PST Steel 72 3000 PSI?

[Dubious]

Greetings All,

To make a long story short, I picked up 2 steel PST tanks way out of hydro (78) along with 2 pairs of jet fins and 2 Scubapro MK7 regulator sets for $100.00. Both tanks just came back to me with a new hydro stamp. Both tanks appear to be the same height and same diameter but one is rated at 2250 and one at 3000. My LDS owner and manager said they have never seen a PST steel 72 rated at 3000 pounds and couldn't believe how heavy it was. Both valves are Shearwood selpac. I am wondering if any of you have more information on the 3000 psi tank and insight into why it is so much heavier than the 2250 tank.

 

[Luis H]

The steel 72 is actually about 71 cuft when it is filled at 2475 psi. That is the cylinder stamped with 2250 (psi) filled with the extra 10%.

On average, the steel 72 has:

an outside diameter of around 6.9 inches

it is around 25 inches tall

the average wall thickness is about 0.176 inches

with a valve and boot it weights around 30 pounds (empty), 35 to 36 pounds full.


The 3000 psi stamped cylinder was actually called a steel 95 (that is what I have heard), but they are actually around 93 cuft when they are filled to 3300 psi. That is including the 10% overfill with the plus(+) stamp.

This steel tank has:

An outside diameter of around 7.0 inches

it is around 25.25 inches tall

the average wall thickness is about 0.23 inches

with a valve and boot it weights around 40 pounds (empty), around 47 pounds full.

When empty, these cylinder is about 7 to 8 pounds heavier in the water than a steel 72. I measured the displacement of my two cylinders.



So they may look similar, but they are two totally different cylinders. The wall thickness alone is 30% thicker.

I have two of those cylinders. But I haven’t dived them yet. They are very heavy.

It is a great cylinder if you need that much air and you can handle that much extra in the water weight. That would remove about 8 pounds of lead from my weight harness, which would be great. But here in Maine I very rarely need that much air. I would get cold and bored long before I consume that much air. Most of our dives are shallow.

 

[Dubious]

So they may look similar, but they are two totally different cylinders. The wall thickness alone is 30% thicker.

Thank you so much. They look so similar. That 3000 psi tank is heavy. I must admit I did not measure them, just stood them side by side. The guy I bought them from did not remember much about the tanks. All he said is the heavier tank was his and the lighter tank was his wife's. Going to go dive them today or tomorrow with my wife.

 

[Luis H]

The outside dimensions are similar. The wall thickness is what makes it so heavy and what gives it the higher pressure capacity.

Overall the weight is not too bad. The heavier tank is 10 pounds heavier, but you can remove about 8 pounds of lead weight.

Keep in mind that at the beginning of a dive you are also carrying about an extra 1.6 pounds of air.

71 cu. ft. of air weights about 5.3 pounds
93 cu. ft. of air weights about 6.9 pounds

 

[AfterDark]

I have 2 of each of those tanks and that's the way I tell'em apart by their weight. One of those 94 on my SS B/P and I use 4 lbs of lead.

You'll find that 94 is negative full or empty just a matter of how much. I weighed it if I remember right it was 48lbs full. Nice score by the way! Does that MK7 still Honk?

 

[Dubious]

Does that MK7 still Honk?

I don't know yet. Tanks were what I was after. Both sets seem to be in very good condition but one is missing the dust cover. I will have to hook them up once I have a tank low enough for them to honk. I will likely post what I have in the vintage or regulator section.

 

[rsingler]

Not to derail, but just now putting the finishing touches on a new thread on "How to put the honk back in your Honker." It'll go in the DIY/Repairing your own gear forum.

 

[Dubious]

Not to derail, but just now putting the finishing touches on a new thread on "How to put the honk back in your Honker." It'll go in the DIY/Repairing your own gear forum.

I will have to check that out. I don’t think I will be keeping either mk7 regulator sets but we will see.

 

[AfterDark]

I will have to check that out. I don’t think I will be keeping either mk7 regulator sets but we will see.

I'd be interested in those MK7's.

 

[Bearded Diver]

Tha

Greetings All,

To make a long story short, I picked up 2 steel PST tanks way out of hydro (78) along with 2 pairs of jet fins and 2 Scubapro MK7 regulator sets for $100.00. Both tanks just came back to me with a new hydro stamp. Both tanks appear to be the same height and same diameter but one is rated at 2250 and one at 3000. My LDS owner and manager said they have never seen a PST steel 72 rated at 3000 pounds and couldn't believe how heavy it was. Both valves are Shearwood selpac. I am wondering if any of you have more information on the 3000 psi tank and insight into why it is so much heavier than the 2250 tank.

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