Acetylene generators - how dangerous?

(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.
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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 @ http://webpages.charter.net/dawill/tmoranwms
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Tim Williams wrote:

Yeah, it is about half the size of a propane tank. It looks like it would hold maybe 2 gallons or so. It has to be more than 5 Lbs. Anyway, for what I do with it, the Propylene works very well.
I won't store Acetylene indoors, it is just too dangerous. The Propylene is dangerous, too, but there are about 3 more ways Acetylene can make a big boom.
Jon
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wrote:

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
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On Sat, 31 Jan 2004 14:16:49 +0000, Andy Dingley wrote:

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.
> I have no idea what my acetylene costs me. I use far more oxygen, and

Mongke
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The problem with this is, you can not develop any higher pressure than the water column over the carbide container. Which I am sure is lower than the pressure a torch would use.
From this I would guess that the commercial generators must use some trick to allow higher output pressure.
Jim
================================================= please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com =================================================
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Maybe you have a leak. If it's just a new set of hoses, that this is a cheap easy fix.
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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

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On 31 Jan 2004 11:10:14 -0800, snipped-for-privacy@krl.org (Dan Caster) wrote:

That's why I was talking about miner's lamps.
There are three ways to generate acetylene; water drippers, carbide feeders and sinkers.
Water drippers are the little ones. Carbide feeders jam with damp lime slurry. All the welding-scale producers (after the first few years) used rising water, held back by the gas pressure. Welding acetylene needs to be purer than lighting acetylene. As hot carbide gives an impure product, this is the real constraint on over-heating, not safety.
A typical low-pressure welding producer from the '20s was a fairly large plant that fed several welders. Each would have their own oxygen cylinder, but the acetylene plant was centralised and fed a manifold pipe around the workshop. Tappings of the manifold would be by a hydraulic anti-backflow valve, similar to todays check valves, to avoid oxygen back-feeding into the pipe. If such a plant ever did explode (and a few did) it was almost always by getting oxygen into the gas-holder.
The gas producer was a steel cylinder holding 40 lbs of carbide and at least 40 gallons of water (pound per gallon was the usual rate). This ran for a ten hour shift and gave 18 cu ft. of gas per hour, at a pressure of about 8" of water. This might keep a production-line welder supplied on their own, but was typically an intermittent supply to a number of general fitter-welders. Torch-hanger economiser valves were an early invention, shutting the torch off automatically when not in use.
Carbide-gas is dirty and not suitable for welding. It needs mechanical filtering to remove lime dust (the worst contaminant) and chemical scrubbing to take out ammonia or H2S. Usually it was filtered first, stored in a water-sealed expandable gas holder, then chemically scrubbed. The chemical scrubber in early days was either chromic acid or cuprous chloride dissolved in hydrochloric acid. These were consumed and required replacement (a pound of scrubber to 100 cu ft of gas) Later scrubbers were a catalyst and adsorber that could be regenerated by swapping between two scrubber elements.
The gas holder rose and fell with gas demand. It was usually coupled to the water valve on the generator.
-- "When men die, their Maker may reward them for their efforts by allowing them to live again as male dogs. Thus freed from inhibition, they can spend a cheerful existence doing all those things they really wanted to do when they were men."
Paneb, Foreman mason in the Valley of the Kings, circa 1190BC
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wrote:

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: http://www.frugalmachinist.com Opinions expressed are those of my wifes, I had no input whatsoever. Remove "nospam" from email addy.
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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... .
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My father used an acetylene generator in his (commercial) shop. This thing was made in the 20s or 30s, so they'd never heard of OSHA, EPA, or Homeland Security. The acetylene generator looked a lot like a horizontal 20 gallon air compressor, sans motor.
The tank was filled with water. The "pump" was actually a hopper and clockwork sort of mechanism which released grains of carbide into the tank in response to the fall of pressure in the tank.
There was some sort of interlocked double doored air lock like thing between the hopper and the tank which was operated by the wind up mechanism. I recall hearing it "ticking" as it was working.
As I remember, the tank pressure was low, no more than 15 PSI, regulated down to 5 PSI for the torch. The whole end of the tank would unscrew, to let you get inside with a rake to clean out the spent carbide residue. I don't recall any blowout plugs per se.
It worked fairly well if you were using it all the time. But if you let it sit up for a while the mechanism would get balky, and it wouldn't drop carbide. I remember my father cussing and tapping on it to get it to drop carbide.
By the late 50s he quit using it, and just bought bottles of acetylene from the same place he was getting his bottles of oxygen.
Gary
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Gary Coffman wrote: .(clip) The whole end of the tank would unscrew, to let you get inside with a rake to clean out the spent carbide residue (clip) ^^^^^^^^^^^ When I was a kid, I mounted a miner's lamp on my bicycle handebars. One of the things I remember is that cleaning the thing involved disposing of a watery-pasty slurry which stank to high heaven. I imagine the job of raking out the spent carbide residue from your father's tank was really unpleasant. That alone would make me want to avoid an acetylene generator.
Off topic a little further, we just got a machine which generates breathing oxygen for my wife (she has heart trouble.) It just plugs into a 120v outlet, and delivers breathing oxygen to one of those plastic nose-hoses. How do it work?
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aren't you refering to an O concentrater? not really the same as being hooked up to a bottle: through a process of vacuum, solonoid/switches/pumps and an activated filter, it delivers a stream of enriched(?)20%(?)mixture...
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By clever use of a filter media which lets the oxygen through and slows down the nitrogen. It's not a generator, its a concentrator. However, a properly set up concentrator can produce essentially pure oxygen. Might not be pure enough for good results cutting, though.
Here's a web page descibing it (unfortunately, the web is now also clogged with spamsites trying to sell these to people who don't need them...so tracking down actual infomration has become needle-in-haystack work).
http://www.ranamedical.com/hospitalconcenop.html
I made a slight effort to see if there were small industrial scale machines available for replacing cylinders, and could not find any amid the spamming of medical devices.
--
Cats, Coffee, Chocolate...vices to live by

