Acetylene generators - how dangerous?

An inverter tig/DCstick welder might be the answer for you.

all kidding aside (i remember going through welding school, which had 'em) and thinking i had to get one of those, along with a liquid O² tank: my puny B tank was causing the same issues you describe....

the regulations/hastles/space requirements/etc. would be prohibitive

hey, now: (found on eBay):

Well just yesterday I happend upon a body work shop with one of these. A small thing, some 70 centimeters tall and 50 centimeters diameter. I've seen larger, about 5 feet tall.

mongke

Way outside my budget by now :(

just in case, 50 cm are 1 1/4 ft aprox; 70 cm are 2 1/4 ft approx I was raised in metric, sorry :)

if I can find the shop again (I was looking for an address and passed it on the run) I might take a picture.

mongke

I've never seen or heard of modern day, compact acy. generaters so I would be interested in who is making them and what they cost, just for curiosity sake. What part of the world are you in? I would also like to be present when you tell your homeowner insurance agent that you keep an acytelene generator in your garage ! Have you checked the price on upgrading your acy. bottle to one of the big ones? And the better price you get on refills? That might be the way to go. The larger the bottle, the cheaper the gas.

JTMcC.

Hmmm.. *puts on chemistry hat*

Lesse, 1mol of gas is 1 (avagadro's number) of molecules in... uh... cubic meter? hmm.. I'll just grab some numbers... Given STP, air is.. 29g/mol and 1.2kg/m^3. Propylene is (by memory) C3H6, so it is 3*12+6*1 = 36+6 = 42g/mol. So 1 cubic meter will weigh 1.2*42/29 =

1.75kg/m^3, or uh.. 1.75 * 2.2(lbs/kg) / 35.3(ft^3/m^3) = .11 pounds per cubic foot. So 5lbs. is about 46 cubic feet?

Tim

-- "That's for the courts to decide." - Homer Simpson Website @

For gasses, the molar volume is 22.414 L at STP.

hmm.. I'll just grab some numbers...

Nope, seems impossibly low. I've been using this same 5 Lb tank for at least

5 YEARS, without using it up. I've used up something like 200 Cu. Ft. of Oxygen so far. I don't know what fuel/Oxygen ratio is used for it, but it still seems like there's got to be WAY more than 46 Cu. Ft. of gas in a 5 Lb tank of liquid.

So, 42 g/mol, and 5 Lbs is 2.27 Kg or 2272 g. So, 2272 gm is 54 mol. And, at STP the gas would occupy 54 * 22.414 L =

1210 L. Ahh, 42 Cu Ft. Back in a circle. But, it can't be right. Well, consulting the data at they say the specific vol is 9.4 Cu Ft/Lb, so with that I get 47 Cu Ft for 5 Lbs. Humpf!

Well, either that tank is really a 25 Lb tank, and I'm badly misremembering, or the mixture is such that the fuel gas flow is vastly less than the Oxygen flow.

ANYWAY, after all that blather, I have found it to work quite well for brazing, at least. It certainly gets hot enough to weld with, as I have accidently burned steel when I got carried away when brazing. It would start spitting sparks like from a grinding wheel.

Jon

Really ? Got any pictures. I'm surprised that they still have one and _amazed_ that any remained in service much beyond WW2. The running costs must be steep.

They're much safer - often to the level of being process-inherently safe. A simple way is to make their gas receiver a water-sealed floating gas-holder (just like a big gasworks). The pressure remains constant because the reservoir can float up and down to change volume. If it over-fills and then over-pressures itself, it just blows out the water seal.

Another way is to make the water-drip feed under low pressure. No more water can get in there until the pressure drops. This is how car lamps and miner's cap lamps used to work. BTW - you can stil buy acetylene generators and supplies from a caving shop.

Monthly ? That's either a tiny cylinder, or you're commercial.

I have no idea what my acetylene costs me. I use far more oxygen, and renting the bottles costs more than the gas does, at any sort of "UK hobbyist" rates.

-- Die Gotterspammerung - Junkmail of the Gods

You must really consume a heap of acetylene in your home shop then to want to spend the big $$ and go through the paian it is to maintain a generator system. Why not just get a larger cylinder or add an additional cylinder or two. I personally don;t think a acetylene genmerator is cut out to be used in a home shop environment no matter how much gas you may consume. Visit my website:

expressed are those of my wifes, I had no input whatsoever. Remove "nospam" from email addy.

About US $1 per kg of carbide plus tap water. What would be the typical acetylene production rate per kg of carbide?

This is good info. I've still not seen the inside of one. Got any schematics for this?

Granted I'm a novice but 3kg went away in just 2 months, and I was not welding a trailer or so. I had expected it to last at least 6 months. That plus the rent cost is hard on my scrawny wallet.

Mongke

(snipped)

If it's spitting sparks like from a grinding wheel I would say that the flame has excess Oxygen to gas mix (no good for welding). The problem with MAP type gases is that they do not produce high enough temperatures for welding without turning the Oxy up and making the flame Oxy rich, this then uses the Oxy to burn the metal as fuel to create more heat. Sure you can stick metal together with it but it really is literally burning it together rather than welding it properly. Well that's what I found when I used to use it.

I suggest you try getting your Acetylene bottles (full size) in future from the local scrap yard. They most often can lose a bottle (in your favour), then later as you use it, change empty for full, at a cut price exchange with no bottle rental charge. This also works for obtaining Argoshield for Migs, from the scrap yard.

well the idea of putting together a miniature one (way scaled down) for limited 7# output (i'm thinking the problems really start to kick in in the compression to 250# phase) is intriguing, esp. in view of the $1/kg for raw material... .

NO! NO! NO!

I have no personal experience, but as I understand it you should never drip the water onto the carbide when generating more acetylene then a miners lamp generates. The process is exothermic and if you don't have a substancial amount of water to keep things cool, the temperature gets too high. So for welding acetylene generators always feed the carbide into water.

When I was caving, we bought carbide at the welding supply. It was two or three dollars for a small can at Hopper Hardware and about $15 for a small drum at the welding supply.

Dan

Maybe you have a leak. If it's just a new set of hoses, that this is a cheap easy fix.

BS! Propane (and air!) gets hot enough to weld easily.. I've forge welded before... oh wait.. that's not actual melting, nor is it out in the open like most welding. ;)

To Jon: thanks for verifying my numbers ;) Hmm.. can calculate flow from oxy I think. Let's see, C3H6 + nO2 = 3CO2 + 3H20, so n = 4.5. Nine molecules of O2 for every two of propylene. I think that does indeed mean O has to be 4 1/2 times the flow rate, so out of 200 ft^3 that's almost the tank (44ft^3)... a quick guess but seems like your tank should be pretty low... if it ain't then it's probably 10 or 20lbs. Is it about the size of a standard propane tank? (I suspect propane and propylene have a similar liquid density.)

Tim

-- "That's for the courts to decide." - Homer Simpson Website @