Valve Pressure Rating Vs. Tank Pressure Rating

[DA Aquamaster]

It's no problem. People use 300 bar (4350 psi) DIN valves on low pressure (2640) tanks all the time, because of the secure connection.

I think people get confused by the 300 bar reference. Just because the valve is designed for that pressure does not mean it will not work fine at a lower pressure with a different burst disc assembly. It is very rare for any diver to use a tank that actually has a 300 bar/4350 psi service pressure, at least in the US.

Many divers are not aware that the "300 bar" refers to a DIN valve with 7 threads as opposed to a 232 bar DIN valve with only 5 threads. The deeper 300 bar valve required on a higher pressure tank (over 232 bar) prevents a 232 bar regulator from being successfully attached.

Huh, I was told that was done to facilitate overfills.

Yep, those would be the people who use 300 bar DIN valves and two burst discs.