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)
How do you choose insulation for hot-water and steam pipes?
In short
Start with the maximum pipe temperature and choose insulation whose manufacturer-stated service temperature covers it. Then pick the form that suits the job: straight pipes in standard sizes usually take pre-formed pipe sections; large pipes, bends and irregular shapes take wired mats; points that carry load take a rigid material such as calcium silicate. Finally, it needs a jacket against water and impact. Thickness comes from design, not from one number for every job.
Why insulate hot pipes?
The National Insulation Association (NIA) and ROCKWOOL Technical Insulation list similar functions for pipe insulation. Hot pipework usually needs more than one at once.
- Reduce heat loss, saving fuel and cutting carbon emissions
- Personnel protection: lower the temperature of surfaces people can touch, to prevent burns
- Process control: keep the fluid at the required temperature when it arrives
- Noise reduction from pipes and valves in some jobs
Different aims lead to different thicknesses. Insulating only to prevent contact burns may need a different thickness from insulating to save energy. See Surface temperature for personnel protection.
Step 1: check the service temperature
Hot-water pipes in a building and steam pipes in a factory are at very different temperatures, and steam temperature rises with pressure. You need the real maximum system temperature, including start-up and upset conditions, and then compare it with the insulation service temperature the manufacturer states.
| Product | Type and form | Service temperature per manufacturer document |
|---|---|---|
| --- | --- | --- |
| SCG PCI | Glass-wool pre-formed pipe section for steel pipe | 10–540 °C |
| ROCKWOOL ProRox PS 960 SA | Stone-wool pre-formed pipe section, split and hinged | Up to 650 °C |
| ROCKWOOL ProRox WM | Stone wool mat stitched to wire mesh | WM 950 / 960 / 970: up to 650 / 650 / 750 °C |
| ASK CS 220 | Rigid calcium silicate as slabs, curved segments and pipe sections | Type I 650 °C / Type II 1,000 °C |
These figures are material limits; they do not mean every job in that range can go ahead without design. For hot-water pipes at moderate temperatures, closed-cell elastomeric insulation is also an option within its own temperature range. See the comparison table in How to choose pipe insulation.
Step 2: choose the form for the pipe
| Form | Suits | Notes |
|---|---|---|
| --- | --- | --- |
| Pre-formed pipe section | Straight pipes in standard sizes | Fits the pipe closely, quick to install, keeps its shape. ROCKWOOL describes it as the first choice for pipework where it can be used |
| Wired mat | Large pipes, bends, fittings and places where sections are hard to use | Can be cut and shaped to fit; needs fixing and support so it does not sag |
| Blanket (no mesh) | Non-vibrating equipment and vessels | The manufacturer specifies it for non-vibrating equipment; for vibrating equipment consider the wired type |
| Calcium silicate | Points carrying load or impact, and high-temperature work | Rigid, with higher compressive strength than fibrous insulation, but more brittle; must be cut and fitted by specialist installers |
No form suits every location. One piping system usually combines several, for example pipe sections on straight runs and wired mat at bends and valves. Read more on the differences in Slab, blanket and wired mat: what is the difference?
The size of a pre-formed section must match the pipe's outside diameter. See Pipe sizes and insulation bore.
Step 3: fix it and jacket it
Fibrous insulation insulates well when dry. If water gets in, performance falls and the steel pipe underneath is at risk of rusting, so an outer covering is always needed.
- Fixing. Pipe sections are fitted with the lengthwise joint underneath and the joints between lengths staggered, then secured with wire or bands as the manufacturer specifies. Thick or high-temperature work is often done in several layers with staggered joints.
- Metal jacket, such as aluminium or stainless steel, protects against rain, impact and foot traffic. The SCG document describes finishing with aluminium foil or a stainless jacket, while industrial stone-wool pipe sections must be finished with metal cladding.
- Jacket joints must keep water from running in, especially outdoors, and must allow for the pipe expanding when hot.
The rust risk is explained in Corrosion under insulation (CUI).
Thickness comes from design
Thickness depends on pipe temperature, pipe size, ambient temperature, the insulation's thermal conductivity at that temperature, and the aim of the job. Thermal conductivity rises as temperature rises, so use the value at the real operating temperature from the manufacturer's document, not the room-temperature value. Have an engineer calculate it, or send us the details to check. See How thick should insulation be?
Steam and high-temperature work is for specialists
Steam pipes involve both heat and pressure. Insulation must be installed when the system is in a safe condition, and details must be designed at valves, flanges, pipe supports and expansion joints. Valves and flanges left bare are both heat-loss points and contact hazards. Have the designer and an industrial insulation contractor specify and install the work.
Information to prepare before asking
- The fluid in the pipe and its maximum temperature (for steam, give the pressure as well)
- Pipe type, size and outside diameter
- Whether the pipe is indoors or outdoors, and whether people can reach it
- The aim: saving energy, preventing contact, or holding process temperature
- Whether the pipe is carbon steel or stainless steel
For an overview of materials for hot work, see How to choose high-temperature insulation.
Sources
- National Insulation Association — About Insulation (design objectives of mechanical insulation)
- ROCKWOOL Technical Insulation — Pipework page (functions of pipe insulation; choosing between pipe sections, load-bearing mats and wired mats)
- ROCKWOOL (Thailand) — data sheets ProRox PS 960 SA (200 329TH-08/25 V4), ProRox WM 960 SA (200 343TH-08/25 V3), ProRox BL 960 SA (200 352TH-08/25 V4)
- SCG — SCG Insulation for Industrial : Pipe (properties and installation guide)
- ASK — Calcium Silicate CS 220 Product Introduction (distributor copy)
Related products
Categories and example products for this topic
- ROCKWOOL ProRox PS — Split, hinged stone-wool sections to 650 °C with water-repellent WR-Tech.
- SCG PCI / PCIF — Pre-formed glass-wool sections for pipes at 10–540 °C, 1/2–18 inch steel.
- ROCKWOOL ProRox WM — Wired stone-wool mat, 3 grades to 650 / 650 / 750 °C, for steam pipes.
- ASK CS 220 — Rigid calcium silicate, Type I 650 °C / Type II 1,000 °C, high compressive strength.
Pipe insulation · Glass wool
SCG PCI / PCIF
- Pipe size
- ½–18 in
- Thickness
- 25–50 mm
- Service temp.
- 10 – 540 °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 · 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