SparticleBrane
Contributor
When talking about overfills on an older steel 72, are you talking about the "10% overfill" to 2475, or are you talking about bringing them up to 3000+?
And they say steel tanks last forever....
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itch808:Got my LP 72 steel tank back from hydro, and it FAILED! Original manufactured date was '74. It only had a little surface rust on the inside, but nothing major. AL80 here I come
The most likely possibility is that they screw up the hydro.
Very likely they didn’t follow the pre-hydro procedure as required by PST on ALL galvanized steel tanks.
There are many other ways that they could have screwed up the test.
I had 3 steel 72 fail hydro two years ago. They came from different places, but the same hydro facility condemned all three. For one to fail would have been unlikely, two highly improbable, three is statistically impossible.
I demanded the hydro data (they are required to provide it). To make a long story short: They replaced all three tanks after I examined the test data and had them re-tested for confirmation only (once condemned and the numbers have been XXX, the tanks can not be put back in service).
I insisted that the tanks be replaced with other steel 72’s in hydro. I didn’t care the age, but I didn’t want any new aluminum tank.
As I kid (in the early 70’s) I worked in a dive shop were we had a hydro station. I personally only performed maybe a couple hundred hydros, maybe more (I did not work full time). Since then I have become an engineer and have performed plenty of pressure vessel calculations and testing.
TSandM:
I respect PSI training, but that is incorrect. As long as a steel tank continues to work under its elastic limit the only events that will truly limit its life expectancy is corrosion or fire (extreme heat). Fatigue is not really an issue for the number of cycles a tank see in 30 years (or even 100 years).
I have tanks as old as 1957 and about 10 of my tanks are from the 60’s and early 70’s.
Luis H:
What exactly would they have forgotten to do? It was a PST cylinder. The guy there only told me when they had finished hydrotesting it, the cylinder was supposed to return back to its normal size and in this case it was a couple mm off. He said he wanted err on the side of caution and thought it was better to fail it. At least they didn't charge me anything for the test. Should I even bother trying to take it to a different place for testing even though they XXX'd it out? I was thinking scrap metal.
captain
Contributor
Ask him if he followed PST technical bulltin D100-E for all galvinized steel tanks. If he ask what's that or says no you more than likely got screwed. You can have them retest using the procedure in D100-E if they didn't do it the first time and if it passes then they owe you a tank. Once it is Xed out it's history.
My PST HP120 lasted a mere 10 years before it failed hydro miserably. Don't think I'll buy another one from PST after that. The shop did use PST's exemption procedure in the test.
oxyhacker
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Maybe true of industrial tanks, which see fairly regular lives, but pretty misleading when it comes to scuba tanks since a 30 year old scuba tank may have been filled thousands of times since new, or used one season then left in a basement for the next 29 years. Since steel doesn't do wierd stuff like age hardening, and it's generally accepted that service life of steel tanks is a function of fill cycles not years, as long as demon rust is kept at bay.
TSandM:
oxyhacker
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Anytime someone goes into the "err on the side of caution" line a warning bell goes off in my head. A hydro shop is authorized to test tanks according to very explicit DOT rules. Those rules have plenty of safety margin built in so there's nothing to be gained adding more. The DOT-licensed requalifier only has statuatory authority to test ACCORDING TO THE DOT REGULATIONS. The minute he starts winging it, or adding his own interpretation, he is exceeding his authority and no longer doing a legal test. The tank isn't required to return to the same size - it is allowed a little (10% of total expansion) permanent expansion. So from what you say the odds are pretty good they guy didn't know what he was doing.
It probably isn't worth having it retested - you still couldn't use it. And since they didn't charge you it is hard to get too angry. Still, it would be real interesting to get the test data from him - test pressure, total, and permanent expansion. A requalifier is required to log these figures and keep them and should give them to you on request. Post them here and we can tell you what they mean.
Oh, the PST bulletin has no official status. It's just something clever that PST came up with, but a shop isn't required to know about it, or follow it. So unless you get a shop to promise to go by it before they do the test, you don't really have grounds for complaint if they don't.
It probably isn't worth having it retested - you still couldn't use it. And since they didn't charge you it is hard to get too angry. Still, it would be real interesting to get the test data from him - test pressure, total, and permanent expansion. A requalifier is required to log these figures and keep them and should give them to you on request. Post them here and we can tell you what they mean.
Oh, the PST bulletin has no official status. It's just something clever that PST came up with, but a shop isn't required to know about it, or follow it. So unless you get a shop to promise to go by it before they do the test, you don't really have grounds for complaint if they don't.
itch808:
oxyhacker:
I totally agree with this statement. Actually, that first sentence is exactly what came to mind. The entire paragraph is perfect; I couldn’t have said it better.
oxyhacker:
I don’t agree with this statement. Destroying a perfectly good tank by an incompetent hydro operator actually makes me angry and it is not even my tank. This actually amounts to destruction of personal property.
oxyhacker:
That is a good idea. The hydro facility is required to provide the test data. As Oxyhacker mentioned, the test is very explicit and doesn’t really leave much room for interpretation. If the data shows that he "err on the side of caution", he needs to replace your tank. That is exactly what happened to my tanks two years ago. The operator "err on the side of caution".
oxyhacker:
You are correct in that the procedure described under “PST Technical bulletin D100” is not required by the DOT or any CFR, but it is required by the manufacturer. And it complies (doesn’t violate) CFR49. Not following a procedure required by a manufacturer may not violate codes, but IMO it is negligent.
The pre-test procedure will easily make the difference between pass or fail a steel tank.
drbill:
Although, I understand that this tanks are slightly more likely to fail than a steel 72, I would first suspect an improper hydro procedure. My understanding is that the pre-test procedure is imperative on this tanks.
This has been covered probably at least three dozen times in the tanks forum, but this is what they probably forgot to do (rounding out the cylinder before testing):itch808:
http://www.underctek.com/open/boards/pstd100.pdf
If your tank is Xed out, it's scrap, nothing more that you can do.
Roak
DennisW
Contributor
Walter's comment about overfilling probably is when the tank monkey at the lds fills your 72 steel tank to 3000lbs. It happens more than you think.
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