What are the true advantages of steel tanks?

[yknot]

One big advantage of steel, especially LP tanks is the increase in gas volume you can acheive IF you can get the overfilled. Say you are diving a yoke reg and want to push the tank pressure to 3400 PSI. With a 80 LP steel, being full at 2640PSI, this is an increase of 28% or about 23 cf for a total yeild of about 103 cf. Push an aluminum 80 from its normal fill of 3000 PSI to the same 3400 and you are only gaining about 13% or 11 cf for a total of 91cf. You would have to fill a HP steel to about 4500PSI to see the same amount of gas as an overfilled LP80 and I would think 4500 PSI is harder to come by than 3500 PSI.

 

[Warren_L]

One big advantage of steel, especially LP tanks is the increase in gas volume you can acheive IF you can get the overfilled. Say you are diving a yoke reg and want to push the tank pressure to 3400 PSI. With a 80 LP steel, being full at 2640PSI, this is an increase of 28% or about 23 cf for a total yeild of about 103 cf. Push an aluminum 80 from its normal fill of 3000 PSI to the same 3400 and you are only gaining about 13% or 11 cf for a total of 91cf. You would have to fill a HP steel to about 4500PSI to see the same amount of gas as an overfilled LP80 and I would think 4500 PSI is harder to come by than 3500 PSI.

Why not go with a HP steel 100? The internal water volume should be pretty similar and it has the higher service pressure so you don't need to overfill.

 

[yknot]

My whole point with overfills was only that you could significantly increase your gas volume using a LP steel tank vs aluminium and that while you could overcharge HP tanks for the same result, that very high pressure (4500) may not be available. Also, for me, my regs are yoke. I know that there are DIN to yoke conversions available but I've found that in my area yoke anything-rental/loaner tanks and regs are far more prevelant than DIN. Also I have heard, but can't say is fact, that the high pressure seat in some 1st stages will need shorter service intervals when used on HP vs LP pressures.

 

[Warren_L]

One big advantage of steel, especially LP tanks is the increase in gas volume

I was just pointing out that I don't think there is much of an advantage in going to a LP steel tank over an HP tank as you can achieve the same thing with an HP tank by short filling it if you want to use a lower pressure.

 

[netmage]

I was just pointing out that I don't think there is much of an advantage in going to a LP steel tank over an HP tank as you can achieve the same thing with an HP tank by short filling it if you want to use a lower pressure.

I suppose this is why PST just went ahead ond did away w/ the HP/LP differentiations....

 

[BIGSAGE136]

E8-130 Rocks!

 

[Jeddah Aquanaut]

One question for all you tank experts. Does the thickness of an average LP steel tank vary greatly from one (ie Poseidon) of HP? If not, as long as one uses a DIN fitting, is it dangerous to use that same tank at 3500 or more, when with the yoke fitting, it was being used at 3000? Also, how much air does a HP 8 liter tank at 4500 have compared with a LP 80 cubic foot tank at 3000 only? Thanks...

 

[debdiver]

Hey. You guys must be tall or some thing. Has anyone mentioned HEIGHT? It's much easier for a shorter person to dive a shorter tank. When I'm diving an AL80, especially from shore, it's awkward. The HP sits higher on my back, and is more comfortable to walk with.

I've owned ONLY HP steels. I've had two that I have had on boats only, and I've had problems with those. Talking to other divers, and the boat operator, their compressor needed a new filter, or some thing. We were getting moisture in our tanks. I've had to tumble them and hydro them a few times in the past few years. However, the other tank I've got, that has only seen the clean dive shop compressor, is just fine.

As for DIN, well, I guess I made that decision a long time ago, and I haven't looked back. All my regs are DIN and I keep a yoke adaptor handy for travel and/or boat dives where I'm not taking my HP steels. (Which seems to be more and more often these days...)

 

[pescador775]

Your 8 liter tank holds 86 cf as opposed to the S80, an 11 liter tank which holds 77.4 cf. Yes, most HP tanks weigh about 5-10 pounds more than a comparable LP tank. This weight variation is in wall thickness. An exception is the PST HP tank (3500) which weighs about the same as a comparable LP tank. Special steel is used. Everything else being equal, a small 8 liter tank will have somewhat thinner walls than a VHP tank of larger capacity. I cannot answer your question about safety because you say 'used' as opposed to 'rated'. Generally it is safe to fill a Faber LP tank to 3000 psi. The tank should be new or near new with appropriate inspections. Some divers fill these to higher pressures but I do not recommend it. A yoke system of modern design and in good condition is safe to 4000 psi. However, abuse of this type of valve seems to be fairly common, especially among rentals.

One question for all you tank experts. Does the thickness of an average LP steel tank vary greatly from one (ie Poseidon) of HP? If not, as long as one uses a DIN fitting, is it dangerous to use that same tank at 3500 or more, when with the yoke fitting, it was being used at 3000? Also, how much air does a HP 8 liter tank at 4500 have compared with a LP 80 cubic foot tank at 3000 only? Thanks...