US safety agency orders partial shut down of LNG facility after leak discovered

Federal regulators have posted a corrective action order following cracks in two of the five storage tanks of Cheniere Energy’s Sabine Pass LNG Terminal in Cameron Parish, Louisiana. Such orders are only issued when there is a danger of ‘serious harm to life, property, and the environment’.

The Pipeline and Hazardous Materials Safety Administration’s (PHMSA) order comes after Cheniere employees found a pool of LNG by one of the company’s storage tanks on 22 January. After a PHMSA investigation a second series of leaks was discovered in a second tank.

The leaks were caused by a fault that allowed the LNG to escape from the inner to the outer tank, exposing it to temperatures far lower than its designed -31 degrees Celsius limit (liquid natural gas is cooled to about -160 degrees Celsius). The leaks were cause by ‘brittle failures’ which do not show warning signs before failing.

All five of the tanks at the Sabine Pass Facility were designed by Mitsubishi Heavy Industries, with three of the five (including both the affected tanks) being fabricated by Matrix Service. The tanks entered operation in 2008. The facility has two other tanks that were made by Zachry Industrial and two berths for LNG transport. The company has been allowed to continue to operate these facilities.

In their initial response to the leak, the company isolated and de-inventoried the tank save for an amount of LNG ranging from one to two feet to maintain the temperature required for the inner nickel steel tank. The order requires that the tanks be completely emptied.

After PHMSA started its investigation, Cheniere Energy supplied them with a report the commissioned from Matrix Service that outlined eleven past incidents from 2008 to 2016 resulting from a ‘geyser-type effect’ that manifests under certain flow conditions and can cause fluid to spill from the inner to the outer tanks.

Talking about these ‘certain flow conditions’, Cheniere spokesman Eben Burnham-Snyder told EENews that "While our event investigation continues, and a root cause analysis has not yet been completed, Cheniere's initial belief is that during freezing weather the bottom fill valve failed to remain closed, resulting in [LNG] flow through the bottom fill line."

Alan Mayberry, the Associate Administrator for Pipeline Safety at PHMSA said in the order that “[t]o date, Sabine has been unable to correct the long-standing safety concerns described”. He also noted that the company has not been able to identify the exact source of the leaks or the amount of LNG that the outer tanks have been exposed to.

The agency mandates a number of actions in the order, including that the company:

• Removes the affected tanks from service within seven days.
• File a work plan with PHMSA to purge the tank, identify the root cause of the issue and outline methods of repair, modification and monitoring. The work plan must also be evaluated and approve by an independent third party.
• Reviews the operation of other tanks.
• Provide the agency with all information about prior incidents at the facility where LNG has spilled or vapours escaped.

The two tanks cannot return to operation without the approval of the director of PHMSA. The Federal Energy Commission reiterated this requirement in a letter to the company.