HP tank Valves

[MikeS]

Genesis once bubbled...
getting pedantic yet?

(BTW, its PSIA, not just "psi", if you want to be pedantic )

What do HP SCUBA tanks have to do with the Professional Ski Instructors of America (PSIA)? http://www.psia.org/

Mike

 

[pescador775]

Sylvester, did you get the answer? It's all there if you sift through it. There are two types of K valves, the yoke type and the DIN type. There are two thread sizes in common use, 3/4"NSPT (large neck) and 7/8"NMT (small neck). The 7/8 is exclusive to HP tanks (3500+). The 3/4 is used on both LP and some HP tanks. That means that the 3/4 thread K valve, whether DIN or yoke, will fit all LP tanks and some HP tanks. The 7/8 is DIN only and only fits some HP tanks (PST and Genesis).

 

[Genesis]

with the large-neck valves is that to the best of my ability to determine only Genesis makes a manifold for them.

That's not so good if you don't like the angled ports...

 

[sylvester]

Now I need to identify what brand HP tanks a have 3/4" threads to see what the wgt savings would be using a hp120 with a lp k valve. I was looking at the OMS galvanized tanks but one of you have already mentioned they have 7/8" valves.

 

[BlueWaterDiving]

OMS I think they sell Faber's and they have a 3/4 neck.

 

[salty]

Isent there a reason HP tanks have DIN valves vs K valves. Something to do with pressure ratings maybe?:bonk:

 

[MikeS]

What would be the down side to a HP120 with a k valve?

After re-reading your original post I think what you were asking is can you get a HP120 tank with a yoke valve versus DIN, I assume you have regulators with yoke valves. If you did, since the yoke valve is only rated to 3410 psi you would have a situation where the tank was rated to 3500 psi but the combination was only rated to 3410 psi. Some LDS will only fill a tank with a yoke fitting to 3000 psi so your HP120 would now by a very heavy LP 100.

Depending on the regulators you are using, you might be better off getting the HP120 with a DIN valve and getting the part to modify your regulator to DIN. That’s what I did and after using the DIN valves I much prefer them. I still carry the part to change the regulator back to yoke for travel where yoke is the only option. There are also adaptors that convert a DIN tank fitting for use with yoke regulator but I personally don’t like them because they make the first stage stick out farther and then it hits me in the back of the head when I am horizontal and look up.

Here is the thread that I started when struggling with the same issue.
http://www.scubaboard.com/showthread.php?s=&threadid=9642
And here are some more recent threads on the subject:
http://www.scubaboard.com/showthread.php?s=&threadid=12992
http://www.scubaboard.com/showthread.php?s=&threadid=10547

Hope this helps,

Mike

 

[yknot]

A big reason a lot of fresh water divers choose LP tanks is the ability to overfill. OMS (Faber manufactured) rates their LP tanks at 4000PSI for 10,000 fill cycles. Using formulas posted previously, if you wanted 104 CF tank, you could: get HP104 and fill to 3500- or - get LP 80 and fill to 3400 apx (LP tanks usually at rated volume at 2640PSI, so 3400/2640 X 80 = 103 CF). Thinking in my area is that you get as big a LP tank as you can handle and then overfill. I am not condoning this practice, only pointing out where some of the preferences lie between HP and LP tanks. Also, OMS valves have a knock out center that would allow you to buy a LP tank and alternate between DIN and K in seconds. AFAIK, HP tanks only allow for DIN. With OMS valves it isn't the valve that limits you to 3400PSI but your use of a yoke on your first stage.

 

[pescador775]

Sylvester, currently, the only HP tanks which can be fitted with a yoke style K valve are the Faber series rated 3180+ psi. However, unless you like heavy, negative buoyancy tanks (some do) it would be best if you waited for introduction of the PST E series which will be similar to present HP tanks but the E's will have 3/4" neck. Since they will have a standard large neck it is possible to fit a variety of valves including a widely used hermaphrodite which allows you to connect with DIN or to crossover to a yoke regulator by inserting a small plug in the inlet of this particular valve. This will remove dive shop objections or wussiness and you won't have to request overfills of a LP tank either. Incidently, I use all yoke valves on my HP tanks. However, I had to machine some standard Sherwood and OMS's valves to fit the small neck of the PST's. Not a problem for me although there are some 'experts' out there who twitch when I say things like that. Incidently, make sure you have the right blow out plug regardless of valve type. Your LDS can advise.