Lightweight steel tank?

[fisherdvm]

As I am loading more lead with cool water diving, and I have had back problem off and on in my life.... What is the best type of tank to use. I currently have regulators that have yoke 1st stages.

As I understand, the HP tank are the smallest and lightest, right? How many pounds do I expect to save because of tank weight.

And steel tank are supposed to have better bouayncy characteristics, right, allowing me to shed a few more pounds of lead.

Last questions, don't HP tanks usually have DIN valves? And do you need a DIN to yoke adapter? If this is the case, how high can you pressurize your tank for my yoke based regulators?

 

[zvinzonz]

I guess it depends on what size tank you'll be using. If you're going to use HP 80 it's a little bit lighter than the alum 80 plus i was able to take off around 8 lbs off wieght. Also it depends on the manufacturer. If im not mistaken Faber got 2 types of HP 80 and one of the tank are heavier than the HP 80 made by Worthington and PST, atleast that's what i was told by one of the LDS.

As far as using yoke you can use it with the HP tank as long as it's rated 3442 PSI. The HP tank that's rated 3500 PSI use a din valve. The 3442 use i believe pro valve which you can use for both yoke and din 1st stage. There's an insert that you can take off if you're using din.

Vince

 

[loosebits]

Here are some tank specifications, pretty much every tank you can buy is listed here: http://www.techdivinglimited.com/pub/tanks.html

 

[zvinzonz]

You beat me to it. I was looking for that link on my old email so i can post it.

 

[spectrum]

Going from from an AL-80 to a HP steel 80 you can drop about 12 pounds from the combned differences in weight and buoyancy. See here.

Most HP cylinders sold today are not truly HP which is defined as having a working pressure of 3500 PSI or more. The common 3442 PSI cylinders have convertible valves that wil accept DIN or yoke regulators. DIN is prefered but many many divers are safely diving in the yoke configuration. Search for other recent threads for more.

Pete

 

[skynscuba]

As I am loading more lead with cool water diving, and I have had back problem off and on in my life.... What is the best type of tank to use. I currently have regulators that have yoke 1st stages.

Compared to an AL-80, the 3442psi 80's will give you a total weight (walking down the beach, climbing out) of about 10# less. The LP steel tanks (77, 80) would give you somewhere in between the AL80 and the HP80 as far as lead required and total weight. If you are tall, the longer LP cylinders, or HP100s, might suit you better.

Where are you wearing your lead? I started with a non-weight-integrated BC, AL80 tank, very thick drysuit undies, etc. The distributed flotation (tank, suit, body) was all being countered by a very heavy weight belt, pulling down right where my back hurts. Distributing the weight helped a lot. I'm really looking forward to trying the HP80's I just bought, and dropping about 7 pounds of lead.

My girlfriend's Worthington 3442-80 cylinders are about 2# heavier than advertised -- almost as heavy as the AL-80. However, they are about 2# more negative than advertised, so it works out okay -- 2# less lead, and the same total weight walking in/out. My PST E80s are closer to spec. I weighed them all, in and out of my pool, and compensated for salt water, how full the tanks were (pressure, temperature), etc.

 

[1_T_Submariner]

Something to Keep in mind when looking at these tanks is where you get them filled and what pressure you end up with.
Example:
HP120 = 120Cu/ft @ 3442PSI
HP80 = 80Cu/ft @ 3442PSI
So I get a fill to 3000PSI
HP120 = 105Cu/ft @ 3000PSI
HP80 = 70cu/ft @ 3000PSI

I rounded a little and assumed the tanks where corrected for temp.

To make a long story even longer. If you get the HP 80 and get a 3000 PSI fill you will run low on air before your buddy with the AL80 that got the 3000 PSI fill.
This isn't a problem if you get fills to the rating of the tank.

 

[Divin'Papaw]

Something to Keep in mind when looking at these tanks is where you get them filled and what pressure you end up with.
Example:
HP120 = 120Cu/ft @ 3442PSI
HP80 = 80Cu/ft @ 3442PSI
So I get a fill to 3000PSI
HP120 = 105Cu/ft @ 3000PSI
HP80 = 70cu/ft @ 3000PSI

I rounded a little and assumed the tanks where corrected for temp.

To make a long story even longer. If you get the HP 80 and get a 3000 PSI fill you will run low on air before your buddy with the AL80 that got the 3000 PSI fill.
This isn't a problem if you get fills to the rating of the tank.

You're raising a very good point. I went with the HP100s for this exact reason. If I can only get a 3000 PSI fill, I still have 87 cf of gas ... 10 more than an AL80. And I have the benefit of much better buoyancy characteristics. I have been able to drop 7 lbs of lead just by going from an AL80 to the HP100.

I've found it difficult to get a good HP fill here in Indianapolis. The one tech oriented shop I go to can get them there, but the closest shop to me can only get them to the 3100-3200 range. Given the type of diving I typically do locally, this isn't a problem. But it is something to be aware of and plan for.

 

[loosebits]

Wouldn't it be great if we did it like the Europeans and just talked about liquid volume (e.g. a 12 L tank or a 15 L tank).. sure does make it easier to compare absolute sizes. And if we switched to bar's instead of PSI, figuring out how many liters of gas is in the tank is trivial.. a 12 L tank filled to 200 bar holds 2400 L. Better yet, if we switched our depth gauges from Feet sea-water (which is really a measurement of pressure, not depth) to bar absolute (2 bar is 33 fsw, 3 bar is 66 fsw) then all the calcs become trivial: If I have a 12 L tank at 200 bar, how long can I stay at 4 bar given a SAC of 20 L/min? 12L * 200 bar / (4 bar * 20 L/min) = 30 mins. Wow, that's so easy I could actually do it while diving. Compare that to the formula for an AL 80 filled to 2000 psi diving to 99' with a SAC of .5 scfm.

Ok, rant over.

 

[SparticleBrane]

My girlfriend's Worthington 3442-80 cylinders are about 2# heavier than advertised -- almost as heavy as the AL-80. However, they are about 2# more negative than advertised, so it works out okay -- 2# less lead, and the same total weight walking in/out. My PST E80s are closer to spec. I weighed them all, in and out of my pool, and compensated for salt water, how full the tanks were (pressure, temperature), etc.

Are the weights advertised with or without the valve? That makes a difference.