Review Diving the Avelo System

[Wibble]

Avelo has the following sketch of the hydro tank (as shown, below). The bladder is in between the OD of aluminum breathable cylinder and the ID of carbon composite hydro tank. As you pump water into that annulus space you displace the volume of the bladder, squeezing the bladder into smaller volume, hence, increasing the air pressure in the bladder. And from what I understood the hydro tank maximum pressure is ambient pressure, hence, equals to the water pressure at whatever depth you are in. If you are at 30m, the hydro tank pressure would be about 4 bar, which is much smaller than the 300 bar for the breathable air from the aluminum tank inside the hydro tank.

The air bladder is just there to keep the water from sloshing around the cylinder and shifting the system weight around.

View attachment 826924

From that image, any additional buoyancy forces will be applied to the bottom of the cylinder, not uniformly around the centre of the diver's back.

Hence it'll tip the diver forwards, requiring flippers to counteract that weight distribution change.

Is there an optional extra to have a rail track on the cylinder to move a lead weight up and down when it changes the gas volume?


One other small question... How would you hydro test and inspect the inner aluminium cylinder? Does the outer cylinder split like an Easter egg shell? Is the inner aluminium cylinder permanently wet as the inner air space will never dry?

 

[Dan]

Or use any Buoyancy Control Device for neutral buoyancy.

Maybe someone could develop a BCD that doesn’t need batteries, electronics and a water pump to vary the gas volume within a bladder.

In engineering, simple always prevails over complexity.

And that’s what we have in the current BCD design.No battery, electronics and water pump is required. We use Scuba tank air pressure and purge valve to vary the gas volume in the bladder.

 

[lowwall]

Avelo has the following sketch of the hydro tank (as shown, below). The bladder is in between the OD of aluminum breathable cylinder and the ID of carbon composite hydro tank.

Nope. The outer cylinder is a carbon wrapped AL shell. The gas is held in a bladder inside the cylinder. It is attached at the valve at the top of the cylinder. Adding ballast is done by pumping water into the cylinder (but outside the bladder) which compresses the bladder. The bladder is filled to an initial pressure below the cylinder's rated capacity so you can safely add up to 4 liters of ballast water at the beginning of the dive.

Dumping ballast does not require the pump. You manually open a purge valve which allows the gas pressure to expand the bladder and thus expel the (ambient pressure) ballast water.

Avelo has a little animation of this here: Avelo - Technology

I took a screenshot of it during the animation of the purge (blue is the ballast water).

 

[clownfishsydney]

So this system has a battery, pump, bladder and needs a different computer to calculate the actual available air you have to solve what actual problem? Seems like creating many more likely possible failure points!

 

[John Bantin]

Looks like an expensive solution to a problem few proficient divers have.

 

[Wibble]

4 litres == 4kg/9lbs buoyancy.

Sure, that should cope with the 2kg/5lbs of gas weight consumption during the dive, but you’re not going to float on the surface or give buoyancy to anyone else.

Any other BCD will have more like 15kg/35lbs as a minimum.

 

[scubadada]

So if the ballast water compresses the air bladder (thus decreasing its volume and increasing its pressure), how do you know how much air you have left without completely purging the system and making yourself positively buoyant in the process?

The Avelo mode on the computer gives you the % of gas remaining. Otherwise you calculate % remaining from the boosted pressure, Avelo provides a slate if you do not want to do the math.

How is that calculated?

Is that precise or an estimation?

I assume it is calculated from the pressure. You could email Avelo and get a better answer

Avelo - Contact

diveavelo.com

There were some misconceptions regarding how the Avelo System works, seems they have been corrected in the post by @lowwall, above.

It is my impression that the ballast water distributes along the length of the bladder, not just at the bottom. Avelo could confirm this.

 

[Dan]

Nope. The outer cylinder is a carbon wrapped AL shell. The gas is held in a bladder inside the cylinder. It is attached at the valve at the top of the cylinder. Adding ballast is done by pumping water into the cylinder (but outside the bladder) which compresses the bladder. The bladder is filled to an initial pressure below the cylinder's rated capacity so you can safely add up to 4 liters of ballast water at the beginning of the dive.

Dumping ballast does not require the pump. You manually open a purge valve which allows the gas pressure to expand the bladder and thus expel the (ambient pressure) ballast water.

Avelo has a little animation of this here: Avelo - Technology

I took a screenshot of it during the animation of the purge (blue is the ballast water).

View attachment 826928

Thank you for correcting me. The one hour Avelo weibinar with Dan Orr really helps clear up my confusion. The bladder can take up to 20,000 psi pressure. That’s a pretty amazing material properties.

 

[Dan]

How is that calculated?

Is that precise or an estimation?

From watching the Avelo webinar, the air pressure profile is pretty close to a regular SCUBA tank. So I would think I can use my Teric for this system.

 

[scubadada]

Hi @Dan

You are correct, you can use your Teric. The day that my wife and I rented Avelo equipment and did 3 independent dives, I used my Teric and Oceanic VT3 operating off a single transmitter, my wife used a hosed Oceanic Pro Plus 2.

Here is my Teric profile. Before running the pump, the cylinder was at 3028 psi. After running the pump for 1 minute and starting the dive, the cylinder was at 3610 psi as shown in the graph. At the end of the dive the cylinder pressure was 1418 psi. I vented the ballast water, and the pressure was 1206 psi.