Factory layout and design for food safety
It is a scientific discipline describing
handling, preparation, and storage of food in ways that prevent food-borne
The food processing industry is a subset of
the manufacturing sector with unique challenges. Among these, ensuring food
hygiene and preventing contamination are two issues of prime importance. Hence,
designers have to overcome such challenges when designing facilities suitable
for food processing. The paper formulates a model that simplifies the layout
planning process for the food processing facilities (FPF) in order to help the
designers. A generalized framework that helps to visualize the Facilities
Layout Problem (FLP) was initially developed. A layout model for FPF was then
developed considering the unique features that need to be present in the
layout. The model classifies the areas of FPF into five: primary, secondary,
utilities, warehouse, and administration based on the activities and the level
of risk present in food processing. It further proposes specific locations for
the five sections in the factory. The framework and the model showed promise in
its implementation. However, the approach and the layout model need to be
evaluated in further cases in order to ascertain their usability and
Food safety and hygiene therefore play a
major role in industry and food quality is the result of numerous factors such
as physical, biochemical, and microbiological characteristics. Therefore, it is
imperative that these factors are considered in layout design in the food
processing industry. Many practices such as the hazard analysis and critical
control points (HACCP) or good manufacturing practices (GMP) attempt to ensure
food safety and hygiene requirements in the food manufacturing process. In
order to align with these requirements, layouts need to focus on segregating
the work area to control hazards and prevent contamination of the products
being manufactured. This focus will ensure that the layouts comply with the
requirements of the food industry and avoid modifications required later that
usually result in additional costs.
A plant layout is designed to
obtain a physical arrangement of different entities of a facility that most
economically meets the required output, in terms of both quantity and quality.
A plant layout ideally involves allocation of space and arrangement of equipment
in such a manner that overall operating costs are minimized. Three main types
of layouts, product layout, process layout, and group layout, are commonly
encountered in manufacturing systems.
In order to assess the efficiency of a layout, key
performance indicators (KPIs) are used. The commonly used KPIs are travelling
distance (m), distance travelled times weight (kg), goods movement, personnel
movement, overall equipment efficiency (OEE), energy efficiency, and waste
generation. However, KPIs suitable for the food manufacturing need to be
identified and incorporated into the assessment criteria of layout efficiency
in order to address the food safety considerations. This also enables effective
determination of the efficiency improvement of the food manufacturing processes
when layout modifications are performed.
The primary concern of food manufacturers is to produce
something that is wholesome and safe, that is, free from pathogenic
microorganisms and chemical and foreign body contamination. Food items are
perishable and become unsuitable for consumption with time. Although it cannot
be prevented, one aim of food processing is to slow down the rate of
deterioration by selecting appropriate methods of processing, ingredient
formulations, packaging, and storage conditions . In order to make food items
safe for consumption, food processing plants take measures to eliminate the
possibility of microbial, chemical, and physical contamination. Thus, it
becomes a key factor of concern, and layout design should essentially help to
prevent direct and cross contamination of the products being manufactured.
Hence, the layouts of the food processing factories have to be designed to meet
food safety requirements on top of production efficiency. This is the main
envisaged difference between the layouts of food processing and other
manufacturing plants. Thus it can be concluded that the food processing plants
add a new dimension to the common layout design problem.
Quality Standards Applicable for the Food Processing
Many guidelines are available to regulate the food
manufacturing processes. In the food processing sector, Quality Assurance (QA)
systems are used to improve quality and reduce costs whilst HACCP programs are
specifically deployed to assure food safety . Based on management principles,
HACCP and GMP have been implemented to help plants to maintain high levels of
hygiene. HACCP systems establish process control by identifying points in the
production process that are most critical to monitor and control in terms of
contamination . It is widely recognised in the food industry as an effective
approach to establish good production, sanitation, and manufacturing practices
that produce food items that are safe to consume . Therefore, it can be concluded
that QA and HACCP implemented in concert facilitate improvements in both
production efficiency and product safety .
Considering the above factors, an area that needs attention in the
food processing industry is the relationship between hygiene and the layout of
the processing plants. Aspects of food hygiene have been addressed in different
disciplines and a considerable amount of knowledge is available. However, this
knowledge is not systematically linked to the evaluation and design of layouts
for food processing. The literature on layout planning has thus far
inadequately addressed the influence of hygiene factors on the specific nature
of the food processing companies.
A systematic process has to be followed in layout design to ensure
that the design is in accordance with the production requirement. Therefore,
sufficient information to start a layout design process is crucial. The layout
design or modification problem becomes even more difficult to resolve when
there are practical limitations such as demolition of existing walls and
structures, adding more space to an existing facility, accommodating the
complexity of a manufacturing process, and maintaining capacity and flexibility
of a plant. The cost of implementation of a new layout and the available time
for execution are other limitations often overlooked in the literature. Hence,
there has to be greater understanding of these limitations when designing a
The proposed framework illustrated was thus developed to support
the industrial designers to obtain the required information in a systematic
manner. It consists of five main steps. Step A is concerned with the capacity
of the required machinery. Step B addresses the issue of design parameters of
the manufacturing process. Step C helps to generate space requirements for
different sections of the layout. StepD considers the layout alternatives and
Step E is dedicated to the selection of the most practical layout from the
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 11.
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 11.
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
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 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.
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.
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.
Personnel and Goods Movement
Employee movement within the facility in the diamond model
is shown by arrows .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.
Evaluation of the Framework and Model
The proposed framework for layout design and the proposed diamond
model were used to rearrange a facility for food processing. The factory packs
bulk malted milk powder into three stock keeping units (SKUs): Sachets, jars,
and bag in box (BIB).
Usability of the above framework and the model was tested and
validated during this layout renovation project. The framework was used to
obtain the layout design requirements and consider other necessary parameters
for the layout design. The diamond model was then used as the guideline in
designing the layout. Stages of the manufacturing process were identified as
primary, secondary, warehouse, utility, and administrative. Machinery and
furniture were identified for these specific areas.