In a complete about-face, the Department of Homeland Security (DHS) is now saying that highly flammable polystyrene is used to insulate liquefied natural gas (LNG) cargo tanks on carriers.

“DHS’ previous statement [in May] that foam polystyrene insulation was not used on LNG carriers was incorrect,” the department admitted last month in a letter to Rep. Edward J. Markey (D-MA). The department made the concession after Markey challenged its earlier claim.

“I’m concerned that neither the Coast Guard nor the Homeland Security Department have focused enough attention on the potential vulnerability of LNG vessels to terrorist attack, and the fact that they were unaware that many LNG carriers use a highly flammable insulating material until I informed them of this fact…,” said Markey, a senior member of the House Homeland Security Committee.

Pamela J. Turner, assistant secretary for legislative affairs at DHS, also wrote “there [was] no U.S. mandated standard for LNG carrier cargo tank insulating material.” But she said that all vessels were required to meet international safety codes.

The two most popular materials to insulate LNG cargo tanks are polyurethane and polystyrene “because they are especially well suited to maintaining the cargo at cryogenic temperature under ambient conditions,” Turner said. At the same time, “the chemical and physical properties that make these materials desirable as a cryogenic insulator render them undesirable as an insulator from the radiant heat that could be expected from an LNG pool fire that might result from the breach of a cargo.”

But she noted “due to the location of the tanks within the vessel’s double hull and under a protective steel cover, it is highly unlikely that a flammable atmosphere would occur inside the vessel that would result in direct flame impingement on the insulation.”

A current study underway by the Department of Energy’s Sandia Laboratory “is expected to examine how the cargo tank insulation would perform under an extreme fire load, and the degree to which insulation decomposition could affect the survivability of undamaged cargo tanks,” Turner told Markey.

“I’ve been hearing for months that the Sandia study is supposed to provide answers to this and other questions that I’ve been raising about LNG safety, but this report is long overdue,” Markey said. “We need to have these safety questions answered now before the FERC approves any new LNG terminals in New England, and we need federal regulators to start putting more emphasis on ensuring that the public safety issues associated with LNG are being properly addressed.”

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