232 vs 300 bar tanks - any practical experiences?

[Tassie_Rohan]

I'm planning on getting several faber 100 cuft tanks. I’m debating between the standard 232 bar and the smaller higher pressure 300 bar tanks. Anyone have practical experience using the higher pressure tanks? The 300 bar tanks are smaller, heavier and would take a lot more weight off my belt and put it on my back (BTW: I don't think these 300 bar 100 ft Fabers are for sale in the US). However they may be a bit too negative for some peoples liking. Any practical experiences and preferences out there?

Aussie -> US Translation:
Australian standard 232 bar are 3360 psi HP ‘high pressure’ tanks
Australian high pressure 300 bar tanks are filled at an unheard-off 4340 psi.

Aussie-> Pom Translation:
100 ft 232 bar: 12 L
100 ft 300 bar: around 9.4 L

(Yep – I use imperial for contained gas, metric for pressure, and converting between imperial and metric tank specifications makes my brain hurt…)

Most of the LDS in my area can do 300 bar fills (probably 290 in reality, 280 allowing for non ideal gas behaviour at that pressure?), and my 1st stages are rated to 300 bar, so should be no issues with fills or wear ‘n tear. Just interested in hearing peoples preferences and any buoyancy/trim issues between the two tank types...

The tanks will be dived as singles for now, but I can see myself converting them to doubles when I get around to doing my cave diver training down the track

Cheers,
Rohan.

 

[JimC]

If your going to be doing caves 9-10L tanks are MUCH to small. Even 12L tanks are smaller than most use. Most cave divers use 16L tanks, then pump THEM to 300bar.

 

[Tassie_Rohan]

If your going to be doing caves 9-10L tanks are MUCH to small. Even 12L tanks are smaller than most use. Most cave divers use 16L tanks, then pump THEM to 300bar.

Thanks for the insight Jim - 16 L's are too large for the rec dives at hand (I can get plenty bent with 100 cf) but it sounds like I'll need a second set of tanks should I get into caves proper....

From other boards I've learnt the strongly (like -14 lb) negative 300 bar tanks can be a pain trim wise, are a lot heavier than the same volume 232 bar tanks and that they suck as doubles. Their smaller size can make them difficult to sit into and they certainly can't be overfilled.

I'll prob go with 100/232 bar (similar as your 100 HP's or 7-100's): they are light (28 lb), can be pumped up a bit if needed, doubled for 200 ft for poking around on deeper wreaks, and by themselevs are a nice size for shore dives and geting back up the ladder. Or maybe only a 85 ft/232 bar... Why is deciding on tanks more of a pain then selecting regs or a drysuit....

Cheers,
Rohan.

 

[CD_in_Chitown]

I've got a set of HP 100s and I love the balance and trim, I have tried LP tanks in various sizes (72, 85, 98, 104) but never found the balance that I have with the HPs. YMMV

 

[aabond]

I just bought a new PST HP 100 and absolutely love it. Only wear 4 lbs compared to the 14 or so lbs i use to wear and trim is amazing. The best part is that extra 25% of air as compared to an al80, which gives me a good reserve of about 1500-2000 psi at the end of my dive.

 

[Blackwood]

^^ Which isn't 300bar...

 

[MrConclusion]

I recently switched from 3000psi AL80's to 3500psi steel 100's. Not exactly your situation, but I do have some observations.

The steel tanks allow me to carry less weight, but 100 cu/ft of air weighs the same no matter what tank it's in. I actually need to start diving about few extra pounds overweight if I want to be neutral in shallow water as the tank nears empty. In normal recreational diving it would matter less if I were somewhat positive above the safety stop, but in confined water it's annoying.

The steel tanks are quite negative, which makes it a little harder to demonstrate skills where removal and re-donning of the BC unit are performed underwater. I can add air to the BC to make it easier, but I try not to since the students should NOT be doing that with their AL80's! Usually, I "fake" the "step 1 complete air dump" part of the demonstration and willfully leave a little air in the bladder.

My trim is quite different. The weight that came off my BC (where it was all above my hips) has now moved way back behind me, and upwards in the form of a heavier tank. With an AL80 I could hover in a "standing" position effortlessly, but with the steel tanks, I need to fin occasionally or else I end up on my back. I've experimented with carrying 4-8 pounds of lead on a belt instead of in my BC, because I can let it ride lower and right in front next to the buckle, and this makes life easier, but looks funny.

But these are just my gripes, and I'm sure that another season of experience will help me deal with them. I actually like the tanks and don't regret buying them.

 

[grazie42]

Ok...the cft and HP100´s just give me a headache so if my answers are superflous because someone else already said the same thing, I apologize...

I have a 8l 300bar tank. For trim and all the other dive-related stuff I like it great (friends have 10l 300bar and like theirs). I also like that it takes up so little room in the trunk of my car. I THINK it holds about as much air as a 80cft-bottle. I use about 2kgs/4lbs less lead when I dive my bottle than when I dive a 12l 232-bar.

300bar tanks are good as singles but become a real PITA when doubled (at least the bigger ones). If you´re thinking of doubling your´s I´d go for the 2x12, 232 bar, that is a sweet doubles set. Personally my 8l 300bar is big enough for a good hours worth of recreational diving. For the tech-stuff I´ve chosen a 2x15, 232 set (because of my buddies airconsumtion).

I only wreckdive right now so take it for what its worth but having talked to the instructor I plan to do fullcave with next year he felt that twin15´s are a good choice for cavediving...

Also just as a side-note...I would make sure you have someone to do the dives with before signing up for the course (preferably with your buddy)...

 

[Tom Winters]

Most of the LDS in my area can do 300 bar fills (probably 290 in reality, 280 allowing for non ideal gas behaviour at that pressure?)

"Most of the LDS in my area"??? I never realized that Mongolia was such a hotbed of diving activity.