Reread my earlier posts. For tanks rated up to 3300 psi, the DIN is "optional". Above this pressure, industry practice requires DIN even though manufacturers know that the MODERN yoke screw attachment is safe up to 4000 psi. Use of DIN valves on low pressure tanks is becoming more wide spread due to myths, due to the unusually cautious attitudes of today's divers, but also due to standardization of the individual diver's kit.
The DIN connection is actually an industrial connection of the type normally used for permanent(not temporary) installations. It's similar to the valve/tank screw in connection in this regard. It is more secure in a mechanical sense because of the long threaded insert. It is more secure at the O ring because of the closed design. However, a change to DIN fittings is not needed by the majority simply because the conditions for failure of their yoke screw connections are not present. Moreover, the DIN valve connections can trap water and grit making on board tank filling a bit of a chore, especially if the tank has no pressure to clear it. The exposed machine threads and nozzle are suspect. (Don't drop one of those things).
The yoke valve is just so easy and reliable, it's hard to beat. When one of my ancient steel tanks failed hydro, PST replaced it gratis with a new 3500 psi fitted with DIN. This thing sat in my diving locker for a year. I bought a set of adapters, looked at all this junk, then at some point thought, "what am I trying to do, here?" I got off the duff and machined a new yoke screw valve to fit the hp tank neck. Later, I did a couple more. You see, with all my equipment, compressors, etc, all standardized to the older valve, I certainly didn't need yet another set of adapters to mess with. Everything worked fine, BTW.
