplier of pumping equipment and related accessories, including a selection of versatile world-class diaphragm pumps.

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