Oxy/Acetylene - Any cheaper alternative to BOC


Hi all
Does anyone know if there's a cheaper way of setting up an Oxy/
Acetylene welding/brazing kit, than hiring bottles from BOC.
I have the rest of the kit - burners, goggles, regulators, hoses, anti-
flashback units, etc, etc - from the last time may late Dad and I did
serious gas welding (circa 16 years ago). Back then, the bottles were
circa =A390.00 in hire charges + =A39.00 for each gas refill + delivery
and handling. A little too expensive for the occasional Model
Engineering use I need now. Trouble is, when you need Oxy/Acetylene
nothing else will substitute (I have Propane/Air torches and the "self-
blowing" Sievert kit).
What's really needed is some supply of the Oxy/Acet bottles on the
same basis as Calor Gas bottles - ie Pay a once only charge when
"signing up" and then just for the gas refills after that.
It's a long-shot I guess - BOC do like their Monopoly - but, if anyone
knows, it'll probably be one of the guys in this group.
Regards
Andy
Reply to
houstonceng
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"houstonceng" wrote
I have the rest of the kit - burners, goggles, regulators, hoses, anti- flashback units, etc, etc - from the last time may late Dad and I did serious gas welding (circa 16 years ago). Back then, the bottles were circa £90.00 in hire charges + £9.00 for each gas refill + delivery and handling.
You'd better sit down and get a stiff drink.
I have a size J acetylene and size T oxygen.
Last refills about 2 months ago were GBP 56 for the acetylene and a mere GBP 15 for the oxygen.
There was a charge of GBP 10 for the transaction (I think this is the same irrespective the number of cylinders exchanged).
Rental, if I recall from the last invoice, was about GBP 90 per year for the pair of cylinders.
Reply to
John
I don't know whether it's any help, but I use a 5 l/min oxygen concentrator with MAPP gas for small stuff. Cost £200-odd second-hand from fleabay, wait around a bit and you may find one at about that price.
Oxy/MAPP is of course not as good as oxy/acetylene, and it won't power big torches, but it works ok for welding up to 1/8" steel, and with preheating and an extra air/gas torch it will braze 1/4" + steel. I don't need to weld bigger stuff, so it was a good solution for me, but ymmv.
The MAPP gas cylinders seem to last a reasonable time, but disposable oxygen cylinders don't :( and they are very expensive unless you are doing occasional micro-work.
Disposable oxygen cylinders are however 3 or 4 times better now than they were some years ago, giving maybe 20 minutes in a nozzle suitable for brazing 1/8 steel. Only cost-effective if you only do very occasional work, however you might want to give them a try - they're not for me though.
I've often thought of building a small compressor to fill bottles from the concentrator, but high pressure oxygen is BL**DY DANGEROUS (far more so than liquid oxygen) and I haven't tried.
You can get a professionally made pump for the purpose, but at a price (ouch!) and you'll probably have to buy a new, expensive model, concentrator with it..
Another often-mentioned low-capital source of oxygen is water electrolysis, but a professionally-made outfit will cost mega$$'s, they are not particularly cheap to run, and they are only really suitable for very small torches.
I don't know of any cheap small-scale sources of acetylene, much as I'd like to - while oxy/MAPP welding is quite possible, it's nowhere near as easy as oxy/acetylene (though oxy/MAPP is fine for brazing).
-- Peter Fairbrother
Reply to
Peter Fairbrother
I have the current price list for BOC as I would like to have oxy/act set up again, but certainly not at their prices. I used to swap my bottles at work and just pay for the gas but I haven't worked there for many years. These prices are for full sized bottles (W = Oxygen, H = Acetylene); Monthly Rental: Oxy = £ 8.11, Act = £ 10.40 Annual Rental: Oxy = £ 92.47, Act = £ 118.62 If using Annual Rental, a full years rental is due BEFORE initial supply !! Gas: Oxy = £ 19.96, Act = £ 77.44 If not paying by Direct Debit an Advanced Payment of £ 75 is required. Delivery = £ 38.19 inc VAT irrespective of number of bottles. Collection = £ 12.63 inc VAT irrespective of number of bottles. Soo, try and work that lot out .... no wonder a lot of companies have turn away from BOC and Oxy/Act. Most scrapyards for example are now using Oxy/Propane from other suppliers. I could give you prices of 'portapack' (small bottles of oxy/act) if you like but they will still be expensive considering all the different charges that BOC add on. Hope this is of use to you all. Cheers Brad
Reply to
BRAD
On or around Sat, 30 Aug 2008 10:38:29 -0700 (PDT), houstonceng enlightened us thusly:
I rent 'em from Air Products. not exactly cheap, still, but a lot less than BOC
Reply to
Austin Shackles
"BRAD" wrote
Interesting. I've never seen a published BOC price list and assumed there are different pricing structures depending upon the user and annual usage.
