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PostPosted: Fri Mar 10, 2017 10:19 am 
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Jon Math wrote:
Thanks, that is good to know. I always wondered if it would just leak or blow off the end of the cylinder.
In this regard, I feel that any explosion danger is greater with CO2 than compressed air. And I have direct personal experience to quantify both.

With compressed air, a seal failure means a blow-by leak of air of a known pressure to zero pressure... it just leaks down. Lots of hissing but no drama. I've had this happen twice with CZ200 cylinders... the gauge incident noted above, and a cylinder seal failure during a Field Target match. Again, hissing but no explosion.

In contrast, with CO2, the pressure rises dramatically (explosively) as 800psi liquid (supergas) is exposed to ambient air and expands. That's how CO2 works when controlled -- firing a shot -- but uncontrolled when there is to seal failure.

I acquired a rare, .20cal Sharp UDII CO2 rifle several years ago as a collector piece. Love the rifle, still have it and shoot it occasionally. However, it was already many years old when I bought it, and I doubted the integrity of the seals. So... the first time I filled it with CO2, I removed the stock and wrapped the action in a bath towel, just in case. Sure enough, an hour later, as the liquid CO2 rose to room temperature, one of the tube seals gave way comprehensively.

KABOOM! The valve flew out the back of the rifle, taking the hammer and spring with it. Thankfully, all was contained within the towel. No metal parts were destroyed, other than I found only about half the o-ring, broken into a dozen bits. The o-ring was very old, dry, hard and brittle, and had several cracks. The boom was quite loud.

Just to emphasize... this happened because the o-ring was beyond old with many defects, releasing the CO2 at a high (explosive) rate. A worn o-ring that is otherwise in good shape will not explode if contained within its groove... it will just leak loudly until the CO2 is gone.

Recognizing that anything can happen, this has been my experience with CO2 and compressed air, to date. IMO the sky does not fall...


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PostPosted: Fri Mar 10, 2017 12:43 pm 
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What about gas struts in cars they can contain pressures around 300bar, there is no best before date on those.


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PostPosted: Fri Mar 10, 2017 12:55 pm 
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In my professional life I have worked in process engineering. I’ve seen some pretty strange things happen with compressed gasses and fluids, but usually any real disasters can be traced right back to operator errors. The wrong rated valve in a system, defeated pressure relief valves stuff like that. When things go wrong they can go in a big way, but a small cylinder on an AP is really not worth the concerns. Fill it with oxygen instead of compressed air…well that would be a different story.

I did see the remains of a building in which a scuba tank being filled with an oxygen rich mixed gas exploded in, that was nothing pretty!


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PostPosted: Fri Mar 10, 2017 3:19 pm 
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DFWdude wrote:
IMO the sky does not fall...


You're right, (maybe in 4 billion years) but there is Murphy's law...


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PostPosted: Sat Mar 11, 2017 10:50 pm 
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Finelld wrote:
These cycles can also cause metal fatigue and fissures associated with this as well. While I disagree with the blanket policy, I understand and agree with its purpose and intent.

I feel there should be avenues within the rules to allow for nondestructive inspection (NDI) for cylinders and have them recertified.



So specifically in the SCUBA world, NDI exists. Would someone please do the math of what those NDI costs are in a 10 year period? that would be nine visuals and two hydros?
(9 x V)+ (2 x H) =???

And keep in mind that SCUBA tanks require only a rubber mallet to disassemble them. Not specialized tooling for the both the fill end and the gauge end of an airgun cylinder.


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PostPosted: Sun Mar 12, 2017 3:04 am 
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Quote:
In contrast, with CO2, the pressure rises dramatically (explosively) as 800psi liquid (supergas) is exposed to ambient air and expands. That's how CO2 works when controlled -- firing a shot -- but uncontrolled when there is to seal failure.
All pressurized gas will expand when "exposed" to ambient air. CO2, btw, behaves relatively friendly in that respect. When CO2, in the liquid state only, (e.g. in overfilled cylinders) is suddenly "exposed" to ambient air pressure, it instantly tranform to CO2 "snow", as in fire-extinguishers (with rise tube).
Quote:
So... the first time I filled it with CO2, I removed the stock and wrapped the action in a bath towel, just in case. Sure enough, an hour later, as the liquid CO2 rose to room temperature, one of the tube seals gave way comprehensively.

Just to emphasize... this happened because the o-ring was beyond old with many defects, releasing the CO2 at a high (explosive) rate. A worn o-ring that is otherwise in good shape will not explode if contained within its groove... it will just leak loudly until the CO2 is gone.

The pressure of CO2 rises fast as temperature rises to room temperature, yes, and a worn O-rings may eventually fail.

