Design & construction of poultry processing plant : part 1 ~ University Notes

GENERAL DESIGN PRINCIPLES

Planning

The reasons for planning a small scale poultry processing plant in the tropics usually come about as a consequence of a desire to make improvements on an existing system. The first stage of planning therefore, is to collect information regarding the exact nature of the project in terms of numbers of slaughterstock to be processed, management system required, costs of materials, services and labour, attitudes of the local population, markets to be served, type of product to be prepared, methods of waste disposal, availability of building materials, equipment and spare parts, specialised labour requirements, indeed everything required to complete a feasibility study. The feasibility study is usually conducted by technical and financial personnel. The expertise may be available locally but if not, can be commissioned internationally.

Economics

The economics of establishment and operation of the venture are usually among the first considerations when designing poultry plant. Small scale plants set up to the highest standards may not be financially viable operations. If this is so, some attempts should be made to quantify the social, hygiene and environmental benefits of the project to make an economic case for its establishment.

The following is a summary of the more important capital and operating costs of a poultry processing plant which should be taken into account when consideration is given to such a project:

Capital costs:

Land
Buildings
Plant and equipment
Installation
Contingencies
Working capital

Operating costs:

Personnel
Maintenance and spares
Water and sewage
Electricity
Fuel oil
Short life operating equipment (2–3 years)
Packaging materials
Insurance
Sundries (stationery, detergents etc)

The size and equipment to be used in the factory will depend not only on the scale of operation to be undertaken but also on the degree of productivity and nature of the end product. Consider the two examples which are given for operations of similar scale:

labour - intensive production of a wide range of products
high technology production of a narrow range of products.

Although the capital costs in the first example may be lower than those in the second (due to lower technology of the equipment), the recurrent costs, particularly those of labour) may be higher. Also, the buildings may need to be proportionally bigger to accommodate staff.

Because more people are employed, the first example has a requirement for a higher training input of production line workers than the second but the second has a greater requirement for highly skilled engineers to keep the factory working.

Because of the increased use of human resources, the first example introduces the possibility of greater variations and inconsistencies of product than the second, especially with respect to wholesomeness of the end product, its appearance and shelf life. The high technology example should produce material of consistent commercial quality. However, the need for maintenance and hygiene of the equipment introduces the need for maintenance and cleaning schedules of particular detail to ensure that complicated machinery is made ready for the next day's production.

Management

The exact management system which is to be operated must be established early in a building project as this will have a bearing on its design and the equipment to be installed. It should be clear from the outset if the project is to operate within the system established for the Public Service, along the lines of a commercial abattoir (whether in the Public Service or not), or if it is to be wholly private. The system of management of staff must be considered from the outset. The system of labour to be employed must be determined eg employed staff (time, piece, bonus rated etc) contracted staff, as a public facility etc or a mixture of systems.

To assist with the design of the facilities, management information should include:

The number of birds to be slaughtered, their type and weight and over what time period
The availability of slaughterstock and its seasonality
The ownership of the birds at each stage eg will the abattoir buy the birds from producers, will it slaughter for producers or wholesalers, will it sell the birds to wholesalers or through its own outlets. These factors influence the carcase identification systems and office requirements
The nature of the product to be prepared (New York Dressed, whole hot poultry carcases, whole chilled carcases, whole frozen carcases, chilled or frozen joints etc)
What parts of the carcase are considered as edible and inedible. eg chicken feet, unused in many parts of the world are considered a delicacy in others. This will assist with by - products and effluent plant design
The slaughter system to be considered appropriate eg will the birds move along and overhead railway system to the processing machines or will the staff carry the birds to the machines
The level of technology to be employed

All the above factors will influence the technology and economics of the systems finally employed.

Location of Plant

In an ideal situation, poultry should be produced in feed production areas, usually to be found in rural districts. The poultry should be slaughtered nearby and preserved so that the product, when it is of highest value and lowest weight is carried to the market. In this way, transport costs and bird mortality are kept to a minimum and economical use can be made of slaughter by - products in agricultural production. In practice this is not always possible eg where birds are produced in small numbers under an extensive system (not necessarily in the rural areas); the market requires fresh, unchilled meat; transport, with its refrigeration, is unreliable. For many reasons, poultry may need to be slaughtered nearer to the market.

The site for a poultry processing plant should be chosen with care. Primarily, consideration should be given to the provision of services. Adequate water, electricity, gas, oil and telephone should be to hand. Labour to manage, operate and maintain the plant is also essential. These staff need not necessarily be drawn from an existing labour pool of experienced slaughter staff since training in production methods must be given on modern equipment. Maintenance staff will need access to tools, materials and spare parts. The site should have good vehicle access, for road communications and, if appropriate, rail and river connection. Access by emergency services should also be considered.

The space requirements of the poultry processing plant is important. Ample areas should be available for parking, turning, waste disposal systems, and ancillary buildings and functions is required. As a general rule, the buildings should occupy about 20% of the total ground area. An eye should be given to future expansion of the building and its facilities.

