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
How are tanks, boilers, ovens and hot ducts insulated, and with what?
In short
Look at two things first: the shape of the surface and the real maximum temperature. Flat walls — boiler walls, ovens, rectangular hot ducts — suit stone wool slabs on pins. Curved or irregular surfaces and equipment that vibrates suit wired mats. Large tanks that do not vibrate can take stone wool blankets. Thick or very hot work should go on in several layers with staggered joints, allow for the metal's expansion, and be finished with water-shedding cladding. Ceramic fibre comes in only when the temperature is beyond the range of stone wool. Thickness and fixing details should be designed by a specialist.
How do the types of equipment differ?
| Equipment | Surface | What needs particular thought |
|---|---|---|
| --- | --- | --- |
| Storage tanks and vessels | Wide-radius walls, tank roofs, dished heads | Weight of insulation on tall walls, rain on the roof, places people step |
| Boilers | Flat and curved walls with stiffeners, openings and many pipes | High temperature, expansion, vibration |
| Ovens and drying cabinets | Flat walls, doors, inspection hatches | Cyclic running, joints around doors |
| Hot-air ducts and flues | Rectangular or round, with external stiffeners | Flow-induced vibration, lengthwise expansion |
Flat walls: stone wool slabs on pins
Slabs hold their shape, close wide areas flat and support the cladding well. ROCKWOOL's documents describe the fixing: slabs are fastened to the equipment on insulation pins that are welded or mechanically fixed to the surface; the edges of each slab must be butted tightly; and steel in a corrosive environment should be cleaned and given a protective coating before it is insulated.
Product to consider: ROCKWOOL ProRox SL, stone wool slabs for equipment walls, boilers, columns, tanks and hot ducts, in six grades with maximum service temperatures of 450–850 °C by grade.
Worth knowing:
- The number and spacing of pins depend on the insulation's weight, the orientation of the surface (vertical wall, underside) and the temperature; the designer sets them
- Undersides and vibrating surfaces need more secure fixing than vertical walls
- The pin and washer material must withstand the surface temperature
Curved surfaces and vibrating equipment: wired mats
A wired mat is stone wool stitched to wire mesh. It wraps around curves, vessel heads, bends and complex shapes, and the mesh holds the fibres together when the equipment vibrates. The mesh edges of adjoining mats are stitched together with wire or hooks.
Product to consider: ROCKWOOL ProRox WM. The manufacturer states its use on pipework, boiler walls, furnaces and flue ducts (WM 950 SA), and on high-pressure steam pipes, reactors and furnaces (WM 960 SA / 970 SA). Maximum service temperature is 650 / 650 / 750 °C by grade.
Wired mats have little resistance to compression, so spacers or a support structure for the cladding are usually needed to stop the cladding's weight crushing the insulation. On vertical surfaces, support rings carry the insulation's weight so it cannot slide down.
Large tanks that do not vibrate: stone wool blankets
Large storage tanks have wide-radius walls and a lot of area, so long rolls go on quickly with few joints.
Product to consider: ROCKWOOL ProRox BL, stone wool blankets in three grades with maximum service temperatures of 350 / 450 / 650 °C. The manufacturer specifies them for equipment that does not vibrate; where there is vibration, consider wired mats.
Extra points for tanks:
- Tank roofs and places people step — need insulation that resists compression, or a support structure. Crushed insulation lets the cladding sag and water pond
- Wall-to-roof junctions, nozzles and the tank base — places where water gets in and collects easily
- Tanks at moderate temperature or in cyclic service — sit in the range where corrosion under insulation (CUI) needs attention
Several layers with staggered joints
When a large thickness is needed, or the temperature is high, splitting it into two or more layers and offsetting the joints of each layer has clear benefits:
- No joint runs straight from the hot surface to the cladding
- When the metal expands and inner joints open slightly, the outer layer still covers them
- Different materials can be used in each layer, for instance an inner layer rated hotter than the outer one
ROCKWOOL's installation guidance calls for the joints of the outer layers to be staggered lengthwise and, where possible, across, and for every layer to be fixed for a tight fit. Working out the temperature at the interface between layers (to choose each layer's material) is a design calculation.
