Ceramic fabrics are high temperature textiles made from refractory fibres that are drawn, spun into yarn and then woven, braided, knitted or felted into a flexible sheet. Because the fibre itself survives temperatures that would destroy an organic fibre, the fabric keeps its shape where a conventional textile would embrittle, melt or burn. Common fibre families include alumina, aluminosilicate, mullite and nitride based materials, each with its own limits on temperature, chemical attack and mechanical strength. The fabric is only one part of an insulation system: it normally sits against a hot surface behind a protective board or a cladding sheet, and it is fixed by anchors, screws or a wire mesh depending on the geometry of the installation.
The route from fibre to finished textile matters more than it first appears. A fibre that is too stiff will not knit cleanly, a yarn with a twist that is too low will fray, and a weave that is too open will let hot gas reach the back of the insulation. The manufacturer controls the blend of fibre grade with a small amount of sizing or binder, decides the yarn count, then sets the picks and ends per centimetre. The result is a fabric with a defined areal weight, a known thickness and predictable behaviour under tension. Flexibility is the reason textiles are used in place of board around pipes, flanges and irregular shapes, and it is also why the material needs a facing layer, since a textile alone offers little mechanical protection.
The chemical composition of the fibre sets the temperature at which the fabric begins to lose strength. Alumina based fibres give the highest temperature capability and resist chemical attack, but they cost more and can be difficult to bend. Aluminosilicate fibres offer a lower cost for a slightly lower limit and remain the most widely used in furnace and kiln insulation. Mullite fibre is used where resistance to thermal shock and to alkaline conditions matters. Nitride based fibres are chosen mainly where specific thermal and electrical conductivity requirements exist. As a rule, the working temperature of a fabric is lower than the melting behaviour of the fibre would suggest, because strength loss starts well before the material melts.
Additives and binders also influence behaviour. A small amount of organic or mineral binder holds the yarn together during weaving, and this binder is the part of the fabric that burns out first at temperature. Binders chosen for easy removal leave less residue after the first heat-up, which matters in a kiln with sensitive product surfaces. Confirm whether the fabric is supplied ready for service or requires a first heat-up to remove the binder.
Areal weight, expressed in grams per square metre, is the usual way textile insulation is ordered, and thickness usually follows from the areal weight and the bulk density of the fibre. Higher areal weight gives more resistance to heat flow but also places more mass on the anchoring system. Specify thickness where the geometry is tight, because a fabric that is too thick may not fit between an existing support structure and the casing. Where the hot face is curved, check the minimum bend radius for the material and grade chosen, since a tight bend applied cold can break the fibre at the fold.
| Property | Why it matters in service |
|---|---|
| Areal weight | Usual ordering unit in g/m2 and the main driver of heat flow |
| Thickness | Derived from areal weight and fibre bulk density; check fit in tight sections |
| Width | Common rolls are 1000 mm or 1200 mm; confirm usable width after seaming |
| Fibre colour | Usually white to cream; a different shade may indicate a different fibre family |
| Binder | Some grades are supplied with an organic binder that burns out on first heat-up |
Other characteristics are worth recording. Stitching and selvedge details affect how the roll is joined, and the weave should be dense enough to hold the fibre but open enough to let moisture escape. Where the fabric forms a hot-face layer, note the surface texture, because a smooth surface is easier to clean when deposits form.
Tensile strength is measured in newtons per centimetre of width and is usually quoted at room temperature, since the strength of all ceramic fibres falls as temperature rises. A specification should always state the test method and the specimen width, because a value quoted per centimetre and a value quoted for a full strip are not directly comparable. In service the fabric is rarely loaded to its tensile limit, but handling during installation, vibration in a duct or a rubbing edge on a nozzle can break individual yarns long before the textile fails as a whole.
Abrasion and flex cracking are the usual causes of early failure. A fabric that rubs against a sharp edge will lose fibres, and a folded or crushed bundle will break at the crease. Install with generous radii, cut with sharp tools to avoid fraying, and avoid compressing the material between tight clamp faces. Where a fabric forms part of a removable jacket, specify a design that allows the cover to be opened without pulling on the textile.
Thermal conductivity of a textile insulation increases with temperature and also rises when the material is compressed, so the design value should be taken at the mean temperature of the layer rather than at ambient. Fibre conduction, gas conduction between the yarns and radiation between the fibres all contribute, and the balance shifts as temperature climbs. This is why an experienced operator keeps the fabric loose and full with no hollow channels, and why a gap left during installation can be more damaging than a slightly lower areal weight. Where a design uses the textile in several layers, stagger the joints between layers.
