Part I RisksRisks
7.9 Inside the plant
When sanitary design features are incorporated into a new structure or into a renovation or addition plan, they will result in an improved appearance of the structure, and will reduce the time required for sanitation. This will fulfill many Improving building design 133
of the purposes of sanitary design to make sanitation more effective, faster, and more economical while satisfying regulations and customers' expectations. In this section we will cover the sanitary design recommendations for floors, walls, ceilings, drains, lighting, heating, ventilation and air conditioning (HVAC) systems, personnel facilities as well as miscellaneous items.
7.9.1 Floors
Although there is an entire chapter devoted to floor design, it must be said in this overview chapter that floors are the most abused surface in a food processing plant. Floors must withstand chemical abuse from the use of water, dust, cleaners, sanitizers, acids, and lubricants, and even the abuse from particles and pieces of the food product being produced. They must also withstand the abuse received from mechanical means of dropped equipment and tools, pallets being dragged over the surface, from equipment being moved and holes drilled to fasten it down. Foot traffic and forklift or pallet jack traffic will cause a lot of abuse to floors. The floors can be exposed to temperature swings from clean-up water, spillage of cooking items, hot oil from fryers, cold water from chill tanks, hot and cold water from the sanitation shift, etc. For long-lasting floors, do not try to cut costs by purchasing a cheap covering that will not withstand the use and abuse it will receive. Cutting the capital cost will result in increased maintenance costs down the line. Wood floors are no longer acceptable in food processing facilities. There are many old facilities that still have wooden floors in the dry processing areas for flour, starch, dry grain handling, etc. However, they are not acceptable in wet processing areas.
The most common base material is concrete, which is then covered with a sealer or monolithic coating or a brick/tile material. If concrete is not sealed or otherwise covered, especially in wet processing areas, spalling can occur where the troweled layer wears away or is eaten away and the aggregate is exposed.
Water containing high levels of chlorine will rapidly eat away the troweled layer.
Acids, food products, and plain water will also attack unsealed or uncovered concrete. Exposed aggregate is a potential home for microbes where they find ideal hiding places and are extremely difficult to remove. Remember also that newly laid concrete floors must have a vapor barrier to prevent migration of moisture from the soil below the floor. Moisture from this source will virtually destroy monolithic floor coatings. Monolithic coatings can be epoxy, urethanes, resins, or combinations of these depending on the type of abuse the floor will receive. Chips in floor coverings in wet areas can lead to water getting under the coating and lifting it off the concrete. As it is doing this, microbiological soup is created under the coating and every time forklift wheels or foot traffic passes over the defect, it is exposed to a loading of microbes from the water expelled through the chip or hole or crack in the coating. This microbial contamination can then be spread wherever the forklift of the foot traffic goes.
For long-lasting floors many companies use acid brick or split pavers or tile.
Although the high-end full acid bricks may be more expensive than monolithic 134 Handbook of hygiene control in the food industry
coatings, they usually last for many years with minimal maintenance. The main thing to remember is that floors must withstand use, cleaning, and abuse.
Monolithic coatings are getting better and better. There are some that bond with the concrete and have approximately the same coefficient of expansion and contraction and are seamless. There are a number of firms that sell these types of floor coating. Degussa Resin Systems (SRS Degadur Corp.) in particular and numerous others in general. Other flooring materials that have been used, but are not recommended in food processing rooms, are vinyl or asphalt tile, wood, metal plates, unless they are stainless, and bituminous/asphalt.
7.9.2 Drains
Wherever there are wet processing conditions drains will be required. Floor drains have proven to be sources of Listeria in food processing facilities unless correctly designed, installed, and maintained, and continually cleaned and sanitized. Drainage systems must meet all local and national plumbing codes.
The food regulatory agencies are basing their requirements of performance rather than dictate the construction of floor drains. The performance they demand is completely drained floors: no ponding or standing water is allowed on the production floors. The two most common drains are area drains or trench drains.
