Oxy propane guidance

I have tried , within another thread , to ask for guidance in respect of the kit required to braze and Silver solder using Oxy propane , but the advice was Not forthcoming.

Could I try again , but ask for more specific advice ? .

What Oxygen gauge is most suitable for this process , not a gauge make , but the pressure range it controls . I have seen several that range from 0 to 4 Bar , and up to 10 Bar outflow , but I haven’t a clue which will work best .

I have no intention to use the kit for cutting , only for Brazing / Silver Soldering in the construction of smaller 7 1/4 “ loco’s .

Hello D.A.G

I can only pass on information for my gauges on the Oxy/Acetylene kit I have

Bottle pressure is marked up to 300 bar, new bottles are often at about 200 bar or so. The torch gauge is marked up to 6 bar but I usually run that at about 2 bar, plenty enough for welding.

I can't really see that an Oxy/propane set up will be any different; you will of course need propane gauges for the fuel.

No grease or lubricants on the threads of course, fuel threads are left hand

I hope that helps you

Brian

I have just been to the workshop to check and Brian has reported pretty much what I found. My Oxy propane set up is as follows:

HobbyWeld cylinder supplying a 2 stage regulator with up to 6.3 Bar outlet. Propane is supplied via a 0 - 30 psi regulator. I don't have spark arrestors, but probably should. The torch is a Saffire 3. All equipment purchased second hand.

I use the gear for occasional brazing using either the Saffire cutting head (flip the cutting lever out of the way to prevent accidentally burning your work in half) or a largish welding nozzle for smallish work. More usual duty is heating for blacksmithing - same burner selection as for brazing. I do occasional cutting (up to 1" plate) as well. In all cases I never need anything like full pressure, so regulators of a lower pressure range might be a better idea.

Hope that helps,

Martin

How does Oxy Propane compare with Oxy Accetelene, which is the only gas welding / cutting I have any experience of, and that was many years ago!

Propane has far more hydrogen atoms, compared to the carbons present. Carbon oxidises with far more energy release than burning hydrogen to water. Hence a hotter flame - although there is a little more to it in scientific terms.

One cannot weld steel with propane but you can get it hot enough for it to burn with oxygen.

So the difference is all down to energy density.

Martin, thanks for your response , and for taking time to go and check your equipment.

I understand that a 2 Stage Oxygen regulator gives a much finer control of the oxygen supply than the single stage one , do you have any experience of the different types ? . Looking at some of the articles on the web , it appears that the rate of Oxygen flow to propane is between 150% to 200% , do you concur with this , or in practice do you find its different , or is it all dependent on the work being done .

In my album you will see the Sievert propane regulator which I currently have . In your opinion , is it worth changing this for one with gauges , bearing in mind it was quite expensive new and has a hose fail device incorporated in it .

As you mentioned , flame arrest units are desirable and I will fit these to my kit when I get it together.

I do appreciate you , as an experienced user of this type of equipment, proffering your assistance, it’s just what I need .

The advantage of Acetylene is that it burns at a very high temperature which might be essential when cutting. But it's expensive, requires special storage and is unusually dangerous if anything goes wrong.

Propane is cheaper per litre than Acetylene and much safer. Storage is straightforward. As it also burns with more heat, Propane is often preferred because many heating jobs don't need the maximum possible flame temperature.

Acetylene can do a wider range of welding and cutting work but at higher cost and with more bother. Propane does most, but not all, things and saves money.

Dave

I have used both O/A and O/P for many years. For welding steel I always use O/A. For heating, brazing, and cutting I have the choice of O/A or O/P. I usually use O/A in the home shop, just as a matter of convenience. I don't like the bother of switching bottles. When I was working I preferred O/P for cutting and heavy heating. The cutting and heating torch tips for O/P are considerably different than those for O/A. Other than the heating and cutting tips the kit is identical for both fuel gasses.

Can I expand this to include Oxy/Propylene?

What are the advantages, if any? How long are the cylinders expected to last for use when silver soldering?

How does the cost compare?

Brian

Hello DAG,

My propane regulator is pretty similar to yours, but I note yours is marked up to 4 Bar outlet - 60 psi, so rather coarse to be getting the 2 to 5 psi you would usually expect for the fuel gas. Even my 30 psi job (no gauges and probably single reduction) spends it's life right at the bottom of it's range. I should have mentioned I also have the usual Sievert propane gear for the "fluffier" heating jobs and this runs just on a hose failure device (no pressure reducer); I haven't often seen this set up elsewhere but it was all sold to me new as a kit, so I assume it's Kosher.

