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Food Grade Fluids vs Non-food Grade Fluids Analysis

It is reported that there are around 4000 companies operating high temperature thermal fluid systems in the UK and Ireland alone. Roughly one in five of these systems is used in the manufacture of food products. However, the current framework of self-governance and external audits means there is a potential for companies to use thermal fluids not suitable for incidental contact with food.

In this industry report, Global Heat Transfer analyses the benefits of using food grade thermal fluid and establishes why some food and beverage manufacturers opt not to.

heat transfer fluids

Food grade fluids – an industry ‘must’

Heat transfer refers to the transfer of thermal energy. In this process, heat transfer fluids (HTFs) act as a heat carrier between a heater and a heat consumer. This is the basic requirement of a wide range of industrial processes and the principle behind indirect heat transfer plants. Indeed, a recent report estimated that the value of the market in 2011 was $1,684 million and by 2017 this will increase to $2,557 million.

A food manufacturer should source food grade HTFs that are suitable for use in food processing. Food grade fluids carry a HT-1 certificate issued by governing bodies such as NSF International and the US Food and Drug Association (FDA). Any manufacturer that wants to sell into the US food market must abide by the correct standards.

In the case of the NSF, the components of a thermal fluid are compared against the NSF's registration guidelines for proprietary substances and non-food compounds. Based on a toxicological analysis, a HTF can then be registered as HT-1.

The supply of food grade HTFs is highly regulated in Europe and companies must comply with REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) and CLP (Classification, Labelling and Packaging) regulations, which refer to the classification, labelling and packaging of substances and mixtures. Failure to use FG oil in a food application can result in the loss of the manufacturer’s top tier accreditation if the EFSIS (the European Food Safety Inspection Service, part of SAI Global Insurance Ltd.) learns that an inappropriate product is being used.

Furthermore, food grade thermal fluid is a requirement for manufacturers that want to supply to the top supermarkets and fast food chains in the UK, in compliance with the British Retail Consortium's (BRC) global standards.

Members of the BRC include Tesco, Sainsbury's, Asda, Morrisons, Waitrose, Aldi, McDonalds, KFC, Burger King and many more retail giants. Thus, compliance with the standards outlined by the BRC is a must for companies wanting to reach these distributors.

A list of recommended food grade HTFs is also commonly reviewed by insurers and food retailers.

With all these compliance and control standards in place, the lack of commercial awareness is surprising. At Global Heat Transfer, we still meet food manufacturers who are keen to sell to the European and US markets, but are not entirely aware of what mandatory requirements exist for HTFs.

Unfortunately, on an international scale, there are still ways to get around the current regulatory framework and use HTFs that are not suitable should they come into contact with food products. For example, one such justification is that a company can choose to dispose of all products that come into contact with the fluid.

The real problem is that food manufacturers are central to all the external audits and controls mentioned previously, but there is no one mechanism to ensure that food grade HTFs are used in the processing of food.

Hazard analysis and critical control point (HACCP) is an internal Food Standards Agency document used to define the acceptable contamination limits for a food. But instead of using a non-toxic food grade fluid, some manufacturers may choose to dispose of all food that comes into contact with an HTF.

Lastly, an insurer could stipulate the use of a food grade HTF, but confirmation that a food grade HTF is used would be based on a paper-based audit only. Insurers also assess the frequency that an HTF is sampled and chemically analysed to ensure the flash point temperature of the HTF is being managed as stipulated.

However, at no point would the insurer request the HTF to be sampled and chemically analysed to validate documentation.

On a final note, some companies still do not fully appreciate the costs they can incur if things do go wrong with their heat transfer system or if entire batches of products need to be discarded. Better awareness of the complexities of thermal fluid would be beneficial for food and beverage manufacturers, suppliers and the general public.

Recalls of food and beverage products due to contamination concerns have risen significantly over the last decade and the associated costs can be crippling. Not to mention the inevitable dent the incident will leave in the company's reputation.

Food grade vs non-food grade fluids

Food grade vs. non-food grade fluids

Food grade thermal fluids are highly refined mineral oils designed specifically to be used in the processing of food. They are non-toxic, non-irritating and have no odour to ensure consumer safety in the event of a leak or spillage. As you can imagine, this is an essential health and safety measure in the food processing industry.

