Aluminum to Steel

Hello!

Since I use this board more than any, I'll start with my fellow Wetpixel divers. I am considering buying our own 119cf steel tanks, cleaned and used for Nitrox. In order to keep down the confusion we are, EANx, recreational advanced divers who dive quite regularly in the Virgin Islands. I am not acquiring the tanks to increase bottom time but to save space aboard the small boat, two tanks instead of four. Looking to get two dives out of one tank. I am acquiring a 15' RIB. The tanks are described as being similar in size to an Aluminum 80, the size we commonly rent in the V.I. Other than removing weight from belt what else can I expect? I am 210 lbs. 6'0" but my soon to be wife is only 130 lbs. 5'6". Our routine involves doing our safety check at the dock and then putting on weight integrated BCDs in the water at dive site. There are only two Nitrox fill sites in V.I. One on St. Thomas and the other on Virgin Gorda. One tank each will also mean one evening trip to fill station

Is this a logical approach? Anybody using the 119cf tank? Are any steel tank brands better than others? Other than clean and dry and not letting it get completely empty anything to be careful of?

--Chris

couple of thoughts...

the problem you will come across is that you will be going from two 80's to one 120. Essentially you will lose 40 cubic feet of air. For me, in warm water I can stay under for 70-75 minutes on one 80, so that means I would lose 35 minutes of bottom time. That would be a lot of bottom time lost.

I own a high pressure steel tank. It is an 80 but looks like a 65. It runs pressures up to 3400psi which gives me an equivalent air of an 80. It is great for Monterey cold water diving. A 100 would look just like a 80 and give me a ton of bottom time.

So, if i were to buy my own tanks in the Virgin Isl, I would get two high pressure tanks (probably 100s), give myself more bottom time, and not worry about the extra space. Another thing, if you do get the high pressure tanks, make sure the places will fill to 3400 psi, if not, that would be a moot point.

Lastly, steel tanks will rust, so make sure the places you get fills have dry air.

Hello Chris. I understand some of the objectives you're trying to accomplish. I'm assuming you routinely only use about half your backgas, and are using cheap (floaty) Al80's.

I also assume you're refering to the Worthington X8-119, since the PST's are out of production right now.

Weight: Correct weighting is often quoted as neutral at a safety stop w/ 500 psi. As someone who quite often dives with deco obligation (which this monster cylinder certainly will allow you to unknowingly get into) I can state with certainty that "correct" weighting is neutral, at the surface, with an empty cylinder, and empty BC.

So, assuming that you are correctly weighed, switching to this cylinder from a cheap 80, you'll be removing 6 to 7 pounds from your belt. For me, this means I'd be going from 18 lbs in my 3mm to 12 lbs.

This has consequences during the dive, though: how big is your BC? For example, my Pro QD has 31 lbs of lift. My camera is about 4 lbs negative. The gas load in a full 119 is about 9 pounds, and the cylinder is 2 lbs. So, if I start out the dive with a trip to 90', where my wetsuit is squashed flat, my total negative weight will be 9+4+12+2, or 27 lbs. So, my BC will be 80% inflated just to stay neutral. And, this may exceed the lift of smaller BC's.

If you are diving shorties, and your wife is petite, it is possible that her lead (right now) is less than 6 lbs, and switching to the 119 will place you in negative numbers.

There's other things to consider, as well. Assume, while at depth, my BC bladder fails. Or an exhaust valve fails. Regardless, I now have no floatation. Fine, I ditch my lead, and (sadly) my camera. I still have to swim up 11 lbs! (gas + cylinder) This is harder than it sounds; throw on a 10 lb weightbelt in the pool and try to stay at the surface. I would reccomend this little exercise before switching to these tanks. It's this nasty little problem that has deco divers, using wetsuits, either using AL cylinders or double-bladder wings.

Beyond that, there's the plain issues of wrestling a 12 lbs heavier BC into the RIB after the dive, or if you can get a reliable fill to 3500 psi. The issues of steel rusting, if you take care of them, I haven't seen a big problem.

Personally, I dive with the smallest cylinder(s) that fits the profile. I do a lot of diving with an AL50.

They don't call these "water heaters" for no reason......

All the best, James

just be sure to sell them when they lose their + rating :-) gotta have that 10% overfill!!!

I'd go with the double 100s too... or even 90's, my friend had one that he ran at 3400 or so... does great

I guess the factor that is I was looking to do Nitrox. If I just do air its anything steel since I can get fills just about anywhere before second dive. I was trying to get in two dives, one below 60 ft. and second above 40 feet in one tank.

The PST E series tanks are out of production? There are a number of new ones for sale around here (So. Ca)

They are the best tanks I have ever owned. I have 3 80s and a 100. I was thinking they made a 120. 3442 PSI, very good buoyancy characteristics.

As they are steel you might have to tumble them when you do the yearly VIP. As they are E series tanks you don't have to worry about that annoying 10% overfill or loosing it after the first hydro.

I would be bad if they were no longer making them.

Sad but true. The company went under, and is being bought by investors, to be relocated and re-open.

A potential problem for divers is that the cylinders are used at a high pressure by exemption from the DOT. With the company gone, the exemption expires, unless a citizen petitions DOT to renew it in their name. As someone with a couple sets of PST, I, too am watching this with interest.

Of course there are still cylinders in the retail pipeline, so they can still be be purchased.

The demise of PST

Official PST propaganda

A truer evaluation of the company's chances

Personally, since PST was primarialy a manufacturer of LPG and industrial tanks, with scuba cylinders as a minor product, I'll be surprised to see a return. Especially with the conditions surrounding the bankruptcy and repurchases, all involving the same management team.

The Worthingtons appear to be so similar to the PST cylinders that most wouldn't know the difference, and are in good, reliable supply.

All the best, James