Hydrocarbon Refrigerants - Flammability

[Kestas]

This is a hotly debated issue. If you want facts, there have been no documented cases of any horrible fiery instance from someone having HC refrigerant in their a/c system, even though there are many cars on the road with HC in the a/c system. This danger is way overhyped.

We're talking about roughly 8 ozs HC in a car. I find it difficult to worry about it considering the many gallons of volatile gasoline a car carries. Plus, the HC would need to be rather concentrated for ignition.

Explosion from lighting a cigarette or static electricity inside a car with a leaky system?... I would expect a person wouldn't get inside a car that reeked of propane. Even if the smell was strong, it still needs to be concentrated enough for ignition.

Explosion from an accident rupturing the a/c system?... Again, the HC needs to be concentrated and there needs to be an ignition source. The HC would vent so fast and would get diluted rather quickly in the unfortunate event of a crash.

Someone would be hard pressed to find a situation where 8 ozs of HC refrigerant would pose a threat to someone, without that person ending up as a candidate for a Darwin award.

Here's a couple of web sites if you want to research this further. In one of them is buried factual evidence (or lack of).

http://www.autoacforum.com/categories.cfm?catid=2

http://acsource.net/acforum/viewforum.php?f=1

 

[Oldswagon]

Thanks for the response. I do think that this is perhaps an overhyped worry, but I have yet to find any concrete data either for or against. I was reading quite a bit through this forum's archives and that autoacforum.com website before I decided to post.

From reading the MSDS for Duracool, it states that the auto ignition temperature is 1630*F, yet does not state at what temperature it becomes flammable. I am assuming that this product is flammable at room temperature though, since both propane and butane are at that temperature.

However, according to the MSDS for propane, it has a autoignition temperature of approx 430*F. Does this mean that for propane to combust, it must have an ignition source with at least 430*F? If so, does this not mean that Duracool would require a 1630*F ignition souce? If I am misunderstanding please clarify.

I know that some HC sites state that R-134a has a autoignition temperature lower than that of HC refrigerants. However, it is my understanding that since R-134a is not combustable, basically this means if it were to be heated to that temperauture it could self combust. However, introducting a ignition source of 1300*F at room temperature will not cause combustion, since it is not flammable.

If my above conclusions are correct, what is the likely hood of having a 1600*F ignition source in a car? How hot would an automotive electrical short be? Obviously, a cigarette wouldn’t be able to ignite Duracool, since according to mythbusters it could not even ignite gasoline (autoignition of approx 540*F).

Further feedback and discussion much appreciated.

 

[Gary Allan]

Wouldn't it become flamable instantly? It will burn as long as there is an environment that will sustain a flame. I think you're mixing some terms here ..or misapplying them. Aren't you more looking for "explosive limits" which would be dependent upon concentration levels

I know you sorta covered this ..but the difference is that the HC is inherently flamable.

 

[mechtech]

R134a doesn't cool quite as well as R12.
Especially in a system that was not designed for it.
If the system failed, however, the conversion was NOT done right. That is not a fault of R134a.

 

[Oldswagon]

quote:

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Originally posted by Gary Allan:
Wouldn't it become flamable instantly? It will burn as long as there is an environment that will sustain a flame.

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Perhaps I am misunderstanding terms, which is why I am posting this question. It's been a while since Chemistry class (too long perhaps), but I thought for combustion to occur you need fuel and air mixed in proper proportions. Then you need an energy source to start the process. You can mix all the gas and air you want, it won't start to burn without a spark.

However, the ignition source has to have enough energy to start combustion. I thought that the level of energy required was the autoignition temperature.

For example on mythbusters, they tried to light gasoline with a cigarette. No matter what they did with the cigarette, they could not get the gas to ignite. They discovered the the cigarette would only burn at about a max of 400*F, while it requires over 500*F for gasoline to ignite. The autoignition temperature of gasoline is over 500*F.

So what I am saying is that if Duracool is leaking into the car, it is flammable. However, it needs to be first off in the proper proportion with air to ignite, and it needs an ignition source with enough energy to start to burn. IF the autoignition temperature reflects this energy requirement, then the spark or flame would have to be 1600*F for the Duracool to burn.

My questions are then,

1) Is autoignition the amount of energy required to START the burning process when the fuel and air are mixed in proper proportions?

