BCD Failure

[emoreira]

Thanks for all the input. To answer some questions that have been brought up:

- This involved a REAR shoulder dump, not a front, airhose connected dump
- It seems that it really did unscrew, as nothing is obviously broken and it was able to be screwed back on. He is an engineer by profession so I imagine he would be able to tell if the threads were broken, but I'll ask him again
- This occurred at the end of the last dive of a week of diving

If the shoulder dump valve unscrewed, it should have been quite notorious that the valve cap was way separated from the BCD. The cap, valve plate and spring should have been hanging from the cord that goes to the puller.
In that scenario the diver should take off the BCD and rescrew it in the valve, put the BCD back on and go on.
Of course this requires some situation awareness and peace of mind. But that situation awareness would have found the dump valve cap almost unscrewed in the predive check. Also, buddy check should have found that prior to entering to the water.

 

[SlugLife]

Wearing a BC which holds no air and is taking on water in 5-ft seas is not going to feel good. If the diver is low on air, does not have a snorkel on their mask and is tired from the dive and is without a buddy nearby and is contemplating dropping lead, then there is really very little question about what to do.

If a diver is in a situation where dropping lead will not cause some type of significant problem (for example an uncontrolled ascent) and is considering that option, then decisive action should not be delayed.

Problems at the surface when it is rough can spiral out of control in one instant if the diver inhales even a tiny amount of water and their throat locks up. This is one reason why removing the regulator and calling for help or notifying someone on the boat that you are having an issue can cause a serious problem. Should a diver delay immediately dropping lead in this type of situation, their future ability to do so (and function in a logical and effective manner) can be completely lost.

Sometimes I doubt that some people who make comments about the benefits of being "theoretically" neutral at the surface have ever been caught in a washing machine situation, behind a boat with their regulator out of their mouth.

Having trouble at the surface is often significantly more complex, dynamic and actually dangerous than dealing with a situation when submerged 20 feet. The psychological stress of being slammed around, waves breaking over your mouth, face and head can be significant. The diver (at least temporarily and repeatedly ) is losing the ability to see, hear and control their position and attitude in the water and if they decide to spit the regulator it can spiral downward in an instant. Even having a breaking wave loosen and partially flood a mask can be the straw that breaks the camel's back.

Of course if you are totally calm, not winded, in good shape and comfortable in rough conditions, then it might not be a big deal, but for most people, you throw in a leg cramp on top of all this and "Houston, we have a problem".

I think it is so important that people be mentally prepared and are physically capable of dropping lead if/when they THINK they need to. I hear people constantly repeating comforting phrases like "anyone can call a dive for any reason" - which is NOT really true if you are a dive professional BTW, yet seem hesitant to acknowledge some of the benefits of dropping lead.

Your post seems to suggest all of us are wrong for pointing out the diver was probably over-weighted. I don't think any of us suggested the diver shouldn't have dropped weights.

 

[wetb4igetinthewater]

This is probably due to dive-training agencies not mentioning or emphasizing the SMB in the initial open-water class, or even Advanced Open Water. At least I don't remember it being mentioned the classes I took, and only really discovered SMBs about a year into diving, and then DSMBs about 2 weeks later. Instead, we all are required to buy snorkels, that most of us rarely ever use again.

I'm not sure at what point DSMBs are taught, maybe technical-diving? Deploying a DSMB below the surface takes some skill, but an SMB has a lot of utility around visibility for rescue, retrieval, or avoiding being run over plus really nice as an extra flotation device. These days I usually carry two, or 1 DSMB & 1 float-bag.

SMBs (inflation at the surface) has been the minimum requirement for open water for a few years already. Teaching DSMB is optional, which makes sense. Most courses are taught on the knees and newly certified divers have poor depth control, so asking them to inflate a DSMB from depth and not cork or crater is "expecting" too much. It is even too much to ask most dive pros to do that even. Though I like to call the surface SMB inflation skill "hurry up and inflate that balloon before that boat runs you over."

About the snorkels. Those are high margin products, same with fins. Hence the requirement of many shops to buy these. Just a way to compensate for inexpensive classes.

