Progress: Addressed, Not Adequately
Pressure relief valves are used on some DOT tanks and on stationary pressure vessels. These relief valves are reseatable, and protect against overpressure that may result from overfilling or from pressure increase due to temperature increase when the tank is not rated to accept the higher pressure.
Pressure relief valves will provide protection against overpressure, but will not protect against rupture in a fire. There are trade offs with the use of pressure relief valves, balancing the risk of a tank failure due to overpressure versus the risk of released hydrogen igniting.
Standards exist for pressure relief devices for transportable and stationary tanks. The pressures intended for hydrogen storage are higher than typical current use.
A study should be conducted that evaluates potential for an event that would cause an increase in pressure above the rated pressure, the likelihood that overpressure could result in a tank rupture, the likelihood that a release of hydrogen due to overpressure would ignite and cause further problems, and the likelihood that an inadvertent release of hydrogen would ignite and cause further problems. A determination should be made as to what applications would benefit from use of pressure relief valves, and what applications would be safer without the use of pressure relief valves.