Narrator: The Chevron Richmond Refinery
lies approximately ten miles northeast of San Francisco in
California's Contra Costa County. The 2,900-acre facility was
initially established in 1902 and primarily makes transportation fuels
such as gasoline and diesel as well as lube oils. The refinery can process up to
250,000 barrels of crude oil per day. The first step of the refining process
takes place in the crude unit where crude oil is cleaned and heated
before entering the distillation tower. Inside the tower
the crude oil is boiled. The vapor then condenses into various
liquid hydrocarbon fractions or streams including jet fuel,
diesel and gas oil. The different streams exit the
distillation tower through separate pipes or sidecuts that lead to other
sections of the refinery. On August 6, 2012, the crude
unit was operating normally. Around 3:50 that afternoon an
operator was performing a routine check when he noticed a small puddle on the ground
near the distillation tower. The liquid appeared to be dripping from
an 8-inch insulated pipe 14 feet overhead. The leaking pipe was a section of
the tower's Number 4 sidecut line which operated at a temperature of
640 degrees Fahrenheit and contained light gas oil, a combustible liquid
similar to diesel fuel. Chevron inspectors knew that over the years the walls
of the Number 4 sidecut had thinned due to corrosion. But they did not realize how close
this particular segment was to failure. There was no shut-off valve between the pipe and
the distillation tower and no way to isolate the leak. The head operator was
called to the scene. Although he believed the situation was serious,
he did not believe the small leak warranted immediately shutting down the
unit and stopping production. Following Chevron's standard practice
for responding to hazardous leaks, refinery firefighters
were sent to the scene. A number of managers, engineers and technicians
gathered there informally to assess the problem. The group discussed a recommendation
from an operator to shut down the unit, but they decided to first try to pinpoint the leak
by removing insulation from the pipe while the crude unit
was still running. They hoped they could stop the leak
with a temporary metal fitting known as a clamp. A Chevron firefighter tried using a pike pole
to hook and pull away the insulation. But this poking action was deemed too dangerous
because it was moving the pipe. The CSB later found that the tip of the pike likely
caused a small puncture in the already thinned pipe. As the unit continued to operate, workers
assembled scaffolding directly beneath the leaking pipe. Two firefighters then used a hook
to remove the insulation from the pipe. As they were working, hydrocarbon vapor
began to flow out from underneath the insulation. The two firefighters backed
away from the growing vapor cloud. As the hot vapor
mixed with air, it ignited. That fire was quickly put out, and the two firefighters
immediately climbed down off the scaffolding. But the exact location of the leak was still obscured
by the remaining insulation and firefighting water. So the Chevron firefighters attempted to strip the
insulation off the pipe with high pressure water. But the leak suddenly worsened, and hot
hydrocarbon liquid started to spray out of the pipe. A decision was finally made to begin an emergency
shutdown of the crude unit, but it was too late. Suddenly the pipe ripped open. A vapor cloud formed and rapidly expanded as the
large inventory of hydrocarbons in the distillation tower started to vent
through the ruptured pipe. The vapor cloud immediately spread over hundreds of
feet, engulfing all 19 people who had gathered nearby. The firefighters and operators struggled to escape
through the dense hydrocarbon cloud. Unable to see, they had to feel their way out,
some on their hands and knees. At approximately 6:30 p.m., two minutes after the
huge vapor cloud formed, the hydrocarbons ignited. One firefighter was trapped inside a fire engine
when it was suddenly engulfed in flames. He radioed for help. Firefighter: Mayday, Mayday, Mayday,
this is 460. Narrator: But when he received no response,
he assumed everyone else was dead. To escape the inferno, he fled through
what witnesses described as a wall of fire. Fortunately all the workers would eventually
flee to safety, and there were no fatalities. The towering white vapor cloud could be seen as far away
as San Francisco on the unusually clear August day. After the ignition, a dense plume of black smoke formed
and drifted away from the refinery. The fire continued
burning for hours. Over the succeeding days, more than
15,000 people sought medical treatment at nearby hospitals for
breathing problems and other symptoms. During its investigation, the CSB determined
that the carbon steel pipe installed in 1976 had thinned to the point of failure
from an effect known as sulfidation corrosion. Carbon steel piping is particularly
susceptible to this type of corrosion which occurs over time when the steel is exposed to
sulfur-containing hydrocarbons at high temperatures. Steel piping that happens to be low in the
element silicon corrodes especially quickly. The CSB learned that sulfidation corrosion
had caused a major failure at Chevron's refinery in
Salt Lake City, Utah, in 2002. Chevron then performed an enhanced inspection of
the Number 4 sidecut pipe at the Richmond refinery. It revealed accelerated thinning in the
piping section that would ultimately fail in 2012. Replacement was recommended, but this did not occur
and the section of piping was never inspected again. In 2009 Chevron experts recommended that every segment of high risk carbon
steel piping be inspected for corrosion. However this was not done. During a maintenance turnaround
of the crude unit in 2011, Chevron inspectors examined some but not all locations
along the Number 4 sidecut and found significant thinning. Some sections were replaced, but managers decided
that the line was thick enough to stay in service and that an overall replacement
could wait up to five more years. According to CSB investigators, a key lesson is that each and every segment
of the piping should have been inspected. Most importantly the pipe should
have been replaced much earlier with an inherently safer
corrosion-resistant alloy. The CSB also concluded that had the crude unit
been shut down when the leak was first noticed, the massive fire likely
would not have occurred. The 19 workers would never have been endangered,
and the community would have been protected. For more information on the
CSB Chevron investigation, please visit csb.gov.
