Posted by sean on July 12, 2001 at 22:12:51:
Hello.
I was looking at
used scuba tanks on eBay to fill my air gun cylinder. I found a couple of tanks
but I couldn't decide what size to buy. Any suggestions? Of course the bigger is
the better but what is the minimum useable size? I appreciate your help.
Sean
Posted by Will on July 12, 2001 at 22:35:19:
Sean -
Your question is
sort of weird in that you know big tanks are better (more volume, pressure being
the same), but you want the 'minimum usable size'. Well, I've got a 13cu.ft
tank, a pony bottle, that is quite usable. Until its pressure is low, and a
small tank doesn't last too long. So, back to your own words - 'bigger is
better'.
80cu.ft tanks are standard for air pistol/rifle shooting, but I'm
currently leaning toward larger tanks for my collegiate team's air guns. More
volume, pressure stays higher/longer, more fills... And, the refill cost to me
is the same. But, it isn't the size of tank I want to lug around to different
clubs, either.
Figure out your own needs/budget, and make a decision. I,
personally, wouldn't buy a scuba tank from ebay. I'd go to a local dealer (who
will be doing the filling) or private party. You can examine the exterior of the
tank that way and check the valve, too. Check for hydro dates, manufacture date,
visual inspection date Look for gouges and corrosion which can influence the
longevity of the tank.
If it all sounds too confusing, buy a pump from
Scott, he has the better, newer, ones.
Will
Posted by JLK on July 12, 2001 at 23:20:20:
I bought a scuba tank off
ebay and had no idea what I was doing. Had to have it shipped from California to
Oklahoma (the things are heavy), it was out of inspection and had to be hydro
tested, it had corrosion and had to be bead blasted PLUS it was only rated 2475
psi... all scuba tanks are not created equal! By the time it was all over I had
more invested than if I had bought a new tank from the local dive shop AND I
would have gotten what I needed. Ended up buying a used 3000 psi from the dive
shop and now "cascade" fill my LP10 cylinders.
Hope this helps you keep from
making the mistakes I did!
JLK
Oh, by the way, I have the TV on at 10:15PM
here in Lawton and the weather guy says it's 99F !
Posted by Pradeep on July 13, 2001 at 02:36:59:
I got a new 80 cu ft.
Catalina steel scuba tank for about AUS$450 ~US$240. This is rated to 250bar
working pressure (W.P.) Included in the price was a 300bar DIN fitting (I had to
order it specially). I had to modify the 200 bar filling adaptor that came with
my Morini so that it would screw far enough into the 300 bar fitting to engage
the end. When u think of the tremendous pressure a scuba tank holds, I would
never buy one second hand, especially not from an auction site.
Posted by pilkguns on July 13, 2001 at 07:57:55:
I hope you are only
having this tank filled to 200BAR as that is what the Morini Cylinder is rated
for. While your dive shop was special ordering you something, You should have
had them order you an 200 Bar valve and then you would have had the correct set
up for both your Morini adapter AND your tank
Posted by Pradeep on July 13, 2001 at 20:13:13: I get the scuba tank filled
to about 250Bar at the fire station, but only fill the Morini cylinders to
200bar. I feel safer having a 300bar din fitting than a 200bar din fitting;
obviously I couldn't fill it to 250bar if I had the 200 bar din fitting on.
Posted by Michael Ray on July 16, 2001 at 18:50:23:
I'm guessing you have
a regulator on the tank as well?
My simple understanding of this was you
screwed on your cylinder to the tank adapter, opened the tank valve to charge
the cylinder to the same pressure as the tank (actually just a tad less), and
closed the valve. How do you control what pressure you charge your cylinders?
Posted by Pradeep on July 17, 2001 at 04:13:51:
I control the pressure I
charge the cylinders to by looking at the pressure indicator on the end of my
cylinders (from an angle, not directly in front ;) So I close it off after it
reaches 200 bar.
Posted by mako on July 12, 2001 at 22:54:22:
I know Scott doesn't like
scuba in general ... for safety reasons, so he'll probably really not like this
"suggestion."
For around $318 you can buy a used (with around three years of
life left on it) 4,500 PSI 1/2 hour firemans breathing tank with valve. You
still need to buy a yoke ... which Scott might have for sale on the Pilkgun
site. This is a pretty small tank, a little less the 2 feet long and around 8"
across but it's good for around 6 month of weekly shooting filling a 3,500 psi
air pistol cylinder.
