Air operated diaphragm pumps, or AODD pumps as they are commonly abbreviated to, are a type of reciprocating positive displacement pump that are driven by compressed air rather than an electric motor. This design of pump is made up of two chambers, each with their own inlet check valve, outlet check valve and diaphragm; hence why they are also referred to as double diaphragm pumps.
The back and forth movements of the diaphragm shifts the air supply shifts from one chamber to the other which enables the two chambers to operate simultaneously. As the diaphragm moves in to the one chamber it forces the fluid inside into the outlet, whilst the other chamber fills up with fluid drawn from the inlet. As the diaphragm moves back into the opposite chamber, the fluid now in that chamber is forced out and the other chamber begins to fill up.
Safe and clean operation – With no motors, packing or seals, the AODD pump is less prone to leaking fluid than typical centrifugal pumps. This makes it a good solution when handling volatile, corrosive or dangerous liquids that may cause harm if leaked, as well as just generally being a cleaner, lower maintenance option.
Good dry running capabilities – Unlike other pump types, air operated diaphragm pumps are able to run dry or against a closed discharge without causing immediate damage to the pump. Excessive back pressure caused by a dead head stops further operation until the discharge opens. This also makes them suited for a wide range of applications within factories as they are often “fit and forgot” being low maintenance, as they are unlikely to be damaged through process stops.
Self priming – Air diaphragm pumps are self-priming and therefore have good suction capabilities (up to 8m when wetted) without need for a manual priming device. They are consequently often select for applications where the suction conditions are difficult for example the emptying of tanks and containers.
Flexible performance – AODD pumps are versatile in their performance, as to meet exact flow rate or pressure requirements of a particular installation you can simply adjust the air inlet pressure. In addition, thanks to the vast range of materials that they can be produced in, air operated diaphragm pumps are compatible with a wide variety of fluids ranging in viscosity from fuels to chemicals to food stuffs. To pump more viscous fluids the pump can simply be reduced in speed to cope with thicker fluids.
Air operated diaphragm pumps are a versatile design suitable for the pumping of low and high viscosity fluids, including those that contain high solid content and shear sensitive mediums. The wide variety of materials that the diaphragm can be constructed of combined with the pumps’ seal-less design, means that even aggressive chemicals and acids can be handled.
As AODD pumps are powered by compressed air supply rather than an electric motor, they are a popular alternative solution for installations where mains power may not always be available. This is also why it is common for smaller sized air diaphragm pumps to be used in portable applications, and why they are often used in hazardous environments where in may not be safe to have an electricity supply. They are commonly used in industrial process throughout the UK as compressed air is very frequently used as a powered medium within these environments for driving other tools and equipment.
AODD pumps when fitted with a tube onto the exhaust of the pump which is vented to atmosphere outside the fluid (snorkel) can be submersed in a liquid.
The air operated diaphragm pump design makes it suitable for use in a wide range of industries:
The way in which an air operated diaphragm pump works means that there is some pulsation in its flow output. However this can be reduced by using pulsation dampeners in the discharge pipe, which then makes them suitable for metering applications and pulse sensitive delivery and transfer applications.
Below are the four common installation types for AODD pumps.
Various accessories can be supplied to optimise the use and installation of the air diaphragm pump:
Castle Pumps are fully accredited to enable you to buy with confidence. Our accreditation includes: A division of the CTS Group, Part of Flow Max Ltd.