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Permalink Reply by Jack Blake on October 18, 2010 at 1:38

JB remembers thosen cars. Jack believes the Pintos would explode when hit in the back and on the Vegas if hit in the front the hood would behead the driver. At least that is what JB's Uncle Gene said.
He did not like foreingn or small vehicles and I can't remember him ever owning a small or foreign vehicle.
JB

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Permalink Reply by P.G. on October 18, 2010 at 9:44

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Permalink Reply by The_Baron on October 18, 2010 at 10:11

natural gas itself is a safer fuel than either gasoline or diesel fuel. It has a limited range of flammability, meaning it requires the correct mixture of air and fuel to burn—somewhere in the 5 to 15 percent range, and an ignition temperature of approximately 1100 degrees F. Compare that to gasoline and diesel fuel which both have lower concentrations of flammability and lower temperatures of ignition

Because compressed natural gas (CNG) fuel systems operate at pressures in excess of 3000 PSI, the fuel tank and associated plumbing have to be incredibly rugged and strong enough to contain that pressure. The on-board tanks are made of steel up to one half-inch thick and often wrapped in protective reinforced fiberglass sheathing. Plus, newer tanks are constructed of polymers and composites that are stronger than steel.

Contrast this with standard gasoline and diesel tanks in regular vehicles. These tanks are usually made from stamped steel shell halves, just a few thirty-seconds of an inch thick, that are welded or crimped together. In the event of a traffic accident, the ability of rugged, durable CNG tanks to withstand rupture or puncture certainly exceeds that of simple stamped steel.

But the safety of NGVs doesn’t just stop with the robust construction of the fuel tank. To take it a step further, most CNG systems have automatic release valves. In a situation of excessive heat or pressure build-up, the valve will open and release the gas to the atmosphere—and since it is lighter than the surrounding air, it will rise and dissipate. The low threshold is set well above ambient temperatures and the high threshold is set well below the ignition temperature of the gas. In the event of a fire, the fuel is safely evacuated from the car before it ever has a chance to catch fire. Gasoline and diesel vehicles simply can’t do that.

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Permalink Reply by P.G. on October 18, 2010 at 12:32

I read where LPG makes a good refrigerant. I wonder if NG would be similar?



LPG can offer following advantages when used as a refrigerant:

1) The cooling capacity of LPG is 10% higher than R-12 and the vapour pressure is appropriate.
2) LPG is naturally occurring and non-toxic.
3) Use of LPG as a refrigerant also improves the overall efficiency by 10 to 20%.
4) The ozone depletion
potential (ODP) of LPG is 0 and global warming potential (GWP) is 8 which is significantly negligible as compared to other refrigerants.
5) Apart from environment friendly, use of LPG also gives us lot of cost advantages.
6) LPG does not form acids and thereby eliminates the problem with blocked capillaries.
7) There is 60% reduction in weight of the system due to higher density of LPG.

The only disadvantage of using LPG as a refrigerant is its flammability. It is highly flammable. This paper elaborates various precautions that need to be taken to safely use LPG as a refrigerant. The amount of LPG used for each appliance should be too small in order to avoid any risk for technicians and customers. Thus by minimizing the possibility of leak and following some international standards, the use of LPG as a refrigerant can be safely implemented.

http://www.engiblogger.com/mechanical/lpg-as-refrigerant/

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Permalink Reply by The_Baron on October 18, 2010 at 7:19

N.g requires a certain concentration in air to explode. You will smell it long before it is explosive.

Furthermore, the cylinders in vehicles are pretty tough.

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Permalink Reply by Mac Davis on October 18, 2010 at 14:11

LNG liquid natural gas has no odorant, so you won't smell a leak from a LNG powered vehicle.

The main focus for automobiles is CNG compressed natural gas, which should have a smell. LNG is being used and is under consideration for 18 wheelers.

i.e. if it's a truck, don't be too sure you'll smell something first.

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Permalink Reply by Linda Whatley on October 20, 2010 at 3:34

Hey Mac,

What does your "i.e." comment mean?

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Permalink Reply by The_Baron on October 20, 2010 at 4:10

Alright Mac. Lets interject some facts here.

LNG does not explode or burn.


It will if suddenly released from containment, begin a rapid transition to gas.


Natural Gas must be in a gaseous state to burn and only when its concentration is just right, not to low, or too high.

Furthermore, I have heard of lng being proposed for trucks, but this tech seems to be extremly expensive and unlikly for widespred use. are you sure you aren't talking about lpg?

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Permalink Reply by Mac Davis on October 20, 2010 at 5:23

It will if suddenly released from containment, begin a rapid transition to gas.

Yes, and the gas it transitions to will explode or burn.

Gasoline isn't explosive in its liquid form either. You have to let gasoline vapors form before gasoline will explode. We just think liquid gasoline is explosive because it evaporates rapidly and readily forms an explosive concentration of vapors.

Gasoline vapors will not burn or explode unless the concentration is right, either. (Or alcohol vapors, kerosene vapors, jet fuel vapors, etc. In general, a gasoline tank and LNG/CNG tank usually can't explode because the vapor mixture in the tank is too rich (too much fuel.) Diesel or jet fuel tanks usually won't explode because the vapor in the tank is too lean to burn.

Spill a large amount of LNG (or CNG). The initial concentration of the gas may be too rich to explode. Sometime later, it will be too lean to explode. Somewhere in the middle, it will be in an explosive range.

Put a LNG/CNG vehicle in a poorly vented area or even outside without much wind. Start a leak of gas or LNG. Somewhere in the area, there will be an explosive mixture of methane and air.

LNG/CNG may be less dangerous than gasoline. It's a bad idea to be telling people that it won't explode or burn, though.

Baron, I mean LNG, cryogenic liquefied natural gas trucks. I believe this was part of one of T. Boone's grand schemes. Google LNG trucks, there's a lot of articles, and apparently a number of local fleet operations that use LNG. I don't have a good idea how many LNG trucks are actually out on the road, but Kenwood and Mac have them in their catalogs.

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Permalink Reply by P.G. on October 20, 2010 at 5:28

I wonder if there have been any studies of actual crashes where one was any more of a fire hazard than the other or perhaps less of a hazard?

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Permalink Reply by The_Baron on October 20, 2010 at 7:23

I've seen crash test videos of cng cars. The tank is virtually indrustructable.

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Permalink Reply by Mac Davis on October 22, 2010 at 8:28

The tank may be indestructible, but the fuel connections to the tank aren't. The gas is under pressure, and if you break off the fuel line, the natural gas will escape from the tank.

Have you ever seen video of what happens when you break the valve off the top of a welding tank? All the gas comes out very quickly. Remember, methane mixed with air is a lot more deadly than methane inside the tank.

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