In-houseThe crucial role of moisture-resistant insulation in cold temperatures
In industrial environments where extremely low temperatures are involved, cold insulation is essential in maintaining thermal stability and ensuring the optimal operation of cryogenic systems. Whether storing liquid cryogenic gases or transporting cryogenic liquids, effective insulation is crucial to optimise performance and prevent unwanted heat transfer.
Why is cryogenic insulation important?
At cryogenic temperatures, below -150°C, the physical properties of materials are greatly altered. Insulation materials such as Cellular glass or mineral wool then become fragile and lose their effectiveness. Cryogenic insulation is designed to meet these challenges, offering advanced solutions that can withstand extreme temperatures while ensuring low thermal conductivity.
The importance of moisture resistance
In cold insulation, it is essential to prevent moisture from entering the insulation system. This is because moisture can reduce the performance of the system and even damage the insulation when it freezes. The greater the temperature difference is between the ambient temperature and the system temperature, the greater the ‘migration’ of moisture to the pipe/barrel surface and thus the greater the need for an effective and durable vapour barrier.
Insulating materials for cold cryogenic insulation
FOSTER® Products Corp has over 100 years of experience in thermal insulation protection, offering complete solutions to prevent moisture intrusion in cold insulation systems, even at temperatures as low as -196°C. FOSTER® vapour barriers provide complete protection without seams, overlaps or joints that could cause short- or long-term problems. This is especially important for bends, T-joints, vessels and other complex shapes.
Different insulation materials offer excellent performance at cryogenic temperatures. Here we name the main components of cold insulation:
1. Primary vapour barrier
A primary vapour barrier is used to seal joints and end sections in cold insulation systems. A Foster® elastomer coating, such as Foster Monolar Mastic 60-90 or 60-91, is applied in two or three layers over the outer insulation surface. Reinforcement mesh is added to the first layer before applying the second.
Foster Vapor-Safe Mastic 30-90 is a very solid, fire-resistant and flexible water-based vapour barrier coating. Suitable for most types of insulation, including polystyrene and elastomeric foam. It offers water resistance and low water vapour permeability comparable to solvent-based products. For use in very humid environments, this coating reduces water vapour penetration into materials.
2. Secondary vapour barrier – VaporStop Foil & Tape
For multiple insulation layers, the inner insulation layer is covered with a secondary vapour barrier. This secondary vapour barrier consists of a three-layer VaporStop Mylar foil with VaporStop tape sealing the seams and overlaps.
3. VaporStops/Insulation ends
VaporStops are barriers that prevent the migration of moisture or vapour into the insulation system. They are usually installed at seams, connections or transitions where vapour can penetrate. The main function of this special sealant is to create a physical barrier through compartments that restrict the passage of vapour, preventing it from spreading further within the insulation system and reducing the efficiency of the insulation system.
Insulation ends refer to the termination points of cryogenic insulation systems, where insulation meets other materials. Sealing the insulation properly is crucial to prevent heat leaks. Proper sealing with a suitable sealant or adhesive is critical to prevent heat leaks. In cryogenic insulation systems, most insulation ends, e.g. flanges and valves, are protected with Foster® 90-66 cryogenic coating/adhesive/sealant.
4. Joint Sealant
Joint sealants seal the connections between insulation components like pipes, valves, and flanges. This prevents moisture from penetrating through the seams, which reduces the efficiency of the insulation system. In addition, joints are often subject to movement, such as expansion and contraction due to temperature changes. A flexible joint sealant can accommodate these movements without cracking or damaging the seal. A Foster® sealant or adhesive is used for perimeter and longitudinal seams, with the outer layers sealed in multi-layered systems.
Foster Foamseal 30-45 and Foster Flextra Sealant 95-50 are flexible, vapour-retardant sealants for jointing cellular glass, PIR and PUR foam insulation. There is also Foster 81-84 two-component adhesive for bonding thermal insulation (including polystyrene foam), by itself to metal, cement and wood.
5. Glass fibre reinforcement
Glass fibre reinforcement often performs several functions in cold/cryogenic insulation systems. One is to prevent the material from cracking, expanding or shrinking due to thermal loads or mechanical stresses, such as tensile and compressive forces. Scrimtex™ is lattice fabric made from 100% fiberglass and is used as joint tape, as a covering for plasterboard and pipe insulation and as reinforcement for mastic and coatings used in pipe lining and insulation. It is frayed to give the fabric dimensional stability, reducing the risk of tearing and damage.
Another lattice fabric is Mast-A-Fab®, made of nylon with a leno weave that gives the fabric stability and prevents thread movement and twisting inherent in flat woven cloth. Applying Scrimtex or Mast-A-Fab® between the two layers of the primary vapour barrier distributes the insulation mass evenly over the surface, providing consistent thickness and insulation performance.
6. Filament Tape
Filament tape™ is a fiberglass reinforced tape used to hold insulation system components such as pipe sections and (segment) bends in place.
7. Metal jacketing
Generally, metal jacketing, also known as cladding, is used in cold/cryogenic insulation applications as a robust protective layer against mechanical stress and weathering. In addition, metal jacketing can provide an extra layer of fire protection and provide structural support to insulation. When metal cladding is placed over insulation, the overlaps are sealed with Foster® Elastolar Sealant 95-44. This is an aluminium coloured, fire-resistant, flexible butyl-based elastomeric vapour barrier sealant. This sealant is intended for sealing joints in insulation, metal and masonry, where maintenance of a watertight and airtight seal is required.
Another option is the 96-01 Extruded Sealant tape, a light grey, non-curing joint sealant with excellent properties when it comes to adhesion and weather resistance. The sealant forms a waterproof gasket that deforms under slight pressure to fill irregularities and cavities.
Conclusion
Cryogenic insulation is an essential part of maintaining extreme temperatures in various industrial applications. High-quality insulation materials and moisture-resistant solutions can maintain the thermal stability of cryogenic systems and improve their efficiency. Investment in cold insulation results not only in long-term cost savings, but also in ensuring the safety and reliability of processes that depend on extreme cold.