Hygienic pumps are utilised everywhere when it is necessary to convey sensitive products which must not be contaminated by germs or also by residues. This is especially the case in the food and beverage industries. However pharmaceutical processes and specific industrial applications also require hygienic pumps.
Specific requirements in terms of materials, the surface quality finish and cleanability also have to be complied with in the case of hygienic pumps. The nomenclature is not therefore uniform. While one talks about hygiene pumps and/or hygienic pumps in Europe, the US-American market refers to "Sanitary Pumps". A parallel utilisation of this terminology will not be accepted in this case.
Organisations such as the EHEDG or 3A Sanitary Standards Inc. analyse hygienic pumps and other equipment facilities for their suitability. EHEDG and 3A Certificates are therefore an indicator of a professional design for hygienic pumps. The procedures of the organisations however vary. EHEDG Certificates are based on empirical findings from experiments, while 3A Certificates are based on a detailed analysis of the design documentation. Hygienic pumps are normally produced from stainless steel of quality 1.4404 (316L). For aggressive media, there are also higher-grade stainless steels such as 1.4539 or also duplex grades can be considered.
The objective for a hygienic pump is that the conveyed media is not contaminated during transport. Therefore, on the one hand it must be ensured that residues cannot easily adhere in the pump and, on the other hand, that these must be simply and fundamentally removed as easily as possible. Hygienic pumps display a high surface quality. Normally, the roughness will be approximately 0.8 µm.
For particularly sensitive products in the pharmaceutical industry, even higher demands are made and the roughness is required to be less than 0.4 µm. The smooth surfaces prevent the formation of deposits and facilitate easy cleaning. Hygienic pumps must be cleaned at regular intervals. Typically, this occurs in the system in the installed condition. In this case, one speaks about a CIP cleaning, CIP = cleaning in place.
Cleaning is performed with highly tempered lye and acid as well as with rinsing, which is conducted in larger quantities to achieve minimum speeds for safer cleaning through the system. All components must be available. The pumps must therefore be executed as a cavity-free design. HYGHSPIN twin screw pumps provide particular advantages in terms of cleaning. They are not only free of cavities and therefore can be cleaned as CIP but they can also be utilised as a CIP conveying pump. This means that an additional CIP pump, switching valves and controls can be omitted from the system. The costs and the risk of a system failure therefore decrease accordingly.
Many details have to be considered for hygienic pumps. Therefore suitable certified materials have to be utilised for the elastomer and the thermal expansion has to be considered. For the HYGHSPIN twin screw pumps, form rings are utilised for static seals to exclude product embedding in the grooves due to thermal expansion.
In addition to cleaning, hygienic pumps are regularly sterilised in the system for aseptic applications. In these cases, one speaks of SIP = sterilisation in place. Superheated steam of 130°C-145°C kills the germs and provides the aseptic condition safely.