Thanks for this Dave.

I hope everyone can remember the last scene of Syriana. What they don't show is that an LNG explosion would look like a small atomic bomb going off. Siting them will be a big battle if it's close to major population centers. This is where you find more "survival NIMBY" than "I don't like seein' windmills off in the distance" stupid NIMBY...

To play devil's advocate, LNG ships
have the safest records of any fuel
delivery ship at the moment.  We have
never seen a LNG ship explode into
pieces.  Because LNG ship accidents
are pretty minor, we do not really
know what happens when a LNG ship
is hit with a bomb like USS Cole
or a tragic accident like Exxon Valdez.

To claim it is too dangerous is without
evidence.  What is to say that a major
accident won't just make the ship into
a burning island?  Why does it have to
explode and destroy the port and the
people living nearby?

Actually, I have not come across a super
explosion that wiped out nearby buildings
for NG storage facilities.  Albeit, they
are mostly underground.

Unlike most bombs, an lng "exlosion" needs oxygen. So it first quickly burns oxygen in surronding air, causing a tower of hot air (actually, products of combustion) that rises, sucking in air at the base. Accordingly, at low levels it creates a partial vacuum and acts as an implosion, the opposite of a bomb.
I remember an influential article in the Los Angeles Times back probably in the 1970s when they were considering putting an LNG terminal in at Long Beach. The article vividly depicted the consequences of an explosion and fire at the transshipping facility. A wave of burning, evaporating methane gas would roll across the city, creating a fire miles on a side that would reach almost to city hall. The conflagration would be almost nuclear in its consequences. I don't know how accurate the story was (or my memory of it for that matter), it may be exaggerated, but it had an impact and that was the end of the idea back then.

Now they are trying again to put in an LNG terminal at Long Beach, and faced with opposition there they are looking at going about 70 miles up the coast to the Ventura/Oxnard area. The Ventura facility would be built offshore to avoid the fire risk, with an undersea pipeline bringing the gas inland (not sure if it would be liquified or vapor at that point). So far that plan is not exactly being welcomed either. It is a real NIMBY situation, nobody wants to get barbecued.

I don't have any hard data to back up this, but a professor of Energy Resources in the University of Barcelona told me once that there was a study that simulated the effects of an explosion in the regasification terminal here in the port of Barcelona, the effects were pretty similar to those described below. In any case, it depends on what is in the surroundings of the exploding tanker. Here in the Barcelona harbour we have a lot of gas and oil depots...
Cold boiling liquid escapes radially from a point source and flows along the ground or sea until it flashes into cool vapor.  Until it has mixed with sufficient atmospheric oxygen, its is not an explosive mixture.  If you light a match, the match is extinguished.  As the cool vapor expands on heating from surface contact and atmospheric mixing, it continues moving outward from the source until it is eventually heated to ambient air temp.  At that point it becomes lighter than air and starts rising.  As the gas  mixes with the oxygen in the air, it eventually reaches explosive limits and starts looking for an ignition source.  <At this point it is very important to extinguish all smoking materials>  If no ignition source is encountered, the gas rises into the air and <"harmlessly"> contributes to the greenhouse effect.  If ignition occurs, rapid combustion follows and heated expanded vapors quickly cause an updraft usually sufficient to pull back any remaining gas mixture in the surroundings near the ground and all is sucked into the updraft and rising fireball.  Consequently, surrounding gas now well mixed with atm O2 is rapidly displaced upward into contact with fireball causing even bigger and more spactular fireball that rises several hundred meters into the air, as radiated heat converts all nearby objects <if there are still any nearby> into melted crispy critters.  Just digging into a large pipeline with a backhoe can cause fireballs and flames that can easily reach 200 meters high and melt the backhoe and unfortunate operator in a few ms.  Happening on the scale of an LNG tanker would be a hell of a photo opportunity.
What about Algeria in 2004?

What about Cleveland in 1941?

Thanks.  I forgot about the Cleveland
incident, but Cleveland incident happen
in 1944.  It was not a LNG tanker accident,
but a storage tank not built to specification
due to war effort and shortage of metal.
The new storage tank was not air tight, so
the resultant LNG mixed into the sewage
pipes and exploded killing hundred plus people.
LNG tanks build with 9% nickel has never
display a crack in 35 years of history.
This example was not built to 1941 US gov't
code for proper storage tank.  Of course,
accidents will occur if people are not
building according to regulations.

Talking about accidents in US.  There are
at least 2 other accidents involving deaths.
None of them involve tanker explosions.

As for Algeria's accident, that didn't cause
a nuclear like explosion.  This accident
results in damage similar to refinery plants.
Those things explode, too.  None of these
severly damage towns, etc.

The Cleveland incident is the worse one.
Hopefully, today's regulators and inspectos
will do a better job.

FYI: I am not an advocate of LNG.  I was
just playing devil's advocate.

A local Boston TV program did a program on the facility in Everett, Massachusetts. They got a tour and interviewed one of the company big-wigs. Mayor Menino has actually expressed his view that he would like to get this thing out of here due to the "safety" concerns.

What the company representative said, however, contradicts some of what has been written here regarding an LNG tanker explosion.

