Overview
EN ISO 23766:2024 / ISO 23766:2022 specifies methods for measuring the coefficient of linear thermal expansion (CLTE) of thermal insulating products for industrial installations at sub-ambient temperatures (−196 °C to 25 °C). Published by CEN as EN ISO 23766:2024, the standard defines equipment, procedures and reporting requirements for reliable determination of linear contraction/expansion of insulation materials used in cold and cryogenic applications. It excludes materials that change dimension because of loss of hydration water or other phase changes during testing.
Key topics and technical requirements
- Scope and exclusions: Test range −196 °C to 25 °C; not applicable to products undergoing dimensional change from dehydration or phase transitions.
- Two test methods:
- Method A - Optical method: Uses a planar, parallel light beam and detector (optical dilatometry) to measure dimensional change. Example apparatus uses an InGaN-based light source with a collimator keeping the beam parallel within 2″ (≈ 0.0097 mrad). Typical specimen sizes cited are 10 mm to 30 mm.
- Method B - Displacement method: Uses a distance/displacement sensor to record linear change as the specimen is cooled.
- Apparatus and accuracy:
- Test chamber capable of controlling specimen mean temperature to ±0.5 K and limiting temperature change rate to 1 °C/min.
- Cooling commonly provided by liquid nitrogen; chamber design must allow good temperature distribution and optical access when required.
- Temperature measurement with calibrated thermocouples of accuracy ±0.5 K.
- Light detector and sensors must be calibrated over the required measurement range.
- Specimen preparation and conditioning: The standard specifies dimensions, number and conditioning procedures to ensure reproducible results (see full standard for details).
- Calculation, reporting and measurement uncertainty: Procedures for calculating CLTE, expressing results and documenting test conditions are included.
Applications and practical value
- Material selection and specification for cryogenic piping, LNG storage, cold process lines, refrigeration and cold-chain infrastructure.
- Quality control and R&D for manufacturers of thermal insulating products.
- Engineering design input to predict thermal contraction, reduce mechanical stress, ensure tightness and maintain insulation integrity at low temperatures.
- Compliance testing for procurement and certification of industrial insulation systems.
Who should use this standard
- Test laboratories and third‑party certifiers
- Insulation product manufacturers and R&D teams
- Mechanical and cryogenic system designers and integrity engineers
- Specifiers and procurement professionals in industrial refrigeration, petrochemical and LNG sectors
Related standards
- ISO 9229 - Thermal insulation - Vocabulary
- ISO 18099 - Determination of the coefficient of thermal expansion (related methods)
Keywords: thermal insulating products, coefficient of linear thermal expansion, CLTE, sub-ambient temperatures, optical dilatometry, displacement method, EN ISO 23766:2024, cryogenic insulation.
