acetylene vs propane

**Alistair** · 02-05-2015

Yes, I've read the Victor recommendations before. They also say that the cracking noise that you get when switching off the fuel first causes a shockwave that draws soot inside the torch and onto the valve seats, but then many dispute that. Over the years, I've read plenty of advice on the web arguing the correctness of both sequences of torch shutdown. Confusing.

I ended up talking to the proprietor of a locally renowned regulator and torch repair shop (Hansen and Miller) and asking his take on this and he told me that in his experience (40 years plus) shutting off fuel first, and O2 second, is the safest way to go. He's seen it and repaired it all and he told me "fuel on first, fuel off first", for what that's worth. He (Harold Heia) is very well known and respected in the Seattle area metal working community so I personally take his advice quite seriously and put a lot of value in it.

If you look at Victors reasoning in the passage you pasted you can see it's a bit thin. Shutting off O2 first to remind you that you might not have your Acetylene turned up high enough is a bit silly imo. You should be setting it correctly, from the get go. and you have a chance to so every time you light the torch. Also, you can (and should) easily check for valve leaks with soapy water., so turning off the O2 first for those reasons seems a bit silly to me.

It does seem odd that Victors advice flies in the face of most other manufacturers. Maybe it would just be best to follow the advice of who ever made your torch? This all being said, I use a gas saver so I don't actually turn off the torch myself, I just let the valves in the gas saver do it but I do set those valves so that the fuel line is closed first, barely ahead of the O2, so I get a slight "pop".

Alistair.

**Will Neide** · 02-06-2015

Originally Posted by Alistair

Maybe it would just be best to follow the advice of who ever made your torch? This all being said, I use a gas saver so I don't actually turn off the torch myself, I just let the valves in the gas saver do it but I do set those valves so that the fuel line is closed first, barely ahead of the O2, so I get a slight "pop".

Alistair.

This is precisely what I'm doing. Victor recommends to do it this way, so I do. I have tried the other way, and quite honestly, I'm not a fan of the pop. Doesn't seem to make sense to create a mini explosion unnecesarily. It appears either way seems to work, but for me it is a more controlled shutdown when I do oxygen first then fuel (propane in my case).

Here's the Uniweld safety tips: Safety Tips
Here's Miller: https://www.millerwelds.com/pdf/FAQ_TorchOperation.pdf
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They all recommend oxygen first.

**Will Neide** · 02-06-2015

How to Properly Light, Adjust and Shut Down an Oxyâ€“Acetylene Torch | The Harris Products Group

Harris recommends turning oxygen first as well.

I have seen a few places that say to do fuel first, but that seems to go against the manufacturer recommendations.

**Alistair** · 02-06-2015

This is really interesting. I've gotten a lot of advice in person from experienced metalworkers who do exactly the opposite. I wonder if it's an old school/new school thing, or if newer torches have a feature that requires the O2 to be shut off first? Both my torches are older Victor J28's (30-35 years old, not sure exactly) that I have had professionally rebuilt. The guy who did the work also recommended fuel off first.

Maybe if I had purchased new equipment the advice would have been different? I might start a thread on a local metalworking forum that I'm on and see if there's any basis to that. I'll post here with anything interesting that pops up.

Alistair.

**Alistair** · 02-06-2015

Apologies in advance for beating a dead horse here, but I did ask around a little and got a few responses from people who know way more about this than I do. Only a few responses so far, 2 to 1 in favor of turning off the fuel line first, but this is not enough responses to to mean anything from a statistical perspective. I have pasted a response from a welding instructor below that is interesting,

"I have taught welding for 19 years now and I have also heard both sides of the argument, but the final arbiter for me is Harold who owns Hansen & Miller Torch and Regulator Repair.

The basic argument for shutting off the oxygen first is that it prevents a backfire from causing soot to build up inside the torch head.

