Month: August 2024

Heat transfer systems are widely used in the pharmaceutical industry to indirectly heat and cool ingredients during processes such as bulk drug processing, batch reactions and crystallisation.

As the thermal fluid moves around the system, it transfers heat to or from base, intermediate and final stage products to achieve the required temperatures.

Thermal fluid-based systems pose many advantages compared with steam-based ones in terms of efficiency, safety and precise temperature control. However, not all thermal fluids are created equal and there are several considerations when deciding which heat transfer fluid (HTF) is most suited to a process.

Does fluid choice matter?

Upfront fluid cost may seem like a big consideration but, in the long-term, achieving good return on investment comes from maintaining the fluid appropriately. All HTFs degrade with time, but the speed of this degradation increases if system temperatures consistently exceed the recommended fluid range.

Degradation occurs at elevated temperatures because the bonds that exist between hydrocarbon chains start to break, resulting in a process known as fouling that leads to the production of carbon deposits in the system.

Eventually, sludge starts to build up inside the pipework and reduce the efficiency. The temptation here is to turn the system up to compensate for the reduction in heat transfer.

However, the Arrhenius equation suggests that increasing the temperature by just ten degrees can halve the expected lifespan of a fluid, making the problem worse.

If the thermal fluid has degraded substantially, pharmaceutical manufacturers may start to experience problems in their process and will have to cease production, throw away wasted batches and drain, clean and flush the entire system, causing unexpected and costly downtime.

Operating temperature matters

There is no need to panic, however, as thermal fluids can enjoy a very long lifespan if care is taken to select, operate and maintain them according to the manufacturer’s recommendations.

HTFs each have specific characteristics that ensure they are thermally stable and perform well if operated at the appropriate temperatures.

Even so, manufacturers should always consider their operating temperatures when selecting an HTF to ensure that the fluid can safely and efficiently run at the required temperature. As the Arrhenius equation law suggests, choosing an oil not suited to your process temperatures will cause problems later on.

Chemical considerations

HTFs have different chemical compositions that manufacturers may consider when deciding how suitable a fluid’s properties are for a specific application.

Although mineral based fluids do offer a good trade-off between cost and performance, the popular choice in pharma applications is synthetic HTFs. These have a lower susceptibility to form carbon than mineral-based oils, offer better heat transfer efficiency, thermal stability and a higher resistance to fouling.

If you are looking to operate a system at a high temperature, you might want to consider a synthetic-based fluid such as  LM-15 series and LM-16 series.. Synthetic fluids are known to have better stability at high temperatures than their mineral-based counterparts.

They also have a lower viscosity than mineral-based fluids, so perform efficiently in both vapour and liquid phases. Chemical reactions and crystallisation occur at a range of low and high temperatures, so manufacturers can benefit from choosing a thermal fluid with a broad operating temperature range, such as Globaltherm L and Globaltherm J.

These fluids also have low viscosity that allows the fluid to be easily pumped around the system, improving heat transfer efficiency and reducing production energy costs.

A full fluid life

However, once you have chosen a suitable fluid, you can’t stop there. All thermal fluids will degrade with time, but regular monitoring and maintenance will slow the process.

Implementing a comprehensive thermal fluid lifecycle maintenance plan further supports manufacturers with on-site engineering and thermal fluid management support from experts in heat transfer oil.

Regular thermal fluid analysis can also slow degradation. By taking a representative sample from a system that is hot, live and circulating and sending it for laboratory analysis, pharmaceutical manufacturers can understand the condition of their fluid and plan maintenance accordingly.

Preventive maintenance can help to slow degradation and reduce the risk of carbon deposition and fouling from decreasing the efficiency of the HTF. This way, manufacturers can optimise system performance, reduce energy costs, improve health and safety and decrease unexpected downtime.

The best approach is to implement a comprehensive thermal fluid lifecycle maintenance plan, such as Thermol care 24/7 Live Condition Monitoring.

This cloud-based remote monitoring system uses real-time analytics to monitor fluid condition, sending instant alerts to maintenance personnel on a smart device as soon as it detects any issues that could impact productivity.

Ultimately, a manufacturer must consider the heat transfer performance against their manufacturing requirements. Poor fluid choice can lead to inefficient system operation and accelerated thermal fluid breakdown, which can increase maintenance requirements and mean products are non-compliant.

However, by carefully considering the requirements of the system and the application, manufacturers can make informed choices about their heat transfer fluids and ensure smooth operation throughout the fluid’s working life.

Heat transfer fluid selection can involve complicated, multi-dimensional decisions where factors such as thermal stability,pumpability, pressure requirements, and more must be weighed in an effort to achieve the optimum balance of performance and economy in your particular system. However, you may be able to narrow your range of options with a few basic decisions.

First, choose a synthetic organic fluid, a silicone fluid or an inhibited glycol-based fluid based on your temperature requirements. If your heat transfer application has a maximum-use temperature requirement above 175˚C (350˚F), consider a synthetic organic or silicone fluid. For temperatures lower than 175˚C (350˚F), or if you need freeze protection for a water based system, consider an inhibited glycol-based fluid.

Synthetic organic and silicone fluids are thermally stable at temperatures up to 400˚C (750˚F). While operating at these elevated temperatures, they exhibit vapor pressures much lower than steam, making them more practical and less expensive to use. Fluids with broad operating temperature ranges offer high temperature stability and low temperature pumpability.

Inhibited glycol-based fluids are solutions of water and inhibited glycols operating below 175˚C (350˚F). The concentration of glycol in the fluid directly affects its performance properties.

If an inhibited glycol-based fluid will meet your system’s thermal requirements, you can choose between ethylene glycol- and propylene glycol-based fluids. In most applications ethylene glycol-based fluids are preferred because of their lower viscosity and resulting superior heat transfer efficiency.

However, local regulations or a specific application may require the use of a propylene glycol-based fluid. Propylene glycols are commonly used in applications in which a fluid low in acute oral toxicity is required, for example, where incidental contact with drinking water is possible and in food processing applications.