Watching Government: BSEE’s focus on bolts
Blowout preventers (BOP) were an initial offshore equipment focus following the 2010 Macondo deepwater oil well blowout. Lately, however, the US Bureau of Safety and Environmental Enforcement has paid growing attention to bolts.
BSEE Director Brian A. Salerno observed in a July 20 column at the agency’s web site that on Jan. 4, 2010, a few months before the event that destroyed the Deepwater Horizon semisubmersible rig, the crew aboard another semi, the Ocean Confidence, was testing a BOP when all 20 of the 16-in. long, 3-in. diameter bolts at the connection between the upper and middle double rams suddenly failed approaching 14,000 psi.
“Luckily, this was a shipboard test, not a situation where the BOP was needed to prevent a catastrophe,” Salerno said. But less than 3 years later, bolt failures made the Discover India’s lower marine riser package separate from the BOP stack, spilling more than 400 bbl of synthetic drilling fluids, he said. Investigators found that hydrogen-induced stress corrosion cracking from embrittlement was the cause.
“Bolts are among engineering’s most simple creations, but they hold together most of the subsea infrastructure used in oil and gas exploration,” Salerno noted. “I’m not sure anyone has counted all individual bolts involved in an offshore operation from drilling through production, but the number is in the thousands. We have a responsibility to make sure that every one of these bolts can handle the stresses they are designed to withstand.”
While there have been no major bolt-related accidents so far, BSEE became so alarmed at the prospect that it issued a nationwide safety alert in February.
Among important steps since, Salerno said the new offshore well control rule includes bolts among required safety-critical equipment reporting. BSEE also is working with international regulators to identify global bolt failure incidents and causes, and has assembled a work group with the American Petroleum Institute, he said. The agency’s Safe OCS near-miss reporting system also allows it to receive data directly from contractors and offshore workers.
“The bolt problem has probably been around for quite a while-in fact, we know of an incident dating back to 2003,” Salerno said. “That we have not had a major incident so far may be due to luck more than anything else. How long that luck will last is not a question I think any of us is comfortable answering.”