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
A pressure relief device (PRD) valve failed on a high-pressure storage tube at a hydrogen fueling station, causing the release of approximately 300 kilograms of hydrogen gas. The gas ignited at the exit of the vent pipe and burned for 2-1/2 hours until technicians were permitted by the local fire department to enter the station and stop the flow of gas. During this incident the fire department evacuated nearby businesses and an elementary school, closed adjacent streets, and ordered a high school to shelter in place.
There were no injuries and very little property damage. The corrugated roof on an adjacent canopy over a fueling dispenser was slightly singed by the escaping hydrogen flame, causing less than $300 in damage.
The station's operating systems worked as view more
An over-pressurization of two 55-gallon drums of waste phosphoric acid resulted in a material failure of the drum bottoms, releasing the contents of both drums (about 100 gallons) onto the facility floor. The spillage was collected within the sumps that are part of the facility's spill control system. The waste material had been packaged into DOT-specified containers earlier that day and the drums were placed into an assigned storage cell. That evening a staff member heard a noise in the high bay where hazardous wastes are stored. Upon investigating, he discovered the breached drums and spilled material.
The only material released to the environment was hydrogen gas. The maximum concentration of hydrogen released into the facility was 0.035%, well below the lower view more
Hydrogen was released near the ground when the vent line from a 13,000-gallon liquid hydrogen storage vessel suffered damage from unusually high winds. The toppled vent line did not shear or tear, but sustained a kink that restricted hydrogen flow and created a back pressure on the vessel relief system.
Repair efforts were hampered by the potential for cold hydrogen gas, a flammability hazard, in the work area. Shut off or redirection of the hydrogen was not possible, and variable breezes made set up of safe zones uncertain. A protocol had not been prepared for this scenario.
An operation to increase the pressure within a hydrogen tube-trailer to 6000 psig was in progress when a burst disk failed at approximately 5200 psig and hydrogen was released. A vent line attached to the burst disk was not sufficiently anchored and bent outward violently from the thrust of the release over an approximate 4-inch moment arm, causing considerable damage to the adjacent vent system components. The operation is conducted with personnel present, but fortunately no one was in proximity when the burst disk failed.
Following the incident, the damaged portion of the tube bank, consisting of 6 tubes, was isolated by valves on the system manifold. The operation was resumed with the unaffected portion of the tube bank, possessing another 18 tubes, until a second burst disk view more
A safety research laboratory experienced two similar air-actuated ball valve failures in a 6-month period while performing hydrogen release experiments. The hydrogen release system contains a number of air-actuated ball valves which are sequenced by a Programmable Logic Controller (PLC) in order to obtain the desired release parameters. During an experimental release sequence, a PLC valve command failed to open the valve even though the PLC valve position confirm signal indicated the valve had opened. On further investigation, the valve actuator and valve stem were found to be moving correctly, but the valve was not opening. The system was depressurized and purged with nitrogen, and the valve was removed for inspection. Inspection required dismantling the valve, and in both incidents a view more
The sensing diaphragm of a pressure transducer (PT), as supplied on an outdoor hydrogen compressor, unexpectedly ruptured and released approximately 0.1 kilograms hydrogen to atmosphere from the compressor discharge line. At time of incident, personnel nearby were alerted by a loud 'pop' and dust disturbance. Simultaneously, the facility monitoring system detected loss of the PT signal and initiated equipment shutdown. Facility personnel then closed isolation hand valves to stop the leak, locked and tagged out the equipment, and restricted the area. The failed component, a cigar type PT rated to 20,000 psi, originally supplied and installed by the manufacturer as part of the compressor package, was removed and inspected. Inspection revealed severed wires, a separated wire housing, view more
The sensing diaphragm of a pressure transducer (PT), as supplied on an outdoor hydrogen compressor, unexpectedly ruptured and released approximately 0.1 kilograms hydrogen to atmosphere from the compressor discharge line. At time of incident, personnel nearby were alerted by a loud 'pop' and dust disturbance. Simultaneously, the facility monitoring system detected loss of the PT signal and initiated equipment shutdown. Facility personnel then closed isolation hand valves to stop the leak, locked and tagged out the equipment, and restricted the area. The failed component, a cigar type PT rated to 20,000 psi, originally supplied and installed by the manufacturer as part of the compressor package, was removed and inspected. Inspection revealed severed wires, a view more