The choice of metal for new pipes at the fire-damaged Chevron oil refinery in Richmond could complicate restoration of the plant to full fuel production.

A Chevron representative said Monday that the gasoline-making plant won't repair equipment damaged in the Aug. 6 fire until regulators' safety concerns are resolved about the company's pick of a metal alloy called "9 chromium."

Chevron will not proceed until all the safety issues have been "thoroughly discussed" with regulators, Barbara Smith, a Chevron refinery senior business manager, told the Bay Area's air pollution board Monday at its meeting in San Francisco.

Chevron has touted the "9 chromium alloy" as an upgrade over the carbon steel pipe that broke at least in part due to corrosion when exposed to high sulfur crude.

The smoke from the fire sent 15,000 people to local hospitals with complaints of breathing difficulty, throat irritation and headaches.

Chevron has said it plans to finish refinery repairs in the first quarter of 2013.

The federal Chemical Safety Board has questions about the decisions and wants answers.

In a letter sent Saturday to Richmond officials, the federal safety agency demanded Chevron release documents by Dec. 7 to explain why it picked the chromium alloy over a stainless steel pipe touted by the American Petroleum Institute as resistant to sulfur-induced corrosion.

"The difficulty in predicting corrosion rates underscores the need for choosing the safest materials of construction, since inspections based on predictable corrosion rates may not prove to be reliable," Rafael Moure Eraso, chairman of the federal safety board, wrote.


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He also said Washington state safety investigators believe that a February fire at a BP refinery near Cherry Point was related to corrosion in pipe made of "9 chromium."

"Photographs of the piping failure at BP," Moure Eraso said, "show a striking resemblance to the failure at Chevron."

In the air board meeting in San Francisco, Smith, the Chevron representative, said that refiners selected the chrome alloy as the best all-around material.

While stainless steel is regarded as effective in resisting corrosion related to sulfur, the steel can become brittle at high temperatures, she said.

Chevron is seeking permits from the city of Richmond to fix rather than replace the refiner unit damaged by the fire.

Air pollution board administrators said it's the responsibility of the city of Richmond -- not the air board -- to make the call on the metal to go into the pipes.

The Richmond City Council is scheduled to discuss the Chevron repair plan at the council's meeting at 6:30 p.m. Tuesday at the City Council chamber at Civic Center Plaza and Macdonald Avenue.

Contact Denis Cuff at 925-943-8267. Follow him at Twitter.com/deniscuff.