Metal Refractory Anchor Failures

Determining the Cause(s)

Background

Failures of refractory anchor systems can be expensive. At CERAM, we have developed the expertise to carry out regular inspections of kilns as well as provide independent analysis in determining the reasons for anchor system failures. We aim to increase awareness about potential failure points in order to encourage regular monitoring and replacement before failure, as well as proactive prevention: CERAM can also assist in the development of anchor composition materials to withstand the individual kiln operating conditions.

CERAM have identified a number of potential causes for refractory anchor failure:

• Mechanical fatigue
• Incorrect material selection or supply
• Deleterious components from combustion processes (acid gas attack)
• Thermal overload / fatigue
• Incompatible material combinations
• Poor weld or weld stresses.

Methodology

In order to determine the cause of failure, a range of investigations can be carried out.

1. Initially, we would take high resolution colour photographs of the parts in their received (failed) condition. This has proven critical for potential legal claims on supplier, installer, and operator. These photographs would be aimed at confirming and detailing scales and deposits on anchor and lug surfaces, including tack weld and fillet weld plus any fracture surfaces, as well as overall geometry and dimensions (to compare with the specification).



2. The lug and anchor steels would be analysed to confirm the base material alloys conform to expectation and specification.



3. Deposits and scales would be analysed to determine the presence of a range of possible contaminants / phases.



4. Any fractured surfaces are found using scanning electron microscopy (SEM).  Analysis that indicates multiple or branched cracking can be indicative of corrosion assisted failure or improper welding procedure, whereas a single fracture surface is commonly found when purely mechanical issues such as fatigue or overload are the cause. The thickness and location of any scales would be used to provide insight into the progression of a lug fracture relative to its overall exposure time.   "Burnbacks" indicate possible over-temperature exposure, which can be confirmed by looking for exaggerated grain growth, thickness of external scales, internal oxidation and changes in hardness using SEM and metallographic investigations.



5. Chemical analysis, looking for Carbon and Sulphur, provides a basis for understanding the microstructure. Such microstructures would have a direct effect on any weld processes on an observed fracture.

Reporting

Using the results of these investigations, combined with an understanding of conditions in the installation and maintenance of cast-in-place monolithic refractory structures, compared against common practice, CERAM can provide a detailed report highlighting potential and actual failure mechanisms, including the findings, with any assumptions, along with a complete file of the metallurgical and chemical and physical interpretation.