Hygienic design of equipment for open processing
Belts in contact with food are used for conveying or inspection of product. Embedded
reinforcements as well as fabric backing materials must be covered to avoid contact with the
product (Fig. 17). Cut edges of belts with reinforcing materials must be seaied to prevent
penetration (wicking) of liquids into the interior. The whole of the belt must be accessible for
Fig. 17: Reinforcement of belts. (a) Open edges of belts with reinforcements cause hazards by crevices orpenetration
(wicking) of liquids; (b) reinforcing materials must be covered at edges of belts.
The belt edges can be supported by removable and easily cleanable covers (see Fig. 18). The
design of Fig. 19 shows an example of overhanging belt edges and a quick tension release
arrangement for cleaning the belt. The belt can be lifted, plastic tubes are then inserted and the
area between support construction and the belt can be cleaned easily.
Fig. 18: Sides of conveyor belts. (a) Non removable bearing sulfaces for belts and covers as well as hinges of pivoted
covers cannoz be cleaned easily; (b) cover which can be removed for cleaning must be preferred.
Fig. 19: Special belt design using swivel mounted rollers facilitates cleaning by releasing the tension of the belt to
give space between belt and bearing table.
Gears and motors of belt drives must be covered to avoid any contamination of product (Fig. 20).
The design of rollers must avoid dead spaces where product can be retained (Fig. 21). Welded
construction should be preferred to sealed design.
Fig. 20: Covered drives for belts. (a) To avoid any hygiene risk drives of belts must be covered and the belt should be
clear of franiework for cleaning; (b) sealed casing for drive, appendages and framework gives open access to belt and
Fig. 21: Design of rollers. (a) Sides of rollers which are not aligned and srnooth cause dead areas and crevices; (b)
aligned front sides which are properly welded to the d e r and to the shaft avoid any hazard and can be cleaned
Mesh, screens, gridirons, perforated sheets.
Mesh, screens, grids, or perforated sheets should be avoided in the product area. The application
e.g. for guarding or processes like sieving and drying requires particular attention to ensure
cleanability. Special, fully (vacuum) welded, gridirons are available avoiding any dead areas..
Non food contact equipment
The main aspect of hygienic design of non food contact equipment for open processes is to avoid
accumulation of soil, microorganisms, insects and other vermin in difficult to clean or uncleanable
areas and surfaces.
Materials and Surfaces
Materials for non food contact surfaces must be easily cleanable and resistant to the product and to
cleaning and disinfecting agents. Dissimilar metals in contact must be avoided by reason of
contact corrosion. For the non food area, stainless steel is to be preferred. If components are
coated (e.g. rnotors, drives, casings) the coating must be non toxic and resistant to cracking,
chipping or flaking. Coated components should not be positioned directly above open product
areas. Insulation must be vapour tight to avoid growth of microorganisms.
Cladding of equipment must be smooth, continuous and without crevices to ensure that it is easily
cleanable. Ledges, projections and pockets must be avoided because they retaîn soil. If
unavoidable, horizontal ledges and projections should be sloped (Fig. 22). A minimum slope of 30"
is required to avoid accumulation of dust and to facilitate inspection. Cladding must be installed
such that a minimum clearance of 30cm is maintained between adjacent surfaces.
Fig. 22: Cladding offrmwork.
(a) Horizontal ledges,
projections and fiaines retain
soil; (b) to avoid accumulation
of dust and for drainage
horizontal parts must be sloped.
Un-clad framework should preferably be constructed from hollow square or round section
members. Open ends of such framework must be closed by welded ends or plastic caps. For the
design of framework that will be exposed to continuous vibrations (eg drying towers etc.) the use
of open profile construction should be considered. Small cracks can aise from vibration allowing
penetration of moisture, soil and microorganisms in closed profiles. For vertical parts of frames al1
cross-sections shown in Fig. 23 can be used. To avoid soil trapped on the horizontal surfaces of
frames open and closed cross-sections must be self draining and easily cleanable. Horizontal
mounted cross-sections and framework should be designed as shown in Fig. 23 b and Fig. 24.
Fig. 23: Cross-sections of un-cladframework (a) Ledges of cross-sections harbour residues of soil when mounted
horizontally; (b) closed or open cross-sections must be used in such a way that soil cannot accumulate.
Fig. 24: Horizontal framework. (a) Horizontal ledges of open or closed cross-sections of framework must be avoided;
(b) for horizontal framework open or closed cross-sections must be used in a way to ensure self draining.
Where support structures of equipment are attached to the floor or to walls either a minimum
clearance for cleaning and inspection must be applied or the equipment must be properly sealed
against the mounting surface (Fig. 25, Fig. 26). Care must be taken to avoid gaps, cracks or
crevices where microorganisms or insects can remaidsurvive after cleaning.
Fig. 5: Equipmentfixed tojïoors. (a) ,.rderneath equipment, with a small clearance to thefïool; cleaning will be
complicated; in addition, not radiussed and improperly Bed feet, sharp corners and crevices at the focing point cause
hygiene risks; (6) feet properly fSxed to rounded pedestals or (c) sealed to the floor with suficient clearance
characterize hygienic design.
Fig. 26: Equipmentfilced to walls. (a), (6) Horizontal suflaces or ledges retain soi1 and small clearances hamper
cleaning between walls and equipment; (c) horizontal supports of equipment (see also fig. 24) must be radiussed and
properly fmed to the Wall considering suficient clearance; (d) equipment can also be directly fixed to the Wall and
seaiing materials applied.
Equipment must be accessible for inspection and maintenance (Fig. 27). Increased elevation of
tanks and vessels facilitates cleaning operations beneath the equipment S. Water and condensation
running down the equipment Wall may result in a hazard to motors and electrical parts.
Fig. 27: Accessibility of equipment. (a) Equipment must not be mounted beneath tanks or vessels so that maintenance
and cleaning are not possible; (6) accessible equipment can easily be maintained and gives open space for handling
and cleaning beneath tanks with suficient clearance.
Raised walkways or stairs over any exposed product should be avoided because dirt may be
transferred from clothing or footwear ont0 product lines beneath. If personnel movement is
required in these areas, the equipment should be constructed to be fully enclosed. Kick-plates
should be designed as a one-piece construction. The decking should be constructed from solid
plates containing a raised anti-slip surface. Risers of staircases must be encased. Steps should be
constructed of the same anti-slip material .as the deck. The use of expanded metal or mesh must be
avoided to prevent soi1 being transferred into the product ( Fig. 28).
Fig. 28: Walkways over exposed product. (a) Raised walkways over product areas cause hazards by contamination
from employees; (b) ifwalkways are not avoidable they must be designed to bejùlly enclosed.