How do double diaphragm pumps work?

Advantages of a double diaphragm pump

The AODD pump is a versatile workhorse for a huge range of fluids. Providing the site has a compressed air supply, you have a robust pump ready to run.

THE WORKING PRINCIPLE OF A DOUBLE DIAPHRAGM PUMP

A double diaphragm is a positive displacement pump which utilises two flexible diaphragms that reciprocate back and forth, creating a temporary chamber, which both draws in and expels fluid through the pump. The diaphragms work as a separation wall between the air and the liquid.

The first stroke

The two diaphragms that are connected by a shaft through the centre section where the air valve is located. The purpose of the air valve is to direct the compressed air to the back of diaphragm number one causing it to move away from the centre section. The number one diaphragm causes a press stroke moving liquid out of the pump. At the same time diaphragm number two is performing a suction stroke. The air behind diaphragm number two is being pushed out to the atmosphere causing atmospheric pressure to push the liquid to the suction side. The suction ball valve is pushed away off its seat allowing the fluid to flow past the ball valve into the liquid chamber.

The second stroke

When the pressurised diaphragm number one has reached the end of its stroke, the movement of the air is switched from diaphragm number one to the back of diaphragm number two by the air valve. The compressed air pushes diaphragm number two away from the centre block resulting in diaphragm number one being pulled toward the centre block. In pump chamber number two the discharge ball valve is pushed off its seat, whilst in pump chamber number one the opposite occurs. Upon completion of the stroke the air valve leads the air again to the back of diaphragm number one and restarts the cycle.

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Where can double diaphragm pumps be used?

Diaphragm pumps are a common site in many industries. There is an extensive number of construction materials available to produce a bewildering number of configurations to accommodate difficult fluids such as 

  • Corrosive chemical
  • Volatile solvents 
  • Viscous, sticky fluids
  • Shear-sensitive foodstuffs and pharma product
  • Dirty water and abrasive slurry
  • Smaller solids
  • Creams, gels and oils

In addition to the fluid handling properties an AODD pump can be specified for ATEX zones, EC1935/2004, FDA and 3A hygienic applications amongst other industry compliance measures. 

Why air operated diaphragm pumps?

The AODD pump is a versatile workhorse that enables users across a hugely diverse range of industries to standardise on a single pump type that for handling a wide variety of fluids. So long as there is a compressed air supply available the pump can be installed wherever it is required and should circumstances change it can be moved round a plant and switched to other operations with ease. Whether to fluid being handled requires a gentle pumping action, is chemically or physically aggressive the positive displacement AODD pump offers an efficient and low maintenance solution.