Using 300bar tank with LP-10

[joecon]

Hi, I currently waiting to get the import approval for my new Steyr LP-10. This will be my first pre-charged pistol (had IZH-46 for 18 mths, served me very well). I can get the loan, long term of a 7 liter 300 bar (73cu ft @4350psi I think) SCBA tank. My local scuba shop (within 2 miles) can fill to both 200 & 300bar. Below are what I believe my options are, has anyone already done this, what is the solution, pitfalls etc.? Any options or issues I have not listed? Thanks in advance, Joe.

1. Charge tank to rated 300bar;
a) get different adaptor which will connect the pistol cylinder to the tank 300bar DIN connection (as I believe the 200bar DIN supplied with LP-10 will not work), be very careful when filling not to allow over 200 bar to build up in cylinder – how high is risk making mistake!
b) Get a 200bar regulator which will connect between tank & supplied cylinder adaptor- takes care of risk of overfilling but adds significant? cost.

2. Only charge tank to 200bar -2900psi (loosing some capacity);
a) get different adaptor which will connect the pistol cylinder to the tank 300bar DIN connection- risk here is that as the tank has the 300bar DIN connection some day it might get charged to 300bar without me knowing & then the cylinder gets over charged.
b) convert the tank such that it has a 200bar DIN connection – no need for different adaptor, no risk of over charging? – but how would this be done & at what cost?

3. Buy a 200bar tank- easiest but most expensive?

4. Buy a hand pump;
with cost at around same as medium size tank, my easy access to scuba shop, & low cost to refill tank, & risk of mositure- I’ll discount this.

[TomAmlie]

b) convert the tank such that it has a 200bar DIN connection – no need for different adaptor, no risk of over charging? – but how would this be done & at what cost?

This would probably be the least troublesome moderate cost long-run solution. I believe it would simply be a matter of getting a 200 BAR DIN valve, unscrewing the old 300 BAR DIN valve (after emptying the tank!) and installing the 200 BAR DIN valve in its place.

[Neil Foster]

If you are going to go to the expense for a fine piece of gear like the Steyr LP-10 why take the risk of damaging the Steyr, or worse damage to you if the cylinder is overcharged and bursts. The answer to me is a no brainer. Either get the proper 200 bar tank (best idea) or change the DIN valve and ONLY charge the tank to 200 bar. Safety and Prudent
Neil

[Rutty]

change the DIN valve and ONLY charge the tank to 200 bar. Safety and Prudent

Neil has the answer. No need to get a new tank or worry about loss of capacity, your 7ltr tank will last you a long time. As it happens. if you change the valve to a 200 bar one the dive shop will only charge it to that pressure, regardless of the rating of the tank itself.

Rutty

[edster99]

Only other thing to note is the following talking about '200', which is what your pistol cylinder is rated to.

Steel cylinders are rated to 232 bar and normally this is what they would be charged to in the dive shop, so when you charge your pistol cylinder keep an eye on it to make sure you stop at 200.

Aluminium dive cylinders can be rated to 207 (usually older ones) or 232 bar.

You could request the dive shop charge to 200, but its easy to keep an eye on the charge as you fill your cylinder. If your dive cylinder has more than 200 bar in it , you'll be able to fill your pistol cylinder to 200 - a full fill - for hundreds of fills. If you start with the dive cylinder at 200, you'll never get a full fill after the first one.

I have an LP2 - same cylinder - and I charge from a 232 bar 3liter - and that has lasted for months.

300 bar cylinders are normally hard to fill, with few dive shops having the capability. You will pay more for a 300 bar fill but it is very rare to actually get a full 300 bar fill, for a number of Gas Law reasons that i'll tell you about if you want.. :)

232 bar cylinders are easier to manage, fill, etc. If you want to buy one there is a company called Go Dive in Derby that are very good on prices for cylinders, and I believe they would deliver to you. Might be worth a check...

good luck!

