Refractory materials occupy a central place in the glass industry, guaranteeing both the longevity of the equipment and the efficiency of the processes. However, poor selection or deficient quality of refractory products can lead to costly and unforeseen failures. This real-life case highlights the consequences of installing non-compliant refractory materials, by analysing the collapse of the regenerator crown arches of a glass furnace.
The context: a rapid and unexpected failure
Less than 18 months after the commissioning of a new bottle glass furnace, a customer observed significant sagging of the crown arches in the regenerators. These arches, although essential to ensure heat exchange and the durability of the furnace, were showing worrying signs of structural degradation.
Faced with this situation, we carried out an in-depth analysis of the refractory materials used, together with an audit of the suppliers involved.
Diagnosis: non-compliant refractory materials
1. Non-compliance of the refractory materials
The crown arches were to be manufactured from sillimanite, a high-performance refractory product suited to the extreme conditions of glass furnaces. However, the chemical and mechanical analyses revealed that the arches were in fact made of a silico-aluminous material doped with ground calcined alumina.
Unlike sillimanite, this material displays inferior characteristics, notably:
- A lower density, affecting mechanical strength.
- A high thermal expansion, poorly compatible with repeated thermal stresses.
2. Defects in the creep-under-load tests
The creep-under-load tests carried out on receipt of the arches failed to detect the excessive shrinkage of the silico-aluminous material. The cause: an initial firing defect in the product.
During the temperature ramp-up for the test, the material, still only partially fired, continued its firing process, causing unusual expansion. This expansion temporarily offset the sagging typical of a poorly formulated silico-aluminous material, thereby masking the non-compliant characteristics of the product.
This phenomenon led to a false impression of compliance, preventing the detection of the defects before installation. Unlike sillimanite, which offers reliable thermal stability from manufacture onwards, this badly fired silico-aluminous material was unable to withstand the extreme conditions of the glass furnace over the long term.
3. Chemical indicators overlooked
During the initialinspection of the arches, the chemical analysis carried out by the customer focused solely on the main values, notably the Al₂O₃ (aluminium oxide) and SiO₂ (silica) contents. These parameters were in line with expectations for a product supposed to be sillimanite-based.
However, the TiO₂ (titanium dioxide) content, a key indicator of the real nature of the product, was overlooked. Yet this value was nearly three times higher than the reference value for a sillimanite-based refractory material. Such a TiO₂ content should have raised the alarm about a probable substitution with a lower-quality silico-aluminous material.
This error of interpretation underlines the importance of an exhaustive chemical check and of particular attention to secondary elements, which can reveal inconsistencies in the composition of refractory materials. An in-depth analysis could have avoided the installation of non-compliant refractory materials and prevented the collapse of the arches.
Consequences of the failure
- Prolonged shutdown of operations
The collapse of the arches required an immediate shutdown of the furnace for emergency repairs, severely disrupting the production schedule. - High repair costs
The replacement of the non-compliant arches and the repair work generated substantial costs, made worse by the urgency of the situation. - Energy and environmental impact
Even before the collapse, the degradation of the arches had reduced the thermal efficiency of the regenerators, increasing energy consumption and the associated CO₂ emissions.
Lessons learned and recommendations
1. Securing the quality of refractory materials
The choice of suitable refractory products is crucial. Sillimanite, although more expensive, offers thermal stability and chemical resistance that are ideal for regenerator crown arches. Investing in higher-quality refractory materials makes it possible to avoid costly failures in the long term.
2. Conducting a rigorous supplier audit
A supplier audit is indispensable to guarantee the compliance of refractory products. It includes:
- An assessment of the manufacturing processes.
- Quality checks on the products delivered, including chemical and mechanical tests.
- A verification of the certificates of conformity provided by the manufacturer.
3. Carrying out in-depth analyses before installation
It is crucial to carry out validation tests under conditions close to real use. Chemical indicators, such as the Fe₂O₃ content, must be systematically analysed in order to identify any anomaly likely to affect the performance of the materials.
4. Working with technical experts
Calling on refractory materials specialists to supervise the selection and installation of the products makes it possible to anticipate and prevent this type of error.
Conclusion: prevention is essential
This case illustrates the serious consequences of a quality defect in the manufacture of refractory products. The collapse of the arches could have been avoided through rigorous selection of materials, a supplier audit and detailed chemical analyses.
In the glass industry, where thermal and mechanical stresses are extreme, vigilance is required at every stage, from design through to the maintenance of the equipment.
Solid technical expertise and rigorous quality control processes remain your best allies in guaranteeing the durability and performance of your installations.
Xavier Schuster
Consultant at SXE Consulting. Industrial consulting firm based in Luxembourg, 25 years of experience in operational excellence.
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