Filling pressure???

[pin]

Wasn't meant to be as flippant as it came across

 

I wouldn't have thought you'd want co2 in there, the argon is heavier than air but is completely inert so shouldn't harm things. I would be concerned over the moisture / filtration.

[No Dosh]

CO2 is much more susceptible to changes in volume (and therefore pressure) with temperature fluctuations. Fill it on a cold day and when it warms up the gun could end up over pressure and you will blow a seal (no, not the that sort of blow and not that sort of seal either). There's also an issue with argon, which has a 50% larger molecular size than oxygen and similarly slower expansion rate when pressure is released, as has CO2. By having a high concentration of these denser gases your muzzle velocity will drop through the floor (CO2 guns have larger transfer ports to allow for this).

 

Remember that normal air in a diving bottle is mostly Nitrogen and Oxygen (similar expansion rates) and has been filtered to within an inch of its life as it is used for breathing. Can you say the same of the contents of your welding bottle?

 

If you fill your PCP with anything other than compressed air you are at best going to see a marked change in the performance of your gun (up or down), damage the seals and possibly cause corrosion and at worst end up seriously injured. Most PCP manufacturers make it very clear on their websites that you must NOT use anything other than compressed air or you risk injury and will invalidate your warranty.

 

In short, don't do it!

[SNAKEBITE]

Jesus wept

I know a couple have gone the nice way of saying not to put anything else but compressed air into a PCP and I will try to be a bit gentle as justme is a new guy on the site but.......................

 

DON'T ******G DO IT!!!!!

 

Anything else than compressed air is bad and will lead to problems.

 

Have a word with Ben Taylor the airgun guru and see what can happen when you do this, no infact ask for pictures of the Rapid he has in his workshop.

 

If you want to do it then go ahead and do it, just make sure you get pictures. It might help your case for the Darwin awards.

 

Oh and don't write about it on here as you might give others ideas ......................................

[justme]

Ok so its a bad idea then. But I have just remembered I have a spare welding bottle that I could get filled with air at the local diving center assuming they would be willing & have the right connectors. What sort of connector do diving bottles have?

 

Justme

 

PS post the pics then might be interesting

[roblade]

Ok so its a bad idea then. But I have just remembered I have a spare welding bottle that I could get filled with air at the local diving center assuming they would be willing & have the right connectors. What sort of connector do diving bottles have?

 

Justme

 

PS post the pics then might be interesting

 

I would love to be in the dive shop when you ask them this :lol:

 

If you think we are a bit harsh here, you try asking that questin in a RW diving shop

 

have you aver heard of the darwin awards? you seem to be a prime candidate if you carry on as you are.

 

ROB :(

[justme]

I would love to be in the dive shop when you ask them this :lol:

 

If you think we are a bit harsh here, you try asking that questin in a RW diving shop

 

have you aver heard of the darwin awards? you seem to be a prime candidate if you carry on as you are.

 

ROB :(

 

Why? The cylinder is a current model thats tested as suitable for filling with compressed gases to a much higher presure than diving cylinders so there is no safety issue with the filling. If there were then every welding shop in the country would be out of work & BOC & AIrd products would also be out or work. I guess the dive shop might not WANT to do this as they would want to sell me a bottle but safty I dont think so.

 

 

So far I have found this site full of nay sayers & people that would rather make a joke than impart sensible factual information. If you dont KNOW then dont post.

 

Justme

[pin]

You asked a question and people were nice and said it was a bad idea. You got a more thorough answer which dealt with the more technical aspects. What exactly do you want from us? Do you want someone to say its ok to do this and won't harm the rifle? Ain't going to happen.

 

Ask any question you like, don't like the advice? Don't follow it.

 

Jesus, some people.

[justme]

Well so far the advice I have been given is you could fill it with jelly or water (but I would not) or that I should stop procreating as I am to dumb to produce viable ofspring. Hardly technical replies.

 

The bottle I have is tested & stamped to 400 bar & is designed for holding gases so quite how this is dangerous or an aplication to the darwin awards is beyond me. I can see that using non designed gases could be a problem which is why I asked (& to some extent received a tech reply). But filling a desgned cylinder with designed gas (diving air) hardly merits the responces I have had. After all its only the same as you all do but with a bigger & heavier / stronger cylinder.

