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Air-operated Double-diaphragm (AODD) Pumps

What to Consider When Selecting an AODD Pump for Hazardous Fluids

| Author / Editor: Edison Brito / Dr. Jörg Kempf

Air-operated double-diaphragm (AODD) pumps have only a few wetted parts and are driven by compressed air rather than an electric motor.
Air-operated double-diaphragm (AODD) pumps have only a few wetted parts and are driven by compressed air rather than an electric motor. (Picture: Wilden)

Dangerous chemicals — those considered highly corrosive, toxic or potentially explosive — require careful selection of pumps and pump components to protect workers and the environment. When it comes to determining which pumping technology is best suited for handling a dangerous chemical, numerous factors must be taken into consideration.

Pumps play a critical role in the handling and transfer of dangerous chemicals, as they are used throughout the chemical supply chain to move fluids to and from pipelines, railcars and road tankers, storage tanks and process vessels. With multiple transfer points in the process, it is crucial that manufacturers select the proper pump for their specific applications. When pumping dangerous fluids, system designers and operators should consider the following:

  • chemical compatibility for all wetted parts;
  • guaranteed leak-free operation;
  • constant flowrates with no slippage; and
  • reliable operation in harsh conditions and hazardous atmospheres.

One technology which meets all four criteria is air-operated double-diaphragm (AODD) pumps. These reciprocating, positive-displacement pumps have only a few wetted parts and are driven by compressed air rather than an electric motor. This allows AODD pumps to run dry and at shut-off without damage, while their self-priming capabilities give AODD pumps superior suction lift over competing technologies. Other technologies like lobe and gear pumps have disadvantages which make them less reliable in handling dangerous chemicals. Lobe pumps, for example, are prone to wear and hence product slippage, which adversely affects flowrates and production volumes. With gear pumps, the meshing gears will begin to wear as soon as the pump is turned on. As gears wear, volumetric consistency is compromised, leading to reduced or inconsistent flowrates and increased energy consumption.

When compared to centrifugal and gear pumps, whose turbulence can damage the particulates present in certain fluids, AODD pumps provide a gentle pumping action. The absence of friction reduces the shear that can alter the fluid properties. AODD pumps also offer a variety of compatible materials of construction depending on the chemical being used. And, by removing the need for mechanical seals, AODD pumps provide virtually leak-free product containment.

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