Ceramic Fibre 101: Light, Fast, and Not for Every Job

Ceramic fibre is the featherweight of the refractory world. Fast on its feet, excellent in the right fight, and folded in half by anything with abrasion in its corner. Used in the right place it saves real fuel and installation time. Used in the wrong place it disappears in a week.

What it actually is

Ceramic fibre is a spun or blown mineral wool, usually an alumino-silicate, sometimes a low-biopersistence alkaline-earth-silicate wool, and for the highest temperatures a polycrystalline mullite fibre. It is sold by classification temperature (common grades sit around 1260, 1400, and 1430 °C, with polycrystalline grades higher) and by density.

You will meet it as bulk, needled blanket, rigid vacuum-formed board, folded modules mounted on studs, plus paper, felt, rope, and coatings. Blanket and modules do most of the work in furnace linings.

Why reach for it

• Very low thermal conductivity. It insulates as well as much thicker dense brick.
• Almost no thermal mass. A fibre-lined batch furnace heats and cools fast, which on a cycling operation is a large fuel saving.
• Light. It adds very little load to the steelwork, so shells and doors can be lighter.
• Thermal-shock proof. It does not spall. You can quench it and it does not care.
• Fast to install. Modules go up in blocks against the casing.

Higher density helps it resist gas erosion and slightly lowers conductivity at high temperature, at more cost and weight.

Where it falls down

It insulates like a dream and defends like a napkin.

• Abrasion and impact. Moving solids or a knock will tear the face.
• High gas velocity. Fast flue gas erodes fibre. It needs a rigidiser, a higher density, or a dense hot face in front of it.
• Slag, molten metal, and glass. Direct contact dissolves it.
• Reducing, alkali, or steam-laden atmospheres. These attack the silica, cause devitrification, and drive permanent shrinkage.
• Fluxing dust. Alkali and iron-oxide dust settle, melt, and form a brittle glaze that spalls off and takes fibre with it.

Fibre also shrinks permanently at temperature over time, so joints have to be laid with overlap and compression, never butted loose.

Making it last

Spray the hot face with a colloidal silica or alumina rigidiser to resist gas erosion. Stagger blanket joints and compress module joints so shrinkage does not open gaps. Where the process is dirty, fast, or abrasive, run fibre as backup behind a dense hot face rather than as the working lining.

One handling note: refractory ceramic fibre carries a possible-carcinogen classification, which is why bio-soluble AES wools exist. Whichever grade you use, control the dust: local exhaust, respirators, no dry sweeping.

Ceramic fibre belongs in clean, low-velocity, low-abrasion heat: annealing and heat-treatment furnaces, ceramic kilns, petrochemical heaters, and backup insulation almost anywhere. Keep it away from slag, scrubbing gas, and moving charge.

The short version

If the furnace is clean and cycles often, fibre is frequently the best answer and pays for itself in fuel. If the zone sees wear, velocity, or chemistry, put something dense in front of it. Our insulation range covers blanket, board, and modules across the grade range: see the products or tell us the furnace and we will help place it.