 

 

Justme

[roblade]

ok now for the technical side of the answer, but unfortunatly i have very limited experiance, im sure someone will be along soon with a little more knowledge than i.

 

Ok you say the cylinder has 400bar stamped on it has a it got a valid test certificate? has it been hydro tested? has it had a visual inspection? Is the 400bar test presure or SWP? what type of thread is on the bottle? how old is it? what has it been used for previously? last but not least, would you be happy to strap it to your back and breath 100% of the contents??

 

Divers bottles have been produced with one job in mind, as have most things on this planet, to use them for airrifles, the air rifles have been designed around the bottles.

 

To want to use a third party bottle would be like using a plastic bottle to carry a couple of litres of petrol in, it could possible do the job but then again it could possible, litteraly, just blow up in your face.

 

Divers bottles have one of two contector type valuves fitted, either a din type crew in fitting or an "A" clamp clamp on fitting.

 

Reading back through your posts you seem to have a head on your shoulders if you want to keep it there i woudl think you would want to keep it there, so please dont take any of what has been said on this thread as anything other than good advice.

 

I still stand by what i said I really would like to be a fly on the wall in the dive centre were you to ask them in person if they would be willing to fill your "non breathing air" bottle LOL

 

ROB

[justme]

Thanks for your frank reply Rob. In reply to some of your points I dont know. To others I do. Like the 400 bar is safe working presure. The bottle was in use recently but COULD have been close to its end of test / life & I have no way of knowing to be honest. I suspect that the dive center wont have the correct adapter to fill the bottle but IF it was possible & SAFE I would have bought what ever it needed to sort it as it would have been cheaper than a bottle. My primary need / want was to use the welding gases as I have them avaliable all the time & extra cost would have been nil with 100% avaliability. As I then received GOOD advice that it was not a good idea mainly due to moisture & dust (which i accept as GOOD reasons) & some concerens about the gasses involved (again I accept the problems) I though about my empty bottle getting filled with the correct gas (air) & correctly filtered / dried getting past all those problems. I think I have heard that testing is about £25 so even adding that in its still cheaper than a bottle. As my bottle is much larger & dive centers seem to charge per fill & not by size it would make refills VERY cheap. But like you said the biggest problem would be the dive center not WANTING to do the fill. My adapter for the hand pump has just arrived & to be honest pumping up from 150 to 190 bar was very easy (most of the pumps was to get the pipe work up to the 150 bar) with the logun pump I have (are logun pumps any good?). Unless I start to use LOADS of pellets I doubt it will be worth the cost going down the bottle route.

 

I like good advice as long as its based of facts & figures for a good reason and not prejuces. I dint want to spend money just because no one has thought about doing it that way before.

 

Once again thanks for ALL the comments as free & open descusion is what its all about.

 

Justme

[roblade]

just curiouse but what size bottle is it? (how many ltrs capacity is it?) i have seen some long thin airgun bottles (5' tall, side by side you could mistake them for a welderss set) but just becasue they are tall and thin does not mean they hold more air than a 2' dumpy bottle. I have seen both and they are both 12ltr capacity.

 

Dont forget you would have to get a replacemt valve for the cylinder which would be roughly another £25 second hand.

 

Haveing used several pumps myself, i know they really are not as bad as some people would have you belive LOL I used a webley pump (fx pumps are the same) and these are probably the best i have experiance of (tried a logun and a hills as well to compare). Used my pump on my career up to 250 bar!!!!! I needed a good cup of coffee after but managed to do it without puffing and panting too much LOL

 

as for the reason some people, myself included, tend to jump up and down when people say what about filling my rifle with..." 99% of the time they are muppets and its justa lot quicler to type DONT EVEN GO THERE YOU MUPPET!!!!!! So dont mind us a good discusion is fun sometimes and that way you will walk away happy knowing the reassons behind the statements.

 

I am normaly the first t jump up and down ungabunga styel, but am also the first to admit when im wrong (see hw95 thread).

