Plumbing in propane, and other propane questions

[mel]

Hi all,
At the mo, my propane is indoors but am thinking of shifting it outside. I currently have a combined regulator and flashback arrester which a welder gave to me-but one without a pressure gauge.
When we had a cooker fitted (bottled gas), we had to have a gas plumber to do the necessary so I am assuming the same is true for other gas installations. If I get my propane put outside, what sort of pressure should I be asking it to be set at? I presume a plumber will have a standard set up for cooker pressure, with flashback etc? will this suffice for a torch?

Secondly, one of the reasons for doing this is to get a bigger bottle, and then get a wee 3.9kg portable bottle for demo-ing at a couple of local events.  Is the gas at the same pressure in a smaller bottle? i.e. would it run a torch? I'm probably being uber-dim, but it's going to cost a bit, so want to get it right.

Any advice out there?

[Blue Box Studio]

No idea about pressures, I just bought all the bumph from Tuffnells including the regulator and plugged it in, but I started with the tiny 3.9kg bottle and it worked fine for the Hothead and the Minor.  I kept it as my emergency spare for a while then swapped it for something larger.  I assume (got thrown out of science class, the nun didn't like me) that the regulator is the thing that controls pressure?

[Moira HFG]

Mel, the working pressure should be marked on your regulator somewhere, unless it's rubbed off - mine is 4 bar, which I believe is about standard for a torch.
You would want exactly the same regulator for any size propane cylinder.

(Sue - you're right, the regulator steps down the pressure in the cylinder to your working pressure.)

Moira

[ajda]

It does slightly depend on your torch. A Hot Head is designed to run on full tank pressure, while dual fuel torches generally prefer lower pressure - but optimum pressure may be different for different torches. An adjustable regulator is the best bet, then you can experiment with different settings until you get it running to suit you and your torch. A standard adjustable regulator will probably give you a range of between 0 and 4 bar pressure, which should be all the scope you need - and Moira is right, it shouldn't matter what size cylinder. I have a 19kg at home and a 6kg for travelling and just switch the regulator from one to the other without a problem.

[bearyboo]

You should be fine to use the same regulator, but I think it needs to be a 4 bar regulator. When I got my set up, I went to the local gas shop and they tried all different regulators on my torch as I took it with me. They started at 1 and worked their way up. The torch would only light on the 4 bar.

Having said that,you may need a different regulator if it is going outside as you need one that will withstand all weathers.

As for having to have a plumber plumb in all gas installations, unless it is coming if a main gas supply then I don't see why you would need a plumber to do it. All you need to do is connect it all up yourself.

As for the flashback arrestor, I have not got one of these nor have I ever used one. This is through my choice as propane is a low pressure gas and the risk is vey minimal. I would like to clarify that I am in no way saying that you do not need one, it is my choice not to use one.

Danielle

[mel]

Many thanks for that, I probably could just plumb it all in then. Interesting what you say about the FB arrester, my neighbour has been burning lead as a roofer for donkeys with all sorts of torch equipment and gases and wasn't convinced about the need for one, hence I borrowed a combined regulator/'arrester'. However, I'm hoping to teach a few workshops, so should really follow best practice.

I sort of thought that different bottle sizes would deliver similar pressures, so it's good to get that confirmed.

I'll cruise the regu;ators at BOC then and aim for 1 to 4 bars.

[Moira HFG]

You only need a flashback arrestor with an oxygen/fuel set-up. There's a chance that the flame can be pushed back down the fuel line, with explosive results. Best to have one, I think.
A roofing burner will be sucking in air at the nozzle, like a hothead, so you don't need an arrestor for that.

[bearyboo]

I have a dual fuel set up and I have never had any problems without one. When I put my torch together, the people at the gas shop said that as it is not bottled oxygen, you do not actually need one but you can put one on as a safety precaution. But as I said, it is my preference not to have one.

My partner is a fabricator and he uses an oxy propane torch at work that is very similar to the torch I have, also known as a gas axe, and they do not use them on their bottles. Like your roofer friend, he also does not see the need for one!

Danielle x

[oliver90owner]

Flashback arrestors are a good back up for any gas line, but with a surface mix burner it is fairly inconceivable that the two gases (one fuel, one oxygen) are going to mix, then go back in the lines.  Start-up, with air in the gas pipe, is the most likely time for a pop.

Pressure has nothing to do with a liquid gas bottle size; it is simply the vapour pressure of the gas at any particular temperature.  Propane bottles can lose pressure by cooling the liquid too much - ever seen propane bottles at high discharge rates where ice forms on the outside?  Not usually a problem for a single torch for lampworking.

Pressure has nowt to do with necessity for flashback arrestors either; they are universal on acetylene lines as there are other safety issues with that gas, almost universal with propane brazing and cutting torches (internally mixed) but almost unheard of for plumbing and roofing burners.

RAB