英文文献：年产万吨的苹果汁工厂设计

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英文文献

2.5.3. Design and construction of the building

Roofs and ceilings

Walls

Windows and doors

Floors

Lighting and power

Water supply and sanitation

Layout of equipment and facilities

In general, a building should have enough space for all production processes to

take place without congestion and for storage of raw materials, packaging materials

and finished products. However, the investment should be appropriate to the size

and expected profitability of the enterprise to reduce start-up capital, the size of

any loans taken out and depreciation and maintenance charges.

Roofs and ceilings

In tropical climates, overhanging roofs keep direct sunlight off the walls and out

of the building. This is particularly important when processing involves heating, to

make working conditions more comfortable. Fiber-cement tiles offer greater

insulation against heat from the sun than galvanized iron sheets do. High level vents

in roofs both allow heat and steam to escape and encourage a flow of fresh air

through the processing room. The vents must be screened with mesh to prevent

insects, rodents and birds from entering the room. If heat is a serious problem, the

entrepreneur could consider fitting electric fans or extractors, although this clearly

increases capital and operating costs.

Rafters or roof beams within the processing and storage rooms are unacceptable.

They allow dust to accumulate, which can fall off in lumps to cause gross

contamination of products. Similarly, insects can fall from them into products. They

also allow paths for rodents and birds, with consequent risks of contamination from

hairs, feathers or excreta. It is therefore essential to have a paneled ceiling fitted to

any processing or store-oom, with careful attention when fitting them to ensure that

there are no holes in the paneling. Care should also be taken to prevent birds,

rodents and flying insects gaining access to the processing room through gaps in the

roof structure or where the roof joins the walls.

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Walls

As a minimum requirement, all internal walls should be rendered or plastered

with a good quality plaster to prevent dust forming in the processing room. An

experienced plasterer should be used to ensure that no cracks or ledges remain in

the surface finish, which could accumulate dirt and insects. The lower area of walls,

to at least 1.08 metres (four feet) above the floor, is most likely to get dirty from

washing equipment, from product splashing etc. and special attention should be

paid to ensure that this area is easily cleaned. Higher areas of walls should be

painted with a good quality emulsion. The lower parts of walls should be either

painted with a waterproof gloss paint, preferably white, to allow them to be

thoroughly cleaned, or ideally they should be tiled with glazed tiles. If tiling a

process room is too expensive, it is possible to select particular areas such as behind

sinks or machinery and only tile these parts. In some countries there is a legal

requirement for specified internal finishes and this should be checked with the

Ministry of Health or other appropriate authority (see also Section 2.4.2)

Windows and doors

Window sills should be made to slope for two reasons: to prevent dust from

accumulating and to prevent operators from leaving cloths or other items lying there,

which in turn can attract insects. Windows allow staff to work in natural daylight,

which is preferable to and cheaper than electric lighting. However, in tropical

climates there is a natural inclination for workers to open windows to allow greater

circulation of fresh air. This provides easy access for flying insects, which can readily

contaminate the product. Windows should therefore be fitted with mosquito mesh

to allow them to be left open.

Normally doors should be kept closed, but if they are used regularly there is

again a tendency for them to be left open with similar consequences of animals and

insects entering the plant. In this case, thin metal chains or strips of material that

are hung vertically from the door lintel may deter insects and some animals, while

allowing easy access for staff. Alternatively mesh door screens can be used. Doors

should be fitted accurately so that there are no gaps beneath them and all

storeroom doors should be kept closed to prevent insects and rodents from

destroying stock or ingredients.

Floors

It is essential to ensure that the floors of processing rooms and storerooms are

constructed of good quality concrete, smooth finished and without cracks. In some

developing countries, it is possible to buy proprietary floor paints or vinyl based

coatings, but these are usually very expensive. Generally, it is not adequate to use

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the red wax floor polishes that are commonly found in households, as these wear

away easily and could contaminate either products or packages. Over time, spillages

of acidic fruit products react with concrete and cause it to erode. Attention should

therefore be paid to cleaning up spillages as they occur and to regularly monitor the

condition of the floor.

The comers where the floor and the walls join are places for dirt to collect.

During construction of the floor, it should therefore be curved up to meet the wall.

It is possible to place fillets of concrete (or 'coving') in the comers of an existing floor

to fill up the right angle, but care is needed to ensure that new gaps are not created

which would harbour dirt and insects.

The floor should slope at an angle of approximately 1 in 8 to a central drainage

channel. At the end of a day's production, the floor can be thoroughly washed and

drained. Proper drainage prevents pools of stagnant water forming, which would in

turn risk contamination of equipment and foods. The drainage channel should be

fitted with an easily removed steel grating so that the drain can be cleaned. Where

the drain exits the building, there is a potential entry point for rodents and crawling

insects unless wire mesh is fitted over the drain opening. This too should be easily

removed for cleaning.

Lighting and power

General room lighting should be minimized wherever possible. Full use should

be made of natural daylight, which is both free and better quality light, especially

for intricate work. Where additional lighting is needed, florescent tubes are cheaper

to operate than incandescent bulbs. However, if machinery is used that has fast

moving exposed parts, these should be lit with incandescent bulbs and not tubes.

