Safe to run dry, self-priming, and easy to maintain: Air operated diaphragm pumps offer many advantages for pumping fluids and can even handle aggressive or solid-laden media. How does an air diaphragm pump work? Pump properties and areas of application at a glance.
Air Operated Diaphragm Pumps
Technical Data & Characteristics:
- Delivery rate: 1 ml/h up to 54.48 m³/h (up to 240 gpm)
- Delivery head: up to 80 m (262.5 ft)
- Back pressure: from 0 up to 8.3 bar (depending on compressed air)
- Temperature: -12 °C to +107 °C (10.4 °F to +224.6 °F)
- Viscosity: 0.1 to 25,000 mPa·s
- Solids: up to 30 % (max. 12.7 mm)
- pH-value: 0 – 14
- Submersibility: immersed
- Depth: max. 8.8 m (29 ft)
- self-priming possible
- sealless design possible
- ATEX: suitable for ExZones 1 & 2
- Materials: PP, PVDF, aluminium, stainless steel
- hygienic design available
- Drive: compressed air
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An air operated diaphragm pump is a type of positive displacement pump that uses air pressure to pump liquids. Air diaphragm pumps consist of
- a housing, which has inlet and outlet openings, and
- two membranes, which alternately expand and contract in order to convey fluid through the pump.
The functional principle of an air diaphragm pump is based on an air supply system, which channels compressed air into the pump’s housing and causes a membrane to be pressed out of the housing. When the membrane expands, negative pressure is generated, which pulls the fluid through the inlet valve into the pump housing (suction stroke). As soon as the membrane contracts again, the pressure increases, and the fluid is pushed out of the pump housing through the outlet valve (pressure stroke).
Double-membrane pumps, sometimes called air operated double diaphragm pumps or AODDs, are a special type: They have two opposing pump chambers, whose membranes are connected to one another by a shaft. If the shaft moves to the left, there is a pressure stroke on the left chamber and a suction stroke on the right chamber. A movement to the right has the opposite effect on the chambers. Thanks to this design, double-membrane pumps generate a continuous flow rate. To reduce pulsation still more, double-membrane pumps and single-membrane pumps are frequently also equipped with a pulsation damper.
Air diaphragm pumps are made of aluminum or stainless steel. Individual manufacturers also offer variants in plastic, usually polypropylene (PP) or polyvinyl fluoride (PVDF). These materials are used if especially aggressive media such as acids, which would attack the metallic materials, have to be pumped.
An advantage of all air operated diaphragm pumps is that they are self-priming, and they are safe to run dry. The transporting units can therefore also be used for applications where a low suction height is required. In addition, the drive and fluid handled are completely separated from one another, which means that these pumps can handle a broad spectrum of fluids and materials, including abrasive, solid-laden, viscous, and corrosive media.
An air diaphragm pump can be controlled easily by adjusting the pressure of the air supply, which makes it ideal for applications where precise control of the volume flow is required. Since the pumps are safe to handle and there is no risk that sparks will be generated during operation, they can also be used in environments subject to explosion. Thanks to their robust construction, air diaphragm pumps are inexpensive to purchase and maintain, and they offer a long lifespan.
Air operated diaphragm pumps offer many advantages and only a few disadvantages, which are gradually disappearing thanks to manufacturers’ constant development work. These pumps’ somewhat lower energy efficiency as compared to other pump technologies has been optimized steadily, and the noise they make reduced significantly thanks to modern compressed air technology. Pulsations in the flow rate are reduced effectively by the double membrane’s design principle.
Depending on the principle, membrane pumps can be operated up to a maximum counter pressure of 8 bar.
Air diaphragm pumps are used in a wide variety of applications, for example in the chemical and food, pharmaceutical & cosmetics industries, wastewater treatment, and in shipping. In these industries, the transporting units are appreciated especially for their suitability for handling aggressive and abrasive media, as they are also in paint and lacquer manufacturing, power stations, and galvanizing shops.
System operators in the beverage industry and food production appreciate air diaphragm pumps for the complete separation of drive and fluid handled. This ensures especially hygienic handling, which rules out contamination of the fluid handled by the pump. Special hygienic models also optimize the pump technology for use with fluids for which there are special hygienic requirements – not just for foods and beverages, but also in the pharmaceutical and cosmetics sectors.
Large air diaphragm pumps manage fluid quantities of more than 900 liters per minute. The functional principle of the membrane pump is also used for dosing. Dosing pumps with membrane are self-priming and enable precise quantity output. Here too, the complete separation of the fluid handled and the drive offers advantages.
Special models such as multi-layer membrane pumps guarantee especially great operating safety when dosing: The multi-layer membrane ensures that even if a membrane tears, no medium can escape.
With their low costs, long lifespan, and easy operation and maintenance, air diaphragm pumps offer many advantages and can be used in a wide variety of applications – both in the raw environment of the chemical industry and in the hygiene sector or water treatment; they win people over with their gentle, reliable handling.
Do you need reliable pumps for your processes that can handle fluids safely and cost-effectively? We’ll be glad to check their suitability for your application.
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