Go BottomPressure for Oxy Acl torches
 | 1st JD
Join Date: Posts: 1 
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2003-02-20 49663
I just got a new set of torches from my loving wife as a gift. Always had a welder but really needed a set of cutting torches (well, kinda needed them). I put them together but I'm not sure of the pressures to run. The very small booklet that came with it is not very clear. Any help would be apprec. Thanks
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| woozee
Join Date: Dec 2003 Posts: 3 northwest Alabama
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2004-01-06 73315
try 7 on the gas and 48 on the air. ....
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 | harvey
Join Date: Sep 2000 Posts: 1550 Moravia, NY 
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2004-01-07 73319
There are lots of pressures to use. BUT it depends on the size of your tip which should correspend to the thickness of metal you are cutting.
Of course then it depends on what gas you are using.
R-U more confused now?
Give us the brand torch, gas type and the tip # and we can help you better.
Harvey ....
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 | Art White
Join Date: Jan 2000 Posts: 6898 Waterville New York 
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2004-01-07 73371
woozee, I wouldn't be running the oxygen that high unless I was cutting inch thick steel. The max I use is about 25 for cutting. Most welding with gas I'm around ten lbs on both. Might be a good time to take an evening coarse to learn what I should remember but can't! ....
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| Lenarguy
Join Date: Dec 2003 Posts: 20 Mercer, PA
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2004-01-07 73389
If you are using Acetylene, safe pressures are 5lbs Acet. and 35 lb Oxygen. This is practical for metals around 1/8 - 1/4" Please be very careful with the Acetylene! Never let the working pressure gauge get above, (or close to), 15 lbs. There should be a red sweep line on the gauge. If would ever get that high it could come out in liquid form and ignite when it mixes with oxygen in the air. Also, keep the cylinders secured in an upright position, periodally check for leaks with soapy water, (including the hoses), I recommend that when done using to shut the tank valves off, bleed the system, and back-off the regulator screws. Please us caution when operating the cutting outfit, it is potentially very dangerous!!
Good luck and happy cutting! ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2004-01-08 73423
When I bought my gas kit a long time ago--and also a long time since I've used it a booklet came with it that gave pressures pre tip size--35 lbs. is what I remember for the cutting tip. I also remember vapourizing thin section material at that pressure. Boy, you hit sheet metal with the O2 at 35 lbs. and wide swaths just disappear. I used to back off the pressure a bit but buying a smaller tip would have been better. Pressures that are too low don't work well either. One of my larger welding tips worked just fine for cutting sheet for when I was too lazy to use snips--bunch of slag to knock off so maybe it was just dumb rather than lazy.
If a booklet didn't come with the kit, I also bought a basic 'how to' book at the welding supply shop that had the pressure charts. I think they are pretty standard and probably are on the web. ....
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 | AC5ZO
Join Date: Jul 2003 Posts: 928 Rio Rancho, NM 87144 
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2004-01-08 73438
Oxy Ac welding can be dangerous. For welding, you want to have the oxygen and acetylene pressure at the same low level. The reason for this is that if you plug your welding tip, the oxygen will not force its way into the acetylene hose due to significantly higher pressure. You will not know that this happened until you unplug the tip and try to relight the torch with one hose filled with mixed acetylene and O2. You can get a back flash and a fire real quickly.
There are reverse flow check valves that can prevent this, but keeping the O2 and AC pressure at the same level is good practice for welding. For cutting, you use a lot more oxygen than AC for burning the steel. For most work under an inch I use 25 psi for O2 with my particular cutting torch and 5-7 psi for the acetylene.
Acetylene is not chemically stable. It will spontaneously and rapidly decompose at pressures above the safe pressure of 15 psi. Never set an Acetylene regulator above 15 psi for any reason. Acetylene is stored in your cylinders as a gas disolved in liquid Acetone (like CO2 is disolved in club soda). The liquid referred to in a prior post is really the acetone and not liquid acetylene. Because of the acetone, you must use acetylene cylinders in the vertical position and there is also a peak delivery rate.
Acetylene can only bubble out of the acetone solvent at a slow rate. If you try to use a "Rosebud" or other high gas consumption torch tip with too small an acetylene cylinder, it will "foam the acetylene" and acetone will be carried out of the cylinder. This is like shaking up a warm club soda and opening it. The CO2 in that case will come out of solution faster than you want it to. Check your owners manual for proper tank and tip sizes. ....
