Hose rupture during hydrogen transfer

The incident occurred while transferring gaseous hydrogen from a tube trailer to a customer stationary supply system. The transfer hose ruptured and released hydrogen which ignited explosively. The resulting fire was allowed to “burn off” the hydrogen remaining in the trailer.
The involved hose was part of system used to maintain a continuous supply to the customer. This is achieved by having one trailer kept connected as a supply source, while refilling the second trailer. By every new delivery of hydrogen, the newly refilled trailer is then connected to the customer system, before the trailer in service is isolated and disconnected.

In this incident, the refilled trailer had just been connected to the customer pressure reducing station and the second trailer was in the process of being disconnected for return and refilling. While disconnecting the in-service trailer, the driver heard an unusual sound from the direction of the full trailer which had just been connected. Before he was able to investigate the source of the sound, there was an explosive ignition followed by a fire. This sequence of an explosion followed by a fire was confirmed by onsite surveillance cameras.

The location of the release was the hose. There was no breach of any of the cylinders comprising the tube trailer, nor did the burst discs on any of the manifold tubes activated during the following fire. The hose was not equipped with excess flow devices, therefore the fire continued being fed by the hydrogen in the trailer, and the non-metallic components of the hose were burned. Since the whole hose was destroyed, a root cause for the incident could not be determined.

The INITIATING CAUSE was the rupture of the flexible hose.
The ROOT CAUSE is unknown, the hose was destroyed during fire, and was impossible to determine the cause.

Hose

the refilled trailer had just been connected to the customer pressure reducing station .

The tradional steel tubes trailers of the company could achieve a max capacity of 350 kg of hydrogen. Their nominal pressure ranged between 180 an d200 bar.

PHMSA report does not mention any injury. The online news speaks of 1 trailer operator with 2-degress burns and one Burger King customer with ear pain.
The total costs consisted of:
Material Loss: $ 1,000.00
Carrier Damage: $ 120,000.00
Property Damage: $ 150,000.00
Response Cost: $ 30,000.00
Remediation/Cleanup Cost: $ 10,000.00

An excess flow valve could be a possible measure to prevent large quantities of hydrogen to be lost when a leak occurs on a hose during hydrogen transfer. However, such a measure requires a careful design (the value of limit flow, the valve location, etc.), a complete review of the worst failure scenarios and of the related risk assessment, to avoid introducing additional hazards (for example when a quick venting is required to reduce over-pressurisation of the storage tank).