 

[AfterDark]

That is immaterial because the BC should be empty at the end of the dive by design. Taking on water is equivalent to a smaller BC, but it's still empty.

The BC could not have been empty if water was leaking in, it would have water in it.

Well, you open your BC dump vent so water can get in and go for swim with it. Let us know how you make out.

 

[wetb4igetinthewater]

Well, you open your BC dump vent so water can get in and go for swim with it. Let us know how you make out.

Law of inertia

 

[inquis]

open your BC dump vent so water can get in and go for swim with it.

No problem. Water doesn't sink in water.

Perhaps you could try an even easier demonstration: fill a pitcher or bucket with water and submerge it in the tub, pool, whatever. It's weight when submerged will be quite light -- even less than the empty bucket in air.

 

[johndiver999]

Your post seems to suggest all of us are wrong for pointing out the diver was probably over-weighted. I don't think any of us suggested the diver shouldn't have dropped weights.

I didn't suggest that at all. If the diver was wearing 5 lbs more lead than they need, is for the most part, irrelevant to the situation.

The story serves to remind me about the importance of having ditchable lead and being willing and able to drop it when it seems necessary.

The potential negatives of wearing a moderate amount of excess lead (like 5 lbs maybe) are negligible if the diver has a bc that works and one which he can control AND has the ability to drop that 5 lbs (or a little more) should it be necessary.

And wearing a BC that is full of water and which needs to be partially supported ABOVE THE WATER in order for the person who is wearing it, to maintain their head above the water, is going to be a problem in very rough 5-ft sloppy seas. There is a big difference between a BC that is full of water at the surface versus underwater. Just think about it a little.

Edit: Also, my first post on this thread ended with the following statement: "Perhaps the diver could try diving with a little less lead?".

 

[Centrals]

Yes, a whopping 1 kg -- easily compensated with a larger breath. This diver could not even SWIM up, almost certainly kicking very hard.

How many divers can maintain neutral buoyancy with an near empty tank at 5m? I honesty cannot so additional weight is required. So what happen if I have a half full/tank at 5m? I certainly need to add gas into my bc to keep me neutral because of the additional weight of the compressed gas.
Would I float with no air in my bc with a half filled tank on the surface? NO idea.

A large breath will certainly affect the buoyancy. But would it arrest a fast descent in that situation? I could not answer.

What is the definition of overweight? 1/2kg, 5kg?

 

[inquis]

The diver i

A large breath will certainly affect the buoyancy. But would it arrest a fast descent in that situation?

In the situation you pose -- weighted such that you're neutral with an empty tank but instead you have half a tank left (I assume an AL80)... yes, it should. First of all, the descent should not be fast. The net force pulling you down is only due to 1 kg. You only need 1 liter more of volume to compensate, which is well within the adult inspiratory capacity. People used to dive without BCs at all and would compensate for FULL tanks with just their lungs. There are numerous videos of buoyancy demonstrations to move bricks on the pool bottom without adding any air to the BC.

 

[Moerae]

No need to show any video.

Do you float with no air in your bc and with half a full/empty tank?

That diver still has 1500psi not 500 left in his tank.
1000psi and that is about 1kg.

It seems a little silly to say "No need for the video" when the video perfectly answers and demonstrates actual examples of your questions.

"Do you float with no air in your bc and with half a full/empty tank?"
He does exactly that in the video.

I think you're underestimating how much of a buoyancy swing your lungs produce. Most people do.

I am neutral at 10-15ft in my wetsuit & rec rig and I have tested that, at the beginning of my dive with a full hp100, I can float with completely full lungs. I can breath "normally" and keep my face above water with gentle kicking. At depth this will be a little harder and require gentle kicking even with a deep breath, but nothing I can't maintain comfortably for a while and ascending is not taxing. This is also demonstrated in that video.

In my drysuit I dive a little more negative. This is so that I can have more air in the suit for cold deco or safety stops than I normally use during the dive. But in that case I have the drysuit as redundant buoyancy and it's still only a little more negative.