Synthetic fluids benefit over mineral oils

As the price gap closes between the more expensive synthetic heat transfer fluids and mineral oils, the benefits of synthetic over mineral oils now have a greater significance.

Historically, synthetic heat transfer fluids have been used in high temperature systems, where degradation of mineral oil based fluids has been rapid and therefore costly.

As the price gap closes between the two types of fluids, the benefits of synthetic over mineral oils now have a greater significance.

MacDermid UK have been distributing Therminol synthetic heat transfer fluids for over 20 years in partnership with Solutia.

This past year has seen a significant rise in sales of Therminol SP as a replacement for mineral oil based fluids.

Therminol SP is a synthetic heat transfer fluid for use in the liquid phase for indirect heating, and is part of a family of fluids which have operating temperatures of between -115 deg C to +400 deg C.

The benefits of Therminol SP over mineral oil based products are significant: * Lower density at high temperatures with Therminol SP result in lower energy requirements, and in today's climate of increasing energy costs, this saving should not be overlooked.

* Mineral oil based fluids can become difficult to pump at low temperatures.

The low kinematic viscosities of Therminol SP are helpful for easy winter start-up.

* Heat transfer coefficients of Therminol SP at all temperatures are equivalent to, or better than, mineral oils.

* Therminol SP heat transfer coefficient remains stable with time (no increase of Kinematic Viscosity).

* Safety considerations - the safety margin between auto ignition temperature and bulk temperature is lower for mineral oils; this can lead to an increased risk of fire for those companies using mineral oils at the upper working temperatures.

Used mineral oils have lower flashpoints by DIN EN 22719/ASTM D93 (Pensky Martens Closed Cup Method) Mineral oils have flashpoints which decrease by usage over time.

This must be considered by safety engineers when they are making the HAZOP evaluation.

Therminol SP is resistant to forming polymers, tars or carbon (which could remain in the system).

These tars or carbon deposits can build up on system heaters and over time the drop in efficiency can be significant.

Therminol SP creates less high boilers than mineral oils and they have a lower molecular weight than those formed from mineral oils, therefore they are more soluble and have less impact toward increasing viscosity.

This again means that over time the life of the fluid can be significantly longer than mineral oil based heat transfer fluids.

Solvency power of Therminol SP is higher than that of mineral oils and comes from specific aromatic chemistry.

High boilers are soluble in Therminol SP and much less soluble in mineral oils.

This is the reason for coke and sludge formation in mineral oil systems; again impacting the life of a fluid and extremely detrimental to the overall use of heating equipment Infra-red absorption test shows that fresh fluids (mineral oils and Therminol SP) do not have carboxylic groups, while after usage mineral oils show presence of carboxylic groups (corrosion starters).

Therminol SP does not.

The impact of this has been seen in systems that have failed due to the onset of corrosion caused by the build up of carboxylic based by products.

MacDermid offer a free analysis service for all of its range of heat transfer fluids.

This analysis can be used to evaluate the condition of a fluid prior to changeover and then to monitor its condition over the life of the fluid.

Put simply, as the costs of mineral oils increase, the price difference between these and synthetic fluids narrows.

Therefore, when viewed over the life of the fluid the cost saving from switching to Therminol SP can be significant.

Energy costs decrease, pump wear decreases, corrosion potential is minimised, carbon build up and tars decrease and the life of the fluid is maximized.

* Experience/references Therminol SP - MacDermid have a great deal of experience of replacing fluids across many application areas such as plastics injection moulding, rotational moulding, oil exploration, pharmaceutical manufacture and fibre board production.

Solutia have supplied Therminol SP all around the world, in all major industrial sectors.

Some of the largest global manufacturing companies use Therminol with great success.

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