Components of a cold/cryogenic insulation system

A cryogenic insulation system consists of a combination of the following main components:

• Insulating material PIR foam
• Insulating material cellular glass
• Insulating material glass wool flakes for cryogenic applications
• Primary and secondary vapour barriers
• Flexible self-adhesive tapes and metal foils
• Contraction joints and associated protection system
• Vapour barrier coatings
• Sealant for cryogenic applications
• Metal jacketing, with metal strips and sealant for seam sealing

Insulation material – polyisocyanurate rigid foam (PIR)

For the properties of rigid polyisocyanurate foam, please refer to the minimum requirements summarised in CINI 2.7.01. The main requirements are specified below, otherwise CINI 2.7.01 is the minimum reference.

Composition according to ASTM C591

• Rigid Polyisocyanurate (PIR) foam, manufactured with CFC-/HCFC-free propellant.
• Foam structure: maximum closed cells (> 90% according to EN ISO 4590 – ASTM D2856).

Properties of rigid PIR foam

• Temperature range: from -200°C to +120°C,
• Specific gravity (EN ISO 845 – ASTM D1622): minimum 40 kg/m3 and maximum 52 kg/m3,
• Thermal conductivity coefficient for non-aged foam (EN 12667 – ASTM C177): max 0.021 W/mK at +20°C and max 0.016 W/mK at -160°C,
• Thermal conductivity coefficient for ageing degraded foam (value determined for dimensioning of thicknesses): 0.025 W/Mk for an average temperature of -65°C,
• Closed cells (EN ISO 4590 – ASTM D2856): more than 90%,
• Water absorption (ISO 2896 – ASTM D2842): max 5% by volume,
• Water vapour permeability (ASTM E96 Procedure A – ISO 1663): 30 (+/-10) g/(m2.24h) at 23°C and 85% relative humidity,
• Chloride content (ASTM C871): max 60 mg/kg.
• Minimum compressive strength (EN 826 – ASTM D1621): higher than (250 kPa and 200 kPa).
• Minimum tensile strength (ASTM D1623) higher than (420 kPa and 320 kPa),
• Dimensional stability (EN 1604): less than or equal to 1%,
• PH: 6 > 7,
• Foam should be protected from prolonged exposure to UV radiation.

Flammability and fire reaction classification

• Temperature index EN ISO 4589-3: above 390°C.
• Fire behaviour classification: category A2 or B according to NF EN 13501 (euro class – low flammability), fire reaction test requirements:
  • Category M1 according to NF P92 501;
  • Category B1/B2 according to DIN4102 (vertical burning).

Insulating material – Cellular glass

The properties of cellular glass are summarised in the minimum requirements of CINI 2.9.01. The main requirements are specified below.

Composition according to ASTM C552 or EN 14305

Cellular glass, without binder and composed of closed cells.

Properties of cellular glass

• Temperature range: -196°C to +430°C;
• Density (ASTM D1622 or EN 1602): 115 kg/m3;
• Thermal conductivity coefficient of plates (ASTM C177 or EN 12667): max 0.048 W/mK at +50°C and max 0.02 W/mK at -180°C;
• Thermal conductivity of shell panels (ASTM C177 or EN ISO 8497): max 0.052 W/mK at +50°C and max 0.022 W/mK at -180°C;
• Closed cells (EN ISO 4590 – ASTM D2856): 100%;
• Water vapour permeability (ASTM E96 Procedure A or EN 12086): max 0 ng / (Pa.s.m) at 23°C and 50% relative humidity;
• Compressive strength (ASTM C165 or EN 826): 500 kPa in all directions.
• Chloride content (ASTM C871 or EN 13468: ion chromatography): max 10 mg/kg;
• PH (ASTM C871 or EN 13468): between 7 and 10.5;

Insulating material – loose Mineral wool for cryogenic applications

The properties of mineral wool for cryogenic applications. Use reserved for contraction joints and specialist parts of the insulation system such as valves, flanges, etc:

• Loose stone/glass wool for cryogenic applications,
• Thermal conductivity coefficient between 0.017 and 0.022 W/ m.K at -170°C, to be specified in the contractor’s quotation,
• Acceptable temperature range of -200°C to +120°C, to be specified in the Contractor’s quotation,
• No organic binder,
• Density: to be specified in the Contractor’s quotation,
• Maximum compression in use: 50%,
• Minimum required fire behaviour: A2 (M0).

