TargetTalk

After seeing a few posts on the subject, I have to ask, "Does anyone except some newbie give a shit?"

Only if you go to a top competition (World Cup etc.) and at gun check they fail to pass your pistol.

Has this happened to you or anyone you know?

If you really want to know the answer, maybe some people.

If you knew about the failure characteristics of aluminum, and how it tends to go from "fatigue" failure to brittle or "catastrophic" failure, if you really knew about bursting aluminum scuba cylinders or aluminum crossbow arms (why you don't see them), you might be one of those people who give a shit.

Now, if you're just bragging about how you save OVER $150 every ten years, then you undoubtedly don't give a shit, so why ask?

Ricardo;

I've heard others mention the same thing with respect to aluminum. What are your feelings on steel cylinders, typically on older CO2 guns?

Thanks,

-John

"Fatigue" occurs from overuse; in the case of aluminum compressed air cylinders, overuse would mean many, many fill-empty cycles. Overuse is only remotely tied to the arbitrary 10 year limit imposed by the cylinder manufacturers. What a 10 year limit logically says, in effect, is that no matter how much use a cylinder can receive in 10 years, it is still safe for the full 10 years.

Most, if not all, cylinders do not receive maximum use in the first 10 years of their lives. Many receive far less than maximum. The only cylinders that were known to fail (at least as reported here on TT) were a batch that was defective, failed early on, and were recalled. I agree with Rover - it's not important.

In the case of CO2, it's even less important, whether the cylinders are aluminum or steel. CO2 maximum pressures are less than 1/3 the maximum pressures of compressed air. In addition, CO2 cylinders have pressure release devices in case the cylinders get left in the sun. In general, I really wouldn't worry about fatigue in them either.

Where problems may occur is in the area of corrosion caused by moisture. That's why so many people recommend SCUBA air instead of a hand pump, which is more likely to introduce moisture inside the cylinder. Again, whether or not a cylinder has, or has had in the past, moisture inside has nothing to do with the arbitrary 10 year limit. If you're buying used cylinders, it would make much more sense to ask about their moisture exposure, rather than whether they are older than 10 years.

I want to point out that I am not an expert in metallurgy, but I do believe that verifiable facts and simple logic can go a long way in making sense of things.

FredB

Ricardo,

I'll repeat my question: "Has this happened to you or anyone you know?" (with an AP cylinder)

John C wrote:Ricardo;

I've heard others mention the same thing with respect to aluminum. What are your feelings on steel cylinders, typically on older CO2 guns?

Thanks,

-John

John: I don't know about steel, except that it tends to fail more gradually and cylinders tend to tear rather than burst (I'm talking SCUBA here), with less explosive release of pressure. As to age... that's a good question. SCUBA cylinders get inspected rather frequently, and presumably end up de-certified. Pressure in CO2 cylinders is less than 200 bar, but then again maybe the steel is thinner.

At a domestic comp shot in the UK to ISSF regs, they did check the cylinder. I don't know if they'd have actually prevented people from shooting with old cylinders, or whether they were checking just because it was on the Control form, but they did check it. And that was most decidedly not a world class event!



One thing to bear in mind for club airguns is that if the 10-year limit is a manufacturer recommendation for general usage and not simply an ISSF limit for their competitions, then there may be civil liability implications on club guns if one did go pop in someone's face.

Now I'm not a metallurgist [/disclosure] but I would say it's unlikely to be a problem in the near future - I haven't seen a cylinder failure* except for some photos on the web where apparently someone decided they'd get better accuracy from acetylene than breathing air (natural selection in action), but then PCPs haven't been around that long relatively speaking. Certainly not in wide and mainstream usage. It's only now that the early ones are starting to get reasonably old and fatigue-related failures might start to show themselves.

I would purport there aren't any PCP cylinders knocking around that are 25 years old for instance. Most have not hit the 10 year barrier yet. I wouldn't be surprised to see them get to that state though, given how long we shooters stretch out kit (how many 1980s-vintage Match 54s are there knocking around, and still shooting well?). My concern is we don't really know how well they will survive club life over a decadal period. SCUBA divers get their tanks inspected annually (albeit they have a harder life, being regularly immersed), but you don't see many scuba tanks make it to 30, despite the fact that (dare I say it), they probably get a lot more TLC than PCP cylinders. We use them and toss them back in the case, taking them for granted.

