Industrial and high-temperature insulation · Calcium silicate
ASK CS 220
- Max. temp.
- 650 / 1,000 °C
- Thermal conductivity (λ)
- ≤ 0.060 W/m·K (93 °C)
- Density
- ≤ 220 kg/m³
What is calcium silicate insulation?
In short
Calcium silicate is a rigid, white thermal insulation made as slabs, curved segments and pre-formed pipe sections. It is used on high-temperature pipes and equipment in power plants, refineries and petrochemical plants. Its main strength is that it resists compression and impact better than fibrous insulation, so it suits places where the insulation carries load or gets stepped on. Its limits: it is hard and brittle, harder to cut to shape, and porous, so it must be stored and clad to keep water out.
What is it made of?
The US National Insulation Association (NIA) describes the process: silica, lime, reinforcing fibres and additives are mixed with water into a slurry, moulded, then cured with steam under pressure for several hours until calcium silicate crystals form. The pieces are then dried and trimmed. The result contains a very large number of tiny air cells separated by thin crystalline walls, which is why it conducts little heat even though it is hard.
Early calcium silicate insulation used asbestos as the reinforcing fibre. Manufacturers today use other fibres, so when buying, check that the manufacturer's document states asbestos-free — for example ASK CS 220, whose product sheet states inorganic fibre reinforcement and no asbestos.
Do not confuse asbestos with stone wool; they are different materials. See is stone wool safe?
Key properties
- Rigid, takes compression — NIA notes that calcium silicate has high compressive strength compared with other non-structural high-temperature insulations. Horizontal pipes insulated with it tolerate some foot traffic without severe damage
- Keeps its shape when hot — the standard requires tests for shrinkage after heat soaking and for hot-surface performance
- Non-combustible — it is an inorganic material, but fire-test values must be taken from the specific product's documents
- Wide temperature range — divided into types by maximum service temperature
The usual reference standard is ASTM C533, which covers calcium silicate block and pipe insulation for surfaces at 27–927 °C. It defines Type I, Type IA and Type II and requires tests such as thermal conductivity, linear shrinkage, flexural strength, compressive strength and mass loss by tumbling.
Example values from the ASK CS 220 product sheet:
| Property | Manufacturer's value |
|---|---|
| --- | --- |
| Maximum service temperature | Type I 650 °C / Type II 1,000 °C |
| Density | no more than 220 kg/m³ |
| Thermal conductivity (at 93 °C) | no more than 0.060 W/m·K |
| Compressive strength | at least 0.688 MPa |
| Flexural strength | at least 0.35 MPa |
| Linear shrinkage | no more than 2.0% |
These values belong to this product only; they cannot stand in for another brand or grade.
Where is it used?
- Steam and high-temperature process pipes, especially stretches people walk across, step on or lean ladders against
- Hot equipment and vessels that need insulation which does not crush under bands or the weight of the cladding
- Pipe supports, where insulation has to carry the pipe's weight without being squeezed
- Around valves, meters and vibrating points, where NIA notes the material's strength is an advantage
- Backing behind refractory brick in furnaces, as the ASK sheet states
Compared with stone wool and ceramic fibre
No material suits every job. This table shows which jobs point to which material.
| Aspect | Calcium silicate | Industrial stone wool | Ceramic fibre |
|---|---|---|---|
| --- | --- | --- | --- |
| Nature | Rigid, holds its shape | Fibrous, flexible; slabs, blankets, pipe sections | Fibrous, light and soft; blankets |
| Compression / foot traffic | Suitable | Compresses; some jobs need a support structure for the cladding | Not suited to carrying load |
| Fitting uneven surfaces | Must be cut and shaped | Fits easily, especially wired mats | Fits very easily |
| Vibration | Strong, but brittle under hard knocks | Wired mats are designed for it | Depends on fixing |
| Temperature range | By type (see product documents) | By grade (see product documents) | Higher than the other two |
| Points to watch | Dust when cutting; keep dry | Keep dry; cladding | Stricter health requirements; follow the SDS |
Example products for each group: stone-wool pipe sections ROCKWOOL ProRox PS 960 SA for industrial pipework, and MINEWOOL Ceramic Fiber Blanket for work hotter than the range of stone wool and Type I calcium silicate.
In practice they are often combined — calcium silicate only where load is carried, stone wool for the rest. The mix of materials should be decided by the designer.
Handling and installation
- Keep it dry — it is porous. Store it under cover and off the ground, and clad it against water after installation. Water held in insulation raises the risk of corrosion under insulation (CUI)
- Handle with care — it is hard but brittle; corners and edges chip if dropped
- Cutting makes dust — installers should use protective equipment and follow the manufacturer's safety data sheet (SDS)
- Joints — rigid insulation does not spring together the way fibre does, so joints must be butted tightly; thick work should go on in several layers with staggered joints as the designer details
- Cladding — NIA notes it works with several jacket types such as aluminium and stainless steel, with sheet-metal overlaps sealed against water
High-temperature work
The type (Type I / II), thickness and fixing method must be designed for the temperature and site conditions. Have an engineer or industrial-insulation specialist specify and install it. See what is service temperature? and choosing high-temperature insulation.
Sources
- National Insulation Association (NIA), Insulation Outlook — Insulation Materials: Calcium Silicate Block and Pipe
- ASTM C533 — Standard Specification for Calcium Silicate Block and Pipe Thermal Insulation (scope and abstract)
- Zhejiang ASK — Calcium Silicate CS 220 product introduction (distributor copy)
- ROCKWOOL Thailand — ProRox PS 960 SA / PS 970 SA Product Data Sheets (08/25)
- 3T Insulation — MINEWOOL Ceramic Fiber Blanket catalogue
Related products
Categories and example products for this topic
- ASK CS 220 — Asbestos-free calcium silicate, Type I 650 °C / Type II 1,000 °C, slabs and pipe
- ROCKWOOL ProRox PS — Fibrous alternative for pipes: split stone-wool sections, snap-on, up to 650 °C
- MINEWOOL Ceramic Fiber Blanket — For work hotter than Type I: working temperature 1,050 / 1,350 °C
Industrial and high-temperature insulation · Stone wool
ROCKWOOL ProRox PS
- Max. temp.
- 650 °C
- Density
- 120–150 kg/m³
- Thermal conductivity (λ)
- 0.037–0.038 W/m·K (50 °C)
Industrial and high-temperature insulation · Ceramic fibre
3T MINEWOOL Ceramic Fiber Blanket
- Service temp.
- 1,050–1,350 °C
- Density
- 128 kg/m³