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  #16 (permalink)  
Old 01-27-2008, 08:10 PM
willys36@aol.com's Avatar
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It is not a good idea having a rubber hose pressurized w/ 15psig acetylene though. Like I said that stuff is very unstable as a free gas.

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Old 01-28-2008, 05:01 AM
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Quote:
Originally Posted by willys36@aol.com
It is not a good idea having a rubber hose pressurized w/ 15psig acetylene though. Like I said that stuff is very unstable as a free gas.

15 PSI is pushing the limit but sometimes it is necessary such as with a large cutting tip (Victor no.8), large gouging tip or a heating tip (a "rosebud" not a large welding tip) but these are special situations and a backflow valve should always be used. Also hose size plays a big part in determining how much pressure is required to deliver the flow needed but if over 10 psi (preferably less than that) is required to supply the"normal" size tips, no.5 or smaller Victor or equivalent cutting tip but never a welding tip, then a larger hose may be needed. Attempting to use large equipment with a small hose, a no.6 tip with a 1/4" hose for example, and turning up the pressure to get enough flow is dangerous and even if you don't get hurt the backfiring that is likely to occur will damage your equipment. For auto type work I can see no need for Acetylene pressure to exceed 6 or 7 lbs of pressure and most likely a person will not need that much likewise 20 to 25 PSI on Oxygen should just about cover anything anyone is likely to run into and with a welding torch keep both pressures as low as practical. In any case NEVER!!! exceed 15 PSI on the Acetylene and don't even approach that much unless absolutely necessary, IMO those regulators should be mechanically limited to less than 15 PSI but they are not and they will easily turn up high enough to get you hurt or even killed!

One thing to watch for, and it happens WAY to often, is when a tank runs low and the pressure starts to fall some idiots (and I do mean IDIOTS!) will turn up the regulator in an attempt to get more gas out of the tank! I think most anyone who has worked around welding and cutting has seen people do this very STUPID trick and what happens is they (or someone unsuspecting) will change the tank to a full one and then the regulator pressure can be dangerously high or even rupture the gauge, when switching tanks the regulator should always be turned to zero pressure but most of the time this is not done. It is a good idea to get in the habit of turning the adjustment screw all the way out before switching tanks and then resetting it after the valve has been opened. NEVER EVER turn the adjuster in when the tank is low not even to "check" it (the usual excuse for doing so ) but I have seen this done time after time, people when the damn tank is empty it is EMPTY and you can screw that adjuster all the way in and it will STILL be empty!

Last edited by oldred; 01-28-2008 at 05:32 AM.
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Old 01-28-2008, 09:10 PM
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to Answer one of your "Q's Shad88

When Cutting the sound should be just under a roar.

If you have too much Gas & or Oxy you will here the flame adjust it back until you can't hear it & it will not blow itself out when you hit the Oxy / Cutting lever.

Here is a previous thread on this subject.

Rule # 1 is safety!
that one is most important
Eyes hands feet clothing to start.

Prepare surrounding area making sure that you will not start a fire /explosion while you are burning / welding.
Anything that can burn should not be in the same area.


PLEASE PLEASE PLEASE remove the Regulators when transporting. not only is it a major D.O.T. Violation its just plain stOOpid to do so., but ..Yet ...I see it almost everyday some Bubba Taking his torches for a ride in the back of a pick up & the regs on









.


Too much Oxy when cutting cools the metal too fast & does not let it flow out.

Good Luck & Be safe!


Rob
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Old 08-23-2009, 08:14 PM
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Setting/technique for welding 1/2" steel

I'm trying to weld some 1/2" steel plate to some 1/4" steel tubing and I'm not having just a whole lot if success. I've read the posts that explain the reason that oxy and acet should be set the same and that they don't need to exceed about 5 or 6 psi and I understand. I'm using my biggest tip and I'm turning up the acet until the smoke quits and then matching that with O2. It doesn't seem to be hot enough to phase it.

Should I keep upping the acet and then matching it with O2 until it does the job or try something else? How far should I open up the valves?(on the torch, not the tanks) Can I literally keep going until the torch valves are wide open or is that dangerous(this is all assuming that the tank regulators are set at 5-6psi each.

Is 1/2" just too much to ask of an oxy/acetylene torch?

Last edited by chadmw7; 08-24-2009 at 07:31 AM. Reason: Not showing up as new
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Old 08-24-2009, 09:23 AM
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1/2" is not too much to weld with Oxy/Acetylene but it would require a good deal of skill and the right equipment. First off you are going to need a very large tip but unless you are already well versed in the art of torch welding I would suggest finding an arc welder to do this, what you are trying to do is tricky even though it can be done. What kind of equipment do you have and what size torch?