No, I don't really personally care if a cylinder is 12 years old rather than 10 (a two year old one that's been abused will probably be less sound than an 11 year one that's been cared for), but what about 20 or 25? If not 10 years, then where does one draw the line, if at all? It is arbitrary, but equally they're high pressure vessels and 200bar going pop within a metre of your face is not fun.

If you want to shoot with an old cylinder, then that's your own lookout and own decision, based on condition, it's history, etc.

If you're running a club on the other hand, it would be worth checking whether your insurance covers cylinders that have expired past the manufacturer's recommended lifespan. For the sake of $15/yr, if your insurance doesn't cover it, then they're worth changing, especially on youth programmes.

Parental lawsuit for maimed kid + no insurance = bad time all round.

It may be a problem, it may not, it may depend on manufacturer, and could vary between insurers so it's certainly worth thinking through and checking.



*I do however know a diver who had a thread strip on a 200bar bottle whilst it was filling from the compressor. Rare, but somewhat of a brown-trouser moment for everyone in the area, and they got lucky that it was a heavy scuba tank which basically fell over after the coupling went bang, not a light PCP cylinder (which would probably resemble a small missile with 200bar jetting out the back of it). That's why you always have the cylinder pointing at a wall or somewhere harmless when filling and read the manometer from off-axis. In the unlikely event a thread does strip, it's not going to embed itself in your eye, stomach, groin, or the chest of the small child stood next to you. They are deserving of extreme respect.

Most aluminium fatigue failures in the aviation industry are usually found in the post crash investigation.
Internal corrosion is easy to inspect and treat.
Pressure/ cycle fatigue failure is the worry, and it is very difficult to find/predict before failure.
The tanks may well be good for 20yrs, but with what safety factor ?
Now that a rule is published the manufactures and officials have covered themselves and the owners are on their own legally if anything happens outside the rules.

Rover wrote:Ricardo,

I'll repeat my question: "Has this happened to you or anyone you know?" (with an AP cylinder)

Cylinders have been checked for dates at world cups in Germany in 2010, at domestic competitions in the UK and at Intershoot in Holland. I attended a couple of these and the shooters cylinders were in date so no problems. I don't know whether anyone failed, but you'd be foolish in the extreme to test it if you were travelling to a major competiton.

Rob.

So other than speculation, has anyone actually seen catastrophic fatigue in an air pistol or air rifle cylinder (not a SCUBA tank)?

6.2.4.2 It is the athlete’s responsibility that any air or CO2 cylinder is still within its validity date. This must be checked by Equipment
Control.

Here is the rule from the new rule book. No arbitory time limit just the manufactures validity date.

David M wrote:

6.2.4.2 It is the athlete’s responsibility that any air or CO2 cylinder is still within its validity date. This must be checked by Equipment
Control.

Here is the rule from the new rule book. No arbitory time limit just the manufactures validity date.

I think it actually says 10 years maximum in the revised rules.

Rob.

Edition 2013 Rule 6.7.7.1 Equipment Control Procedures:
.............
It is the athlete’s responsibility that any air or CO2 cylinder is
within manufacturer’s validity date (maximum of ten (10)
years); this may be checked by Equipment Control and
advisory recommendations may be given;
.............

Greetings Hans

Since there have been many opinions and facts tossed out here, and remembering that Hammerli would replace their cylinders after TWENTY years, there remains the question....

"Why?"

Rover wrote:Since there have been many opinions and facts tossed out here, and remembering that Hammerli would replace their cylinders after TWENTY years, there remains the question....

"Why?"

I believe it's simply because the governing bodies cannot risk a malfunction nor a catastrophic failure of a cylinder during a televised match. No matter how improbably that is and even if it means ruling out perfectly good and safe ten year cylinders. It´s like wearing a seat belt... it does't matter 99,9% of the times... until someone crashes!

The ISSF cannot get the wording uniform in different locations of the same rule book .

I take your point, rmca, but it's not like we're constantly crashing and needed to be protected.

Rover wrote:I take your point, rmca, but it's not like we're constantly crashing and needed to be protected.

Tell that to the cop next time you get pulled over for not wearing a seat belt! :)

Now, and more serious, I believe that is why the manufactures and the ISSF impose the ten year rule, they are basically covering there behind...

There has been always a lot of people that don't like the idea of other people shooting weapons of any kind, regardless of what safety measures they take... and I believe that the ISSF is doing the right move to not give any arguments that can be used against them and the sport. Even if that means ruling out perfectly good cylinders.