"vapour consuming type appliance" ?

I believe a "vapour consuming type appliance" is anything that needs to be fed with propane in the vapour (i.e. gaseous) phase - this will apply to all torch-type burners (AFAIK), and probably covers propane powered refrigerators as well.

Thanks, that makes sense. "Vapour consuming" means fueled by the vapour, not to a ventilation/safety appliance.

The point is to never try to use the tank unless it's standing vertically.

There are special tanks, equipped with siphon tubes, for delivery of liquid propane, if required.

And remember that the gas will find and pool in the lowest level of the building. The gas has even been known to travel from one building to another before finding an ignition source and blowing the hell out of half a city block.

Very much to the point.

I was recently advised by a 'professional consultant' to buy the simple plumber's torch rig with no hose, and then was physically instructed to balance the propane cannister horizontally on one arm and tip it downwards toward the metal being 'soldered'. I was led to believe that this was a safe and normal practice. The flame, in these conditions, flares up uncontrollably and unpredictably - a difficulty the consultant blamed on my lack of skill and insufficient practice, never mentioning that a hose is standard equipment for this work, for safety and for efficacy.

Just doing my follow-up on the paperwork here, and wanted to be sure I understood the hazards described in the safety documents.

I have the same problem with mine. I seem to recall that some older models didn't have this problem, but they had to be hot, or they would go out, too.

I think that if you are working with delicate things a hose between tank and burner would be the ticket. It'd be lighter too.

It might be interesting to note the LEL(lower explosive limit) and UEL of propane/air is 2.1 and 10.1%.

Cheers.

I'm curious about how to interpret LEL and UEL values. Does that mean (LEL) that propane released by accident will not explode if the volume of propane is less than 2.1% of the air? Can't be I guess, or the UEL wouldn't make sense?

The problem with horizontal use of the torch cannister, is that liquid propane (instead of vapour) comes in contact with the relief valve and is either spewed out with the vapour (causing flare up) or causes the valve to close (causing the flame to go out).

Bernzomatic says a hand-held cannister should never be tipped more than 60 degrees.

I just read that liquid propane, when released, expands to 270 X its volume. It's a much bigger hazard as a spill, than accidental vapour release.

LEL means that below 2.1% concentration there's not enough propane to support combustion and UEL means that above 10.1% there's not enough O₂ to support combustion.

Spills are uncommon. Usually the gas finds an ignition source and you have a BLEVE.

Boiling Liquid, Expanding Vapor Explosion. Like this:

WOw. amaazing video.

Just to put the LEL risk in perspective, say I have a 400g cannister of propane, in a room 10 x 12 feet X 8 1/2 foot ceilings. That's 1020 cubic feet. Gas - it's all about volumes isn't it? The cannister is similar to a quart size, a little bigger. It's just short of a foot long and 3 inches around. I would estimate it would take at least four cannisters to get close to a cubic foot. If the propane in a full cannister is assumed to be 80% liquid by volume, then maybe five cannisters would contain a cubic foot of liquid propane.

The liquid propane expands to 270 X its volume. By my reckoning a single small cannister, if it leaked all its contents, would amount to around 7.5% of the air volume in the room. That's pretty impressive, for such a little thing. If not for the compression, the cannister full if dispersed into the room would not support combustion, if I understand you correctly about the LEL.

I didn't check your math, but you get the idea.

But, there's more. Let's assume your room doesn't have any air leaks. So no convection movement, just those atoms whipping around in the air/propane molecules.

Now you've got to deal with stratification. Remember, propane is heavier than air. So, somewhere in this mixture you've got a fuel air blend that is flammable.

You know, this stuff gives me a headache. I have to quit thinking for a while. Just leave the window open a little.

Little trivia: water expands 1700 times when it converts to steam.

Is the sun over the yards yet?

Stratification, very important point, thanks for the reminder. No leak is without a risk of combustion.

The other thing about ventilation, when burning the torch, is that carbon monoxide is produced by propane combustion if there's insufficient air.

So if I were using the torch in a closed room theoretically (not that I would do that! hello sun!) then at some point (say, approaching the UEL value) carbon monoxide becomes the product instead of CO2 because of air being replaced by CO2.