Ed

[joecon]

Hi All , thanks for the replies. Looks like 200bar is way to go- need to find out what conversion cost might be.
Just a couple more questions;
What is the connection type used on the Steyr cylinder i.e. the non DIN end of the supplied adaptor (is it an Industry std.)?
When filling from a tank at 232bar a)how fine is the adjustments needed to open the tank valve to avoid over filling? b)I've seen mention here of cylinders over heating due to filling too fast- what sort of fill times do people here try to achieve?
Edster99- Pricing with Go Dive is good, need to call for delivery cost. They also have a link to sister company Go Shoot which has air rifle charging kits - tanks, gauges & fittings; any experience of these?
Joe

[David Levene]

Joe, when you ask about the conversion cost make sure you specify a valve with a built in gauge. When I had a tank of mine done a couple of years ago it cost under £100.

No, the pistol end of the adaptor is not standard.

Beware of air rifle charging kits. These usually have hoses for connecting to the gun, not suitable for top end air pistols. You just want a 232bar valve with a built in gauge.

When filling the gun's cylinder you normally only have to "crack" open the valve. Fill the cylinder as slowly as you can to avoid metal stress and heating.

[edster99]

Hi

The only issue with Go-Dive, and I suspect it'll be the same with Go-Shoot, is that they advertise everything no matter what the lead time would be for things out of stock.. So I would check the stock levels before you commit to an order, or you might be waiting an inordinately long time.

As for charging, as slow as possible is best, but if you keep it to under 3 bar a minute you wont go wrong. Basically, if it feels cool or tepid its ok, if its warm you are going a little bit fast, and if its hot you really must slow down.

If you keep it cool, you'll have no trouble controlling the final fill pressure. I find that I fill to about 205 and leave it a few minutes and it goes down to about 195 or so, then just a little squirt gives you a good 200 bar fill.

The other option is to buy a diving pressure check gauge, rather than one in the cylinder valve - this gives you more scope to buy and change cylinders

http://cgi.ebay.co.uk/Scuba-Diving-Cyli ... m153.l1262

regds

Ed

[Guest]

Wow, can you really charge such a small cylinder at such a 'slow' rate! Not having worked with air or gas systems before I had impressions of having to make sub 1/10 of second valve closes or I would 'fry?' the cylinder. So for a charge of say 140 to 200 bar it could take 20 min plus ?
I suppose thinking about it now its 'NOT about size' it's about the difference in pressure- correct?
As always thanks for sharing your knowledge & time. Joe.

[edster99]

Absolutely right, its all about the pressure differential. If you are decanting pure O2, you are looking at 3 bar/min at absolute maximum, because the heating can lead to it going bang... not good. The more inert the gas - like air - the quicker you can do it, but you then have to wait until it cools down to top it up to the desired end pressure. An option is to put your little cylinders in the freezer, then you can balance out the heating effect by the low temperature you're starting from, and you can feed it in a bit quicker. To be honest, I normally take about 2 mins to go from 120 - 200... so whilst its not recommended, it does work. As soon as you turn off the charging cylinder you can see the pressure drop as it cools. I fill mine to 205, it drops to 200 really quick, i pop it up to 205 again and then leave it, once it has cooled it is usually bang on 200.

You'll find it is very controllable.

cheers

Ed

[David Levene]

The other option is to buy a diving pressure check gauge, rather than one in the cylinder valve - this gives you more scope to buy and change cylinders

http://cgi.ebay.co.uk/Scuba-Diving-Cyli ... m153.l1262

Unless I'm mis-reading it Ed, that gauge only tells you the pressure in the Scuba tank. You have to take it off to fill the gun's cylinder.

The advantage of the valves with the integral gauge is that they read the pressure in the cylinder you are filling.

[Richard H]

Absolutely right, its all about the pressure differential. If you are decanting pure O2, you are looking at 3 bar/min at absolute maximum, because the heating can lead to it going bang... not good. The more inert the gas - like air - the quicker you can do it, but you then have to wait until it cools down to top it up to the desired end pressure. An option is to put your little cylinders in the freezer, then you can balance out the heating effect by the low temperature you're starting from, and you can feed it in a bit quicker. To be honest, I normally take about 2 mins to go from 120 - 200... so whilst its not recommended, it does work. As soon as you turn off the charging cylinder you can see the pressure drop as it cools. I fill mine to 205, it drops to 200 really quick, i pop it up to 205 again and then leave it, once it has cooled it is usually bang on 200.

