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IS 4671:1980 is the Indian Standard (BIS) for calcium silicate preformed thermal insulating materials. This standard prescribes the requirements and methods of sampling and test for calcium silicate preformed thermal insulating materials, typically supplied as blocks or pipe sections for high-temperature industrial and MEP applications.
Specifies requirements for calcium silicate preformed thermal insulating materials.
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! Always ensure the material is strictly kept dry during storage and installation; moisture ingress severely degrades its thermal insulating properties.
! Calcium silicate is highly rigid but brittle; careful handling is required on-site to prevent edge breakage and minimize dust.
! Though the original 1980 standard may predate strict asbestos regulations, modern procurement must explicitly specify 'asbestos-free' calcium silicate to meet current HSE norms.
Standard Specification for Calcium Silicate Block and Pipe Thermal Insulation
Covers preformed calcium silicate block and pipe thermal insulation for hot surfaces.
BS EN 14306:2015+A1:2018BSI / CEN, UK / Europe
HighCurrent
Thermal insulation products for building equipment and industrial installations - Factory made calcium silicate (CS) products - Specification
Specifies requirements for factory-made calcium silicate products for industrial insulation.
JIS A 9510:2019JSA (Japanese Standards Association), Japan
HighCurrent
Preformed calcium silicate thermal insulation
Specifies requirements for preformed calcium silicate insulation for heat-retaining applications.
GB/T 10699-2018SAC (Standardization Administration of China), China
MediumCurrent
Calcium silicate insulating products
Covers general calcium silicate insulating products, including those with asbestos (Type I).
Key Differences
≠IS 4671:1980 does not explicitly ban asbestos. Modern international standards like ASTM C533 and EN 14306 mandate that the product must be asbestos-free.
≠Modern standards have more detailed classification. IS 4671 specifies one type for up to 650°C, while ASTM C533 has Type I (650°C) and Type II (927°C), and EN 14306 uses a complex designation code for multiple properties.
≠International standards like ASTM C533 specify chemical requirements, such as limits on leachable chlorides, to mitigate stress corrosion cracking on stainless steel. IS 4671:1980 lacks these specific chemical purity requirements.
≠IS 4671 references outdated Indian test methods, whereas international standards reference current and globally recognized test procedures (e.g., ASTM, ISO) for determining properties like thermal conductivity and compressive strength.
Key Similarities
≈All standards cover the same fundamental material: preformed thermal insulation made primarily from hydrated calcium silicate.
≈The primary intended application is consistent across all standards: thermal insulation for high-temperature pipes, equipment, and vessels in industrial facilities.
≈The product forms specified are similar, principally covering preformed blocks (slabs) and pipe sections (coverings).
≈All standards define requirements for the same core performance properties, including maximum service temperature, density, thermal conductivity, and mechanical strength (compressive or flexural).
Parameter Comparison
Parameter
IS Value
International
Source
Maximum Service Temperature
650 °C
1200 °F (650 °C) for Type I
ASTM C533-22
Apparent Density (max)
240 kg/m³
15.0 lb/ft³ (240 kg/m³)
ASTM C533-22
Compressive Strength (min, at 5% deformation)
5.5 kgf/cm² (≈540 kPa)
60 psi (≈414 kPa)
ASTM C533-22
Flexural Strength / Modulus of Rupture (min)
2.8 kgf/cm² (≈275 kPa)
45 psi (≈310 kPa)
ASTM C533-22
Linear Shrinkage (max, after 24h at max temp)
2.0% at 650 °C
2.0% at 1200 °F (650 °C)
ASTM C533-22
Thermal Conductivity (max, at 300°C mean temp)
0.087 kcal/m.h.°C (≈0.101 W/m·K)
0.70 Btu·in/h·ft²·°F (≈0.101 W/m·K) at 500°F (260°C) mean temp
ASTM C533-22
Leachable Chlorides (for stainless steel)
Not Specified
Must be tested per ASTM C795; specific limits apply (e.g., <50 ppm)
ASTM C533-22
⚠ Verify details from original standards before use
Key Values4
Quick Reference Values
max temperature grade 1650 °C
max temperature grade 2950 °C
typical bulk density240 to 300 kg/m³
max thermal conductivity at 100C0.065 W/(m·K)
Tables & Referenced Sections
Key Tables
Table 1 - Physical Requirements for Calcium Silicate Insulation