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FEET

Feet begin at the point where they attach to the leg or the body of the equipment and end at the support point on the floor. These feet are indirect- product contact surfaces but have a hygienic significance because they may become a harborage of soil and create a source of secondary contamination to the products (e.g., during high-pressure cleaning of equipment and especially floors, and dirt present on the feet may splash on the food contact surfaces).

Use a minimum number of support legs/floor mountings, because they are important obstacles for cleaning and service personnel. However, feet must be sufficient in number and strength and so spaced that the equipment

If the equipment is heavy, the contact face of the foot

FIGURE 6.22 If the equipment is heavy, the contact face of the foot (2) with the floor (1) must be sufficient to absorb the pressure. To distribute the load, feet should be provided with a footplate (4) welded to the foot leg (3). The foot may be fastened to the floor by means of (a) stainless steel anchor bolt(s) (5) which must have (a) seal washer(s) (6) and (a) dome nut(s) (7) fitted. When the equipment must be bolted to the floor, floorplates shall be sealed with polymer material (e.g., epoxy) to the floor (figure left, 8). The bolting hole(s) must be sealed so that water and dirt are not allowed to leak into the hole(s). Grouting with concrete (figure right, 8') is not recommended (Moerman & Kastelein, 2014).

will be adequately supported. The general rule is to minimize the floor contact area, but the contact face of the foot must be sufficient to absorb the pressure of the equipment. Skid-proof antislip feet or feet with a footplate fastened to the floor can be used. The latter are applied when the load of heavy equipment must be distributed over a larger surface of contact with the floor. When anchored to the floor, the equipment can’t move from its designated position during operation. However, it is better to avoid fastening to the floor because of hygiene issues. The manner in which feet are fastened to the floor depends on the type of floor and the presence of equipment (e.g., machinery producing heat) or services (e.g., electricity) immediately below the surface. When the process equipment must be bolted to the floor requiring floor slab penetration, footplates shall be additionally sealed to the floor with polymer material (e.g., epoxy) (Fig. 6.22 left and Fig. 6.23). Grouting with concrete (Fig. 6.22, right) is not recommended, as practice in the food industry has proven that the concrete grouting can break, allowing food residue to accumulate and bacteria to find a niche in the cracks and crevices of the concrete. Chemical anchors without bolting (fixing to floors by means of a polymer seal) are more recommended. Care must be taken during installation to assure that the footplate does not span over cracks, grout lines, or other floor imperfections.

The footbase of foot ends may either have flat (not recommended) or sloped (recommended) surfaces. Provide only fixing holes where bolting to the floor is necessary, and avoid the use of extra brackets. Avoid all unnecessary (sharp) corners and edges, as well as crevices at the fixing point. When installed on the

By anchoring the process equipment to the floor, it cannot move from its designated position during operation

FIGURE 6.23 By anchoring the process equipment to the floor, it cannot move from its designated position during operation. Foot anchors should be polymer sealed into the floor. Grouting foot anchors into a concrete floor may give rise to unhygienic conditions with time. Courtesy of Surface Solutions, Inc.

The foot has plenty of pits, folds and other imperfections where dirt and liquids may build up

FIGURE 6.24 The foot has plenty of pits, folds and other imperfections where dirt and liquids may build up. In particular the exposed treads, bolt nuts and washers create a lot of crevices. The footbase forms a difficult-to-drain flat surface, and dirt and water may penetrate under the footplate. In this manner, they form a niche where microorganisms may grow. Photo left, courtesy of Mondelez International, 2016; photo right, American Meat Institute, © 2016.

machinery and within the specified load conditions, all exposed surfaces shall be free of pits, folds, cracks, crevices, and other imperfections in the final fabricated form. A smooth finish is required such that soil may be cleaned from the surface using manual cleaning techniques. Several examples of nonhygienically designed feet are shown in Figs. 6.24 and 6.25.

