HELISOL®

Heat accounts for around two thirds of industrial energy needs and almost one fifth of total global energy consumption. HELISOL® heat transfer fluids make an important contribution to the efficient transfer of heat. HELISOL® heat transfer fluids may be used in a broad variety of different applications: in wood and metal processing, oil refineries, chemical, polymer and other industries, as well as in solar thermal applications.

HELISOL® heat transfer fluids are highly stable silicone fluids specifically designed for high-temperature and heating/cooling applications. They provide excellent economic benefits – efficient operation, low maintenance, and precise temperature control. With a recommended operating temperature range of −40 °C to +425 °C and versatility due to their chemical structure, they have an outstanding property profile, which sets them apart from organic materials such as mineral oils and aromatic heat transfer fluids.

Benefits of HELISOL®heat transfer fluids:

  • Exceptional thermal stability
  • Highest max. working temperature: 425 °C
  • Very broad temperature range: -40 to 425 °C
  • Low pour point: < -40 °C
  • Lower hydrogen formation
  • Low fouling potential

HELISOL® in Industrial Applications

HELISOL® heat transfer fluids can be operated in industrial applications to heat up or cool down systems and materials during a production process. Whether for heating raw materials or chemical processes, for drying and cleaning or for converting solar energy into electricity or process steam – HELISOL® heat transfer oils offer economic advantages compared to organic representatives, most important reliable and efficient operation and low maintenance costs.

HELISOL® heat transfer fluids can be used in almost all manufacturing industries:

Chemical and petrochemical industry:

  • Chemical processing, distillation, heating and drying
  • Manufacturing, refining, transporting, and recycling of petrochemical products

Plastic / textile industry

  • Polycondensation and polymerisation
  • Synthetic fiber formulation and processing

Energy generation and conversion:

  • Thermal energy transfer
  • Waste heat recovery

Food and pharmaceutical industry

  • Precise temperature control
  • Heating and cooling applications

HELISOL® in Concentrated Solar Thermal Energy

Concentrated solar thermal energy (CST) is an innovative technology where sunlight is concentrated by parabolic collectors and converted directly into heat. This heat can be used directly for processes or to generate electric power. CST is thus an environmentally friendly alternative to fossil fuels and can make a significant contribution to reducing CO2 emissions. For example, a CST plant in Antwerp using HELISOL® as heat transfer oil replaces annual gas consumption by 500 MWh.

Frequently asked questions

HELISOL® heat transfer fluids are linear, clear, odorless and non-reactive polydimethylsiloxanes with a viscosity range of approx. 5 to 35 mm²/s at room temperature.

Due to their chemical structures, HELISOL® heat transfer fluids have an outstanding property profile, which sets them apart from organic materials such as mineral oils and aromatic heat transfer fluids. They are especially characterized by a very high thermal stability. Properly handled and maintained HELISOL® heat transfer fluids can be operated at up to 425 °C for many years before they need replacement. Operation below these temperature maximums may provide even longer service life under most operating conditions.

HELISOL® heat transfer fluids are polydimethylsiloxanes - mixtures of linear siloxane compounds. Due to their chemical structure, they undergo so-called rearrangement reactions (equilibration) of their silicone-oxygen bonds when operated at temperatures above 220 °C. However, this rearrangement reaction of HELISOL® heat transfer fluids is not a degradation reaction and does not affect fluid lifetime.

Because of the rearrangement reaction some physical properties of the fluids will change throughout operation. Once the equilibrium fluid composition is reached the physical properties remain stable. The typical product data and the physical property tables are provided in the technical relevant pressure/temperature range both, for the unused (HELISOL® unused) and used fluid (HELISOL® in use).

For further information about the fluid properties in the full temperature and pressure range please consider the HELISOL® heat transfer fluid Extended Technical Datasheet.

HELISOL® heat transfer fluids are not classified as hazardous. For more information, please consider the Material Safety Data Sheet (MSDS) of the respective product. The MSDS of all HELISOL® heat transfer fluids are related to the unused condition.

However, when HELISOL® heat transfer fluids are used as intended above 220 °C the products of the so-called equilibration reaction are D-cyclic siloxanes (including octamethylcyclotetrasiloxane D4 (CAS 556-67-2), decamethylcyclopentasiloxane D5 (CAS 541-02-6) and dodecamethyl-cyclohexasiloxane D6 (540-97-6).

These low-volatile components have different toxicological and flammability ratings as the unused fluid. Therefore, appropriate handling precautions by the personnel must be taken. HELISOL® in use contains substances ≥ 0.1% that have been subjected to the SVHC process according to REACH regulation (EC) No 1907/2006 Art. 57 as fulfilling the PBT and/or vPvB criteria according to REACH regulation (EC) No 1907/2006 Annex XIII.

This must be considered when handling (sampling, leakages, filling, emptying) HELISOL® heat transfer fluids. For further information regarding the hazard identification and classification of HELISOL® heat transfer fluids “In Use” please contact your WACKER representative.

Fluid service life in general varies with the quality of the fluid and the type and quality of the heat transfer system equipment and can vary from system to system. Significant overheating and fluid contamination will also affect the performance of a heat transfer fluid system. Properly handled and maintained, HELISOL® heat transfer fluids can be operated at 425 °C for many years before they need replacement. Operation below this temperature maximum may provide even longer service life under most operating conditions.

According to DIN 4754 HELISOL® heat transfer fluids must be checked to its serviceability limit state once a year or on demand. Therefore, WACKER recommends regular sampling and inspection of your heat transfer fluids.

Possible cases of demand are:

  • After the initial start-up
  • Three months after the initial start-up period
  • Irregularities of the process which could harm the heat transfer fluid e.g. impurities, water contamination, overheating etc.
  • Three months after a change-over from a different heat transfer fluid

The most common reasons for suggesting fluid replacement are:

  • The test results of viscosity are outside the limits of action resulting for example in impaired low-temperature fluid performance (pumpability).
  • Contamination of the heat transfer fluid with extensive quantities of water or other foreign materials (insoluble solids).

Contact your WACKER representative for details on assistance in the proper disposal of any used fluid. Please also consider the HELISOL® heat transfer fluid Sampling Guide where all relevant information regarding proper sampling techniques and cases of demand are summarized.

This has to be evaluated in detail because there is a variety of different heat transfer fluid technologies available and depends on the exact chemical composition. Always consult your supplier's technical service department for recommendations. In general, petroleum-based, aromatic chemical or synthetic fluids may not be compatible with HELISOL® heat transfer fluids at high temperatures. Deposits from oxidized, thermally degraded, or contaminated organic fluids can foul interior surfaces. These fouling products are not soluble in HELISOL® heat transfer fluids, making it necessary to clean the system prior to charging with the new fluid.

At high temperatures, HELISOL® heat transfer fluids may be sensitive to various contamination. Therefore, it must be ensured to guarantee the exclusion of water, oxygen, oxidizing agents, alcohols, acids and bases or any contamination at operating temperature. Acids, bases or alcohols may accelerate the formation of volatile by-products, while water or oxygen/oxidizing agents can result in crosslinking of siloxane molecules and may cause a faster increase in viscosity.

To minimize these adverse effects HELISOL® heat transfer fluids must be operated under inert conditions in technical tight systems. For example, an inert gas blanket (e.g. nitrogen gas) on the expansion tank is required to prevent the fluid from coming into contact with the outer atmosphere. Especially, when filling or refilling the system, care should therefore be taken to prevent oxygen and moisture from entering the system with the cold fluid.

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