This is because even though the parts should have guards fitted, a rotating machine

can appear to stand still if its speed matches the number of cycles of the mains

electricity that powers fluorescent tubes - with obvious dangers to operators.

All electric power points should be placed at a sufficiently high level above the

floor that there is no risk of water entering them during washing the floor or

equipment. Ideally, waterproof sockets should be used. It is important to use each

power point for one application and not use multiple sockets which risk overloading

a circuit and causing a fire. If there are insufficient power points for the needs of a

process, additional points should be installed, even though this is more expensive.

All plugs should be fitted with fuses that are appropriate for the power rating of the

equipment and ideally the mains supply should have an earth leakage trip switch. If

three-phase power is needed for larger machines or for heavy loads from electric

heating, it is important that the wiring is installed by a qualified electrician to

balance the supply across the three phases.

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Water supply and sanitation

Water is essential in nearly all fruit and vegetable processing, both as a

component of products and for cleaning. An adequate supply of potable water

should therefore be available from taps around the processing area. In many

countries, the mains supply is unreliable or periodically contaminated and it is

therefore necessary for the entrepreneur to make arrangements to secure a regular

supply of good quality water each day. This can be done by installing two high level,

covered storage tanks either in the roof-space or on pillars outside the building.

They can be filled alternately when mains water is available and while one tank is

being used, any sediment in water in the other tank is settling out. As sedimentation

takes several hours, the capacity of each tank should be sufficient for one day's

production. The tanks should have a sloping base and be fitted with drain valves

above the slope and at the lowest point. In use, water is taken from the upper valve

and when the tank is almost empty, the lower valve is opened to flush out any

sediment that has accumulated.

Water that is included in a product should be carefully treated to remove all

traces of sediment and if necessary, it should be sterilised. This is particularly

important if the product is not heated after water has been mixed in as an

ingredient.

There are four ways of treating water at a small scale: by filtration; by heating;

by ultra-violet light and by chemical sterilants, such as hypochlorite (also named

'chlorine solution' or 'bleach'). Other water treatment methods are generally too

expensive at a small scale of operation.

Filtration through domestic water filters is slow, but having made the capital

expenditure, it is relatively cheap. Larger industrial filters are available in some

countries. Heating water to boiling and holding it at that temperature for 10-15

minutes is simple and has low capital costs, but it is expensive because of fuel costs

and it is time consuming to do routinely. Heating sterilises the water but does not

remove sediment and boiled water may therefore require filtering or standing to

remove sediment.

Ultra-violet light destroys micro-organisms in water and commercial water

treatment units that use this principle (Figure 38) are coming down in price to the

point that they can be suitable for those small scale processors that use a lot of

water. Again, this method does not remove sediment from the water.

Finally, chemical sterilisation using hypochlorite is fast, relatively cheap and

effective against a wide range of micro-organisms. Cleaning water should contain

about 200 ppm of chorine and water that is used as an ingredient should contain

about 0.5 ppm to avoid giving a chlorine flavour to the product. A chlorine

concentration of 200 ppm can be made by adding 1 litre of bleach to 250 litres of

water and a 0.5 ppm solution is obtained by adding 2.5 ml of bleach to 250 litres of

water. Although chlorine kills most micro-organisms, it also has a number of

disadvantages: it can corrode aluminium equipment; it can taint foods; bleach must

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be handled with great care as it damages the necessary, the concentration of

chlorine in water can be measured using a chemical dye that produces a colour when

it reacts with chlorine. The intensity of the colour is compared to standard colours

on glass discs in a 'comparator'.

Good sanitation is essential to reduce the risk of product contamination and to

deter insects, rodent and birds. All wastes should be placed in bins and not piled on

the floor. Processes should have a management system in place to remove wastes

from the building as they are produced, rather than letting them accumulate during

the day. Wastes should never be left in a processing room overnight. This aspect is

described further in Section 2.7.2, and summarized in Appendix I.

Layout of equipment and facilities

The different areas required for fruit and vegetable processing are shown in

Figure 39 for a drying unit and in Figure 40 for other types of production. The layouts

of these processing rooms show how raw materials move through a process and

through the room without paths crossing. Different stages in a process should be

physically separated wherever possible. This helps prevent contamination of

finished products by incoming, often dirty, raw materials and clearly identifies areas

of the room where special attention to hygiene is necessary. This is particularly

important to prevent contamination arising from activities such as bottle washing in

which inevitable breakages produce glass splinters that could contaminate a product.

This separation also reduces the likelihood of accidents or of operators bumping into

each other.

Perishable raw materials should be stored separately from non-perishable

ingredients and packaging materials. A separate office allows records to be filed and

kept clean and provides a quieter working environment for book-keeping. Toilets

should either be housed in a separate building or two doors should exist between

them and a processing area. All workers should have access to hand-washing

facilities with soap and clean towels. Laboratory facilities are generally not needed

in fruit and vegetable processing, although a separate table for conducting quality

assurance checks or check-weighing packages of finished product (Section 2.7.2)

could be located in the office or in a separate area of the processing room.

英文文献译文

2.5.3.

建筑物的设计和建造

屋顶和天花板

墙壁

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