A distillate dewaxing unit at an oil refinery was undergoing hot hydrogen regeneration of the catalyst when an explosion occurred. Catalyst regeneration is a periodically performed procedure, in which the normal liquid hydrocarbon feed is stopped and a hydrogen-rich gas mixture is fed through the catalyst bed for which the normal operating temperature is raised from 700F to 800F. During the catalyst regeneration process the reactor pressure is increased from normal operating levels just below 600 psig to about 640 psig. A pipe failure occurred as a sudden and complete rupture of the 10-inch diameter line at the exit of one of the two reactors. Security video revealed that the release rapidly exapnded and the hot gas mixture ignited shortly after rupture. A shock wave from the resulting view more

A petroleum refinery experienced a catastrophic rupture at one bank of three heat exchangers in a catalytic reformer/naphtha hydrotreater unit because of high temperature hydrogen attack (HTHA). Hydrogen and naphtha at more than 500F were released from the ruptured heat exchanger and ignited, causing an explosion and an intense fire burned for more than three hours.

The rupture fatally injured seven employees working in the immediate vicinity of heat exchanger at the time of the incident. The workers were in the final stages of a start-up activity to put a parallel bank of three heat exchangers back in service following cleaning. Such start-up activities had resulted in frequent leaks and occasional fires in the past and should have been considered as hazardous and nonroutine. view more

Operators in a powdered metals production facility heard a hissing noise near one of the plant furnaces and determined that it was a gas leak in the trench below the furnaces. The trench carried hydrogen, nitrogen, and cooling water runoff pipes as well as a vent pipe for the furnaces.

Maintenance personnel presumed that the leak was nonflammable nitrogen because there had recently been a nitrogen piping leak elsewhere in the plant. Using the plant's overhead crane, they removed some of the heavy trench covers. They determined that the leak was in an area that the crane could not reach, so they brought in a forklift with a chain to remove the trench covers in that area.

Eyewitnesses stated that as the first trench cover was wrenched from its position by the forklift view more