Refractory Ceramic Fiber Blanket | Bell-Type Furnace Lining Solution | CCEWOOL®

Bell-type furnaces are typical intermittent heat treatment furnaces widely used for bright annealing and heat treatment. Their basic structure usually includes a furnace base, inner cover, and heating hood. Workpieces are placed on the furnace base, enclosed by the inner cover, and heated from the outside by the hood. Depending on charging arrangement, bell-type furnaces are generally classified as square or round types. Their operating temperature is usually 650–1100°C.

For bell-type furnaces, lining design is not only about temperature resistance. It must also achieve heating hood lightweighting and energy saving. This is why traditional lightweight brick or castable structures are increasingly being replaced by ceramic fiber lining systems with lower weight and lower heat storage. The main advantages of CCEWOOL® ceramic fiber blanket and related ceramic fiber products in heating hoods come from their low thermal conductivity, low heat storage, and low density.

Furnace Structure and Temperature Range: Why Bell-Type Furnaces Are Better Suited to Lightweight Ceramic Fiber Linings

In a bell-type furnace, heat is supplied by the heating hood and transferred through the inner cover to the workpieces. Therefore, the weight, heat storage, and insulation efficiency of the heating hood directly affect the thermal performance of the whole furnace.

Although the overall furnace temperature is usually 650–1100°C, heat load is not the same in all areas. The burner zone has the highest heat load, the large hood area above it is the secondary high-temperature zone, and the backup and cold-face areas are lower in temperature. For this reason, the lining should be designed according to the heat-load gradient of each area, rather than using one material for the whole hood.

Burner Zone: Ceramic Fiber Module + Ceramic Fiber Blanket Composite Structure

The burner zone is the area with the highest heat load and the strongest gas flow erosion, so it requires better insulation performance, structural stability, and erosion resistance.

For this area, CCEWOOL® recommends a 1260°C ceramic fiber module + ceramic fiber blanket composite structure. The hot-face layer uses 1260°C CCEWOOL® ceramic fiber modules, while the backup layer uses 1260°C CCEWOOL® ceramic fiber blanket. The modules may be arranged in a soldier-course pattern and use angle-iron or suspended structures, depending on furnace design.

This structure is better suited to concentrated heat-load conditions. It improves insulation and erosion resistance while also helping maintain lining flatness, sealing performance, and a lighter hood structure.

Areas Above the Burner Zone: Layered Refractory Ceramic Fiber Blanket Structure

In the large hood area above the burner zone, CCEWOOL® recommends a layered ceramic fiber blanket structure. This lining is usually installed in 6–9 layers, fixed with heat-resistant steel studs and clips. The section approximately 150 mm near the hot face uses 1260°C grade CCEWOOL® refractory ceramic fiber blanket, while the remaining layers use 1100°C CCEWOOL® ceramic fiber backup blanket.

This “higher grade at the hot face, lower grade behind” design is better suited to the actual heat-load conditions of this area. It helps ensure sufficient temperature margin while also controlling cost, weight, and heat storage.

The main advantages of this layered ceramic fiber blanket structure are:
Reduced heating hood weight
Lower heat storage and lower non-productive energy consumption
Better sealing and insulation through staggered joints

Product Grade Selection Logic: Zoned by Heat Load, Not a Single Product Throughout

CCEWOOL® refractory ceramic fiber products cover temperature grades from 1100°C to 1430°C, including bulk, blankets, modules, boards, vacuum-formed shapes, paper, and textiles. This means bell-type furnace lining design should not rely on a single product throughout the whole hood, but instead use different grades in different areas according to heat load, structure, and installation needs.

When a bell-type furnace heating hood adopts a full ceramic fiber lining, the main benefits are:
A lighter hood, reducing steel load and lifting demand
Lower heat storage, better suited to intermittent furnace operation
Easier and faster installation
Better insulation performance, reducing external heat loss and energy consumption
Conclusion

For bell-type furnaces, an effective lining solution is not just one that can handle 650–1100°C, but one that clearly distinguishes the burner zone, the hood area above the burner zone, and the backup area, then matches them with suitable grades of CCEWOOL® refractory ceramic fiber blanket and ceramic fiber modules.
Only with this zoned configuration can a bell-type furnace heating hood achieve lightweighting, easier installation, and better energy efficiency at the same time.