There is another fellow on here that has welded (if I remember correctly) about 2" thick steel with his torch and maybe even a bit thicker so maybe he will see this and have some input.
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Old 08-24-2009, 09:26 AM
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Quote:
Originally Posted by chadmw7
Should I keep upping the acet and then matching it with O2 until it does the job or try something else? How far should I open up the valves?(on the torch, not the tanks) Can I literally keep going until the torch valves are wide open or is that dangerous(this is all assuming that the tank regulators are set at 5-6psi each.
Whether or not you need to increase the pressure will be determined by your tip/hose size so we need that info before making any suggestions about that.
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Old 08-24-2009, 09:42 AM
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Thanks oldred. I was hoping you would weigh in on his one. I have a 1/4" hose and 0, 1, & 4 size tips. Can I make it work with that setup?
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Old 08-24-2009, 11:09 AM
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I'm not an expert in O/A welding (self-taught, so take this in stride), but I do believe that a #4 is too small to do any serious welding of 1/2" steel. Now, if you're trying to weld a small piece of 1/2" it might work (like welding a 2" square vs a table-top), but it'll take a long time to do so.

I don't have my charts in front of me, but I did find this page which shows a comparison of different tip sizes and steel thicknesses, and you're looking at a size 6 Victor tip for 1/2". This would also put you into a medium-duty torch body at a minimum (I use a Victor 100-series).

Welding 1/2" with an O/A torch is do-able, it might take a couple passes to get full penetration depending on what you're doing.
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Old 08-24-2009, 12:46 PM
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Quote:
Originally Posted by chadmw7
I have a 1/4" hose and 0, 1, & 4 size tips. Can I make it work with that setup?


If the sizes you are referring to are for Victor equipment then it is probably stretching it a bit. Did you preheat the 1/2" plate and how big is it? Preheating it with a cutting torch or rosebud will make a big difference and the size of the 1/2" plate will make a difference also, the larger it is the harder this will be to do.

Brimstone that is a very good chart, thanks for posting it. I agree the no.4 is going to be a bit on the small side here and what you said about the 2" square vs a table top is exactly what I was thinking too as to whether this can be successfully done or not. Certainly some preheat is in order here and I suppose even the table top size plate could be welded ok if preheated and the heat maintained during the welding, the welding tip might not supply enough heat by itself if the plate is too big.
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Old 08-24-2009, 06:35 PM
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Thanks guys.

I have 3 pieces to weld together - 1/2" x 5 1/2" x 2 3/4" plate to a piece of 2 1/2" steel tubing 2 3/4" long and 1/4" thick. Then I need to weld the other end of the tubing to a 1/2" plate that's 5 3/8" x 1 3/4".

I'm learning about preheating now. The thought did cross my mind but I didn't realize it might make a big difference. If so, how can I know how long to preheat, etc?
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Old 08-24-2009, 07:14 PM
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If we are talking about mild steel here you are not likely to get it too hot so just heat those pieces as hot as is practical especially right at the weld. While they are still hot use the large tip you have and see if you can melt a puddle in the 1/2" plate and move it along the intended weld area. Remember you are trying to fuse the two pieces to each other not trying to stick them together with the rod so melt the base of both pieces and add filler rod as needed, don't try to melt the rod onto either part. Try to maintain an equal area of the puddle on each part and feed the rod in from the back (my method anyway) just adding metal from the rod to the molten puddle, never melt the rod and try to fuse it to the parts. Give it a try and let us know what happens, it may seem a bit difficult at first but trust me you will get the hang of it then it becomes much easier. You are doing yourself a big favor by learning to do this and if every welder would take the time to learn to gas weld first they would all be better welders for the effort.
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Old 08-24-2009, 10:52 PM
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Thanks oldred. That makes perfect sense. I appreciate the extra info regarding the technique too. That's pretty much the way I understood it but that cleared up a few things I had wondered about. I'll give it a try.
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Old 08-25-2009, 12:36 AM
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i keep my rig at 20 oxy and 7-8 acty but im an a/c guy what do i know
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Old 08-25-2009, 08:40 AM
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Quote:
Originally Posted by raiderdave007
i keep my rig at 20 oxy and 7-8 acty but im an a/c guy what do i know


At the risk of starting an argument here I have to say that for welding the regulator setting has little to do with it as long as the pressure is high enough to deliver the needed volume. There has long been arguments of where to set the regulator for proper welding pressure but actually the best setting is the lowest practical pressure that delivers the right gas volume to the torch tip. If it is too high then the flame will still be the same but the control valve will not be open as far. The fact is the flame at the tip will not know the difference between a pressure setting of, for instance, 5 PSI or 15 PSI on the fuel side, certainly the line pressure will be higher but the gas pressure in the discharge side of the control valve will be the same as long as the flame is adjusted the same. Raising the fuel or Oxygen pressure on the regulator simply raises the potential for a larger flame and if the flow is adjusted to any given amount of volume with the control knob at the torch then the the flame will never know the difference, the difference will be that the control knob will not be opened as far with the higher line pressure.
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Old 08-25-2009, 09:32 AM
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That makes sense. So raising the regulator settings from a minimum of 4 or 5 psi for welding never comes into play unless you just can't get enough volume by adjusting the torch valves, right?

This is good stuff.
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