How do you maintain thermal fluid system assets to prevent risk of explosion?

Jon Lawson

An estimated 3,000 companies within the UK’s process industries alone operate thermal fluid systems to transfer heat around their manufacturing plants.

Legislation stipulates that these firms must proactively monitor and maintain their thermal fluid system assets to prevent the risk of fire or explosion.  

The implementation of a continuous risk assessment and preventative maintenance programme can help firms to save money as well as lives.

And the first critical part of a successful programme is to regularly monitor the condition of thermal fluid.

The heat transfer media used in thermal fluid systems are typically mineral or synthetic oils. 

A system’s operating temperature is invariably higher than the ‘closed cup flash point’ of the media - the minimum temperature at which, in the presence of a source of ignition, such as light switches, pump failure or sparks, the fluid’s vapours will ignite.

Where heat transfer systems operate under high pressure, any leaks from the pipework at points such as flanged joints, valves and connection points, can create mists or sprays, which result in the creation of an explosive atmosphere outside the system.

Most thermal fluids operate above their flash points, and the systems that contain them must therefore be treated on a risk assessment basis.

Whether inside or outside heat transfer systems, on ignition, volatile atmospheres result in fires and explosions, and European ATEX (Atmosphère Explosible) legislation - implemented in the UK via DSEAR (Dangerous Substances and Explosive Atmospheres Regulations) - stipulates requirements for the protection of workers against such incidents arising from the presence of hazardous substances in the workplace. PUWER (Provision and Use of Work Equipment Regulations) dictates that all installations, including thermal fluid systems, are operated correctly and properly maintained.

Although most companies are aware that heat transfer systems operating above the flash point of the fluid must be maintained according to legislation, many do not appreciate that organic thermal fluids based on mineral oils will degrade over time. Degradation can cause a fluid’s flash point to decrease, as ‘light’ materials with lower flash points than the heat transfer fluid itself are generated, reducing the flash point of the fluid overall, so that fluids that were not flammable at the operating temperature at installation, eventually become flammable.

The legislation demands that the risks inherent in the use of flammable fluids are assessed and eliminated or reduced via a comprehensive preventative maintenance programme. Regular fluid sampling and analysis is required to indicate when unacceptably low flash points are reached. If necessary, oil must be replaced or conditioned so that a safe flash point is restored.

The formation of explosive atmospheres outside the thermal fluid system following a leak can be reduced via the fitting of spray-protected safe rings.

The importance of legislative adherence cannot be overstated. Although thermal oil fires and explosions are not common, they do occur with avoidable regularity.  During a 10-year period, clients of insurer FM Global experienced 54 fires and explosions caused by thermal oil. In February, 2010, the thermal oil boiler at a wood processing plant in Northern Europe exploded, killing three people.

Use long-lasting thermal fluids

Employing a thermal fluid with a high flash point combined with chemical stability, prolongs the period for which it may be safely used, making it highly cost-efficient.

Such fluids enable companies to operate their systems safely and efficiently at high temperatures long-term, reducing the frequency with which the oil needs to be reconditioned or replaced to ensure that vital parameters such as minimum flash points are always maintained.

In 2016 Thermal Fluid Solutions (TFS) launched TFS Magma Ultima and its food-grade sister, TFS Thermaltrans FGS, two semi-synthetic heat transfer fluids with a flash point of over 2,600.  

Recondition rather than replace thermal fluid

Historically, the only available option for firms whose thermal fluids required flash point restoration was total replacement, but some suppliers are now able to recondition customers’ existing oils to maintain the appropriate flash points. 

TFS provides this service, which offers a quick, cost-effective, environmentally sustainable alternative to total fluid replacement. Its HTfluidfit rigs remove volatile organic compounds (VOCs) from the oil, returning it to a safe condition, extending fluid life by a factor of at least 10, saving customers up to 70% of their thermal fluid costs.

Only a continuous risk assessment approach to thermal fluid system preventative maintenance will ensure safe and efficient operation and ATEX, DSEAR and PUWER compliance at all times.

Although the development of bespoke, comprehensive, continuous improvement plans enable companies to meet legislative standards, the explosion protection documents that form part of TFS’ plans also enable clients to prove their safety credentials to insurers and so reduce their premiums.

Richard Franklin is managing director of TFS

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