Pumps are a vital part of many dairy processing facilities, but it is important to select the correct pump for both the product (for example, creams might have different requirements than fruit purees) and the process. Physical damage due to factors such as pressure and shear stress must be avoided, and if you need to pump large solid items such as fruits or curds, then more complex challenges are presented.

There are many types of pumps on the market, including rotary lobe, rotary piston, reciprocating positive-displacement, progressing cavity, peristaltic hose and air-operated double-diaphragm designs. Each type has its own advantages and disadvantages, and some are more suitable for certain applications.

Not all of these various designs can maintain product quality at a reasonable cost while at the same time keeping the required pressure in the system. For example, progressive cavity pumps, in particular, can break the product, while double diaphragm pumps result in a low pressure drop. Another issue is that traditional pumps can be expensive to maintain, while lobe pumps have low flow rates.

If you are not careful, the wrong pump can easily turn your delicate cream product into curds and whey or butter. At the same time, pumping thicker materials requires care to prevent them from de-homogenizing or splitting.

Overcoming the issues

One pump design that overcomes many of these difficulties is the hygienic reciprocating, positive-displacement pump. These pumps are suitable for a wide range of difficult-to-handle food products, including whole fruits, curds, sauces, fruit purées, creams, custards, etc.

Positive-displacement pumps have an expanding cavity on the suction side of the pump and a decreasing cavity on the discharge side. Liquid flows into the pump as the cavity on the suction side expands and is forced out of the discharge side as the cavity collapses. The best hygienic designs for food industry use are operated either hydraulically or pneumatically and incorporate separators between the piston and the hydraulic chamber to ensure there is no contact between the product chamber and hydraulic oil.

Other advantages of positive-displacement pumps are variable flow rates, typically between 52 gallons/hour and 3,170 gallons/hour, and the ability to maintain high pressure drops of up to 435 psi bar. This makes them suitable for a wide range of high-viscosity, shear-sensitive and large-particle-containing fluids such as creams and fruit mixes. The fitting of clap valves allows you to pump whole fruits or other large pieces.

If you have experienced product issues using other pumps, then it is quite possible that positive-displacement pumps will be able to meet the challenge, whether you are handling whole fruits, delicate dairy products such as creams and sauces, highly viscous materials such as custards, or larger particles as those found in fruit compotes.