Primary vapour barrier

For the characteristics of the primary vapour barrier, refer to the minimum requirements summarised in section 4.4.21 of the CINI 1.3.02 data sheet and the CINI 1.3.53 data sheet. The main requirements are specified below:

• This primary vapour barrier consists of two layers of elastomeric coating, reinforced in the second layer by a fibreglass scrim fabric.

Regarding the coating used as vapour barrier:

• Solvent-based elastomeric coating according to CINI technical specification 3.2.03,
• Permissible temperature range -50°C to +100°C,
• Water vapour permeability, max 0.001 g/m2.h.mm Hg (according to ASTM E96 Procedure E),
• Chloride content (ASTM C871): max 90 ppm,
• Flame dispersion index (ASTM E84): less than 7.

With regard to the fibreglass scrim fabric:

• Glass fabric, type and version recommended by the coating supplier,
• Fabric and number of threads per length to be specified,
• Mass per unit area, in g/m2 to be specified,
• Minimum required fire behaviour: A2 (M0).

Secondary vapour barrier

For the characteristics of the secondary vapour barrier, refer to the minimum requirements summarised in CINI datasheet 3.3.10. The main requirements are specified below:

• Three-layer construction of polyester foil / aluminium foil / polyester film,
• Permissible temperature range of -60°C to +120°C,
• Water vapour permeability, max 10×10-6 g/m2.h.mm Hg (ASTM E96 Procedure E),
• Minimum thickness: 12 micron polyester film and 25 micron aluminium film, total thickness minimum 50 microns,
• Mass per unit area, greater than 100 g per m2,
• Tensile strength, min. 100 MPa,
• Tear strength (Elmendorf), min. 400 g/mm.

Flexible self-adhesive tapes and metal foils

Glass fibre reinforced tape

The first layer of rigid PIR foam, on the pipe side, and any intermediate layers of the same foam should be fixed with tape as referred to in Technical Specification CINI 2.25.01 (chapter 2.4 “Synthetic tape”). The main requirements are specified below:

• Tape of synthetic material reinforced with glass fibres,
• Permissible temperature range of -120°C to +120°C,
• Minimum width 38 mm,
• Minimum thickness 0.14 mm,
• Minimum adhesive strength 200 gr / 25 mm².

Steel strapping and fasteners

The outer layer of rigid PIR foam, the metal cladding and the housing of valves are strapped by means of steel straps and associated clamps. Both components are made of austenitic stainless steel, partly in accordance with the technical specification of CINI 2.25.01 (section 2.1 “Tape on rolls of 10-20 kg”). The main requirements are specified below:

• Austenitic annealed stainless steel, Cr-Ni 18-10 grade (e.g. ASTM A167 TP 304),
• Minimum width and thickness: 13 mm x 0.5 mm for DN 400 and smaller,
• Minimum width and thickness: 19 mm x 0.5 mm for DN 400 and larger,
• Clamps of annealed austenitic stainless steel, of equal thickness guaranteeing the same live load as the steel strap, of a type corresponding to the type of steel strap used.

Contraction joint and associated protection system

The Contraction joint is made of mineral wool for cryogenic applications and is listed in technical specifications CINI 5.1.06 (“Cold insulation – Contraction joints”) and CINI 3.25.01 – 2.1 (Auxiliary materials for cold insulation).

