pub gas plus regulator confusion

[beanis]

Hi,
Sorry for what is probably a simple question, But i've just got a mig welder with a bottle of pub gas. it has this regulator on it:

It says argon 3 - 5, and i seem to be able to regulate the psi with the tap on the top.

Now being an idiot, i used it to what it was set to when i bought it, this being WIDE OPEN, at stupid amount of psi. i thought it sounded loud. Anyway now i've pretty much used all the gas up and need to refil it, as the needle only moves a bit when gas is wide open.

I rang up a local supplier (Parflo) in Altrincham and he said something about drilling out the return valve if it had one?
I'm pretty confused.

1. what psi/bar should i be using for welding?
2. how will i get it filled up? Do i need to drill anything out?
3. Opon what psi in the bottle dopes it need refilling, ie, when can i tell it is gonna run out.

sorry, i have searched forums but can;t find answers to these questions

 

[the snooper]

you should be using around 10 litres per minute

that guage tells you the pressure in the bottle and pub bottles are pure Co2 with an external thread yours has an internal thread
there should also be an indication printed on the regulator in litres per minute

 

[hairymel]

hey beanis

it all can be a bit confusing

i have only a bit of experience but will give my tuppence worth until someone more knowledgeable comes along

first thing that strikes me is the bottle doesnt look like any of the pub co2 bottles i have had - it seems to have the same valve fitting as an argon type bottle

if you have a look here http://www.weldequip.com/regulators-gas.htm

your reg fitting looks like the ones for argon whereas i would expect it to look like a co2 fitting (ie your bottle has an argon type fitting rather than there being anything wrong with the regulator)

all that aside



the psi reading on your reg shows the bottle pressure - for co2 this stays at 50bar-ish from full until its almost empty (the co2 is stored in a liquid form)

for argon a bottle will be anywhere between 130-230bar depending on fill pressure and this will fall in direct relation to the gas left.

a 2 gauge regulator usually shows outlet psi or the gas flow on the second gauge

your adjustment control on the reg should have some markings somewhere and you should set it to around 10 litres per minute or a bit less (see the forum tutorials at the top of the page for more in depth setting up guides)

if no markings are present you can get get a flowmeter like on the weldquip page

or for a very rough setup just connect it all up pull the trigger on the mig (without actually striking it on anything) and adjust the reg to hear a very very gentle shoosh noise from the nozzle of the welding gun

return valve - not sure - possibly he has come across gas bottles with a non return valve to prevent refilling- i think some of the disposable bottles have this.

DO NOT start drilling anything!!!!!!!!!!!

put up a pic of the bottle from the side and have a look for any identifying markings.

hope this help a bit

mel

 

[rtbcomp]

You've obviously got the right gauge for the bottle, if you can regulate the pressure with the tap on the regulator then the gauge is reading output PSI, not bottle contents.

You need to replace the bottle when gas stops coming out.

A cheap pea-shooter type flowmeter is a good a way as any to check the gas flow.

The bottle should be marked with the type of gas it contains.

As Mel says - do NOT start drilling anything, if your gas supplier suggested you start drilling into valves &c on a gas bottle he wants shooting.

 

[beanis]

Ok, thanks for advice. I wasn't going to drill anything to be honest, sounds mental.

I think i've worked it out. When tap on regulator is turned off, and i open the tap on top of the bottle, it shows me the pressure of bottle in PSI. This is how much is left.
When i turn tap, i can regulate PSI, it has little notches under it like you said, and i can make it about 15psi for welding, sounds good.

The bottle is murphey brewery ireland! it says 70%Nitrogen30%CO2 - i imagine this has been filled with pure CO2 though.

I'm gonna take it to somewhere and just see if they can fill it, i'm not drilling anything.

Last question - At what BAR pressure should I replace, when will it run out? It was on 150BAR or something, now it dropped quickly almost down to 25BAR.... I need to do a bigger welding job next monday, so just wondering if its worth letting it all out now and refilling this week, don't wanna be stuck half way through a job.

 

[the snooper]

those bottles usually have 50 bar in them how does it weld ? can you be sure it doesnt have the original gas in it ?
also you dont set gas by psi as there is no pressure to speak of it should be set in litres per minute so if you dont have this measurement on the regulater then you could do with a flow guage.

as for your question when will it run out, when the guage reads zero pressure

 

[hairymel]

if it has nitrogen in it its not really suitable and a reputable firm should not refill with a different gas.

pure co2 will not ever be as high as 150bar - my experience is it showing 50bar (usually) but it may (possibly) go a bit higher 60-70bar if its warm.

because co2 is stored as a liquid its pressure will stay almost constant as it is used (ie full 50 bar and almost empty 50bar) the pressure will only start dropping when all the liquid co2 is gone and then pressure will rapidly drop off as the last bit of gas is used.

dont let the gas out - take the bottle and regulator and see if anyone can/will fill it for you - worst case is you vent it in the car park


edit/

beaten to it again

only way to be sure of how much gas is in the bottle is-

find the tare weight stamped on the bottle and then weigh the bottle (minus the reg)

the difference is how much gas is left if you work on the principle that 1kg of co2 = 500 litres at room temp/pressure you won't go too far wrong.

then divide the figure by 10 to give your welding time (only if your flow rate is set right)

 

[beanis]

hooray i just had it filled at Parflo with argoshield.

Now its registering at about 100 bar or a bit less.

I think i'll regulate it by guessing to be honest, i'll do some test welds.

Thanks for all the help!