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How Does An Air Operated Diaphragm Pump Work

By | December 10, 2021

How Does An Air Operated Diaphragm Pump Work


An Air Operated Double Diaphragm Pump (AODD Pump) is a Positive Displacement Pump; where air pressure is used to drive 2 flexible Rubber / PTFE diaphragms back and fore. This causes negative and positive pressures in the respective wet chambers of the pump. A set amount of liquid, equal to the diaphragm displacement, then fills the one chamber under negative pressure and is forced out of the other chamber under positive pressure, at the same time.

Other gases can be used to drive the pump; for example Nitrogen or even Natural Gas if required.


Pump Animation Available

Compressed air is alternately applied to the back of each of the 2 diaphragms, controlled by our unique fully pneumatic air valve / air distribution system. The diaphragms are secured onto a thrust tube which means that when the pressure is placed onto the back of one diaphragm it is pushed forward; and because it is attached to the Thrust Tube the opposite diaphragm moves backwards at the same speed. As this Diaphragm / Thrust Tube assembly move back and fore it gives alternate air signals to the Air Valve to switch.

This produces a negative pressure in one of the liquid chambers. Atmospheric pressure then tries to equalize the pressure outside and inside the liquid chamber. Any liquid between the atmosphere and the liquid chamber under negative pressure will be pushed into the wet chamber, lifting the delivery balls as it does so. Note: Atmospheric pressure is the only ‘driving’ force involved, the pump does not ‘pull’ liquid into the wet chamber. Regardless of what air  pressure you give the pump is still relies on atmospheric pressure to ‘force’ the liquid into the pump.

At the same time a positive pressure is generated in the opposite liquid chamber. This positive pressure pushes down on the bottom (inlet) balls sealing the suction manifold and at the same time forces any liquid in the wet chamber against the top (outlet) balls, thereby lifting them and forcing the liquid through the delivery manifold and out of the pump. Note: any liquid in the wet chamber is being ‘driven’ out by the compressed air given to the pump. Full air pressure is available to ‘force’ the liquid out of the pump and into the delivery pipework.

This process then repeats for as long as compressed air is supplied to the pump.


The beauty of AODD pumps in general and specifically the Unique 'One Nut' designed Flotronic version is the simplicity of design and small number of moving parts:

  • An air valve supplies air pressure to back of either of the 2 diaphragms. 
  • This air pressure is used to drive the 2 diaphragms, which move in unison, causing negative and positive pressure in the respective wet chambers of the pump.
    • Negative pressure in one wet chamber results in atmospheric pressure pushing liquid into the pump
    • At the same time positive pressure caused in the other chamber by the driving air acting on the back of the diaphragm, drives liquid out of the pump.

4 Non return Balls / Valves, control the direction of liquid flow.



Appropriate Pumps

Good Food Pump                    Chemflo PTFE Pump             Minichem PTFE Pump

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