burst discs are just thin pieces of copper, basically shim stock punched in a circle. And as sailors might know, copper in salt water
, seated in a steel or aluminum fitting, it going to self-destruct. They are supposed to be replaced every year as part of the annual maintenance
on the valve. There's no safety
disc on a SCUBA tank, no burst disc on a SCUBA tank. The disc is on the valve.
But that's rarely done. Either it costs the shop time and money
, or they have to explain why they're charging
to do it, or, everyone can ignore it and then just charge the customer for a new disc and a fill when it fails, which is always more entertaining to watch. (ahem.)
I always used to maintain my own and I'd coat it with Krytox on both sides to ensure it couldn't corrode. And of course, rinse the valve after diving to get any salt water
out of there. Krytox because it can be used on both sides, isn't a problem inside the tank, and it doesn't go anywhere or wash off the outside.
The early aluminum tanks were supposed to be "forever" but then there was the kerfuffle about faulty necks. Quickly "resolved" by "enhanced" VIPs using ultrasound to look for stress cracks in the necks. Except...Gungho, another $20 to add to the regular VIP and most shops didn't really know how to use them. The normal thread tappings in the neck were sometimes mistaken for flaws and perfectly good tanks sometimes condemned as a result.
Another sadly good reason that many shops, if not most shops, encourage mystic FUD instead of trying to educate divers. If you have ever had a tank hydro'd and VIP'd? Every dive shop insists on performing a VIP after the hydro. Which is most peculiar, since the US DOT regulations
require the hydro shop to perform a VIP and only continue to do the hydro test if the tank passes that VIP. So if the tank has been hydro'd...it has just been VIP'd as well. The second VIP is totally redundant, a rip-off by the SCUBA shop.