The food industry produces many different types of food that require many different processes and methods of food handling. There is no one particular style of conveyor that caters for all applications but in terms of design principles, the scope of design choice narrows when considering hygiene. ENE applies the best principles to its conveyor designs.
Various types of conveyor offer different attributes that can be encountered within the food and pharmaceutical industries;
- Plied belted (General conveying throughout)
- Solid or homogeneous belted (Direct food contact)
- Modular plastic belted (General conveying throughout)
- Modular steel belted (Bakery industry)
- Wire belted (Extremes of hot and cold)
- Round or shaped profile belted (Niche applications)
The over-arching consideration when designing a conveyor for use in the food or pharma sector is one of hygiene. The form, function and materials choice must all feed into the central theme of hygiene conformity. For ENE, the influential EHEDG (European Hygienic Equipment Design Group), EU legislation and HACCP provides the foundation for best practice.
Broad design principles
Hygienic conveyor design encompasses three areas;
- Inspection – All food sensitive areas of the conveyor should be easily inspected. The use of open construction is encouraged. Ease of disassembly such as hinges and guards is vital to facilitate thorough inspection. The use of fasteners that do not require tools to operate should be used.
- Operation – The conveyor must be designed in such a way to minimise contamination from various sources. One example could be placing guarding over sensitive areas or making sure that belts are prevented from shedding material through contact with other parts by fitting tracking guides. Good design practice could also prevent product ‘run-off’ or residue re-entering the food production stream. There are a number of areas that define an excellent food conveyor.
- Cleaning – The conveyor should be designed to be free of blind-spots, grooves, adjacent mated surfaces. There should be no areas that are impossible to clean or that could harbour product, dirt or cleaning media. All surfaces should be smooth and sloped as much as practically possible (generally no less than five degrees inclination). Flat surfaces encourage fluids to lie and for foreign objects to remain.
The European regulation concerning materials in contact with food (EC 1935/2004) lays out the outline requirements for materials suitable for food contact materials. Broadly speaking, the rules are;
- Materials used in food contact must be non-toxic and non-absorbent.
- They must not contaminate or taint the food in any way.
- They must not inadvertently alter the chemical composition of the product.
- Materials in contact must not contain lead, arsenic, cadmium, or mercury.
The most widely used and acceptable materials in modern food conveyors are;
- Stainless steels of different grades offer strength, durability and a strong resistance to corrosion. Framework, fasteners and guards are the main components that use this material.
- UHMWPE is odourless, nontoxic and tasteless. It is highly resistant to most chemicals. It has very low moisture absorption and a very low friction co-efficient. It has a high resistance to abrasion. It is used as wear strip, dead plates or impact areas.
- Polycarbonate is used in applications where visual inspection is required. Polycarbonate is resistant to moderate impact and therefore used to reduce the risk of shattering. Hygienic conveyor design
- PVC is widely used as the main component in conveyor belts for heavier food applications. There are food approved versions that are also oil and fat resistant. PVC belts are relatively inexpensive. They aren’t particularly wear resistant. They can suffer to surface cracking in certain applications and their lifespan is shortened due to eventual loss of plasticisers. They are slightly more resistant to delamination due to their construction.
- Polyurethane is widely used in conveyor belts where more defined performance is required. Abrasion resistance is good as is relative life-span. Costs are about a third higher than PVC. PU belts are more versatile than their PVC counter parts.
- Acetal is used in modular belting types. It has high abrasion and cut resistance. It’s impact resistance is poor.
- Polypropylene is a good all-round material used in modular belting types.
- Polyethylene is a lower cost material used in modular belting types. It offers good low temperature performance. It is resistant to impact but not cut resistance.
Materials to be careful with are;
- Aluminium is not sufficiently corrosion resistant to be considered a suitable material for food machinery use. Occasionally, a zinc coated (anodised) aluminium may be considered but regular inspection will be required to ensure there is no flaking and risk of contamination.
- Rubbers cover a large range of types can be mis-specified. It’s sometimes necessary to provide gaskets for housings or seals for certain applications. Make sure that the rubber used is food approved and suitable for the application. Care should be taken that the type of the rubber is confirmed.
- Plastics cover a large range of types and can be mis-specified. It is vital (particularly in belt selection) that the correct type of plastic material is used. The plastic belt should be food approved both in material type and in construction and form. Certificates will always be available for these items. Aside from certification, the suitability for the application is important. Different types and grades offer different attributes.
Good conveyor design is a combination of understanding legislation, industry best practice and common sense. Quite often, trying to ‘re-invent the wheel’ can have disastrous consequences. Please consult with ENE for further details of its range of market leading products.