These tanks are safety wrapped in fiberglass or carbon
fiber (the newer ones). So you get a convenient light tank that will give you a
lot of refills. My local scuba place has no problem filling this tank. You do of
course have to carefully monitor the gauge when filling if you are using 200
bar/3,500 psi air cylinders and you are filling from a 300 bar/4,500 psi tank.
But the 200 bar tanks are of course rated higher, usually 300 bar I believe ...
so you don't have to worry if you overfill a little. Those of us using Walther
airguns can fill to 300 bar ... but Walther says that you can save a bit of wear
on your Walther by not filling to 300 bar. I only fill to 200 bar and still get
over 130 shots per air cylinder.
Apparently paint ball shooters are using
these 4,500 psi tanks a lot. You'll discover this if you do an internet Search
for "4,500."
Of course the latest hand pumps are so efficient and effortless
that if I had one I might not have bought a tank. The new pumps are the ones
where the thicker part of the pump body travels up over the thin rod. Even with
their silcon condensation balls, it's probably a good idea to only do about 35
psi of filling before letting the pump cool off. This allows more moisture to be
extracted from the air ... and less getting into your cylinders and
regulator.
A good source for used 4,500 psi tanks is American Airwork. Talk
to Ray Lambert (800) 523-7222. The also have 1 hours tanks if you don't mind the
extra size. They might be good for a club ...
Posted by Will on July 13, 2001 at 00:46:20:
I do not think it wise for
anyone to pay attention to Mako's suggestion - sorry Mako.
It would be
foolish and dangerous to attempt what he is advocating, for many reasons. One,
200Bar is not the 3500psi Mako says it is, closer to 3K, and to make a mistake
and put 4500psi in a 200 bar cylinder is just plain dumb and dangerous. Do not
fool with high pressure air. Period. Also, what Mako does not tell you is that
scuba yokes are rated differently, like 200bar and 300bar - a big difference and
a larger error factor if using the incorrect one with a higher pressure
tank.
The only safe way to use a 4500psi tank for a 3000psi cylinder is to
use a reducing regulator, which can be had for $200-300. Add that to Mako's $318
used tank and you could be up to $600. Great if you want to blow big bucks fast,
but, for about $200 in my area (New England), I can get a brand new 100cu ft,
3000psi tank, with a DIN valve (so a yoke won't be needed) with 10 free fills.
And, save up to $400 to boot.
Mako, your saying, "so you don't have to worry
if you overfill a little" is taking something that should be treated with
knowledge and respect and caution and making it casual. Refilling cylinders
should be taken seriously.
This board has some very experienced shooters as
readers, but it also has many novices. You should be more careful with the
information you give everyone, especially the novices.
Sorry to come down a
little hard, but this is a safety issue, and I not take them lightly.
Will
Posted by mako on July 13, 2001 at 02:59:01:
In Reply to: NO!!! posted by
Will on July 13, 2001 at 00:46:20:
Points well taken, especially concerning
novices...
I tend to write too quickly ... but I actually think and act
slowly and carefully. :-)
FYI, 200 Bar= 2930 PSI, 300 Bar =4351 PSI
NT
Posted by pilkguns on July 13, 2001 at 08:03:22:
Posted by Mark P. on
July 13, 2001 at 00:45:23:
I pretty much second what Will said. I dunno
about going with the 4500 psi tank that Mako suggests.
While cylinders are
usually pressure tested to that level, I'd worry about going above the approved
pressure too often. Would you shoot proof loads through your firearm? Granted,
he doesn't recommend this, but by having a regular 80cu.ft. tank that's rated
for 2500-3000psi, you never have to worry about accidentally overfilling your
cylinders. In addition, you'll probably find a regular 80cu.ft. tank a lot
cheaper. I bought one a couple months ago (nice aluminum Catalina rated to 207
BAR in candy apple blue) for about $150. Also, to add some emphasis to the risks
you take when you buy tanks (especially older aluminum) from an unknown source,
check out the links below. Simply put, these things can be BOMBS if they let go.
Don't get cheap on these things.
Posted by Gene Rotsch on July 13, 2001 at 01:46:05:
Hi Sean,
I use a
similar tank to what Mako is referring to. 4500psi rated, firemans oxygen
bottle, filled to about 4200 psi. Have used this bottle since about '93, maybe,
with zero problems. It is very portable and gives months of service before
needing to be refilled. You do have to pay close attention when filling your
cylinders, so they are not over filled. The yoke I use on my P34 has a gauge on
it, that I monitor while filling my cylinders.