I have done some quick, online research in the past and what I found out generally confirms what I heard on the TV show. However, I don't claim to be an expert on LNG - so if what I say is crap, please let me know.

LNG in liquid form is not flammable. It needs to be in the range of between 15-25% concentration of the atmosphere/oxygen around it to explode.

In the movie Syriana, the terrorists were using what appeared to be a shaped-charge armor-piercing SRAW anti-tank rocket. This round is fully capable of piercing the outer hull of the tanker. However, I am guessing that there is a gap between the outer hull and either a second hull, or the LNG cooling container within. It is doubtful that this round could penetrate the second wall, having exhausted it's charge on the first.

Even if the rocket did produce a hole in the LNG compartment allowing LNG to escape to the outer atmosphere, that liquid would have to completely regasify and drift into a cloud where the methane was between 15-25%(taking who knows how long) - and then be independently ignited by some other source for there to be an explosion.

Again, this is conjecture based on some things that I have heard and trust. Any contradictory info would be greatly appreciated since this is an issue of national security that deserves full discussion.

Don't know about the rocket, but the liquid would instantly gasify on contact with the water.  The water would eventually freeze into an ever-expanding ice floe, and the liquid methane would run out across the floe.  The flowrate through the tanker hole would essentially be gravity driven; the tanker would depressurize quickly.

What happens next depends on the wind speed and direction.  The cold methane will hug the ground; on land it will follow low points like valleys or streets.  As it starts to mix with the surrounding air an opaque cloud will form from the condensation of water vapor.  How fast it mixes depends on the wind turbulence.  You would first get a severe asphyxiation danger from the cloud and then an explosion danger.  If the cloud reaches the explosive limit then something like a automobile distributor could set it off.

Great info Dave!

Question: how much BCF can be on one tanker, and if there was a problem, what is the size that that gas would expand to? In other words, how big is a billion cubic feet of gas in the air? I assume 1 billion cubic feet is 1000x1000x1000 so is a cube the size of three lengths of football fields on each side (per bcf)

When the gas industry says cf of gas they usually mean standard cubic feet, which is at 60 deg F and 14.696 psia.  So a billion standard cubic feet of gas at normal ambients occupies close to a billion cubic feet of actual volume (or water volume).
Largest LNG tanker now holds 'bout 145K m3 of tank vol => 3 BSCF (billion standard cubic feet)

probably increasing in future to 200K m3 of tank vol => 4 BSCF

Tanks are thinner towards the top and looks like future tankers will be using aluminum tanks to save weight.

Sandia Labs study classifies a successful terrorist attack on an LNG tanker as a, "Low probability, high consequence  event." Radiated heat would be damaging within a 1 mile radius.

The tops of the LNG tanks are protrude about 30% above the deck.  Just shoot high and no hull to slow it down.  The spherical tanks are mostly well inside the hull, only getting near the hull at 3 tangent points, so a hit on a tank after hull impact would need accurate placement on the tangents.  The LNG tank itself is an outer steel shell, about 3 ? feet of expanded perlite type insulation, and an inner steel shell.  Shell thickness is about 50mm (2") steel. No way near like hardened armor.  I'm  no explosive expert, but seems like anything that can get through the first layer <rocket qualifies>, would still have enough momentum to make it the rest of the way, as the inner tank will have high specified Sharpy V-notch toughness, but at low temps could be pretty brittle for a head on impact from hi vel chunks.  I'd think you'd want to keep all the little rubber boats away from these things.    
I have not seen the movie Syriana yet, and I am a little dubious of Hollywood's representation of weaponry.  (These are the same guys who are trying to figure out how many shots are in a six-shooter.)

That being said, a SRAW (or Short Range Assault Weapon) would be an excellent choice, but a bit of an overkill (and kind of expensive given the price of RPG-7s).  The SRAW is American and RPG-7s are cheap, cheap, cheap.

Most hand-held rockets of this type use a shaped charged warhead.  If you think of the pointy end of an RPG rocket, this is actually a hollow, copper cone.  The explosive behind it is also hollowed out, so there is a cavity.  When the warhead explodes, this crushes the copper into a bit of plasma and shoots it forward (This is called the Monroe effect for those still reading).

The average RPG-7 will burn through about 330 mm of steel.  The good news is, it will burn through about 330mm of air too once the round explodes.  A common defense is to put a grate or something up to make the round explode before it hits the tank.  The latest upgrades to the US M-1s have a louver across the back to protect the engine.  So long as you have a foot or so for the plasma to burn up, you are good.  Reactive armor works in a similar fashion by using an explosion to disrupt the plasma jet.  (Friendly infantry don't care for this though).

The bad news is, a rocket can have 'stacked' warheads, so one explodes, disrupts the louvers, and the second one goes through.  Another solution is using multiple rockets.

Would an anti-armor rocket work against a LNG tank?  I don't know.  The insulation between the two tanks would certainly disrupt the plasma jet.  However, the explosion will make one hell of a hot spot on the tank and surely crack the tank.  I just know I don't want to be there when it happens.

I guess I won't ask what you do in your spare time...
I love TOD just for stuff like this!
Ya with a name like that; better you don't.
Everyone needs a hobby.