What are the common grades of calcium silicate insulation specified?

It is generally classified into grades based on maximum service temperature, typically Grade 1 (up to 650°C) and Grade 2 (up to 950°C).

How is the thermal conductivity of the material determined?

Thermal conductivity is determined using the guarded hot plate method, typically referencing IS 3346.

What forms does this insulation come in?

It is primarily supplied as preformed flat blocks, bevelled lags, or half-round pipe sections.

IS 4671

: 1980

Specification for calcium silicate preformed thermal insulating materials

CurrentSpecializedSpecificationBIMMEP · Insulation Materials

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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.

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)

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.