Note: This article has been amended after the bus company retracted its original statement. The headline had been “EXCLUSIVE | Hydrogen cylinders that 'exploded' on California bus were same make that leaked in Netherlands”

Hydrogen cylinders that may have exploded on a fuel-cell bus in California on 18 July were made by the same company that saw its equipment leak H2 in the Netherlands in June, causing Danish green H2 producer and distributor Everfuel to halt its deliveries, Hydrogen Insight can reveal.

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Everfuel found a leak in one of its hydrogen transport trailers — made up of Type 4 compressed hydrogen cylinders and connecting pipes supplied by Norwegian company Hexagon Purus ­— in Rotterdam on 10 June, which prompted the distributor to halt all deliveries as a precaution.

That leak was found to have been caused by a burst O-ring on a valve in the trailer’s distribution system — the pipes connecting the hydrogen cylinders. The bolts on the valve had been improperly tightened during assembly.

“The assembly error was not detected in the quality inspection by the valve supplier or inbound quality check by the trailer supplier [ie, Hexagon Purus],” said Everfuel.

After repairing this fault, the Danish company subsequently found a second malfunction on the same valve across eight of its 12 H2 transport trailers, prompting the company to continue withholding new hydrogen supplies to eight of its nine filling stations.

Everfuel has told Hydrogen Insight that it still has not found a root cause for the second malfunction.

Hydrogen Insight has learned that Hexagon Purus’ H2 cylinders were also on board the Golden Empire Transit (GET) bus — built by Canadian manufacturer New Flyer — that was destroyed by a fire in Bakersfield, California, last week.

However, the valves on the bus’ cylinders were not the same as those used in the Everfuel system.

“In the Netherlands incident, the root cause to the incident was not the cylinder, but a valve related to the cylinder system. These types of valves are not present in an onboard [bus] hydrogen storage cylinder,” a Hexagon Purus spokeswoman told Hydrogen Insight on Thursday(27 July).

GET explained in a press release on 18 July: “Explosions were heard and seen from the tanks [ie, cylinders] on the bus that had just been filled,” adding that the bus was being refuelled at the time of the fire.

But that press release was retracted on 28 July.

“We (Golden Empire Transit) retract our earlier public statement regarding “hydrogen tanks exploding” as this is merely speculation,” the company told Hydrogen Insight on 28 July. “Explosion-like sounds were heard, but until the investigation is complete the source of the explosion-like sounds cannot be confirmed.”

When asked why the initial statement had been issued if the information contained was incorrect, a GET spokeswoman replied: “Explosion- like sounds were seen and heard and it was speculated that it was the tanks. We will not have any concrete answers until the investigation is complete.”

A spokesman for Hexagon Purus told Hydrogen Insight on 24 July: “On July 19, at (between 1am and 2am PCT) a fire at a hydrogen refueling station in the city of Bakersfield in California was reported where a New Flyer bus operated by Golden Empire Transit District (GET bus) was refueling. Currently the cause of the fire is unknown.”

“Our hydrogen cylinders are onboard the bus. We are working closely with the operator, the bus manufacturer, and the appropriate authorities to investigate this event, and we will support the investigation with relevant resources. The investigation is still ongoing, and it is too early to speculate on the root cause of the fire.”

GET initially stated that the Bakersfield Fire Department (BFD) were investigating the fire, but the BFD says it is not doing so because it does not believe there was any malicious intent. It nevertheless asked GET for video footage of the fire to help firefighters to contain such incidents in the future, but the bus operator has declined to do so.

A GET spokeswoman tells Hydrogen Insight: “Since Bakersfield Fire was not conducting an investigation, there was no need to turn it over.”

GET had told local newspaper The Bakersfield Californian that “multiple agencies” were involved in an investigation, but declined to identify any of them.

But the GET spokeswoman later told Hydrogen Insight: “Golden Empire Transit has retained legal counsel that will coordinate the investigation. I do not have any further information at this time.”

Hexagon Purus has been supplying lightweight high-pressure Type 4 hydrogen tanks to New Flyer's Xcelsior CHARGE FC buses since early 2021 — a deal that was extended in March 2022 and again in February this year.

It was one of New Flyer’s Xcelsior CHARGE FC buses that was burned to a charred shell in Bakersfield last week.

A spokesperson for New Flyer told Hydrogen Insight that the fire was “the first event of this kind on a New Flyer hydrogen fuel-cell electric vehicle, which has not had any recalls”.

The Winnipeg-based manufacturer says it has been delivering hydrogen fuel-cell buses since 1994, with about 135 currently on the road.

Hydrogen Insight has asked New Flyer if it is taking any precautions with the rest of its hydrogen bus fleet, a spokeswoman replied: “It will likely be months until investigations are complete, and we cannot speculate on the cause of the incident while the investigation is underway. Thus far, New Flyer has not heard or found any information that causes us to believe that other fuel cell-electric vehicles manufactured by the company pose a safety risk.”

GET has reportedly withdrawn all its hydrogen buses from service until further notice.

Coincidentally, a hydrogen leak was also discovered at a Shell H2 filling station for buses on Friday afternoon in Groningen, the Netherlands.

According to hydrogen equipment marketplace Hyfindr, Type 4 hydrogen tanks “have a non-metallic inner liner made of composite materials and are encased in an outer wrapping made up of carbon fibre and other interwoven thermoplastic polymers”, and can store H2 at a pressure of 700 bar.

This article was amended on 26 July to remove an earlier reference that the bus fire began after the cylinders exploded. This has not definitively been determined.

It was further amended on 27 July to include the statement from Hexagon Purus that the faulty valves on its cylinders in the Dutch incident were not the same as those on its cylinders in the Bakersfield fire, and to add: that GET has removed its original press release from its website; that the BFD is not investigating the fire; the comments from GET that “multiple agencies” were investigating the fire, without naming any of them.

This article was further amended on 28 July to include the news that GET had retracted its initial press release.

It was amended again on 31 July to include new comments from GET about the investigation, and new comments from New Flyer answering our question about precautions with the rest of its fleet.

And it was further amended on 1 August to reflect that the malfunctioning valves were on Hexagon Purus' distribution system, rather than its cylinders.