The best sites are those situated on a gentle slope which, if this is not to be a completely rural site, should be to the lee of any built - up areas. Care must be taken if the poultry processing plant is to be built on an industrial “estate”. Contamination of the poultry may occur from the odours, fumes, smoke, steam or particulate matter eg flour millings, sawdust etc from other manufacturing processes as could contamination by the poultry of other industrial processes eg dairy or confectionery industries. Proximity to other abattoirs or meat processing factories is best avoided. However, the potential for sharing the poultry and other meat processing facilities eg by - products processing, effluent disposal etc, may be a factor in the economics of establishment of the poultry plant. In this case, especial care should be taken to prevent cross contamination of one product by the other.

The ground of the chosen site should have good load - bearing characteristics to support the building itself and adequate drainage. The drainage is necessary for rainwater to run off. It is not to be used as a substitute for a proper effluent disposal system. The effluent disposal system should be designed so that the ground water or other water source used for residential, industrial or, indeed, the poultry processing plant itself is not contaminated. Nevertheless, one of the most important services to the plant is effluent disposal and its effective handling is facilitated through an adequate gradient and soil type. This is discussed later in this chapter.

Whatever site is chosen, the proposal to build a poultry processing plant, no matter how small, should be discussed with the local dignitaries and population to seek their approval. Some obvious sites may have to be rejected as it may be consecrated, used for local recreation etc.

Facilities Required

Consideration should next be given to the type and number of facilities required. This may include reception area, slaughterhall, dressing rooms, chilling and freezing facilities, processing rooms, chill, frozen and dry storage rooms, dispatch areas, by-product processing rooms, laundry, ice production rooms, offices, changing rooms and toilets, messing facilities, first aid rooms, crate and vehicle wash areas, effluent treatment, workshop, boiler and refrigeration rooms. Depending on the system of operation, not all will be required but more than one will be needed in others. The system of management may also include facilities to operate a shop, wholesale market etc.

Flow Diagram

Using this information, a flow diagram should be drawn up, bearing in mind the management system to be employed. A typical system is given in Annex 1. Some of the services have been included to illustrate the growing complexity of the system. To each of the processes, the number and sizes of the rooms should be added.

Equipment and Machinery

The machinery to be used in the plant should be decided on the level of technology best suited to the management system chosen and the estimated maximum throughputs envisaged for the foreseeable future. Equipment is usually bought to last for ten years after which time it is worn out, obsolete or redundant but this will depend on:

the likelihood of having funds to expand further in ten years' time. If it is unlikely that the plant will be able to re - equip in ten years, the time frame may be expanded. This will also depend on:
the history of the poultry production and processing industries. The time frame can be adjusted to address the confidence shown in these industries, its continuing economic viability and the economics brought about by the purchase of new equipment.
the history of equipment maintenance and breakages etc. in other processing industries. If maintenance is known to be good, the time frame can be extended. If not it may be reduced and the level of technology adjusted to suit the circumstances.

The manufacturers' specifications should be checked to determine:

the designed throughput of the equipment
the space requirements to operate the equipment
the robustness of the equipment
its specification in terms of power ratings and consumption, pressures, speeds, temperatures etc
that the equipment meets the legal and safety requirements laid down in law or, in its absence, that of straightforward common sense

Hygienic Principles of Design

Clean and dirty areas

The architectural drawings should give attention to the hygienic principles in design. Points to watch are that “clean” and “dirty” operations are kept separate and carried out in dedicated facilities. This means that separate rooms are required for:

reception of birds,
slaughter, scalding and defeathering
evisceration, washing and giblet processing
chilling
cutting and packing
freezing and storage
dispatch
by - product processing

A diagram showing separation principles is given in Annex 2.

Product flow

The plans should show a smooth flow of product along the processing line, with minimum distances between all operations including those which require other materials to be used in the process eg the ice harvester should be near to the chiller tank, the packaging materials should be close to the packaging machine. There should be minimum interference between other operations and cross flows of operations and operators should be kept to the absolute minimum.

Equipment

The general guide - lines for equipment design, manufacture, installation and operation are long and detailed. The equipment generally available is usually of sufficient standard if obtained from a reputable manufacturer. The following description outlines the general principles to be followed, particularly where local manufacture or fabrication is planned.

The equipment to be used in a small scale poultry processing plant in the tropics must be strong and effective enough to last for at least 5 years. Replacement is often difficult (usually through lack of funds) so it should be obtained with a view to longevity easy maintenance and repair. The equipment must be maintained to a schedule, which should be established before installation and based on the manufacturers information. In the tropics, it will almost certainly be used on birds of different sizes and weights, if not different species from that chosen for the original project, so equipment should be selected with a view to adaptability as far as possible. The equipment must conform to local standards of construction and safety. It should have proper safety guards, maintained in full working order. The equipment must be designed to be cleaned properly after use. It must have smooth surfaces, clean welds, an absence of bolts and irregular protuberances, made preferably in stainless steel or at least galvanised steel which has been hot - dipped after manufacture. The use of paint and mild steel is not recommended as it will easily flake in the atmosphere and contaminate the carcases.

