Industrial and high-temperature insulation · Stone wool
ROCKWOOL ProRox WM
- Max. temp.
- 650–750 °C
- Density
- 80–128 kg/m³
- Thermal conductivity (λ)
- 0.037–0.038 W/m·K (50 °C)
Industrial and high temperature
How do you choose high-temperature insulation?
In short
Start from the highest surface temperature that really occurs, then choose a material whose service temperature covers it with a margin. Next, choose a form that fits the surface (pipe section, wired mat, slab or ceramic-fibre blanket), check chloride requirements for stainless steel, and plan cladding against water and impact. Thickness should be calculated by an engineer or industrial-insulation specialist for the actual conditions.
- 1The service-temperature range stated by the manufacturer — check the conditions in the document
- 2The real pipe or equipment surface temperature, including its hottest or coldest moments, must stay within the range
- 3Service temperature is not a fire rating or non-combustibility — they are different tests
Why hot work needs more care than building work
Industrial insulation can serve several purposes: cutting energy loss, holding process temperatures and lowering the outer surface temperature to protect workers from contact. A wrong choice can shrink, sag or degrade early, and water getting into the insulation can cause corrosion under insulation (CUI), which cannot be seen from outside.
Selection steps
- Find the real maximum temperature — include start-up, steam-out cleaning and upset conditions, not only normal operation
- Compare with the insulation's service temperature — use the maximum service temperature from the maker's documents and keep a safety margin. See what is service temperature
- Set the goal — energy saving, process temperature control or limiting outer surface temperature; different goals need different thicknesses
- Choose a form that fits the surface (see the table below)
- Check compatibility with the metal — for austenitic stainless steel, check whether the insulation meets ASTM C795
- Plan cladding and water protection
- Have a specialist calculate thickness and set installation details
Forms of hot insulation
| Form | Suits | Example product |
|---|---|---|
| --- | --- | --- |
| Pipe section | Standard pipe sizes; fast, neat joints | SCG PCI (glass wool, within the maker's stated range) |
| Wired mat | Large pipes, tanks, boilers, flue ducts; curved or irregular surfaces | ROCKWOOL ProRox WM (stone wool, grades by temperature) |
| Slab | Flat equipment walls, rectangular hot ducts | Industrial stone-wool slabs |
| Ceramic-fibre blanket | Very high temperatures beyond stone wool; furnace linings, seals, removable jackets | MINEWOOL Ceramic Fiber Blanket |
Material overviews: glass wool · stone wool · ceramic fibre
Chloride and stainless steel (ASTM C795)
Austenitic stainless steel (such as grades 304/316) is at risk of stress corrosion cracking when chlorides build up on the metal surface together with heat and moisture. The chlorides can come from the insulation itself or from outside water soaking through it.
ASTM C795 is the specification for insulation in contact with austenitic stainless steel. It refers to a corrosion test (ASTM C692) and chemical analysis of chloride and inhibiting ions (ASTM C871). For stainless-steel work, ask the maker for written confirmation — for example, the ProRox WM documents state that it meets this requirement — and still keep water out of the insulation.
Cladding and water protection
- Fibrous insulation needs cladding / jacketing, such as metal sheet, to keep out rain, wash-down water, impact and sunlight
- Cladding joints should overlap so water runs off, penetrations for pipes and supports should be sealed, and the cladding should be inspected and repaired regularly
- Water trapped in insulation lowers its performance and raises the risk of CUI on carbon-steel pipe
- Cladding material, thickness and sealing system should be specified by the designer for the plant's environment
Thickness is calculated, not guessed
Thickness depends on surface temperature, pipe size, ambient temperature, wind, the insulation's thermal conductivity at that temperature and the goal (e.g. an acceptable outer surface temperature). Designers use calculation standards such as ISO 12241 or ASTM C680. We do not give ready-made thicknesses — send site data to a specialist for calculation.
Safety
- Work on live hot pipes or equipment, work at height and work in confined spaces must be done by qualified contractors under the plant's safety procedures
- On first start-up, insulation with an organic binder may give off smoke or fumes for a while; ventilate as the maker advises
- Ceramic fibre has stricter health requirements than glass wool and stone wool; follow the SDS
Common mistakes
- Choosing by melting point or the word "non-combustible" instead of service temperature
- Using building insulation on steam pipes because "it's glass wool too"
- Using ceramic fibre where stone wool would already do, adding health controls for no reason
- No cladding, or leaking cladding, letting the insulation get wet
Sources
- ASTM C795 — Standard Specification for Thermal Insulation for Use in Contact with Austenitic Stainless Steel (refers to ASTM C692 and C871)
- Johns Manville — Technical Bulletin: Stress Corrosion Cracking of Austenitic Stainless Steel
- ASTM C411 — Hot-Surface Performance of High-Temperature Thermal Insulation
- ROCKWOOL Technical Insulation — Process Manual; Corrosion Under Insulation (South Asia); Safe Use Instruction Sheet
- ROCKWOOL Technical Insulation — ProRox WM 950SA / 960SA / 970SA Product Data Sheets
- SCG — SCG Insulation for Industrial : Pipe (PCI) catalogue
- 3T Insulation — MINEWOOL Ceramic Fiber Blanket catalogue
- ISO 12241 and ASTM C680 (calculation standards, titles only)
Related products
Categories and example products for this topic
- ROCKWOOL ProRox WM — Wired mat: steam pipes, boiler walls, furnaces; max 650–750 °C by grade
- ROCKWOOL ProRox SL — Slab for flat surfaces such as equipment walls and tanks; max 450–850 °C by grade
- ROCKWOOL ProRox PS — Pipe section: up to 650 °C, meets ASTM C795 for use over stainless steel
- MINEWOOL Ceramic Fiber Blanket — Very hot work: ceramic fibre blanket, working temperature 1,050 / 1,350 °C by grade
Industrial and high-temperature insulation · Stone wool
ROCKWOOL ProRox SL
- Max. temp.
- 450–850 °C
- Density
- 60–160 kg/m³
- Thickness
- 50–100 mm
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