300 bar tanks

What do you use? Got a question about buying and maintaining your tank /valve? Then post in here.

300 bar tanks

Postby 3RNZIR » Fri Jul 25, 2008 8:10 pm

Any in NZ?
Peace:Via superior firepower.
3RNZIR
Member
 
Posts: 17
Joined: Tue Oct 23, 2007 9:46 am

Re: 300 bar tanks

Postby Andy » Fri Jul 25, 2008 8:21 pm

Some. But you won't find many selling in the dive shops.
Andy
Serial Poster
 
Posts: 4628
Joined: Thu Feb 01, 2007 1:29 pm
Location: Auckland

Re: 300 bar tanks

Postby 3RNZIR » Fri Jul 25, 2008 8:26 pm

Import the tanks and use your own compessor I gather would be the go?
Peace:Via superior firepower.
3RNZIR
Member
 
Posts: 17
Joined: Tue Oct 23, 2007 9:46 am

Re: 300 bar tanks

Postby Andy » Fri Jul 25, 2008 8:29 pm

Depends on what tanks you're actually after. Check the list of LAB and SP numbers on the ERMA website and work out whether you can get a tank that has an existing LAB number - then there's no risk of bringing in the tank and being somewhere that you can't get a fill.

Do a search on here and you'll find links to the downloads for the LAB and SP numbers.
Andy
Serial Poster
 
Posts: 4628
Joined: Thu Feb 01, 2007 1:29 pm
Location: Auckland

Re: 300 bar tanks

Postby 3RNZIR » Fri Jul 25, 2008 8:32 pm

Thankyou Andy
Peace:Via superior firepower.
3RNZIR
Member
 
Posts: 17
Joined: Tue Oct 23, 2007 9:46 am

Re: 300 bar tanks

Postby Tristan J » Mon Jul 28, 2008 4:37 am

Hey 3rnzir,

I went down this path a few years ago, and my advice is to go with something simple like 232bar Fabers.

I was looking at twin 7 300bar but went with 232bar Faber 10s instead

Few reasons for this;

I was unable to find 300 bar tanks from any importers, and so bringing in my own meant dealing with LAB numbering and extra costs
(not to mention effort, a bit negative for me)

While a set of steel 300 bar 7s are a nice little package, they weigh more than a set of steel 232 bar 10s.
And they both contain the same amount of gas.
( 2*7*300 = 4200 liters or 2*10*210 = 4200 liters), however perhaps you like the weight? or maybe your looking at composite? (I know a fireman from the UK who uses these, and he doesn't use an excessive weight belt? has me perplexed!)

Next is most dive shops fill with yoke fittings and hence only to the lower pressures. I have a portable 330bar Bauer at home, but it is not very travel friendly even with a LWB truck. (2*7*210 = 2940 liters)

And finally I guess is the old "Van der Waals", high pressures and mixed gas don't work so well!

Probably not the answer you were looking for, but maybe this helps?

Cheers,
Tristan
User avatar
Tristan J
Member
 
Posts: 15
Joined: Sat May 10, 2008 7:18 am

Re: 300 bar tanks

Postby Andreas » Mon Jul 28, 2008 3:51 pm

Not that I mean to pick on your maths, but you actually get more gas in the 10x232 than a 7x300.
In reality you only get around 270 bars in the 300 after the tanks have cooled down, and even then the Van der Waals force means that you have less air in there than in the ideal state.
Andreas
Member
 
Posts: 13
Joined: Tue Jul 01, 2008 2:46 pm
Location: Hamilton, Waikato

Re: 300 bar tanks

Postby Andy » Mon Jul 28, 2008 5:31 pm

I'm not too sure where Tris is getting his fills..... but I'd not be that happy with a 210bar fill in a 232bar tank! If we play by OSH rules, then I'd hope for 227bar.

