18.1 Introduction: types of pump used in food processing
In automated food processing technology, pumps are used for the transport and
the increase of pressure of low-viscosity, liquid products. To ensure a hygienic-
ally and microbiologically perfect condition of the product, high standards are
applied to turbo machines and positive displacement pumps with regard to
hygiene and cleaning technological requirements. These standards apply to all
pumps used in the food processing industry, including centrifugal pumps, piston
pumps, rotary pumps, peristaltic pumps, diaphragm pumps, water ring pumps,
positive-displacement pumps, screw pumps, gear pumps as well as to homo-
genisers, dampening devices and finally all valves integrated in the pump body.
Concerning centrifugal pumps, it is common practice to flange the pump
directly to the motor. This has the advantage of a more compact pump design.
Open couplings as used in the conventional pump design where the motor is
mounted on a ground plate are not needed. If motors with special shafts are used,
the impeller is plugged on to the motor shaft or the pump shaft is plugged on to
the motor shaft of a standard motor (Fig. 18.1). In this case, depending on the
pump size and/or axial forces, reinforced bearings, integrated bearing flanges
and measures against axial thrust are required.
18.2 Components usedin pumps
18.2.1 Impeller
Open impellers without a front cover plate are generally used on centrifugal
pumps. The advantage is an easier manufacture of the impeller (Figs 18.2 and
18.3). The impeller blades are mechanically accessible and can be treated to
18 Improvingthe hygienicdesign of pumps
R. Stahlkopf, Tuchenhagen GmbH, Germany