Clive Jones discusses what companies should know when installing a new heat transfer system
The Earth’s water is 97% salty or undrinkable, with another 2% locked in ice caps and glaciers.
Which means just 1% remains for all of humanity’s basic needs – its agriculture, residential, manufacturing, community and personal requirements.
In a thermal fluid based heat transfer system water, salted or otherwise, is unusable and can actually be an early sign of system contamination, which can lead to both accelerated fluid degradation and reduced system lifespan.
Thermal fluids are used in many industries including solar, pharmaceutical processing, food and beverage processing, industrial manufacturing and marine.
The fluids are used in processes that require indirect heat, as well as to derive electricity in concentrated solar plants.
The only downside is that heat transfer fluids degrade over time. Despite their importance to the application, thermal fluids often go unnoticed, but if left to degrade substantially this can lead to significant and expensive downtime.
Despite the propensity of heat transfer fluids to degrade, proper planning, set up and maintenance can improve the fluid's life span. It is imperative that maintenance teams flush and clean a system correctly to remove contaminants before use and treat regular system maintenance as essential to the productivity of the plant.
Maximising the life span of a heat transfer fluid in this way ensures that the set up of a new system is a cost effective investment.
When installing a new heat transfer system, design and planning is of great importance. The designer should select appropriate components for the temperatures the system will be operating such as pumps, pump seals and furnace tubes.
New systems are particularly at risk of contamination because of environmental exposure during building. This exposure provides contaminants, such as water, soil and welding slag, with an opportunity to get into the system and accelerate the thermal degradation process.
Many component manufacturers pressure test their equipment using water as opposed to thermal fluid and this is another cause of contamination in a new system.
Contaminants can also damage other parts of the system, including pumps and seals, so it's essential that contaminants are removed before the virgin heat transfer fluid is added and the system goes live.
A cleaning and flushing protocol can be used to clear contaminants from a new system. During flushing contaminants are suspending in the fluid so that they can be easily removed.
Maintenance teams can also use this process in conjunction with filtration to remove larger particulate matter.
Instead of water, a detergent such as Globaltherm C1 should be used in the flushing and cleaning process. Globaltherm C1 is a detergent combining both flushing and cleaning properties, to remove contaminants such as metals, minerals or lacquers that may have entered the system during construction.
A recent study, by Dr Chris Wright, group head of R&D at Global Group, has shown the importance of testing several parameters when checking for contaminants in a new system.
The new heat transfer system investigated in the study contained particulate contamination with silicon, aluminium, iron, calcium and zinc.
The study also showed that water content does not accurately reflect the presence of all particles in the fluid, only the larger ones. This means testing for water alone is not sufficient for detecting particulate contamination.
Water contamination can be measured onsite and maintenance professionals should monitor it regularly because, not only is water the most common contaminant, but the presence of water can be an early sign of particulate contamination. Our research links increased water level in the system to contamination with larger particulate matter and high iron content, an indicator of rusting.
The results of the study indicated that the flushing and cleaning protocol in combination with a filter is effective in removing water and environmental contaminants, safeguarding the system’s future health.
As well as checking for contamination when the system is set up, it is important to be aware that degradation can occur once the system is up and running.
The processes responsible for this include oxidation and cracking, which also require monitoring to avoiding fouling and corrosion and coke deposits respectively.
There are several parameters that need to be measured to check the health of the heat transfer system.
Cracking, for example, can be measured using a molecular weight test and oxidation can be tested by reviewing total acid number (TAN), measuring the organic acids produced in the oxidation process. This is just the tip of the iceberg though; Global Heat Transfer offers an eleven point test as part of its Thermocare preventative maintenance package to investigate whether all parameters are within defined safety limits.
Preventative maintenance can also improve the operating cost of the system. When thermal fluids begin to degrade, the system becomes more expensive because more energy is required to maintain fluid temperature.
Good maintenance practise can minimise this increased cost and reduce the risk of system downtime and loss of production.
Using a set maintenance protocol means a trail of results can be followed. This reassures the management team that the overall process is effective and secure in the long term.
By keeping on top of heat transfer system requirements and creating a robust maintenance strategy from installation, a plant operator can be reassured that the new system will live a healthy life, without using up humanity’s one per cent of the earth’s water supply.
Clive Jones is managing director of thermal fluids specialist Global Heat Transfer.