Welding torch fuel question

[willlgord]

I’ve been using Mapp and propylene in my gas torch set (an oxy/acetylene setup) for decades, I went to pick up more propylene and they didn’t have any so they sold me an acetylene tank ( I’m in a real hurry to finish a brazing job). After getting home I found I needed a different ****** on my fuel regulator along with a tank to regulator adapter and went to pick one up. Now they’re telling me it’s dangerous to switch fuel gasses and want to sell me a new regulator and hoses. I’m rather ticked off they didn’t tell me this before they sold me an acetylene tank. Is this true? I found some information on the web that says it’s ok to switch.
Thanks!

 

[The Cobbler]

what size acetylene tank, MC, B? they each have different connections than a regular larger acetylene tank.
you can buy adapters for them to fit . Years ago I bought a new ****** to put into my regulator so I didn;t have all the bulk of an adapter . not sure if they are still available .

 

[willlgord]

what size acetylene tank, MC, B? they each have different connections than a regular larger acetylene tank.
you can buy adapters for them to fit . Years ago I bought a new ****** to put into my regulator so I didn;t have all the bulk of an adapter . not sure if they are still available .

The connectors aren’t the problem, they say my regulator and hoses are contaminated in some way and it’s dangerous to switch fuels even if I purge the hoses with compressed air.

 

[no704]

Following, what about propane oxy?

 

[logixjock]

The connectors aren’t the problem, they say my regulator and hoses are contaminated in some way and it’s dangerous to switch fuels even if I purge the hoses with compressed air.

They are full of ****, fuel gas is fuel gas, I've swapped between oxy/acetylene and propane lots of times. Can't imagine propylene would be any different. You are supposed to use a type-T hose for propane, but in actual practice the cutting tips are the only thing you have to change.

 

[Sumboodie]

Seems like a special torch? Oxygen/acetylene or oxy/propane is all I've worked with.

Edit... other than the little campfire starter propane "torches"

 

[willlgord]

Seems like a special torch? Oxygen/acetylene or oxy/propane is all I've worked with.

Edit... other than the little campfire starter propane "torches"

It’s a regular oxy/acetylene torch, nothing special

 

[rlitman]

The connectors aren’t the problem, they say my regulator and hoses are contaminated in some way and it’s dangerous to switch fuels even if I purge the hoses with compressed air.

NEVER send compressed air through an oxygen hose. I hope you're aware of this, but I feel it still needs to be said.

Why would you purge a fuel gas hose with air ever? That's pointless and dangerous. Purge fuel gas hoses with fuel gas, and purge oxygen hoses with oxygen!

As for the rest of your questions, we need to know more about your setup to know how much the story you got was BS, and how much of your story was lost in the telephone game. What pressure does your fuel regulator go up to? What's the "grade" of your fuel hose (R, RM or T)?

 

[willlgord]

If I did do that I would purge the hoses with the fuel gas before using the torch, just thought it might help remove the “contamination “. My setup is a normal Airco oxy/acetylene set made to use with acetylene. When I first bought it I used mapp and switched to propylene later.

 

[GaryM909]

They are full of ****, fuel gas is fuel gas, I've swapped between oxy/acetylene and propane lots of times. Can't imagine propylene would be any different. You are supposed to use a type-T hose for propane, but in actual practice the cutting tips are the only thing you have to change.

I ran propane through type R hose. After a couple months and probably only about 10 hours use the casing was starting to blister. I didn't hesitate to replace it with typeT.

 

[rlitman]

Fuel gases don't contaminate each other. Grade R and RM hoses can be damaged on the inside by fuels other than acetylene, so it is possible that's what they're getting at.

 

[willlgord]

I was able to find the adapter I needed so I’m all set, thanks for the replies. Everyone I spoke to agreed it’s fine to switch fuel gases, I’ll keep a close eye on my hoses just the same.

 

[ching0n]

can you braze w/o an oxygen tank? B tank often gets hot enough depending on the job....I know you're in a hurry so thought I'd bring it up.

