Layout Models for the Food Processing Industry
4. Development of the Model
A model can be developed for the
food industry to support Step D in the framework. Layout generation and
evaluation are often challenging and time consuming due to their
inherent multiobjective nature and complexity in the data collection
process as in L. C. Lin and G. P. Sharp, "Application of the integrated framework for the plant layout evaluation problem,". Past and emerging research is aimed at
developing methodologies to meet these needs. For example, C. S. Tak and L. Yadav
discusses an algorithmic approach to layout design. However, algorithmic
approaches have focused mainly on minimising flow distance in order to
minimise material handling costs. On the other hand, procedural
approaches have relied heavily on experience of experts. Therefore,
neither an algorithmic nor a procedural layout design methodology is
necessarily effective in solving practical design problems.
Food processing factories are governed by guidelines
developed by regulators. These guidelines describe the minimum
requirement relevant for the industry. GMP for industry is developed
based on these guidelines and the latest developments made in relation
to the industry. These mandatory GMP have to be adopted by the food
manufacturing factories to comply with product safety standards and
ensure hygiene. Hence there are many similarities in these factories.
These similarities can help to develop a common model layout applicable
for the food processing factories.
As discussed earlier, the food
industry norms have to be followed in designing factory layouts for
food manufacturing and segregation of work areas is important for the
food processing industries as they are characterised by a continuous
change in volume, type, and mix of products due to constantly changing
market requirements. On top of this, many critical control points
are present in the food processing industry. These have been identified
as hazards for the manufacturing process. Hence there should be adequate
controls to mitigate the risk of contamination. The site layout plays
an important role in this risk mitigation process. Thus, basic sections
of food processing facilities were identified as primary manufacturing,
secondary packing, warehouse, utility area, and administration.
The
hazards identified in HACCP are biological hazards (e.g.,
bacteria, yeasts, and moulds), chemical hazards (e.g., cleaning
chemicals and lubricating fluids), and physical hazards (e.g., glass,
insects, pests, metal, and dust). Layouts for food processing facilities
should be designed to minimise risks due to the above hazards. The
product is exposed to the environment at the primary manufacturing area.
Thus, it is the area, which poses the highest risk for hygiene in the
manufacturing process, and risk mitigation steps are essential to
prevent contamination. Environmental conditions in terms of humidity,
temperature, and particulate levels and the barometric pressure have to
be closely monitored and maintained within the primary manufacturing
section. Furthermore, the primary manufacturing area has to be
completely separated from the other areas to control the risk of
contamination. Employees moving to the primary manufacturing area should
undergo uniform changes as required by GMP requirements for the
manufacturing processes and adequate facilities are needed for this
activity. Personnel entry and the material entry paths to the factory
also have to be clearly segregated. This is a GMP and safety requirement
in the industry. The other four sections need to be placed to provide
maximum assistance to primary manufacturing while ensuring the food
hygiene requirements. Thus, it is important to clearly define the above
five basic sections of a food processing factory in a layout drawing. A
colour scheme as shown in Figure 3 is also proposed in order to identify
the basic sections. Food processing comprises many simultaneous
activities and can have complex layouts. These can take many shapes.
Therefore, the proposed colour scheme can potentially simplify the
layout design process by enabling easy visualisation.
Figure 3 Colour scheme to identify the five basic sections of a layout.
4.1. Layout Model
The
layout model for food manufacturing, called the "diamond model" (Figure
4), was developed by sequentially locating the five basic sections
discussed above. The traditional method of locating departments is based
mainly on two optimisation factors, the adjacency or distance
travelled. However, in this model, food safety (or GMP) becomes the main
criterion for optimisation to locate departments. Other traditional
factors are considered as secondary.
Figure 4 Diamond model.
Existing layouts present in the food industry were observed and evaluated in designing the model layout. Many layouts indicate that
the high risk and low risk areas are protected from the external
environment by only a solid wall. This can lead to pest ingression,
cross contamination, and direct contamination. Most of the time, the
utility system is located away from the high risk area; hence, heating,
ventilating and air conditioning (HVAC) ducting, steam lines, and
compressed air lines should move to this area through wall openings.
This poses a risk to the food processing plant. These risk factors can
be significantly controlled by surrounding the primary manufacturing
area with the secondary manufacturing area. The secondary manufacturing
area then has to be surrounded with other sections of the factory. This
prevents the external contaminants from reaching the primary and
secondary manufacturing areas. This reduces the risk due to biological,
chemical, or physical contamination. Finally, the utility,
administration, and warehouse areas should be attached to the secondary
manufacturing area.
The diamond model layout shown in Figure 4
ensures correct material and personnel movement within the factory. As
indicated in Figure 5, the material flow is from left to right. The raw
material and packing material received at the stores in left side are
converted to finished goods and transferred to the stores at the right
end of the layout. Personnel entry to the facility is from the
administration area at the bottom as shown in Figure 6. Thus, this model
minimises cross contamination and streamlines personnel and goods
movement on the factory floor.
Figure 5 Material movement in diamond model.
Figure 6 Personnel movement in diamond model.
The
model in Figure 4 clearly shows the five key areas of a food processing
factory. These five areas encompass all functions of typical food
processing factories. The space allocation for each of these sections
varies from the actual space requirements as per the manufacturing
process. This is performed when the framework is applied to identify the
space requirements in the layout.
