Unless it's a California thing, they likely just need a new hydrotest when due (except for the old Lux bottles). I know it's hard to believe, but sometimes you'll find a fill station operator that will not know what the frack they are talking about. When I got started, I'd ask the same question of 3 shops and get 6 different answers. I'd push for more background. There's not federal requirement for for fill station operator training (outside of the hazmat component) so a lot couldn't even tell you what they're looking for when they do a VIP inspection, much less a tank fill and so there is a lot of hand-me-down misinformation floating about. It's their compressor and fill operator, so in a lot of cases that's what you get stuck with.
Some hydro shops don't always know what they're doing (not sayin' who) and if they have the equipment they use it because that's what Rick showed them before they left (depending on the quality of their training and what they spend most of their time testing (probably NOT scuba cylinders)) .... I've seen tanks with the UE and VE marks that didn't need that (that's in addition to the hydro - I don't think VE or UE testing will measure the flexibility and resiliency of the metal and that's what hydro is testing).
So, the hydro is really what's required and having them hydroed should be no problem.
However, the old '86 Lux Al bottles are not really serviceable in many locations because of the ongoing extra testing required (not a gumment reg - usually a fill or test shop standard might adopt hard-date cutoffs). I have an 87 Luxfer (cherry condition - actually cherry red, unused pretty much, bright, clean shiny insides, no visible cracks, one hydro subsequent to manufacture done in 1996. It's really pretty and I would have no hesitation to use it for diving if it was properly hydro tested (with VE) and subsequent VIPS with VE - but that gets expensive. I bought it and gave it a new job as a valve-holding fixture for rebuilding valves (hard to hand-hold a valve for torquing the packing assembly on the stem or the burst disk - the old tank will do fine in that role.).
It's not about nice and clean. The 6351 alloy had, IIRC, almost 4x the amount of lead than 6061 (not lead poisoning risk like eating paint chips, but if you ate a scuba tank I think you'd have other issues to worry with). A few of the 6351 tanks did develop cracks in the shoulders and necks over time just holding pressure. On fill, primarily, some could/did rupture. People were killed or permanently maimed (like losing limbs or eyesight).
So, it's not so much in
diving that the problem of sustained load cracking (SLC) in the shoulders and threads becomes dangerous or deadly (but could, I suppose happen in the right set of circumstances). It is in the filling process that tanks have tended to blow up with the force of a hand grenade (Just for reference I once figured the internal surface area of an S80 aluminum tank and when you put 3,000 lbs of pressure on each of the internal square inches, the total stored force, IIRC, exceeded 1,000,000 pounds).
So if using a scuba or paintball compressor or are using a whip to transfer gas to them from other scuba, it's filling and moving gas around the shop is where
I'd worry most about them and make sure they were up to tested spec. But that's me ...
If your other tanks are getting close to their hydro deadline, just have them hydro tested (hint: the dive shop may not be the best place). Call around to some industrial gas or fire extinguisher service companies in your area. The DOT has a searchable index of RIN holders by area. May be better flexibility in finding one.
portal.phmsa.dot.gov
Type in your location and the radius you wish to search. It will put them on a map. You will probably need to find one that will do scuba tanks - not all will - and it will show folks that are not really hydrotesters too so there's still a little leg work involved, but it may beat a long commute.
