There is some sort of blinker effect when it comes to compressed natural gas. Since it always is compressed in tanks and in writing compressed with “green” or “clean” there is a blind spot that is silly.
In a recent exchange on this website, someone said that there is no reported problem with compressed natural gas canisters in the rear parts of a some lightweight vehicles, so it must be OK and I am an uninformed person. Piece of tin containing a Compressed Natural Gas Canister under the most recent fuel efficiency and reduced weight mandates?
Might I provide for those who care, a warning. Many assume compressed natural gas (CNG), since it’s not gasoline, is good, gasoline is bad. CNG as the new magic.
I don’t presume to know more than Seldon Graham, who knows explosives and he knows carbon based fuels.
Here’s my friend and consultant, Sel, West Point after field promotion to officer in WW II, Petroleum Reserves Engineer, Attorney, explaining, and expounding, for your benefit:
Compressed Natural Gas (CNG) vehicles are mobile Improvised Explosive Devices. The Honda Civic GX sedan canister holds 8.03 GGE (Gasoline Gallons Equivalent) at 3,600 pounds per square inch (psi) pressure. Gasoline contains 124,238 BTUs per gallon. Thus, the Honda gas canister contains 997,631 BTUs of energy. Since one pound of TNT has 2,300 BTUs, this small canister is equivalent to 434 pounds of TNT. Driving a small Honda Civic GX sedan is similar to driving around with 434 pounds of TNT.
I am not a paranoid person, but since when do the proposals, assertions and assurances of a wildcatter/slicker/charming bandido like T Boone Pickens get such weight? Why is it that people who question everything, would accept assurances about driving vehicles with a metal IED/CNG vessel in the trunk?
Have you seen what happened to the Murrah building from an explosive device in a truck sitting in front of the building? Basic components nitrogen fertilizer (ammonium nitrate) and diesel in just the right proportions?
You don’t have to have just the right proportions to blow a CNG vessel. It is an IED and it acts like one, when ignited, on purpose or accidentally. Gasoline is not so energetic.
The point about BLEVE is relevant, but not proof that CNG will not result in explosions through leaks or that it is safer than gasoline or diesel to an extent of assuming that T Boone Pickens will save us from burning up.
CNG is not LPG, and doesn’t react in the same way. The addition of heat will not cause the same kind of phase transition that LPG can undergo.
Clearly something was already wrong. The man dives for the filling line in a panic. The explosion is almost entirely a pressure release, not a conflagration, and the man walks away apparently uninjured despite his close proximity.
The truck itself loses a tank in the front of the bed. This strongly suggests that the driver over-pressured a home-made tank. The problem here is not CNG – it’s the idiot trying to use it in a bodged-up conversion.
Very dangerous indeed when in a car filled with explosives with a detonator 🙂
And what about the ’82 Chevy that rear-ends the CNG car?
“tend to be handled by more cautious operators”
Really?
I think the author’s concern was the introduction of light-weight materials as a container for all of that explosive potential. From there, consider an accident that ruptures the tank and introduces a heat source as a means of ignition.
Would the out-gassing from the tank cause an explosion?
We have seen too many cases of supposing the answer to questions, without actually trying it to see what the facts are.
It seems like it’s time to break out the crash test dummies and see if they burn.
“Only by removing all safety features did they manage to finally explode one using explosives.”
See… I told you they were dangerous!
A catastrophic failure of the tank can result in an “explosion” without fire. When I googled “CNG explosion” I got a number of those. In a fire, the tank pop off valve should release and the contents will add to the fire, but not explosively. However, if the tank fails catastrophically, the results could be “interesting.”
For liquified natural gas (LNG) the main worry seems to be pool fires, where the liquid leaks and burns while it is vaporizing. With liquified natural gas (LNG), LPG and other liquids in sealed containers, the worry is a boiling liquid expanding vapor explosion (BLEVE) which could be with or without additional fire. http://en.wikipedia.org/wiki/Boiling_liquid_expanding_vapor_explosion
BLEVE demonstration videos are very impressive with the tank going 50-100′ into the air.
A CNG tank can’t BLEVE, no liquid. The tanks used in transportation seem to have a pretty good safety record.
You can use flour and margarine as a bomb as well
http://en.wikipedia.org/wiki/Mont_Blanc_Tunnel#The_1999_fire
This one was interesting too. Having lived in the region at the time, according to rumors, cars melted into puddles. And I believed that to this day until I looked it up on the wiki. http://en.wikipedia.org/wiki/Caldecott_Tunnel_fire
The economics and hazards of methane (CNC) and propane/butane (LPG) as motoring fuels are different enough for each to fall in its own class of things. Both have been widely used and neither is known to have caused an extraordinary number of accidents in normal road use.
The hazards are different because methane can only be economical if highly compressed, while propane and butane can be stored as liquids at a relatively small pressure. Both can leak, but methane is lighter than air and is less likely to accumulate in hazardous amounts. Gasoline has enough volatile fractions in it to make it a hazard that is quite similar to LPG.
