6 Steps to Solve Common Problems with Air-Operated Double Diaphragm Pumps (AODD)

Aug,08,2023

Air-operated double diaphragm pump (AODD) is an ideal choice for fluid transfer due to its simple design, easy operation and low maintenance cost. To ensure the best performance of the AODD pump, it is necessary to ensure that the diaphragm pump is installed and operated correctly. If you encounter problems during installation or operation, try these 6 quick and easy ways to troubleshooting and fix common problems.

1. Check the size and pressure of the air inlet pipe

The most common mistake associated with AODD pumps is that the installed air pipe size is too small. The diaphragm pump needs enough compressed air to ensure performance, and if the air pipe is too small, the pump will have insufficient air supply. Larger AODD pumps (1 inch and above) require more compressed air than smaller AODD pumps, and the piping therefore needs to be thicker. Refer to the manufacturer's installation and operation manual for the correct size of the air pipe to be configured with the diaphragm pump. According to general experience, the inlet pipe diameter of AODD pump air valve should match the size of air pipe hose.

The air inlet pressure also plays a role in optimizing the performance of the pump. The diaphragm pump operates at a 1:1 ratio. This means that the air supply pressure of the pump is directly related to the fluid pressure at the pump outlet. If the target outlet pressure of a 1", 50gpm pump is 100psi, the air inlet pressure into the pump air valve must also be greater than or equal to 100psi.

Fluid viscosity and system back pressure can affect the pressure of the outlet fluid. Too little back pressure can reduce pump operating efficiency because the ball check valve may not check the fluid quickly. If the back pressure is too large, it may cause the pump to stall when the fluid pressure overcomes the air pressure. In order to control the flow, pressure and performance of the AODD pump, an air regulator must be installed to control the air inlet pressure. Choosing the right air pipe size, coupled with an air conditioner, can solve the most common problems with AODD pump installation.

2. Check the muffler for ice and blockage

A muffler is recommended for AODD pumps as it helps not to make high noise when the pump is running at full speed. Compressed air is needed to run the pump's air motor. When the compressed air enters the air valve and is discharged by the muffler after through the central section of the pump, the temperature will change rapidly. Because the air temperature at the exhaust of the muffler is well below freezing point, it may cause problems related to icing. This situation is particularly common in high humidity environments.

If the diaphragm pump operates unsteadily, the air humidity at the inlet is high, or if you see the front end outside the muffler, you may be facing problems related to icing. Try the following solutions to eliminate the problem and restore pump operating efficiency.

（1）Reduce pump air pressure

（2）Increase the size of the pump and operate at low speed (i.e. lower air pressure)

（3）Exhaust the air to a distant place through the exhaust pipe

（4）Add air pipeline filter with water collector and drain to collect condensate

（5）Install an air pipeline heater to raise the exhaust temperature above freezing

（6）Use an air compressor dryer to regulate the pressure dew point temperature

3. Check whether the sealing surface is leaked

All types of pumps are prone to leakage problems. To make sure the liquid stays inside the pump and not on the ground, try the following:

（1）Tighten the pump according to the pump instruction manual provided by the manufacturer and connect the pump according to the bolt connection diagram.

（2）When repairing AODD pumps, replace all PTFE O-rings used for pumps. PTFE is a versatile material, but it cannot be restored to its original shape after compression.

（3）Tighten the pump correctly as per manufacturer's requirements and ensure that the sealed O-ring is replaced during use to prevent leakage of the pump.

4. Make sure the pipe size is correct

The inlet and outlet fluid port diameter of the diaphragm pump varies according to the required flow rate. The size of the inlet and outlet hose must match the size of the diaphragm pump. The main problem associated with this is the possible risk of cavitation, increased repair frequency and repair costs.

If a 1 inch diaphragm pump is connected to a 1/2 inch inlet hose, the diaphragm pump will not be able to operate at full capacity and will not create cavitation. This risk rises as the viscosity of the liquid increases. 1 inch diaphragm pump should use 1 inch inlet and outlet hoses to avoid cavitation and frequent, costly repairs.

For AODD pumps, flexible inlet and outlet connection pipes are recommended to avoid hard pipes. As the diaphragm pump speed increases, the vibration will increase. With the increase of vibration, the risk of hard connection pipe loosening increases, and leakage is easy to occur.

5. Slow down the pump to self-priming state

In the need for self-priming occasions, people often use AODD pumps. The AODD pump pumps the fluid by creating a low pressure zone in the fluid where the atmospheric pressure is below 14.7psi. If the air supply pressure of the pump is too high, and the pump switches too fast, there is not enough time to suck the liquid into the diaphragm pump.

The solution to the self-priming problem is to use an air regulator to reduce the air pressure entering the air valve and reduce the speed of the pump to ensure that the liquid has enough time to enter the pump. Once this is achieved, the air pressure can be increased and the pump operation speed will be accelerated.

6. Clear all fluid pipeline blockages

The final step to ensure optimal pump performance is to remove any blockage in the fluid pipelines. Blocked pipelines create back pressure, cavitation, and increased maintenance risks. To resolve this issue, you need to find and eliminate the following conditions:

（1）A closed or partially closed valve

（2）The line is kinked or blocked

（3）Too many hoses or too long distance

The above six steps will help solve common problems with AODD pumps, helping pumps achieve optimal performance and reduce downtime.

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