Harold counters this with a story of one of his clients.
At the end of the day, the fellow shut off his torch Oxygen first, then coiled up the hose and hung the torch on the regulator.
He went home, and about 4 hours later his tank set exploded, taking out a section of his shop.
The forensic investigation of the torch showed it had a tiny leak on the fuel gas valve.
When he shut off the oxygen the fuel leak allowed a tiny flame to keep burning at the torch tip.
So small he didn't notice it.
For 4 hours that tiny flame was heating the side of his oxygen cylinder until the tank wall failed, rupturing the cylinder.
If he had shut off the fuel gas first the excessive oxygen would have snuffed out the flame.

So for me it is fuel gas on first, fuel gas off first.

And FYI soot will build up inside every torch and fuel gas hose due to carbon condensing and dropping out of solution with the fuel gas.
It is one of the reasons for replacing your hoses on a regular basis."

Anyway, for anyone interested, the full thread can be referenced here,
http://tinyurl.com/njztkgp

Alistair.

**jclay** · 02-06-2015

Originally Posted by Alistair

Apologies in advance for beating a dead horse here, but I did ask around a little and got a few responses from people who know way more about this than I do. Only a few responses so far, 2 to 1 in favor of turning off the fuel line first, but this is not enough responses to to mean anything from a statistical perspective. I have pasted a response from a welding instructor below that is interesting,

"I have taught welding for 19 years now and I have also heard both sides of the argument, but the final arbiter for me is Harold who owns Hansen & Miller Torch and Regulator Repair.

The basic argument for shutting off the oxygen first is that it prevents a backfire from causing soot to build up inside the torch head.

Harold counters this with a story of one of his clients.
At the end of the day, the fellow shut off his torch Oxygen first, then coiled up the hose and hung the torch on the regulator.
He went home, and about 4 hours later his tank set exploded, taking out a section of his shop.
The forensic investigation of the torch showed it had a tiny leak on the fuel gas valve.
When he shut off the oxygen the fuel leak allowed a tiny flame to keep burning at the torch tip.
So small he didn't notice it.
For 4 hours that tiny flame was heating the side of his oxygen cylinder until the tank wall failed, rupturing the cylinder.
If he had shut off the fuel gas first the excessive oxygen would have snuffed out the flame.

So for me it is fuel gas on first, fuel gas off first.

And FYI soot will build up inside every torch and fuel gas hose due to carbon condensing and dropping out of solution with the fuel gas.
It is one of the reasons for replacing your hoses on a regular basis."

Anyway, for anyone interested, the full thread can be referenced here,
http://tinyurl.com/njztkgp

Alistair.

Very interesting failure mode cascade. I've never been comfortable hanging my torch near the cylinders or hose coil; I always arrange things so that doesn't happen. Now my gut has confirmation!

**MrkiMedo** · 02-06-2015

Originally Posted by Alistair

Apologies in advance for beating a dead horse here, but I did ask around a little and got a few responses from people who know way more about this than I do. Only a few responses so far, 2 to 1 in favor of turning off the fuel line first, but this is not enough responses to to mean anything from a statistical perspective. I have pasted a response from a welding instructor below that is interesting,

"I have taught welding for 19 years now and I have also heard both sides of the argument, but the final arbiter for me is Harold who owns Hansen & Miller Torch and Regulator Repair.

The basic argument for shutting off the oxygen first is that it prevents a backfire from causing soot to build up inside the torch head.

Harold counters this with a story of one of his clients.
At the end of the day, the fellow shut off his torch Oxygen first, then coiled up the hose and hung the torch on the regulator.
He went home, and about 4 hours later his tank set exploded, taking out a section of his shop.
The forensic investigation of the torch showed it had a tiny leak on the fuel gas valve.
When he shut off the oxygen the fuel leak allowed a tiny flame to keep burning at the torch tip.
So small he didn't notice it.
For 4 hours that tiny flame was heating the side of his oxygen cylinder until the tank wall failed, rupturing the cylinder.
If he had shut off the fuel gas first the excessive oxygen would have snuffed out the flame.

