Acetylene generators - how dangerous?

Old Carbide Generator.

I have been following the posts in this thread for some time with interest. For many years I have wanted to get my hands on one of these units - as in UK where I come from, the charges for renting acetylene cylinders is really exorbitant, especially for someone who only uses acetylene infrequently. A number of questions have already been answered here. Thanks.

I live in the United Arab Emirates and here there are many small exhaust repair shops still using them. They will not part with them either, so they must be satisfactory. They have been banned in a couple of the other Emirates and this might be a reflection of their dangerous properties or it might be the political power of the acetylene bulk suppliers.

When passing through one of the places where they are banned, I saw recently an old one not in use. After a deal of haggling I got it and brought it home to restore, (it cost me about 90 US$!) It is basically a cylinder of about 16 inches diameter and 3 feet high. It has about 3/4 of the cylinder at the top end double skinned and sealed at the top. It appears to be open into the main cylinder at the bottom and I would think this is where the water goes, so that the level falls away from the carbide which is stored in a basket, raised and lowered by an external lever passing through both skins at the top, when the basket is lowered into the water and gas pressure is raised. There is a line inside to indicate the suitable level.

One thing that worries me a bit is the sealing between the two areas where the shaft of the raising/lowering mechanism passes through. The outside seal is a compressed O ring, but I cannot see what seals the inner skin at this point. The whole of the outer chamber seems to be full of carbide residue that looks like chalk, and I would like suggestions as to what would dissolve it, without dissolving the tank, as it is pretty inaccessible. The challenge of restoring this was as much of a motivation as the use to which it will be put. I have restored a lot of old engines, and am still looking for a high pressure diesel fuel pump for a horizontal twin Witte of about 1950 vintage and about 20 HP. I have a fairly extensive home workshop in UK, but some of the items would bring howls of anguish from the Safety Inspectors! I feel the acetylene generator will join these.

When the gas is generated it comes out of a union at the top and goes through a valve into a water flame trap clinder of a couple of inches thick and about 18 inches long mounted on the side and half full of water. Then it goes to the acetylene pipe and the torch. The top of the main cylinder has a thick mild steel plate that clamps on with a thick rubber gasket to seal it. In this plate is mounted a pressure gauge and a safety valve. The pressure gauge goes up to 60 PSI (in German), but I would not dream of using it at this pressure and, because of the rust on the bottom of the cylinder I am going to have it sand blasted and then decide whether to repair any leaks or replace the bottom domed section. I shall then test it to about 40 PSI with water and set the pressure relief to about 15.

In UK I still have a can of carbide that I bought about 40 years ago, It is still OK in it's sealed tin, but it is freely available here at about a dollar a kilo. I have an oxy-propane set up for bronze welding and cutting but acetylene is better and I want to do sheet steel welding. I would think the trick will be to make it all gas tight, as otherwise I will waste a lot every time I want to use it. When first used, how much gas should be allowed to escape to ensure all the air is purged? Are there any other things to watch out for? Any advice or hints as well as answers to my questions above would be appreciated. I also have taken a few pictures if anyone is interested, I could post them when they are processed.

Thanks in advance. George Bell.

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George Bell
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Recently I found a 1916 copy of "Automobile Welding With The Oxy-Acetylene Flame" which briefly mentions shop-sized acetylene generators, the basics of which are: The generator should have a capacity of 1 gallon of water for each pound of carbide, a means to prevent a pressure greater than 15 psi, automatic control of feed mechanisim, water valve to prevent return of flame into generator, filtering devices to prevent dust or dirt getting into flame, and the generator should not be called on to deliver more than 1 cubic foot of gas per pound of carbide per hour. It also says that if generated too quickly, the gas is heated excessively and when acetylene reaches a critical temperature it ceases to be acetylene and becomes a mixture of gases, giving a flame that is not suited for welding steel. Mike

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MikeM

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