Equipment should be adequately located in position, with all its feet having a contact face that is even, so as to ensure complete contact with or to allow fixation to the floor. Where the floor is flat, hygienic nonadjustable feet can be used (Figs. 6.26 and 6.27).

Foot ends with a flat footbase

FIGURE 6.25 Foot ends with a flat footbase (footplate) are not recommended. The use of a bush (welded to a footplate, and either open or closed) to insert the legs of the equipment or the foot spindle is a proof of bad hygienic design practice because debris and water may collect into the bush (A & B). Welds to fix the equipment leg or foot spindle onto the foot base must be smooth, without pits and folds where dirt and liquids may build up (C & D). Holes in the footplate should be omitted where bolting to the floor is not necessary. Exposed threads such as threaded foot spindles (B) and bolting screws without dome nut (C, D) are not allowed. Countersunk screws with slots or other drive configurations (A) and bolts with flat hexagon bolt heads (B) are not recommended. Bolts with hexagon dome nuts and seal washers must be used instead of flat open hexagon nuts (D). Because the footplate is not provided with an antislip rubber pad or polymer sealed onto the floor, dirt and water may penetrate under the footplate, forming a niche where microorganisms may grow. Concrete pads should not be used, as the concrete may crack (D).

Nonadjustable feet with sloped surfaces, rounded corners and smooth welds for maximum drainability should be used (APV Baker, 2001)

FIGURE 6.26 Nonadjustable feet with sloped surfaces, rounded corners and smooth welds for maximum drainability should be used (APV Baker, 2001).

(A) Foot with a smooth radiused leg-footbase transition (Frank Moerman

FIGURE 6.27 (A) Foot with a smooth radiused leg-footbase transition (Frank Moerman,

© 2016). (B) Foot radiused down to the foot base. (C) Foot spindle smoothly welded to the footplate and the hermetically closed leg. Photo right, courtesy of Joe Stout, Commercial Food Sanitation LLC - Intralox, © 2016.

Ball feet with the threaded surface covered by an adjustable sleeve

FIGURE 6.28 Ball feet with the threaded surface covered by an adjustable sleeve (A) and other foot designs without threads (B & C) provide easily cleanable designs. However, mechanically they will almost destroy the floor, because they exert a (very) high pressure locally, especially if they are used to support heavy equipment prone to vibration/oscillatory movement. Ball feet should only be used to support low-weight equipment. Photo left, courtesy of Koss Industrial, Inc.

Notice that ball feet (Fig. 6.28A & B) or other foot designs exerting high punctual loads on the floor (Fig. 6.28C) are not recommended. They leave uncleanable crevices between the floor and the foot. Moreover, mechanically they will almost destroy the floor, because—due to their very small contact surface with the floor—they exert a very high pressure locally. If the process equipment is heavy and prone to vibration, the floor will break up very quickly.

Foot ends with a ball-socket arrangement (Figs. 6.29 and 6.30) have a spindle with ball end that may freely swivel in a socket or internal cavity of

Hygienic adjustable equipment feet admitting slopes up to 10 degrees on floors

FIGURE 6.29 Hygienic adjustable equipment feet admitting slopes up to 10 degrees on floors. Footbase and spindle are two separate entities. The ball-end of the spindle (1) fits in the diametrically centered depression (socket or internal cavity) (2) in the footbase. The gasket (3) at the junction between the foot spindle and footbase plate (ball-socket joint) prevents any dirt from entering the socket or internal cavity. The adjustment sleeve (4) which covers the threaded surface also functions as a nut. O-rings (5) inserted inside the adjustment sleeve at both ends prevent dirt from entering the thread.

