The facility includes a Crude/Vacuum Unit (“CVU”). The CVU stores, handles, treats or otherwise processes a mixture of flammable substances, including methane, ethane, isopentane, propane, butane, isobutene and pentane. The CVU had an 8 inch piping elbow that failed, leading to the release of hot Vacuum Tower bottoms. The piping elbow used in the CVU was constructed of carbon steel, in a service that required chrome alloy construction. The use of carbon steel resulted in material failure leading to the release and fire. An additional factor leading to the release and fire was a thinned wall due to high- temperature sulfidation corrosion. Measurements taken after the fire revealed thickness readings near the failure point as low as 0.07, well below allowable levels. The refinery’s post fire investigation concluded that poor quality practices and procedures were utilized when the elbow was installed in 1990 by the previous owner. Another carbon steel elbow was identified in the same piping circuit following the incident.