Manual cleaning is adaptable to all types and sizes of buildings, equipment and tools but its effectiveness depends heavily on the worker. Manual cleaning will always require considerable input of manpower. Nevertheless, it may be the cheapest method.
When cleaning manually great care must be taken to assure that brushes and equipment are cleaned to avoid cross-contamination. Essential will be frequent changes of water and water/detergent solutions. It is recommended that smaller equipment and items are collected for central cleaning by hand and in this respect the following 3-tank system can be recommended:
Remove soil from the equipment by scraping the surfaces (see Fig. 4 a).
Transfer the equipment to tank no. 1 which contains a suitable solution of water and detergent. Loosening the soil may require soaking for a period (see Fig. 4 b).
The equipment is then transferred from tank no. 1 to tank no. 2, which contains a solution of water and detergent. The equipment is scrubbed clean (see Fig. 4c).
The equipment is rinsed in water (from pails or running water from water hoses) (see Fig. 4 d).
The next step is transferring the equipment to tank no. 3 containing hot water (77°C) for at least one-half minute to have a disinfecting effect (see Fig. 4 e).
The equipment is stacked to drain and dry quickly.
An alternative to step 5 is to use a solution of chemical disinfectant and allow contact for several minutes. Post-rinsing in clean water is required after chemical disinfection. For chemical disinfection a solution containing 200 ppm of available chlorine may be recommended. If the equipment is made of wood, the solution should contain 500 – 1000 ppm of available chlorine.
If the water supplies are insufficient, step 2 may be omitted. Thorough removal of soil from surfaces will then be required.
If manual cleaning with brushes is used for cleaning large freestanding equipment and buildings the water has to be brought to the parts. The best solution will be to use running water from water hoses. Where water supplies do not allow running water a 3-pail system is recommended for cleaning. Two pails should contain a solution of water and detergent and the third clean water. The pails and brushes etc. should be placed in a trolley.
Fig. 4. Manual cleaning, 3-tank system. (Illustration by U. Boyter).
The first pail containing water and detergent is used for dipping and cleaning of the brushes.
The water/detergent solution in the second pail is used for cleaning. A measuring cup or a small container may be used for application of the water/detergent solution to the surfaces. The surfaces will then be cleaned by a clean water/detergent solution.
The clean water in the third pail is used for rinsing purposes.
If the rinsing can be done with running water it should be preferred. Then the three-pail system will be reduced to a two-pail system.
It will be obvious that energy is required for cleaning purposes. The mechanical force needed will be supplied as electrical force or pressure, or maybe a combination of both (e.g. pressure cleaners).
Electricity may be used for automatic floor scrubbing machines or vacuum cleaners for water suction in food processing areas. These machines will not be economical in use in processing areas, but will have advantages in areas with different functions such as resting rooms, walking areas etc.
Pressure will be used in manual spraying systems. These systems may be constructed with special nozzle arrangements or with a handoperated pump and special nozzles to give a certain pressure. The nozzles are supplied with different sizes of holes and different spreading angles (see Fig. 5). When worn, nozzles should be replaced. As a manual spraying system, sprays constructed for spraying trees or flowers with insecticides etc. can be recommended.
Fig. 5. Principle in nozzles. The first two figures show the spreading angle and the last two figures show the size of hole(mm).
The spreading angle is important for pressure against surfaces. An angle of 0° gives a massive jet of water. If the angle is larger, the jet of water will be less massive (see Fig. 6).
Fig. 6. Nozzles with spreading angles of 0° and 45°. The jet of water from the 45° angle is obviously less massive than the jet of water from the 0° angle.
The nozzle principle will be the same independent of manual or automated systems.
There are different types of pressure cleaners available and the choice will always be a compromise between various advantages and disadvantages.
Pressure cleaners exist in many varieties and trade marks and for specific details it will be necessary to obtain information from manufacturers, instruction handbooks, etc.
Electric installations and water taps will be necessary. Application of detergent may require the installation of compressed air (air compressors).
Pressure cleaners may give pressures from 4–180 bar and it will be possible to change the pressure between these values according to cleaning purposes.
The pressure cleaner systems will either be:
high pressure-low volume system or
low pressure-high volume system
High pressure-low volume systems are economic in use concerning water consumption but have several disadvantages concerning the maintenance of buildings, machines and equipment. When using high pressure for prerinsing and rinsing, the pressure may cause spreading of soil in the whole area, even under the roof construction.
Rinsing with high pressure will cause aerosols. Aerosols are small droplets of water that may contain chemicals and microorganisms which may lead to irritation of the respiratory tract. High pressure cannot be recommended for application of detergents and disinfectants because of these aerosols. If used for application of chemicals the pressure must not exceed 5 bar. Aerosols may also cause problems when penetrating coverings of electric installations.
High pressure can damage the wall and floor surfaces of the buildings, the equipment and machines. For example, high pressure used wrongly on tiled walls may loosen the tiles.
The advantages of using high pressure are the short time and low water consumption for rinsing purposes and removal of most soil types. It will be very time-consuming if used for prerinsing because of the low water consumption. Water hosing may then be used for prerinsing.
Low pressure-high volume systems are costly in use because of large water consumption.
Cleaning systems working with low pressure (30 bar) and low volume (18–20 1/min) have been developed. The low volume is increased a little compared to the high pressure-low volume system but overall this kind of cleaning system may save water because the system can be used for both prerinsing and rinsing.
When using pressure for cleaning the detergent can be applied after the same principle independent of the pressure and the volume. Injector systems can be combined with the different pressure systems. The injector will be connected to the water supply of the cleaning system and have an intake for water, detergent and air (see Fig. 7). When used for rinsing purposes the intake of detergent and air can be closed.
Fig. 7. An injector showing intake of water, detergent and air. The intake of detergent and air can be closed.
When using pressure cleaners the cleaning results will depend on :
Water pressure and spreading angle
Time and efficiency
When choosing pressure cleaning systems, the instructions from the supplier must be followed and personnel given sufficient instructions and practical training before start of cleaning.
Special instructions for using the appropriate nozzles, choosing an appropriate length of jet pipes and correct handling of jet pipes must also be given.
Correct handling of jet pipes covers:
appropriate working rate
appropriate distance from the surfaces which are to be cleaned (see Fig. 8)
appropriate angle achieving a chisel-like effect (see Fig. 8)
appropriate working movements (see Fig. 9)
Fig. 8 The distance between the nozzle and the surface should be 30 cm and the angle between the surface and the jet of water should be approximately 45° (effect of a chisel).
Fig. 9 Jet movements on hard, smooth surfaces
Movements for application of detergents. The movements should be smooth and cover an appropriate working breadth. The movements should go from below working upwards.
Movements for rinsing. These should go up and down utilizing the water as much as possible.
The systems for cleaning should be chosen in accordance with the actual conditions of the slaughterhouse. If automatic systems are chosen, delivery time of spare parts for the system should be considered as well as the possibility for service when repairs are required.