Heavy-duty adjustable feet with the threaded spindle completely covered by a sleeve provided with O-rings

FIGURE 6.30 Heavy-duty adjustable feet with the threaded spindle completely covered by a sleeve provided with O-rings. By adhering to the smooth surface of the screw, this gasket prohibits any intrusion of dirt. Where required, the spindle can be welded to the footplate to avoid liquids or product residues from gathering in the hole in the footplate. Photo left, courtesy of Martin S.R.L., photo right, courtesy of NGIA/S.

a separate load-bearing footbase. Such a design provides stability under load (the load is evenly distributed about the entire spherical surface of the socket), as well as vibration/oscillatory movement absorption capacity and the ability to support the equipment on an uneven floor. To prevent any dirt from entering the socket or internal cavity of the load-bearing footbase, a rubber gasket at the junction of the footbase with the spindle (ball-socket joint) is essential. In other designs, the foot spindle has a concave end which can swivel over a diametrically centered convex elevation in the load-bearing footbase plate (Fig. 6.31). An O-ring fitted in the concave spindle end must prevent access of impurities, filth or bacteria in the joint. The load-bearing

Hygienic adjustable equipment feet admitting slopes up to 15 degrees on floors

FIGURE 6.31 Hygienic adjustable equipment feet admitting slopes up to 15 degrees on floors. Footbase plate and spindle are two separate entities. The concave end of the spindle fits in a diametrically centered elevation of the footbase plate, having the form of a spherical dome. An O-ring fitted in the concave spindle end must prevent access of impurities, filth or bacteria in the joint. The adjustment sleeve covers the threaded surface, and at the same time functions as a nut. The O-rings inserted inside the adjustment sleeve adhere tightly to the smooth surface of the screw, and prevent dirt from entering the thread section. Courtesy of NGIA/S.

foot may also include a rubber layer underneath or rubber can be embedded in the load-bearing foot. The elastomeric material may dampen the vibrations of the operating equipment and may prevent slipping of the foot on the support surface. The rubber pad may also prevent liquids and dirt from getting under the footbase due to the fact that the rubber compensates for the roughness and irregularities of the floor. A sufficiently low Durometer rubber provides a tight continuous seal with the flooring material.

For proper installation on uneven or inclined floors, it is not allowed to level food processing equipment with improvised shimming either with metal sheet (Fig. 6.32A) or a wooden plank (Fig. 6.32B). Equipment feet adjustable by min. ± 75 mm should be used. Adjustable feet may not leave (threads) (Fig. 6.33). When adjustable feet are used, the threaded spindle for leveling should be completely concealed in closed profiles/pipes (Fig. 6.34) or enclosed by a sleeve (Figs. 6.29—6.31), so as not to cause accumulation of dirt or contaminants in the thread and to facilitate the cleaning of the foot (Fig. 6.35). O-rings inserted inside the adjustment sleeve must prevent dirt from entering the thread section. USDA has imposed a new safety feature to prevent exposed thread parts due to overscrewing the sleeve (Fig. 6.36).

Also the fixation of feet to legs must be done in a hygienic way. Sometimes it is better to leave the leg end half open. In refrigeration

Leveling food processing and packaging equipment with improvised shimming creates an unhygienic mess

FIGURE 6.32 Leveling food processing and packaging equipment with improvised shimming creates an unhygienic mess. In case (A), several sheets of metal create plenty of metal-to-metal crevices in which dirt and liquids may collect (Don Graham, Graham Sanitary Design Consulting LCC, © 2010). In case (B), although wood may absorb moisture and food debris, a wooden plank is used to level the equipment. With time, this wood becomes prone to rot. The foot is fixed to the equipment subframe by means of rivets in an overlapping sheet construction. The horizontal section may accumulate dirt.

Adjustable feet with exposed threaded spindle easily become prone to contamination and are difficult to clean

FIGURE 6.33 Adjustable feet with exposed threaded spindle easily become prone to contamination and are difficult to clean. Lower middle photo shows a hollow leg which is not hermetically closed. Photo at lower center courtesy of Joe Stout, Commercial Food Sanitation LLC - Intralox, © 2016.