Area drains must have a p-trap and be spaced at a recommended one 4-inch (0.1 m) drain for each 400 square feet (~40 m2) of floor space. The floor should be sloped to the drain at a 1±2% slope. Area drains are the most common in meat processing plants and dairies. There are area drains on the market that exhibit sanitary design and are easily cleaned. All drains should be accessible for cleaning and application of sanitizer on a routine basis. Area drains should be a minimum of 4 inches (100 mm) in size and equipped with a removable metal strainer to catch food materials, and to prevent the entry of rodents and some insect pests such as cockroaches. They should also be designed to minimize the reflux of contaminated air that can come when a surge of water enters the drain.
The other most common choice is trench drains or gutter drains. Trench drains should be designed pre-sloped with rounded or coved bottoms. Square bottom drains are no longer recommended because of the difficulty in cleaning them and keeping them clean. Trench drains should be sloped at 1±2% slope for continuous drainage. Trench drains should be cleaned routinely and the grates constructed to withstand forklift traffic and any other wheeled traffic. There are, on the market, preformed trench drains that are easily cleanable and can be quickly installed.
Processing or packaging equipment should never be placed over an open area or trench drains. The air from the drains contains aerosols that can contain microbes.
These aerosols can contaminate otherwise clean equipment.
7.9.3 Walls
Wall design can be broken into two categories ± external and internal. External walls need to be water, rodent, and insect proof. The best material for external walls is concrete, followed by dense concrete block. Medium density block may Improving building design 135
be available in some areas of the country and will work. Light density or cinder blocks should not be used as they are porous and insects can work their way to the center of the block. Fumigation may be a problem as well since the fumigant will work its way to the center of the block and slowly release into the workspace long after the plant is back in production.
Many facilities use other materials, such as insulated metal panels and corrugated metal especially in pre-engineered buildings. Concrete walls can be cast in place (tilt up), precast, or formed and poured. Many concrete silos are cast in place using slip forms. If you intend to paint or apply epoxy coatings to tilt up walls, remember to match the release agent to the paint or coating material you intend to use. If the two are not matched according to the manufacturer's directions, the coating used may not adhere to the concrete.
Precast panels are done at a precaster's location and trucked to the site where a crane of similar piece of equipment hoists them in place onto a poured foundation or footer. The panels can and often are precast with an insulated center surrounded by concrete sealing the insulation into the concrete wall panel.
The joints of the precast panels will require caulking with a good caulking compound made with an acrylic base to retain elasticity. There will be some maintenance of these joints required, as the plant gets older. Precasting with the insulation already in the wall has the advantage of not having to attach insulation on the inner wall surface or under an additional surface covering material for refrigerated or otherwise temperature-controlled facilities. Tilt up concrete walls are often used when there is enough space to form and pour the wall panels at the construction site. These are preferred by some construction companies and used with great success. These too can be poured with enclosed insulation.
Pre-engineered metal buildings are not greatly preferred materials or building types. These panels are difficult to keep sealed as they have a high rate of expansion and contraction and can present condensation problems. If the metal panels are sandwich panels they must be equipped with secure and tight end caps to prevent rodent and insect infestation. Rodents can penetrate the insulation and roam freely inside the walls if end caps are not provided. All panel joints should be caulked with a good grade of caulk to prevent insect infestation inside the panels. There are materials on the market that can be sprayed on the interior of the panels to insulate and seal the insulation with a resin material that provides a seamless surface that is easily cleanable and resistant to damage.
When exterior walls are designed rodent proofing can be incorporated into the design. A very simple, inexpensive method is to install a rodent barrier at the base of the wall by installing a barrier of concrete or galvanized metal (anywhere from 16 gauge to 28 gauge) 24 inches (61 cm) down from grade level extending out at least 12 inches (30.5 cm). Rats burrow at an angle and will not try to go around this barrier but will abandon the burrow and go somewhere else.