Worst case scenario: If a CO2-cylinder ever ruptures "explosively", then hydrostatic pressure is the cause. Overfilled, chilled cylinders (may) contain liquid CO2 only, and this liquid will expand as the temperature of the liquid rises to ambient air temperature. Max fillweight is stamped on the cylinders. Don`t be tempted to overfill CO2 gas cylinders, to "gain a few more shots".
A properly filled "healthy" CO2 cylinder may never fail from overpressure. At reasonable temperatures that is.


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PostPosted: Sun Mar 12, 2017 2:50 pm 
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Location: czech republic
Gentlemen!
Co2 must not be dry at all times. Generally all Al alloys are typically in the acid and wet environment susceptible to selective corrosion, particularly under stress. This corrosion may not be noticeable to the naked eye, see my notes
http://www.targettalk.org/viewtopic.php?f=4&t=54750
I recommend the microscopic examination and an appropriate NDT method.
Be careful.


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PostPosted: Sun Mar 12, 2017 4:59 pm 
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Reading several references, I am finding that liquid CO2 stored in pure form is NOT corrosive, on metals and alloys. (Several citations linked below. Enjoy the boring reading.)

Apparently, the presence of water is what can cause liquid CO2 to react with metals.

However, since the CO2 used in airguns is normally food grade (as used in carbonated beverage applications), there exists "less than 1 ppm of water in purified CO2, before it is liquefied and tanked for distribution."

The fire extinguisher plant that hydros/refills my bulk CO2 tank refines the CO2 to the same level of purity, whether used for food or fire extinquishers. (It would make no economic sense to have multiple grades of purity, as the costs to clean equipment between runs would be very expensive.)

CO2 is used extensively in large-scale -- hundred Million dollar -- pipeline applications, where water contamination is expected and planned for. As noted in these references, standards of water entrainment in field applications can be nearly 300 ppm and still not be a concern for corrosion.

Yet, for CO2 used in the extremely small scale for our purposes, you should be convinced that CO2 stored in AP cylinders is in no way corrosive.

https://hub.globalccsinstitute.com/publ ... -onshore-5

http://www.eng-tips.com/viewthread.cfm?qid=235228

http://www.twi-global.com/capabilities/ ... corrosion/

https://www.ohio.edu/engineering/corros ... 8153-5.pdf

https://publications.csiro.au/rpr/downl ... 5&dsid=DS2

http://www.corrosioncenter.ohiou.edu/do ... /11377.pdf


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PostPosted: Sun Mar 12, 2017 8:09 pm 
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Location: Dallas, Texas
CO2 is an inert gas. Inert, unless in the presence of water. When dissolved in water CO2 'becomes' carbonic acid. Very weak acid, it's what makes fizzy water slightly tart. Over a long period of time it will attack metal. But ppm of water is not enough to do any damage.


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PostPosted: Sun Mar 12, 2017 8:35 pm 
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Location: Australia
Jon Math wrote:
I’m much more concerned with the gauge failing catastrophically than I am the cylinder rupturing from metal fatigue; but both are potential failure points.

With the costs of .22’s these days I can easily shoot off the cost of a new air cylinder in a weekend, a new $200 cylinder every ten years is pretty cheap insurance for my safety in the big picture.

Not much about target shooting is inexpensive if you are doing it right. Guns, travel, lodging, time, ammo, entry fees it all adds up fast.

Exactly, I'm not sure what all this griping about spending $20/year is about.

Aluminium does develop fatigue cracks, if people think its worthwhile to have a - lets say - $50 inspection and rebuild to get an extra $100 value out of their cylinder then by all means convince the ISSF and manufacturers association.

Otherwise I just don't see that its worth the trouble.


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PostPosted: Mon Mar 13, 2017 4:05 pm 
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Location: Montreal, Quebec
I'm glad I still have the 20 years max Morini cylinders that are 2x as thick and heavy as the 10 years max ones. Har har


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PostPosted: Tue Mar 14, 2017 12:12 am 
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I also agree the older cylinders were better made than the newer ones.

I compared an old cylinder (left) with a unused cylinder made in 2005 (right).

I think the "newer one" has a manufacturing defect. The diameter of the walls of the cylinder on the end of the air gauge are uneven, making me to believe that with use, the cylinder can burst. Check your cylinders to make sure they have the same thickness!


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PostPosted: Tue Mar 14, 2017 1:35 am 
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Location: czech republic
kevinweiho, do not panic. At this place there is no stress. It is a geometric inaccuracies in the machining process merely. It's a visible defect only.

I agree, the older version was usually better quality. When there was no 10 years time limit, manufacturers have tried to make cylinders with the maximal care and almost "unlimited" lifetime. The cylinder life influences used the type of aluminum alloy (chemical composition and heat treatment method), the quality of the finishing (anodizing) and operating stress. The operational stress is determined by design (especially the diameter of the cylinder, part of its length) and from working pressure (200 bar or 300). In other words, if the design of the cylinder was performed correctly and the operating stress well below yield strength of the material, the cylinder life is practically unlimited.
Todays all they are trying to save and still make as much money. That is the reality. For little money a lot of music ;-)


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PostPosted: Tue Mar 14, 2017 1:49 am 
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I was being ironic. I'm pretty sure the 20 and 10 years max Morini cylinders are exactly the same.


