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I've been diving with PST HP tanks for a while (rated to 3442 psi - technically not high pressure, but certainly higher than the 3000 we typically see in AL tanks). The issues really depend on the shop you fill at.
There are a handful of shops that I can fill at, depending where I am going and most of them (except one) keep their banks sufficient to fill to the rated pressure. Of course, if there is insufficient pressure to fill to 3442, you're going to end up short.
The issue with the shops that do have sufficient pressure in their banks is the time required to do a proper fill. As already mentioned, you could fill it to 3800 psi and let it cool (though you're not really supposed to do that). So to get a proper fill to the rated pressure does require a bit of time which some shops may not be willing to spend, so you end up short of the rated pressure. How short depends on how quick they fill (and to how much) and let you go.
No problems getting HP tanks filled. I am somewhat surprised your LDS can't do it...... most outfits can easily fill to 4K psi. Maybe he doesn't want to? Have you asked why he can not fill to the rated pressure?
has anyone bought a hp( 3442 psi) tank only to find your local dive shop cant fill it to the rated pressure? so in order for me to get 100cf or close i have to buy a hp 120
All of the shop around here have the capability. Willingness or ability of the fill person to pull it off is the big wild card. There are shops and especially boats that cannot do a pseudo HP or HP fill.
If it's possible leaving the tank over night to get a fill, cool and top off will get you there. A careful fill (bleeding in over about 15 minutes) to about 200 PSI over will get you where you want to be. Lots of stuff can effect the results. Some shops don't bank HP or at times will top-off with hot gas right from the compressor. If you hit the shop early and they happen to have cold full banks you can get very nice results.
Originally Posted by salt h20
and also am i more likely NOT to get a hot fill with 3000psi in my rated 3442 tank due to less heat buildup due to not packing as tight?
Thats the bottom line. Technique can alleviate a lot of the difficulty but the physics are inescapable.