HIGH PRESSURE TANK vs LOW PRESSURE TANKS...?

[Superlyte27]

According to the IANTD book, nitrox cleaning is not necessary with oxygen contents below 40%. Except for filling deco bottles, I've never been a shop that looked for one of those fancy Nitrox bands. Of course, I generally only visit techy shops.

I honestly believe that below 40% the Nitrox Bands/Stickers and O2 cleaning is a money grab for shops.

 

[cbrich]

According to the IANTD book, nitrox cleaning is not necessary with oxygen contents below 40%. Except for filling deco bottles, I've never been a shop that looked for one of those fancy Nitrox bands. Of course, I generally only visit techy shops.

I honestly believe that below 40% the Nitrox Bands/Stickers and O2 cleaning is a money grab for shops.

True statements, I could less about the stickers. But O2 cleaning is different deal, you said it yourself

nitrox cleaning is not necessary with oxygen contents below 40%

this is assuming you are fillling off banks, a membrane system, or some kind of system that uses premixed Nitrox. But this does not hold true to partial pressure blending, where in a 40% mix, the blender might drain the tank and fill with pure oxygen to 700+ psig.

You could be correct it could be another way for the shop to make money, but this is to verify the tanks meet the shops requirements of being oxygen clean (that is a different subject all together.) You can not fault a shop to refuse service because they are following what they think is safe practice.

I personally clean all of own tanks, and I have built a relationship wtih my LDS to where they allow my tanks for partial pressure blending. I think a shop that charges $50 - $100 is well worth the money spent, but that is assuming they do a thorough cleaning like I would do.

 

[roadrash]

To all: Im new at this forumand will like to know more. What is the volume on a lp 95 cu tank and why some divers said that they hold more than a 100 hp tank?

 

[kaerius]

I've got a Faber 10L 300bar steel, which I think equates to HP80? 105cu'@4350 PSI according to some online converters.
It's pretty decent for shape, size, weight vs gas ratio. For cold water diving.
In general, due to weight, steel is better in cold water and aluminum in tropical water. Choose accordingly.

I use a DIN reg as well. In order to utilize the higher pressure rating on a HP tank you must have a DIN reg, period. Otherwise you've just got an extra heavy LP tank in practice.

 

[spectrum]

Roadrash,

An LP 95 will hold 95 cubic feet (clever name huh?) of air when it has the + rating on the last hydrostatic test allowing it to be filled to 10% over the service pressure stamped into the cylinder.

The reason some claim higher capacity is that in some regions and yours it the poster child it is common practice to exceed the specification. The common term for such a fill is a "cave fill"

Pete

 

[HIGHwing]

What is the volume on a lp 95 cu tank and why some divers said that they hold more than a 100 hp tank?

An LP95 holds 95 Cubic Feet at it's working pressure. However, you can fit 130 cubic feet of gas into a 95 cubic foot cylinder if you squeeze it hard enough.

 

[Griffo]

Dear God, now we've moved to the myth of O2 cleaning for Nitrox.

How's it a myth? Around here many shops still partial pressure fill, and will refuse to do so without a valid O2 clean sticker. So for me it's not a myth. Either o2 clean the tanks, or only fill at shops with banked nitrox.

On the original topic, you guys have such a confusing number of fill pressures. Here it seems to be standard - Ali tanks go to 200Bar (3000 PSI) and steel goes to 230 Bar (3442 PSI) or 300 Bar (4350 PSO). 230Bar is definately the "standard" fill pressure. But on the flipside we have to hydro every year :-(

 

[HIGHwing]

We make it easier. Everything goes to 3600psi and you get a complimentary hydro with every visit to the fill station. ;-)

 

[Dr. Lecter]

In order to utilize the higher pressure rating on a HP tank you must have a DIN reg, period.

False, at least so far as the common 3442psi/3500psi HP tanks go. Get up to the 4000psi+ HP tanks (I think there's a Faber in that category), and you'd be correct...but A-clamp/yoke connections are fine with 3500psi connections.

From AA's specs page:

Max-Pressure Rating (all)

3500 psi (241 bar) with yoke connection 4350 psi (300 bar) with DIN connection

 

[elmer fudd]

Aside from price, the only reason I can see to go with LP tanks over HP tanks is if you plan on overfilling an LP120.

For nearly every other LP tank there is an HP tank made with nearly the exact same weight and dimensions. The HP tank is just rated to a higher pressure and will hold more air at that higher pressure. So if your local shop won't fill to 3500 you can always use it at lower pressure and you'll have just as much air on your back as you would with a similarly sized LP tank. If you have some old regs with low pressure yokes, just don't get your HP tank filled all the way.

Basically, an HP tank works just as good as a similarly sized LP tank at low pressure. It just has the option to hold more air.