 

[willlgord]

I’m not sure about brass brazing but I’ve silver brazed copper pipe with a b tank w/o oxygen before. I think it was acetylene but it might have been propylene or propane.

 

[The Cobbler]

you won't braze too big a part with acetylene only .

 

[ItsNemo]

They are full of ****, fuel gas is fuel gas, I've swapped between oxy/acetylene and propane lots of times. Can't imagine propylene would be any different. You are supposed to use a type-T hose for propane, but in actual practice the cutting tips are the only thing you have to change.

They aren't full of ****, you should change hoses...a leak in the acetylene/propane line can be fatal. Regulators usually have different ranges, would be dangerous running a propane regulator on acetylene bottle.

You can switch between the two yes but if the guy didn't know getting acetylene needed to be treated differently, the shop was doing him a favour telling him the dangers.

 

[logixjock]

They aren't full of ****, you should change hoses...a leak in the acetylene/propane line can be fatal. Regulators usually have different ranges, would be dangerous running a propane regulator on acetylene bottle.

You can switch between the two yes but if the guy didn't know getting acetylene needed to be treated differently, the shop was doing him a favour telling him the dangers.

I've been using an acetylene regulator with a 40# LP bottle on my main torch setup since early 1997. Guess I'll stop now since you decided it doesn't work.

 

[ItsNemo]

I've been using an acetylene regulator with a 40# LP bottle on my main torch setup since early 1997. Guess I'll stop now since you decided it doesn't work.

I said you can switch between the two, technically...people like you are why a couple times a year we hear about garage explosions, it's all perfectly fine until it's not. And given the amount of energy stored in an oxy/fuel setup, it's not something worth mucking around with as compared to say a garden hose where the worst thing that happens is you get a little wet.

PVC air lines get a lot of hate around here (rightly so)...improper oxy/fuel setups should be right up next to them.

*edit* just doing some rough math, for each 10cf of acetylene, you have approximately the same potential energy as 2lbs of TNT. So a typical B tank with 40cf is 8lbs of TNT.

(10cf of acetylene is about 329 grams, each gram has 11.8kJ of energy, so 3,882,200 joules, and 1kg (little more than 2lbs) of TNT 4,184,000 joules, so close enough).

 

[MoonRise]

Acetylene regulator with a propane cylinder is not a big problem by itself. You just might not be able to run the higher pressures on the fuel that some large propane tips can use.

A propane regulator on an acetylene cylinder IS a big problem.

If you run the acetylene pressure higher than 15 psi, the acetylene gas can spontaneously decompose all by itself. That is the reason why the acetylene regulator only goes up to 15 psi and any higher pressure is in the RED zone. Dang slightly unstable molecule.

If you are using different fuel gases, you NEED to use Grade T fuel hose. You can use that hose with any common fuel gas (acetylene, propane, MAPP if you can somehow get some actual MAPP gas, propylene gas blends, etc).

If you are using ONLY acetylene as the fuel gas, you can use Grade R or RM fuel hose.

Do NOT-NOT-NOT use Grade R or RM fuel hose with any other fuel gas.

And you need to (or should) use the appropriate torch tip for the fuel gas that you are using. The tip geometry and internal passage size/geometry can be slightly different for the different fuel gases, at least partially because the different fuel gases are used at different fuel-oxidizer (either air or oxygen) ratios and pressures.

(Nemo, I agree that oxy-fuel setups need to be used carefully and that PVC piping should NEVER be used for compressed gas storage or transport. btw, I calculate ~333 grams of acetylene in a 10 ft3 cylinder. )

 

[Zeke]

Seems to me that I remember that when the acetylene bottle is getting low that the rate of flow needs to be reduced some. The max pressure is just a measurement of flow since gauges don't have flow meters. All I know is that big users will put several bottles on a manifold to reduce flow from individuals regadless of the set pressure.

