Since its invention in 1955, the air-operated double-diaphragm (AODD) pump has built a reputation as a technology that is ideally suited for utilitarian, auxiliary or basic liquid-handling applications. AODD pumps excel in these applications because of their simple, seal-less operation and their ability to self-prime, run dry, achieve suction lift up to 30 feet (9 meters or 14.7 psia), resist deadhead pumping conditions, operate while submerged and pass solids up to 3 inches (76 mm) in diameter.
Because of these characteristics, AODD pumps are ideal for many of the fluid-handling tasks in the chemical-processing industry. In fact, there are four areas where AODD pumps will outperform competitive technologies in terms of efficient, reliable and cost-effective operation.
1) The Importance of Air
AODD pumps operate via compressed air, and keeping air usage low is critical to maintaining a healthy environment and processing plant. Recent advances in optimized air consumption focus on the one slight shortcoming in AODD pump operation – at the end of every stroke, a small amount of air is consumed that does not contribute to fluid movement.
Because of that trait, AODD-pump manufacturers have searched for ways to eliminate the air (or energy) loss at the end of the pump stroke. A new pinnacle of air-distribution system (ADS) operation was reached in 2013 when Wilden® Pump and Engineering Co., completed the development of the Pro-Flo® SHIFT ADS technology.
This redesigned ADS features a revolutionary air control spool that reduces the amount of air that is allowed into the pump at the end of the stroke. This allows the pump to realize up to 60% savings in air consumption (over competitors), improves suction-lift capability and enables the handling of high inlet pressures, all while delivering more yield per standard cubic foot per minute (scfm) of air consumed.
2) Low Maintenance Through Proper Diaphragm Selection
Compared to many rotating-pump technologies, diaphragm pumps don’t require any seals, which makes them a true "set-and-forget" type of pump – provided that the proper diaphragms are selected for the application.
Chief among the recent improvements in diaphragm construction and function are long-life diaphragms that require less maintenance, which lowers repair and replacement costs. Wilden has contributed in this area with its Chem-Fuse Integral Piston Diaphragm (IPD). Unlike conventional diaphragms, the outer piston in the Chem-Fuse IPD is completely encapsulated within the diaphragm’s thermoplastic (TPE) elastomer material, which eliminates any chance for outer-piston abrasion to occur. Secondly, it also eliminates a known leak point in traditional diaphragm designs around the outer piston. Finally, the IPD removes an area along the outer piston where pumped fluid can be trapped.
The various models of Wilden® bolted AODD pumps offer many operational advantages for chemical processors, including optimized flow paths, easy maintenance, quick assembly and disassembly, and the ability to be a bolt-to-bolt and pipe-to-pipe drop-in replacement for competitive pump models.
3) Versatile and Compatible
AODD pumps can also match the supposed benefits of competing pump technologies in chemical processing because they have a number of operational advantages:
- Can be used with fluids from water-like to high-viscosity
- Can run dry and strip discharge lines without getting damaged
- Control relies solely on solenoid operators, pump-cycle counters and surge-dampener assemblies
- Operating costs are lower when all maintenance, accessories and controllers are considered
Also, a new generation of AODD pump styles – highlighted by Wilden’s bolted pump models – have been designed to be direct bolt-to-bolt and pipe-to-pipe drop-in replacements in existing pumping systems. Finally, the operation of AODD pumps virtually eliminates product slip since the pump’s ball check valves control fluid transfer.
4) Pump Construction
AODD pumps are available in a wide range of materials of construction. Common chemical-pump materials include polypropylene, Kynar®, stainless steel, ductile iron and Hastelloy, with some companies, like Wilden, able to offer special materials like super duplex when really unique materials are required.
If metal pumps are required, one overlooked material is ductile iron, which works well in both acidic and basic PH application ranges of 4 to 10. Provided that the chemical compatibility is correct, operators who use ductile-iron pumps can realize all of the benefits of stainless steel, but at a lower price point.
Conclusion
The design and operation of the AODD pump has proven to be able to meet the demands of chemical processors. The AODD pump, which possesses a stable of notable operational characteristics, has become a first-choice technology for chemical manufacturers who are searching for a pump that meshes cost-conscious air consumption with reliable and safe production rates.
About the Author:
Erik Solfelt is the Diaphragm Pump Product Manager for Wilden® and PSG®. He can be reached at (909) 422-1741 or [email protected]. Based in Grand Terrace, CA, USA, Wilden is the global leader in air-operated double-diaphragm (AODD) pumps and a product brand of PSG, a Dover company. Headquartered in Oakbrook Terrace, IL, USA, PSG is comprised of several of the world’s leading pump brands, including Abaque®, Almatec®, Blackmer®, Ebsray®, Finder, Griswold™, EnviroGear®, Mouvex®, Neptune™, Quattroflow™, RedScrew™ and Wilden®. For more information on Wilden or PSG, please go to wildenpump.com or psgdover.com.
This content is sponsored by Wilden. Sponsored content is authorized by the client and does not necessarily reflect the views of the Process Flow Network editorial team.