Adjustable feet with the threaded spindle completely concealed in closed pro- files/pipes

FIGURE 6.34 Adjustable feet with the threaded spindle completely concealed in closed pro- files/pipes. In the first example (photo on the left), the thread of the foot is covered by the closed pipe, welded in a sheet metal leg (courtesy of Den Rustfri Stdlindustris Kompetencecenter). In the second example (photo in the middle), the foot can be screwed in and out at the bottom of the frame’s legs (courtesy of Alfa-Laval AB), while the thread still remains covered in the leg. In the third example (photo right), the leveling foot is screwed in leveling foot mount (courtesy of Schenck Process LLC). In the second and third examples, the contact surface of the feet with the floor is rather small, which will locally exert a (very) high pressure, especially if used to support heavy equipment prone to vibration/oscillatory movement.

Difference in cleaning results between

FIGURE 6.35 Difference in cleaning results between (A) a hygienic leveling foot having the spindle covered by a sleeve and an arrangement of O-ring silicone seals in all the mobile joints (left) and a standard fully threaded foot (right). Both feet were soiled with sour yogurt containing fluorescents (courtesy of NGIA/S). After rinsing to remove a large part of the soil, the feet were cleaned with detergent. In a postrinse step, the feet were flushed with water until visibly clean. (B) Both feet look visibly clean to the human eye. Opposite to the hygienic leveling foot (left), which was found to be free of residual soil and bacteria under UV light, the foot with exposed spindle thread (right) still contained residual soil and bacteria, visible as fluorescent spots under UV light.

equipment operating below 0°C, it is essential that any liquid entering the hollow leg can be drained to prevent cracking of the leg when ice forms at the inside (Fig. 6.37). But preferably, hollow legs must be hermetically closed, requiring adequate sealing of the points where the feet enter the

(left) Overscrewing the lock/sleeve may result in exposure of the thread in the area just below the sleeve

FIGURE 6.36 (left) Overscrewing the lock/sleeve may result in exposure of the thread in the area just below the sleeve. USDA therefore requires an additional feature to avoid overscrewing by blocking the sleeve or counter nut. Courtesy of NGIA/S.

The leg end is provided with a drain hole to allow draining of any liquids entering the hollow leg

FIGURE 6.37 The leg end is provided with a drain hole to allow draining of any liquids entering the hollow leg. However, in this design, dirt can get in the leg end and complete draining is not possible. The leg end may provide a niche where microorganisms can grow. Despite the drain hole, at below 0°C temperatures, the leg end can still crack under the impact of ice formed within the leg end. The footplate is also not hygienically fastened to the stainless steel floor plate. Courtesy of Stephanie Olmsted, Safeway Inc.,© 2016.

hollow leg (Fig. 6.38). Fixation of the leveling feet onto open profile legs may not leave thread parts exposed, requiring a top sleeve with O-ring seal and round top to cover the exposed thread parts (Fig. 6.39). Threadless adjustable feet are also available (Fig. 6.40).

Fixation to the equipment or equipment legs must be done in a hygienic manner

FIGURE 6.38 Fixation to the equipment or equipment legs must be done in a hygienic manner. (A) Stair riser leg, totally sealed, with sloped top and set off the riser (courtesy of Joe Stout, Commercial Food Sanitation LLC - Intralox, © 2016). (B) The stringers of staircases make no floor contact due to the fixing of hygienically designed leveling feet on the stair riser legs welded onto the stringers (courtesy NGIA/S).

(A) Fixation of the leveling feet onto open profile legs may not leave thread

FIGURE 6.39 (A) Fixation of the leveling feet onto open profile legs may not leave thread

parts exposed. (B) A top sleeve with O-ring seal and round top must be used to cover the exposed thread parts. Courtesy of NGI A/S.

Threadless adjustable feet hygienically fixed onto open profile legs. Courtesy of Rudi Groppe, Heinzen Manufacturing International, © 2016

FIGURE 6.40 Threadless adjustable feet hygienically fixed onto open profile legs. Courtesy of Rudi Groppe, Heinzen Manufacturing International, © 2016.

 
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