Jointless kiln insulation, without use of cordierite

by Adam Slater, International Sales Director

In a wide range of ceramic firing applications, kiln builders have quite often elected to fix cordierite tiles to the hot face. Cordierite is an aluminosilicate refractory that is characterized by a low and uniform thermal expansion and low creep rate, making it ideal for use in an area that is subjected to prolonged, direct high temperature conditions as well as repeated heat up/cool down cycles.

Cordierite – as opposed, say, to silicon carbide – is relatively inexpensive and is easily cut/shaped. It can also, for the most part, be accurately and quickly fixed into place. This provides a hard cover over the traditional ceramic fiber used to insulate the kiln walls and roof.

Kiln with Jointless system on walls, and cordierite roof coveringKiln with Jointless system on walls, and cordierite roof covering

This system has over a number of decades been favoured by some ceramic manufacturers and is in some ways effective in preventing the ingress of kiln dirt. This is particularly important where the firing of whitewares such as sanitaryware and tableware is concerned, as the presence of any contaminants from a damaged lining is likely to cause glaze faults and lead to higher loss rates.

There are, however, a number of notable disadvantages associated with the use of cordierite cover tiles. The first of these is the fact that this type of ceramic kiln lining adds to the weight of material to be heated on every cycle, so the fuel consumption is increased by up to 15%, considerably increasing a kiln’s operating costs over time. Additionally, the supports or clips used to support these tiles need to be made from a high temperature ceramic and so they conduct heat to the kiln shell, which is undesirable. This system also results in a hotter kiln shell and roof.

Of course, cordierite tiles provide an effective solid cover over the fiber, but this leads to another downside – shrinkage gaps in the fiber, should they occur, need to be rapidly rectified in order to retain the integrity of the kiln lining. If they are hidden behind a cordierite tile then they can go unnoticed until hot spots or damage is seen on the outside of the kiln. This causes more expense, both in terms of fuel (heat will have been lost through any gaps) and kiln repairs. There’s further bad news if contamination results from organics attacking untreated fiber.

Improved All-Fiber Lining

So, all-fiber kiln linings are preferable but they need to be constructed in such a way as to avoid the pitfalls associated with having a patchwork of fiber on the roof and walls. Consequently, for ceramics being fired up to a temperature of 1,350ºC (2,460°F), Nutec Bickley uses its patented ceramic fiber Jointless® modules, providing manufacturers with minimal maintenance, enhanced fuel economy and extended service life.

Our Jointless system consists of monolithic ceramic fiber modules engineered to cover a complete kiln wall, door, or roof. It’s a one-piece construction continuously shaped with ceramic fiber blanket folded and anchored. Jointless modules not only eliminate the joints between smaller modules (as commonly found in ceramic fiber linings), but also eliminate the gaps typically located around the flues which require higher maintenance. It’s important to note that a well installed and maintained Jointless fiber lining will not cause kiln dirt, thus eliminating one of the key reasons to consider the cordierite tile alternative.

A Jointless lining is simpler to install and is also more effective. For instance, it’s much easier to seal around updraft exhaust flues, which are otherwise notoriously prone to damage and leakage. The whole system is less expensive than fiber covered with tile.

Jointless ceramic fiber modules – also manufactured by Nutec Bickley – provide a low density insulation solution. They offer significant in-use advantages, enabling our kiln customers to minimize heat waste and reduce fuel consumption.

It should be borne in mind that cordierite tiles act as a heat sink, whereas Jointless modules don’t store heat and therefore allow for faster heating and cooling, resulting in significantly improved kiln response as well as lower operating costs.

Assuming there is no impact damage to the fiber modules, customers can expect to see a much reduced need for maintenance. Jointless installations typically last over 10 years with minimal maintenance, which is a marked contrast to traditional, modular all-fiber kiln linings.

For further details on the Jointless® system, and how to get the best out of your kiln insulation, contact:

Adam Slater, International Sales Director

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