EMERYVILLE -- The use of an incorrect valve caused a May 4 Emeryville fire that caused neighborhood evacuations and closed AC Transit's $10 million new hydrogen fueling station for buses, federal investigators have concluded.
In an apparent slip up, a pressure relief valve at the hydrogen fuel plant was made with a type of hard steel known to crack and fail when exposed to hydrogen, Sandia National Laboratories investigators said in a 33-page report released this week.
"Proper material selection would have prevented this incident," Sandia experts said in the report to be discussed Wednesday night by the AC Transit board. "The valve manufacturer already offers the same valve component using an appropriate material, therefore the correct selection (was) available."
It's unclear why the wrong valve was installed, officials said, but the result was dramatic.
Eight months after the plant opened as a model to boost hydrogen fuel cell buses, the valve failed, leaking hydrogen into the air that caught fire, boomed, and then burned for two hours.
No one was injured, but the fire rattled neighbors, spurred street closures and evacuation of two schools and several businesses, including Pixar Studios.
Meanwhile, AC Transit has temporarily suspended use of its 12 hydrogen cell fuel buses because it has no place to refuel them.
AC Transit spokesman Clarence Johnson said Tuesday the transit agency still hasn't sorted out
AC Transit hopes to reopen the fuel station n September after making a series of recommended equipment and procedure changes, including replacing the valve that caused the fire.
"We're not going to reopen the plant until we're sure we have measures in place to prevent a recurrence," he said.
Johnson said the firm that designed and engineering the hydrogen fuel plant -- Linde North America -- will pay for the repairs and changes in accordance with its agreement with AC Transit. There is no cost estimate yet for fire damage and repairs.
In their report, Sandia safety experts said the intensity and duration of the fire could have been reduced if AC Transit and Linde employees had followed procedures to promptly communicate fire and plant operation information to Emeryville Fire Department.
"Both AC Transit and Linde communicated well internally, but failed to communicate with each other or the incident command (Emeryville Fire Department)," concluded the report by Sandia.
The safety investigators also said the fire lasted longer than necessary because the plant was not designed well to isolate the flow of hydrogen.
The fuel cells combine hydrogen with oxygen in the air to make electricity to run the buses without pollution.
Contact Denis Cuff at 925-943-8267. Follow him at Twitter.com/deniscuff
The AC Transit Board will meet 5 p.m. Wednesday at 1600 Franklin St., Oakland to discuss a report on a May 4 fire at its hydrogen fuel station in Emeryville.
The report can be inspected online by visiting www.actransit.org/ and clicking on board of directors and then meetings.