A single-stage regulator "failed" while flowing hydrogen gas from a standard 200 cu.ft. gas bottle. The regulator had functioned properly prior to the event through several on-off cycles. During the event, a solenoid valve was opened to allow hydrogen to flow, when a rather loud noise was noted and gas began flowing out of the pressure relief valve on the side of the regulator. It was noted that the low-pressure gauge on the regulator was "pegged" at the high side (>200 psi). The valve on the bottle was shut off, and hydrogen flow was immediately stopped. Hydrogen flowing out of the relief valve did not ignite. With the bottle shut off, the regulator was removed and replaced with another regulator of the same type, and activities continued.

The failed view more

Hydrogen and chlorine concentrations at a certain plant are measured once each shift. On the morning of the explosion, the hydrogen concentration in the chlorine header leaving the cell bank was 0.47 percent. After passing through the chlorine coolers and liquid/gas separators, the hydrogen concentration of the gas streams increased to 2.5-3.2 percent H2, i.e., 63-80 percent of the lower flammability limit.

About 5 hours after the measurements were made, the DC power to the electrolysis cell bank was shut down because of intermittent power supply problems. At that time, a low-order explosion was heard from the chlorine dryer area of the plant. Thirty seconds later, chlorine gas began escaping from the chlorine header pumps, and another explosion occurred in the electrolysis cell 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