CGH2 trailer roll-over and fire

A tube trailer-tractor transporting compressed hydrogen was travelling on a highway, when the driver lost the control of the vehicle trying to avoid an obstacle on the road. The vehicle collided with the central guardrail, tipped over on the other side and the tubes became loose and spread across the motorway. At least one of the 22 tubes started releasing its contents. The tractor caught fire, and probably because of this, also the leaking hydrogen ignited and the fire propagated. The sources are unclear on the number of the tubes which eventually released their content.
The first responders created a safety distance of 300 m and interrupted the traffic in both directions on the highway and on the parallel roads. They used a thermal imaging camera to determine the locations where the hydrogen was released and concentrated the efforts on cooling the hydrogen tubes. Since closing the valves on the tubes would have been a too great risk, it was decided to let the hydrogen burn and extinguish by controlling the fire. As soon as the flow of hydrogen had stopped, the tubes were inspected. Few tubes that had not yet been emptied, were emptied manually by the experts of the transporting company using a blow-off installation. The tubes and the truck were then recovered by means of a crane.
The road surface had to be repaired, because it had been exposed to temperature up to 2000 degree Celsius and half-meter holes had formed. The highway remained closed one week.

The INITIATING CAUSE was the release of hydrogen from a tube valve broken by the impact on the ground. it is unclear if the initial fire was a conventional fire due to the truck impact or the ignition of the released hydrogen. Certain is that this escalated, because the fire caused the hydrogen release from other tubes, probably due to activation of their TPRD’s.
The reason for the driver to lose control was a reserve wheel on the road, lost by a previous vehicle due to the failure of a welding fixing the wheel.
The loss of control could be attributed to a human error. However, this is also a case of conventional material failure: losing a wheel on a road is the effect of inadequate inspection and maintenance of conventional vehicle components.

CGH2 tube-trailer, 22 hydrogen tubes

The driver died due to vehicle crash. The road surface had to be repaired, because it had been exposed to temperature up to 2000 degree Celsius and half-meter holes had formed. The highway remained closed one week.

A security perimeter was set up by fire fighters / authorities. The road, as well as the parallel roads,
was cut in both ways of traffic. A diversion was organized.
Fire brigades quickly mastered the fire. They also verified the state of gas cylinders. Those not leaking were cooled, those leaking were left burning in a controlled way. The evolution of the fire was followed by a thermography (thermal camera). It was estimated that the fire burned at a temperature superior to 2000°C.
The following morning, several bottles had finished burning, four were still closed and two others remained wedged under the truck. Fire brigades continued to splash the cylinders with water to cool them, before being able to analyse the situation more in detail. One day later, the fire was totally under control by fire brigades, further hazards involving cylinders were excluded, and the operations of clearing were able to begin. Three days later, the crisis unit met and decided to open again a part of the road in the traffic in both ways. The traffic was disrupted during approximately one week because of renovation work.

Although the intervention was eventually successful, there have been several challenges during the emergency and the report presents some lack of details which hinder the assessment of the intervention:
a) The fire brigade could not know the effect of the mechanical impact on the integrity of the tubes. Also, they could not assess the effect of the heat radiation on them.
b) There is scarcity of water supply along the highway. Nevertheless, because of the possibility of tube over- pressurisation due to exposure to fire, it was decided to make intensive use of water.
c) It took hours for the transport company engineers to arrive on site, due to the traffic jam created by the interruption of the traffic,
d) When they arrived, also they could not provide any certainty at that time whether it was safe to recover the tubes.
e) The report stated that “As soon as the flow of hydrogen had stopped, the tubes were inspected”. It is unclear how it was decided that the risk was terminated. Were they hearing the hissing of the leaking hydrogen? If true, how to explain the presence of a fire, and at the same time the release of un-ignited hydrogen?

Based on the lesson learnt during this and similar incidents, the following guidance was issued to Dutch first responders:
In the event of incidents involving hydrogen, the five most important aspects in the first phase of incident response are:
(1) Start the procedure for incident for the hazardous materials (IBGS), because it cannot be known beforehand how large the area of effect is (determine the line of fire and stay upwind).
(2) Do not extinguish a hydrogen fire, but cool (radiated) objects where necessary.
(3) Always cool a radiated hydrogen tank with sufficient water. Prevent water from contacting the Thermal Pressure Relief Device (TPRD, fuse on the blow-off valve). This will cause the TPRD to no longer work, which may result in pressure build-up and an explosion.
(4) Always use an explosion hazard meter and a thermal imaging camera to make the leak and/or fire visible.
(5) Keep sufficient distance from the object where hydrogen is present due to the risk of blowing off and/or escalation.
(a) The distance to be used differs per scenario / installation size.
(b) Measuring equipment cannot be used to determine safe or unsafe areas; keep to standard 25 meters.