Safe Harbor?

Ships bringing liquefied natural gas from the Middle East pass regularly through Boston Harbor. Experts say there’s little chance of an LNG tanker going up in a fireball. Then why are city officials so worried? Should you be?

Can LNG catch fire inside the tanker?
LNG itself is not flammable. You could light a match, drop it into a vat of the stuff, and be perfectly fine. Yet if LNG, which is extremely cold, spills out onto the relatively warm ground or water, it immediately starts to evaporate. That forms a vapor, which is flammable, but only under certain conditions (see “The Fire”). LNG tankers are built with double hulls, each made of one-inch-thick steel. By contrast, the USS Cole had a single hull of half-inch-thick steel.

Would it be easy to blow up a tanker?
Successfully attacking an LNG tanker would be very difficult, experts say, but it’s hard to say exactly how difficult. For most ships passing through Boston, an attacker coming from outside the ship would first have to breach the security zone, then cause a leak by blasting through about 30 feet of the ship. Sandia considered all conceivable means and methods of attack for its 2004 report, though that part remains classified. “We got drawings of the ships and did very high-definition structural calculations of the damage you would get from those types of credible threats,” says Mike Hightower, one of the study’s authors. “We [considered] things like an attack, a hijacking, an insider threat where a member of the crew…brought some explosives onboard. We looked at a range of weapons, and we looked at things people could make into weapons: small aircrafts, small boats.”

Do LNG accidents happen often?
There hasn’t been a major LNG incident since the 1944 storage-tank explosion in Cleveland. And a shipwreck doesn’t automatically mean disaster: A tanker once hit a rock outcropping head-on in the Strait of Gibraltar and had to be towed to port, yet lost not a drop of LNG.

  • Robert

    Skikda, Algeria, had a catastrophic LNG accident in 2004, that killed 26 workers and injured 74.

  • Robert

    LNG storage tanks contain vapor (called “boil off”) at the top, above the liquid. It does not require pouring onto land or water to vaporize — it simply needs a slight rise in heat.

    The statement about a lit cigarette and LNG vapor flammability give a false impression of safety. Liquid gasoline will not burn until it vaporizes, either.

    LNG vapor is 3.7% more flammable than gasoline vapor. Methane (LNG) has a fuel-to-air flammability range of 5% to 15% (a 10% range), while gasoline has a flammability range of 1.4% to 7.6% (a 6.2% range). Neither will burn or explode outside those ranges.

    The Federal Government has defined LNG ship Hazard Zones that extend 2.2-miles from the ship. The hazards within those zones include cryogenic burns, asphyxiation, fire, thermal-radiation burns, and explosion.