 

ROB

[justme]

Having looked at the web site (& some forums) it looks like its a 20L size. But I cant be sure as its hard to work out as diff gasses in the same bottle have diff capacities. I think divers bottles are sized on how much water they hold whilst welding ones on how much gas / liquifed gas they hold. Do people dive with the 12L? If so I doubt its the same as this bottle would sink a small row boat. Must weigh about 40-50KG empty. Will look at the bottel & see if it has any size markings on it. It has a on / off tap built in but would need some sort of more sensitive valve. I do have spare regulators that I could take the connector off to fit to a inline valve & gauge as it has a standard screw thread (well standard for welding kit). The bottle is about 3 foot 6 (100cm) inch high & about 7 or 8 inch (16.8 - 19.2)diamiter. Been trying to work out some capacities using the size but it only comes out to 5.2L to 6.03L (diamiter x Pi x hight) which seems very low. Looking at the bottle I would have said about 15-20L. All the diving bottles I have seen are only about 2 foot 6 max by about 6-7 inches but then I not seen many. i guess the wall thickness of a diving bottle is quite thin as its expected to be looked after whilst a welding bottle isexpected to be dropped & bad handled.

 

 

Justme

[Recurve]

Yes people dive with 12L cylinders (you are right, it is water capacity)

 

If your welding cylinders are purged well enough of the gas they previously held and in test, then in theory there is no reason why a dive centre wouldn't fill them. If they had welding oxygen in them, then they wouldn't need purging, just emptying. Lots of divers use welding oxygen for blending in breathing gases, so don't worry about the purity/moisture content. The centre might want them painted in the correct colour for air (black and white segmented neck). However if it's an acetylene bottle then forget it, as they are full of capok I believe.

 

The practical aspects of connectors is a diferent matter.

 

Hey, go ask your local dive centre, the worst they can do is laugh you out the shop.

 

Oh, and kids, don't play with high pressure oxygen unless you REALLY know what you're doing, it will lead to a whole lot of pain.

 

And to work out the volume from sizes, it is Pi x radius x radius x height (radius being half the diameter)

[justme]

So if I have done this right its:-

 

pi x 10cm x 10cm x 100cm = 31415cm cubed which is 314L

If its the 8 inch size

 

or

 

176L if is 6 inch

 

 

Justme

[Recurve]

So if I have done this right its:-

 

pi x 10cm x 10cm x 100cm = 31415cm cubed which is 314L

If its the 8 inch size

 

or

 

176L if is 6 inch

 

 

Justme

 

Close, but there are 1000 cc's in a litre, so it's 31 litres or 17 litres.

[justme]

LOL

 

thought that sounded far to high.

 

 

Justme

[Gary]

Hi Justme,

 

CO2 at pressure is a liquid and I think you'll find that CO2 bottles are thinner/lower rated because they are pressurised at much lower rates than O2/Air, Argon and the like. CO2 and O2/Air aren't interchangeable. Also, because CO2 is a liquid at pressure and as someone has said, if you have a half filled bottle and the tepmeprature rises your CO2 vapour pressure will rise as well.

 

So, if you put liquid CO2 through your PCP valve it will probably knack it or the gun will be under extreme pressures as the CO2 boils off. I don't know but I'm guessing that the pressures in the gun valve are relatively low compared to the pressure of boiling CO2 (I think CO2 boils off at 860 psi which is about 60 bar), the point being that if liquid CO2 gets into the PCP gun valve and it's boiling the vapour pressire will rise inside the valve and could exceeed the guns normal working pressure.

 

As someone has said the Acetylene cylinders are filled with capok.

 

It would be easy for anyone just to say "For **** sake don't do it!" but sometimes finding out why you shouldn't do it is much more fun and much more interesting

[justme]

Hi Justme,

 

CO2 at pressure is a liquid and I think you'll find that CO2 bottles are thinner/lower rated because they are pressurised at much lower rates than O2/Air, Argon and the like. CO2 and O2/Air aren't interchangeable. Also, because CO2 is a liquid at pressure and as someone has said, if you have a half filled bottle and the tepmeprature rises your CO2 vapour pressure will rise as well.