Will is correct that you have
to have a high pressure valve that fits the tank, though they are not quite as
expensive as he mentioned, from my experience. I also make sure to stay current
with all the necessary inspections and testing, which is required on any
compressed air tank. With the proper care and treatment, this size cylinder is
very safe and useful. Mako and I want a tank that is portable, with long term
use before refilling. This type tank gives us that. Consider your needs and then
talk with your dive shop operator for suggestions. Remember, the only dumb
question, is the one you don't ask. Make your decision based on accurate
information and you will be fine.
Deep 10's,
Gene
Posted by Will on July 13, 2001 at 08:57:04:
Gene -
If you read my
post, again, you will see that I did not price the valve (or the valve adapter),
just the regulator, and, yes, regulators are that expensive. Valves, adapters,
and regulators are different parts, Gene. Had I added the valve adapter to the
package cost (I can get them for $30), it would be even higher. To use the
'fireman's tank', which to my knowledge does not take regular scuba valves, one
needs to thread on to the stock valve an adapter which protrudes and has a
fitting for the yoke to attach (that's the way I've seen them used, anyway, for
paintball). That sysytem works well for filling like-pressure cylinders.
BUT, to use it as Mako suggests, is too risky. To use it as you do, too,
Gene, is risky, but you are adding an extra step to reduce the risk by using the
gauge. Is your yoke rated for 200 or 300 BAR? You may not know, but you should
check. What is the quality of the pressure gauge you are working with?
You
have been using that bottle since '93 with zero problems. Great. I once knew an
automotive salvage 'expert' who used a torch to cut gas tanks off cars. He had
over thirty years experience. Like I said, I once knew him.
As a former
urban firefighter, I have used the 'fireman's tank' for what it was designed
for, and have respect for what it does. And, I have been offered those tanks
(for free!) to use as fill bottles for my airguns. I passed on them. But, if I
did use them, I, personally, would have them filled to no more than
3Kpsi.
So, other than portability, I see no real strong points for using
them. By my calculations, you would be far ahead, in dollars and safety, by
getting a 3Kpsi 100cu ft tank for the house and a small pony bottle for travel.
(Old 'fireman's tank', $300, adapter, $30, yoke w/gauge $100 (should use
regulator) you're up to $430 and more. Cost of new 100cu ft tank w/DIN valve and
10 free fills, $200, new pony tank w/DIN valve and 10 free fills, $135, total
cost, $335. Safety margin, priceless.
For you new shooters thinking of
getting into compressed air, do the right thing. Be careful.
Will
Please
tell me that you got your terminology wrong
Posted by pilkguns the saftey tyrant on July 13, 2001 at 08:15:40:
and
that you are NOT using a yoke to go from 4200 to 3000. yokes are not designed to
withstand that kind of pressure, thus the threaded fittings for connections
above 3000 psi . They will stretch and then come apart and are not very freindly
when they do so.
If you are using a yoke, pales tell us that you ae going to
go this weeke and get the correct fittings to properly step this down.
This
stuff will kill you, see the link on the posters below comments
: on my P34
has a gauge on it, that I monitor while filling my cylinders.
: Will is
correct that you have to have a high pressure valve that fits the
: tank,
Posted by Grzegorz on July 13, 2001 at 12:10:10:
Hi,
I use 200 bar 50
liters tank to fill my air rifle cylinder since one year, and the pressure is
180 bar now... So, if you want to buy a tank for your team - buy a big one. If
you want to buy a tank for yourself and keep it at home (never under the bed!)
buy 5-10 liters tank, otherwise you will need a specialized team to move it from
your home to any filling center...
Safety:
1. If your air pistol/rifle
cylinder is limited to 200 bar NEVER fill it using any tank having more than 200
bar gas inside (no matter what gas)! This is only possible with a professional
pressure reductor, but better skip this idea. It can break too one day...
2.
If your cylinder is limited to 300 bar (ex. Walther LG/LP300) fill it up to...
200 bar. What a nice safety margin, isn't it?
3. If you look for any tank -
better buy 300 bar one and fill it always ONLY up to 200 bar. The same reason as
in 2.
4. ALWAYS limit a maximum pressure used to the weakest
tank/gauge/cylinder/regulator part!
I do not know how about you, but I feel
much better during competition having my air rifle cylinder at 150 bar than at
200 bar...
Best rgds
Grzegorz
PS. Yeah, bigger is better but still
small is beautiful! :-)
Hey Gregorz, want to go to work for me, what a
wonderful post! nt
Posted by pilkguns on July 13, 2001 at 15:08:16:
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