So for me it is fuel gas on first, fuel gas off first.

And FYI soot will build up inside every torch and fuel gas hose due to carbon condensing and dropping out of solution with the fuel gas.
It is one of the reasons for replacing your hoses on a regular basis."

Anyway, for anyone interested, the full thread can be referenced here,
http://tinyurl.com/njztkgp

Alistair.

Do I understand correctly that man did not close the valves on the tanks nor purged the lines when leaving the shop? If so, he might have larger issues than sequence of shutting valves on the torch.

**Alistair** · 02-06-2015

Originally Posted by MrkiMedo

Do I understand correctly that man did not close the valves on the tanks nor purged the lines when leaving the shop? If so, he might have larger issues than sequence of shutting valves on the torch.

Agreed, it would certainly seem to be the case anyway.

Alistair.

**ljm** · 02-07-2015

As several of you have rightly said, an ignition source is required for O2 to do its thing. But where pure O2 is present, ignition can come from many sources that perhaps we wouldn't normally consider; a burr inside a valve or fitting, even a poorly designed component that for example has sharp bends in the path of gas flow.

I'm a professional diver and have designed and built oxygen system. Of course, there are differences, but also similarities here. But I've seen for myself a hose start to burn as O2 ran through it. it transpired that the source of ignition was localised damage inside the hose, causing friction and so heat.

The big difference in that instance was the pressure involved. However, I've also opperated hyperbaric chambers; in one of those (with pressure at or below those involved in welding, once we're downstream of the regulator) we don't even wear nylon clothes or wear watch.

There are clear differences here. And no doubt someone here can express those in terms of the energy involved etc etc.

But the point is, don't understand estimate what it takes to get a fire started in the presence of pure oxygen. There is however no need for alarm, only common sence and good practice.

**jclay** · 02-07-2015

When the fuel is turned off first, does the flame front migrate into the tip and is the pop a result of its being extinguished within the tip, or does the entire event take place outside the tip orifice? If the former, it doesn't sound good but I don't know the details of the event.

The Victor instructions reminded me that the speed of the mixture exiting the tip is (largely....or entirely?) what prevents combustion migration into the tip. That is making me rethink my use of the same size tip for everything from crowns to braze-ons (turned way down). Thanks for posting them.

**John Durning** · 02-12-2015

This is a great thread, I'm finding it really useful.

I'm running a BBQ propane / Oxygen concentrator set up but I'm having no luck getting the thing lit. I can only use a tiny amount of propane before the flame becomes detached. When I switch the oxygen concentrator on (I run it for a minute or so beforehand) I start with almost no flow and slowly bring it up. The flame starts detaching almost immediatly and when the oxygen flow gets to 1.5-2 lpm the flame goes out.

I've tried many variations on bringing up the O2 a bit, then the propane, then the O2, etc but it makes no difference. I've tried the 3 and 5 nozzle but still the same.

This is the kit that I bought:

The Welders Warehouse - Lightweight Heating and Brazing Torch for Oxygen + Propane

Anyone else seen this problem before? Could it be a problem with the propane itself or is it just a case of buy cheap buy twice?

**nspace** · 02-12-2015

I remember Doug mentioned something earlier in the thread about Propane specific tips. They differ from the acetylene tips in that they have a small recess in the end of the tip which helps hold the flame and keep it attached. You can still use the acetylene tips but they are more difficult to light from what I gather. Maybe the kit didn't come with these? Check to see if there is a countersunk hole in the end of the tip with another hole in the middle where the gas comes out.