You'll find it is very controllable.

cheers

Ed

3 bar/minute where pray tell did you come up with these figures? I've been to the factories and they fill them way faster than that. Air is not an inert gas either. Nitrogen which comprises 80% of air is inert the other 20% is oxygen which is far from inert. the freezing of an air cylinder is also not a good idea, for starters its going to be hard on the o-rings, if there is any moisture you will also get condensation. A slow controlled fill is all that is required, just don't fire open the valve and shock load the cylinder.

[edster99]

Richard

I fill much faster than that, and most people do. However, if you do an TDI or and IANTD Gas blending course, you'll find thats the speed they recommend. Not really necessary, but as I said it applies to higher O2 fractions as well. Theres always a difference between recommendations and reality! As for freezing, it doesn't cause a problem that I have come across. It might be hard on the o-rings, so if you think it might be don't do it. As for condensation, the fill adapter is at ambient temp so it wont have any condensation on it, so it wont introduce anything into the cylinder.


David
Thats right you do have to take the reading with the cylinder off, but all you need to know is that theres enough in there to fill the pistol cylinder. LP10 cylinders tell you what the internal pressure is anyway with the built in pressure gauge. You don't need to measure that twice, more useful to know whats in your charging cylinder.

regds

Ed

[jipe]

I think that the only right way is to use a 200bar tank because from my experience:
- filling a small AP cylinder goes pretty fast
- the cylinder built in pressure gauge is not acurate at all, it is only usable to have an idea of the remaining air in the cylinder
- there is always some cylinder heating resulting from filling the cylinder, so the right way to fill is to fill to 200bar with some heating, wait some times to let the cylinder cool down and then equalize the pressure with the tank a second time.

I would also advise to use a bigger capacity than 7l since the pressure drops too fast with such a tank capacity.

[edster99]

my cylinder is 0.068l, so filling from a 7 l is a 1% take - if you have 30 bar over the 200, you'll get thirty fills at 200 bar, and then another 30 down to 170 - still plenty... one fill is 100 shots, so thats 3000 from your cylinder - enough surely??

Ed

[MG2-owner]

LP10 cylinders tell you what the internal pressure is anyway with the built in pressure gauge. You don't need to measure that twice, more useful to know whats in your charging cylinder.
Ed

A 200 bar tank is usually filled at divershops to 220 - 230 bars. After å few cylinderfills your scupa tanks holds less than 200 bars.

I bought a 300 bar bottle, then had a tool shop custom make a 300/200 bar "converter", with a relief wheel valve installed (valve for convenience, its is not necessary).

When filling cylinders, just keep focused at what you are doing, whenever the tank holds much over 200 bars.

I bought the 300 bar tank cause I use it to fill MG1 cylinders, whith a 250 bar upper limit of "green zone".

A 300 tank holds much more air than a 200 ( 232 tank).
A 300 bar (filled usually to 310 - 320 bars) will give you a lot of cylinderfillings until the practical 150 bar level is reached, a 200 bar tank much fewer.

But, As have been stated above, filling a 200 bar air pistol cylinder from a scuba tank potentially holding over 300 bars is not foolproof.

[edster99]

My experience is that 300 bar fills never get to 300, let alone over it to 310 or 320... but you might get lucky !

[Guest]

My experience is that 300 bar fills never get to 300, let alone over it to 310 or 320... but you might get lucky !

I have attended the tank-filling in the divershot myself. Filled to about 320, according to manometer of filling aperature, tank luke warm from filling.
When cooled to normal temperature, it reads some 310.

Whct could be the reson for your divershop not filling your 300 bar tank to 300 bars?
Defect compressor equipment?

[edster99]

Possibly - but seems to be the case wherever one goes. For diving 300 bar cylinders are becoming much less popular for this very reason. If you always get a good 300+ fill, good luck to you!

cheers

Ed

[RobStubbs]

Whct could be the reson for your divershop not filling your 300 bar tank to 300 bars?
Defect compressor equipment?

The most probable reason is that they are not cooling the cylinder properly and/or filling too quickly. As an aside that also happens with a 232 cylinder as well - mine has been 'filled' to as little as 170 - 180. Unfortunately you can't tell until you get it home.

Rob.