If a tank fails, the authorities cleaning up the mess will follow up with the hydro test facility to review the test record and verify it was in fact properly tested. They will not be concerned with the shop who completed the extra post hydro test VIP, but will pull the licence of a test facilty that blew a test or falsified the results.
I also find it easier to trust a hydro test facility that generates 100% of their business from tank testing and does scores of tanks per day as oposed to a dive shop with staff who took a one day VIP course and inspect a few tanks per day - if that many. Its the difference between "experts" and "self-proclaimed experts".
Test facilities test lots of steel medical O2 tanks and welding tanks and do not get concerned about normal flash rust. Makes sense given nearly 100 years of successful service history indicating it is not an issue.
Some dive shop staff on the other hand, seem to practically have a seizure if you bring in an "O2 clean" or even "Nitrox" tank with flash rust inside. It is very much a double standard and one that I find hard to tolerate when the shop objecting to flash rust is coincidentally charging $125 or more to tumble and re-clean a set of doubles.
Personally I tumble my own tanks when needed, rinse them and then immediately dry them while inverted using air from a scuba tank and flash rust is minimal. Hot water is not required and when comparing one against the other, I am of the opinion that a hot water rinse is no better and may in fact be worse as the elevated temp of the tank potentially accellerates the oxidation process as opposed to a cold tank that takes only slightly longer to blow dry. A couple minutes with a moderate flow rate will completely dry the tank.
A phosphoric acid solution can speed the rust removal process and finishing with an even milder phosphoric acid solution can add enough rust protection to eliminate flash rust, but it is basically not worth the trouble.
I also find it easier to trust a hydro test facility that generates 100% of their business from tank testing and does scores of tanks per day as oposed to a dive shop with staff who took a one day VIP course and inspect a few tanks per day - if that many. Its the difference between "experts" and "self-proclaimed experts".
Test facilities test lots of steel medical O2 tanks and welding tanks and do not get concerned about normal flash rust. Makes sense given nearly 100 years of successful service history indicating it is not an issue.
Some dive shop staff on the other hand, seem to practically have a seizure if you bring in an "O2 clean" or even "Nitrox" tank with flash rust inside. It is very much a double standard and one that I find hard to tolerate when the shop objecting to flash rust is coincidentally charging $125 or more to tumble and re-clean a set of doubles.
Personally I tumble my own tanks when needed, rinse them and then immediately dry them while inverted using air from a scuba tank and flash rust is minimal. Hot water is not required and when comparing one against the other, I am of the opinion that a hot water rinse is no better and may in fact be worse as the elevated temp of the tank potentially accellerates the oxidation process as opposed to a cold tank that takes only slightly longer to blow dry. A couple minutes with a moderate flow rate will completely dry the tank.
A phosphoric acid solution can speed the rust removal process and finishing with an even milder phosphoric acid solution can add enough rust protection to eliminate flash rust, but it is basically not worth the trouble.
