Are you new to heat transfer fluids and not quite sure what some of the industry terms mean? Take a look at our most commonly used terms and their definitions below.



Anti-foam additive
Causes air bubbles to break on the surface and prevents the build up of foam. Can also help prevent oxidation. Cannot prevent air entrainment but can speed up the release of entrained air.
An additive to retard oxidation.Anti-oxididants are critical where an application is not sealed from the atmosphere. Oxidation leads to sludge formation and when left unmanaged could cause blockages and lead to system failure.
The ATEX directive consists of two EU directives describing what equipment and work environment is allowed in an environment with an explosive atmosphere. As of July 2003, organisations in the EU must follow the directives to protect employees from explosion risk in areas with an explosive atmosphere
Methods or standards for laboratory proceedures for specific tests
Auto ignition values
Auto ignition or autoignition is the temperature at which an oil will ignite on contact with air
Average Molecular Weight
The Weight of the molecules that make up a fluid.
Batch vent
Process where whole "batch" or volume of thermal fluid is passed through a distilation and condensing process to remove light fractions
Biphenyl is an aromatic hydrocarbon with a molecular formula (C6H5)2
Bulk tankers
Transportation designed to move large volumes of liquid from one place to another
Carbon is a chemical composite that can occur in heat transfer fluid and is harmful to system performance when it is not managed properly
The change in rate of a chemical reaction due to a substance
The formation and then immediate implosion of cavities in a liquid. Cavitation can be a significant cause of wear in engineering
Centipoise and Centistoke
Relates to viscosity of a fluid at a specific temperature
Corrosion Inhibitor
Helps prevent oxidation of metal by displacing water from metal surfaces. Most systems at some point will have some water contamination. Corrosion inhibitors virtually eliminate this risk.
Defoaming agents
Air can become trapped in a system during start-up. Pumping creates air bubbles which can lead to pump cavitations, possibly damaging pumps and other system components.
Density (Specific Gravity)
The ratio of the density (mass of a unit volume) of a substance to the density of a given reference material, usually water
Oil-insoluble materials that result from oxidation/thermal cracking of the oil and contamination from external sources and settle out in system components as sludge and varnish
The main application of diphenyl ether is as a eutectic mixture with biphenyl, used as a heat transfer medium. This mixture is well-suited for heat transfer applications because of the relatively large temperature range of its liquid state
Distillation Range
The difference between the temperature at the initial boiling point and at the end point of a distillation test
Dangerous Substances and Explosive Atmospheres Regulations 2002. DSEAR puts duties on employers to protect people from risks to their safety from fires, explosions and similar events in the workplace as a result of dangerous substances. Dangerous substances are any substances used or present at work that could, if not properly controlled, cause harm to people as a result of a fire or explosion
FDA certified
Food and Drug Administration
Fire Point
The temperature at which the fluid will sustain a fire if ignited by an outside ignition source.
Flash Point
The temperature at which the vapours produced from a fluid will ignite (flash off) with the presence of an ignition source and oxygen (the fluid will not burn at this point). The flash point is important from the viewpoint of safety; however it is quite common for heat transfer systems to be operated at temperatures above the flash point of the fluid
Food grade
A fluid that is safe for incidental food contact in food processing plants and pharmaceutical facilities
A colorless, sweet liquid, C2H6O2, used as an antifreeze and as a solvent
HAZOP Survey
A hazard and operability study (HAZOP) is a structured and systematic examination of a planned or existing process or operation in order to identify and evaluate problems that may represent risks to personnel or equipment, or prevent efficient operation
Heat Capacity (Specific Heat)
Or thermal capacity, is the measurable physical quantity that characterises the amount of heat required to change a substance's temperature by a given amount
Heavy ends
High boiling point, intert carbon and sludge like products resulting from thermal cracking and oxidation of an oil
HT1 accredited
Is the specific accreditation given to some heat transfer fluids that meet exacting standards of NSF International, the organisation which certifies products for food, water and consumer goods
An organic compound consisting entirely of hydrogen and carbon
Having an affinity for water.
Incapable of dissolving in water
A substance that slows or prevents chemical reactions, such as oxidation or corrosion.
