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I just bought this HP100, 3500psi Sherwood Right hand valve tank of the forum. It's got small neck threads and the 300bar valve. However I have a Worthington HP 100 and its buoyancy characteristics are different and I am off kilter diving them in sidemount. Does anyone have a Worthington they are willing to trade for the Sherwood. The Sherwood has a fresh hydro and VIP. Will sell out right for 200 if someone wants it. Call me 808 265 0282 Kyle
To the best of my knowledge, Worthington never made an HP. They have only made cylinders with the 3/4" neck.
It's a terminology thing. I think the OP knows Worthington never made an "HP" tank - at least in terms of being the same as the Worthington X7 and X8 series tanks.
To be accurate, any tank with a service pressure over 800 psi is "high pressure" per the DOT, so all scuba tanks in current use are "high pressure".
Sherwood is the entity that decided to call their special permit 3500 psi Genesis tanks "HP" - and marketed them with those letters implying they were "high pressure" when others were not. They also decided to reinforce the point by adopting the really stupid and unneccesary 7/8" threads (which are smaller than the 3/4" threads used in most tanks as they use different systems) in their "HP" tanks. They then followed that mistake up with their slant valve design, which most people don't like.
To avoid all the non essential BS Sherwood started with what amounted to non standard threads, everyone else just went with 3442 psi tanks to stay under the "magic" number of 3500 psi has defined by Sherwood.
The end result is that Sherwood "HP" tanks can be a real pain in terms of valve options, are harder to VP and a pain to tumble due to the smaller neck thread. And worse, the rest fo the world is left with klutzy nomenclature for the PST and worthington 3443 psi tanks and have to refere to them as either 3442 psi steel tanks, E7-100s, X7-100s, etc rather than just calling them a generic "high pressure" steel tank as other people insist on making the distinction that they are not "high pressure" tanks since Sherwood co-opted the term for their "HP" tanks.
DA, I didn't say they aren't high pressure. All scuba cylinders are high pressure. I said they aren't HP, which is a nomenclature that for over twenty years has refered to a particular series of cylinders that has the awkward skinny neck.
And I'm surprised that as learned as you are, you don't agree.
Well I did not intend to start this debate. Let me explain my lack of proper vernacular when it comes to these types of tanks. I have been rec diving for about 7 yrs now with a lot of military diving experience 100% o2 ccr and Scuba. However it wasn't really until I just recently got into cave diving that I started into all this 230bar and 300 bar valves and 3442psi vs 3500psi tanks and tanks with different neck sizes. It's a steep learning curve. Compared to diving mainly aluminum 80's in single or double configuration which were all filled to 3000psi, it's ingrained in me to think anything rated higher has got to be "HP". My question is this. If so much emphasis is put on neck thread size this and valve bar capacity that, then why when a tank rated to 3442psi @70 degrees F is brought to most cave shops in the area it's common place to get a cold fill of around 3600-3700psi? Is that a case of creative fill pressure or is that common place?
Don't worry about it, it only serves to keep your ad on top :-DQuote:
Originally Posted by fewproud0001
I agree completely, I guess I was just taken off guard by someone using "HP" correctly in that regard.Quote:
Originally Posted by Slüdge
In any event, the OP now understands the difference.
The 232/300 bar valve issue is not an issue once you get past the marketing hype, nor is the 3442 versus 3500 fill presure.Quote:
Originally Posted by fewproud0001
For what its worth, most cave divers I know are fine with 232 bar valves and manifolds and prefer them over the 300 bar variety. The difference is that 232 bar valves are 5 threads deep while the 300 bar valves are 7 threads deep. They were designed that way to prevent 200 bar regulators from being used on 300 bar tanks as the shorter 200/232 bar reg connection would not see in the deeper 300 bar valve.
That made sense back in the day when some regs were intended for 200 bar pressures and were not approved for use at higher pressures up to 300 bar (4350 psi). However the reality in the US is that gas fills are in the 3300-3600 psi range and most regs handle that pressure just fine so there is no real need to "protect" them from 3500-3600 psi fill pressures.
In any case the difference is not related to the strength of the valve as either valve is more than strong enough for 300 bar pressures. In most cases, I doubt you have more than 3 threads in face to face contact anyway in either valve.
Some divers regard 300 bar valves as less desireable as they are longer (2 more turns to secure the reg), more prone to damage if the tank falls over and have two more threads to trap water that could find its way into the tank during a fill. I don't discriminate against 300 bar valves exactly, in fact I bought one a couple weeks ago, but mostly because it was old stock in the shop (the guy ordered a 300 bar manifold but later decided he really wanted a 200 bar) and as it was not going to sell anytime soon, so I got it for cost about the same as my cost on a pair of 200 bar DIN/K valves.
In N FL the average cave fill is 3600-3700 psi and shops tend to fill both 2400 psi LP tanks to that pressure and use the same pressure for 3442 psi tanks. The 3442 psi story is interesting but not real relevant. What matters is the average gauge is not going to hit 3442 on the money anyway so practically it is a 3500 psi tank that will get 3500 psi fills. In N FL, where cave divng is the norm, most cave divers use some variation fof diving thirds, so a 3500 psi fill woudl require the diver to round down to 3300 psi and use 1100 psi thirds rather than the 1200 psi third he or she would have at a 3600 psi fill pressure, so most shops try to ensure that tanks leave with an honest 3600 psi in them w.hen cool so that usually translates to a 3700-3800 psi initial fill pressure even with a water bath
Exactly - a 3500 fill might as well be 3300.Quote:
Originally Posted by DA Aquamaster
Good luck selling your tank, and thank you marine!
Semper Fi!