Why hygienic design is essential

Hygienic pump design is the alpha and omega of any successful sanitary production process. Hygienic design implies that the pump is easy to clean and thus is made of materials and components which comply with strict international standards for sanitary applications.

In a number of industries, including food and beverage and pharmaceutical industries, high-grade sanitary pumps play an important role in the production process. If the pump does not live up to the high requirements with regard to safety, design, materials used and material surface finish, this can lead to impurities in the system, potentially causing an entire production to be brought to an immediate standstill.

So, cleanability is the essence in any sanitary pump. The most important criterion for the cleanability is primarily an optimum hygienic pump construction that is easy to clean. The circulation space should be free of dead ends.

Unique hygienic design

Because quick and efficient cleanability plays such a decisive role in sanitary processes and thus in sanitary pumps, higher safety standards apply for these types of applications than for other processes involving pumps. The Grundfos range of sanitary pumps, designed by Hilge, is made in accordance with the strictest hygienic design criteria both for physical properties and with regard to preventing possible breeding grounds for bacteria and germs.

The design requirements and the surface finish of the materials used are of the utmost importance and subject to a wide variety of national and international rules and regulations. Among these are the GMP Rules and Regulations, FDA Regulations, 3A Sanitary Standard, EU Foodstuff Hygienic Guidelines, DIN EN 12462 Biotechnology, the recommendations of the EHEDG (European Hygienic Equipment Design Group) and QHD (Qualified Hygienic Design).

Materials

Strict requirements to hygienic design mean strict requirements to construction of any component that comes in contact with the pumped liquid. Therefore, the selection of materials and their surfaces with regard to cleaning and corrosion characteristics plays an important part when it comes to quality and safety of the entire process.

Different factors need to be considered in order to determine these requirements: product safety, consumer protection, reducing cleaning costs with regard to economic and ecological aspects, and legal requirements related to ease of cleaning, etc.

Depending on whether the pump is to be used in, for example, the pharmaceutical or food and beverage industry, it is important to specify these requirements in order to get the most suitable pump for the task at hand.

To ensure a homogeneous pore-free surface of the sanitary pumps, Grundfos uses AISI 316L (DIN EN 1.4404/1.4435) cold-rolled and/or forged stainless steel for sanitary pump construction.

Shaft seals

Hygienic design also calls for high requirements with regard to the seal arrangement. Sealing surfaces must be free of gaps, the contact pressure of sealing materials must be well defined and a hygienic, certified shaft passage or seal must be used. Depending on the requirements, the shaft passage or seal can be located either internally or externally in a single or double arrangement with a connection for flushing water.

To ensure trouble-free operation, no matter the application and the pumped liquid, two main types of shaft seal exist: single and double mechanical shaft seal arrangements.

The single shaft seals are inboard mechanical seals with an optimum position in the pumped liquid in order to ensure lubrication and cooling as well as CIP (cleaning-in-place) and SIP (sterilisation-in-place). The double seal arrangements are either a tandem or back-to-back seal arrangement. All standard seals in the Grundfos sanitary range have seal faces of carbon/stainless steel and O-rings of EPDM (ethylene propylene diene M-class rubber). Other seal face material combinations are available, such as SiC/SiC (silicon carbide/silicon carbide) for pharmaceutical and biotech applications.

Depending on the user’s requirements, Grundfos offers two types of shaft seals for hygienic applications and sterile applications. As standard for hygienic applications, Grundfos offers a single shaft seal fitted with a metal spring as seal driver. This shaft seal has seal faces of carbon/stainless steel and O-rings of either EPDM or FKM (fluoroelastomers). As standard for sterile applications, Grundfos offers a 100% encapsulated shaft seal. In this case the shaft seal has seal faces of SiC/SiC and O-rings of EPDM or optionally FFKM (perfluoroelastomers) or FKM (white).

Impeller types and connections

To meet the different and high demands of the pharmaceutical, food and beverage industries, Grundfos has developed a range of surface finishes designed for specific industries. Impellers and connections are designed and treated in different ways according to international standards in order to handle the pumping task in the best possible manner.

All the impellers for the Grundfos sanitary range are electropolished stainless steel impellers and are available in different types of design: semi-open impeller, closed impeller and free-flow impeller designs. Each type is capable of handling a wide range of pumping tasks, such as different viscosity liquids and liquids with a variable content of solids. For pharmaceutical applications where it is a requirement that the surface finish Ra<= 0.8/0.4 μm only semi-open impellers are used. However, channel impellers are available on request.

Connections are also subject to different hygienic designs and thus to a wide range of standards. Sterile threads are designed according to DIN 11864-1 PN 16 and sterile flanges according to DIN 11864-2 PN 16. Grundfos also offers a whole range of special connections for special applications such as SMS, RJT, DIN or ISO clamp connections, Tri-Clover connections and ASME BPE 2000.

Approvals and certificates

Grundfos wants to protect users’ consumable products from contamination and to make sure that their production is safe and lives up to the strict international requirements with regard to hygienic design. The design, materials used and surface finish are subject to a variety of national and international rules and regulations. All the products in the Grundfos high-grade sanitary range comply with the strict requirements as to hygienic design listed in the 3A Sanitary Standard, the EHEDG and QHD.

In addition, a number of special certificates and approvals are available for different purposes such as material certificates and ATEX approved sanitary pumps which have to be ordered with the pump. Customers who require absolute certainty that the delivered Grundfos product complies with the specifications of the order as to surface roughness, for example, can order a certificate on request. This means that if the pump is to be installed in explosive atmosphere, an ATEX- EC Conformity Declaration must be delivered together with the pump.