Heat transfer systems: myth versus reality

Jon Lawson

Proactive maintenance and staff training are vital for heat transfer systems, says Clive Jones

Believing without question some of the widely circulated myths about heat transfer systems can lead to system inefficiency, non-compliance with legislation and expensive downtime. Here, we explain the truth behind four common misconceptions about heat transfer systems.

In the chemical and process industries, many plant managers use thermal fluid systems in processes that require indirect heat during operation. Historically, manufacturers used steam systems to fill this role, but in recent years, thermal fluids have become more popular due to their benefits in safety, efficiency and less intensive and costly maintenance requirements. Today, thermal fluid systems are used to provide heat in many solar, pharmaceutical, chemical and food and beverage processes.

A new heat transfer system is a worthy investment for many applications, but to get the most out of a system, plant managers need to know how to operate and maintain it, without falling into the trap of believing common misconceptions. 

No maintenance? No problem.

It is a common belief that once the system is installed, it can run indefinitely with little maintenance. In truth, thermal fluids have a finite lifespan and manufacturers should take care to prolong fluid life. This particular myth is perpetuated by operators that have run a thermal fluid system for many years without major problems. However, by leaving the system unattended for long periods of time, manufacturers put themselves at risk of failing to meet mandatory regulations and incurring expensive downtime.

Although it is true that thermal fluid systems require considerably less maintenance than steam heat transfer systems, it is imperative that monitoring and maintenance is carried out on the system and the fluid. To meet the Dangerous Substances and Explosive Atmospheres (DSEAR) regulation and the Explosive Atmosphere Directive (ATEX 137), it is recommended that the operator performs at least one site survey a year.

However, to keep the system in the best possible condition, plant managers should ensure that thermal fluid is sampled more often than this. Thermal fluid degrades over time and the degradation processes can lead to carbon and acid build-up and a low flash point, which can cause system inefficiency, health and safety problems and downtime. The only way to get an accurate representation of the condition of a thermal fluid is to carry out a hot, closed representative sample. Once this is done, appropriate action can be taken to keep the system safe. However, anyone carrying out the sampling and follow-up actions needs to be properly trained in heat transfer system operation.

One is all you need

Heat transfer systems should be operated by trained, knowledgeable members of staff. However, many companies make the mistake of believing that one trained member of staff, such as the plant manager or health and safety manager, is sufficient. In reality, it is vital that all staff operating the system understand the importance of taking frequent samples and carrying out surveys by a trained expert.

Training can also open a company’s eyes to the importance of taking representative hot, live samples to ensure the resulting flash point analysis is correct. An inaccurate sample can artificially inflate the flash point, which would indicate the system is safe when it may not be. Having the correct reading allows the company to perform planned maintenance, minimising the risk of unplanned downtime.

Trained staff can perform the day-to-day set up and shut down operations of the system. Staff can also undertake walk-around checks to make sure that gauges are working correctly, pipes are insulated and gaskets are not leaking or worn out. More than one member of staff should also be trained to understand the requirements detailed in DSEAR and ATEX regulations to ensure compliance. In the pharmaceutical and food industries, there are various additional regulations that staff must get to grips with.

Sit back and relax

Maintenance is essential for an operational heat transfer system. Despite what some manufacturers believe, this maintenance should be proactive rather than reactive. It is better to take the approach of regular sampling and corrective planned maintenance, instead of waiting for a problem to interfere with an operation, which can be costly.

Plant managers should ensure that heat transfer fluid sampling takes place at least quarterly and that it tests for all necessary parameters. For example, Global Heat Transfer recommends an 11-point test to make sure that nothing is missed. Without proactive sampling, there can be a carbon or acid build up in the system, which can lead to a lack of flow or hotspots. Carbon is a natural insulator, so operators can encounter problems with uneven heat transfer that impacts production efficiency and increases energy costs.

If the system is left for longer, the carbon build-up in the pipes can reduce the life span of a thermal fluid so dramatically that the only solution is to shut down the entire system, flush out the oil and re-fill it with new oil. If the problem is caught early, the manufacturer can simply dilute the thermal fluid or apply another intervention which is considerably less expensive than replacing the oil. It is important that manufacturers do not sit back and wait for fluid condition to deteriorate, which can result in damage and system failure and potential fire hazards.

You’re on your own

Many manufacturers believe that guidance on heat transfer systems is difficult to access, but there are lifecycle management programmes available that provide detailed training for staff and help reduce the associated risks and financial costs. To overcome the thermal fluid sector's myths, plant managers can make sure several staff members are trained, maintenance is proactive and they know where to turn if they do encounter a problem.

Clive Jones is MD of Global Heat Transfer

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