We'd like to apologise in advance for the cold jokes, but this time they seem to fit in with the theme. Cold insulation is next in our series, The ABC of insulation.
Cold insulation keeps the cold cold
What has once been cooled down shouldn't be heated up again - this applies to both old love affairs and insulation. When the cold can be kept cold with the help of insulation, less energy is needed to maintain the cold temperature.
Everyone knows that you shouldn't keep your freezer open, otherwise you'll lose power and your freezer's performance will suffer. The same applies to poorly insulated industrial systems, but on a much larger scale.
Cold insulation has two important goals:
- To insulate so that as little heat as possible is transferred from the surrounding air to the object to be insulated. While thermal insulation prevents the flow of heat from the object to its surroundings, the principle of cold insulation is exactly the opposite. It restricts the flow of heat from the surroundings to the object to be insulated so that the heat flow does not increase the temperature of the contents, whether the medium is gas or liquid.
- To protect the surface from moisture (condensation). Refrigeration installations typically struggle with problems caused by moisture and condensation. When warm air meets a cold surface, the air's ability to absorb moisture is reduced, causing condensation to settle on the cold surface.
In cold insulation, moisture is the enemy
The need for moisture management places special demands on cold insulation materials. The cell structure of the insulation material used on a cold object should be mainly closed and preferably have high diffusion resistance, so that humidity cannot penetrate it. Diffusion refers to a phenomenon in which air humidity tends to equalise between different humidity levels.
In addition, for an open-cell material, the insulation must be protected against diffusion by a vapour barrier that must be intact and meet the minimum requirements for water vapour permeability. For example, odourless bitumen and bitumen felt or bitumen mats, plastic or metal foil can be used as a vapour barrier. The joints of these materials must be as tight as the material itself for the vapour barrier to work.
The vapour barrier is always installed on the warm side of the insulation layer, i.e. on the outer surface. This prevents water vapour from being absorbed into the insulation.
On the other hand, a vapour barrier is not needed if you use insulation with a closed cell structure, such as ArmaFlex from Armacell, a product developed from cellular rubber. In this case, water vapour diffusion resistance is built into the entire material.
When dimensioning cold insulation, it is necessary to define the dew point to prevent moisture and condensation from forming on the surface of the insulation. The dew point can be calculated from the air temperature and the relative humidity of the air, and results in the temperature at which moisture begins to condense on the surface of the object. For example, if the dew point is 8℃, the insulation must be carried out so that the surface temperature is higher than 8℃.
Here's a cool tip: Armacell offers an easy-to-use online tool for calculating technical insulation. Try it out here.
Condensed water on the bathroom mirror or shower cubicle is something everyone is familiar with. If the moisture accumulates in the insulation materials in the same way, the insulation performance is impaired and the life of the material will be shortened. At the same time, the surface under the insulation is exposed to corrosion and rust.
Why is cold insulation practised?
Cold insulation can be divided into three groups based on their main purpose:
- With condensation insulation, the aim is to keep the surface temperature of the insulation higher than the dew point and thus prevent moisture from condensing on the surface of the insulation.
- In process thermal insulation, the aim is to keep the temperature of the contents (medium) of the object to be insulated within the limits required by the process.
- In economic cold insulation, the aim is cost-effectiveness, by reducing cold losses and optimising insulation costs.
Important things to remember when installing cold insulation
As with all insulation, including cold insulation, accurate work, the right tools and equipment, and high-quality materials are important prerequisites for a successful end result.
It's worth paying particular attention to penetrations and joints to ensure they are properly sealed. Each layer of insulation must be installed separately and the joints must be sealed by gluing them together.
Special precision is also required with support structures, brackets, valves, pumps and t-connections to avoid the formation of thermal bridges through extra joints.
The pipe or tank to be insulated must be protected against corrosion before the insulation is installed. There is a high risk of corrosion, especially on surfaces with an operating temperature of -10℃ or higher, and on pipes that are not in continuous use. On the other hand, a pipe whose temperature is significantly below freezing is more likely to be spared from corrosion.
Let's warm up again - but not the old love affairs. See you in the next instalment of the article series!
This article was originally written and published by our Finnish sister company, Kespet Oy in co-operation with Armacell, and has been translated and adapted into Norwegian. Original title: Back to basics: Why do we need cold insulation?
Read part 1 of the article series here: Do you remember the basics of technical insulation?
Read part 2 in the article series here: Technical building equipment also needs care and insulation
Read part 3 in the article series here: Industrial insulation