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Heat transfer fluids (HTFs) are chemicals and therefore interaction with the internal components of a HTF system. Dr Chris I Wright highlights some of the key considerations when buying O-rings. 

Chris Wright is a research scientist whose research focuses on the use and maintenance of heat transfer fluids in manufacturing and processing, which includes food, pharmaceutical, specialist chemicals and solar sectors. (Image: Global Heat Transfer Ltd.)

It is a fact that HTFs and O-Rings will degrade over time. The objective of any buying decision, however, is to avoid their accelerated ageing, which can be monitored through a well-designed preventative maintenance plan. When selecting a new O-Ring it is advisable to work with reputable suppliers and manufacturers as they should be able to provide technical data for every O-ring and more specifically their elastomer properties and characteristics.

Once a suitable O-ring has been identified, it is recommended that before buying an O-Ring, the buyer should consult a reputable supplier / manufacturer regarding its application and to confirm its technical specifications.

Five top tips for any O-ring buyer:

1.   Define the operating temperature of the seal and its compatibility with the HTF currently being used.

2.   For well-known synthetic high temperature HTFs (Therminol 66, Therminol VP-1, Globaltherm, Syntec, Globaltherm, Omnitech, and Dowtherm A) Kalrez O-Rings have the strongest evidence to support their use at continuous high temperature.

3.   Consider the compatibility of the O-Ring with the fluids used to clean and flush a HTF system.

4.   All high HTFs will thermally degrade over time and/or oxidize in the presence of oxygen. These chemicals can also affect an O-Ring’s long-term stability.

5.   Use a routine preventative maintenance programme to monitor a fluid and to plan any corrective interventions. A well-designed programme can also be used to assess seal health.

In summary, when buying new seals consider the chemistry of the O-ring and its compatibility (please see Table as an example) with the existing HTF and its operating conditions. The above 5 top tips along with the expert advice from a reputable supplier / manufacturer and a well-designed maintenance plan, such as theThermocare programme offered by Global Heat Transfer Ltd, will help to sustain the life of the HTF and the HTF system’s O-rings.