You also can open you bleed valve ( on whatever your filling method is ) very little to empty your reservoir, just a tiny bit.
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With most compressed gas cylinders the enforcement mechanism are the fill centers. In order to both comply with the law and protect their employees they will insist on regular inspections before filling your cylinders. But once you start filling your own gear it's all up to you.
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I do not think the DOT regulations for SCBA tanks are a good model for how airguns should be regulated. If you read the Navy report on their experience the only way they have had to retire a tank is damaged from the hydrotest. No tanks have failed for other reasons. So the test itself is the biggest risk. Not a very good system IMHO. There is no technical basis for the 15 year "design life". The Navy did their research to look at using longer tank life and to suggest a different test for tanks. Doesn't seem to have gone anywhere but I think their report is technically sound.
When the government does not regulate the design and/or testing requirements that doesn't mean manufacturers can just do whatever they want. If they design a product that later injures people they can count on being sued. They pay lots of money for liability insurance and it will be dropped if they make a serious mistake. That is the same way lots of design aspects of things we use every day are handled. Like our cars. Much more risk of death if our car experiences a serious safety malfunction. There is a regulatory agency looking at usage data and they will act after the fact to minimize injury/death but the government does not tell car manufacturers how to design the car. I wouldn't want them to.
Users have a role too, of course. Like putting gas in our guns that doesn't contain moisture. And not overfilling them. If you are worried, you can also underfill to add some safety margin. It's not very convenient to fill to 300 bar from a tank anyway so I don't. I also commonly underfill my 250 bar guns a little too. I'm not real worried about their safety but I think not stressing things to the limit is generally a pretty good idea.
The test data that has already been mentioned in this thread and posted on this site also provides an idea of the huge mechanical margin in at least the carbon fiber tank that was tested. It was intentionally damaged and still did not fail until well above the pressure my YH could take it to. The SCUBA tank which seems to have been all metal was not apparently damaged and failed at a much lower pressure. I take from that the carbon fiber containers tend to have more margin. But I'm not sure that principle applies to all carbon fiber reinforced tanks. And even if it does, that is only one part of the gun, the rest of the gun is undoubtedly metal (probably aluminum) and if any part of the gun that sees pressure fails there is a safety risk.
When the government does not regulate the design and/or testing requirements that doesn't mean manufacturers can just do whatever they want. If they design a product that later injures people they can count on being sued. They pay lots of money for liability insurance and it will be dropped if they make a serious mistake. That is the same way lots of design aspects of things we use every day are handled. Like our cars. Much more risk of death if our car experiences a serious safety malfunction. There is a regulatory agency looking at usage data and they will act after the fact to minimize injury/death but the government does not tell car manufacturers how to design the car. I wouldn't want them to.
Users have a role too, of course. Like putting gas in our guns that doesn't contain moisture. And not overfilling them. If you are worried, you can also underfill to add some safety margin. It's not very convenient to fill to 300 bar from a tank anyway so I don't. I also commonly underfill my 250 bar guns a little too. I'm not real worried about their safety but I think not stressing things to the limit is generally a pretty good idea.
The test data that has already been mentioned in this thread and posted on this site also provides an idea of the huge mechanical margin in at least the carbon fiber tank that was tested. It was intentionally damaged and still did not fail until well above the pressure my YH could take it to. The SCUBA tank which seems to have been all metal was not apparently damaged and failed at a much lower pressure. I take from that the carbon fiber containers tend to have more margin. But I'm not sure that principle applies to all carbon fiber reinforced tanks. And even if it does, that is only one part of the gun, the rest of the gun is undoubtedly metal (probably aluminum) and if any part of the gun that sees pressure fails there is a safety risk.
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In lieu of government regulation, in many industries and fields there are accepted methods, procedures, tests, safety margins. And these will be published, vetted and accepted widely within a particular industry. Just as the Titan submersible did not follow accepted industry practices for construction, engineering, testing and life limiting of submersibles and subsequent implosion and not surprisingly to anyone but the fellow who insisted industry practices were holding him and his brilliant concepts back. And the results of being cheap and passing off being cheap as being innovative instead were in the end, predictable.
Are there accepted general industry standards for air rifle HP vessels? I suspect not and that instead the companies that import these things rely upon engineers in the box factories for China sourcing. And sourcing or manufacturing elsewhere the design engineer would use accepted engineering principles for safety margins of the materials and cycles to failure (for materials which are known to have cyclic failures, aluminum, carbon fiber).
I would like to find that Navy report? Love to read it, not for argument but education. Is it on the web?
Are there accepted general industry standards for air rifle HP vessels? I suspect not and that instead the companies that import these things rely upon engineers in the box factories for China sourcing. And sourcing or manufacturing elsewhere the design engineer would use accepted engineering principles for safety margins of the materials and cycles to failure (for materials which are known to have cyclic failures, aluminum, carbon fiber).
I would like to find that Navy report? Love to read it, not for argument but education. Is it on the web?
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They do if you're asking them to fill it. A lot of what dive shops will or won't fill is simply up to the shop and the technician doing the fill. Some are very cautious and won't fill certain tanks regardless of hydro and vis while others will give you a "cave fill" 700 psi over a tanks rating if you ask.
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Exactly. I have worked for scuba shops off and on since high school. The stores have policies and so do the employees. I would check the VIP, the Hydro date and the external condition and age of the cylinder and valve and DOT and if anything and I mean anything I did not like, I did not fill. On certain steel cylinders when I was familiar with the owner (and cylinder) I would cave fill if requested. For example, I did the VIP and remember the cylinder. A VIP is a SCUBA industry accepted practice for an annual internal and external visual inspection. It is not regulatory like a hydro for cylinders in commercial service.
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To be clear, I meant cylinders. No way I would have filled direct to a gun even if the gun had a bottle. I would not have even if there was a hydro, VIP and DOT stamping, absolutely no fill. For one thing, a scuba store is not a gun shop and I would have quickly asked anyone to leave who walked in carrying a rifle for direct fill of any sort. If they brought a bottle in, if it had DOT, VIP, hydro and appeared unmodified and in good condition, then I probably would have filled (for free).
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I think the ASME Boiler and Pressure Vessel Code would provide guidance, probably in section VIII, Rules for Construction of Pressure Vessels. There may be useful content in other sections. In the U. S., a manufacturer that did not design in accordance with this code would risk increased liability. I'm not sure how it would work for those in other countries but it is a widely used and recognized code. It seems like saying your design meets it would reduce risk for those in other countries too. It is thousands of pages long. There are requirements for safety margins, welding, materials, and inspection. My degree is in mechanical engineering but I never designed pressure vessels.
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I did not mean to imply that most scuba shops would actually fill airguns if you brought one in, only that they would have the right to demand the same level of testing and inspection if they did and would certainly do so.
I actually did loan my s410 out to a dive instructor that I was taking a class from years ago however and we charged it up right on the shop counter.
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Same thing, the bleed valve is the one in the pump or compressor, once pressure is equalized you barely open the compressor/pump bleed screw/valve and the air will come out da gun
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Betcha if you do it right it will empty your gun,......... just open the bleed screw a fraction so air starts to come out just a bit.
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I think I have attached the report by the Navy on their experience with SCBA tanks.
View attachment navy-self-contained-breathing-apparatus-scba-composite-cylinder-life-extension-research-project.pdf
View attachment navy-self-contained-breathing-apparatus-scba-composite-cylinder-life-extension-research-project.pdf
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