227 * 10 * 2 = 4540 liters
Andy
Serial Poster
 
Posts: 4628
Joined: Thu Feb 01, 2007 1:29 pm
Location: Auckland

Re: 300 bar tanks

Postby Tristan J » Mon Jul 28, 2008 9:56 pm

Andreas wrote:Not that I mean to pick on your maths, but you actually get more gas in the 10x232 than a 7x300.
In reality you only get around 270 bars in the 300 after the tanks have cooled down, and even then the Van der Waals force means that you have less air in there than in the ideal state.


Well I think the maths is fine? I use 210 bar in the example as to prove that even a low fill will produce more than a full fill in the 7lt 300s.

I believe our concern with the Van der Walls is more relative to specific gas compressibility, and the interactions that cause nonlinear fractions in gas percentages as we leave the ideal linear pressure reagons?, ie above 250ish bar. Hence the problems with Mixed gas fills.
I also think that you are right, that you will also have less gas than in the ideal state but I think this is a minimal amount, as you say temperature is the real culprit.
But i'm also sure that someone on here will know more about this than me and might explain!


Andy wrote:I'm not too sure where Tris is getting his fills..... but I'd not be that happy with a 210bar fill in a 232bar tank! If we play by OSH rules, then I'd hope for 227bar.

227 * 10 * 2 = 4540 liters


Well as above, for the example and point I was trying to make, even a low fill has more gas

None the less we all make the same point here, the low pressure tanks are easier to get more gas, for a slight increase in volume?

Cheers,
Tristan
:)
User avatar
Tristan J
Member
 
Posts: 15
Joined: Sat May 10, 2008 7:18 am

Re: 300 bar tanks

Postby Andy » Mon Jul 28, 2008 10:26 pm

Tristan J wrote:None the less we all make the same point here, the low pressure tanks are easier to get more gas, for a slight increase in volume?


Yeah... I'd consider (in an ideal world) 300bar 12s, but they are damn heavy. Realistically there's not much difference than 232bar 12s with a cave fill.

Not that anyone in NZ would do a cave fill, mind you.
Andy
Serial Poster
 
Posts: 4628
Joined: Thu Feb 01, 2007 1:29 pm
Location: Auckland

Re: 300 bar tanks

Postby 3RNZIR » Tue Jul 29, 2008 2:05 pm

What about filling 232bar Fabers to say 250bar from time to time?Would be within the engineering spec pressure wise surely.Andy,what is a cave fill?
cheerz
Peace:Via superior firepower.
3RNZIR
Member
 
Posts: 17
Joined: Tue Oct 23, 2007 9:46 am

Re: 300 bar tanks

Postby Andy » Tue Jul 29, 2008 2:24 pm

3RNZIR wrote:What about filling 232bar Fabers to say 250bar from time to time?Would be within the engineering spec pressure wise surely.Andy,what is a cave fill?


There are laws that control how much you can fill a tank based on the temperature of the day it's filled. Basically, the "developed pressure" cannot (by law) exceed 227 bar at 15 degC.

Even though the developed pressure tables are included in the tank fillers course (required by law) they're rarely used. Most shops will fill to 230 or so and let it cool to 200-210 bar. A couple of places will then top up the tank once it's cooled so you do get 227bar.

A "cave fill" is exactly what you're suggesting - pumping up a tank to beyond it's working pressure. It's common practice in some parts of the US - but the divers sell on the tanks before the hudro's are due. I doubt you'd find anywhere in NZ that does this. It does reduce the lifespan of a tank significantly.
Andy
Serial Poster
 
Posts: 4628
Joined: Thu Feb 01, 2007 1:29 pm
Location: Auckland

Re: 300 bar tanks

Postby Tristan J » Wed Jul 30, 2008 12:52 am

3RNZIR wrote:What about filling 232bar Fabers to say 250bar from time to time?Would be within the engineering spec pressure wise surely.Andy,what is a cave fill?


The law of 227bar is targeted at flat face o'rings (yoke) and provided that you don't exceed the working pressure of any of the components (Tank, valve, whip etc,).
However I think that you can reach the 232 bar ''legally" provided you don't exceed any components WP, So in NZ this must be done with captured O rings (DIN), not nesessarly 300bar, not 100% sure on this though!

