Review Diving the Avelo System

[scubadada]

I received an update email from Avelo this morning. You can sign up for these updates on the Avelo website. They will be making announcements regarding the sale of Avelo equipment through Avelo Dive Centers at the Los Angeles Scuba Show June 1-2.

Avelo holds periodic webinars that are an opportunity to get more information and to ask your questions. The next webinar in June 20. you can register on the Avelo website.

 

[Belzelbub]

Avelo is safer than standard scuba. There are fewer things that can go wrong and if something goes wrong it is a slowly developing problem and easy to manage. On standard scuba a problem can be an emergency. Having seen a shoulder dump valve blow off a divers bcd at 70' I can assure you that this does happen. Not often but it happens. And it's urgent. A more common scenario is a self inflating bcd. This can also get ugly fast.

I can't really comment on what can go wrong on the Avelo. I think it's probably more than you are implying, but I'll leave it as I haven't actually dove one.

Regarding the shoulder dump valve. Yes, it's rare, and is a problem that can happen. However, I'm not certain I'd qualify this as urgent in every case. For a diver that is severely over-weighted, then this could be urgent. For divers using the correct amount of weight, this is more of an annoyance. If you can't swim up with an empty BC, then you have way too much weight. The Avelo system seems to be one possible solution to this problem, but it is certainly not the only or simplest one.

Same with the stuck inflator. This can likely be avoided with good routine maintenance, but if it happens, it is an easy fix in water by disconnecting the LPI hose.

I could definitely see pump failures (either way) as a problem similar to the two you described.

 

[hammet]

Why does the avelo system need to be incorporated within the main cylinder?
Why not a separate, uncompressible volume, say a second cylinder with a bladder or piston system connected to a low pressure inflator hose as well as a battery powered water pump?

 

[rmssetc]

Why does the avelo system need to be incorporated within the main cylinder?
Why not a separate, uncompressible volume, say a second cylinder with a bladder or piston system connected to a low pressure inflator hose as well as a battery powered water pump?

Do you mean something that looks like a 19cu pony bottle, with an integrated bladder & battery & pump and IMU (to measure ascent/descent) & HP hose (so that the "buoyancy controller" could track the mass of gas used during the dive, if the tank volume is input as a factor), that could be strapped to any generic cylinder used for diving?

That would be a terrific game-changer, particularly for rental/recreation divers.

 

[Wibble]

Do you mean something that looks like a 19cu pony bottle, with an integrated bladder & battery & pump and IMU (to measure ascent/descent) & HP hose (so that the "buoyancy controller" could track the mass of gas used during the dive, if the tank volume is input as a factor), that could be strapped to any generic cylinder used for diving?

That would be a terrific game-changer, particularly for rental/recreation divers.

Why the pump? Why not use backgas to push the water out? Then you just need an OPV valve to let the air out and water in.

Hey, just use something like the i3 BCD control: up to put air in (and water out the bottom), down to let water in (and air out the top).

No pump means simplicity -- no batteries, pump motor, electrical connections, switches...

 

[rmssetc]

Why the pump? Why not use backgas to push the water out? Then you just need an OPV valve to let the air out and water in.

Hey, just use something like the i3 BCD control: up to put air in (and water out the bottom), down to let water in (and air out the top)

I like the idea of that kind of simplicity.

However, I haven't run any of the numbers, but I'm assuming there's a reason why Avelo, with 3200+ PSI tanks, don't use backgas instead of a pump.

Over the course of a dive, how would the amount of air lost to evacuating water from the buoyancy tank compare to the amount of air used in a BCD or wing?

 

[inquis]

Over the course of a dive, how would the amount of air lost to evacuating water from the buoyancy tank compare to the amount of air used in a BCD or wing?

Need to compensate for 5 lb of gas consumed, so 2.3 L of water added by the end of the dive. Plus a liter or 2 to become neutral at the beginning of the dive.

 

[EdMcNeill09]

Why does the avelo system need to be incorporated within the main cylinder?
Why not a separate, uncompressible volume, say a second cylinder with a bladder or piston system connected to a low pressure inflator hose as well as a battery powered water pump?

Avelo is simply the first successful attempt to use ballast for neutral buoyancy. There have been many earlier attempts to do this. Including, I believe, what you are suggesting. I'd have to dig a bit to get the names of other systems. As I recall hearing these other attempts ran into issues that were resolved by using the main cylinder. I am not a historian of Scuba though so perhaps there are others here who recall the names of these systems.

 

[lowwall]

I like the idea of that kind of simplicity.

However, I haven't run any of the numbers, but I'm assuming there's a reason why Avelo, with 3200+ PSI tanks, don't use backgas instead of a pump.

Over the course of a dive, how would the amount of air lost to evacuating water from the buoyancy tank compare to the amount of air used in a BCD or wing?

The pump is just to add ballast water. To remove it, you open a manual purge valve to the part of the tank containing the ballast water. The pressure in the gas bladder causes it to expand which forces the ballast water out through the valve. That's why losing battery power is not a safety issue. Even if you breathe your tank down so low that your regulator's first stage won't operate, there is still enough gas pressure in the bladder to purge ballast water.

There's an animation of this around halfway down this page: Avelo - Technology

 

[lowwall]

Avelo is simply the first successful attempt to use ballast for neutral buoyancy. There have been many earlier attempts to do this. Including, I believe, what you are suggesting. I'd have to dig a bit to get the names of other systems. As I recall hearing these other attempts ran into issues that were resolved by using the main cylinder. I am not a historian of Scuba though so perhaps there are others here who recall the names of these systems.

We all use ballast, mostly in the form of lead and occasionally in the form of a stainless steel plate shaped to allow the addition of a tank, wing and harness. Since the invention of the BCD, divers have added sufficient ballast to get themselves neutral at the most buoyant part of the dive, i.e. when they are shallow (if wearing neoprene) and have used up most of their gas. This means we are overweighted for the rest of the dive which we compensate for by increasing our volume without increasing our weight (by adding gas to a wing), thus decreasing our system density. The problem this creates is that the gas bubble and thus system volume will fluctuate with changes in depth, especially when shallow, which requires the diver to react by changing lung volume or adjusting the amount of gas in the wing.

Avelo, on the other hand, increases density by adding ballast in the form of water while keeping volume the same. The advantage of Avelo is that since your volume doesn't change, your overal density will only change very slowly as you use up gas. So once you are close to neutral, you will stay there for many minutes even as you ascend or descend (assuming you are not using a heavy wetsuit). The disadvantages all come from using water as your ballast material. The main disadvantage is the low density of water (approx 1.03 g/cc for sewater) compared to lead (11.2 g/cc) or stainless steel (8 g/cc) means it takes a lot of space, thus limiting how much you can add. This in turn means you need a physically large cylinder for the amount of gas it carries, you have limited positive buoyancy on the surface and limited ability to counteract the volume changes of thick neoprene as you descend and ascend. These factors make Avelo unsuited for rough or cold water. Another disadvantage is that adding water to the same volume that already contains high pressure air means you need the added complexity, cost and potential failure points of a high pressure pump, electronics, and a battery. You also have to keep the battery charged and pay attention to its charge state.

I just can't see this taking off except for possibly a small subset of wealthy tourist divers who will happily pay a premium to have someone else handle the details of their Avelo dives. But I suspect the need to get weighting just right is going to be a problem for these folks.