One more QxyAcetylene Question

[TxDoc]

I bought this little portable system for when I cannot get the workpiece to the plasma cutter or the plasma cutter to the workpiece. It uses the 10CF MC acetylene cylinder, 20 CF type "R" oxygen cylinder. It is for "emergencies" or as a headache preventive. It will not be a daily used item.

It came with valves and check valves, but no flashback arrestors and/or non-return valves. From what I gather, a check valve will not stop a pressure or shock wave. Should I install the flashback arrestor or non-return valves? And, at the valve end or the torch end....or both?

I don't mind extra safety. I just wouild rather not go short and risk an explosion. I do have several friends who are very experienced with this, but wanted to see what you think is the safest thing to do.

They can help me with learning to light the torch, setting the flame and cutting and shutting down with hands on one on one demonstration. But, if you have any suggestions, comments or pearls of wisdom with proper technique or procedures, I will be more than attentive.

Thanks

 

[Franz©]

I hope you don't need a lot of cutting time because that setup is good for about 5 minutes.
It probably also has 3/16 hose, so adding flashbacks and check valves might require adaptors. Personally, I'd spend the money and install at least one of those devices. Even small cylinders hurt like hell when they blow up.

 

[Red Green]

I have Flashback arresters at the regulators and at the torch head. I had them at the torch head only then I droped a hot part on the Oxy. hose and caught it on fire so I added a set to the regulators.

 

[TxDoc]

I appreciate the help and info.

 

[russlaferrera]

Most of the info you seek, can be found in a free booklet from "Smiths Equipment" You can Google the address.


Franz, FYI you only should cut 1/7 of the tank capacity in an 1 hour span.

 

[Franz©]

Franz, FYI you only should cut 1/7 of the tank capacity in an 1 hour span.

ACTUALLY, the 1/7 rule won't be a problem cutting with that tank configuration. The Oxygen will run empty in 5 minutes and the acetelene flow won't have exceded the 1/7 rule.
You can even manifold a pair of 20cf oxygens together and not excede the 1/7 rule cutting.

 

[russlaferrera]

ACTUALLY, the 1/7 rule won't be a problem cutting with that tank configuration. The Oxygen will run empty in 5 minutes and the acetelene flow won't have exceded the 1/7 rule.
You can even manifold a pair of 20cf oxygens together and not exceede the 1/7 rule cutting.

Sure it would. a MC tank as 10cf. You need 6 scfh to operate the smallest cutting tip. Also a oxygen bottle at 20 cf the flow rate is 10% of the volume. You need 30 scfh to cut. All this to cut 1/8 steel.

If he were to manifold the tanks. IMO he is better off renting bigger tanks ie 20 acety and a 40 oxy as it would be cheaper for the gas

 

[Franz©]

Believe me when I tell you, a 20cf tank of Oxygen won't support even a small cutting torch for 5 minutes.
Your profile says you're old enough to remember the wonderful government issue backpack torches with a MC acetelene and a pair of 20cf Oxygens manifolded. They camn in rectangular steel cans that looked like a tall ammocan.

After you shlepped that damn contraption on your back you quickly learned the total burn time with 40cf of Oxygen wasn't sufficient to burn a half inch thick plate 3 inches before the oxygen crapped out.

20cf oxygen tanks are for small brazing and welding aplications, NOT for cutting. The limitation of the oxygen suply won't bring the MC cylinder into deep drawdown.

Oh yea, all torch manufacturers cf/hour cosumption ratings are about as accurate as the EPA mileage ratings on a car.

 

[russlaferrera]

I agree with you. However the origional post stated he has a 10cf acet and a 20 cf oxy. for emergency use. Cutting would be out of the question as there in not sufficient volume. He needs 7 cf of acet he has .7 cf available. He needs 30 cf of oxy he has 2cf available. This is based on a use chart from Smiths Equipment. Honest, I am not making this up LOL When reading this I found out you can only use 10% of oxy at a time. I have made a effort to quote the facts the best I can. I don't make them up. When I have an opinion I state so.

He does not have a manifold or extra tanks or anything you may suggest. What he does have is a 10 cf acet, and a 20 cf oxy tank So we agree he can not cut heavy steel with that setup.

As mentioned in the other post IMO, he would be better with larger tanks as he would be able to cut some steel and the cost of the next size tanks would be worth the small investment.

Should you respond or not to this great, as I type with two fingers and their tired. It is not my intention to piss anyone off. YOU WIN!!! LOL... Russ

 

[Franz©]

Where the hell did you find a statement that only 10% of oxygen can be used at a time?
Oxygen is a compressed gas in a cylinder, in this cars 20cf of oxygen compressed to 2200psi@70°f. The only limiting factor is the size of the opening in the valve fitting.

Acetelene is an entirely different storage system. The drawdown on acetelene is due to the physics of the rate at which the acetone in the porous media can give the acetelene off. Totally different situation.

That 10% discharge rate on an oxygen cylinder sounds like Wikipedia horseshit.

 

[goodfellow]

For what it's worth, I have a small portable set (like the set described in this thread). For very small heating and welding jobs it's fine, but for cutting it's just plain aweful.

I brought it to my in-laws house over Thanksgiving to cut four leaf spring shackles from his '87 F350 -- we made it through two shackles before it ran out of oxygen.

 

[russlaferrera]

From Modern Welding, by ALTHOUSE, TURNQUIST and BLOWDITCH and The Welding Encylopedia.

Now if you will, where do you get your info?

 

[Jared]

From Modern Welding, by ALTHOUSE, TURNQUIST and BLOWDITCH and The Welding Encylopedia.

Now if you will, where do you get your info?

I also have to disagree about the 10 percent on the oxygen, like stated before oxygen is a compressed gas there is no acetone of filler in the tank.

 

[Franz©]

Well I get most of mine from about 55 years of burning gas and rods and close to 30 years of experience running MIG following a little time burning wire in the SubArc process combined with a few things I've read over the years.

I've been rattlin this 10% rate on Oxygen around my head all day, and the only place that applys is with LOX oxygen suply systems. 10% comes into play 2 ways on LOX, first you can only boil off 10% of the liquid per hour (don't believe that been proven wrong too many times) and secondly you might as well use it or the LOX tank will boil off and blow 10%± of the remaining liquid volume thru the safety in a 24 hour period. LOX is very similar to propane and Co2 in a cylinder, operating at different temperatures and pressures.

On conventional oxygen, even on a sixpack, the only limitation on how fast the oxygen can come from the cylinder is valve opening. I can personally assure you a full 330 will completely empty 330cf of oxygen compressed to 2200psi in less time than ti takes to say oh **** when it falls and the valve shears. It will also travel completely thru 3 12" concrete block walls in that time, and your ears will ring for the next hour.

Acetelene as I said previously is a completely different storage system and set of dynamics.

 

[russlaferrera]

I concede to this post as the point is moot. Thanks to all for your imput. Russ

 

[W-Cummins]

I guess if you had a large enough tank you could freeze the valve up on a humid day....


BTW those MC or motorcycle tanks are really small, a setup like that might be nice with one of those little micro torches that the jewelery guys use....

William....