Back to basics: High thermal insulation is required when conditions are really hot

After our previous topic, cold insulation, it’s starting to warm up again – you could even say that the Back to basics series continues in a rather hot atmosphere. In this article, we focus on high thermal insulation and the materials used in it, as well as the types of lining.

High thermal insulation promotes to safety and energy efficiency

High temperatures are no joke. Ikaros knows it too – he flew too close to the sun with wings made of feathers and wax and crashed. Daidalos, Ikaros’ father who made the wings, had warned his son about the temperature, but maybe he should also have chosen a high thermal insulation material when he made the wings.

Moving from mythology to the present day, everyone has their own experience of high temperatures. You may have accidentally touched a hot stove in the kitchen or sauna or put your finger on an iron and noticed that your skin cannot withstand such temperatures. However, these temperatures are still low compared to high thermal insulation temperatures, where the insulation is put through a real acid test.

High temperature insulation of equipment and pipes is when the temperature rises above 600–700 °C. The insulation is usually built on the inside of the sheathing surface, the outer surface of the structure, to protect the sheathing not only from heating, but also from the stress caused by the heating. Such stressful factors include internal mechanical and chemical stresses and vibration, which puts strain on the fixing of insulation.

The higher the temperatures are, the more energy is at risk of being wasted. High thermal insulation can bring significant energy savings, which are beneficial not only for the economy, but also for the environment.

High temperatures place demands on materials

The materials used for high thermal insulation are different from other insulation materials because they have to withstand mechanical and chemical conditions in addition to the higher temperature. For example, the highest temperature for conventional mineral wool materials is usually around 700 °C, whereas mineral wool for high temperatures can withstand temperatures of around 1 000 °C.

Other high temperature insulation materials include:

  • vermiculite
  • perlite
  • calcium silicate
  • ceramic fibres.

Insulation materials are usually classified according to either the thermal conductivity or the temperature resistance of the material. However, it is difficult to draw a line between the two classifications because in many applications the term ‘insulating material’ is used for materials that are used elsewhere as hard wearing linings.

In any case, the choice of material is usually based on the thermal stress, i.e. the temperature inside the equipment and the way the equipment is used. The most economical lining solution is usually achieved by choosing a material with the lowest possible specific heat capacity and good insulation properties.

Although it is difficult to define precisely, insulation lining materials can be divided into:

  • insulation bricks
  • insulation mass
  • ceramic fibres.

The type of lining matters

Lining solutions are always designed on a case-by-case basis. We’ve listed a few considerations for different types of lining – do you remember all of them?

  • Brick lining is still a very useful solution for applications such as billet heating furnaces, molten metal processes and grate structures. With bricks, you have to bear in mind their susceptibility to cracking.
  • Mass lining challenges brick lining, among other things, in terms of costs: thanks to the mass installation and workability, the end result is often more affordable than in brick lining.
  • The clear advantages of fibre lining are its good insulating properties, its very low heat retention capacity and the low need for sheathing support structures, not to mention the absence of problems with thermal shocks.
  • Multi-layer felt lining is a challenge for the installer – most installation errors are related to installing the fibre layers too tightly.
  • Fibre module lining is increasing in popularity due to its easy installation, which also compensates for the price of fibre module lining.

Lining can also be done by combining lining materials. Common combinations include fibre and brick or mass and brick. In some cases, additional internal insulation is also installed to improve the energy efficiency of the appliance or to extend the life of the old structure. Lining can also be installed externally, but then you have to be careful with the maximum structure temperatures.

Choose your insulation material for high temperatures more wisely than Daidalos, the father of Ikaros – we supply products from Insulcon, a specialist in high temperature insulation. Let’s return to insulation facts in the next part of the article series!

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