300 bar tanks

[Diver0001]

In January my 15 litre tank will need a hydro and I'm considering selling it and replacing it with a twin-7.

The twin-7 solves a few little problems that I have with the 15 and the format is firmly decided. I already have a larger twin-set and the double-7 is the largest format the instructors I work for will accept for assisting in OW.

Here is my conundrum: I can buy these sets in 232 (3400psi) and 300 bar (4500psi) variants. There are weight differences and I know about gas laws, trim, stability and blah blah blah. That's not my problem.

My problem is that part of me wants to buy the high pressure tanks to get the longer bottom times and part of me is worried about the strain on my 1st stages.

Which part of me should I listen to?

R..

 

[TX101]

In January my 15 litre tank will need a hydro and I'm considering selling it and replacing it with a twin-7.

The twin-7 solves a few little problems that I have with the 15 and the format is firmly decided. I already have a larger twin-set and the double-7 is the largest format the instructors I work for will accept for assisting in OW.

Here is my conundrum: I can buy these sets in 232 (3400psi) and 300 bar (4500psi) variants. There are weight differences and I know about gas laws, trim, stability and blah blah blah. That's not my problem.

My problem is that part of me wants to buy the high pressure tanks to get the longer bottom times and part of me is worried about the strain on my 1st stages.

Which part of me should I listen to?

R..

I don't "believe in" 300 bar cylinders, for the reasons that you say are "not my problem".

Roughly speaking, a 300bar 7L is the same weight and contains the same gas as a 232bar 10L. So why not just get the 10? You wont have problems with short fills (270 when you hit the water) or problems with getting the correct nitrox mix.

If you want longer bottom times, take your bigger twinset...

Why would you want longer bottom times on an OW course anyway? with 14L, you should outlast every student easily.

 

[Diver0001]

I don't "believe in" 300 bar cylinders, for the reasons that you say are "not my problem".

Well....what I should have said is that it's not a problem that I need to discuss, which isn't to say that it isn't an issue I need to consider. Same goes for short fills and hot fills. I was curious about people's experience with the extra strain on the 1st stages because that's the part where I have a white-spot.

If you want longer bottom times, take your bigger twinset...

Why would you want longer bottom times on an OW course anyway? with 14L, you should outlast every student easily.

The comment about longer bottom times wasn't related to OW. I was thinking more in terms of my own dives.

My other set is a twin-12. I'm unable to rent a second twin-12 for N. Sea diving and I can't fill on the boat I've been using so in the back of my mind I was thinking about a generic solution that would work for OW (ie small enough, a twin-10 simply isn't acceptable for the shop) and would work for the 2nd N. Sea dive of the day.

So that's the backdrop I'm looking at.

R..

 

[grazie42]

Aren´t your first stages 300bar DIN´s ?(I assume they are)
That means that they were built/designed for that pressure. Of course 300BARs propably means more "wear & tear" then 200 but my experience with diving 300´s for some 300 dives has meant no more maintenance than my buddies 200 setup...
What I´m trying to say is that there´s propably a theoretical difference but not a practical one...

 

[Leadking]

Aren´t your first stages 300bar DIN´s ?(I assume they are)
That means that they were built/designed for that pressure. Of course 300BARs propably means more "wear & tear" then 200 but my experience with diving 300´s for some 300 dives has meant no more maintenance than my buddies 200 setup...
What I´m trying to say is that there´s propably a theoretical difference but not a practical one...

There is a lot of talk about 300 bar tanks in the U.S.

What is the largest diameter of 300 bar cylinders and who makes them?

 

[NauticalbutNice]

I have dived both 12L 232's and 300's.

300 bar cylinders have DIN fittings, and as far as I can see have about the same life as an A-clamp on a 232.

Nauticalbutnice :fruit:

 

[Diver0001]

There is a lot of talk about 300 bar tanks in the U.S.

What is the largest diameter of 300 bar cylinders and who makes them?

7's and 10's are fairly common. The biggest ones I know of are 12's.

They're pretty negative. You could make a twinset out of 7's but you'd need to strap the Hindenburg to your butt if you twinned up the bigger ones.

The manufacturer is Faber. You can probably find more information on their website

R..

 

[Lightning Fish]

Rob:

When diving with the OW class, is there a need to fill the 300 Bar 7s right up? Keep the fill pressure lower so your first stage isn't exposed to a high pressure all the time. When diving in the North Sea, then fill them up to the max. How damaging is it to expose your regs to a high pressure every once in a while?

Bill.

 

[Diver0001]

That's a good idea, I hadn't thought about that. Thanks, Bill

You always were the smart one...

R..

 

[KOMPRESSOR]

Hello? Your 1st stage is made for 300 bar. What's the problem? Up here where I'm at you will find 70% of the diving schools uses 10L/300 bar on their students, simply because they are better than the "other choice". the 15L/200 bar. (All steel. Never seen alus in use here at all)

Take into consideration we use drysuits in most of our diving. -Very often neoprene drysuits with lots of bouancy.

I went for a slightly different solution as I chose to use long 12L/300 bar tanks in single tank config only (On a Eclipse 40). Since I am 6'2" / 187cm this long and heavy tank gives ME a decent trim. And trim is an issue when choosing tanks.

With 300 bar tanks, short tanks tend to drop you on your nose. A snug 2x6L/300 bar would certainly to you good for trim, and gives you plenty of air. If you want more, I would think you could consider a 2x12L/232 bar for a doubleset that gives you PLENTY of air/gas, and also gives you a great trim for most purposes.