I think it's the last time at our shop for this guy, we have failed a few of the older HP PST tank's for neck crack's this guy has no care for me or the other shop tech's who have to fill his tanks, our price's are very fair for a hydro he has his own business and has the cash. But I guess his life or our's is not worth the hydro charge.
Hmmm...if you failed one of my HP steel tanks due to neck cracks I'd hope you limited the failure to refusing to put one of your VIP stickers on it. If you drilled it or X'd out the stamp, we'd have some serious words, I'd get a second opinion from a DOT certifired requalification facility and you may find yourself buying me a new tank after I took you to small claims court. If you failed and condemned a tank for a shop VIP that was just returned from requalification (hydro test) I'd be EXTREMELY upset as I would have already gotten the "second" opinion as it had already passed the legally required hydro and VIP done by people who do it for a living.
I have no objection to hydro test facilites condemning tanks for cracks, failed hydro tests, etc as they are required to render the tank unusable by law. However I am not inclined to allow a local dive shop the same lattitude to do so based on their opinion that a tank failed what is only an industry required annual VIP. In that case, unless I know and trust you, I'm probably going to want a second opinion and/or see the evidence myself.
The difference between a "crack" and a "fold" in any tank is important as one will disqualify the tank and the other is an entirely normal artifact of the manufacturing process. Not everyone knows the difference. In regard to a steel tank, a crack is exceptionally rare and a crack in a steel tank, especially an HP tank that is by definition very young in the time scale of steel tanks, would statistically raise suspicion.
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In terms of stamps, in 25 years of diving, after numerous hydro tests, and after owning numerous older tanks with several hydro test stamps, I have never seen anything other than a custom stamp for the RIN number. Its possible they have just been incredibly good at spacing and aligning the letter and numbers, but I doubt it. A missing stamp or a poorly aligned RIN number or test date would be suspect for a forged stamp.
I agree with Oxyhacker that a forged bydro test would not be high on my list of concerns, especially with steel tanks that almost never fail a hydro test making it almost a legal formality on tanks that if they are ever condemned tend to be condemed due to rust and pitting.
However if you find one that is suspicious just pick up the phone and call the facility. They are required by law to keep the test records and, especially if the test is recent, they should be able to access the records and verify the test was completed. If it has been a few years, the records may be filed away somewhere, but they should still be filed by month and year of the test and should not be that hard to locate. At worst someone has to spend a few minutes scanning the test sheets that month for the customer's name and then verify the serial number of the tank and the test results.