TargetTalk

I know that the Steyr can only be charged to 200bar.

I have a dive tank that can be charged to 220bar.

If I am careful with the charging and only fill until the gauge on the pistols cylinder sh owes full is that safe ?

After a few fills the pressure in the dive tank will soon drop below 200bar but should allow me to fully charge the pistol several times.

Thanks for your advice

Paul

Hi Paul,
I hope all is well in Kiwi land. My local dive sop fill a 3000# tank above this limit. They call it a "California fill" Why it has that name I am not sure. I fill the cylinder on my LP 10 very slowly and when it gets close to the 200 bar mark I shut the valve off. The manometers on the cylinders will vary a bit, so filling it slowly from a 220 bar dive tank should not be a problem,
Good shooting, think 10.9
Neil

it doesn't matter, as long as the cylinder does not stay at such a high pressure for a prolong time.

i have seen cylinders charged up into the red, at 230-250 bar. so i suppose its ok.

also, if you accidentally fill it to over 200 bar, you can try releasing the excess gas from the cylinder, instead of choosing the more cumbersome way of carefully charging it to make sure that it does not exceed 200bar.

Thanks Guys

Just done the calculation

It seems that by using a 100cf filled to 220bar I would get 43 refills.
With the 80cf tank at 200bar only 10 refills so there is quite a difference

http://www.airgunexpo.com/calc/calc_fill.cfm?

Regards
Paul

I have some remarks with your question:
- for the cylinder, loading at 220bar is not be a problem since it is tested till 300bar (like the 200bar scuba dive tanks that are also tested tat 300bar)
- you should not rely too much on the very inacurate manometer of the cylinder. I have read that its precision is +-10%, i.e. +-20bar !
- I do not think that 220bar at room temperature is a real problem since it is only 10% more and, since pressure can vary quite a lot with temperature, the regulator of the pistol, is made to still work with a little more than 200bar
- about refilling the scuba tank: since the tank warm up during refill, good shops let the tank cool down a while after the refill and then do a second refill to come to 200bar or put a little more. If this is not done, you actually do not get 200barafter a refill but less (you can easily loose 10-15 bar). When you refill your cylinder you should normally do the same, buit with your tank at 220bar, you can suppress this second fill and I think that you will come very close to 200bar when the cylinder will cool down.

Hi - a few comments from someone who has a dozen cylinders in use for diving, with air, oxygen, nitrox, trimix, you name it...

Testing
These little cylinders are designed to be filled to 200 bar, and they are tested to 300. Filling slightly over pressure is not a problem as they have to conform to a number of things to pass the test, so hence it is quite conservative. For example, rated pressure in steel cylinders is normally 232, tested to 345. Aluminium is usually rated 207, tested 320.

Filling
If you fill quickly, the little cylinder heats up and so if it goes to 220 hot, you'll end up with a nice 200 bar fill when it cools. Or you could fill very slowly, monitoring it, and avoid the adiabatic heating and stop at 200. When your fill pressure drops to 200, you can just leave it on the fill cylinder for 10 minutes and it'll all balance out nicely. When its a bit low, and you want to get more out of your fill cylinders, put the little one in the fridge before you charge it to lower the fill temperature. Don't use the freezer though!

Effects of overpressure gas
My concern is not about the pressure in the cylinders, 200 or 220. It is about the design pressure of the mechanism within the pistol, and whether overloading it could lead to premature wear / damage. As I don't know how much margin is built into the regulator mechanism for overpressure gas, I pretty much stick to 205 as a maximum. If it works like a diving regulator, then it is probably fine up to a much greater pressure, but as I always have plenty of gas left after a session of 100 or more shots, why risk the expensive and possibly sensitive mechanism? When I have £500 of pistol, and £3 of gas, I know which one i'll try and conserve !!

Fill Cylinders
As far as the number of fills is concerned - base you decision around convenience rather than theoretical cost. If its a pain to get to a fill shop, get a big cylinder and only fill it occasionally. If its easy, get a 3 liter and fill more often, and then you can take it around with you, and refill from it when its dropped to a lower pressure than you would be prepared to use without a backup around.

With a 3l compared to a 12l
Your fills cost less but are relatively expensive.
Your servicing costs will be the same
You can carry it about much more easily
You get less fills but you make better use of the gas you have
It takes up less space!

Hope that helps

Ed

Thanks ED, very helpful

Paul