I'm relatively lucky in having a good BOC stockist locally, and by taking the cylinders to the agent I avoid the delivery/collection charges.
Reply to
John
Then you are lucky if they don't charge it. Mine makes that charge even If 9which is always) I take the bottle back myself.
Wayne....
Reply to
Wayne Weedon
There is a published price list that lists the rental charges, along with the refill charges.
They have started doing the 3 and 5 year rentals again, which saves a good amount of money on rental charges.
Reply to
moray
"Wayne Weedon" wrote
All I get charged is a flat GBP10 processing charge by returning the cylinders to the agent.
Reply to
John
Come to think of it, you could make acetylene from carbide.
3 kg of carbide, producing 1.1 cu m of acetylene, costs £20.75, about £19 per cubic meter: if a H size cylinder costs £77 to refill, that's about £10 per cubic meter of useable acetylene,
So acetylene from carbide costs around twice as much as acetylene in a big cylinder - and no rental, more reasonable delivery fees, no return fees, and available in small quantities.
The problem then is the generator to produce the acetylene. Small capacity generators are available at around £40-50, but I do mean small. Apparently you can get bigger generators for welding for third-world use, but I don't know where from.
Making your own generator? Could be inexpensive, but I don't advise it unless you know what you are doing, and thoroughly understand the dangers (for instance it can explode all by itself, unlike propane etc., it has wider flammability limits in air than propane, lower flash point, and more) of acetylene.
-- Peter Fairbrother
Reply to
Peter Fairbrother
My late Dad and his brother had an original Oxy/Acetylene welding kit (pre-WWII) which used an "acetylene generator" and compressed Oxygen. Problem is that you have to have a low pressure torch (not a modern "Saphire" style) as Acetylene cannot be compressed without exploding. I don't know what the limiting factor is but, IIRC, the torch used circa 2 psi.
He kept the torch and oxygen bottle throughout the war - don't know what happened to the generator. When his brother wanted to set-up a welding kit again, the torch, hoses and Oxy regulator, etc, went to him. The Oxy bottle which, as I understand it, was owned by Dad and Unc was, previously to WWII, swapped for a refilled one at an agent in Carlisle where they lived at that time (ie, no rental). It proved to be NBG as it was "round-bottomed" and current bottles are "flat bottomed" so BOC wouldn't even take it away. The regulator wasn't suitable for current Oxy-bottle pressures either. To cut a long story short, my uncle did get the torch working with new regulators and such like, but it was never easy to use with bottled Acetylene - too touchy on the regulator.
When my Dad and I wanted to do some serious welding, we invested in a completely new "BOC Saphire" kit in the '60s. IIRC, we had to upgrade (by exchange) the "new" regulators when BOC increased the pressure in bottles a few years before I finally cancelled the contract - after Dad passed to the great engineerium above (1992).
Reply to
houstonceng
Chemically speaking the limit is 15 psig at reasonable room temperatures: but you should use a good safety margin, as acetylene is seldom pure and the impurities can lower the minimum explosion pressure; and the explosive limit is absolute, ie 29 psia (15 psi plus the 14 psi of the atmosphere) - however a non-explosive 7 psig torch supply *should* be possible.
Unfortunately one of the problems with this idea is that the carbide container is sometimes replenished, and when that happens air is admitted when it is opened - ouch. The explosive pressure limit for acetylene with a little bit of air in it can be much lower - a 2 psi maximum may also be used to limit the damage from an explosion, with the generator being perhaps built to withstand it.
I don't know what pressure a Sapphire torch uses, but I have a fairly ordinary balanced torch which welds okay at 4-5 psi with MAPP gas.
(There are two types of torches, the balanced and injector types. In the balanced type the fuel and oxygen supply are at about the same pressure and the gases simply mix in the nozzle - in the injector type the oxygen (usually) is at a fairly high pressure, maybe 40 psi, and the fuel at a much lower pressure, maybe 1 psi - the nozzle is built so that the oxygen flow sucks the fuel gas out. I don't know what type a Sapphire torch is)
-- Peter Fairbrother
Reply to
Peter Fairbrother
"Peter Fairbrother" wrote
FYI I have a Butbro lightweight torch which can take up to no: 25 nozzles which will weld up to about 1/4" steel.
I've just check my acetylene regulator and the output pressure gauges has the green sector as being up to 0.6 bar and the red sector starts at 1.5 bar. I believe acteylene self detonates at about 2 bar. When doing heavy work with the no:25 nozzle I find that I need to have the pressure at the top end of the green.
