How do you take your whisky? Serious whisky drinkers insist that it tastes better diluted with water — and they might be right. Whisky’s distinctive taste comes from guaiacol, which has a part that likes water and a part that doesn’t. According to the journal Scientific Reports, diluting a whisky from 45 per cent to 27 per cent boosted the density of guaiacol at the surface by more than one third. Dilution has its benefits, both in whisky and in heat transfer fluid. Here, Clive Jones, managing director of thermal fluid specialist Global Heat Transfer, explains how to dilute thermal fluid and the benefits.
When working in applications that require indirect heat transfer, engineers have the option to select a heat transfer fluid that is matched to the industry, system, and temperature requirements. If properly maintained, heat transfer fluids will operate at and maintain high temperatures for many years before starting to degrade. However, if left unattended, or operated at higher temperatures than the stated operating range, the rate of degradation will increase.
Thermal oil will break down by both oxidation and thermal cracking. All systems are designed to run using Ph neutral fluid to avoid excessive corrosion. When heated fluid is exposed to air, acid (TAN) levels start to increase, oxidation occurs and the heavy ends, or carbon, instantly start to form. Carbon adversely affects pipework, the heater coil, and the expansion tank.
When thermal fluid is overheated beyond its stated operating range, thermal cracking occurs. The fluid’s molecules break down into smaller particles, or light ends, which have a low boiling point and are very volatile. Heavy ends are another product of thermal cracking, which are carbon molecules that cause fouling in the system, reducing heat transfer efficiency.
Fluid is not visible once it enters the system, so an issue may go unnoticed until it negatively impacts production. For example, if food products cook inconsistently or chemicals do not blend, it is likely that the fluid has degraded. When this occurs, manufacturers must cease production, act quickly to understand the condition of the fluid and take steps to return to production.
Thermal fluid does not go from being fit for use to unviable overnight. When a system operates properly, degradation is steady — it is only as the fluid approaches the end of its practical working life that there is a gradual curve, which eventually drops off very sharply. Specialists refer to this as the degradation curve.
The gradual curve before the sudden drop is a grey area where a fluid can be managed to extend its lifespan. Without regular and preventative maintenance, manufacturers will struggle to know when this sudden drop in performance will occur.
By taking regular samples, manufacturers can monitor the condition of the thermal fluid and track degradation. To ensure the sample is representative of the fluid in the system, engineers should take samples using the closed method, and while the thermal oil is hot and circulating.
Thermal fluid experts will carry out fluid analysis, conducting eleven tests to determine its condition. If any one or a combination of the eleven tests carried out is outside the acceptable limits, based on typical data, it is an indication that the fluid is beginning to degrade.
The sweet spot
Proactive maintenance enables manufacturers to detect when fluid is in the early part of the degradation curve and take action to extend its lifespan. Diluting existing fluid with virgin heat transfer oil will remove degradation by-products and increase heat transfer efficiency.
Diluting fluid by topping up will reduce operational and capital expenditure costs associated with shutting down production, cleaning the system and replacing the fluid. Intervening at this time will also prevent downtime, reduce the risk of associated production losses, and reduce the environmental impact of the heat transfer fluid.
Once diluted, carbon and heavy ends are significantly reduced and fluid can operate efficiently at its intended temperature, removing the need to turn up the temperature to maintain production. As a result, manufacturers may see a reduction in energy usage and therefore costs.
While dilution reduces light ends, it does not address the cause. Instead, manufacturers should consider a long-term solution, for example by installing a Light Ends Removal Kit (LERK) to continue managing light ends and flashpoint. Choosing to maintain existing fluid rather than replacing it also reduces the environmental impact and cost associated with removing, transporting, and processing waste.
Dilution is a cost-effective and durable option, but only when fluid is in the early part of the degradation curve. After the condition of the fluid has significantly deteriorated, dilution is no longer a viable alternative. Diluting a degraded fluid would be a very short-term solution because the system would not operate at optimum capacity.
The best thing to do when thermal fluid reaches the end of its lifespan is to flush and clean the system before refilling it with fresh heat transfer fluid.
Diluting thermal fluid
When lab analysis shows that fluid dilution is the best maintenance option, they can consult a thermal fluid specialist for support. The specialist engineers will consider the site, application fluid type, system type and the rate of fluid degradation to calculate how much virgin thermal fluid to add to the system.
By implementing a preventative maintenance programme, such as Thermocare®, manufacturers can gain expert support when carrying out regular thermal fluid sampling and analysis. By better understanding fluid condition, manufacturers can notice the first signs of degradation and plan maintenance, such as dilution, before issues begin to negatively impact production and operating costs.
Whether it’s extending the lifespan of heat transfer fluid or improving the taste of your favourite tipple, dilution can offer a range of benefits. For more advice on proactively maintaining your thermal fluid, contact Global Heat Transfer.
About Global Heat Transfer: Global Heat Transfer is a thermal fluid specialist, providing heat transfer engineering assistance and thermal fluid supplies. Services offered include sampling and analysis, 24 hour delivery of premium quality thermal fluids, system drain down / cleaning / waste management, planned maintenance programs and a broad portfolio of affiliated system design and installation services. It is part of the Global Group of companies.