There will be a need for wall penetrations for wiring, plumbing, ventilation, utility pipes, etc. These penetrations should be made, framed, and sealed the same day in order to prevent inner wall infestation by insects and often by rodents. Pipe penetrations require sealing with sheet metal or galvanized 136 Handbook of hygiene control in the food industry
hardware cloth or any other long-lasting material that will withstand rodent gnawing. Any penetrations below grade must be protected and sealed. If a number of pipelines enter at one spot then surround them with a galvanized fine mesh screen or hardware cloth to prevent rodent incursion. Cone guards can be used on vertical pipelines as well as flat guards. Whatever type your designer decides on must keep the rodents from gaining access.
7.9.4 Interior walls
Interior walls are constructed from numerous materials, ranging from tile, cement block, concrete, metal, reinforced fiberglass paneling, baked on enamel insulated metal panels, resin materials with built-in antimicrobials as well as dry wall in selected areas. Dry wall should not be used in any area where there is moisture or wash-down cleaning, or any kind of food processing taking place.
Whatever type of material is used, there are certain criteria that must be met for it to be considered a sanitary wall for food processing plants. According to Katsuyama (1993), the walls should conform to the following standards of sanitary design and construction:
· The juncture of the roof with the wall should be weather- and rodent-proof.
Wall plates should be sealed to prevent insect entry and avoid dust accumulation.
· Double walls of frame construction should have built-in rat stops. The insulation material must be unattractive to rodents for nesting.
· The inside surfaces of the wall should be water-resistant, smooth, washable, and easily cleaned. There should be no ledges to collect dust and debris. All rough or irregular surfaces in concrete walls should be rubbed or ground smooth to reduce dust and dirt accumulation; where grain and flour dust occur, such accumulations can become breeding spots for insects.
· All wall openings should have tightly fitting doors, windows, or screens to exclude rodents, insects, and other pests.
· Flat surfaces, such as horizontal braces, should be sloped at about 45ë to prevent their use for storage of personal and miscellaneous items.
· Particular attention should be given to areas that are subject to splash and spray. They should be surfaced to facilitate quick, easy, and frequent cleaning or flushing.
· The floor juncture of framed walls is of primary importance to sanitation. Its proper construction and maintenance are essential to adequate rodent control and general housekeeping. The juncture of the interior wall should be watertight and built on a coved base rising to a height of at least 6 inches (150 mm) above the floor level. Corners should be rounded to facilitate cleaning.
Companies are continually developing wall material that is cleanable and sanitary. Most materials now are white or very light colored. The material needs to be resistant to the cleaning and sanitizing compounds used in the facility.
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Resistance to damage is another important criterion since the use of troughs and other mobile equipment can damage and break the surface of the wall, thereby ruining the pest and water proofing of the wall. Protective barriers such as bollards and wall guards are recommended for areas where there is a high potential for damage. If cement block walls are erected in dry areas, the grout lines should be shallow to minimize ledges for dust to collect. Through experience, it has been found that a striking tool the shape of a stainless steel teaspoon works very well in creating a shallow grout line.
In wet areas the tile or block should be constructed using the stacked bond method rather than the running bond construction. Stacked bonding places each cement block or tile directly above the one below it. This yields a vertical grout line so moisture will drain down the grout line to the floor below. A running bond configuration puts the vertical grout line of each course of block directly in the center of the block below and the block above it. Moisture can and will accumulate at each layer where the vertical grout line meets the center of the tile or block below and can create a growth niche for microbes. A word of warning:
if the stacked bond method is to be used then the construction structural designers must be notified so the wall can be reinforced by either filling the center of the block with mortar or using reinforcing rods through the center of the blocks, or both if the facility is in a high seismic zone. If block walls are used then the first two courses of block should have the centers filled with mortar.
Doing this will not only prevent water or other liquids from seeping under the block to the area adjacent but will also prevent insects from gaining access to the interior of the block wall in case a crack develops at the floor wall junction.
