Thread: oxy acetalyne hose fittings

Originally Posted by fittermachinist

hey guys!
just woundering if anyone knows of a video on the internet of how to change the fittings on a oxygen acetayne hose?
thanks
dave

Whatever instructions you may find, do NOT use the proven old match method for the leak testing

Jokes aside, if you need to ask for a video, better buy a new hose with fittings already attached and leak tested. If old or worn, please toss and buy new. Hoses do not last forever. The cost of a new hose is pocket change compared to the hire of gas cylinders etc over 5 or 10 years..... or a new home and family if you burn down what you have now. Oxygen and Acetylene are both unforgiving and tricky to handle gases. It is not like fixing an Argon hose for the TIG welder, playing with oxygen and Acetylene can be seriously dangerous. Chris

Well I will tell you what I did... People can burn me at the stake if they want...

My oxygen hose was perished and leaking only on the ends, they were crimp on fittings...

So I cut off the fitting, cut off the brass crimp section leaving just the barb.... Put the barb on the hose and nipped it up with a wire.. It only has to hold 40psi or so... And it is only oxygen...

Now the safety fanatics can tell me how I made baby jesus cry and have managed to kill five blue whales from doing it...

OK maybe the last bit was not warranted, but just been reading up on government OHS laws and what is a high risk, apparently I should have been killed about 20 times over the last decade or so...

The fittings are crimped with a dedicated tool, for a one off job it is not worth the outlay, your local welding supply will do it although these days you may as well just buy a new set of hoses already fitted

With the older style fittings, you can fit new hoses , I did it back in the 1970's to a old set I had which would be a antique today . . To test for leaks, I held the whole torch under water and looked for bubbles , never had any problem with it . Don't know about the modern setups, but if they are crimped, then yes, go to a reputable business and have them to the job .

Mike

BTW I've never seen a oxy / ac setup that runs at 40 psi - the tip number is usually the psi rating e.g., if your using a #6 tip for general work, then you set the regulators for 6 psi . that's how I was taught at TAFE

Hey There,

From my experiences over the past few (15) years, you are better off getting new hoses, because when they start to go they just keep going, you repair them today and then you do it again on Friday and then next Wednesday and then ...............and then they are too short to do the job, and the ammount of down time out weighs the cost of the hoses by about 75%
Just get a new set and count your blessings.

HazzaB

G'Day Dave, the way I have done it with the older re-usable fittings, as distinct from the crimped ones used on pre assembled hoses, was to firstly remove both hoses from the mixer handle, to which the cutting attachment or welding tip adaptor screws. The hose to be repaired has any damaged ends cut off, (with a nice clean straight cut) and a lead for the barb, cut around the bore of the hose, (like a countersink would trim it.) The brass ferrule is then fitted over the end of the hose and is pushed fully home. The barb should be re attached to the mixer handle, and some water or even saliva can be applied to the countersunk area of the hose, and also on the barb as a lubricant but never any oil or petrolium product - they could explode. The hose is held by the ferrule with a spanner or gently nipped up in a vice, and the barb is screwed in, using the mixer handle as a tool to hold it. These threads on both oxy and acetylene hoses are conventional right hand threads on the tapered barb, but acetylene has left hand threads on the section which screws to the mixer handle. If you have had to cut more than an inch or two from one hose, you may have to cut a similar amount from the other hose in order to avoid having a mismatch in hose lengths, but otherwise you are good to go once you have reconnected the hoses properly, and checked for leaks. Soapy water is excellent for locating leaks, just brush over the new joints, and perhaps the old ones as well, and any leaks will show a stream of bubbles. Acetylene or LPG both smell strongly, and you would be unlikely not to detect any leak with your nose, but oxygen and shield gasses are odorless, can be dangerous in confined spaces and way too expensive to waste. Even if the damaged hose was at the regulator end, I would still use the mixer handle to screw in the barb to the hose and ferrule, and would disconnect the hoses as necessary to perform that operation, and then reconnect everything as it should be to test. HTH
Regards,
Rob
PS. Too slow again, mike said it all in half the space and time, RG.

Originally Posted by morrisman

BTW I've never seen a oxy / ac setup that runs at 40 psi - the tip number is usually the psi rating e.g., if your using a #6 tip for general work, then you set the regulators for 6 psi . that's how I was taught at TAFE

Just for information, oxy acetylene pressures can be up around the 80PSI (550 Kpa) mark when Gouging and the like. 30PSI (200Kpa) would be a starting point when cutting. These figures are for the oxygen regulator only.

