Leak from a CGH2 trailer during delivery

This incident occurred when delivering hydrogen to a stationary hydrogen tank at a customer site. After transferring from the first 2 tubes, the driver began to transfer from the 3rd tube. At this point, a fitting failed on the customer tank. A 1/2" tube separated from the fitting causing a leak. The leak lasted about 5 minutes until the pressure dropped and the driver was able to isolate the leak and stop the flow.

The INITIATING CAUSE was the failure of a connection pipe on the stationary storage tank, when transferring.
The connection was a double ferrule fitting. Inspection revealed the back ferrule in the fitting was installed backwards. A new fitting was installed correctly to prevent reoccurrence.
The ROOT CAUSE was then a wrong installation performed by the customer of the hydrogen supplier.

fitting

Trailer's capacity was approximately 355 kg , the transported quantity was however less, approximately 300 kg.
The tubes were of composite materials, nominal pressure was not provided.

The customer was a company producing boilers

The hydrogen quantity accidental released was 42 gas-pound (approximately 20 kg)

The driver waited for the pressure to drop in the tube, after which they were able to isolate the leak.

The event had limited consequences, because the leaking hydrogen did not ignite. Another mitigating element was the fact that the hydrogen transfer was performed by connecting only one individual trailer tube and waiting for its emptying before moving to the next tube, This limited the amount of hydrogen leaking.
Nevertheless, under different conditions, it could have been more severe.
The PHMSA reports as immediate corrective action the replacement of the ferrule with new one properly installed. This simple action allowed to bring to a successful end the delivery of hydrogen to the customer.
Nothing is known, however, on a additional necessary measures aiming at avoiding the re-occurrence of the wrong installation, or at the timely detection of it. Such measures could be, for example, a regular high-pressure test before hydrogen transfer, or the execution of the connection(s) mounting based on the principle of the 4 eyes.