I've had great luck with the Propane/NG specific tips from Torch Tools—The GENTEC 883TEN ones:
883TEN GENTEC Tip Ends, VICTOR TEN

**Doug Fattic** · 02-12-2015

Hi John,

There could be several issues causing the problem with your flame blowing out. 1st of all your concentrator needs to run long enough that it has purged the line of nitrogen. On my concentrator that takes 1 to 2 minutes. If its filters are dirty than it takes longer even up to 5 minutes if the unit hasn’t been cleaned in awhile. So my first recommendation is to let the concentrator run longer before lighting the flame. It is also possible that it isn’t putting out pure enough oxygen anymore so it might not be working properly. Check that your filters are clean.

A propane flame is more difficult to light than acetylene. There is a learning curve to getting the adjustments just right. It is easy to blow out the flame if the oxygen is turned up too fast. It takes a very small amount of a turn (depending on the handle this is maybe 1/16th or even 1/32nd of a turn) and if the knob is a bit sticky than it is very easy to go beyond the point where it should be and the extra flow just blows out the flame. I find it easier to have a very small amount of oxygen already flowing when I light the flame. Actually when I get it adjusted properly I don’t turn off the oxygen knob I just leave it on where it was last adjusted for the next time.

It is easy to have too much flow coming out of the concentrator. When I 1st got mine it took me awhile to find the right flow adjustment. Also try turning down your propane flow too so it doesn’t require as much oxygen flow.

A tip that does not have a recess is also harder to light. Tips can be designated for propane but still not have that helpful recess at the end. The width and depth of this recess is about double the diameter of its orifice. This recess is why I like using Victor equipment that has them. Smith’s propane mixer/elbow/tips have more and bigger oxygen holes so its flow ratio of the 2 gases works better for propane but they don’t have the helpful recessed tips. Are your torch tips recessed?

Doug Fattic
Niles, Michigan

**Larry** · 02-12-2015

Hey Doug

Do you know if the Smith SMNE154 and SMNE153 have recessed tips. I'm having the same issues as John. I was previously using Smith's LT103, LT104 and LT106 tips. After giving it ago with the acetylene tips I finally gave up and called Smith and was told to try their LP tips.

**Doug Fattic** · 02-12-2015

Originally Posted by Larry

Hey Doug, do you know if the Smith SMNE154 and SMNE153 have recessed tips. I'm having the same issues as John. I was previously using Smith's LT103, LT104 and LT106 tips. After giving it ago with the acetylene tips I finally gave up and called Smith and was told to try their LP tips.

Larry, the NE series of tips are NOT recessed. They just have bigger orifices than the LT series. They are too big for the way I like to braze most joints. Are you using the AT-61 mixer/elbow? That is designed specifically for Propane while the similar AT-60 is for acetylene. They look alike but the AT-61 has bigger and more numerous holes in the mixing part that carries the gas to the tip.

Doug Fattic.
Niles, Michigan

**Larry** · 02-12-2015

Doug

Thanks for the reply. I'm using the AT-60 mixer. I don't think I will be able to find one of the AT-61 locally, but will try. I had to order NE tips, which should be here tomorrow.

**Doug Fattic** · 02-12-2015

Originally Posted by Larry

Thanks for the reply. I'm using the AT-60 mixer. I don't think I will be able to find one of the AT-61 locally, but will try. I had to order NE tips, which should be here tomorrow.

I just went to my shop and tried lighting my Smith AW1A torch using both an AT-60 and AT-61 mixer/elbows with a LT-104 tip. The tip is only marked with a number 56. This represents a #56 drill bit size and means its orifice is .046” in diameter. This is the same size as a Victor #2 tip. I set my propane regulator to just over 3 psi and my oxygen concentrator at a bit more than 2 lpm. I had just a bit of oxygen flowing already when I lit the torch. I could light both of them without any trouble. It did seem like the AT-61 was a bit less fussy but I’m so used to lighting them that it is easy for me to make adjustments with whatever tip or torch handle I’m using without thinking. I do remember that when I 1st got my concentrator I was having trouble not blowing out the flame so there is a bit of a learning curve to lighting them.