2) Are there any sources of energy in a car that could produce a 1600*F energy source, such as an electrical short?

quote:

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If the system failed, however, the conversion was NOT done right. That is not a fault of R134a.

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Well, it failed due to component failure which caused the refrigerant to leak. However, before this car was switched from R12, not only did it cool better, it didn't have one A/C problem from new. My truck also failed after it's conversion, again done by the dealership. Does R134a have smaller molecules than R12, causing it to be more likely to leak? All the seals were replaced in both vehicles.

 

[Bob Woods]

Does R134a have smaller molecules than R12, causing it to be more likely to leak? All the seals were replaced in both vehicles.

Yes, and the optimum operating pressures are different too, to convert from Freon12 to 134A you really need to change the old hoses and the expansion valve and dryer/receiver.

 

[Oldswagon]

With the summer heat beginning, I have been thinking about repairing my A/C system in my vehicle. After reading the recent thread on Maxifrig refrigerant, it got me looking into alternative choices for refrigerants.

My vehicle was original equipped with R-12, and was since converted to R-134a by the dealership. The conversion didn't as well as original, and it also didn't last long before the system failed. Since R-12 is practically been eliminated in Canada, I couldn't even go back to it if I wanted to do so.

That leaves me with the option of going back to R-134a, and hoping it lasts longer this time or trying a much cheaper and better hydrocarbon based refrigerant.

Of course there is much concern over the flammability issue of HC refrigerants. I looked at the MSDS for Duracool, and of course it does list the autoignition point, but nothing about flammability temperatures. I am assuming though that this stuff would be flammable at room temperature, but how hot would the ignition source have to be? The auto ignition of Duracool is much higher than that of propane, but does this effect the flammability at all?

http://www.deepfreezeinc.ca/msds.htm

Now, the purpose of this thread is to begin a discussion on the safety of this product. I don't want anecdotal evidence, rather actual facts and data that can prove or disprove the real world safety of this product. Obviously there are many people who are using HC refrigerants, and some even using straight propane. If these products are dangerous as some claim, there must be some record of a failure? Would liability be an issue for the companies peddling this stuff?

 

[toocrazy2yoo]

Perhap the hoses are seeping, if not leaking but..

When I help folks with their conversions that didn't last long, what I find is the techs that did the conversion simply are not sealing the adaptors at the high and low side ports. They tighten them down, but they work loose just a crack, and out goes the charge.

When I use a wrap of teflon-tape around the threads of the old ports, THEN put the 134A adaptors on, the charge holds real well. Either the tape is sealing the threads, or it's absorbing vibes that would allow the adaptors to loosen, I'm not sure which, but if you're losing the freon on a conversion, this is where I have the most trouble, and the fix that is most successful with conversion-trouble.

 

[Oldswagon]

quote:

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Originally posted by toocrazy2yoo:

When I help folks with their conversions that didn't last long, what I find is the techs that did the conversion simply are not sealing the adaptors at the high and low side ports. They tighten them down, but they work loose just a crack, and out goes the charge.

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Thanks for the tip! I will look into that.

As far as my original question goes, I think I was able to partially answer my own question through research. I read on those A/C forums that since Duracool is a blend (propane, butane and isobutane according to the MSDS), when it leaks, the lightest component leaks out first. So, in this case if the Duracool leaks, it can be as flammable as the most flammable of it's components.

In this case butane has the lowest autoignition temperate, at 287*C, propane at 432*C, and isobutane at 460*C. So Duracool is potentially as flammable as butane if it is leaked out of an A/C system.

When researching I also came across a guy who put R152a into several vehicles and has had long term success with it. R152a, Difluoroethane, is commonly available as electronic duster aerosols. It is too however flammable, but not to the same degree as HC refrigerants. In fact the auto industry seems to be considering both R152a or CO2 as the next refrigerant.

R152a, is rated as a ASHRAE A2 [flammable]substance, as opposed to ASHRAE A3 [flammable],which HC's are rated . R134a is A1, which is non-flammable. It seems that A2 products are flammable but not explosive. While A# products have much greater velocities and energy when they burn and can be explosive.

Here is a study:

http://ec.europa.eu/environment/air/mac2003/pdf/hill.pdf

Here is a individual who converted several cars:

http://home.earthlink.net/~bob1.gardner/id21.html