Oxygen question

Started by jeannette, May 24, 2013, 06:59:39 PM

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jeannette

Hi -

I was going to open an old topic, but the forum said - "it's a bit old, love, why not open a new topic" and I'm easily led, so I did.
This one http://www.frit-happens.co.uk/forum/index.php?topic=10303.0

I keep reading around the place that everyone is pro-oxycon and I understand the reasons, but I'm trying to do the maths to see if the oxycon makes sense from a cost perspective. If you are using O2 - how much do you use an hour? Is it flowing at 5LPM?
Also, I want to share the setup with him indoors for braising, he uses a oxy-propane mix, so is it the same?
Any experience in the welding/braising cross-over to lamp work gratefully received!

Thanks
Jeannette


June

Bottled oxygen is pretty expensive. I can't tell you how much you use per hour suffice to say that we had cylinders that were about shoulder high that were around £30 a time to refill (that's not including the annual rent of the cylinder) and it lasted about a month when I was at the torch during weekend afternoons only. The cylinders go down much quicker than propane. On the plus side, bottled burns hotter than an oxycon.  :)

Redhotsal

If you have oxygen on the premises then it is a luxury that most bead makers can't afford so you can make the most of it. Bottled oxygen is expensive - last time I bought any - which was YEARS ago, I was paying £80 per cylinder rental (W size) and £35 per delivery PLUS about £30 per new cylinder "refill". So, even if you only use, say three cylinders a year, each separately delivered you're looking at about the same cost of an oxycon. The downside of this is that you'll need two cylinders on the presmises at the same time - 'cos there's nothing more inconvenient when one runs out. Then you have the sheer inconvenience of them. A W sized cylinder is about 5 ft tall and incredibly heavy - if you have steps then it will be horrible trying to hump them up them. Most "normal" sized women will struggle - I certainly couldn't lift one (though I could "walk" one along a level surface). PLUS you have to properly restrain them (chain them up) and get a two stage regulator and flash back arrestor...........

Now - if you have all this if your OH is a welder then you can just piggy back onto his supply and save time and expense, but presumably you will need to "tee" off a connection to your burner. Bottled oxygen doesn't have a "flow rate" as such - it has a pressure, suffice to say that your bottled oxy will deliver a lot more "umph" than an oxycon - certainly sufficient to do something which requires a lot of heat - like borosilicate. So, in many respects it is far superior to the oxygen that an oxycon can deliver.

But, yes, it is expensive. Can't say how many cylinders you will use as it's a "how long is a piece of string" type question, but as a moderate user about ten years ago I worked out that it was costing me about £500-600 per year in oxygen. But then if your OH is paying........  ;)

One other thing - people who use bottled oxy soon learn to turn it off when you don't need it - unlike oxycon users who will happily wander off and put the kettle on while their torches are still lit.  ::) Which, of course I would NEVER recommend anyone to do.......!


June

A much more detailed answer than mine Sal  :). Suffice to say I used to be on bottled and now have an oxycon  :)

jeannette

Thanks, both.
Did you use a two stage regulator? I'm just wondering about your mention of pressure, not flow rate.
I'll just give it a bash and put a gauge on after a session, I think. I'll know how many litres an hour from there.
Cheers.

Redhotsal

You will almost definitely need a two stage regulator - for reasons I can't actually remember late on a Friday night. Someone did explain it to me once but I can't remember why - it's something to do with dropping the pressure down in two stages (as opposed to one - like on your propane line) - which basically means the pressure of oxy to your torch is kept constant without any "droop" in pressure.

I would really not think of things in terms of litres per hour - "flow rate" is a bit of a nonsense term when it comes to pressurised gas. Flow rate is only really meaningful to a non pressurised (or low pressurised) system such as you get in an oxycon  - you'll use a variable amount of oxygen anyway and it will depend on what pressure you set the regulator to - which depends on your torch. The best way to guage the useage of a cylinder is to see what pressure is left (in Bars) on the regulator - you'll soon know when you are running out and the drop in pressure of the tank over a beading session can then be extrapolated out to estimate how much time you will get out of a tank. Basically one gauge on the regulator tells you what pressure you are supplying oxygen to the torch at and the other guage tells you how much pressure is left in the tank.

If your partner welds he will have a two stage reg on the cylinder anyway.

Don't be tempted to think of oxygen as a friendly gas - okay - it doesn't actually "burn" but it can cause other materials which get "soaked" in it to burn at an astonishing rate. Any leakage is very very hazardous - because unlike propane you won't smell it or even know that there is a leak. Treat it with at least MORE respect than you would propane and you MUST use a proper pressurised and armoured hose to run to the torch. Never use a PVC hose like that on an oxycon. Always, always, use a flashback arrestor - because there is a proper chance of a flashback with pressurised oxy - even with a surface mix torch, becuase of the higher oxy pressure. You must have the bottle properly restrained by law - if it gets knocked over and the valve is damaged it will knock a hole through a brick wall, no trouble. I don't want to frighten the bejeebers out of you but seriously if you don't have any experience with pressurised gas please make sure you set everything up in the company of someone who has had some experience or training. 

Redhotsal

Just another couple of points:
You will need a flashback arrestor for propane and ALSO for the oxygen line. You can't use a propane flashback arrestor in the oxy line.
The oxy line will have right hand threaded fittings and the propane line will have left hand threads. This is to stop people using oxy fittings on propane lines and vice versa, so you won't be able to use a propane flashback arrestor anyway on the oxy line. Unless you have all of this kit (which I would assume you will have if your partner welds) then it is an expensive option to buy all of this just to test it out. last time I looked an oxy flash back arrestor was around £30.
Hope this helps.

DragonBright

Sal has pretty much covered it, but from a previous life working (occasionally) with oxygen, depending on exactly how himself is using the supply, if you're both running at the same time, you may find that your torch pressure fluctuates a little.  This may not bother you, and judicious use of second stage regulators will minimise the problem.

If you're looking for hosing etc, try United Welding - http://www.unitedwelding.co.uk/ .  They're super-helpful, and if they don't carry what you need, they'll be able to point you to someone who does (and not for silly money, either!).
DragonBright: quality tools and accessories for craftspeople - visit us at www.dragonbright.co.uk.

Ian R Pearson

Just catching up with this subject. I use a W size cylinder cost in Nov 2012 was £21.38 plus VAT of course and a little "Enviroment and Energy" surcharge as BOC like to call it. Of course rental is extra. I have used double stage and single stage regulators. At moment a single stage is on but pressure does alter slighty especially when nearly empty. Running at 2 bar pressure seems fine for me. Only use one cylinder and time it so order replacement nearly when empty.

Ian