Expansion and cladding
Steel grows when it heats up. Large equipment and long ducts therefore move a good deal relative to the cooler cladding outside.
- The insulation and cladding system must accommodate that movement without tearing or opening joints, for example with expansion joints as the designer details
- Metal cladding keeps out rain, wash water and knocks. ROCKWOOL's documents call for cladding joints to be fastened with screws or rivets and sealed watertight
- Around openings, oven doors, inspection hatches and stiffeners, the work must be finished carefully; these are both heat leaks and water entry points
The type of cladding also affects the outer surface temperature — see personnel protection insulation.
When is ceramic fibre needed?
Industrial stone wool covers most tank, boiler and hot-duct work, within each grade's maximum service temperature (in the range we sell, the highest is 850 °C for ProRox SL 978 SA). Ceramic fibre comes in when:
- the surface is hotter than the service temperature of the stone wool grades available, such as the inner wall of a high-temperature furnace
- a hotter-rated inner layer is needed, with stone wool as the outer layer of a multi-layer system
- sealing, packing gaps, or making removable insulation jackets at very hot points
Product to consider: MINEWOOL Ceramic Fiber Blanket, 128 kg/m³, in two grades with working temperatures of 1,050 °C (Standard) and 1,350 °C (Zirconium).
Ceramic fibre should not be used where stone wool already does the job, because its health requirements during installation are stricter. See what is ceramic fibre?
Safety
- Pin welding, work on equipment that is still hot, work at height and work in confined spaces such as inside tanks or furnaces must be done by qualified contractors under the plant's permit-to-work system
- On first heat-up, mineral wool with an organic binder may give off smoke or fumes for a short time; ventilate as the manufacturer advises
- Ceramic fibre requires protective equipment and compliance with the safety data sheet (SDS)
- Insulation thickness must be calculated for the real conditions; we do not give ready-made thicknesses
Common mistakes
- Using plain blankets on vibrating equipment, so the insulation settles and leaves a gap at the top
- Installing one thick layer and leaving joints that run straight through
- Not allowing for expansion, so the cladding tears or joints open after start-up
- Choosing a grade by density instead of the maximum service temperature in its document
- Neglecting cladding on tank roofs and around nozzles, letting water into the insulation
Read next: stone wool slab, blanket, wired mat or pipe section · choosing high-temperature insulation · insulation fixing accessories
Sources
- ROCKWOOL — RockTech Slab Series data sheet (Handling and Installation: pins, joints, surface preparation, cladding)
- ROCKWOOL Technical Insulation — Insulation with SeaRox wired mats (spacers, support rings, staggered joints)
- ROCKWOOL Technical Insulation — Installation guidance videos (wired mats on vessels, cladding)
- ROCKWOOL Technical Insulation — Storage tanks product category
- ROCKWOOL Thailand — ProRox SL, BL, WM Product Data Sheets (08/25)
- 3T Insulation — MINEWOOL Ceramic Fiber Blanket catalogue
- American Petroleum Institute — API RP 583 (contents: CUI-susceptible locations on vessels, tanks and insulation support rings)
Related products
Categories and example products for this topic
- ROCKWOOL ProRox SL — Slabs for boiler walls, tanks and hot ducts: six grades, 450–850 °C by grade
- ROCKWOOL ProRox WM — Wired mats for boiler walls, furnaces and flues: 650 / 650 / 750 °C by grade
- ROCKWOOL ProRox BL — Long rolls for large non-vibrating tanks and vessels: 350 / 450 / 650 °C by grade
- MINEWOOL Ceramic Fiber Blanket — Beyond stone wool's range: ceramic fibre, working temperature 1,050 / 1,350 °C
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 insulation · Stone wool
ROCKWOOL ProRox BL
- Max. temp.
- 350–650 °C
- Density
- 60–100 kg/m³
- Thickness
- 50–100 mm
Industrial and high-temperature insulation · Ceramic fibre
3T MINEWOOL Ceramic Fiber Blanket
- Service temp.
- 1,050–1,350 °C
- Density
- 128 kg/m³