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Troubleshoot Your Air Operated Double Diaphragm Pump

By | March 15, 2022

How to Troubleshoot Your Air Operated Double Diaphragm Pump

Air Operated Double Diaphragm Pumps (AODD) are very easy pumps to install. Simply connect the Process Pipework, and a suitable Air Line, turn on the air and the pump should run.


It is always good practice to ensure all fastenings are tight and correctly torqued up, especially the main 'One Nut' on the Flotronic Range.

A good place to start if the problem has appeared on an existing pump is by asking the question; Has The Application Changed? Try and get the history of the pump and application and try to establish if anything has anything changed; for example, product being pumped, flow rates required, process pipework, cleaning procedures, air supply?

Has the pump recently been inspected or maintained, was it working before it was stripped down and rebuilt? Not working after a rebuild is an obvious 'red flag' for incorrect assembly. 


  • Check all valves are open
    • Suction Line
    • Delivery Line
    • Air Supply Line
  • Check you have enough air available, Air Operated Pumps can be easily starved of air, and simply increasing the air line size or the volume of air available can solve many issues. 
    • Check that the main airline isn't kinked, and that there are no air leaks.
    • Check the diameter of the Air line
      • Min 10mm on pumps with 7" or 10" Diaphragms
      • Min 20mm on pumps with 12" or 14" Diaphragms
    • Air Pressure - Pumps require between 2 and 7.2 Bar to run
    • Air Volume - Check the Volume required on Company Brochures .
  • Check the pressure in the delivery pipework is not equal to or more than the air pressure being given to the pump:
    • If the air pressure equals the delivery pipework liquid pressure the pump will 'Dead Head' and not cycle.
    • Once the pressure in the delivery pipework drops below the air pressure being given to the pump, it will restart.
  • If the Pump has been maintained or stripped for inspection - check the orientation of the Thrust Tube in the center of the Pump.
    • Bearings located in the middle of the Thrust Tube have to be closest to the Air Valve side of the pump.
  • Check the free movement of the Air Valve by pressing the Signal Buttons supplied on the Air Valve - should move easily without appearing to be too loose.
    • Contamination from 'dirty' air can restrict movement within the air valve, causing stalling or unequal running
  • Check the Pump Internals
  • Check the Silencers fitted to the Air Valve - Blocked Silencers will stop the pump from Cycling - 'Iced Up' Silencers can have the same effect.



  • Check the application is within the pumps capabilities - majority of 'One Nut' pumps have a 3.6m Dry Suction Lift.
  • Check all process pipework valves are open
    • Closed valve in suction pipework will stop pump priming.
    • Closed valve in delivery pipework can cause an 'air lock' which can stop pump priming.
  • Check there are no leaks in the suction pipework - any leaks can result in air getting into the pipework instead of product.
  • Check the suction pipework is reinforced and able to take the vacuum without collapsing and that there are no kinks in the pipework between the source and the pump. 
  • Check Suction Pipework is the right diameter and length for the application - thicker more viscous materials will need larger diameter and short runs between the source of the liquid and the pump.
    • It is also good practice to start the pump slowly when dealing with high viscosity products. This allows the pump to prime, and once primed the pump can be sped up to reach the most efficient pump operation.
  • Ensure that any filter in the Suction Line is clear.
  • Check Pump internals for wear, and replace as necessary:


  • Check the application is with the pumps capabilities - Flow charts available on Company Literature
  • Check Diameter and Length of any Suction / Deliver Pipework, along with the Pipework 'Run'.
    •  All pipework should be the same diameter as the pump inlet and outlet connections as a minimum.
    • All Pipework should be kept as straight and short as possible, this is especially important with the suction pipework on a viscose material.
  • Check the pump is getting enough Air Pressure and Volume
  • Check there are no restrictions or partially closed valves in the suction & delivery pipework.
  • Ensure that any filters in the Suction or Delivery lines are clear.
  • Check Pump internals for wear an replace as necessary
  • Check the Air Silencers (Mufflers)
    • Blocked or restricted Silencers can slow the pump down and eventually stop it.
    • 'Iced Up' Silencers can have the same effect.


  • Check Main Nut is tight enough
  • Check Manifold Nuts / Bolts are tight enough
    • If the manifolds are tight enough and there is still leakage; check that the Manifold O Rings are not damaged or in the case of PTFE O Rings 'flattened off' - replace as necessary.
  • Torque figures available in Pump Installation and Operation Manual
  • If product is leaking from silencers check diaphragms are tight enough, and have not failed.


Operation and Installation manuals for the Flotronic One-Nut range can be found on our Brochures and Downloads Page.


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