Two types of protection of contraction joints, depending on their location in the cold insulation system:

• The contraction joints of the inner and intermediate layers of rigid foam are covered and protected by a secondary vapour barrier as described earlier.
• The contraction joints of the outer layer of rigid foam are covered and protected by a corrugated layer of butyl rubber 1 mm thick, in accordance with ISO 188 (CINI 3.25.01 – 2.1). This butyl rubber protection of the joint is secured on both sides of the shrinkage zone with steel tape, as described in the previous paragraph.

Vapour stop coating – end pieces and terminations

The characteristics of the “Vapour Stop” coating used for compartmentation and end pieces are based on the minimum requirements summarised in the CINI data sheet 3.2.09 (“Two-component sealing”), with an additional reinforcement of lattice fabric made of glass fibre. The main requirements are specified below:

Cryogenic, two-component elastomeric coating for use as a coating for seals and barriers:

• Two-component” elastomeric coating, according to CINI technical specification 3.2.09,
• Permissible temperature range of -196°C to +120°C,
• Water vapour permeability, max 0.001 g/m2.h.mm Hg (ASTM E96 Procedure E),
• Average solids content (ASTM D1644): 55% by volume,
• Chloride content (ASTM C871): max 90 ppm,
• Flash point (ASTM D93): 23°C,
• Two layers of coating when used as a vapour barrier and three layers when used as a Vapour Stop.

Additional reinforcement for Vapour Stops:

• Glass fabric, type and version recommended by the coating supplier,
• Fabric and number of threads per length to be specified,
• Mass per unit area, in g/m2 to be specified,
• Minimum required fire behaviour: A2 (M0).

The vapour control coating chosen is uniform for the entire system and thus allows all joints for the permissible temperature range (-196°C to +120°C) to be finished with a single cryogenic coating. The use of a second type for the temperature range (-50°C to +120°C) is not acceptable. 

Cryogenic joint sealant

The properties of the joint sealant used to fill the longitudinal and circumferential seams of the various rigid foam elements and vapour control coatings meet the minimum requirements summarised in CINI data sheet 3.2.09 (“Two-component sealant”). The main requirements are specified below:

• Cryogenic joint sealant of the “two-component elastomer” type, in accordance with CINI Technical Specification 3.2.09,
• Permissible temperature range of -196°C to +120°C,
• Water vapour permeability, max 0.001 g/m2.h.mm Hg according to (ASTM E96 Procedure E),
• Average solids content (ASTM D1644): 55% by volume,
• Chloride content (ASTM C871): max 90 ppm,
• Flash point (ASTM D93): 23°C. 

External protective metal cladding

The characteristics of the protective metal cladding, of the type “steel plate coated with pure aluminium, known as type 2 and pre-painted”, are referred to the minimum requirements summarised in data sheet CINI 3.1.02. The main requirements are specified below:

• Steel sheet coated on both sides with pure aluminium, minimum thickness 50 microns,
• Type 2, i.e. “pure aluminium coated”, with 300 g/m² per side,
• Minimum thickness of cladding:
  • 0.55 mm for cold insulation systems with an outer diameter of less than 400 mm;
  • 0.8 mm for cold insulation systems with an outer diameter of more than 400 mm (according to the recommendations of DTU No 67.1);
  • 1 mm for valve boxes and accessories;
• Standard NF A36.345 – Iron and steel products – Steel sheets fully coated with aluminium – Sheets and coils – Thickness 0.5 mm to 3 mm – Maximum width 1540 mm,
• CINI Standard 3.1.02 (Chemical properties according to (ASTM A463M), Table 2 Commercial grade – Corrosion resistance according to (ASTM A463M) – Minimum width 500 mm),
• Special requirements and deviations from the properties of the metal cladding may be specified as “alternatives” in the Contractor’s quotation and submitted to the Client for approval.

Questions or contact?

If you have technical or commercial questions about the components of a cryogenic insulation system or any of our other solutions, please contact us. We will be happy to work with you to find the most efficient insulation solution for your application.