Storage overhead is higher for LPG than for gasoline, and is the highest for methane, but depending on where you are, one of the three types of fuel may be significantly cheaper than the other two. An additional complication is that conventional piston engines are not robust enough to run on methane. Their valves burn out at a much faster rate (about 2x), adding to the overall cost.
None of these fuels is in any way extraordinary. Moscow city trucks and buses have run on methane since 1960s. Taxis (when they were owned by the state) used LPG. In 1985, 3.7% of all cars in Russia used methane and 2.8% used LPG. Many private car owners chose to fit LPG systems to their cars to save on fuel costs (although I recall some were wary about riding with a propane tank in their trunk). I don’t recall any news of explosions involving these vehicles. Gas explosions in people’s homes seem to be much more prevalent. My sense is that it is a mature technology that makes such accidents unlikely.
These are all mass-produced vehicles:
for LPG:
http://cache.zr.ru/wpfiles/uploads/2011/06/201106021142_1-575×359.jpg
for methane:
http://ntrtv.ru/uploads/posts/2013-05/1369976071_avtobus.jpg
This one can use any fuel sold in the country:
http://rostec.ru/content/images/other/камаз/какмаз-на-гБО(1).jpg
A leak of natural gas into a house at some point provides a mixture that will support rapid combustion. The explosive limits (upper and lower) bracket the concentration at which a mixture of the substance and air will support the reaction. Below the lower limit, the oxidation of the substance will not provide sufficient heat to warm the mixture up to its ignition temperature, above the upper limit the mixture contains too little oxygen to heat the compound to its ignition temperature.
Truly explosive substances do not require injection of oxygen or air. The rapid decomposition of those compounds, TNT, nitroglycerin, gun cotton produces large volumes of gaseous reaction products, which provide the explosive force.
In much the same way that Ralph Nader and the lemming stream press ruined the reputation of the Chevrolet Corvairs.
How about a practical experience.
In 1973, a “bomb train” moving from a manufacturing plant in Nevada to the Oakland (CA) Army Terminal caught fire, then had “low order” explosions as the fire set off bombs in the freight cars. The fire also spread to other nearby rail cars, including tankers with 30,000 gallons of LP gas. The LP gas cars exploded with rather more energy than the 100 or so 500 lb bombs (many did not explode) in the freight cars. Indeed, much of the damage caused by the fire was attributed to the LP gas tank cars.
The explosion of LP gas rail cars is not a freak accident. On October 13, a train in Canada had 9 LP gas freight cars explode along with 4 tankers filled with petroleum just outside Edmonton.
I also recall (but was unable to find any reference) a fire causing explosions of as many as 50 LP gas tank cars in a rail yard near St. Louis — probably in the early 1980s.
Since explosions of compressed gas rail cars is not all that uncommon — with railroads generally having far fewer collisions than automobile traffic — that compressed gas fuel tanks may be a serious hazard — though lessons learned over the years (e.g. the gasoline fuel tank explosions of Ford Pinto compact cars that were “rear ended” in collisions back in the 1970s) may allow sufficient engineering to reduce the hazard — but it will still exist.
=====
CNC is not, necessarily, billed as “more efficient” than gasoline, only that it is sourced in the U.S. (and Canada) and could be used to reduce our dependency on foreign oil as well has have a slightly lower “greenhouse gas” content than liquid fuels. However, the fracking revolution has also been applied to petroleum recovery, and North American production is up significantly. This past year, the U.S. has substantially reduced use of foreign suppliers, with some 71% of petroleum coming from North American sources — up from about 55% a few years ago.
Which is interesting because government safety data showed that the Pinto was one of the safer cars from the era according to government data. The perception we have of the car was due to media hysteria propped up by “consumer advocates.”
Well yes – that is because the energy density is really low co.parednto gasoline or even ethanol – so to compensate so you can get decent mileage and still have room to sit in your car – they put in underpowered smaller engines. That is also why CNG is recommended for trucks. Less space constraint.
It would actually make more sense to me to convert the NG into ethanol and use that is normal cars than to create cars with CNG tanks.
excellent commentary, mr. G.
seldon, meet bob greene, a regular contributor of great knowledge at the junk science web site. He has or is recently retired from a compliance position with a concern that does chemical manufacturing from what I can tell from his hints.
John Dale Dunn MD JD Consultant Emergency Services/Peer Review Civilian Faculty, Emergency Medicine Residency Carl R. Darnall Army Med Center Fort Hood, Texas Medical Officer, Sheriff Bobby Grubbs Brown County, Texas 325 784 6697 (h) 642 5073 (c)
Gasoline in auto tanks is not pressurized to 3200 psi (or similar). Any compressed gas wants to leak out. In a closed garage, this can produce exciting results. I saw the remains of a house with a natural gas leak. Not fun to be nearby. So, no, it will not explode on its own, but if it leaks …
Further, it takes energy to compress the stuff. Energy that is not recovered. Worse if cooled to liquid. Take that into account, and the claimed efficiency declines.
