Inspectioneering Journal

Inadequate Inspection Documentation Cited in One of Four Root Causes In 1995 Explosion

"Repair mention does not an inspection make!"

By Greg Alvarado, Chief Editor at Inspectioneering. This article appears in the May/June 1998 issue of Inspectioneering Journal.

The Environmental Protection Agency (EPA) issued the report on this catastrophic failure that involved two storage tanks in a Pennsylvania refinery. The report issued March 20, 1998, stated that while both tanks had roof replacements since their initial construction, no further information was available about routine inspection or maintenance procedures.

The two tanks failed along their bottom seams causing them to shoot up into the air and to release the entire contents of one of the tanks. This led to a fire which spread throughout part of the refinery causing extensive equipment damage. A likely contributing factor to this type of failure, according to the report, was corrosion around the lower portion of the tanks. Corrosion in this critical zone is not uncommon, especially when “chat” or limestone rock has built up around the outside of the tank.

It is important to report the detailed condition of equipment during all inspections. We should never just report that the equipment was repaired without reporting the specifics of the problems and how the tanks were repaired and the quality of the repairs. Explain not only why it was repaired, note the condition of the equipment, otherwise, such as:

In addition to agitator replacement, due to general corrosion, stress-accelerated corrosion was noted in the welds and heat affected zones in the top head, sidewall and bottom head during internal inspection of this vessel.

Top head thickness measurements ranged from xxx to xxx, sidewall from yyy to yyy and bottom head from zzz to zzz. (The inspector could also note whether or not preferential corrosion was noted in the “splash zone” or liquid vapor interface area, etc. depending upon the tank/vessel, design, material of construction, past history and service.)

This is just a general example. It is also possible, and recommended, to show the location pattern for thickness readings, and so forth, either in hardcopy or as a linked digital image to a computerized database. Hopefully, the days of looking at an inspection report and just seeing the note that a repair was made and nothing else is recorded are long gone.

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