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wrote:

Yeah, it stank to high heaven. (Guess whose job it was to clean out the generator.)

It pumps air through permeable membranes which pass oxygen slightly more easily than nitrogen. After passing through several layers of membrane, the amount of oxygen in the output gas is enriched the desired amount. Won't work for welding though. Welding and cutting oxygen needs to be better than 98% pure. The concentrators don't get it that high.
Industrial oxygen preparation is done by fractional distillation of liquid air. Nitrogen boils at -196 C while oxygen boils at -183 C. By controlling temperature, they let the nitrogen boil off, leaving the liquid oxygen behind.
Gary
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Mongke:
I was taking a jewellery course a couple of year ago I advised my insurer in writing that I was going to be taking my small acetyene tank in the house and they didn't increase my rate or ask me not to do it. I have a jeweler friend who has a propane tank in his small store just below a number of apartments and he hasn't had any problems getting insurance and his landlords insurer has never shown any concern.
However if your running a business no matter how small and you don't carry business insurance, your house policy isn't worth the paper it's written on, that's a fact not an opinion. From the amount of gas your using it sure sound like a money making operation to me. My son is an adjuster and some of the horror stories he tells me would scare the crap out of you. The fact that you have dangerous gases in the house isn't the problem. The problem is you haven't supplied your insurer with the information they need to calculate their risk, it's that simple. We live in a post 9/11 world and insurers are really playing hardball.
Every insurance company has different rules so in my opinion advise yours in writing and let the chips fall where they may.
Jimbo
wrote:

of
raking
unpleasant.
breathing
membrane,
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First thing is that you'll need an injector-style torch to handle the low pressure out of the generator. I've seen these in both Smith's and Victor's catalogs, I've never seen one on the shelf. These have different internals than what the standard torches do. Next, you'll have to find some way of disposing of the residue which is mostly slaked lime with some impurities. And it stinks. There was a welding supply shop in my home town that made their own acetylene, filled tanks from three states around. They had tons of white sludge laying around, it wasn't really suited to agricultural application because of the impurities in it. The city would get on them about it, the piles would disappear and then, soon after, there'd be more. Never did find out where it went. You might have a problem finding small quantites of bulk carbide, there's the 10 lb tins for miner's lamps and then there's the 100 kg. drums, not much in between. I'm not sure it would be a paying business for occasional use. Once wet, carbide evolves gas continuously, there's no easy "off" switch or valve with it.
You might want to look into oxy-propane or oxy-propylene for your brazing needs. Either would be cheaper than using acetylene, if you're really using that much. And if you are, you might want to look into getting a larger bottle, the cost/cu.ft. goes way down on the larger bottles. Around here, the refill price is about the same if it's an MC or an 80 cu.ft. tank, it's mostly the handling and overhead that costs the money, the gas itself is pretty cheap.
Stan
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On 2 Feb 2004 13:18:37 -0800, snipped-for-privacy@americanisp.net (Stan Schaefer) wrote:

That's not necessarily so. My father's generator produced about 10 PSI. That was regulated down to 5 PSI for use with a normal Harris torch.

Just heat it up (some residual acetylene will burn off, supplying most of the heat once you get it started). That'll turn it into quick lime. I used to peddle that to the neighbors for use in their outhouses to *control* stink.

The latter is serious truth. Lease the biggest bottles your supplier carries. That'll save tons of money over time.
Gary
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Some other posters have hinted at this, but switching processes might be the best best. Acetylene is probably not the most cost-effective process available. One poster suggested MAPP gas, even oxy-propane might work for brazing, surely much cheaper than acetylene. A MIG welder is a popular option for steel, or TIG for various metals. Talk to the local shops about what you do and what other options there are.
Richard
mongke wrote:

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