Air-operated double diaphragm pumps for all reasons

Paul Boughton

Air-operated double diaphragm pumps are suitable for demanding applications in chemical, pharmaceutical, coatings, paint, sanitary and food

The use of air-operated double diaphragm (AODD) pumps in the process industry is steadily growing in popularity. This is even more evidentin the chemical industry.

Crane ChemPharma and Energy's DEPA brand of AODD pumps are designed to satisfy performance requirements in a wide range of demanding applications found in chemical, pharmaceutical, coatings, paint, sanitary, food and many other process industries.

Available in cast metal, stainless steel, non-metallic, and PTFE construction materials, they provide reliable and efficient control for conveying liquid and shear-sensitive materials.

DEPA pumps can also handle viscous and abrasive media, and operate in other 'aggressive' environments and extremely demanding applications. Based on a flexible and modular design, DEPA pumps are available in a broad range of sizes and specifications, limiting the need for extensive spare parts inventories due to interchangeability of components.

With its ATEX certified for Zone 0 (Group II 1 G), Crane’s  AODD pumps product suit applications in potentially hazardous and explosive environments.

Crane pioneered its 'nopped' surface diaphragm, which utilises a uniform sequence of small mounds radiating in a band located medially within the diaphragm, creating turbulent boundary layers which in turn results in advantageous flow conditions (similar to the effect of golf ball dimples)  and consequently improving energy efficiency.

The ‘nopped’ surface also makes the diaphragm much more flexible than standard rubber diaphragms.

Available in four sizes, ranging from 1/2-in-2-in, the diaphragm combines versatility and functionality, and is constructed as a single unit from a combination of PTFE and EDPM, coming into contact with liquid and air respectively. The outer piston, usually a separate component in standard pumps, is entirely encapsulated. In addition, EDPM is electrically conductive, which makes it suitable for use in ATEX-conforming pumps, and the diaphragm is approved for use in Zone 0 when used in conjunction with pumps made of stainless steel casting. [Page Break]

The increased flexibility enables greater flow rates combined with reduced air consumption, resulting in energy savings. The flexible nature of the DEPA E4 Compound diaphragm gives it a longer life-span while by that very fact increases the length of replacement intervals (reducing replacement frequency), which generates savings in both operation and maintenance, while decreasing down-time.

The diaphragm can be installed and replaced easily due to its single-unit construction and is compliant with CE markings.

The laminated design ensures the diaphragm surface is impermeable. This facilitates greater safety and an ultra-clean working mechanism, which prevents leaks/deposits and greatly limits areas for bacteria build-up whilst the high chemical resistance is maintained right through the entire pH range (0-14) against most media.
This year DEPA launched the S4 Diaphragm - a versatile, state of the art industry solution. Its enhanced flexibility and resistance to abrasion are a result of this surface design in combination with the use of Santoprene as its core material, a substance combining rubber polymer (EPDM) and polypropylene.

Santoprene, a registered trademark of Exxon Mobil, offers resistance to mild acids, as well as some solvents and bases, and contributes to a long lifetime in cold and warm environments. The resulting efficiency and reliability of the S4 Diaphragm saves on energy and time costs, respectively.

The DEPA S4 Diaphragm is in compliance with Machinery Directive 2006/42/EC. It can operate within a temperature range of -4°F to 230°F (-20°C to 110°C), and a maximum 7 bar operating pressure.

Crane also enhanced its product range with the development of the DEPA AirSave System, which improves energy efficiency and service life of the pump. The system operates with virtually no leakage at a low start up pressure, and provides lower costs of operation, while enablieng ease of service and maintenance. The DEPA AirSave System is available for a broad range of applications and pump sizes.

Crane additionally designs and manufactures the ELRO range of peristaltic pumps for mobile and industrial applications, which are regarded as indispensable in the positive displacement pumps market, serving industries such as chemical, building, environmental and power. These pumps can transfer all kinds of abrasive, viscose and shear-sensitive media and are also suitable for potentially hazardous environments. When installed or portable units, ELRO pumps provide easy operation and servicing, with only one item to wear out.

Both DEPA and ELRO pumps are distributed in the UK by Teesside-based Tomlinson Hall.

Crane ChemPharma Flow Solutions is based in Düsseldorf, Germany.