Exploring the efficiency and reliability of air-operated double diaphragm pumps
PUMPS
Air-operated double diaphragm pumps (AODD) have become a staple in numerous industries due to their exceptional versatility, efficiency, and reliability in fluid transfer applications. Pipes, Pumps and Valves Africa finds out more. As positive displacement pumps, AODD pumps are proving their worth. Relying on compressed air to drive their operation, they are crucial for managing a wide range of fluid types, including viscous, abrasive, and shear-sensitive substances. These pumps are distinctive in their ability to handle dry running and deadheading scenarios, solidifying their position as a reliable choice across various industries, says Michael Um, product manager at Wilden. Whether pumping water, aggressive acids, food products or solid-laden slurries, manufacturers of AODD pumps have realised that improved diaphragms are central in achieving better, more reliable pump performance. Over the years companies such as Wilden have invested extensively in research and development of diaphragms with some very meaningful revisions taking place.
The ingenious operation of AODD pumps AODD pumps operate by using compressed air to shift diaphragms, displacing fluid from one of two liquid chambers during each stroke. The diaphragms in each chamber are linked by a single shaft, enabling them to move in unison. The process begins with applying pressurised air to the back of diaphragm A, initiating chamber B's suction stroke. This creates a vacuum within chamber B, allowing atmospheric pressure to force fluid through the inlet ball valve and into the chamber. As diaphragm A completes its discharge stroke, pressurised air is redirected to the back of diaphragm B, starting chamber B's discharge stroke. The hydraulic forces within chamber B facilitate fluid flow through the pump's discharge, mirroring a similar process in the opposite chamber. This cycle continues until the inlet air supply is interrupted or discharge pressure equals the air inlet pressure. Central to the functioning of AODD pumps are diaphragms, explains Um. "These critical components facilitate fluid movement from the suction to the discharge side. However, diaphragms are prone to wear and tear due to their constant flexing and exposure to various fluids and environmental conditions. Similar to a car's tires, diaphragms are regularly replaced parts. Understanding the nuances of diaphragms—material types, designs, and compatibility—is therefore pivotal in achieving longer durations between repairs." Factors influencing diaphragm failures According to Um, diaphragm failures can stem from many factors, including forced inlet pressure, outer piston abrasion, flex creases, chemical attacks from incompatible fluids, and excessive temperatures. "Each failure type can be exacerbated by the application's unique demands, compatibility issues, or temperature extremes," he says. "Selecting the appropriate diaphragm material and design tailored to specific temperature limits is essential for prolonging the pump's longevity and efficiency." Many manufacturers offer downloadable guides and manuals that align diaphragm designs with temperature requirements to aid in diaphragm selection. Ensuring compatibility between material and application conditions can significantly minimise the risk of failure. It's imperative to use authentic or OEM parts to prevent voiding the pump's warranty and to avoid detrimental impacts on operational safety and flow rates, warns Jorge Hernandez, a product specialist at PSG.
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Pipes, Pumps and Valves Africa - Sep/Oct 2023