Block walls should also be capped to prevent insect and rodent infestation in the center spaces of the block. Walls up to 6 feet (1.8 m) in height should be capped with a concrete cap at an angle of 45ë to 60ë to prevent tools, clip boards, etc., from being placed on the flat surface. Walls that go all the way to the ceiling or are over 6 feet (1.8 m) can be capped with a flat concrete slab. All interior walls should be constructed so the wall floor juncture has a cove with a radius of 1±3 inches (25±75 mm) to get rid of any crack at the juncture. Joint cracks are very hard to clean and can become harborages for dust, dirt, insects, and bacterial/
fungal growth.
If plain concrete walls are used (tilt up, precast or poured in place) and lining or epoxy coating them is not considered as in dry processing areas, warehouses, etc., then a good grade of sealer should be applied to prevent dusting of the concrete. Concrete dust will contaminate open products or settle on packaging material, finished goods and equipment.
Walls in new facilities should be designed without windows, particularly in the raw material storage, preparation, processing, and packaging rooms.
Windows require maintenance and are subject to breakage. There should be no glass in a food processing facility. Plants with existing windows in the subject areas should replace any glass with a tempered polycarbonate material.
The windows should be sealed to prevent opening, which will allow insects, dust, dirt, odors, and anything else present in the air into the facility. Open 138 Handbook of hygiene control in the food industry
windows will also destroy required air pressure relationships necessary for good air circulation within the facility. In older facilities where windows already exist, they should be sealed. If they cannot be sealed then they should at least be fitted with screens of 18 18 mesh or similar material to keep out insects if opened. Non-opening windows in interior walls are permitted, such as in supervisors' offices, as long as they are non-breakable material. Wire-reinforced glass will break and shatter with small pieces. Plexiglas material will also break into shards if struck so these are not recommended for interior or exterior windows. Windowsills should have a 45ë slope to prevent the accumulation of dust and debris and make them easier to clean.
Doors should be tight fitting with less than 0.25 inches (6 mm) clearance at the edges. The doors should be solid, as should the doorframes. Hollow doors and hollow doorframes can and do become harborage areas for insects and rodents. All doorframes should be flush with the wall with no ledges above the door. Any door windows should be of a polycarbonate material and mounted flush to the door on the sensitive product or process side. The other side or exterior of the door should have a sill of 45ë. All doors should be self-closing and designed to withstand the use expected. In food processing areas stainless steel doors are always acceptable. There are other materials such as fiberglass and fiberglass resin materials that are acceptable in sanitary areas.
7.9.5 Ceilings
Ceilings should be the easy-to-clean type and should be able to withstand direct impingement of water from hose stations. A ceiling should be a good reflector of light to help make the process area bright and shiny. It must be non-absorbent and above all cleanable. Smooth ceilings will allow better airflow across the ceiling surface and that, in turn, helps to prevent condensate formation. The most sanitary type of ceiling is the walk-on type. This type of ceiling completely seals off the trusses and other structural pieces holding up the roof and connecting the walls. All utilities can be run on the roof side of the ceiling with only vertical drops to the equipment below, thus eliminating horizontal runs of pipe in the process area. There must be access to the above ceiling area, from outside the process room, in order to do maintenance on the lines above the ceiling and for pest control. The space requires ventilation to reduce the possibility of condensate formation. In a well-designed and constructed walk-on ceiling space, the lights in the room below can be changed from above the ceiling. Recessed telescoping sprinkler heads are available, eliminating sprinkler pipes and sprinkler heads in the process room. With this type, ceiling process piping changes, pest control, etc., can all be carried on over the process room without intrusion into the process room envelope.
If at all possible, and the type of processing allows, the interior of the roof becomes the ceiling material. An example is the concrete double tee roof described earlier. The interior surface of the precast concrete double tee can become the ceiling surface. If this type of ceiling is to be used in a high moisture Improving building design 139