Look behind the scenes
Displacement pumps are often used in food production where viscous or difficult media such as molasses, honey, spent grains from beer brewing or chocolate have to be conveyed. These media has to be handled in part very sensitively. Progressing cavity pumps are particularly good for these tasks as they ensure conveying at stable pressure and volume, are gentle on the product and allow high-precision dosing. Despite the benefits in handling such media, progressing cavity pumps have the reputation of being only of limited suitability for tasks with product contact in the food industry. The main concerns regard the latent risk of food contamination through rubber abrasion.
It is correct that important components of progressing cavity pumps, such as stators and seals, are made primarily from elastomers, i.e. from elastic natural or synthetic substances. Constant wear occurs due to the friction between the rotor and the stator elastomer, depending on the conveyed medium, especially for highly abrasive media, but those are rather seldom in the food industry. But even for those rare media there are hygienic progressing cavity pumps available, where only a very low level of abrasion occurs when properly used. In an internal risk assessment conducted on individual pumps, the rubber removed through abrasion was put into relation with the expected total pumped volume during the entire stator operating time. The impurity caused by the elastomers is minimal with a single-figure ppb value and an unacceptable change in the composition of the conveyed medium can therefore be excluded. Accordingly, we will use obviously only food-safe elastomer.
Specific hygienic progressing cavity pumps which are intended for hygienic critical applications fulfil a whole range of hygiene regulations – from EHEDG and the 3-D Sanitary Standard to the requirements of the US Food and Drug Administration (FDA). The food compatibility of the installed materials and the cleanability of the design lie at the heart of all these regulations. Conventional progressing cavity pumps are therefore adapted for use in hygienically sensitive areas. To ensure that they can be used in the food industry without risks, the elastomer used is specially selected for food contact. For the food applications, compounds are selected which have good wear resistance, comply with FDA regulations and Regulation (EC) no. 1935/2004 and do not affect consumers’ health.