A hydrogen fire occurred in an early morning accident involving a hydrogen tube trailer and multiple vehicles on a rural highway. The cause of the collision is unknown, however, it appears to be unrelated to hydrogen (i.e., it was likely human driving errors). The hydrogen tubes contained compressed hydrogen gas at a pressure of 15 bar (218 psi). The accident caused a leak in the hydrogen plumbing system and deformed one of the hydrogen tubes, resulting in a 10-centimeter (4-inch) longitudinal crack from which hydrogen began to leak (see Figures 1 and 2). Fire from the conventional vehicles trapped under the hydrogen tube trailer during the accident ignited combustible components on the tube trailer (tires and fuel/oil), and subsequently the leaking hydrogen. Emergency crews arrived and cooled the hydrogen tubes with water to reduce the explosion risk and then put out the fire. No injures occurred related to the hydrogen fire.
- Vehicle & Fueling Systems
- Gaseous Hydrogen Delivery Vehicle
A hydrogen tube pressure indication system needs to be developed that is robust enough to withstand an accident, indicates hydrogen pressure regardless of valve position, and would be visible from a safe distance during an accident situation. Hydrogen system pressure is very important in determining incident response actions. Centralizing the system pressure indicators on a highly visible information panel located in a protected area of the tube trailer is a possible solution to increase visibility. Fragile manometers should be replaced with more robust instruments and associated piping/components that can survive accident situations. Finally, pressure indications in all areas of the hydrogen system are desired, but especially the internal hydrogen tube pressure. System pressure components should be designed so that hydrogen pressure in the tubes is measured even when valves are closed and tubes are isolated.
Increased structural protection is needed at the back of the hydrogen tube trailer to protect the vulnerable hydrogen systems components in this location (e.g., valves, pressure-indicating devices, manifolds, piping) in case of an accident. More robust components (especially the pressure-indicating manometers) and better support/tie-down to the tube trailer of the hydrogen pressure components may be beneficial.
Hydrogen valves should have a visible means to show that they are in the closed position. A highly visible lock or pin that can only be used when the valves are closed may help guarantee valve closure prior to transport. If the valve positions are visible, an operating procedure could be added that requires a final valve line-up check just prior to hydrogen tube trailer departure.
The hydrogen tubes need more fire protection/heat shielding at their location on the tube trailer, especially as related to the key fire load sources (combustible material) at the tire and fuel/oil locations. Local shielding, both at the fire source and at the protected destination, should be considered to provide the best method for reducing flame impingement and thermal loading/impact on the hydrogen tubes and associated components during a fire. Consideration should also be given to hydrogen tubes and components designed for higher pressures and greater fire resistance.