An oil field tanker truck trailer transferring crude oil from various tank batteries to a pumping station, was having a stainless steel pressure relief valve replaced when the tanker contents violently detonated. One fragment, weighing 69 pounds was found 3,500 feet from the explosion site.
Photograph A View of similar size tanker trailer to one involved in subject accident.
Photograph B View of some of the exploded tanker trailer debris.
Photograph C Circular scans resulting from hydrogen blisters and delamination of tank hemispherical end caps.
The circular shaped scabs shown in Photograph C were the result of long-term hydrogen blistering and the formation of hydrogen bubbles on the interior of the tanker steel shell. Hydrogen gas concentrated along laminar nonmetallic inclusions in the tank wall steel. This resulted in large areas of hydrogen blistering and delamination.
Photograph D Closeup View of ruptured hydrogen blister.
Evidence and documents reviewed during this investigation indicated that hydrogen sulfide exposure of this, and possibly other tanker trailers had occurred over a long period of time. The hydrogen from the hydrogen sulfide had diffused through the tanker steel end caps and agglomerated along non-metallic inclusions near the hemispherical tank ends. As time passed, these hydrogen traps provided a location for hydrogen gas and/or methane gas to agglomerate and form gas bubbles. The failure was determined to be the result of long-term exposure to crude oil containing low concentrations of hydrogen sulfide.