Diaphragm Pumps

The Arrival of Diaphragm Pumps as Mainstream Process Pumps

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This trend can be commonly seen. One hygienic sub-segment in which the switch from simply being an unloading pump to a mainstream process pump is very visible is the personal-care/cosmetic industry. Plants with a preponderance of diaphragm pumps in operation are to be found from large multinationals to smaller co-packers. This is especially true in formulation and filling lines that are able to take full advantage of the air-diaphragm pump’s very flexible viscosity, suction and flow operating characteristics. Of course, if an application has needs that cannot be met by a diaphragm pump, such as flow regime, flow rate or discharge pressure, then a suitable pump for these situations is needed.

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Some traditionalists will write off the use of an air-diaphragm pump because of the fact that it is powered by air. This stance needs further consideration because the very fact that the pump runs on air that is compressible gives these pumps some process-friendly capabilities that are not achievable by other pumps. For example, enabling production of a product with less thickener since the thickener is not damaged by shear in a pump may trump simple energy usage in value between pumps. Let’s examine these capabilities:

Deadhead Capability

These pumps can easily and automatically achieve a deadhead condition by simply adjusting the air pressure to match the system’s maximum desired deadhead pressure. This is possible without introducing heat or shear to the product, which is a key need in the production process for many hygienic products, such as pumping yeast (live cells) or expensive skin creams. The only other mainstream pump class that can be deadheaded (somewhat) is the centrifugal pump, but these pumps quickly generate considerable heat and shear in deadhead operating conditions and are not a suitable option.

Examples of the benefits of deadhead capability can be found industry-wide beyond the simple protection against broken pump shafts and burst piping. They include:

Certain filter-feeding processes: Certain filters, such as the filter presses found in beverage plants, operate at an ideal pressure to maximize the filtration process. The goal here is that as the filter gets loaded during the process, the operating pressure cannot be exceeded. If it is, the material that is retained in the filter, termed “breaking the filter cake” in the industry, can be pushed through to contaminate the end-product. Such an event is costly. Air diaphragm pumps are a simple safeguard against this.

Filler-feed processes: Certain filler technologies need a stuffing pressure, for example, to feed a volumetric cylinder that later pushes product into the container. The air-diaphragm pump does just that. It charges the system to the desired pressure so when the filler cylinder’s channel opens, product flows in. When it is closed, such as during the container-dispensing process, the diaphragm pump keeps the line pressurized to react quickly during the next opening. If it were not for the air-diaphragm pump, complex control loops with sensors, valves, drive control and automation would be needed. A prominent shaving-cream company did just that replacing a complex pump and pressure control system with a simplified and reliable diaphragm pump charging/feed system for greatly improved reliability and yield.

Shear-sensitive applications benefit even further when fed by air-diaphragm pumps. Two different U.S.-based multinationals that produce personal-care products know this. In one case, problems were experienced with lobe pumps that were causing shearing in the shampoo, which produced foam in the beginning of the production process. The incorporation of air-operated diaphragm pumps both increased the accuracy of the fill with proper feed and also eliminated the foaming issues at startup.

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