Explosion in the storage of a HRS

A major leak (estimated between 1.5 and 3 kg) of hydrogen from high-pressure storage, resulted in a detonation, from hydrogen a refuelling station.
Causes were two untightened bolts securing the gasket between the high-pressure tank and the pipeline. Gasket held for over 2 years against 900 bar pressure before eventually giving way due to fatigue induced by pressure oscillations during refuelling.
Specific tank was the one closest to the ground; after breaching the high-pressure gasket, hydrogen quickly broke through the low-pressure gasket and rapidly leaked to atmosphere, forming and explosive cloud.
The untightened bolts were blamed on faulty assembly by manufacturer NEL, who took responsibility. They enacted new procedures, similar to the aviation industry, to ensure such a mistake would not occur again.
Damage to surrounding buildings (65 m away) indicate that a detonation occurred. The HRS was by a busy roundabout at the outskirts of Oslo on a day when Norwegians were driving home from holidays.
Two car drivers were checked in at hospitals after their airbags opened due to the shockwave, but there were no direct damages to people; injuries were light.
Neighbourhood was alarmed by the loudness of the blast, which was heard in a large area; one dog panicked and jumped from a balcony at the fourth floor of a neighbouring building.
NEL shut down immediately all similar plants worldwide pending inspection on bolts. Station operator Uno-X has after 10 months not yet reopened their hydrogen stations, and may have been permanently swayed against the technology.

INITIATING cause for the release were two not properly tightened.
Root cause was Human error during assembly. The two bolts were screwed in place by hand, but not tightened.

Unexpectedly, pressurisation did not cause gasket to fail , which made the system pass inspection. Gasket held against 900 bars for over 2 years before eventually failing to fatigue.

Monitoring system was not programmed to detect leaks by monitoring abnormal pressure loss in high-pressure tank.

bolts, bolts

Event occurred shortly after a refuelling, as the compressor started refilling the high-pressure tank.

DESCRIPTION OF THE FACILITY
The Refuelling station was in the open. Its storage system was confined by fence but no was roof present.

Station likely totalled and unrecoverable. Material damages est. 1 million euros.
Two car drivers whose airbag opened due to shockwave were checked in to hospitals with minor injuries.
Alarm over a large area as the explosion was very loud. One dog panicked and jumped from a balcony at the fourth floor (9 metres), breaking some bones but surviving.
Parts of the fence that absorbed the explosion were projected into the neighbouring roundabout, about 15-20 metres away; no damage to vehicles.
Detonation focused in internal corners of neighbouring (65 m) office building, which has windows broken.

The system passed inspection, but was not safe. The gasket was far more resilient than assumed, and hid a faulty assembly for over 2 years.
High-pressure components need to follow precise procedures for assembly, with double witnesses.

Manufacturer of the storage system enacted strict protocols for assembly with double-witness (as in aviation industry).

A more robust design of the outer perimeter of the refuelling station would shield members of the public from projectiles would presumably be a good start.

The manufacturer shut down immediately all similar plants worldwide pending inspection on bolts.