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

Overview: A hydrogen leak and explosion occurred due to the installation of an incorrectly sized gasket at the suction line of a hydrogen compressor in a refinery hydrodesulfurization plant. The incorrectly sized gasket was mounted during the startup of the plant in 2001 and had never being inspected nor replaced.

Incident synopsis: The operating conditions were stable when the operator received an alarm indicating pressure loss in the circuit. He immediately instructed his field personnel to inspect the area. The hydrogen leak was confined inside the compressor room because the walls and roof were not provided with ventilation devices. An explosion occurred, causing two fatalities and the destruction of the compressor room and some of the surrounding area.

A pressure relief device (frangible burst disk) on one of a hydrogen delivery tube trailer's 26 tubes failed prematurely and released hydrogen while filling a hydrogen storage tank at a government facility (see Attachment 1). Prior to the filling process, all procedures and safety checks, including connection to the facility's regulator/distribution control system with leak checking and follow-up verification of leak checking by facility personnel, were completed (see Attachment 2 for more details). During the filling process, a person walking near the facility heard the noise of escaping gas that included occasional popping sounds typical of bursts of gas release. Facility personnel were alerted and the tube trailer vendor's incident response team was dispatched to the view more

A metal hydride storage system was refilled using compressed hydrogen in a closed lab environment. The tank system is an in-house development and is optimized for high hydrogen storage density and use with an air-cooled fuel cell. The system is equipped with a pressure relief valve that opens gradually at 35 bar to protect the tank from overpressure conditions. The tank itself is designed to adsorb 400 g of hydrogen at a pressure less than 15 bar.

For refueling, the secondary pressure on the compressed hydrogen supply container was set to 20 bar and the adsorption of the hydride was started without hydrogen flow limitation. Due to the exothermic nature of the hydride upon recharge, as expected a sharp increase in tank temperature was measured. The tank was uncooled because the 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 System Shutdown logic activated and the compressor automatically shut down on high vibration. When the operator investigated the unplanned shutdown, two broken compressor head fasteners were noted lying on the deck.

A sidewall burst failure of a high-pressure polytetrafluoroethylene-lined hose was experienced. The 4.0-m hose was in service for approximately two years, primarily for 70 MPa fueling of hydrogen at ambient conditions ranging from -40 C to +50 C. The total number of fills during its service life was estimated to be 150. In addition to the high-volume fill events, pressure cycling occurred as part of the routine test procedures and operational protocols. These additional pressure-cycling occurrences were approximated to be 200-250 cycles. During each filling cycle, the hose was allowed to bend during connections, as required by the situation. Failure of the hose occurred while temporarily connected to a gas booster, after 1-2 hours of service at 75 MPa. There were no tight bends in the view more

A single-stage diaphragm compressor failed during boosting of high-pressure hydrogen ground storage banks. The compressor sources hydrogen from a 44 MPa storage bank as suction and discharges it at a stop set point of 85 MPa. The compressor capacity is 0.71 m3/min (25 scfm).

The original notice of failure was through an inter-diaphragm pressure indication and alarm. There should not be any pressure build-up between the layers of the diaphragm. Upon opening, hydraulic oil was found, leading to the assumption that the hydraulic-side diaphragm was leaking. Although spare diaphragms and seals were available for on-site repair, difficulty was encountered in attempting to remove the compressor nut above the diaphragms. Similar difficulties were encountered when the unit was returned view more

The subject needle valve was used primarily for manual filling to control the flow rate of hydrogen from storage banks to the 70MPa test system. The valve was installed on the exterior of the thermal chamber in ambient temperatures of -5C to +30C. The gas flowing through the valve was at conditioned temperatures of -40C to +50C. The valve was in service for approximately two years and 400 fill operations.

Failure occurred during a test under an open valve condition. When attempting to close the valve, the turning force increased and the technician was unable to completely close the valve. An upstream ball valve was closed to isolate the flow.

An explosion at a coal-fired power plant killed one person and injured 10 others. The blast killed the delivery truck driver who was unloading compressed hydrogen gas, which is used to cool the plant's steam generators. Hydrogen deliveries are routine at the plant, occurring about once a week. Evidence pointed to the premature failure of a pressure-relief device (PRD) rupture disk, which had been repaired by the vendor six months prior to the explosion.