automatic vent valve for bc or wing?

[formula1mb@aol.com]

I've been looking into drysuits recently and thinking of buying my first but when I was looking at the features, I noticed almost all have the automatic vent valve on the shoulder to maintain a constant volume of air in the suit.

Afterward, I started wondering why don't any bc's have automatic, adjustable vent valves to maintain a constant volume of air? Sure they have the overpressure valves but why not an adjustable vent valve too?

Not only would it make it easier to maintain buoyancy and reduce the amount of fine tuning needed when changing depths, but it could be a great safety tool too esp for newer inexperienced divers. In an emergency ascent than, you can still vent manually but at least the bc would more or less take care of the majority of the venting and eliminate the risk of a completely out of control rocket ride to the surface.

Plus for a diver rescue, the task loading would be reduced since most of the venting would be automatic.

Am I missing something or isn't it a good idea? Of course you would still have the manual inflator for fine-tuning and emergencies but curious to see if it has been tried and if not, why not?

Robert

[awap]

One reason is because a constant volume of air is not the solution to correct buoyancy.

[formula1mb@aol.com]

Yes I realize that but wouldn't it reduce the need to fine tune your buoyancy? I'm not saying it's a replacement for proper buoyancy skills but simply a way to make it easier.

Plus for emergency ascents or rescues, it would reduce the task loading and also reduce the chances of an out of control ascent.

[formula1mb@aol.com]

If you ever read on the bsac forum and other places, a lot of drysuit divers already do that and use the drysuit only for buoyancy control----letting the vent valve maintain a more or less constant volume and using the wing for backup.

[Peter_C]

If you ever read on the bsac forum and other places, a lot of drysuit divers already do that and use the drysuit only for buoyancy control----letting the vent valve maintain a more or less constant volume and using the wing for backup.
Most experienced drysuit divers use the gas in the drysuit to only remove squeeze (Also keeps loft in the undergarments for warmth) and the wing to control buoyancy.

I want my wing to only vent when I pull the dump valve or push the button.

[spectrum]

First of all the DS valve is a one way street. It does nothing to compensate for compression as you go down. That would require a lot more complexity.

I can see your point of preventing runaway ascents with new divers but IMO that is what training and shallow novice dives are for.

I and others before me have toyed with the concept of automatic control but it would need a lot of inputs including the compression response curves of compressible items such as neoprene gear and a signal to permit / halt a depth change. The system would also need to be position independent so it could shift on demand.

Pete

[formula1mb@aol.com]

First of all the DS valve is a one way street. It does nothing to compensate for compression as you go down. That would require a lot more complexity.


Pete


Good point and I wasn't referring to a valve that would compensate for both descending and ascending but only for ascending like a DS valve. You still need to add air when you're descending to establish neutral buoyancy at the deepest part of the dive but than when you start ascending the valve would start to vent. That way you only need to add air at the beginning of the dive apart from fine-tuning and when you start ascending the valve would handle the bulk of it. At least it would greatly reduce the serious possibility of an out of control ascent during any type of rescue, OOA situation, etc.

[halocline]

I am of the mindset that BCs in particular need to move in the direction of simplicity and minimalism, not added complexity and automation.

Even though your valve idea might lessen runaway ascents, I don't think it would eliminate them, and if a student diver became a little dependent on it and it stuck, that could be pretty problematic. Another safety issue with BCDs is establishing positive buoyancy at the surface; you could still do this but it would complicate it a bit. Unfortunately that added task loading would happen at exactly the time most new divers are at risk; on the surface.

[formula1mb@aol.com]

You dump the weights at the surface, per most standard rescue classes. I don't see it as being that much more complicated, you can replace the standard overpressure valve with an adjustable vent valve.

Drysuits already use them, not like it's a new unknown technology.

[formula1mb@aol.com]

Plus I'm not saying get rid of the standard inflator, that would still be there for fine-tuning, adding air, manual inflation, etc.

[knowone]

One reason you can do it is because a constant volume of air is the solution to correct buoyancy at your depth.
Great idea if you're busy and doing a crocodile tooth profile.
Because experienced divers used to only wear the suit and with depth compression just out of suit squeeze is sufficient.
I'm going out to install one in a right shoulder opv hole and a rear bottom one, see how it goes.
Ya gotta keep it interesting.