Food grade fluids consist of a complex combination of hydrocarbons obtained from the intensive treatment of a petroleum fraction with sulphuric acid and oleum, by hydrogenation or via a combination of hydrogenation and acid treatment. A food grade HTF consists of saturated hydrocarbons with carbon numbers predominantly in the range C15 to C50.

A recent test carried out by Global Heat Transfer illustrated that, on average, carbon residue for food grade fluid was lower than non-food grade. 1,223 fluid samples were examined - 280 food grade943 non-food grade. These were taken from 97 customers (24 food grade HTF and 73 mineral HTF) with multiple HTF system lines based at multiple locations in the UK and Ireland.

All identified systems were sampled whilst performing under normal operating conditions. A 500 ml sample of the HTF was withdrawn from the system using a custom designed sampling device. The sampling method ensured a true and representative sample of the HTF was obtained.

The first aspect of this analysis showed that carbon level was 0.10 and 0.23 of the percentage weight for food grade and non-food grade respectively. This reflects a percentage difference of 118 per cent (- 0.12/0.10 * 100). Total acid number (TAN) levels were also lower for food grade HTF (0.13 versus 0.18 - food grade versus non-food grade HTF).

The data clearly showed mean and maximum values for carbon residue and TAN were higher for non-food grade HTF than for the food grade one. Individual data was then explored and linear analysis showed there was a strong positive relationship between carbon residue and TAN for both types of HTF.

The analysis demonstrates the non-fouling nature of a food grade HTF, making it more sustainable and less costly in the long-run.

HTFs suitable for use in food processing are commonly referred to as ‘non-fouling’, which means when they thermally degrade, they produce small carbon particles that are suspended in the liquid. Moreover, the carbon formations are less sticky and this reduces the extent of adhesion to the internal surfaces of a heat transfer system.

It is important to remember that all HTFs undergo thermal degradation over time. At high operating temperatures, the bonds that exist between hydrocarbon chains will start to break and form shorter (commonly referred to as ‘light-ends’) and longer chained hydrocarbons (‘heavy-ends’). Both of these products have consequences for the safety of a HTF system and for HTF sampling.

The build-up of light-end components is a potential fire risk because they decrease the ignition temperature of the HTF. The accumulation of heavy-ends results in the formation of sticky carbon deposits or sludge and can be monitored by analysing the carbon residue in a system.

The same is true for oxidation of a HTF: this leads to the formation of carbon sludge and acids.

Sludge or soft carbon will lead to a carbon coat forming on the internal surfaces of the HTF system and with time this will harden. The insulating effect of carbon means that the HTF system is less efficient: heat transfer rates are reduced resulting in longer heat-up time and lower production rates. Also, the hard carbon deposits work to form hot spots and have the potential to cause heater tubes and electrical elements in the HTF system to burn-out.

The salient point is that routine heat transfer fluid analysis is the only accurate way of assessing the condition of HTFs and predicting when the system needs topping up or flushing.

Ideally, all plants using heat transfer fluids should create a robust lifecycle maintenance plan that contains regular sample analysis and careful flashpoint management and thermal fluid condition maintenance.

Safety can be further enhanced in food and beverage manufacturing by using non-fouling food grade HTFs that have a lower tendency to result in carbon residue than non-food grade HTFs. This will implicitly mean a reduction in maintenance and production costs and should eliminate the unwelcome prospect of discarded product batches.

Thermal fluid condition


Global Heat Transfer's analysis of both food grade and non-food grade fluids revealed the former was less fouling to systems, had a lower carbon residue and lower TAN levels. This means higher safety levels, as well as lower maintenance and operational costs in the long run.

Despite these obvious advantages, some food processing facilities still don't use food grade transfer fluids. We believe food and beverage manufacturers require a higher level of awareness when it comes to the regulatory, environmental and maintenance benefits of using food grade heat transfer fluids in food and beverage applications.

We believe awareness is the key to make food and beverage manufacturing more cost-effective in the long run, while ensuring companies don’t make any unnecessary sacrifices when it comes to product quality and process safety.

Process Industry Informer

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