The AT-61 has more (6) and bigger holes for the flow of propane in the mixer. The AT-60 holes (4 of them) are smaller for acetylene. I bet it is unlikely you can buy the AT-61 locally since it is a less common unit. I also tried lighting the flame using the larger NE tips with the same good results.

**John Durning** · 02-13-2015

Thanks Doug. The nozzles I have don't have a recess so that's something I might look into later on.

Quick question about the concentrator. How do you start the flow of oxygen? The way I've been doing it is to have the knob on the torch all the way open and then try to control the flow using the knob on the concentrator itself. The reason I do this is that I'm worried about damaging the concentrator due to the line being blocked. Should I just turn the concentrator up to 4-5 lpm and then control the flow using the torch?

**shirk** · 02-13-2015

I open the oxygen on the torch and let my concentrator run till it's up to speed. Mine has a flashing light that tell's me it's putting out pure oxygen (or rather whatever it's internally set to that it thinks is it's operating level).

Once I am ready to light my torch I will turn off the oxy on the torch, turn on the propane and then add back in the oxy. If I turn off the oxy on the torch for too long the concentrator will beep until it gets flow again.

When done I'll shut off the oxy at the torch, then the propane. Then I'll open the oxy back up to allow the concentrator to keep running if I know I plan to fire the torch back up.

If completely done I'll shut off the oxy at torch, purge the propane, then open the oxy back up and shut down the concentrator letting it be the last purge.

My work space is a 16x24ft garage and I always work with a door man open.

**Doug Fattic** · 02-14-2015

Originally Posted by John Durning

Quick question about the concentrator. How do you start the flow of oxygen? The way I've been doing it is to have the knob on the torch all the way open and then try to control the flow using the knob on the concentrator itself. The reason I do this is that I'm worried about damaging the concentrator due to the line being blocked. Should I just turn the concentrator up to 4-5 lpm and then control the flow using the torch?

Like Brian just illustrated there are probably several ways to lit the propane and adjust the oxygen flow. The way I do it is to turn on the concentrator several minutes before it will be used. Usually this is before I start to flux the joint so I don’t have to wait. I already have the oxygen knob on the torch handle left open a bit from my last braze. This is so the unit doesn’t start to beep a warning that no oxygen is coming through. I set the flow on the concentrator 1st to somewhere between 2 and 3 lpm with the oxygen knob on the torch handle open about an 1/8th to a quarter turn. I don’t think it matters much how precise the settings are in this stage. When I am ready to braze, I turn the oxygen knob on the torch handle so it is open about an eighth of a turn. Both the concentrator and torch handle now have approximately the right adjustment with the oxygen flowing. With those set I am now ready to light the propane. My setting on the propane regulator is around 3 or 4 psi with smaller tips. I light the propane and then adjust both both knobs on the torch handle so I get the right volume of gas coming through as well at the right percentages so it is a neutral flame.

If I was having trouble, I would have the oxygen turned off at the torch handle and open it up slowly after the propane is lit to help me figure out adjustments. This way I can keep the propane only flame adjusted 1st so the flame stays attached to the tip. A flame with oxygen stays on the tip better than just a propane only flame.

While I am no expert on oxygen concentrators, I don’t think it hurts them to have the oxygen flow restricted by the torch. As an experiment I tried adjusting the flame with the flow on the concentrator with the oxygen knob several turns open. It worked although the oxygen control was less precise and took a bit of time to stabilize so I wouldn’t want to bother doing it that way myself.

John, I keep wondering if your concentrator is putting out pure enough oxygen. I am suspicious that there is still too much nitrogen in the line and that is what is blowing out your flame and not that your oxygen flow is too strong for the amount of propane. Of course it could also be related to the mixer and tips your are using too. I don’t have a suggestion for testing it except to switch your concentrator with someone whose unit is working properly and see if it is the concentrator or the mixer and tips. I did this with a VS member one time to make sure his concentrator was working properly.

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