Hydrogen leaked from a 9,000-gallon horizontal liquid hydrogen tank in the rear of a high-intensity lamp manufacturing facility. The facility manager noticed the leak during his normal morning rounds and initiated the plant's emergency response policy, which included calling the local fire department. A large vapor plume (actually condensed moisture in the air) was visible 200 feet above the tank. The technician for the hydrogen supplier arrived on site, thawed out the ice buildup around the gland nut from which the leak originated using warm water, and tightened the nut, thus ending the problem. The technician verified that the leak originated from packing material around the valve that had come loose because of the recent extreme cold weather.
The fire department requested that the facility not shut down, but rather continue operations to draw normal levels of hydrogen from the tank. A checkpoint was established near the tank side of the building where hydrogen level readings were taken and reported every 5 minutes. Employees of the plant were notified to exit the front of the building in the event of an evacuation signal. As hoses were turned on by the fire department, a drop in water pressure tripped the internal alarm, causing an evacuation of the plant. All employees were accounted for and were asked to return to work, as this was a false alarm condition. Two local streets were closed, radios, cell phones, and other electronic devices were shut down within a 500-foot safety zone to eliminate any static electricity that could ignite the hydrogen gas, and airplanes were diverted from their normal flight path to the local airport. Firefighters set up combustible gas monitors inside the building, but no gas was detected. The incident lasted approximately two hours.
Excessive venting of hydrogen from the tank due to lower facility consumption, in combination with extreme temperature conditions, placed thermal stress on the gland nut, causing a leak. The low consumption of hydrogen resulted from the shutdown of some production equipment and the delay of additional production equipment coming online. The tank size is too large for the facility's current hydrogen demand.
The hydrogen supplier will conduct annual training on handling all types of gases used by the facility and will include the local fire department in this training. The facility will continue daily rounds to look for visual evidence of leaks, and the hydrogen supplier will exchange the 9,000-gallon tank for a smaller 4,500-gallon tank to significantly reduce pressure build up from lower usage.