drywaterdiv:
VIP are governed by law (DOT) A DOT approved test company can fail a tank from a VIP. A VIP is done prior to doing a hydro test. If it fail a visual the tank then has the DOT marking x out.
The visual inspection is done as part of the hydro test, but it is done after the hydro for a couple of very good reasons.
You want/need to inspect the tank after the hydro test to ensure it is dry inside. And you need to do it after the hydro, especially in the case of 6351-T6 tanks, as any incipent cracks may enlarge under the 5/3rds test pressure. It is not unknown to have an undetectable or within tolerances crack prior to the test and then have the tank either fail during the hydro (due to water leaking through the now much larger crack) or to have the tank then fail the VIP due to a now longer crack.
As a matter of practice, a test facility may drop a light down the neck prior to the hydro to look for gross indicators the tank is not worth testing, but the visual inspection that counts will come after the hydro.
And as indicated in a previous post, the test facility visual is required by law, but the dive shop's visual inspection is just a scuba industry standard, is not governed by law and does not grant the tester the authority to condemn a tank.
The shop VIP will still serve the dive shops purposes (ie. we don't think it's safe so we refuse to fill it, even if a legally required visual is not due for another 1-4 years when the tank is due for requalification (hydro testing).
It also serves the shops purpose since as soon as the tank comes back from hydro, as most shops gouge you for their VIP and sticker even though it has obviously just passed the legally required visual inspection by the test facility. That is just a blatant example of making money of a customer for absolutley no reason. They would charge $0.50 for the shop VIP sticker and leave it at that if they were not interested abusing the diver's checkbook. Condemning the tank for an unoffical industry standard VIP, with the knowledge that the diver is possibly going to then buy a replacement from them, is an even more blatant abuse of the customer.