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Top tips for effective heat transfer

03 August 2022

Clive Jones offers advice on how effective heat transfer system management can help food and beverage manufacturers reduce the risk of contamination while increasing productivity. 

According to legal firm RPC, 203 unsafe food products had to be recalled in 2019 in the UK, due to allergy issues, unsafe materials entering the food and breaches to health regulations. Manufacturers need to take every precaution to prevent contamination, particularly when working with thermal fluids. 

On the rare occasion heat transfer fluid can contaminate food. For example, if the system has a leak. Some food manufacturers opt for steam-based heat transfer to avoid this issue all together ? but is this the best option?
Steam versus thermal fluid 
While the distilled water in steam heat transfer systems ensures that incidental contact with products will not lead to contamination, steam-based systems are not always the safest option.

Steam heat transfer systems operate at very high pressures of about 85 bars or 8,500 kPa. If the steam reaches a critical pressure and the system has no way to vent, it can cause pipes, valves or seams to burst. Consequently, extremely hot steam or shrapnel from the pipes may harm employees and damage the surrounding infrastructure. Corrosion in pipes is also common in steam-based systems, so regular maintenance is needed to reduce unexpected downtime.

Alternatively, thermal fluid systems pose many advantages over steam based systems in their efficiency, safety and precise temperature control. Thermal fluid systems operate at atmospheric pressure and are well vented, decreasing the strain on pipes and the risk to life and infrastructure. Decreased risk improves the health and safety of the workplace and means that downtime to replace piping can be planned into the production schedule.

Factors to consider 
If food and beverage manufacturers use a standard heat transfer fluid and there is incidental contact with a food product, the whole batch will have to be scrapped. It can be costly to dispose of products and can damage a company’s reputation if the product has to be recalled. The best way to prevent the risk of contamination is to invest in a food-grade fluid.

Food-grade thermal fluids must carry a HT-1 certificate, granted by the US Food and Drug Administration (FDA) or the NSF International, to be approved for use in food processing. They are typically colourless, non-toxic, non-irritating and non-fouling, so if they do come into contact with food and consumers, they will lead to lower recall rates. Manufacturers should also select a fluid with a high flash point — the temperature at which a fluid produces enough vapour to be ignited. The higher the flash point, the lower the risk of fire.

Fluid maintenance 
Thermal fluids will degrade over time, especially when operating at high temperatures for long periods of time. Fluid degradation can cause a build-up of carbon and other by-products in pipes, reducing heat transfer efficiency that can cause products to be cooked inconsistently. If the fluid is properly maintained manufacturers can slow down the degradation process and reduce the risk of unplanned downtime.

Heat transfer fluids should be sampled regularly to ensure compliance with the Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR). Engineers should take samples of hot and circulating thermal fluid to get an accurate representation of the fluid’s condition. The sample is then sent for specialist analysis to measure the flash point temperature, carbon levels and the TAN, which indicate the fluid’s condition. 

Product recalls can be a costly and damaging process to any food manufacturer. While steam has historically been the most popular choice for indirect heat transfer, food-grade heat transfer fluids have climbed ahead in recent years because of their increased safety and more manageable maintenance.

Clive Jones is managing director at Global Heat Transfer.

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