[TSandM]

It's a good question, I think. My guess is that the biggest reason it isn't done is that being positive at the surface is a life-saving thing, and should be as easy as possible for either the diver or a rescuer to accomplish. If someone is in distress on the surface, having to remember to close a vent to keep the BC inflated may be beyond them, as remembering to dump their weights so often is.

[Peter Guy]

The "automatic vent" on a drysuit is NOT "automatic" in the sense that it vents when there is a "need" to vent, but, to the contrary, it vents "automatically" when air is presented to it. The "automatic" part is that it vents without being pushed -- NOT when it is "needed."

For example, if you are neutral at depth but then change your attitude so that the vent is high, you will vent "automatically" even though you really don't want to vent (which is a PITA for photography). Or if you are head down and start to ascend, the "automatic" vent WON'T -- and I can guarantee you will find your suit ballooned and you may well find yourself in an uncontrolled ascent -- even with the "automatic" vent.

In other words, "automatic" is a misnomer.

The possible benefits of an "automatic" vent on a BC are far outweighed by the negatives I believe.

[Nemrod]

First of all the DS valve is a one way street. It does nothing to compensate for compression as you go down. That would require a lot more complexity.

I can see your point of preventing runaway ascents with new divers but IMO that is what training and shallow novice dives are for.

I and others before me have toyed with the concept of automatic control but it would need a lot of inputs including the compression response curves of compressible items such as neoprene gear and a signal to permit / halt a depth change. The system would also need to be position independent so it could shift on demand.

Pete

Since most suit compression occurs in the first 15 feet and certainly by 30 feet I don't see that a big problem.

I don't think the OP meant to include a drysuit in his thought, only that his shopping for one was his inspiration when he learned about the CV valves.

I think this direction will be an evolution from the current "up and down" valves used on some BC jackets that do not have a corrugated hose at all. Dacor, AL, Mares have marketed such BCs already, it would be a simple step to incorporate a CV valve into the mechanism.

One thing that impacts this is liability, as long as scuba manufactuers can say the diver was in control and therefore any injury that resulted was a result of improper operation they are in the clear, as systems become more automated, doing more for the diver and removing diver control/input from the equation then they will find their liability exposure for injury may increase.

Increasingly in many fields from aviation to diving, lawyers and lawsuits act to dampen innovation and ultimately limit our choice.

Electronics are the next frontier in diving, we will see a return to a system approach, proprietary equipment and connections, where a perhaps two channel computer plugs into the regulator, BC, tanks and can regulate buoyancy, attitude, mix gas on the fly and compute deco, time remaining and even offer suggestions all on a HUD display.

Certainly divers trained in the last decade or so will suddenly find themselves "vintage" and espousing all of the downsides of integrated electronic controlled systems, the divers of the future who grew up with an I Phone installed in their hands and video game controllers in the other will laugh at the "old school" divers.

N

[LauraJ]

i'm in agreement with peter here...

the 'auto-dump' is a misnomer. it's just an adjustable overpressure valve. (OPV)

[formula1mb@aol.com]

The "automatic vent" on a drysuit is NOT "automatic" in the sense that it vents when there is a "need" to vent, but, to the contrary, it vents "automatically" when air is presented to it. The "automatic" part is that it vents without being pushed -- NOT when it is "needed."

For example, if you are neutral at depth but then change your attitude so that the vent is high, you will vent "automatically" even though you really don't want to vent (which is a PITA for photography). Or if you are head down and start to ascend, the "automatic" vent WON'T -- and I can guarantee you will find your suit ballooned and you may well find yourself in an uncontrolled ascent -- even with the "automatic" vent.

In other words, "automatic" is a misnomer.

The possible benefits of an "automatic" vent on a BC are far outweighed by the negatives I believe.


I realize that it won't vent exactly when it 'needs to vent' like a diver would himself. Obviously the diver still needs to use the inflator to fine-tune and still needs proper buoyancy skills. But like a drysuit, it would definitely assist in keeping ahead of the curve so that when you ascend and do finally need to vent, the valve if set correctly would vent perhaps 90% of it and you only need to fine-tune the final amount.

