In July 2016, a coal silo collapsed at an Indiana power plant. The root cause was identified as cracking of the cone-to-skirt weld. Warnings to inspect this vulnerable weld were published widely in conference proceedings and trade journal articles. Nevertheless, coal silos continue to fail at an alarming rate (Figure 1), which suggests that the needed inspections weren’t completed by all power producers.

1. Recent failures of cone-to-skirt welds on large coal silos point to the need for ongoing inspections. Courtesy: Joe W. Frey Engineering Associates, LLC

If you have any of these suspended cone silos (Figure 2) in your plant and are not yet doing non-destructive evaluation (NDE) inspections of their cone-to-skirt welds, then you need to start today.

2. Coal silos like this need our immediate attention! Courtesy: Joe W. Frey Engineering Associates, LLC

Granted, this particular design is a real challenge to inspect, because the silo’s liner seals over the galvanic cell (in layman’s terms, a corrosion sandwich) that is created at the union of the stainless-steel liner and the carbon-steel structure.…

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