And before someone asks, the BOC size J acetylene cylinders are filled to 15.5 bar at 15 degrees C but its disolved in acetone and also I think the cylinder is packed with asbestos or some other material.
All flamable gases have both a high and lower explosion limit when mixed with air. Acetylene and Hydrogen are considered the worst, and acetylene in particular has a very wide band between the LEL and HEL. LELs and HELs are normally expressed as the percentage of flammable gas in air which will ignite.

Reply to
John
"John" wrote
Just checked the Safety Datasheet for acetylene. The Flammability range is 2.4-88 vol% in air.
By comparison Propane's Flammability Limits are 2% to 11% in air.
Reply to
John
It depends on many factors, including the volume and shape of the container (and the impurity levels). Butbro, and many others, may assume you only use their equipment and shapes.
The figure I gave of 15 psi is generally regarded as the figure below which it has never been known to explode.
When doing heavy
That's about 8 psig, still okay.
Yes - and the gas is dissolved in acetone soaked into the porous contents of the cylinders, rather than being compressed gas.
btw, the porous medium used is "diatomaceous earth" - which nitroglycerine is also soaked in to make the safer dynamite.
among :)
the worst, and acetylene in
Acetylene has a large explosive air mixture range, as you say later it's up to 88% acetylene in air, or 12% air - but that's at 0 psig /14psia (atmospheric pressure): increase the absolute pressure a bit and the limits change, from 12% air at atmospheric pressure to 0% air at 15 psi.
-- Peter Fairbrother
Reply to
Peter Fairbrother
On or around Sun, 31 Aug 2008 14:25:46 -0000, "John" enlightened us thusly:
hmmm. tricky. It's all done by direct debit thing, I'd need to find a bit of paper.
Mind, they recently screwed around with the distribution network. Luckily, the place not too far away continues to get them as a customer and swaps them out with their customers, even though they're not a full-blown agent any more.
Reply to
Austin Shackles
Thermodynamic calculations for pure acetylene put it at 274 kPa, or 23.2 psi (= 39.7 psia) for infinite volumes @ 25 C. A Butbro gauge which goes red at 22 psi is likely taking advantage of small volume factors and perhaps statistics as well.
I'd still stick by 15 psi for everyday use, with a safety margin.
I do this chemistry stuff in my sleep - not only can I do it, I actually do do it. I once got 99% in an exam (my chemistry O level), and furiously demanded my teacher ask the examiners to explain my mistake. They replied that they had taken off a mark for bad handwriting.
Which was - I don't know exactly what - as I had just recently blown off several fingers.
When it comes to being infallible, or very nearly always right, as is required of eg some university professors, things can get weird. For simple chemistry, for me, it was usually just a question of sanity checking my replies. No great problem.
But then I became a cryptologist instead of a chemist, and being right became different. The simple math aspect of cryptology is nice, because either the math is right or it isn't, forevermore - but the math aspect isn't everything, and there are scumbags^H^H^H^H^H fellow researchers who want to find fault in what you do. And who can sometimes even come up with better math. And of course I try and do it to them^H^H^H^H find fault with their work too, and am inordinately pleased when I succeed.
And surprisingly often work is just simply wrong, not just insecure, due to bad math, bad procedures, or bad peer review.
Sometimes you prove someone else's work insecure, and watch them gnaw their livers - sometimes someone else proves your work is insecure, and you gnaw your own liver. Which hurts, especially if you have put yourself on the line.
This is as it should be, as security is about what is actually possible, not what you, or theory, think is possible.
Nowadays for crypto work, apart from my published papers, I don't try to be infallible any more in casual talk like usenet.
But for giving practical/engineering chemistry-related advice about a possibly dangerous situation, I do take care - not that I accept any legal responsibility, I don't.
But how would I feel if someone followed my advice and lost a few fingers (been there, done that), or killed himself, or God forbid, killed some else? Not good. So I try to be accurate, and give safe advice.
-- Peter (beery) Fairbrother
Reply to
Peter Fairbrother
For me, it was the monthly chemistry tests at school. On one of them I got marked down 4% (one mark). On protest, It appeared that The teacher's preferred answer to "what is the product of combustion of hydrogen in oxygen?" was "pure water" instead of the grammatically correct "water" that I had tendered. I assume that the staff felt the need to knock down the smart alecs once in a while.
I think it was just the case that O levels were too easy for anyone with an interest in the way things work. Don't get me started on the modern abortion of a compromise between CSE and O level. The youngest has just done his :-|
Mark Rand RTFM
Reply to
Mark Rand

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