 

So, if you put liquid CO2 through your PCP valve it will probably knack it or the gun will be under extreme pressures as the CO2 boils off. I don't know but I'm guessing that the pressures in the gun valve are relatively low compared to the pressure of boiling CO2 (I think CO2 boils off at 860 psi which is about 60 bar), the point being that if liquid CO2 gets into the PCP gun valve and it's boiling the vapour pressire will rise inside the valve and could exceeed the guns normal working pressure.

 

As someone has said the Acetylene cylinders are filled with capok.

 

It would be easy for anyone just to say "For **** sake don't do it!" but sometimes finding out why you shouldn't do it is much more fun and much more interesting

 

Er not sure you have been following this closly. I am not planning on using CO2 (but did think about using a gas blend containing co2 in small amounts till advice on here guided me away). Also as you say co2 presure is about 800psi PCP guns use 3000psi cant see that getting damaged by the low presure co2 as even when boiling off it cant go over that presure. Any way to put an end to this having been using the gun now for a while & hand pumping it I have found that either people complaining its to hard to hand pump are whimps or I have a easy gun / pump combo. I fill to 190 bar (as per hand book as not had time to work on sweet spots yet) & try to refill at about 100 bar / 50 odd shots (I am not saying that 50 shots get to that presure just that thats how I am doing it at the min). Re pumping takes about 70 pumps once the line is charged up.

 

All those points about co2 & tempreture are why I dint go for a co2 gun in the end.

 

Justme

 

PS the bottle i have is far heavier & thicker than diving bottles & is the same bottle used for all industrial gasses (except ones like aceteline). I would estimate wall thickness to be 10mm plus.

[pin]

Just a tip, you might already be doing this, if it takes 70 pumps do it in at least two preferably 3 sets of effort with a couple of minutes in between to allow things to cool down. You will end up with more air in there for the same effort.

[Gary]

Er not sure you have been following this closly. I am not planning on using CO2 (but did think about using a gas blend containing co2 in small amounts till advice on here guided me away)

 

That's why

 

The other thing is about ******* the gun: If you fill the valve with liquid CO2 and then let it go into a primed barrel you have x ammount of CC's of rapidly expanding liquid at 860 psi behind your little pellet, the increase in volume would be massive and would continue to expand (as the CO2 boiled) as your pellet moves down the barrel, accelerating it all the way. Pellet velocity is constantly increasing and a wedged pellet could cause quite a few problems in a valve/barrel not used to that kind of back pressure.

 

That's my theory anyway I still don't see why you couldn't use any other stable inert gas though, like Argon or better still helium... You could make silly voices if your buddy bolttle valve leaked as bad as mine does

[justme]

Just a tip, you might already be doing this, if it takes 70 pumps do it in at least two preferably 3 sets of effort with a couple of minutes in between to allow things to cool down. You will end up with more air in there for the same effort.

 

Hi,

As its only take less than 1 1/2 mins to pump it up I'm doing it in one go (I had read that its best to do it in small bursts due to heat but its not been getting hot). The valve block is not getting warm in that time. I then tend to wait a few mins & give another pump or two to bring it back up to the 190 bar (it only drops a small amount).

 

Justme

[pin]

Good, but with a modest increase in air temperature your 190 (which is too much, try 180) will be more like 170 when you look the day after..

 

Not trying to teach granny to suck eggs, just saying..

[justme]

Good, but with a modest increase in air temperature your 190 (which is too much, try 180) will be more like 170 when you look the day after..

 

Not trying to teach granny to suck eggs, just saying..

 

All advice welcome. Wont an increase in temp cause an increase in presure due to air expansion not a drop? Would have thought the drop was more due to a leak or the air chilling after the pump up or loss due to the air feeding into the filling valve (I have to connect to the pump to see presure). Only been using 190 as the manual recomends it. Do notice that power picks up after a few shots. They (the makers) recon on 70 plus shots but I am doing about 40 plus before filling. How low is it safe (for filling problems & for shot power) to go before hand pump filling? IS it true that below 50 bar the valve wont seal? The manual says to put the bolt in the rear postion to remove the presure on the valve from the hammer whilst filling from low presure. Dont want to get it so low I cant hand fill.

 

Justme

[Ferret Master]

On my S410 if all the air leaves the cylinder I just cock it before pumping. Make sure it is unloaded first.

 

FM