Ceramic fiber furnace linings should be repaired in time when shrinkage joints or damage and detachment occur under long-term high temperature to extend the service life of the overall furnace lining and ensure safe operation of production.
Repair of shrinkage joints
Ceramic fiber furnace linings with gaps wider than 5mm should be repaired. The same grade of ceramic fiber blanket is used for filling. The ceramic fiber blanket should be stuffed into the gap as much as possible until it cannot be squeezed. Make sure that the gap is filled and squeezed tightly, and do not only fill the surface, otherwise it will fall off again after a short operation.
Repair of standard ceramic fiber module detachment
After the standard ceramic fibre module is damaged and detached, a ceramic-fiber module of the same size is used for repair. Re-weld the anchor nails at the original anchor nail position, lay the ceramic fiber blanket backing, and install the fiber module. Compress the ceramic fiber blanket between the two rows of modules in the non-folding compression direction to compensate for the shrinkage. For the larger gap between the replacement module area and the unreplaced modules around, fill it with ceramic fiber blanket.
Repair of falling off special-shaped ceramic fiber modules
After the special-shaped ceramicfiber modules (such as corner modules, arc modules, etc.) are damaged and fallen off, they are repaired by laying ceramic fiber blankets in layers. That is, long anchor nails are welded, and then ceramic fiber blankets are laid layer by layer. The thickness of the laying is consistent with the original furnace lining, and finally the surface layer is fixed with ceramic cups. The reason why the method of laying ceramic fiber blankets in layers is changed to repair is that, on the one hand, there is generally no corresponding special-shaped module preparation after the special-shaped ceramic fiber modules are damaged and fallen off. On the other hand, after the special-shaped modules are damaged and fallen off, the special-shaped modules that have not fallen off have also shrunk and lost their elasticity after a long period of high temperature. If the same special-shaped modules are used for repair according to the original structure, the contact between them and the replaced special-shaped modules will not be compact enough, which will become a hidden danger point. After high-temperature operation, rapid shrinkage and gaps will appear, which will cause the furnace lining to be damaged and fall off. By adopting the structure of laying ceramic fiber blankets in layers, the ceramic fiber blankets can be cut larger than the damaged and fallen off area. In this way, the compression amount can be reserved for compression laying at the contact with the special-shaped modules that have not fallen off, which solves the above problems. After the corner module of the cracking furnace roof of a petrochemical plant and the corner module of the steam superheater hoisting hole of the styrene unit fell off, they were repaired with a layered structure. After the repair, the operation effect was good.
Precautions
1) The ceramic fiber module furnace lining will shrink under high temperature. This is determined by its own properties and is caused by crystallization and grain growth at high temperature. High-temperature shrinkage causes cracks in the furnace lining, forming gaps, and eventually it is damaged and falls off under the action of long-term high-temperature flame airflow.
2) The size, quality error, construction quality defects and human factors of the ceramic fiber material itself can accelerate its damage and fall off, affecting its service life. Therefore, it should be paid attention to during installation, inspection and maintenance construction.
3) After the ceramic fiber furnace lining is damaged and falls off, it should be repaired according to the original structure if it can be repaired according to the original structure. For those without the original model material, the layered ceramic fiber blanket structure can be used for repair.
