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Industrial furnaces and boilers rely on refractory or ceramic fibre linings to contain heat and protect equipment. When these linings fail, online hotspot repair becomes crucial to avoid costly shutdowns. Technicians use thermal imaging technology, supported by standards like API guidelines, to detect hotspots early and prevent further damage.
Refractory failures often occur due to corrosion of the anchors holding the refractory or ceramic modules in place. This corrosion can be caused by high temperatures or corrosive elements in flue gases.
This is exacerbated in high humidity environments, where the water content in the combustion air is high. When high water content flue gasses seep through cracks in the refractory or ceramic modules, the water can condense when it comes into contact with the cooler casing temperatures on which the anchors are welded on.
This combined with corrosive elements such as Sulphur or salts from coastal facilities, forms ideal conditions for aggressive corrosion to take place, weakening the anchors and potentially leading to refractory lining failure or perforations/pinholes in the casing.
Figure 1: Flue gas condenses on the cold roof plate through gaps in the refractory lining, corroding the anchors.
Figure 2: Yellowish sulfurous deposits appear between the refractory and furnace casing plate, caused by flue gases seeping through cracks.
Figure 3: Cracked insulation shows corroded anchors detached from the casing. This image was taken after cutting the external furnace plate during inspection.
Poor installation can lead to refractory failures. Gaps or improperly secured modules allow hot flue gases to penetrate the lining, accelerating corrosion. To prevent this, installers must seal all gaps and use high-quality anchoring systems. Special care should be taken at transition points, where compressed blankets or fillers must fully cover interfaces.
Ceramic fibre modules and vacuum-formed ceramic systems (like peepholes) shrink when heated for the first time. Even if inspections after installation show all gaps sealed, shrinkage during initial heating can create new gaps, causing hotspots on casings.
To avoid this, manufacturers should pre-shrink vacuum-formed components before installation to prevent unexpected shrinkage and hotspot formation.
Cementitious and water-based refractory materials require careful drying during initial startup. If water pockets remain trapped and the furnace heats too quickly, the water turns to steam, causing mini steam explosions that fracture or even collapse the refractory lining.
Experienced applicators recommend a curing curve that guides operators on gradual heating to allow proper drying. When restarting furnaces after prolonged shutdowns or high humidity exposure, operators should also allocate time to dry the existing refractory lining.
Failures such as malfunctioning or unsecured cuplocks in blanket-type installations can damage the lining. Once cuplocks fail, exposed anchors corrode rapidly due to high temperatures. The blankets start to sag and dislodge, increasing stress on nearby anchors and causing a chain reaction of failures.
Regular inspection and maintenance of anchoring systems are essential. These tasks should be part of all turnaround and maintenance inspection programs.
Damaged or poorly tuned burners can cause flame impingement, leading to localized overheating or “licking” that damages refractory materials. High-velocity flue gases at furnace transition points create turbulence, causing mechanical wear, erosion, and hotspots on furnace casings.
Proper burner maintenance and furnace design help minimize these risks. In areas with very high velocity or turbulence, applying a protective lining such as 3M Nextel lining systems can provide extra durability.
Thermal cycling, emergency shutdowns, prolonged exposure to extreme temperatures, and abrasive particulates in flue gases also contribute to refractory degradation. Furthermore, poor material selection, insufficient refractory thickness, and operational deviations can worsen damage.
If you face refractory failure and cannot shut down your unit without significant losses, Online Hotspot Repair is your best option. KLAY EnerSol specializes in these emergency repairs, saving clients substantial costs by avoiding unplanned shutdowns.
Their method involves cutting the external casing near the failure, inserting a custom high-temperature backing system, and filling the cavity with a proprietary compound. This compound cures while the furnace operates at full capacity, enabling repairs without slowing or stopping production.
In conclusion, refractory failures in furnaces and boilers can stem from various factors. Addressing these challenges requires proactive measures such as robust material selection, meticulous installation practices, regular maintenance, and adherence to operational best practices. By mitigating the risks associated with refractory failures, industries can ensure operational reliability and efficiency.
Need urgent assistance? Contact us for expert online hotspot repair solutions.