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 | AV8R
Join Date: Oct 2003 Posts: 882 North Central Wisconsin
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2004-01-08 73469
Excellent analogy AC5ZO! Couldn't have said it better myself. Welding How-To books are much cheaper than a fire or injury from improperly adjusted regulators.
One more piese of advise: I like to have my regulators professionally cleaned and inspected every year. Lack of use is harder on them than constant use. One blown regulator will teach many lessons. ....
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 | jasonsewell
Join Date: Jan 2004 Posts: 34 Plainville, CT USA
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2004-01-08 73495
I must add that I cut a lot of steel 1/4 to 3/4 inches thick and I use 10lbs gas to 40 lbs air. I have never had to adjust this mix for anything that falls into this range. 5 and 30 works for me for anything lighter than 1/4" ....
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 | blizzard
Join Date: Jul 2003 Posts: 282 Central Maine
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2004-01-09 73513
For 0xy-Acetylene cutting 5-7# fuel and 25-35# oxygen is a pretty common setting for the regulators. You have to control 2 variables here, the preheat flame(s) and the cutting oxygen pressure. The regulators will keep the pressures steady to the torch, but you will have to adjust the preheat flame to the condition of the metal ( and your technique). Too much heat/moving too slow and the edges aren't square and much slag adheres to the bottom of the cut. Too much oxygen and you can blow the preheat out, and definitely waste gas.
Acetylene is really dangerous stuff! I strongly urge you to talk to your welding supplier about MAPP fuel and tips for your outfit. If you do an appreciable amount of gas work, you will save money in the long run.
Have fun with your outfit, and be safe.
....
Link: WeldingInfo
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 | Murf
Join Date: Dec 1999 Posts: 7249 Toronto Area, Ontario, Canada
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2004-01-09 73527
As Blizzard states there are good alternatives to using Acetylene at all.
In the recent edition of Farm Show there is a story about a company which has started making Gasoline/Oxy. systems, these used to be very popular but for a long time were only used by large volume industrial cutters.
We have been using Propane/Oxy. for along time and it works very nicely.
Best of luck. ....
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| AC5ZO
Join Date: Jul 2003 Posts: 928 Rio Rancho, NM 87144
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2004-01-09 73540
I have used MAPP, propane and butane with oxygen before as well as acetylene. I do like MAPP a lot and prefer it to butane or propane. The last gasoline torch I used had a preheater pan that you used to get the torch head hot before it would make a decent flame. Surely that must have improved.
I think that Acetylene has the edge on highest flame temperature, and MAPP is better for overall BTU value. MAPP, propane, and butane are all safer than acetylene in my opinion. I have been using acetylene for over thirty years, however, so I am probably not going to change. ....
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| Mecheng
Join Date: Posts: 1
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2004-01-23 74788
Start as low as you can on pressure and work your way up.
For welding accetylene 3 to 6 psi NEVER EVER GO OVER 15 PSI
Oxygen 10 psi
Cutting
Accetylene 4 to 7 psi, oxygen 20 psi
These setting are for home/hobbyist torches
I doesn't take all that much pressure to get a desirable flame cone. Adjust accetylene to the proper cone length 3/8" to 5/8" in most cases, then slowly add and adjust oxygen to make the cone.
Always use check valves to protect your regulators ....
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| AC5ZO
Join Date: Jul 2003 Posts: 928 Rio Rancho, NM 87144
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2004-01-23 74799
I respectfully disagree about the welding pressure settings. Acetylene and Oxygen should be set at the same low pressure in a welding torch. There are safety reasons for this that I addressed earlier in this thread. I agree with you about the check valves and I also spoke about that.
The check valves would likely keep you from having a problem with flashbacks in the first place, but you should still use equal pressure settings. It is also dangerous to suggest starting as low as you can and working your way up. Using too low a pressure is one of the things that can favor a flashback in the first place. I am sure that you have the experience to know when pressure is too low, but others may not be as experienced. I do agree with you that for most torches and tips that the 3-6 PSI range is a good start but anyone should follow the manufacturers recommendations if they are available. ....
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