AOD/AODD Pumps

How do AOD and AODD pumps work?  

Both AOD (Air Operated Diaphragm) and AODD (Air-Operated Double Diaphragm) pumps pump fluid using positive displacement and are operated by compressed air. Compressed air is alternately fed to, and vented from, air chambers to create a pumping action. The main difference between AOD and AODD pumps is that AOD pumps have a single diaphragm while AODD pumps have two diaphragm that work in unison. In AOD pumps, the single diaphragm pushes and pulls to open and close the inlet and discharge valves, which draws fluid into the chamber and expels it out through the outlet port. In AODD pumps, the diaphragms fill and empty two separate pumping chambers, which are linked by bolts or clamps, to create a continuous pumping action. As one diaphragm fills a chamber, the other one empties its contents and the cycle repeats.   

Advantages of AOD and AODD pumps  

Using compressed air to activate the diaphragms gives the pump many advantages over motor driven pumps. Because air operation is intrinsically safe by design, the pump can be used in areas which are hazardous or where ATEX compliance is required. Other advantages include:  

Self-priming: AOD and AODD pumps are self-priming, which means they can draw fluid from a lower level and lift it to a higher level without the need for additional priming.  

Versatility: These pumps can handle a wide range of fluids, including corrosive, viscous, and abrasive materials, without damaging the fluid characteristics. Other than fluid handling capabilities, the pumps can run dry and ‘deadhead’ as well as operate while completely submerged. These capabilities make them suitable for a wide range of applications.   

Low maintenance: AOD and AODD pumps have few wetted and moving parts, making them easy to maintain and repair. The pumps do not require oil lubrication which also reduces the need for maintenance as well as helps to avoid contamination of the pumped fluid.  

Efficiency: The pumps have a consistent flow rate, making them ideal for applications that require precise fluid transfer.   

Cost-effective: AOD and AODD pumps are generally less expensive to purchase and operate than other types of pumps, especially in applications where electricity is not readily available. No expensive mechanical seals or packings are required, adding to their cost-effectiveness.  

The versatility, safety, low maintenance, efficiency, and cost-effectiveness of AOD and AODD pumps make them a popular choice for many different industries and applications.  

 Applications  

AODD pumps have gained a strong reputation across various industries for their ability to pump abrasive and viscous liquids, as well as operate in challenging conditions. They are versatile and suitable for use in both clean and hazardous environments, making them a go-to solution for a wide range of applications.   

The industries where AODD pumps can provide safe, reliable, and cost-effective performance are vast and diverse, including ceramics, paints, coatings, aerospace, wastewater treatment, chemical processing, paper and pulp, and automotive, among others. Some common applications of AODD pumps include:  

• Transferring hand gel from bulk tanks to filling machines in sanitary product manufacturing.  
• Separating aggressive particulates from industrial wastewater for solids separation and water recycling.  
• Removing water from bins containing discharge paint sludge in dewatering plants to reduce the weight of the load in the bins and waste disposal costs.  
• Emptying pipelines in oil production facilities where the media is potentially explosive.  
• Offloading liquids in bulk tankers and containers.  
• Handling dry powders, such as silica, during offloading from bulk tankers, where the pumps are essentially pumping air with powder.  

 Heavy-duty design  

AxFlow's product range includes heavy-duty AODD pumps, in addition to standard design AOD/AODD pumps, which offer several advantages in handling abrasive slurries, suspended and non-suspended solids, and large-size solids, making them suitable for various industry sectors. The Heavy-Duty Flap Check Valve pumps have a design that optimizes flow capacity, reduces air consumption, ensures continuous performance, and provides minimal flow velocity changes when handling thick and viscous fluids. With their thick walls and large flow area, these pumps prevent solids from settling in the unit. The Heavy-Duty Ball Valve pumps have similar construction but with smaller ports and various discharge porting options. These pumps are suitable for thin to highly viscous and small solids-laden liquids and are designed for use in tight spaces. Finally, the Containment Duty Ball Valve pump has been developed for handling potentially dangerous fluids, preventing leakage, and providing added safety and peace of mind in certain circumstances. 

Selecting the right pump  

Some key considerations for selecting an AODD pump for your application and need include:  

• Fluid: Determine the type, composition, and consistency of the fluid you plan to pump to avoid wear and tear or corrosion. Also, consider whether it is a clean or slurry liquid.  

• Viscosity: Highly viscous fluids require robust pumping equipment, so factor in the viscosity of the fluid in the pump selection process.  
• Pressure: Determine the potential pressure conditions on the inlet and outlet of the pump to ensure that the pump can handle the required pressure.  
• Temperature: The temperature of the fluid dictates the pump material best suited to a particular application.  

When considering heavy-duty AODD pumps with flap check and ball valves, it is important to evaluate their technical capabilities for efficiency and reliability before making a final decision.  

The only significant limitation of AODD pump design is the suction pressure, which is dictated by atmospheric pressure, and can limit performance. To optimize performance, it is best to position the pump as close as possible to the tank or vessel holding the liquid.   

Why buy AOD and AODD pumps from AxFlow  

AxFlow offers AOD and AODD pumps and accessories for the widest range of industries and applications. Only at AxFlow do you receive individual advice from industry-experienced process engineers and the manufacturer-independent selection of the world's leading process technology. Do you need support in selecting the right pump for your needs? Do not hesitate to get in touch. AxFlows experts and engineers can provide guidance for selecting, specifying, installing, and maintaining your pump.