Tanks: HP100's

[beeger]

Traditional high pressure steel cylinders come with a 7/8 UNF neck thread vs. 3/4 NPS for 3000 psi and lower for most other types. So, no, a regular yoke valve will not fit into a HP cylinder neck (for reasons beyond the scope of this message the 7/8 is actually *smaller* than the 3/4 neck size). There are convertible valves available that are actually a 200 (232) Bar DIN valve that allows for a yoke insert to be easily screwed in and out with without having to first drain the tank or anything like that. The convertible valves seem to only be available in the 3/4 neck size. I would assume that this is because the manufacturers don't want people putting these valves on HP cylinders. Keep in mind that the new Pressed Steel E-series cylinders which many people would consider HP cylinders actually have the 3/4 neck size.

Myself I like 300 Bar DIN. I use it on everything, and have for a number of years now. If I'm ever traveling someplace where I know I'll be diving cylinders with yoke valves I switch out the DIN kit on the reg I'm taking to the yoke fitting that came with the reg. This takes about 2 minutes, and any competent tech can show you how to do it on your own (no scuba-specific tools needed). You can also buy a simple, generic, spin on fitting for the reg DIN fitting that allows it to mate to a yoke valve. These take about 10 seconds to put on and can very easily be done at the dive site. I always have one in my save-a-dive/spare parts kit. The only disadvantage to the spin-on adapter being that it makes the first stage stick out a bit more than I like.