Fire and Explosion Hazards with Thermal Fluid Systems

Health and safety incidents relating to thermal fluid systems are unfortunately more common than we might realise, and can be extremely serious in nature. An important health and safety issue which has a direct bearing on the estimated 4,000 UK companies that operate thermal fluid systems has recently come to light. 

The Health and Safety Executive recently issued a prohibition notice to a UK company following a major thermal fluid incident and significantly, following that incident, has identified thermal fluid systems as a fire and explosion hazard. There have been other serious incidents this year. Although not under HSE jurisdiction, there was a recent thermal fluid-related explosion and fire at a German panel products plant which tragically caused 3 fatalities. 

As specialists in thermal fluid systems for 15 years, Derbyshire-based Heat Transfer Systems believes that most companies will be aware that any system that operates above the flash point of the thermal fluid falls under the “Dangerous Substances and Explosive Atmosphere” (DSEAR) Regulations 2002. However, many people are unaware that all heat transfer fluids degrade over time. This degradation can cause the fluid’s flash point to decrease dramatically, so that thermal fluids which were not flammable at the operating temperature when they were initially installed may, over time, become flammable at the operating conditions. The DSEAR regulations require that the risk from dangerous substances (flammable materials) is assessed and eliminated or reduced. Systems need to be put in place to reduce the risk and manage the residual risk. The ATEX directives require the hazardous areas to be identified.

 Regular thermal fluid testing and the results obtained will indicate the physical condition of the fluid and the degree of risk in the event of a fluid release.  However, flash point testing alone is not enough to comply with DSEAR.  Procedures are also needed to change out the thermal fluid, or remove the lower flash point components from the thermal fluid. HTS is concerned that the majority of companies operating thermal fluid systems may not be aware of this. 

From HTS’ experience of numerous systems both in the UK and across Europe, many thermal fluid systems will have Zone 2 hazardous areas as defined under the “ATEX Directive” (1999/92/EC). As such, area classification is required to determine the location and extent of the hazardous areas, together with a full risk assessment to identify the fire or explosion hazards and any actions required to reduce the risk, which must include specialist training for relevant employees. As Alison McKay of PROjEN explained, “Hazardous areas can be present not just where a fluid is handled above its flash point. If the thermal fluid is handled under pressure a mist or spray can be formed, which can form an explosive atmsophere at temperatures below the flash point”.   

PROjEN has been working with HTS to designate the hazardous areas in thermal fluid systems. PROjEN has considerable experience in determining hazardous areas for a wide range of processes, including systems handling natural gas, using the recognised standards (BS EN 60079-10-1 and IP15). PROjEN also has extensive experience of carrying out DSEAR Risk Assessments to determine the level of fire or explosion risk and making recommendations to reduce the risk.

 Graham Field, a director of Elciem Limited, a leading risk engineering consultancy with clients in the manufacturing and insurance sectors, commented:  “It is good news that there is greater awareness of the hazards and risks associated with thermal oil systems, but bad news that a lot of this is due to losses associated with these systems.  Losses are bad news for all concerned.  For a manufacturer, they can result in injury to employees, equipment downtime and lost sales.  For insurers who pay the associated claims this can result in greater risk analysis, more careful risk selection and potentially increases in premiums, restrictions in cover or warranties aimed at reducing risks from specific causes.  Greater risk awareness is the priority for all concerned, and the classification of these systems under DSEAR is one way that this can be achieved.  Using the DSEAR risk assessment, elimination and mitigation methodologies will give owners greater comfort that they are operating their systems as safely as possible and will have the added benefit of being a qualitative approach that demonstrates good risk management to their insurers.” 

Richard Franklin of HTS believes that historically, there has been little regulation regarding the majority of manufacturing installations using thermal fluids. 

“Most systems operate in liquid phase with a pressurisation of below 0.5 bar (g) and as such are exempt from inspection under the Pressure Equipment Directive (97/23/EC). The majority of European installations have used a German standard under DIN 4754 (1994-09) – Heat transfer systems operating with organic heat transfer media – Safety requirements and testing.  At the same time, most thermal fluid heaters are excluded from the ATEX directive as appliances that burn gaseous fuels and are regulated under 90/396/EEC. 

Of greatest significance is that the process and pipeline systems that these heaters service are not exempt. This means that the majority of system users are not aware of their responsibilities under ATEX. Also, many system designers and suppliers across Europe are not aware of their responsibilities, and we believe could be handing over systems following commissioning without the required risk assessments, training and documentation.

References:1.      BS EN 60079-10-1:2009 Classification of areas – Explosive gas atmospheres. 2.      IP 15 Institute of Petroleum; Area classification code for installations handling flammable fluids, Model Code of Safe Practice, Part 15, 3^rd Edition; July 2005; Energy Institute (Inst Petroleum).    

30th June 2010

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