 

[finn]

Seems to me that I remember that when the acetylene bottle is getting low that the rate of flow needs to be reduced some. The max pressure is just a measurement of flow since gauges don't have flow meters. All I know is that big users will put several bottles on a manifold to reduce flow from individuals regadless of the set pressure.

Back asswards. At a given valve (orifice) setting, lower pressure will result in lower flow, so, as the pressure drops, the valve (orifice) has to be open farther to maintain the same flow to the torch.

 

[Zeke]

Back asswards. At a given valve (orifice) setting, lower pressure will result in lower flow, so, as the pressure drops, the valve (orifice) has to be open farther to maintain the same flow to the torch.

You may not be correct.

What is the 1/7 acetylene rule

www.harrisproductsgroup.com

 

[MoonRise]

Zeke,

'big users' will manifold several acetylene cylinders together mostly for flow/withdrawal rate safety considerations.

Acetylene should not (must not) be withdrawn at a rate faster than 1:7 (newer quidelines are 1:10) than the cylinder volume in ft3. This is to allow time and volume for the dissolved acetylene in the cylinder to come out of solution from the acetone it is dissolved in and turn to gas and then flow out of the cylinder safely.

example: you have a B cylinder of acetylene of 40 ft3. The maximum safe withdrawal rate from that cylinder is not more than 40 / 7 = 5.7 cfh (new guidelines is 40 / 10 = 4 cfh). That means that the biggest recommended size welding tip you can safely use with that B cylinder is a Victor #1 (fuel flow rate of 3-6 cfh) or maybe just barely a #2 (fuel flow rate of 5-10 cfh) acetylene welding tip (W or RTE series).

 

[finn]

That’s a different question. My answer relates to how flow and pressure work, not what the max withdrawal rate that’s safe for an acetylene tank is.

 

[MoonRise]

You posted the link to the Harris write up about the 1:7 withdrawal rate rule as I was typing up my reply.

 

[Zeke]

That’s a different question. My answer relates to how flow and pressure work, not what the max withdrawal rate that’s safe for an acetylene tank is.

Well, your 'answer' skates safety issues. Your answer pertains to the pressure on the high side of the regulator. Let's not quibble over terms. I was correct in saying as the bottle gets low, care must be used. The role of the regulator is to maintain even pressure, right? Why would it drop until pressures are equalized? What ever you do by opening the valve more, I'm not doing it. When it gets to that point, I'm going in for an exchange.

 

[pcmeiners]

"’m not sure about brass brazing but I’ve silver brazed copper pipe with a b tank w/o oxygen before. I think it was acetylene but it might have been propylene or propane."

Acetylene alone, with the correct tip can braze rather large pipe (2-3") but propane will not. Also since you are new to acetylene, you best educate yourself, it can be very dangerous under multiple circumstances.

 

[finn]

Well, your 'answer' skates safety issues. Your answer pertains to the pressure on the high side of the regulator. Let's not quibble over terms. I was correct in saying as the bottle gets low, care must be used. The role of the regulator is to maintain even pressure, right? Why would it drop until pressures are equalized? What ever you do by opening the valve more, I'm not doing it. When it gets to that point, I'm going in for an exchange.

Not quibbling at all. Physics is physics, and that’s all I was referring to. If reducing flow as the bottle empties is required for safety, so be it.

You can’t rewrite physics and the gas laws under the guise of safety,, though, no matter how important you think you are. The laws are the laws. Reducing pressure reduces flow, all other things being equal.

Not sure how single stage regulators vs two stage regulators fit in here, or flow meters vs regulators for that matter.

 

[Zeke]

Not quibbling at all. Physics is physics, and that’s all I was referring to. If reducing flow as the bottle empties is required for safety, so be it.

You can’t rewrite physics and the gas laws under the guise of safety,, though, no matter how important you think you are. The laws are the laws. Reducing pressure reduces flow, all other things being equal.

Not sure how single stage regulators vs two stage regulators fit in here, or flow meters vs regulators for that matter.

We got off on a tangent here and I may as well never say anything as someone is going to refute, top it, or argue. But honestly, if the bold above is true....


