This sounds stupid but

The square valve on the BOC gas bottle that opens / closes the supply to the regulator. I generally open it about 1.5 to 2 turns. Is this too far / not enough and more to the point will it fall out / blow out it I unscrew it too far. 2 turns works for me but may not be correct !!

What I do is open the cylinder valve until the regulator gauge shows pressure, then I open it a little bit more (quarter turn more).

Works for me!

David

Not a daft question at all....

I'm almost certain it won't come out...that would be VERY dangerous...I'm sure it's travel is limited like the taps on your kitchen sink....

So, I'm sure what you are doing is fine, also what David says is fine too......ISTR opening them up about 1 turn, but it's 9 years since I used a UK gas bottle (US ones have a hand valve)

Thanks Alan

Maybe not so daft but it's like some many other things you have been doing for a while but not really learned the proper way of doing them.

Your way works for you but you are never sure if it is right / wrong or doesn't matter at all ......

I've been welding for a lot of years, I have never unscrewed the peg more than 1/4 turn. Alan is probably right, it is almost certainly safe to undo it several turns - do you really want to test the theory, let me know the results ( no don't, 3000 psi don't bother).

On a safety point of view, as a baby welder on day release, we were told never to undo the valve more than 1/4 turn (applies to sexy ahotaline really), because if you want to turn it off in a hurry, one good belt with you fist will shut it off (always leave the key in place on a lanyard). Argon is not dangerous - BOLLOCKS. I have had a LP pipe blow where it enters the welder, the thing thrashed about like demolition flail. Hit me in what I typed in capitals earlier, smashed my EW13 lens, knocked the glass cover off the reg valve guages, all in the time it took me to say FU....

I watched a safety video on welding cylinders when I first learnt to weld. This admittedly was on oxy-acetylene welding but the acetylene cylinder is full of a catalyst which holds the gas in a liquid form and releases it as it turns to gas when the cylinder tap is opened not as a result of it being pressurised but as a result of a reaction causing it to expand. The oxygen cylinder, at that time pressurised to 2000psi, was placed in a jig and the tap broken off by a guillotine causing the cylinder to fly off like a missile and demolish a two brick thick wall about 20 yards away and come to rest about 50 yards away. If the valve was not secured you would be in very grave danger of losing part of your anatomy or killing anyone in the line of fire. I don't think BOC would leave themselves open to accusations of being criminally negligent by not securing the square firmly in place. Does the top come off your bath tap if you open it fully, or haven't you tried that one yet either. I use an Energas cylinder which has a wheel and that stops when it's fully open as I tried it when the cylinder ran out, but there was still none left.

yours, Pete.

P.S. anybody got a boc account I can get my portapak refills on?

Nope my bath tap does not come off when I fully open it. But then my bath tap does not as everyone points out control 2000 psi or more of compressed gas, so the results of that experiement (if you use the cold tap) are potentially less damaging and painful.

As for BOC leaving themselves open to accusations of being criminally negligent by not securing the square firmly in place, well, lets just say it never stopped several other large corporations. They just get off on the clause of " to be operated by qualified persons only" or "fully read and understand operating instructions prior to use"

maybe a daft question, but unless you ask it you never get an answer !!



(not in any way suggesting BOC operate in this manner)

Wait till it runs out, then try it..

yours, Pete.

I had it "knocked into me" at college that no more than 1/4 of a turn is all that is needed,until you hear it go "psh-u"and that is it..any more is too much..imagine your acetylene hose getting a hole in it and you trying to turn that square peg in 5 or 6 full turns...don't want to be near your back yard when it happens...

right scared me enough people 1/4 turn it is, key on lanyard and if (just maybe) the square plug could come out I am not going try and find out (even when the bottle is empty). Some things are best not known.

end of discussion as far as I'm concerned

thanks

Very sound advice about cylinder saftey everyone.
Have also seen video of gas cylinders with valves knocked , BUT what was really scary was what happens to anything that gets touched by the escaping Oxygen.

Nerd time .. Pete Acetylene is soaked into charcoal in the cylinder as it can absord many times more liquid than in a pressurised gas state.

Seems like my fears were well founded

quote from "Safe Under Pressure" BOC publication:

BOC permanent gas cylinders are all fitted with cylinder valves in which the spindles have collars to prevent them from being completely unscrewed. There may however, still be a few acetylene cylinders which have not yet been returned for this modification. So as a general rule for acetylene cylinders never turn the spindle more than three revolutions.

so any gas welders out there beware

[Edited on 3/12/03 by givemethebighammer]

Acetylene is a 'liquified' gas dissolved in a catalyst (charcoal) not a 'permanent' gas (unliquified) under pressure and is your cylinder an acetylene cylinder or a CO2/Argon mix for mig welding? You did not mention what kind of gas in your original post.

yours, Pete.

I know my gas is CO2 / Argon just trying to illustrate that the value could come out if loosened to much (and would if you have and older BOC bottle). The type of gas is not relevent.

[Edited on 4/12/03 by givemethebighammer]