Process Industry Safety Lessons

by Gary Mintchell | Jul 15, 2014 | Automation, Safety

My friend Kenna Amos is a  Chem E, PE, has been a magazine editor and editor-in-chief. He has written columns for me in a couple of tours of duty.

He recently wrote a series on process industry safety. Here is a guest post with one of those reports.

Chemical Safety Board Blames Deficiencies for Tesoro Refinery Deaths

Catastrophe blasted Tesoro Refining and Marketing Company LLC’s (Tesoro’s) refinery in Anacortes, Wash., on April 2, 2010. Seven workers died—and the refinery would be closed for six months. Unfortunately, maintenance, design, operations, regulatory agencies, industrial guidance and company safety culture all had roles in the incident.

The accident occurred in the Catalytic Reformer/Naphtha Hydrotreater unit. In it, two parallel banks of shell-and-tube heat exchangers operate. On the day of the disaster, workers were returning A/B/C bank into service, while leaving D/E/F bank in operation.

At 12:35 a.m., carbon-steel exchanger E, in the middle of its vertical stack, ruptured. Instantly, hydrogen and naphtha at 630-710 degrees Fahrenheit and about 600 pounds per square inch, gauge, burst out and auto-ignited. The resulting explosion’s fireball engulfed the heat exchangers. It and the ensuing fire, which burned for three hours, killed the workers.

The state Division of Occupational Safety and Health (DOSH) concluded the tragedy was completely preventable. So did the U.S. Chemical Safety Board (CSB) in its May 1, 2014, report—“INVESTIGATION REPORT: Catastrophic Rupture of Heat Exchanger (Seven Fatalities) – Tesoro Anacortes Refinery; Anacortes, Washington; April 2, 2010.”

High-temperature hydrogen attack (HTHA) caused the vessel to rupture along high-stress, non-post-weld-heat-treated regions of the inside walls of exchanger E. In HTTA, CSB says, atomic hydrogen diffuses into steel, reacts with carbon and produces methane. Because those molecules are too large to diffuse through the metal, they accumulate and exert pressure against exchanger walls.

That process fissures or blisters the steel. “As more fissures form, they can link, forming microcracks. Microcracks can also link to form larger cracks, which greatly weaken the steel and can lead to rupture of the vessel,” says the CSB report. “This process occurred in the E heat exchanger.”

But it needn’t have. Had Tesoro measured or otherwise technically evaluated the heat exchanger’s actual operating condition, existing refinery procedures would’ve required an HTHA inspection, CSB reports. “[Also] no evaluation was documented to demonstrate effectiveness of the inspection safeguards claimed by the [process hazard analysis] PHA team.” If an evaluation had occurred, investigators would’ve found Tesoro didn’t implement safeguards.

Nor did the refiner pursue safer design. None of the Tesoro PHA teams ever considered applying the principles of inherently safer design, by upgrading the heat exchangers before the incident, CSB declares.

Substandard State, Federal Oversight

Even so, for failing to evaluate/implement inherently safer design—or failing to implement HTHA inspection as a safeguard, state and federal regulators never issued citations to Tesoro, reveals CSB. But regulators couldn’t have, as the board discovered, because they have no process safety management (PSM) requirement to scrutinize inherently safer design or evaluate safeguards’ effectiveness.

No U.S. Environmental Protection Agency (EPA) requirement is puzzling. “Despite its acknowledged authority to do so, to date the EPA has not required industries to implement IST [inherently safer technology] through either the creation of a new rule, or the enforcement of the Clean Air Act [Amendments of 1990] General Duty Clause,” CSB states.

But would an existing state requirement have been effective? Circumstance suggests not. CSB notes for 270 PSM facilities, DOSH employs only four process-safety specialists. Only one has significant refinery experience. Only one is an engineer. And none have metallurgical experience.

The state would’ve found deficient maintenance and design programs—and problematic safety culture. Instead of incorporating design elements to eliminate HTHA risk, Tesoro used the mechanical-integrity program to identify damage mechanisms, CSB says. Also, for years, technical experts evaluated HTHA susceptibility using design parameters. But in concluding no heat-exchanger vulnerability, experts weren’t required to prove safety effectiveness.

The Chemical Safety Board also finds an inadequate American Petroleum Institute (API) standard. “API RP [Recommended Practice] 941 – ‘Steels for Hydrogen Service at Elevated Temperatures and Pressures in Petroleum Refineries and Petrochemical Plants’ is written permissively—and there are no minimum requirements for refiners to take any action to prevent HTHA failure,” CSB says. “We will consider CSB’s recommendations as part of the work already underway to prepare the next editions of refinery safety standards,” API spokesman Carlton Carroll says.

Because of a long history of frequent leaks and occasional fires when putting the six heat exchangers back into service, CSB acknowledges that startup, shutdown, and cleaning activities were a hazardous nonroutine operation.

C. Kenna Amos can be reached at [email protected].