What is AODD Pump? | How Air-Operated Diaphragm Pump works?

The pumps are used for a wide range of industrial applications. The pumps have multiple types designed for different applications. An Air-Operated Double Diaphragm (AODD) Pump is a most commonly used industrial pump. AODD pumps use in industries for a smooth operation. These pumps have extremely high reliability and efficiency. They are handy and best ideal for multiple industries from beverage to mining and food production. This article mainly explains different aspects of the Air-Operated Double Diaphragm (AODD) pump.

What is an Air-Operated Double-Diaphragm pump?

The AODD Pump is a famous type of reciprocating pump. This pump has two pumping cylinders and two flexible membranes or diaphragms. The flexible diaphragm or membrane firstly fills the cylinder, pressurizes the fluid, and discharges it to the desired area.

The AODD (Air Operated Double Diaphragm) Pump uses compressed air to drive the repetitive reciprocating motion of the flexible membranes attached to the connecting rod. This reciprocating of the membrane discharges fluid from one cylinder and transfers it to the second cylinder.

These types of pumps are best suitable to safely pump the viscous liquid. AODD pumps have the capability to control the toughest liquids in the harshest conditions. With only a few parts, this pump remains reliable with low maintenance.

Air Operated Double Diaphragm pumps are most commonly used to transfer shear-sensitive liquids, abrasive slurries, and sludges. They have high reliability and easy maintenance. The main disadvantage of the AODD pump is that it generates high noise and is prone to icing. 

Working of AODD Pump

An AODD pump works on the positive displacement principle. It uses compressed air to drive the diaphragms. The reciprocating motion of the diaphragms compresses the fluid and transfer it to the desired area. However, you can drive the diaphragm pump directly by connecting it to an electric motor via a shaft. An Air Operated Diaphragm pump works in the following way: 

AODD PUMP working
(Refer: https://www.michael-smith-engineers.co.uk)
  1. First of all, the control system transfers compressed air into cylinder A.
  2. For the suction stroke, the crankshaft shifts the diaphragms from the right to the left side.
  3. As the diaphragms move to lift, the volume of cylinder A decreases, and the volume of cylinder B increases. In such conditions, the fluid starts going from cylinder A to cylinder B.
  4. When the diaphragms complete their first stroke, the air valve transfers compressed air from cylinder A to cylinder B.
  5. For the second stroke (discharge stroke), the shaft shifts the diaphragms to the right. During this stroke, the volume of chamber A increases while the volume of cylinder B decreases.
  6. As the volume of cylinder A becomes more than the volume of cylinder B, the fluid starts going from cylinder B to cylinder A.
  7. When the second stroke completes, the air valve discharges compressed air from cylinder B and transfers it to cylinder A, and the whole cycle repeats.

Advantages of an AODD pump

  1. The Air-operated double diaphragm pump has no leakage issues. It has a tight seal between the external environment and the wetted components of the pump. Therefore, leakage issues will only appear if one or both membranes fail.
  2. The rotating parts and internal parts of this pump don’t need lubrication.
  3. Compared to mechanically operated diaphragm pumps, AODD pumps have less membrane wear due to the advantage of pressure equalization of the compressed air supply.
  4. They can run dry forever without suffering damage.
  5. These types of pumps have the capability to pump slurries, sludges, high viscosity fluids, and abrasives. You may also use them to transfer shear-sensitive liquids.
  6. These have self-priming capability.
  7. They don’t have priming problems.
  8. They have up to 8m suction lift capability.
  9. This pump consumes low energy and reduces the electricity bills because it uses compressed air as power instead of electrical power.
  10. They are the best ideal to use in hazardous applications.

Disadvantages of an AODD pump

  1. The Air-operated double diaphragm pumps are costly than the centrifugal pumps.
  2. The AODD pump can’t deliver constant flow.
  3. These types of positive displacement pumps need frequent maintenance.
  4. The stability and efficiency of these pumps vary according to the supply of compressed air. The pressure of the compressed air supply must be equal to or more than that of the medium to be pumped. This condition limits the use of these pumps to low pressure (i.e., 120 psi) applications.
  5. When the pressure of the compressed air supply increases or the pressure of the pumping fluid decreases, the pumping speed increases. In the case of constant flow, additional flow and pressure controls are required.
  6. A poorly designed air distribution system can produce icing problems. Continuous air discharge can lead to cooling, and in extreme cases, ice can form in the distribution system or around the ventilation slots.
  7. These pumps generate very high noise.

Application of AODD Pump

  • Pumping Wastewater
  • Circulating ceramic slurry
  • Filling moulds
  • Day tank transfer
  • Ceramic slips
  • Pumping fuels for cars and other machinery
  • Pumping solvents for separating minerals
  • Dosing reagents
  • Pumping sludge and abrasive slurries mixtures

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