Synthetic Crystal Autoclave Failure

A manufacturing facility was used to grow synthetic crystals for use in the electronics industry. Synthetic crystals were grown in autoclaves that were 50’ tall and operated for extended periods of time at 700°F and 29,000 psi internal pressure.  Due to these extreme operating conditions, the wall thickness of these autoclaves was more than 8”.

The manufacturing facility experienced a catastrophic rupture of one of the autoclaves while in operation. The resulting explosion decimated the building and propelled debris into the surrounding area. This debris included a 4 ½ ton fragment of the autoclave itself which traveled more than 400’ before penetrating the wall of an adjacent building. Another fragment traveled a quarter mile, struck and killed a person.  

Examination of the autoclave fracture that initiated the catastrophic failure indicated that there was a crack in the autoclave which progressed over time to the point of final failure. In addition to causation, a critical question in the investigation was the length of time the cracking was present in the vessel. ESi initiated a comprehensive investigation, examining the material, its processing, the environment within the vessel and the stresses in the material during service. It was determined that the cracking initiated from Stress Corrosion Cracking (SCC) and propagated over many service cycles to the point of final, ductile overload.