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Admittedly, the search for possible sources of fault for a prematurely aborted firing can sometimes be quite complex, especially if the fault only occurs sporadically. Even with damage such as the one shown in the image, a specialist should be called in – this requires considerable work. Locally, we carry out such repair and maintenance service upon request.
Fig.: Inside of a kiln with broken heating elements, support tubes and bottom shelf
1) Common wear parts inside the kiln
The kiln pictured here hasn't had any preventative maintenance performed for a long time. We only received a call when the kiln was no longer able to reach its final temperature and the user could see a corresponding error message on their control panel. The cause of this is a defect in common wear parts such as heating elements and the corresponding support tubes. In this kiln, the support tubes and heating elements are broken in several places. A complete replacement is recommended, as the heating elements have developed extreme "nests" over time. The resulting uneven temperature distribution not only damages the fired ware, but also causes local overheating in the heating elements, melting them and breaking the support tubes!
If a heating element has been damaged due to an accident, such as glaze running down, then of course just a single element can be replaced. However, if there is extensive wear, it is not a good idea to replace the heating elements one after the other every few weeks - they should be done all at once! Soiled support tubes, especially those with melted deposits, should always be replaced together with the heating elements. Melt residue would pose a very high risk of a new heating element burning out in exactly the same place! If the support tube is only broken and the heating element appears to be undamaged, then the user can usually temporarily fix the defective support tube until the next element change. Replacing the support tube at this point would carry a high risk of damaging the recently intact heating element!
Over time, the base shelf covering the heating element grows by a few millimetres. Please don't wait until the base shelf completely bulges upwards; replace it as soon as there is no longer any air gap between the shelf and the recess. Otherwise, forces will develop that would completely damage the kiln insulation (as can be seen in the cracks in the collar stones on the door). Unfortunately, repairing the collar stones is very time-consuming, and sometimes the repair results aren't entirely satisfactory!!
2) Damage to the kiln insulation
The range of defects is quite diverse! There are numerous minor defects, most of which are purely cosmetic. These defects are often irreparable, or the risk of causing even more damage during repair attempts would be quite high (e.g., cracks in the grooved or lid bricks of a top-loading kiln). If larger fragments of the lightweight refractory brick insulation remain intact, they can be reattached using our repair kit 1145 (or similar). Often, replacing the entire affected area (e.g., the entire cover, base, or extension ring) is the better solution for a top-loading kiln, as long as this is still economically viable.
Fig.: Worn kiln contactor with clear traces of smoke
3) Electrical and mechanical elements in the switch case
These components are often neglected during regular maintenance, even though they are very important! This includes, for example, the temperature sensor (thermocouple). It is subject to annual drift, which is particularly significant if the ceramic protection tube is damaged. If you don't want to get used to setting the final temperature 20°C higher after a few years than in a new kiln (in order to achieve the same firing result, mind you), then the thermocouple must be replaced.
Other electromechanical components should also be replaced preventively if signs of damage are already apparent, such as broken heating element lead-through tubes or burnt cables (both of which, unlike the connection terminals, are not included with new heating elements). Electromechanical contactors, in particular, are designed for approximately 1,000,000 load cycles. If the kiln still has a traditional contactor, this number can add up quickly, meaning that, depending on the intensity of use, replacement is due every 1.5 to 5 years. Otherwise, there's a great risk that the contactor contacts will stick together, and the kiln will blow up! Along with the contactors, the built-in interference suppressor (suppression element) must also be replaced to ensure the new components last a long time!
Fig.: Pitting corrosion at an old kiln (side, door, roof)
4) Steelwork
While modern kilns are often double-walled, meaning they are ventilated from behind, older kilns are more prone to rust in various places. To ensure stability, the kiln body must be reinforced in the event of pitting corrosion. If this is no longer possible, the kiln must be shut down.
Conclusion:
This list is not exhaustive. Depending on the kiln model, other wear parts may need to be replaced, such as exhaust air flaps, transport castors, or even connecting cables and plugs. Since an unmaintained kiln poses a high risk (fire and electric shock hazard), it is very important that regular maintenance work is performed according to the operating manual. It is best to have maintenance performed by a specialist company, which will then inspect the kilns. In Germany, this maintenance must be executed in accordance with the German Industrial Safety Ordinance and the German Insurance Association DGUV V3(4) (in accordance with DIN VDE 0701-0702). As described in the first paragraph, we are happy to carry out this work regionally.