Anonymous
A similar incident happened several years back at a Coker in the southern US. The root cause was steam purge leakby into the overhead vapor line. The steam was condensing, and eventually accumulated a sufficient level to “burp” overhead into the piping. A contract worker was working at that location to hydroblast the vapor line, and was scalded when the hot water came out. The facility now opens drain valves on the vapor line to prevent a level from forming. Hope this helps. [;)]