On the stratification theme, I looked and found out CO2 is heavier than air, so it will sink as it's produced. CO is around 3% lighter than air, so it will tend to rise. I guess I'll be putting the CO detector around face height near the bench.

I really appreciate you helping me think about gas, Lyn. Thank you. This way, nothing will go wrong because of my ignorance. And on the day that anything does go wrong, I won't do something ignorant. Even if my head hurts now.

I think I'd better go expand some water 1700 times or less and infuse caffeine.

Thanks for bringing this up! Although the manual in your link did not (that I saw) specifically refer to the small cylinders commonly used for camp stoves or soldering torches, pretty much everything still applies. I have to admit that I've never thought about the liquid/vapor issue while soldering, and I'm sure I have used one on its side and even upside-down on some occasions. Now I understand the reason for the changes in the flame...

The caution specific to hand-held torches is on the Bernzomatic page:

"Caution

DO NOT use torch with the fuel cylinder tipped more than 60 degrees from its upright position as this may cause torch to flare."

I guess it's inevitable that a hand held torch will be tilted at some time during use. Even at 60 degrees, or with rough handling, liquid propane can contact the valve, and they give these instructions if you have to tilt sideways:

"Warning

1. The propane cylinder contains gaseous and liquid propane. If the torch is moved rapidly, tilted too far to the side or upside down, the liquid can enter the valve and cause the flame to flare or extinguish. To prevent this, adjust the torch to a ¼" long inner flame and let the torch warm-up for 5 minutes prior to such movement, and then slowly re-adjust as necessary once the torch is in the desired operating position."

There are directions, but not explanations, in the fine print on the cannister itself. "Use upright to prevent flareups or flashes" etc.

It's a credit to the construction and design of the cannisters and valves that more accidents don't happen. When liquid propane expands, the reaction is strongly endothermic. Contact with skin can cause frostbite, and of course, if splashed in the eyes it can cause permanent damage. Better safe than sorry!

Cheers.

"adjust the torch to a ¼" long inner flame and let the torch warm-up for 5 minutes prior to such movement, and then slowly re-adjust as necessary once the torch is in the desired operating position."

Thanks. That indicates that what I have done in the past was indeed acceptable.

"When liquid propane expands, the reaction is strongly endothermic. Indeed when any liquid is allowed to expand from a pressurized liquid to an unpressurized vapor, the vapor will cool according to the standard gas law, but that is not a (chemical) reaction.

not a (chemical) reaction.. right you are. not sure what term applies instead of reaction. energy is consumed in the process of expansion. (that energy, of course, was put there when the gas was compressed to a liquid form).

"adjust the torch to a ¼" long inner flame and let the torch warm-up for 5 minutes prior to such movement, and then slowly re-adjust as necessary once the torch is in the desired operating position."

Can you explain the physical reason why this approach works, other than, you burn the torch for five minutes and use up some fuel, so that the liquid propane does not reach the valve when you carefully try again? How does warming up affect the ratio of liquid to gas?

It still seems to me that you can't expect anything but flakey operation and a hazard if the cannister is full enough for liquid to contact the valve in the tilted position.

The only way you can hold the cannister horizontal and not have a problem, is if the cannister is less than half full IMO.

Once the Torch nozzle is up to temperature, it will vaporize the small amount of liquid that gets past the valve, as fast as it comes through the valve, so only vapor reaches the ignition location. Remember that the flow was previously set while the tank was upright, and only vapor reached the valve. The much higher viscosity of the liquid will limit the flow past the valve when there is liquid instead of vapor reaching the valve.

Agree. Flame may splutter a bit, but should be fairly steady as long as it's only a brief splash or tipping-up event.

Must be referring to gas stoves and other domestic/ commercial burner based applications. If the cylinder is full the outlet may be below the liquid level and liquid fuel may flow out. Certainly hazardous.

You really do not want to allow liquid propane to flow to a "vapour consuming type appliance".

For example, if you light a hand-held propane torch and then tilt it downwards, the torch may gush a large flame or choke on the liquid and extinguish, or both.

So if your appliance is a "V.C.T.A.", keep the cannister vertical.