In the interests of hygiene, stairways, overhead gangways, platforms, steps etc should be made of aluminium alloy checkerplate which can be cleaned much more easily than iron grills. Wash hand basins, which should be made in stainless steel rather than china, should be provided with cold and hot water at 82°C and operated by foot, knee or arm. Sterilizers for knives and hand tools and equipment should be used. They may be attached to the wash hand basin and these also should run at 82°C.

Sterilizer unit

Mobile equipment or that used part - time or irregularly should be stored in proper facilities out of the way when not in use.

All equipment should be installed at a sufficient distance away from walls to permit installation, operation, cleaning and maintenance. If not sealed to the floor, it should be raised 200mm to facilitate cleaning underneath.

Drains

Floors should have falls in the region of 1:60 so that waste water flows away rapidly but not so steeply that it causes difficulty in walking, movement of other traffic or positioning of static equipment. Drains, which may be open channels covered with a well fitted grill, should flow from clean to dirty areas. Drainage pipes should be at least 150mm in diameter so that they will run freely and not block with the large weights of feather, fat and faeces which pass over the floor. Drains should be screened at the exist to the building. Effluent disposal systems should be designed to suit the nature of the waste and its volume. This will depend on the system of operation and management chosen above.

Floors, walls and ceilings

There is a temptation to economise on the quality of wall and floor structure and finishes. This is false economy. Poultry blood, fat and other tissues are very corrosive. The work involved is heavy and intensive. Any economies made will rapidly show and constant maintenance will be required if good hygienic standards are to be maintained. The floors and walls must be easy to clean, smooth, impermeable and acid resistant. The floors must be non-slip to prevent accidents and should be coved with the walls. The walls should be coved and rounded to each other to prevent accumulation of dirt and water. The walls and floors may be finished in tile but this should be completed in materials of very high quality and laid with excellent standards of workmanship. A simple granolithic screed, spread across the floor and up the walls is relatively cheap, durable and hygienic but lacks visual appeal. The temptation to finish walls in domestic paint should be avoided as this discolours and flakes, thereby contaminating the poultry product. There are suitable epoxy resin finishes in white which may be applied if appearance is important. These are sometimes referred to as a “liquid tile”. Walls should be finished to a height of three metres. Where product or equipment comes into regular contact with the walls or floors, reinforcement will be needed. This should be established before operation commences since it may be difficult to fix hygienically after production has been underway for several weeks.

Doors and windows

Windows should be encased in non-corrosive material eg metal alloys, not wood, and should have sloping sills so that items of clothing, knives, bottles etc cannot be stored. Doors should have alloy frames and impermeable surfaces. The whole building should be proofed against insects, rodents and birds.

Service runs

Service runs and ducting need special attention. Pipework runs should be simple and straight, preferably buried in the walls or floors, or run down an outside wall before it passes into the room in which it is required. Pipes buried in the wall should be in stainless steel where they emerge into the room as they tend to corrode at this point making repair very difficult and expensive. Pipes which run inside a production room should be stainless or galvanised and mounted in wall spacers so that they are 50mm from the wall. Suspended pipework should not be located over product lines. Should they attract condensation, leak, need repair etc, production and product quality will be affected. If necessary, pipework and ducting should be suspended from trapeze hangers. Electrical runs should also be buried or run in conduit. Switches, lighting fixtures and other electrical fittings and fixtures should be of waterproof standard, able to withstand the unintentional play of a hose pipe or steam lance if they cannot be situated outside production areas.

Lighting

This has to be of a standard for both general work and for meat inspection purposes. Daylight is the cheapest form of lighting but it is sometimes difficult to provide sufficient in all areas. In Europe, windows are not favoured as they let in dirt and insects, and let out heat. In the tropics it would be churlish not to use the light which is so amply available. Lighting should be about 220 lux in working areas and 540 lux in inspection areas at a height of 1.2m from the floor. Note the advice regarding the need for waterproofing electrical fittings given above.

Ventilation

Adequate ventilation is essential in tropical meat processing rooms. The air temperature and humidity of the air can be very high and its extraction imperative if comfortable working conditions are to be maintained. Condensation is a problem which must be addressed. The Venturi effect, where one wall, heated by the sun, causes an updraft of air which is voided through a slot in a pitched roof is preferred but care must be taken to prevent entry of birds, insect and rodents. Artificial extraction of air is expensive but may be necessary especially in countries where temperatures fall considerably overnight and open ventilation systems would be inappropriate. The equipment used for ventilation should be considered as internal equipment and conform to the standards set out above. In general rooms, six changes of air every hour are sufficient for comfort but in processing rooms, particularly where there is steam production, this may need to be increased to 20 or more.