Studies suggest MMS knew blowout preventers had 'critical' flaws
Government regulators have said that the failure of the Deepwater Horizon's blowout preventer April 20 was unforeseeable. But studies conducted for federal regulators in MMS or with their participation show that blowout preventers were known to have 'safety critical' vulnerabilities.
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One type of hydraulic ram valve, called a shear ram, is designed to prevent a situation like the one in the Gulf. In the event of a catastrophic failure, the shear rams are supposed to stop the flow of oil by cutting and crumpling the pipe between them. The Deepwater Horizon’s shear rams failed, though it’s not yet clear why.Skip to next paragraph
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Many BOP gaskets (the Deepwater Horizon’s included) are designed to handle up to 15,000 pounds per square inch (psi) of internal pressure – the pressure of the oil and natural gas pressing outward on the BOP. But they are not mandated to handle external water pressure, which can equal more than 2,000 psi in deep water.
Moreover, stress on seals and gaskets could be exacerbated if the pressure inside the well drops dramatically, meaning pressure is higher outside than inside.
The study noted that neither the MMS nor the American Petroleum Institute (API) had any specific standards dictating how much external pressure the seals and gaskets must be able to withstand.
“The maximum allowable external pressure is never published and indeed may not even be known by the manufacturer,” the report said. “If differential pressure is applied to a component not designed to withstand it, there could be serious consequences for well control; the deeper the water the greater the risk....”
A BOP engineer active in the industry who asked not to be named corroborates the study’s findings: “It was gaskets and seals that were the challenge.”
The study recommended that the industry have an external-pressure test for closure mechanisms. That “would demonstrate a factor of safety in this critical area,” it said.
Some manufacturers have upgraded seals and gaskets voluntarily. “Manufacturers don’t sit around waiting for the MMS to write a spec,” says the BOP expert who requested anonymity. “If they waited for specs from MMS, they would still be waiting.”
But the lack of specific federal standards resulted in a lack of uniformity both in seal quality as well as their maintenance, say Dr. Bea and others.
Minerals Management Service officials said by e-mail that the agency’s safety research division did act on the 2006 report by sharing it with headquarters staff charged with writing regulations, with regional field staff who enforce the regulations, and with industry organizations. Technical papers were presented at conferences with the findings.
But almost four years after the study findings, there are no federal or industry external water pressure standards for BOP closure device seals and gaskets. “We have not updated our regulations related to these findings since the 2006 report,” an MMS official wrote in an e-mail.
No. 2: test ram vulnerability
Test rams are a relatively new innovation in the offshore oil and gas industry and are currently on only a few deep water drill rigs’ BOPs. They are designed to streamline costly and time-consuming hydraulic test procedures required under federal regulations. The Deepwater Horizon was one of the few rigs whose BOP had a test ram. One big problem: The devices don’t help in an emergency – and they may obscure emerging dangers.
That is precisely what happened in one of the “safety critical” failures recorded in the 2009 report. One of the BOPs studied experienced a critical failure when a leak developed at the wellhead connector, compromising its ability to maintain the correct pressure. “On rigs with test rams, the leak, regardless of size, would not have been identified,” the report noted.
The report strongly criticized test rams because they obscured leaks and took up space on a BOP that otherwise could have been used for a real ram.
Critics in Congress said the test ram retrofitted onto the Deepwater Horizon impaired the BOP’s redundancy and, therefore, reliability of the BOP.
The MMS responds that its “drilling engineers have allowed the use of test rams only after a very thorough review.”