Hygienic pump design

In this article, a glimpse of theory and basic information regarding the pump data assumptions, together with the hygienic features of its elements, has been considered. It has been stressed that the main criteria for the decision taken with respect to the practical application of the variety of hygienic pump types should be the result obtained after the microbial test given.

Do we have any definitions to describe the meaning of hygienic pumps, and what does this mean? The answer to both questions is no. Pumps in general refer to such devices in which the basic function is related to the effective medium transfer of either liquids or gases, based on the pressure value changes between the suction inlet inside, and pressure outside. The term ‘hygienic’ refers to the measurement of certain parameters related to the characteristics of the medium, and their quality and quantity features before entering the body pump and after leaving that body pump, in terms of any soil and contamination remaining on the internal surfaces.

Pumps design data assumption

All types of pumps and their functioning facilities can be built up and presented through the following scheme (Figure 1).

Pumps, like any other technical equipment, belong to and can be created based on the system design rules. Any technical system design is an interdisciplinary process influenced by basic knowledge of mathematics, physics, mechanics and thermodynamics. Furthermore, in the same process, the rules of manufacturing methods, material engineering, economy and cost ratio together with marketing and distribution strategies also should be taken into account. All the above-mentioned technical systems features have to be considered according to the relationship with the surroundings of the system as well. Every technical system can be described by the structural and functional relationship between parts within the design object. In accordance with such a description, a functional relationship means that the bonds of the system are placed in the target design area. A structural relationship indicates responsibility for the physical ties of all elements of the system and its exploitation facilities13,15. With respect to the definition, a pump system can be described by the following characteristics:

• A set of elements understood by designer intuition
• Elements chosen belonging to the certain type of pump system
• A relationship between sets of chosen elements
• Created pump structure, which means an exploitation order in relation to and between chosen elements
• Pump function value, meaning the describing changes of pressure between input and output inside the system at the range of expected capacity
• Surrounding conditions of the pump system – i.e., a set of other elements that do not belong to the system directly but can influence it in various ways

When looking at any pump operating system, it can be observed that within the parts of such a system, the following relationship exists: e →R →S →F →T. In other words, this means that the designer is facing the target (T) task in which the design pump should be verified, according to the set-up criteria. For instance high possible hygienic flow during the fill up of any package operation or in the brewery supporting cleaning and disinfection installation.

Usually, in the pump designing procedure, the following steps should be considered:

• By assumption, there are a set of elements that can make an entire domain {e}
• Regarding the target and chosen criteria, it is possible to describe the required relationship {RS} between the elements located in and taken out from the domain
• Based on the recognised RS, it is possible to set up the amount of elements {er} needed for pump design type
• The set of elements {er} makes the structure Sr of the designed pump system.
• The designed pump structure Sr is considered together with its facilities for all requirements as far as the function Fc of that system is concerned
• The function Fc achieved within the designed structure should have guarantee that all expected targets of such a system can be reached

It is obvious that one target can be characterised by many functions and realised through many design pump systems. For example, in the case of pumps placed in a pipeline installation, various valves there can play the same role in regards to the medium’s transportation, i.e., reducing the pressure, velocity or even closing the flow in that installation. The differences of these valves are due to the amount of elements to build up and to design a variety of types of them1,11,12. It also will be connected with relation to the kind of materials chosen, as well as the shape and geometry, to the finishing surfaces of their elements and their manufacturing and assembling.

Pumps hygienic level requirements

There are hundreds of pump types and thousands of equipment manufacturers. For instance: displacement pumps, reciprocating power pumps, direct acting steam pumps, rotary pumps with guided or swinging vanes, eccentric and circumferential piston pumps. Also, radial-plunge and swash-plate pumps, roots rotary lobe pumps, gear pumps, screw and double screw pumps, piston less pumps, nutating disc pumps, and many types of centrifugal and axial pumps. But not all of them have the same resulting exploitation parameters needed; ‘ready to use’ can be achieved and applied as hygienic pumps with necessary working conditions. It depends on the reference system described by the designer for all the pump elements, their quality as a whole and special attention paid to the surfaces in contact with the flowing medium. The optimal set of element features can be chosen for design systems regarding the following criteria: pump processing working conditions, material selection and its properties. Practically, it is related to an unlimited amount of questions the designer asks himself concerning the element form and shape. Also, their tensile strength, surface hardness, heat resistance, as well as the precision expressed by high accuracy to its roundness, cylindrical fit, surface roughness and other geometrical tolerances. When taken into account, the hygienic working conditions for all pumps applied especially to the food industry, the most important feature of their parts is the surface quality: for elements placed inside the pump body and remaining without movement, and also those located inside but with rotary or displacement movement. The final characteristics of these surfaces depend on several factors, namely, the treatment of machining, casting, welding and variety of finishing ways. All of these strongly influence the achievement of the internal and external elements surface picture. It also depends on other ways of lowering the final surface roughness after mechanical workings. Among others, it is known as surface coating process. Recently it has been performed by a method developed in Japan and applied mainly to pipe installation and to other industrial equipment. Based on that method, the value of surface roughness is the lowest, smoothness is the highest and the value of adhesive forces for some kinds of medium in contact is equal to zero.

