When Air Operated Double Diaphragm (AODD) pumps were first introduced to the market over 60 years ago, they offered an interesting seal-less (does not use packing or mechanical seals to isolate the process fluid), positive displacement alternative to centrifugal pumps and quickly gained traction in the manufacturing world. Over the past six decades, the market has seen many innovations in AODD pump technology. Interesting variations on pump design and changes to diaphragm construction have given AODD pumps the edge over alternative pumping methods in liquid-transfer applications.
David Rozee, Managing Director of Tri-Ark Ltd., a finalist in the 2015 Pump Industry Awards, explains how AODD pumps fit into pump system optimization.
Multiple options for construction
AODD pumps have found applications in industries, ranging from chemicals, food processing, paints, electronics, mining and everything in between. Air operated double diaphragm pumps come in a variety of sizes and materials of construction and their versatility means there is a pump for every fluid.
Materials of construction include bodies in acetal, aluminium, cast iron, polypropylene, PTFE, Stainless Steel and Kynar and many elastomers choices. The material and size selected can be selected to cope with almost any fluid that needs to be pumped.
The simplicity of AODD pumps makes them appealing to everyone from amateur to professional users. They are best described as a ‘plug in and play’ product because once they are connected to a compressed airline, they effectively take care of themselves; they can run dry dead-head without damage. Their ease of use combined with a highly effective capability of pumping most materials, makes them the pump of choice for many in the industry.
Safety is key
Since AODD pumps use compressed air as their only power source, they are intrinsically safe and are available ATEX Certified for use in applications where it is not possible to use electricity or it is dangerous to do so, such as in hazardous or explosive environments or at remote sites.
Flexibility and discharge capability
AODD Pump sizes from ¼” to 4” are available giving flow rates between 19lpm and 1,100lpm. With manufacturers offering a range of flexible sizes, users can buy a pump that will give them a perfectly balanced system. To give an idea of what this means in real terms, a ¼” pump will empty an IBC (1,000litres) of water in 53 minutes whereas a 3” pump will take just 1 minute.
Another attraction of AODD pumps comes from the fact that standard units 1:1 ratio pumps, meaning the air pressure in equals the fluid pressure out giving potential discharge pressures of up to 8bar. All this without mentioning the high pressure e.g. 2:1 ratio pumps. More on these units next time…