So if you ascend a fair amount, you would only need to adjust for a swing of perhaps 3-5 pounds of buoyancy instead of 10 pounds. Plus again for an emergency ascent, OOA situation, rescue or whatever the task loading would be far less. Or how about an inflator stuck open? If you have the vent valve, you would have more time to react before it becomes a critical situation.


Lynne brings up a good point about establishing buoyancy on the surface in an emergency and having to remember to close the vent. That is one problem that would have be thought about it. However, that seems like less of a problem than someone getting an air embolism from rocketing to the surface.

[Valaika]

Hmmm..just what I would want, a BCD that is designed to not hold air!

[it_mike]

Have you considered how you're going to adjust the valve resistance? My drysuit valve is adjustable for a reason. Heavier insulation requires greater volume.

[formula1mb@aol.com]

Like a drysuit valve, where you rotate it to adjust it, so you can click it from fully closed to varying levels of sensitivity depending on your configuration.

So the first time to set it up, you go to the bottom, set it to the loosest setting----inflate until you either get neutral or air starts getting dumped. If air is being dumped and you're still negative, you need more air, click it to the next level, than inflate until you're neutral. Than if it still dumps air before you're neutral, keep clicking up until it holds enough air.

Now you should be set for the rest of the dive and as you ascend it will hold about the correct amount of air. Obviously as you go up, you still need to fine-tune but a lot less than before.

[spectrum]

Don't forget that even the air in the BC is subject to compression/hence volume (displacement) change. Even with all else equal it will need puts and takes as you change depth.

I other words if it were that simple it would be in the shops.

Pete

[pjones]

This is the situation that I picture with this device and it scares me...

An OOA diver is required to do a CESA to the surface. Its chop on the surface and their adrenalin is pumping due to the stressed state of the diver. They are struggling to keep their head out of the water as they are huffing between the waves trying to catch their breath. They try to establish positive buoyancy by manually filling their BCD but their attempts fail because the air is now exhausting through the variable pressure dump valve. The exhaustion is now getting the best of the diver and they have no other option but to dump their Weight Belt.

The situation that could have been avoided by having a set OPV was made over complicated because of the variable pressure dump valve. By having a set pressure in a situation like this the diver doesn't need to waste valuable seconds trying to adjust their bcd for the surface during an already stressful and task loaded situation.

But maybe thats just my over active imagination. :dontknow:

[it_mike]

Like a drysuit valve, where you rotate it to adjust it, so you can click it from fully closed to varying levels of sensitivity depending on your configuration.

So the first time to set it up, you go to the bottom, set it to the loosest setting----inflate until you either get neutral or air starts getting dumped. If air is being dumped and you're still negative, you need more air, click it to the next level, than inflate until you're neutral. Than if it still dumps air before you're neutral, keep clicking up until it holds enough air.

Now you should be set for the rest of the dive and as you ascend it will hold about the correct amount of air. Obviously as you go up, you still need to fine-tune but a lot less than before.

This was my point. Think about the task loading, the likely mount points, and the manual process / dexterity requirements. This valve would be on a soft, flexible bag, tank side, above your shoulder. Is it a one handed or two handed operation? Does it work with gloves? Your drysuit is held in place by you by virtue of wearing it, and your arm provides counterpressure.

There is a reason your dump valves have pull cords.

[RJP]

Am I missing something or isn't it a good idea? Of course you would still have the manual inflator for fine-tuning and emergencies but curious to see if it has been tried and if not, why not?

Robert

Gear solution to a skill problem.

New divers are constantly venting/filling/venting/filling because they can't fine tune their buoyancy with their breathing. For a diver with proficient skills there's no need to vent at 80ft if you rise 10ft to overcome a ledge and then descend back down to 80ft. But an auto valve WOULD vent. and maybe someone with poor skills would fail to put more air in as they descended back down to 80-90-100-130-150...

[NC Wreck Diver]

When I drysuit dive, I put just enough air in the suit to equalize the squeeze, no more. The BC is used for Bouyancy at any depth. Yes, it is true that you need to monitor how much air is in the suit vs. what you need for bouyancy in your BC. The automatic valve will vent as you start your ascent, so you are manually venting your BC as you come up.

An automatic dumping valve in a BC would be dangerous. The BC should hold all your air in the vest/wing. If you were at the surface, and need to remain totally bouyant, a valve that would let air out if it was set to do so would be a problem.