As to relative consumption of propane and oxygen I haven't a clue. With dual use on the propane for the Sievert gear, and different size bottles for oxy and propane, it's just a case of set the flame up to neutral, carry on regardless and change the bottles when empty. Either way, I am not trotting down for new bottles very often.

As pointed out by others, you can't weld with propane, but it's great (and cheap) for general heating and cutting. If I had a specific job of welding, I would get an acetylene bottle from HobbyWeld do the job and then return it. It's nowhere near as eye wateringly expensive as BOC used to be for hobby use. To be honest, with MIG and TIG so relatively cheap now (Chinese electronics again), why would you want to be gas welding?

Martin

When stitching rusty cars back together it is very convenient to be able to warm metal up with a gas flame held back so it is able to be tapped down into close contact before moving in closer to actually weld. But in the general run of model engineering I agree with you.

This might be an ignorant observation, because I've never done anything with Oxygen, but do gauges matter much? Obviously they're needed to tell you when the cylinder is running out and to get the flow about right when lighting up. Once going, I imagine that the flame is adjusted by colour to get the required temperature. A oxygen poor flame is yellow, smokey and relatively cool. As oxygen is added the flame burns more fiercely and turns blue. Progressively it will be hot enough to solder, braze, and then weld. At some point adding more oxygen won't make the flame any hotter. However, if the intent is to cut, extra oxygen in the flame is needed to set fire to the steel and burn it away. Although it's quite hard to get steel burning, once going it produces a lot of heat and melts itself - provided enough free oxygen is in the flame. Presumably a welder is careful not to use too much oxygen, while a gas axe operator uses a large excess.

I'd have guessed that judging the flame and it's effect is done more by the operator than by checking gauges, or I am wrong again?

Dave

Edited By SillyOldDuffer on 25/12/2018 10:55:33

The gas axe only really needs very little fuel, if any, once hot enough to burn the metal. All a surplus of oxygen does to a flame is cool it. Think air- fuel v. oxy-fuel. In the case of the air 80% of the gas is inert and only cools the flame. No nitrogen dilution for a pure oxygen supply.

As stated in my opening post , I am looking for advice, from those with experience, in the set up and use of OXY-PROPANE . Not ACETYLENE, NOR MIG , TIG , or any other method , Nor , as I stated , to do any cutting with the set up .

I most certainly do not wish to be rude or ungrateful , and I am extremely aware that those contributing have been most helpful and have given good guidance in other threads , but please , could we stick to the purpose of this thread and restrict it to Oxy Propane equipment and its use for Silver Soldering and brazing of boilers etc up to 1/8 “ thick by about 16” long .

Dave : so far as judging gas flow and mix , I am sure , given time with the new set up , I will be able to select the pressures necessary, however , initially, I am sure that gauges of the suitable kind will put me in the right place to make such adjustments . I am fine with pure propane , but I have no knowledge of Oxy Propane , and whilst there is a plethora of advice for Oxy Acetylene, not so for the detail for Oxy Propane kit , unless you just want to buy an assembled kit at a greater cost than I am comfortable with .

Regards and have great Christmas Day ,

David .

See your second post on this thread? Merry Christmas.

See your second post on this thread? Merry Christmas.

David, I'v done 3 conversions from OA to OP, on one I think we used the regulator from an old BBQ, the other two were rush jobs with no regulator on the LPG(the last one will get one). For brazing use a larger tip than you would with acetylene. The Oxygen is set fairly low, can't remember what pressure. It is a bit more difficult to get the torch to light up, but once you have the LPG lit, slowly open the oxygen, then a bit more gas. Once you have it set up you;ll love it.

Ian S C

Hi I to use oxy pro for brazing and silver solder My oxy regulator is calibrated up to 400bar for checking the cylinder content and the low pressure gauge is calibrated up to 7bar. In my area the scrap yards use this set up for cutting scrap using a cutting torch but I use a oxy ac torch which can handle nozzles up to a no 10, for my use I use a no 3 it all depends how much heat you need, adjust the cone size to suit your needs.

You must use flash back arresters on this on this set up this is a must. For brazing you don't need a lot of pressure round about 5psi, for cutting up to 40 to 50 psi of oxy.

If you go on to utube you will get more info.

Donald W

Heat is energy; temperature is heat (energy) density. One can heat it all day long but if the temperature is not hot enough...