Cave fills, as I understand it relate to the use of the older LP steel tanks. These had working pressures around 2640 psi (approximately 180bar). Now the American classification of tanks relates to the amount of gas it will hold at its WP in cubic feet...
So if you had a LP 104cf we would call it a 16 liter, or there abouts
however a HP (3500 psi or 230bar, approximately) 100cf tank is closer to a 12 liter,
Now the cave fill edict was to fill the LP tanks like it was a HP tank, then you had the preferable buoyancy and weight characteristics and alot more gas.
Over filling the HP tanks was not so common.... thats another story
The reason the risks of overfilling a LP tank was deemed ok, is due to the fact that tanks are engineered to have a life expectancy of something like 1000 cycles to test pressure, when new!
This is why they were sold before the Hydro as Andy points out!

[quote="Andy"]
Yeah... I'd consider (in an ideal world) 300bar 12s, but they are damn heavy.
quote]

Ideal world? why not the twin megs :D

Cheers,
User avatar
Tristan J
Member
 
Posts: 15
Joined: Sat May 10, 2008 7:18 am

Re: 300 bar tanks

Postby Andy » Wed Jul 30, 2008 10:48 am

Tristan J wrote:The law of 227bar is targeted at flat face o'rings (yoke) and provided that you don't exceed the working pressure of any of the components (Tank, valve, whip etc,).
However I think that you can reach the 232 bar ''legally" provided you don't exceed any components WP, So in NZ this must be done with captured O rings (DIN), not nesessarly 300bar, not 100% sure on this though!


You're spot on, Tris. Though in typical OSH/ERMA style there are exceptions... so to reach 227bar for a yoke valve, the valve actually needs to be stamped or marked with it's WP. Any unmarked valve, irrespective of the WP of the tank, can only be filled to 207bar!!

You've gotta love the bueracracy at times.

I've just dug out the 2004 HSNO act, which states;

"This filling pressure is the maximum permitted pressure in the cylinder when the cylinder, gas and ambient temperatures are all at 15 degC. Such an event will rarely occur in practice and the pressure should be adjusted to compensate."

There's also a procedure for filling tanks that allows you to fill to what you believe (by experience) the correct amount will be so that the developed pressure will settle to the allowable amount after the tank is left standing for 24 hours.

There's a look up table, if I had a tank that's WP was 22.8MPa - if it was a cold day (5 degC) the maximum developed pressure would be 21.6MPa, but if it was a hot day (30 degC) it could be as much as 24.6bar.

The logic behind this is that if you fill a tank on a cold day, when it heats up it doesn't cause a problem.


Interesting stuff, eh?!


Ideal world? why not the twin megs :D


Not convinced by the meg, yet. Nor the inspo, so I'm still sitting on the fence not quite managing to commit to a given unit.

Might wait til we move to Canada - more chances to go and have a play with various units.
Andy
Serial Poster
 
Posts: 4628
Joined: Thu Feb 01, 2007 1:29 pm
Location: Auckland

Re: 300 bar tanks

Postby Jason » Thu Nov 13, 2008 1:54 pm

I'm thinking about buying x2 18Litre tanks (not as a twin but because of majority being double-dive). My dive buddy uses two and the only real problem is if you have a Loooooooooooonnnnnnnnnnnnnnnnng walk to the Shore Dive entry (or from exit) - then they can take their toll on your shoulders.

I've heard of Titanium Tanks that can be filled to 700 Bar (for say a 12 Litre) but only a few specialist systems cater to this. The only one I have heard of is in Russia. Also the fact that these tanks can become VERY bouyant and you need to weight yourself down considerably.
Has anyone heard differently or more so :?:
Just drifting along with whatever is current.
Currently I'm reading : The Art of Innovation by Tom Kelley.
User avatar
Jason
Member
 
Posts: 1184
Joined: Sat Nov 01, 2008 10:41 pm
Location: Outside of Sydney, NSW - Australia. Oceania.

Next

Return to Tanks

Who is online

Users browsing this forum: No registered users and 2 guests

cron