Response from AF on Hydrotesting…
I spoke with AF today and they said the following:
* Tank does NOT require visual inspection every year.
* Tank DOES require hydro every 5 years.
* Tank valve needs to be removed counterclockwise.
* Tank valve thread is M18/1.5 and can be tested by Paintball and some SCUBA depending on their adapters.
* AF does NOT hydro their own tanks.
Wok, you’ve got a lot of experience with the tanks… is the thread and removal information correct?
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80grit was going to send one to be tested a while back, that’s the only one I know of. Being a used tank and not knowing the history, I would do the same.
I have one that is 3 years old, and I don’t know it’s history, so in 2 years I may have it tested. That will probably be the last time for me.
🙂
X2?
😆
so, how many Airforce tanks hydroed to date?
🙂
Good find!
Great info!
To be frank,
These ali tanks are a T6 temper, that is already pretty “brittle”.
The T6 temper is a precipitation hardening of ali that stresses the crystalline structure therefor bringing the metal closer to it’s yield strength. That means it can withstand more force without deforming. But it also means when she blows she’ll blow without much warning.
What they measure with a hydro is if there is no plastic deformation. Or a to great elastic deformation. In short the water that is displaced need to come back in the hydro tank otherwise there’s something wrong in the state of denmark! It is only a before after comparison.
That would probably mean they will show no signs of fatigue before actual failure. The only thing Hydro does is give you a good feeling about the tank!
Don’t get me wrong it is a good thing that it’s beeing done both it’s not a 100% reliable test. And I would not discurrige anybody getting there tank hydroed!
I don’t proclame infinate wisdom just going with what I have learned about metallalurgy. So correct me if I’m wrong!
Cheers,
Marc
Ah, I stand corrected. 😯
Looks like it could be pretty good at detecting small amounts expansion. For our itty bitty tanks it may be harder though. 😉
Looks like a pressure cooker… 😆
I saw a hydro tank that looked like a big fish tank. 😕 Maybe that was for filling or something else. That looks far safer than an open tank. 😯
Thanks for this post, good information!
My mistake, Brittle is the wrong term, I should have said that it indicates Fatigue due to operational duty since the last hydro.
I should have posted a link to Wikipedia at the beginning of this article instead of relying on my memory of the process: http://en.wikipedia.org/wiki/Hydrostatic_test
If it’s too brittle wouldn’t that be a product of the metal when the tank is formed. As I understand it metal won’t changes it’s internal properties (become more brittle) unless heat is applied.
The reason why a hpa tank would break is the fatigue of the metal after cycling over and over… The composition of the metal (it’s density and addition of different type of metal) would constitute it’s ductility or brittleness…
For these tanks your probably looking at a couple thousandths of an inch expansion (maybe as big a a hundredth). I don’t know of any water tank capable of measuring that little of a difference in volume. 😕
The tank is filled with water to 5/3 pressure and placed in a water container. They measure how much of the outside water is displaced by the tank expanding. If it displaces the required amount of water then it’s considered flexible enough for another 5 years.
Zero or little displacement = too brittle.
If the pressurized water escapes then there’s a leak.
If the tank ruptures then the pressurized water escapes but doesn’t explode because water isn’t compressible like air.
The only workout I get is when I take my SCUBA tank to/from my car for a refill every couple of months. 😛
“pUmP WORK OUTch”
As far as water testing is concerned, I wonder how they determine a failed tank? What happens to the tank if it failed?
If it blows up they usually consider that a failure.
NOT meaning to hijack a Very Good Thread here, check out:
“pUmP WORK OUTch”
As far as water testing is concerned, I wonder how they determine a failed tank? What happens to the tank if it failed?
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I have read a lot of mumbo jumbo about hydro testing but I have not read
anything from anyone that has found a business that can, will, or has hydro
tested even 1 AF tank….. Even AF did not give out any information on a
business or business that are hydro testing their tanks…. I don’t think it has
been done by anyone as of yet….