Stainless steel belting improves conveyor hygiene

Food conveyor hygiene standards can be increased by at least 10 times, and in some cases by more than 100 times, when stainless steel belting is used instead of modular plastic types, according to research programmes carried out in the UK and USA.

This research established that – under production conditions rather than in the laboratory – stainless steel Flat-Flex belting from Wire Belt Company is more hygienic than plastic belting when conveying vegetables, meat and fish.

Openness of the Flat-Flex design results in less build-up of contaminants than modular plastic belts, as well as making cleaning easier and allowing visual inspection of drive shafts without the need for dismantling. The advantages of stainless steel over plastic, such as polyethylene, polyvinylchloride, polypropylene, and mineral resins include easier and more effective cleaning as well as greater resistance to damage resulting in scratches and crevices that can lead to increased opportunities for attachment and growth of bacteria.

These features make stainless steel preferable to plastic for use where hygiene and ease of sanitation are important, especially in areas where accessibility and extended production runs present cleaning problems.

Easier to sanitise

Research in the UK, using a variety of cleaning agents, shows that with fish and meat Flat-Flex picks up fewer bacteria, maintains a lower level of contamination over time and is easier to sanitise, possibly because the gaps in plastic modular belting cannot be as readily cleaned as the stainless steel belting and harbour bacteria with quicker recontamination of the belt as a consequence. Drive shafts and the undersides of plastic modular belting are particularly difficult to clean in comparison with Flat-Flex belting.

Experiments with meat and fish showed that plastic modular belting tended to contain trapped debris, even after thorough sanitising and rinsing. Experiments with carrots showed that Flat-Flex could usually be cleaned to a satisfactory level with just one clean but plastic modular belting often required a second or even third clean to reach a standard acceptable for production to start.

Figure 1

The increasingly rapid growth in bacteria on plastic modular belting compared with Flat-Flex stainless steel belting, especially after two hours, is shown by results of the study in a controlled environment with chicken meat (fig 1 above) and carrots (fig 2 at the end of this article) after sanitisation with Multikleen.

In the USA, where Flat-Flex is approved by the US Department of Agriculture (USDA), research shows that, when proper cleaning and sanitising schedules are maintained, stainless steel belting reduces the problems of biofilms on product contact and non-contact surfaces.

Biofilms, consisting of microbes and extracellular polymeric substances that protect them from their surrounding environments, can harbour potentially dangerous pathogens and create reservoirs of contaminants that are very difficult to eradicate completely. Once a biofilm is established, bacteria living within it can withstand stronger doses of sanitising agent – in some cases up to 3000 times stronger than unattached cells – and bacteria in biofilms are more resistant to heat. The bacteria can be loosened and contaminate product flowing over the biofilms, with the possibility of product contamination and a potential for recalls being necessary.

Minimise the risks

Because biofilms generally form in crevices and hard-to-reach places, hygienic design of equipment can help to prevent their formation and minimise the risks associated with them as well as improving hygiene levels generally, especially in high-usage and difficult-to-clean areas of conveyor belting.

Wire Belt Company's mesh belts, with between 70 and 85 per cent open framework structure, do not typically need to be removed from the conveyor system for cleaning. However, in applications where removal is required, easy disassembly and reassembly without the need for tools can promote proper cleaning and Wire Belt's recently introduced EZsplice belt re-joining system eliminates the problems normally associated with replacing a wire mesh belt by making re-threading simple and easy.

Other aspects of stainless steel belt design that can help to improve hygiene standards include reduction or elimination of areas such as hinge pins, through holes and link barrels where product or debris can become lodged.

The hygiene benefits of Flat-Flex belting are shared by Wire Belt's new Compact Grid conveyor belt, which is designed specifically to handle smaller, more delicate products. With a 70 per cent open surface area, Compact Grid is extremely easy to clean and maintain and provides optimal performance for processes involving product coating, drainage, and where liquid or air circulation are factors. It withstands the heat from cooking operations, such as conveyorised frying or baking, and transfer of product directly onto a cooling line in high-volume, high-throughput processes.

In addition to the hygiene advantages of stainless steel belting, Flat-Flex and Compact Grid belts also have a number of beneficial features that can help to increase productivity, contain costs and improve overall product quality.

The open mesh on Flat-Flex improves efficiency in cooling, coating, draining, heating and drying applications; its small diameter end rolls and drive rolls mean that even the most delicate products are handled gently and easily with extremely tight transfers; and a non-slip positive drive eliminates the need for complex tracking mechanisms.

Lower operating costs

The very low belt mass reduces power consumption, resulting in lower operating costs, less heat absorption during processing and easier handling. The variety of mesh sizes available enables users to choose the exact degree of openness that combines excellent strength and minimal contact between product and belt.

Flat Flex conveyors can be designed to meet special requirements such as maintaining product separation, minimising point contact and keeping product in line. For applications where belts may curl or "sag" under high heat, belts can be pre-stressed in the opposite direction to maintain a flat surface during operation and prevent belt "sag" during conveyorised frying, for example.

Compact Grid, Wire Belt's latest conveyor belt system, has a lighter weight, open mesh belt design that can outperform many competitive belts. The belt will not sweat, slip, droop, or catch fire like many plastic conveyor belts can.

Long belt life is claimed to result from Compact Grid's rugged framework, which provides maximum strength under significant loads and reduces the number of belt replacements over time. When replacement is necessary, Compact Grid belting is joined or spliced on the conveyor by simply hooking the belt ends together and crimping to close.

Full details of the research results and the hygiene benefits of stainless steel belting are available from Wire Belt Company.

Figure 2