Repair
Linings often require some form of repair to achieve its full potential.
Products
Most repair materials are relatively fine-grained chemically bonded products.
| Area | Product Name | Product Description | Bond | Max service temp. / °C |
| Plastics | Capram 60 | Phosphate bonded high alumina zircon enriched plastic and repair mix | Chemical | 1600 |
| Capram 70 | Phosphate bonded high alumina plastic and repair mix | Chemical | 1700 | |
| Capram 90 | High grade high alumina patching and topping material | Chemical | 1800 | |
| Repair materials | D10 Plaster | Alumino-silicate patching plaster | Chemical | 1700 |
| D10F | A finer version of D10 Plaster | Chemical | 1700 | |
| D11 | High grade high alumina patching material | Chemical | 1800 | |
| Capram 90F | High grade high alumina patching and topping material | Chemical | 1800 | |
| Capram 90P | High grade high alumina patching material | Chemical | 1800 |
Procedure
The patching material should be smeared over any cracks, but should not be squeezed into cracks otherwise this can prevent the crack closing when the furnace is heated up (see digram right).
Short-former Repair
Lining lives can be extended by carrying out a short-former repair. This can be carried out on a lining that has worn by around half of its original thickness to leave a minimm of 30-50 mm of sidewall; this ensures that some protective unreacted powder is retained.
On the charge prior to the repair an alloy should be chosen to give minimum slag retention; it is also advisable to raise the metal temperature significantly(~50°C higher than normal) to remove as much residual slag as possible. The lining then needs throughly cleaning to remove metallic and slag impurities on the surface. It is usually advisable to remove the topping to gain better access to the lining.
A short-former is essentially a former without the base and typically 30-50 mm smaller in diameter. It does not need to be as thick as a full former: 3mm rather than 5 mm. It is located as vertically as possible and anchored in place. A ring of patching material is positioned at its base to seal it against the linng; this stops lining material from falling through to the bottom of the furnace.
The lining is then vibrated into place - typically by hand spiking because the former is not as robust and the seal will probably give way under strong vibration. The topping can then be applied as normal. We recommend that the lining should then be sintered by the liquid-sinter method with the usual pre-heat (30-60 mins).