NEVER set acetylene above 15PSI (100Kpa) due to it's volatility at pressures above this.

Of course, when assembling your hoses, do not use oil or grease as a lubricant.

Acetylene is one the most volatile gases on the planet.
It should be used by responsible and trained operators.

When it is not used so, stuff like below can happen.

Originally Posted by Grahame Collins

When it is not used so, stuff like below can happen.

Where was that incident?

According to what I can find on the 'net, Melbourne.
(Remote Detonates Explosion In Plumbers Van - Raw Fish)

Michael

Originally Posted by Karl Robbers;1613538[U

NEVER[/U] set acetylene above 15PSI (100Kpa) due to it's volatility at pressures above this.
Of course, when assembling your hoses, do not use oil or grease as a lubricant.

Its not the volatility. Acetylene becomes unstable at pressures above about 1 bar (or about 15psi). Unstable means it becomes first shock sensitive, and can even explode spontaneously at higher pressures. That is why in the cylinder it is not stored as a pressurised gas, but it is instead dissolved in a liquid (either Acetone or Dimethylformamide). Think of mineral water, when you crack the bottle CO2 bubbles form in the water and rise to the surface. Same in an acetylene cylinder. To avoid the liquid spitting out along with the gas, the cylinder is filled almost to the top with a porous stone-like filler. It is at the very top of this filler that the acetylene gas bubbles out of the Acetone. This is why the cylinder must not be laid to its side. This is why if it was on its side, it should be stored upright for at least as long as it was on its side to allow the liqid to settle withing the porous filler. Else Acetone or DMF gets carried into the regulator, where it damages the regulator and torch seals and attacks the gas hoses from inside and worst case spits out from the torch as a burning liquid onto your job.

Acetylene can also form Copper Acetylyde in the presence of pure Copper (not brass, it has to be Copper of above about 70% purity). Copper Acetylide is explosive. So better do not use copper pipe to repair a perished gas hose. Copper(I) acetylide - Wikipedia, the free encyclopedia

Interesting if you can visit a gas factory. I recently had the chance to visit Supagas in Dandenong. They produce their own Acetylene with Carbide (calcium Carbide, not the insert tooloing ). Remember the old lamps used by cars and bikes, you fillet the bottom container with carbide chunks, the top container with water, then with a needle vale the water is let to drop onto the carbide where a reaction takes place releasing the Acetylene gas wit the distinctive smell. Then you light it at the ceramic burner, resulting in a bright yellow/white flame. That was before cars had electric light. Carbide lamp - Wikipedia, the free encyclopedia From time to time such a carbide lantern did blow up.... mine did when I was playing with it as a kid because of perished rubber seals. Anyway, back to the gas factory visit, the Acetylene is then slowly fed at low pressure to the cylinders where it dissolves in the acetone. That generates heat, and therefore the whole filling procedure happens under a water jet curtain to keep the cylinders cool.

Please do not repair the gas hoses unless you know exactly what you are doing. They perish with age and have a finite life. Just buy a new set of hoses, they are cheap enough at somewhere between $50 and 100 for a pair. Not worth the risk, and nowdays not worth your time. Chris

Reported in the local media a few years ago - A chap had a couple of fingers blown off by a acetylene bomb . A member of a military re-enactment group at Geelong picked up a contailer filled with acetylene , it exploded . The acetylene " bombs " were used to add realism to a display of WW2 era equipment . Some people have too much spare time , Mike

Originally Posted by cba_melbourne

Anyway, back to the gas factory visit, the Acetylene is then slowly fed at low pressure to the cylinders where it dissolves in the acetone. That generates heat, and therefore the whole filling procedure happens under a water jet curtain to keep the cylinders cool.

Hi Chris,
Nice post but are you sure the water was used for filling Acetylene cylinders?
I would have thought it would be only needn't on the high pressure cylinders(but what would I know. but then the gas coming out of the liquid cools it so I guess the gas going back in must heat it.........)

Yes plumbers have been blowing themselves up for years(I guess since vans replaced utes). Its been illegal to carry combustible gas cylinders inside an enclosed vehicle for many years now(unless in an approved vented cabinet).

Stuart

Be extra careful with oxygen cylinders as well. Saw a video with some very scary stuff that can happen with them, years ago. If one gets knocked over and breaks off the valve it will become a missile.

Nev