I know, we haven't heard the end of this so I yield to the last shot. Thank you and good day.

 

[pcmeiners]

Flow rate safety?.....

How about the more common dangers of back flow or flash back. Should oxygen flow back into a fuel tank or the reverse you have a bomb. If a flame flows back into a torch or hose you also can have a damaging explosion or fire. All fuel regulators should have a flashback arrestor, fuel and oxygen as should torches handles.

Why Do We Need Check Valves or Flash Back Arrestors? | Ron-Son’s Torch Repairs & Sales Ltd.

Why Do We Need Check Valves or Flash Back Arrestors? “Suitable safety devices to prevent reverse gas flow and to arrest a flashback must be installed on each hose in an Oxy-fuel system, between the torch and the regulator." --Work Safe BC regulation 12.120 Flashback prevention Click here for the...

ronsonstorch.com

 

[nadogail]

I am planning on building a welding torch for my workshop, but because I don’t want to use Fuel Gas I am looking for a source of Carbon Rods.

Where are GJ Members getting Carbons for their welding torches?

 

[WAID]

I am planning on building a welding torch for my workshop, but because I don’t want to use Fuel Gas I am looking for a source of Carbon Rods.

Where are GJ Members getting Carbons for their welding torches?

Are you looking to do carbon arc welding? Gouging too? Why not any of the more modern arc processes?

 

[nadogail]

Are you looking to do carbon arc welding? Gouging too? Why not any of the more modern arc processes?

I am thinking of brazing steel sheet metal.

 

[WAID]

I am thinking of brazing steel sheet metal.

That's venturing outside of my experience, but I was under the impression carbon arc rods for gouging were suitable and I'd get those at my local welding shop. They do appear to be readily available online. Previous jobs I worked had a lot of carbon arc gouging being done(not by me mind you) I just pull out my oxyacetylene torch though when I braze, and have no carbon arc brazing experience. I would have figured you still need the constant current power supply to power it. You can braze with TIG equipment.

 

[nadogail]

That's venturing outside of my experience, but I was under the impression carbon arc rods for gouging were suitable and I'd get those at my local welding shop. They do appear to be readily available online. Previous jobs I worked had a lot of carbon arc gouging being done(not by me mind you) I just pull out my oxyacetylene torch though when I braze, and have no carbon arc brazing experience. I would have figured you still need the constant current power supply to power it. You can braze with TIG equipment.

I don’t have TIG equipment or an Oxy Acetelyene torch, I have read a magazine article many years ago about building your own Carbon Arc torch. I think the article mentioned using carbons from old flashlight batteries.

 

[WAID]

I don’t have TIG equipment or an Oxy Acetelyene torch, I have read a magazine article many years ago about building your own Carbon Arc torch. I think the article mentioned using carbons from old flashlight batteries.

Do you already have a constant current power supply to use? Thats more or less the expensive part and the capabilities of that somewhat determine the carb9n rod size you need. The carbon rods are easy and cheap like here at baker gas or here at amazon. My local welding place is Central welding and they can also provide carbon rods but they aren't much of a online presence.

 

[nadogail]

Do you already have a constant current power supply to use? Thats more or less the expensive part and the capabilities of that somewhat determine the carb9n rod size you need. The carbon rods are easy and cheap like here at baker gas or here at amazon. My local welding place is Central welding and they can also provide carbon rods but they aren't much of a online presence.

I do have a Hobart Stickmate with both AC and DC outputs.

 

[WAID]

I do have a Hobart Stickmate with both AC and DC outputs.

Oh gotcha. That does simplify things, though you may find the current output limiting for all but the smallest carbons. Those carbon rods from online or a local welding shop are probably your best bet. This welding web discussion does mention somebody having trouble with them but it looks to be at least partially an arc stability limit on machine polarity and current output. Hopefully that helps you. I would suggest reconsidering the oxy-fuel torch as it really is a versatile and useful tool. There are dangers but they are very managable.