4.1.1. Primary Manufacturing Area
The
product that arrives from the secondary manufacturing area is exposed
to the facility environment in the primary manufacturing area,
drastically increasing the contamination risk and thus it should be the
most protected area of the manufacturing process. Hence the above model
locates the primary manufacturing area at the centre of the layout to
isolate it from the outside environment as much as possible.
The
product usually enters the primary area through pressurised air locks.
Personnel also must enter through air locks and undergo gowning changes.
They need to wear head covers, shoe covers, masks, and gloves as
appropriate to the manufacturing process before entering the primary
manufacturing area. Hand-wash stations also need to be established at
the entry to the primary manufacturing area. Furthermore, entrances to
this area need to have air curtains to prevent outside air from entering
the high risk area.
As mentioned, the product is exposed at the
high risk primary manufacturing area. Thus, the air in this section
must be conditioned as a standard. The particle count in air is
controlled through high efficiency particle absorption (HEPA) filters
and relative humidity is controlled as per the process norms. The air
pressure is also maintained at a slightly higher level than that of the
secondary manufacturing area to prevent particulates from getting into
the primary manufacturing area. The pressure difference between low and
high risk areas is kept between 5 and 15 Pa so that the air flows to the
low risk area from the high risk area is 1.5 m/sec or greater through
openings.
4.1.2. Secondary Manufacturing Area
The product
is first exposed to the facility environment in the secondary
manufacturing area. The raw material enters the secondary manufacturing
area from the stores. The product being manufactured at the primary
manufacturing area is usually in its primary packing when it reaches the
secondary manufacturing area, and the secondary manufacturing area is
the entity in which the final packing of the product takes place. Then
the product in its final packing is sent to the finished goods
warehouse. Hence, air locks need to be placed between the stores and
secondary manufacturing area to prevent contamination through leaking
air. These air locks also prevent pests from entering the secondary
manufacturing area.
The personnel entry to the secondary
manufacturing area is from the administration area and that too needs to
be through air locks. It is also usually equipped with a gowning regime
to change to designated clothes before entering the secondary
manufacturing area. Thus, the gowning area needs to be appropriately
placed in the administration section of the layout.
The air
quality of the secondary manufacturing area is maintained as specific to
the manufacturing process. The same pressure difference is maintained
between the primary and secondary manufacturing areas so that the air
flows to the low risk area from the high risk area. Here, it is
also good practice to maintain positive pressure (e.g., 0.02 mm H2O)
with respect to the utility, stores, and office areas. The positive
pressure prevents outside air from reaching the secondary manufacturing
area. This prevents possible contamination of the product.
4.1.3. Warehouse
The
warehouse holds raw material and packing material for the manufacturing
process and finished goods. The warehouse is divided into two sections:
Store A and Store B. Store A keeps the raw material and packing
material. All these materials are in the quarantine area until they pass
the quality check. Then these materials are released for manufacturing.
Store B holds finished goods. The finished goods are released from the
store once the quality checks are over. The environmental conditions in
the store areas can differ to suit the products being manufactured. For
example, these can be cold rooms, chilled rooms, or air conditioned
according to the requirement for raw material and finished goods.
The
goods movement from the stores is in one direction. There is no back
tracking or criss-crossing of material movement on the layout. As shown
in Figure 5 for material movement, the raw and packing material entering
Store A move through the manufacturing process and reach Store B as
finished goods. Therefore, in order to prevent cross contamination,
personnel movement needs to be restricted or controlled and thus
changing room facilities need to be placed at appropriate locations.
4.1.4. Utility Area
This area hosts all utilities and the engineering department of the organisation. Utility equipment includes components such as air handlers for the heating, ventilating and air conditioning (HVAC) system, boilers, air compressors, chillers, and water purification plants that support the manufacturing process. According to the observations, there is no need for frequent direct access to the secondary packing area from the utility area. Therefore, sealed type emergency exit doors can be fixed if required.
4.1.5. Administration Area
This area holds the facilities such as the main administration office, changing rooms for employees, canteens, washrooms, toilets, and first aid rooms. Employees use the changing room in the administration area and wear the factory uniform and sanitise their hands before entering the secondary manufacturing area. Employees enter the stores from a separate entrance after changing their uniforms. This area is not treated as a production area. Offices are also located in this area and the layout can be designed so that the offices have a direct view of the manufacturing area through glass panels. This facilitates good visibility of the production area while preventing cross contamination. Visitors' viewing area of the production process can also be located in this area.
4.1.6. Personnel and Goods Movement
Employee
movement within the facility in the diamond model is shown by arrows in
Figure 6. The employees working in different sections can access them
through the administration area. Those who work at the primary and
secondary manufacturing areas can enter through air locks. Access to the
primary manufacturing area is only through the secondary manufacturing
area.
Goods movement in the diamond model is depicted in Figure
5. Goods first reach the warehouse as raw and packing material. These
are stored in Store A. Then they move towards the secondary
manufacturing area. Removal of packaging, weighing, and batch
preparation takes place in this area.
Then the raw material ready
for processing is moved to the primary manufacturing area. Once the
manufacturing process is complete and primary packing is finished, the
final product moves into the secondary packing area. Then secondary
packing takes place in the secondary manufacturing area. This includes
tasks such as pasting labels, printing information, packing into
shippers, shrink wrapping, and palletising. Then the finished product
moves to Store B, and it is ready for dispatch.