IBC containers
Intermediate bulk container is the container used for transport and storage of fluids and bulk materials
ISO 14001
The core set of standards used by the Company (monitored by an independent third party) for maintaining an effective environmental management system
ISO 9001
The quality policy adopted by the Company (monitored by an independent third party) to ensure that the highest standards of efficiency and effectiveness are achieved and maintained
Light Ends Removal Kit // Distilation loop modification to remove light ends and improve flash points
Light ends
Low boiling point, volitile, fuel like material resulting from thermal cracking
Maximum Bulk/Use Temperature
The Heat Transfer Fluid's highest average temperature
Maximum Film Temperature
Maximum Film Temperature is the highest temperature a fluid experiences in the system
Modified terphenyls
Terphenyls are a group of closely related aromatic hydrocarbons, also known as diphenylbenzenes or triphenyls
NSF accredited
NSF International is the organisation which certifies products for food, water and consumer goods
The process of combining with oxygen and temperature. All petroleum products are subject to oxidation to some degree. The reaction increases with rise in temperature. Oxidation produces oil-insoluble oxidized materials, which result in viscosity increase and deposits
Oxidation Inhibitor
A chemical additive that minimises the formation of harmful acids that form when a fluid is subjected to air at elevated temperatures.
Oxidation Stability
Ability of a lubricant to resist natural degradation upon contact with oxygen
Oxidative Degradation
Degradation which is caused by exposure to oxygen
Pour Point
The pour point of a liquid is the lowest temperature at which it becomes semi solid and loses its flow characteristics
Pour Point Suppressants
Prevent insoluable wax molecules in oil at colder temperatures. Particularly useful for paraffinic oils. Allows you to pour an oil at colder temperatures.
Registration, Evaluation, Authorisation and Restriction of Chemical substances, or REACH for short, is a legislation passed by the European Union in 2007 with the purpose of enforcing the use of harmonised safety information for chemical substances
Sample analysis
Statistical analysis of data collated to determine the quality of a heat transfer fluid
A range of tests undertaken to determine the quality of an oil or fluid
Seal and Gasket Extender
An additive that conditions seals and gaskets to help keep them from drying out and failing.
Service agreements
A planned maintenance programme designed to prevent replacement of high cost capital equipment or loss of production and output
System flush
Cleaning of the heat transfer system and the fluid
System fouling
Result of carbon deposition on coil, pipework and heat exchanger system interiors as a result of heavily degraded thermal fluid
(Total Acid Number) Organic acids are formed when a fluid comes in contact with oxygen at temperatures over 65 degrees centigrade, TAN levels are a means to show the extent of which a fluid has been oxidised using a titration test. The rate of oxidation is minimal under 65°C (149°F) however as the temperature climbs the effects of oxidation are exponential. It is an industry accepted standard to assume the rate of oxidation doubles for each 10 degree increase above 65°C (149°F)
Thermal Conductivity
The property of a material's ability to conduct heat
Thermal cracking
When heat is applied under pressure and breaks larger molecules into smaller molecules
Thermal degradation
Thermal degradation or thermal cracking is the breaking of carbon in the fluid molecules. In heat transfer, the two types of degradation are known as "low boilers" and "high boilers". If thermal degradation occurs at high temperatures - greater than 400°C (752°F) - the effect is not only to break carbon but to form coke. In this case, fouling of the heat transfer surfaces is rapid and the system will soon become inoperable.Low boilers will decrease the flash point and viscosity of the fluid and increase its vapour pressure. High boilers will increase the viscosity of the fluid but begin to form solids which can foul the heat transfer surfaces once their solubility limit is exceeded.
Thermal Expansion
Is the tendency of fluid to change in volume in response to a change in temperature. Heat transfer fluids change in volume according to temperature. Volume increases when heated and decreases when cooled. This information is helpful when trying to size an expansion tank; typically, an expansion tank should be ⅓ full when cold and about ½ full when hot
Thermal fluid
Thermal fluid or thermo fluid or thermic fluid refers to a branch of science and engineering and to the transfer of heat via a liquid or vapour where temperature, flow rate, phase transition, pressure, volume, and density all play an important role.
Vapour Pressure
The pressure exerted by a vapor in equilibrium with its solid or liquid phase
A measure of a fluids resistance to flow. A higher viscosity is essentially a thicker fluid.  a fluids viscosity is its VI (Viscosity Index) or how a fluids viscosity is affected by temperature. It’s a measure of the rate of change of viscosity with temperature. In lubricants a high VI is desirable to maintain a relatively consistent viscosity throughout the useable temperature range. In heat transfer fluids a lower VI is more desirable in order to allow the fluid to thin out ( reduce viscosity ) with temperature increases. This allows for more efficient thermal transfer properties