It seems that similar reasoning could be used to determine that gas tanks on normal vehicles also create an IED. It is well known that gasoline is highly combustible.
Ford Pinto comes to mind
The most likely event is a fire as the methane burns off the rupture/vent.
I don’t think the energy comparison is relevant without defining the process. Explosives are marked by extremely rapid, exothermic decomposition (detonation) because they carry the oxidizing agents and fuel in the container and do not need atmospheric oxygen from air. Gunpowder and dynamite (nitroglycerin) are examples. The rate of reaction determines whether the explosive needs to be contained to actually explode. For many, the reaction must be contained to get more than fire. Gunpowder is an example, it burns and does not explode when it is not contained.
For methane (CNG) to burn the methane concentration must be between ~5% (LEL) and ~15% (UEL) in air. Similar for gasoline. Less than 5% you need other fuels to burn methane and greater than the UEL you don’t have enough oxygen. Theoretically, you can put a match out in a 20% methane vapor or gasoline. To get an explosion from methane (or gasoline) you need to disperse enough of the material in air and then have an ignition source, but you’d need a large volume to get the IED effect. They do this with fuel air explosives (FAE’s) by a small explosive device to spread the vapor in air followed by a second ignition to detonate the vapor cloud.
To get the FAE effect from methane, gasoline or other chemicals you need to contain the vapor then ignite, so you need a building or a very still wind. I’ve had the fun of being in a building that contained about a ton of toluene vapor when the sump pump cycled. Blowout panels do their thing, the roof lifts and walls go out and you get to watch the pressure wave come down the warehouse at you. Only the vapor “detonated” and the remaining 3k gallons vented out of 2′ reactor man way like a butane lighter. (If you need any more adrenalin, putting out a lighter with a 30′ flame that’s 24″ in diameter will add things that keep you awake for a while.)
Europe bristles with LPG fueled cars. When i bought my caddy 1975 eldorado it had a LPG tank fitted. (which i stripped immediately ofcourse) No major acidents have occurred for decades with LPG fueled cars. They even tried to get a lot to blow up, but the emergency vent just blew and spewed along flame for a while. Only by removing all safety features did they manage to finally explode one using explosives.
Watch this man’s natural-gas pickup explode as he refuels it – Autoblog – Jan 25th 2013 12:44PM
We’ve reported before on the proliferation of natural-gas powered vehicles in the heavily oil-sanctioned state of Iran. Now we’ve got some further very dramatic circumstantial evidence that not all of the Compressed Natural Gas (CNG) vehicles are as safe as their Iranian owners would hope.
It’s hard to say just what caused the violent ending in this pickup refilling video – a KTLA rebroadcast from an unidentified news source – but the result is terrifying. In light of this catastrophic clip, we’d be remiss if we didn’t mention that CNG vehicles have an excellent safety record here in the US. Follow on below to watch the video clip.
http://www.autoblog.com/2013/01/25/watch-this-mans-natural-gas-pickup-explode-as-he-refuels-it/
Due to a mandate by the Muldoon government (1975-84), there were at one time rather a lot of CNG powered vehicles on New Zealand roads (not any more, all the refueling stations are long gone). I don’t recall any massive rash of explosions at the time. My CNG powered van was awfully gutless, though
There plenty of gas powered vehicles on the road today. You should be able to find reliable statistics for explosions per capita, collateral damage an so on.
Anytime I’ve heard Pickens talk about his scheme, it was alwats for commercial fleets and trucking.
I am amused by the belief that propane gas cylinders are bombs. They were employed as such by the Columbine jerks, by a doctor who attacked the LAX airport, and by the idiot who tried to bomb Times Square in New York City. Propane and CNG are gases that can burn and release prodigious energy. But they are no more explosive than a block of wood that can burn to release energy. Propane, CNG and wood require an oxidizing agent. A mixture of hot wood and air can generate horrific forest fires, and mixtures of propane or CNG and air will explode – that is how engines work. But to compare CNG to TNT is big time ignorant.
There are enough vehicles with nat gas that you ought to be able to find real numbers of explosions per 1000 vehicles and deaths and other doom and gloom.
Also, Pickens always talks about Trucking and commercial fleets but that would be even more scary. Don’t tailgate any buses or garbage trucks or UPS or… Better to just stay of the road until you get the data.
Gotta disagree. You’re falling for the Hindenberg worry. Yes, there’s energy “locked up”, so to speak, in CNG tanks – just like there is in gasoline tanks.
The question is… is there a significant difference in explosive and other risk between one and the other?
The answer, so far, is that CNG is a touch safer.
Now a lot of that is because CNG powered vehicles, at least in the US [we won’t talk about Russia and Gazprom] are newer, and tend to be handled by more cautious operators. But there’s certainly nothing approaching a huge risk increase in going with CNG.
–