Hello and thank you for being in a new occasion in our blog. Today we are going to try to approach how to solve the problems of your pneumatic double diaphragm pump, also known as AODD pumps for their abbreviations in English.
Air-Operated Double Diaphragm (AODD) pumps are generally very easy to install. Simply connect the process piping and a suitable air line, supply compressed air and the pump should be operational, although we will provide some installation tips in a later article.
Troubleshooting your air operated double diaphragm pump
It is always good practice to ensure that all fasteners are tight and correctly adjusted, especially the nuts that secure the housings where the diaphragms or diaphragms are housed.
A good starting point if the problem has appeared in an existing pump that may have been installed is to ask: Has the application changed? Try to find out the history of the pump and the application and try to establish if anything has changed, e.g. the product pumped, the required flow rates, process piping, cleaning procedures, air supply, etc.
Has the pump been inspected or serviced recently and was it working before it was disassembled and reassembled? Failure to operate after reassembly is an obvious "red flag" for incorrect assembly.
If the pump does not work, what to do?
- Check that all valves are open
- Suction line
- Drive line
- Air supply line
2. Check that you have enough air available. Pneumatic pumps can easily run out of air and simply increasing the size of the air line or the volume of air available can solve many problems.
- Check that the main air line is not kinked and that there are no air leaks.
- Check the diameter of the air line:
- Minimum 10 mm on pumps with 7 or 10″ diaphragms
- Minimum 20 mm in pumps with 12 or 14″ diaphragms
- Air pressure: the pumps need between 2 and 7 bar to operate.
- Air volume: check the volume required in the manufacturer's data sheet.
3. Check that the pressure in the delivery line is not equal to or higher than the air pressure to the pump:
- If the air pressure is lower than the liquid pressure in the delivery line, the pump will not start.
- Once the pressure in the delivery line drops below the air pressure given to the pump, it will pump again.
4. If the Pump has been serviced or disassembled for inspection, check the correct installation of the pneumatic exchanger.
5. Check the free movement of the air valve by pressing it several times. It should move easily without seeming too loose.
- Contamination by "dirty" air can restrict movement within the air valve, causing irregular operation.
6. Check the inside of the pump
- Diaphragms - Replace if damaged
- Air Exchanger - Ensure that all air ducts are clear.
7. Check the silencers fitted to the air valve: clogged silencers will cause the pump to stop working.
If it is not primed, how can it be solved?
- Check that the application is within the pump's capabilities: most Seko Duotek pumps have a dry suction lift of 5m.
- Check that all process piping valves are open.
- A closed valve in the suction line will prevent priming of the pump.
- A closed valve in the delivery line can cause an "air lock" which can stop the pump from priming.
- Check that there are no leaks in the suction pipe: any leakage may cause air to enter the pipe instead of product.
- Check that the suction pipe is reinforced and able to withstand the vacuum without collapsing, and that there are no kinks in the pipe between the source and the pump.
- Check that the suction pipe is of the correct diameter and length for the application: thicker and more viscous materials will require a larger diameter and short lengths between the liquid source and the pump.
- It is also good practice to start the pump slowly when working with high viscosity products. This allows the pump to prime and, once primed, it can be accelerated for the most efficient pump operation.
- Make sure that there is no filter in the suction line.
- Check internal pump components for wear and replace if necessary:
- Pneumatic distributor
- Balls and seats
What if the AODD pump does not deliver enough flow?
- Check that the application matches the capabilities of the pump (operating diagrams are available in the manufacturer's documentation).
- Check the diameter and length of the suction/inlet pipe and the pipe routing.
- All piping must have at least the same diameter as the pump inlet and outlet connections.
- All pipes should be kept as straight and short as possible, which is especially important in the case of suction pipes for a viscous material.
- Check that the pump is receiving sufficient air pressure and volume.
- Check that there are no restrictions or partially closed valves in the suction and supply air lines.
- Make sure that there are no filters in the suction or delivery pipes.
- Check internal pump components for wear and replace if necessary.
- Pneumatic distributor
- Balls and seats
- Diaphragms
- Check air silencers
- Clogged or restricted silencers can slow down the pump and even stop it.
- Frozen" silencers can have the same effect. In this case the compressed air should be dehumidified and filtered.
What to do if the pneumatic double diaphragm pump leaks product?
- Check that the main nuts are sufficiently tightened.
- Check that the nuts/bolts on the manifolds are sufficiently tightened.
- If the manifolds are sufficiently tightened and leakage still occurs, check the manifold O-rings for damage or, in the case of PTFE O-rings, "crushed".
- The tightening torques are available in the Pump Installation and Operation Manual.
- If product is leaking from the silencers, check that the diaphragms are sufficiently tight and have not failed.
ProDos is a specialist in air operated double diaphragm pump problems. Please do not hesitate to contact us if you have any questions.
