Maximum Bottle Size Rating of Bella BCD

[Don Quixote]

Hi,

I just purchased a Bella BCD, size XS. Notice now that there is chart showing that the maximum bottle size for the XS is 10L. But, will need to be diving this with 12L tanks as those ares the most common in most places. Understand also that 10L tanks are actually heavier with pressure up to 300bar compared to the 200bar for 12L tanks. Is there a concern if the XS size Bella is used with 12L tanks? Please advise. Thank you.

- Don

 

[tbone1004]

Don take no offense to this, but I will still never understand why people post these questions in the manufacturers subforums. That is like emailing a car manufacturer saying "my truck is rated to tow 9000lbs, can I tow 10000lbs safely with it?". They legally can't respond to this thread.... Seriously. You are doing something that violates the manufacturers recommendations and are asking them for their advice on whether it is safe to violate the recommendations. Someone else posted this morning in Atomic asking about shortening a regulator hose, they can't respond to that either. Scubapro is also really not an active participant in this forum anyway, so even if it was a legit question they could answer you're better off posting in the general BC section.

To answer your question, which will probably get me a PM saying don't do that. You have 10kg/22lbs of lift in that bc. 5kg of that goes away because you need to keep your head at the surface. I am not 100% up to speed on metric tanks, but I think the 12l's are our Aluminum 80's. Typically about 1kg negative when full with regulator, plus about 2kg needed to balance out the positive buoyancy when empty. So you're at 8kg for the tank and requisite lead to sink it, plus your head at the surface. Hopefully you need less than 2kg of lead to sink otherwise you're not going to be able to stay at the surface comfortably.

Technically you can dive a 22lb wing with an al80 *many of us dive 20-25lb wings for travel wings*, but you can't have any more than 6kg of lead on the rig, to compensate for the tank and exposure protection. With a jacket bc it will be rather uncomfortable when it is filled that full....

 

[Don Quixote]

Hi tbone1004, thanks for the education on both legal matters and how the BCDs are rated. Understand now that the rating is more about lift capability vs the tank. We have mainly 12L steel tanks here, most of them. Thanks.

- Don

 

[tbone1004]

ok, so that's like a HP100 I think if it's a 230bar tank or whatever pressure rating it gets, similar internal volume. They're about 4kg negative, so you're getting close to the carrying capacity on it. It'll float it but not give you a bunch of wiggle room.

 

[Don Quixote]

The 10L tank is -7.8Kg while the 12L tank is -4Kg. This is why I am confused by the rating.

The Bella is designed with the inner vest restrained to the torso through the cummerbund and the shoulder straps. The air bladder is independent and is attached over the vest by loops. So, the bladder inflates outward and does not squeeze even when fully inflated. We dive mainly warm water with lots of rolling waves, 3ft and over. So, the Mares Kaila and the Scubapro Bella are what the wife feels comfortable with on the surface, cannot argue with that or no diving.

Thank you so much for the shedding light on this.

 

[BoltSnap]

The size of the tank isn't as critical as the weight and buoyancy (full/empty) of the tank in this particular case. If she is using an AL80, she should be very OK with this BC. Even small children's BC's are made to be used with the standard AL80 tanks. Steel tanks are a different matter.


Note: Most scuba equipment mfg. are now very busy with getting ready for the DEMA show and with rolling out new products and new catalogs for 2015 so their responses on online forums will be very slow.

 

[tbone1004]

sorry for not having all of the proper buoyancy specs for the tank, but the liter size isn't enough. I've only seen a very select few tanks that have that much negative buoyancy and they are extraordinarily rare in the US. The closest to that is a 16L Faber with a 220bar service pressure, so it's not likely that tank.

This is to correct my first post.
Last I checked, and I could be wrong, 10L tanks corresponded very closely to our AL80's, which are about 2kg positive when full, so you have about 3kg of total ballast for that tank when full with the lead to compensate for it being floaty, that would make sense for the 10kg of lift that BC provides. That is 10L, 200bar service pressure, made out of aluminum.

The 12L tank at 3500psi correlates to our HP100's, or E7-100's which are about 0.5kg negative when empty, and about 4kg negative when full. So that would be seriously pushing the limits of that bc, but it MIGHT float it. She likely won't be able to get much more than her chin out of the water when it is full at the surface and she can't be over-weighted at all otherwise it won't hold her up at the surface. It's cutting it a bit close and I would highly recommend she carry at least an SMB with an OPV on it or a small lift bag. They make small 22lb lift bags designed for divers to basically hang from at safety stops and that would be a good idea for her as a source of redundant buoyancy if you are regularly pushing the limits of that BCD design.

 

[Don Quixote]

Just in case someone is wondering how this worked out. We took the new gears diving in Hengchun Peninsula a couple of weeks ago. We're weighted on the dot at eye-level with empty tanks. With tank full, the Bella is capable to lifting the head out of the water to near shoulder height with a 12L stainless steel tank and BCD not even fully inflated. The 12L tank is rated at a sink weight of 3kg full and the human head is around 5kg. The BCD has a lift of 10.2Kg. So, the numbers seem to add up. Conclusion is that the XS size will work with 12L stainless steel tanks very well with margins to spare.

 

[tbone1004]

just quick clarification, the tanks are not stainless steel, if they were you'd have all sorts of issues because SS is much less malleable than normal steel so you would see stress fractures when they were pressurized.

Glad the rig worked out for you though.

 

[Don Quixote]

I stand corrected about the scuba tanks. Checked and was told that practically all the tanks are aluminum. Was told that steel tanks are no longer used due to difficulty in maintenance. So, all the tanks rented out in Asia-Pacific are mostly aluminum. Was told that tanks with flat bottoms are aluminum. Steel tanks will have round bottoms with stands. The marking also shows 13AL100 which indicates aluminum.