The U.S. Department of Transportation has ordered Cheniere Energy’s Sabine Pas LNG terminal to take two storage tanks offline after learning that chilled gas cracked and ruptured an outer tank wall. Cheniere will be able to continue producing and exporting LNG using the remaining three tanks while it takes corrective action.
In an order dated February 8, PHMSA said that workers discovered the leak at Tank S-103 on January 22. The cryogenic gas escaped past the inner wall and chilled and cracked the carbon steel outer wall, leading to “pooling of LNG in the secondary containment area surrounding the tank.” The leakage and cooling caused “four separately-identifiable cracks” of one to six feet in separate areas of the outer steel wall. No injuries were reported and the leak did not lead to a fire or explosion.
PHMSA said that Tank S-101 also experienced a release of LNG into the space between the inner and outer walls, leading to 14 leaks of natural gas vapors along its base. The agency expressed concern that given the problems with S-101, the condition that caused the breach in Tank S-103 could exist in multiple tanks.
Neither tank has been completely removed from service, and the level of LNG in Tank S-103 is being maintained at one to three feet in order to keep its inner nickel steel liner at the correct temperature. Cheniere has stationed its emergency management team to control access to the tank and monitor any emissions, and it has issued work permits for personnel to “enter the area where there are gas vapors to better assess the tank.”
All five tanks at Sabine Pass were designed by Mitsubishi Heavy Industries. Tanks S-101, S-102 and S-103 were built by one contractor and S-104 and S-105 by another firm. No issues have been reported with the last two tanks in the series.
The cause of the leaks is unknown, and PHMSA and Cheniere have no estimate of the amount of LNG released. A previously commissioned (and previously undisclosed) report on 11 earlier incidents with Tank S-103 suggested that the problems could be caused by splashing of LNG over the top of the inner tank in a “geyser-type effect.”
Based on this information, PHMSA ordered Cheniere to come up with a plan to shut down tanks S-101 and S-103, without opportunity for a prior hearing. “I find that a failure to issue this Order expeditiously to require immediate corrective action would result in likely serious harm to life, property, and the environment,” wrote Alan Mayberry, Associate Administrator for Pipeline Safety. The firm will not be permitted to return these two tanks to service until after conducting a root cause failure analysis, carrying out repairs and obtaining PHMSA’s approval to bring them back online. Cheniere must also determine whether its other three tanks are subject to the same problems.
LNG storage and transportation have a relatively safe history, and unlike heavier forms of petroleum, LNG tends to evaporate in the event of a spill without polluting the immediate area. In 2014, an LNG tank breach caused by an explosion at a facility in Plymouth, Washington, led to a release of LNG from the tank but not to a secondary blast. In at least one instance, though – the East Ohio Gas Co. explosion in October 1944 – an LNG tank release caused widespread damage and multiple fatalities. A leak at a storage site on Cleveland’s east side led to multiple successive blasts that destroyed about one square mile of mixed-use area and killed about 130 people. The accident led to the development of safer methods for LNG storage.