HPA Tanks and Hydro

[Deerslayer]

I have a Ninja 3000 PSI, 48 cu in aluminum HPA tank that is about a year out of hydro. Testing this costs within a few bucks of buying a new tank, and in the past that is exactly what I have done, replacing and recycling the old tank. Recently I've had some second thoughts. I now have two of these in hydro, one within two years out.

First, my usage and condition. I use my marker and these tanks to scare away deer, raccoons, and the occasional squirrel clever enough to pillage our bird feeders. I rotate these tanks, charge them up, use the air, go to the next tank, charge them, etc. They are charged maybe 4 times a year (sometimes maybe once). The tanks live indoors, and every one of them looks brand new. None have been ever dropped, the paint shows no chips, scratches, or dings. I took the new tanks to a scuba shop, the guy scrutinized the stampings, determined the tanks were able to be pressurized and filled them. I've taken my tanks to a local paint ball field, the kids grab the tank, fill it and take my cash. Since they charge by the 1000psi and rarely look at the gage, I've started to tell them what I need ("2500psi, please, or this tank only needs 1000 to top it up") so I don't pay for air I don't get. Do they look at the stamping on the tank at all? You have to be kidding. I've seen guys with ratty old tanks (in or out of hydro is unknown) get air at this field.

From a metallurgical point of view, metal fatigues with repetitive stress. My tanks clearly receive very very few pressurizations compared to say those rental scuba tanks at the dive shop. None of my tanks have been charged w/ air more than a couple of dozen times over their hydro lifetime. I have no idea what time does to the strength of the tank - we are supposed to junk them after 15 years.

How often has anyone here heard of a tank exploding?

Are you religious in getting your tanks hydro-ed when they expire? Do you junk them at 15 years?

[k_obeastly]

Unless I am mistaken, the junking after 15 years is only the fiber wrapped tanks, and yes I do junk those. The fiber and the aluminum inside expand at different rates as they heat and cool causing more damage than a purely aluminum or steel tank (or that could be just what they tell me to justify demanding I buy a new tank).

From what I have seen on forums and/or heard, the appearance of a tank that is going to fail hydro is enough for concern before you ever send it off. That said, it is still a hand grenade and I won't be the one to tell you it's okay to play with it.

[Ecapnation]

3000 psi letting go alone is enough to turn your head to mist... let that sink in.

While I've never seen one explode I've seen threads fail which caused a tank to launch with enough velocity to go through two cinder block walls, a sheetrock wall, break through a glass counter, and finally come to rest squishing two cases of paint against another wall.

And that was only filled to 2000 psi before it failed.

[Shaftski]

i would be most concerned about the structural integrity on inside of tank vs. outside. a tiny amount of water vapor stored at high pressure can do a lot of damage to a cylinder over time. if you know for a fact that the air that went into the tanks was pristine breathing quality air with no moisture then you might be ok. otherwise you are taking chances with safety.

it's a common problem with airguns cause most of those shooters self fill and don't invest in proper air drying/filtration for their pumps and compressors.

[Grendel]

I abide by the DOT rules and regulations for a few of simple reasons:

• Not worth the hassle at a field to push the envelope even if you are technically correct. The venue has the last say in what can or cannot be used
• The DOT rules came about not because they want to tell you what you can or can not do but because bad things happened to people historically and these were safe standards that idiots will not get hurt with if they just follow the basic rules.
• The cost over time for compressed air (gas) bottles is insignificant. Yup costs are high but we get to used them unlimitedly for years without even testing them and magnitudes longer if we get them tested.
• Liability - if you find you are violating DOT (US) or ISO rules and something goes wrong any insurance you might think you have can back out because you were not using it correctly. That is bad enough when you are the only one affected but what about if you affect someone else. No/limited insurance assistance and law suits ......good luck.
• So a 3.5-4oz CO2 bottle has an internal surface area of ~28 sqin and for argument sake we will use 1800 psig of pressure for that little bottle (we'll avoid the phase change aspect). So that is (28sqin X 1800psig)/2000 lbs = 25.2 Tons of energy on a catastrophic failure that needs to be released. Now this is comparatively small in size and 1/2 the pressure of your bottle. I think I will try to be safe on this one, the energies we casually work with in paintball should not be taken lightly. If not for your own sake think about those around you.

[Trbo323]

Unless I am mistaken, the junking after 15 years is only the fiber wrapped tanks,

As a general statement this is correct. There are exceptions but any tank that is stamped "3AL" is not one of them and that's the most common certification.

As for tanks rupturing, it's extremely rare. I can't say I've spoken with anyone who has had direct experience. It's always "I knew a guy" etc. The actual burst psi of a 3k tank is somewhere around 7 or 9k so there is lots of room for error and deterioration.

Sent from my motorola edge 5G UW (2021) using Tapatalk

[Grendel]

Yup, I have never seen a solid metal cylinder itself rupture (but have seen pictures/samples of them in past training). Typically in my experience the failure point is the valve itself or the bottle threads as Doc mentioned. I have seen fiber wrapped bottles rupture, one in paintball and a few in industrial settings. I used to work with high pressure systems and bottles when I was still working/supervising failure analysis labs (been a little over 3 years) and I am definitely not running scared of this stuff but the risk to benefit of ignoring established HP regulations and practices is just not worth it.

[Hp_lovecraft]

I’ve never seen a tank fail but I’ve seen a few tanks come off valves. That’s scary enough!

plus those damn smart remotes. Those were a menace.