XS 80cf Tank Looks Vintage.

[SurfLung]

Worthington Cylinders HP 80cf Compact Steel Tank
- I like small tanks and was attracted to the vintage round bottom and galvanized look of this new high pressure tank from XS Scuba. It looks so much like the 38cf tanks used for Mike Nelson's compact twin tank harness... I figure somebody will be tempted to use these for a vintage looking twin tank set like those. So, here's some info:
- Length is almost exactly the same as a U.S. Divers aluminum 50cf... 19.7" not including the valve. Diameter is 7.25" which is too wide for Allan's tank bands. But, I got some stainless T-Bolt Hose Clamp Bands from MSC and mounted my Travel Harness real solid with them. Empty weight is 28 lbs.
- High Pressure means they're marked for 3,442 psi... Which also has the marking of 230 BAR on the tank... This matches the marking on my Phoenix yoke (Yay!)
- 80cf is a lot of air for such a small tank. This should be a fun rig to dive.

[Robohips77]

Just a thought for you and you probably already know this one. The amount of cubic feet of air per one hundred psi. Steel 71.2 with 2250 PSI has 3.16 cubic ft of air per 100 PSI, XS 80 has 2.32 cubic ft at 3442 PSI and the aluminum fifty pictured provided it is a 3000 PSI cylinder has 1.66 cubic feet of air per 100 psi. I too do like the shorter cylinders and with my hips the smaller and lighter they are the better. I have a RENE 38 (I think) and it has a rated working pressure of 1800 psi. and it has 2.11 cubic ft of air per 100 psi. So if you have a SAC rate like Greg Barlow he could get by on my one 38 for 15 dives in one DAY! Nice looking tank. Robohips x 3

[luis]

A small correction:
A 71.2 cu ft is at 2475 psi; therefore you have 2.88 cu ft per 100 psi.

Tanks are rated/ advertised as having the maximum possible capacity. In other words, tanks that have a “+” in the original hydro date stamp are rated with there 10% over fill.

[Robohips77]

A small correction:
A 71.2 cu ft is at 2475 psi; therefore you have 2.88 cu ft per 100 psi.

Tanks are rated/ advertised as having the maximum possible capacity. In other words, tanks that have a “+” in the original hydro date stamp are rated with there 10% over fill.

That + rating if it is followed all the way through most of my cave training... about 2 of the 6 manuals of my training on tanks sizing and their non similarities are based on the no + ratings on the tanks. The graphs and information presented in them is incorrect and I based a crap load of dives.... over 600 safe cafe dives on way too much air!. I am not being sarcastic here Luis I am being very serious. I am glad I always followed my rule of thirds plus two hundered PSI. Good point and now I will recalculate my new triples that are OMS 45"s or are they 48"s?

[SurfLung]

You guys are a bit beyond me here. Are you saying my 80cf tank is not really 80cf at the 3,442 psi pressure that's stamped on it?

[luis]

I have actually measured the volume of most of my steel 72, using water. I precisely weighted the tanks and the water it can hold. I have done various PST and Norris tanks (plus one Walter Kidde).

I also have manufacturer data from PST.

The equivalent air volume that I have measure range from 70.3 to 72.2 cu ft at 2475 psi (most of them are somewhere around 71 cu ft).

This variation in volume is not surprising considering the fabrication method used for this type of pressure vessel.

That + rating if it is followed all the way through most of my cave training... about 2 of the 6 manuals of my training on tanks sizing and their non similarities are based on the no + ratings on the tanks.

I guess that I am not surprised about this statement considering the amount of miss-information in our sport (especially when it comes to tanks and some other aspects involving physics); it seems that cave diving training is no exception.

You guys are a bit beyond me here. Are you saying my 80cf tank is not really 80cf at the 3,442 psi pressure that's stamped on it?

Those tanks are rated at 3442 psi since that is the only working pressure… there is no overfilling.

Now to confuse things a little, I also measure my wife’s 80 cu ft HP tanks (made by PST, original hydro 2005). The volume in her tanks came out about 85 cu ft at 3442 psi. This is very strange, but I checked my measurements and calculations several times. I don’t think that I made a mistake, but I will not double check until next hydro test (I don’t feel like getting the inside wet only for this purpose).

I don’t know if your Worthington tanks run different than the advertised.

I am very surprised for these two PST tanks to be advertised that much lower than actual. The 5 cu ft difference on an 80 cu ft (or 85 cu ft) tank is a large difference. IMO it is too much difference to be explained with the normal fabrication variances.

[SurfLung]

XS High Pressure Tank Features
- Besides the high pressure and air volume in these new tanks, I like the valve they come with, too. It has a screw out O-Ring sealed center so a DIN connector can connect to it while still retaining the capability for yoke type regulator connections. My dive shop says he has to use the DIN connector to fill it to the full 3442 PSI. Finally, the valve shows a red ring when it's turned off and a green ring when it's turned open. The one in the photo was turned off. A quick visual answers the question, "Is my air turned on?"
- I asked about the potential for over fill and he said most dive shops don't have enough pressure capacity to over fill this tank... He figured the fill station would max out before the burst disk gave way.
- The round bottom actually comes with a nice tank boot. I just like the looks of it without the boot.
- There's a whole series of these tanks in different sizes and the specs on dimensions, weight, and buoyancy are at http://www.divegearexpress.com/gas/steel.shtml. They have a few real interesting information links there, too. One is "How to Select a Tank" and has an article entitled, "The Big Lie About Capacity" that I think addresses what you guys have been talking about above. Also some good info on steel vs. aluminum.
- Best Regards, Eb

[SurfLung]

- I dove this tank recently with my Phoenix DAAM and a 2mm wetsuit. It was a certification checkout class at a local 12 ft deep pool... I tagged along.
- The specs say this tank is 9 lbs negative in sea water when full. I found neutral buoyancy with just the tank and no weights... I'm 6'2" and 240 lbs.
- The students were struggling with their BCD's... I could hear them inflating constantly. They all ran out of air with their aluminum 80's. I kept going another 25 minutes until closing. I dove 1.5 hours and still had 1,000 PSI... Nice tank!