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PostPosted: Tue Mar 14, 2017 3:46 am 
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pbrejsa wrote:
It's a visible defect only. Todays all they are trying to save and still make as much money. That is the reality. For little money a lot of music ;-)


That “visible defect” worries me. If you actually see it in person, the wall of the cylinder looks a lot thinner than the pic.

Yup, many manufacturers churn out products faster, so they can make more money. Sometimes skipping quality controls, thus increasing the probability for defects. I think air pistol cylinders are made the same way as scuba tanks being extrusion pressed instead of CNC machined from a cylindrical block of aluminum alloy.

If a cylinder is well made, it should last for a long time. However, I still have the gut feeling that something will go wrong when I least expect it.

A bit off topic, you Czechs are lucky. A civilian like yourself with no criminal record, can own and use automatic weapons with no red tape. I am a big fan of CZ line of products. My favorite is the Scorpion Evo, but nothing beats the feeling and handling of the all steel CZ 75 pistols.


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PostPosted: Tue Mar 14, 2017 3:53 am 
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v76 wrote:
I was being ironic. I'm pretty sure the 20 and 10 years max Morini cylinders are exactly the same.

I know, but I stand my ground that the “older stuff” is better made... :,) Throughout the years, they could have switched to a different aluminum alloy to manufacture their cylinders.


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PostPosted: Tue Mar 14, 2017 6:40 am 
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ask Steyr about the cylinder thickness... I'm curious if it's dangerous (they will know)

also, the gauge is not dangerous at all, if it fails, it will just hiss for a few seconds. For explosion you'd need the metal to rupture. This will only happen on the side of the cylinder, because as you'd see if you disassembled the cylinder that the front and end caps are pretty thick, it can only injure you if have your hand wrapped around the cylinder, during the filling process/mounting

can somebody please fill one of the older ones up and throw it into fire and film it (safely)? That would be awesome


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PostPosted: Tue Mar 14, 2017 11:54 pm 
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hundert wrote:
ask Steyr about the cylinder thickness... I'm curious if it's dangerous (they will know)

also, the gauge is not dangerous at all, if it fails, it will just hiss for a few seconds. For explosion you'd need the metal to rupture. This will only happen on the side of the cylinder, because as you'd see if you disassembled the cylinder that the front and end caps are pretty thick, it can only injure you if have your hand wrapped around the cylinder, during the filling process/mounting

can somebody please fill one of the older ones up and throw it into fire and film it (safely)? That would be awesome


Steyr does not manufacture all of their components. If I am not mistaken, the parts of the cylinder are made for them by sub contractors,
then they’re hand assembled in the Steyr facility. So far, I have not heard of any Steyr recalls, so I assume my cylinder is safe to use.

If the cylinder was to explode due to a thinner wall section that compromises the structural integrity of the pressure vessel, I can guarantee you will be injured in some way, even though you weren’t holding onto the cylinder.

I think it would be safer and easier to ask Steyr if they have done any destructive cylinder testing at a lab. That will clear many of our doubts concerning the safety and life expectancy of air cylinders.


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PostPosted: Wed Mar 15, 2017 7:01 am 
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I just calculated that the energy of the gas inside a fully filled cylinder at 200bar is 0.00359kg TNT equiv. A typical hand grenade has 0.0150kg TNT.

So, 3.59g vs 150g TNT

the blast wave of a typical hand grenade is very weak, it needs to be within a few inches from you to kill you, from one meter it's harmless (we're talking the blast wave, not the shrapnel). It will take your hands off if your're holding it.

if you don't have your hand wrapped around the cylinder, nothing will happen, with your hand something like 10 inches away from a cylinder which explodes nothing will happen.

Now, what will happen when it bursts while you're holding it, I don't know. I have an old cylinder which I could wrap with chicken wings and throw into fire :D I'd say some of the fingers will come off, will tear skin and tissue of your palm.


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PostPosted: Wed Mar 15, 2017 7:18 am 
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hundert wrote:
can somebody please fill one of the older ones up and throw it into fire and film it (safely)? That would be awesome

hundert wrote:
I have an old cylinder which I could wrap with chicken wings and throw into fire :D I'd say some of the fingers will come off, will tear skin and tissue of your palm.

Please don't. It will simply provide an internet visual that the "sky is falling" people will twist and distort to fit hundreds of differing opinions and armchair calculations... Further, the ISSF will over-react and outlaw all compressed gas cylinders.

We'll be back to the stone ages shooting Walther LP53s. I have an LP53, and trust me, shooting one is not pretty or fun.


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