Reliable insulation of low temperature pipelines
The insulation of pipelines for cold and low temperature technology presents technicians diverse challenges. Numerous requirements have to be met, which means that insulators must have very high-level, specialist knowledge. Not only the insulation material itself but also the method of applying it must guarantee that the low temperature of the transported medium, which in some cases may be critical, remains constant even over long distances. Examples of such media include liquid gas (LNG/LPG), ethylene and ammoniac, which are used in numerous industrial processes.
If the relevant pipelines are inadequately or incorrectly insulated, this can lead to high energy losses, fluctuations in the process and – in extreme circumstances, if highly flammable gases leak out – the total failure of the plant and therefore high costs. Technicians, therefore, bear a huge responsibility.
The insulation material is crucial.
What, then, should be taken into account when insulating pipelines in refrigeration and deep-freeze technology? First, the insulation systems used must be extremely reliable and cost-efficient. Second, they must demonstrate optimal mechanical qualities and endure high thermal stress. This means, specifically:
Low heat conductivity
The temperature of the medium in the pipeline must be kept constant over long distances. Variations in temperature may cause the medium to be no longer usable. This means that the insulation material used must, on the one hand, prevent the refrigeration inside from escaping and, on the other hand, prevent the outside temperature from warming up the medium.
The insulation must also be able to withstand the extreme temperatures which are often prevalent in the industry. Extreme temperature cycles also cause tremendous vibrations, warpage and impacts. The insulation must not be damaged by these mechanical stresses and has to be reliably able to absorb such fluctuations without changing its consistency, settling, warping etc.
Protection from corrosion
As soon as the surface temperature of the pipe falls below the respective ambient temperature, condensation is produced, which almost inevitably causes corrosion. It is the job of the insulation to reliably prevent this by not allowing condensation to occur in the first place. This means that the insulation materials used must demonstrate a high water vapour diffusion resistance coefficient.
Since many of the transported media are critical, i.e. highly flammable, it is all the more important that no gas should escape. The insulation used should reliably prevent the main cause of gas emission (leakage as a result of corrosion) in the pipeline environment – and therefore prevent production failures or entire plant outages.
Be on the safe side with Kaiflex
Kaiflex insulation materials are optimally suited to the correct insulation of cryogenic plants. Thanks to their low thermal conductivity, a high water vapour diffusion resistance and their closed-cell, water-repellent structure, they fulfil all the criteria mentioned above. Even if the cell structure is damaged, the insulation and vapour barrier capacity is retained. The following products guarantee the safe and reliable insulation of pipelines in cold and low-temperature technology:
R-FORCE sheets and R-FORCEplus V-cut sheets made from Semi-rigid elastomeric foam (SERIEF)
- Temperature application range -200 °C to +85 °C, see below
- Heat conductivity: λ0 °C = 0.038 W/(m·K)
- Water vapour diffusion resistance level: μ ≥ 7,000
- Building material class B-s1,d0 with INCERAM cladding
Kaiflex KKplus tube and sheet material
- Temperature resistance of -50 °C (-200 °C, see below) to +110 °C (sheet +85 °C)
- Heat conductivity: λ0 °C = 0.033 W/(m·K)
- Water vapour diffusion resistance level: μ ≥ 10,000
- Construction material classes BL-s2, d0 (tubes and self-sealing tubes) and B-s3, d0 (sheet)
Kaiflex EPDMplus tube and sheet material
- Temperature resistance of -50 °C (-200 °C, see below) to +150 °C
- Heat conductivity: λ0 °C = 0.038 W/(m·K)
- Water vapour diffusion resistance level: μ ≥ 8,500
- Building material class E
Reliable and correct setup
As well as using insulation material which is suitable for low-temperature zones, it is important that the insulation is applied correctly. This means that the insulation system – depending on the temperature range of the medium – must be set up as follows:
Temperature range from -50 °C to -110 °C
In this temperature range, the insulation system must consist of at least two material type layers (the thickness and subdivision of the respective layers depends on the required heat transmission value and the dew point position). The first layer is constructed with Kaiflex EPDMplus or R-FORCE, and the second with Kaiflex KKplus or R-FORCE in the corresponding thickness. The interior diameter of the first tube dimension or the first layer should always be selected one size larger than that of the insulated pipe. For example, for a pipe diameter of 22 mm, a Kaiflex EPDM tube with an interior diameter of 28 mm should be selected. When using Kaiflex sheet material – with the exception of R-FORCE, which has a very low thermal expansion and shrinkage – the interior diameter of the insulation must also be selected in a larger size (‘finger gap’). You should also fit an abrasion protection foil, such as Kaiflex Protect F-ALU, between the pipeline and the lowest insulation layer.
Temperature range from -110 °C to -196° C
In this temperature range, the insulation system must consist of at least three layers. The first layer is again constructed with Kaiflex EPDMplus or R-FORCE, and the second and third with Kaiflex KKplus or R-FORCE in each case. An example of a very cold medium is nitrogen. Pipelines carrying liquid nitrogen run the danger of liquid oxygen forming in the core area of the insulation, since the boiling point of N2, -196 °C, is 13.5 °C lower than that of oxygen, which is -182.5 °C. Oxygen in the air can condense on pipelines containing liquid nitrogen. The condensed liquid oxygen may, in some cases, react aggressively to organic material. It is therefore important in this case to lay a vapour-proof film, such as Kaiflex Protect Alu-NET, Alu-TEC or F-ALU. This should be laid over at least the first layer, with adhesion over the entire surface. Vapour barriers are recommended in at least every second layer. In addition, all permeations must be sealed in a vapour-proof way. Bumps and overlaps should be additionally adhered by Kaiflex Tape to make them airtight and sealed off with Kaiflex sealant (mastic). On vertical pipelines, the individual layers must be adhered over their entire surface, except in the case of R-FORCE, which is self-supporting. In critical environments or extreme climates, where normal adhesive does not work, you should work with R-FORCE (thermoweldable) and the airtight weldable cladding comCLAD.