Service temperature combines chemical stability and mechanical strength. A fabric may survive a short peak excursion above its nominal rating without visible damage, but continuous operation above the rating causes gradual loss of strength that appears as shrinkage, cracking or anchor pull-out. Note the number of temperature cycles the duty involves, because cyclic service is generally more demanding than steady service at the same average temperature. A hot-face fabric is also exposed to gas velocity and dust, which erode the surface, so a facing board is often added for that reason.
Alumina and aluminosilicate fibres are broadly resistant to most furnace atmospheres, but they are attacked by some fluxes, by alkali bearing dust and by certain metal oxides that form low melting eutectics with the silica content of the fibre. Molten metal splashes, salt fluxes and cementitious dust in a mixed plant are the situations where a generic grade fails. When the environment contains such materials, ask for a grade selected for that specific atmosphere and check whether a protective facing layer is required to keep the fibre clean.
Interaction with adjacent materials also matters. Calcium silicate and other rigid boards can be hygroscopic and should be protected from moisture by the cladding, and coated steel surfaces may be affected by the binder during first heat-up. Coatings that contact the fibre can stick to it, so they should be fully cured before the lining is closed. A short compatibility check with the other materials in the assembly avoids most unexplained lining failures.
Acceptance should start with a check of the material delivered against the order: fibre family, areal weight, width, roll length and colour. A certificate of analysis for the fibre chemistry and a test report for tensile strength, thickness and mass per unit area let a quality department verify the batch. Where the fabric will run hot, a thermal shrinkage figure at the working temperature is more informative than a room temperature measurement.
| Check | What it confirms | Typical acceptance approach |
|---|---|---|
| Fibre composition | Temperature capability and chemical behaviour | Certificate of analysis against the agreed grade |
| Areal weight and thickness | The heat flow calculation behind the design | Verify against the ordered value on the delivery note |
| Tensile strength | Handling durability during installation | Test report with stated method and specimen width |
| Dimensional stability | Resistance to cracking and shrinkage in service | Thermal shrinkage figure at the working temperature |
| Binder and first heat-up | Residue and smoke release at start-up | Confirm binder type and the burn-out schedule |
| Width and roll length | Joint layout and material wastage | Check usable width after seaming |
On site, keep the material dry and clean, store rolls off the floor and avoid opening them long before installation. Any wet or contaminated section should be cut out rather than installed. Cutting should be done with a sharp blade or shears, edges bound where fraying is likely, and joints staggered so that no straight line of weakness runs through the layer. Photograph the completed installation before the cladding is closed, because that record is valuable when a hot spot appears later.
Start from the required heat flow or surface temperature at the coldest part of the insulation, then work backwards to the thermal resistance needed at the mean temperature of the layer. The result is a minimum areal weight, to which a margin is added for compression, for joints and for normal product variation. Do not select by rule of thumb from pipe diameter alone, and remember that the cladding, the fastening and any air gap change the result. Ask for a calculation based on your actual service temperature and insulation thickness.
Yes. The material is designed to be cut, folded and shaped, which is one of its main advantages over rigid board. Cut with sharp shears or a knife on a hard surface, allow generous bend radii, and bind or tape the cut edge if it will be exposed to gas flow or vibration. Re-cut and re-tie a damaged section rather than patching it with tape, since a taped joint traps heat and creates a local hot spot. A template made on site is the most reliable way to fit a jacket around a complex fitting.
They are the same family of fibre in different forms. Woven cloth is a flat sheet used for linings and jacketing, tape is a narrow strip for seams and for wrapping small diameters, rope is a round form for plugs and irregular penetrations, and mesh is an open structure used as a carrier or support for other materials. Open forms have lower mass and better conformability but less resistance to direct gas flow, so they are normally combined with a facing layer. Specify the form that matches the geometry rather than the one that is easiest to cut.
Store rolls in their packaging, in a dry place, off the ground and away from moisture or contamination. Do not cut a roll until the installation sequence is clear, because opened material picks up shop dirt. Bring the lining to a slow, controlled heat-up: a staged ramp reduces the risk of cracking the textile and allows any binder to burn off without a sudden release of smoke. Keep a record of the ramp used and inspect the surface after the first full cycle for signs of dusting, shrinkage or anchor movement.
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