filling 72's

[akcaver]

Mine passed hydro earlier this year and have been getting filled to 2800-2900 since.

Dont get me wrong, I "accidently" filled a 72 to 3100 this summer at the shop, and nothing happened, just havent done that since

[FW]

The neck isn't as big an issue as wall thickness. 72s have thinner walls than most other steel tanks.

As for exploding, the only ones I have heard of exploding were due to heavy rust inside the tanks. The incidents went way down when the VIP program started. Since they walls are thin, it wouldn't take very much rust to weaken them.

[Hydrogirl]

If they pass hydro, they held 3750psi for 30seconds.
I have an old set of 72 but I don’t fill more than 2500psi. The best way to judge the health of your tanks is by getting the % permanent expansion from your hydro tester.
Keep in mind that DOT allows 10% permanent expansion, most tanks will show 0.2 to 0.8% mine are at 4% this is why I don’t go pass 2500psi.