How Does an Air Operated Double Diaphragm Pump Work?

An air operated double diaphragm pump is a pneumatic pump that uses compressed air to move two diaphragms back and forth. An air distribution valve alternates the compressed air between the two air chambers, causing one diaphragm to perform a discharge stroke while the other performs a suction stroke.

Because the diaphragms are connected by a common shaft, their movement is synchronized. As one fluid chamber empties, the opposite chamber fills. Check valves help control the direction of the liquid so that it enters through the suction manifold and exits through the discharge manifold. The alternating movement produces a continuous, pulsating flow as long as compressed air is supplied to the pump. ARO air operated diaphragm pumps are available with different fluid-section and diaphragm materials, helping users match the pump to the fluid’s chemical properties, viscosity, temperature, solids content and application requirements.

Pneumatic diaphragm pumps offer a number of advantages, namely:

• They allow for less wear to the diaphragm compared to a mechanically driven pump, due to the balance of pressure by the compressed air. This means that AODD pumps can run for longer periods of time without damage and have a longer lifespan as well.
• Their design allows full separation of fluids and sensitive part components, which reduces the frequency of repairs.
• They can handle abrasive and viscous sludges, slurries or fluids.
• Also, the smooth pumping mechanism of the pump means that they are well-suited for shear-sensitive fluid applications.
• As the only stationary seals in AODD pumps are between the wetted components and the exterior of the device, leakage can only occur if one or both of the diaphragms fail.
• Because their working mechanisms don’t produce a spark, AODD pumps are suitable for use in hazardous areas, such as where flammable materials are present.

Figure 2: Diaphragms which moves to the right

AODD pumps come with a range of benefits and can have somewhat specialized requirements for their installation. Adhering to these instructions can help avoid a variety of costs and damages to your AODD pump:

• They must be mounted on a rigid base or surface, as the mechanism of this pump’s diaphragms cause it to vibrate during operation. Suction and discharge connections should be flexible connections (such as a rubber hose), not ridged pipe, and should be compatible with the fluids being pumped.
• The fluid inlet suction pipe or hose should be at least the same size as the suction port. If this is not adhered to, pump starvation can occur. It also should be as short and as close to the supply vessel as possible.
• Ensuring a properly sized air supply line is crucial. Using an airline that is too small can lead to starvation of compressed air. Proper air flow is required for the AODD pump to operate effectively.
• To regulate the flow and pressure of AODD pumps, an air pressure regulator assembly should be installed in the pump’s air supply line to regulate incoming air pressure.