BUS606: Operations and Supply Chain Management

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 $(n=4)$ 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.