Hygienic pumps are designed for application in special circumstances, such as baby food production, as well as for other applications that require a hygienically high standard that should be proved in open and closed equipment located at the food and medicine production plant. The specific surroundings influencing the application of hygienic pump conditions have been well published in New Food2,4,5,7,9,10,17 concerning the basic hygienic requirements at the above productivity area. It is pertinent to point out that the risk in changing food quality with possible contamination always occurs when pumps placed in the technological lines have to be cleaned. While other equipment operating on the same line is still used or contains an amount of raw material that can be further processed or has to be packed. Therefore, the hygienic pumps with such characteristics as reliable, easy to clean, with a quick dismantle design, with a surface polished finish to the lowest value of microns, and other exploitation abilities are preferable.

Conclusion

The correct hygienic pump design and manufacture, especially for the food, chemical and pharmaceutical industries can be found based on the correct relevant conflict solution. This conflict always exists between expected pump users due to requirements described in the UE Directive No. 178/2002 issued on 28 January 2002, regarding the rules for hygienic and safe food production, and manufacturers of the pump product should be in agreement with the UE Directive 42/2006 i.e., the new machinery standard issued on 26 June 2006.

The criteria on which the required inside surface feature elements remaining are based, without any movement as well as for outside surface feature elements left inside body pump as either rotary or displacement movement, should be the adhesive forces value rising from the type of fluid into both surfaces.

The adhesive forces value appearing between flowing fluid and surfaces should be decisive for reaction forces needed, and provided with the cleaning and disinfection method applied together with the process parameters of chemical agents used, based for example on the Sinners’ circle proportion (Time, Temperature, Chemical, Mechanical).

Based on the cleaning and disinfection method applied and its measurement results, a certain test adequate for hygienic pump classification has to be built up6, 8, 14, including description of product residues, accumulated areas and weak design places.

From the test results, there is the suggestion to follow into the better hygienic pump designing process with respect to the other higher hygienic level requirements expected and needed in the chosen industry processes3,16.

References

1. Cocker R., Hygienic design and assessment (Food Processing Valves), New Food, Issue 1, 2004, pp.8-14.
2. Duke M., The value of EHEDG, New Food, Issue 4, 2004, pp.8-12.
3. EHEDG Guidelines, Document17, 2nd Ed., Published by CCFRA Tech. Ltd. Chipping Campden, September 2004, pp.1-12.
4. Hygienic equipment design criteria, EHEDG Document 8, 2nd Ed., 2004.
5. Holah J., Designing a hygienic food factory, New Food, Issue 4, 2003, pp.9-13.
6. Jensen B.B.B., Friis A., Fluid flow in cleaning closed processes, New Food, Issue 1, 2006, pp.64-67.
7. Kastelein J., Cnossen H., Up to standard? New Food, Issue 4, 2005, pp.68-69.
8. Knudsen B., An Achilles’ heel for hygiene, New Food, Issue 1, 2006, pp.18-19.
9. Lelieveld H.L.M., The EHEDG certification scheme, New Food, Issue 3, 2001, pp.29-32.
10. Lorenzen K., Seals for safety, New Food, Issue 3, 2003, pp.46-48.
11. Lorenzen K., ECO-MATRIX: the efficient piping concept for Process Plants, New Food, Issue 1, 2007, p.15.
12. Majoor F., van Eijk H., Hygienic aspects of double seated valves, New Food, Issue 2, 2001, pp.29-33.
13. Matuszek T., Selected aspects of system design theory, Systems, 2003, Vol.8, No.2, pp.132-140.
14. Matuszek T., Olszewski H., Liquid energy analysis for the spray nozzle jet parameters optimisation, TASK, 1999, Vol.3, No.2, pp.227-237.
15. Matuszek T., Modular design process applied to the food industry, Scientific Papers, Bialystok University of Technology, No.7, 2000, pp.185-193 (in Polish).
16. Stahlkopf R., Efficient, hygienic pump design, New Food, Issue 3, 2003, pp.12-14.
17. Seward S., Sanitary design principles for meat processing, New Food, Issue 1, 2006, pp.54-58.