The Good, The Bad, The Ugly of Side Mount

[halocline]

I couldn't open the deco stop link. The only reason I can think of that a freeflowing reg would empty a tank quicker at depth is because the majority of the air path is at IP, which does increase in absolute pressure with depth. I suppose it's possible that since there would be more pressure in that path, air could flow more quickly through the hoses. But, if you simply opened a tank valve at 100 ft and another one simultaneously at the surface, my guess is that the surface tank would empty more quickly. Not that it matters.......

 

[ianr33]

Link works OK for me. Maybe you need to be a member?
Anyway,here is a copy and paste. I think the figures are interesting.

<<<<Divers


Here is a little test I did at Eagles Nest cave on Feb 12th for a small article to be placed in issue 17 of Advanced Diver Magazine.

The question I wanted to answer was:

How much time would it take to empty a full aluminum 80 cuft cylinder from 3000 psi to 0 for the following situations and would depth affect the times.

1. Failed Burst Disk
2. Failed HP Hose
3. Failed LP Hose
4. Free Flow high performance regulator 2nd stage.

I completed the test on the surface (0 feet) with 4 aluminum 80’s and a Zeagle D50 regulator.

Here are the results

1. Failed Burst Disk = 72 seconds
2. Failed HP Hose = 22 minutes
3. Failed LP Hose = 83 seconds
4. Free Flow High Performance Regulator = 255 seconds


I then repeated the test at 4 atm’s / 99ft

1. Failed Burst Disk = Same within a second or 2
2. Failed HP Hose = Same within a minute
3. Failed LP Hose = Same within a second or 2
4. Free Flow High Performance Regulator = 155 seconds

I then repeated the test at 8 atm’s / 231ft

1. Failed Burst Disk = Same within a second or 2
2. Failed HP Hose = did not complete due to time restraints but would assume it would be with a minute difference
3. Failed LP Hose = Same within a second or 2
4. Free Flow High Performance Regulator = 91 seconds

The results show the small amounts of time a diver would have to solve a major equipment failure while at deeper depths.

The question I post for you is

What would be the best procedure to follow if such an equipment failure occurred to you and why?

1. Isolate manifold
2. Turn off affected post
3. Dive independents
4. Other answer

Next time you’re in your rig, conduct a test on yourself and your buddy by doing a shut down drill. Not cheating estimate in seconds how long it takes you to shut down you manifold.

By the numbers given above, estimate how much gas you would have lost, would you have enough left even if you where following the rule of thirds or half + 200.

The answers will affect the finished article.

Thanks for your responses

Curt Bowen >>>>

 

[DaleC]

Thanks ianr (and Curt)

I try to dive systems in applications where an equipment failure does not create a major issue so I don't really focus on that part of the issue. To me, the greater problem is user error and when I look at manifolds vs ID's I see the greater potential for user error in manifolds.

A failure behind the head is a good example:

With manifolds one must decide what to shut down, iso or post. Is it a burst disc, LP hose near the first stage or a valve O ring? Make a decision while one is losing gas and then determine if that was successful. If it was the left tank you then diving a blind tank. How much gas do you have left, how will this effect your exit? I know some people will say they have all the answers because their rig will only fail in a certain way and it doesn't matter how much gas is left because you are exiting anyways but I also believe there are a lot of people diving manifolds who don't.

With ID's you can look and see where the failure is and it doesn't matter whether you shut down or not because the two systems are not connected. While the failure leaves you with less available gas it also leaves you with a clear understanding of what has happened, how much gas you have left and what your exit should look like.

If we look at systems being used in the applications they are suited for, the only real issue becomes user error. It's pretty hard to argue that manifolds are safer than ID's in this regard, no matter what the scenario. ID's simply offer more information to the diver and allow more of a buffer towards their response.

 

[TSandM]

Dale, I think you have a very good point. No equipment you dive is going to function within the parameters you envision for failures and problems if the diver using the equipment isn't facile with the procedures, either physically or mentally. I have read a story of a very badly managed failure in sidemount; I have watched a fully certified cave diver do a valve drill in doubles that he couldn't completely without kneeling in the bottom of the open water basin (thus implying that any failure he might have that would involve shutting valves would blow the viz).

WHATEVER you use, you need to understand the downsides of your choice, and you need to practice emergency procedures until they are fast, smooth, and stress-free. One of the things that does bother me a lot about backmounted doubles is that people think it's okay to dive them, even if the only way they can do shutdowns is to writhe about, release straps, and fuss . . . if you can't shut a valve and the isolator FAST, you are better off with a configuration where you can. If you CAN do shutdowns quickly, AND you are diving environments where the physical dimensions of a backmounted setup are not a problem, you may be better in backmount.

Until someone can do a study of relative problem rates, it will remain a matter of opinion -- strongly held and vehemently contested, but largely unsupported.

 

[billgraham]

Link works OK for me. Maybe you need to be a member?
Anyway,here is a copy and paste. I think the figures are interesting.

<<<<Divers

Here is a little test I did at Eagles Nest cave on Feb 12th for a small article to be placed in issue 17 of Advanced Diver Magazine.

The question I wanted to answer was:

How much time would it take to empty a full aluminum 80 cuft cylinder from 3000 psi to 0 for the following situations and would depth affect the times.

1. Failed Burst Disk
2. Failed HP Hose
3. Failed LP Hose
4. Free Flow high performance regulator 2nd stage.

I completed the test on the surface (0 feet) with 4 aluminum 80&#8217;s and a Zeagle D50 regulator.

Here are the results

1. Failed Burst Disk = 72 seconds
2. Failed HP Hose = 22 minutes
3. Failed LP Hose = 83 seconds
4. Free Flow High Performance Regulator = 255 seconds


I then repeated the test at 4 atm&#8217;s / 99ft

1. Failed Burst Disk = Same within a second or 2
2. Failed HP Hose = Same within a minute
3. Failed LP Hose = Same within a second or 2
4. Free Flow High Performance Regulator = 155 seconds

I then repeated the test at 8 atm&#8217;s / 231ft

1. Failed Burst Disk = Same within a second or 2
2. Failed HP Hose = did not complete due to time restraints but would assume it would be with a minute difference
3. Failed LP Hose = Same within a second or 2
4. Free Flow High Performance Regulator = 91 seconds

The results show the small amounts of time a diver would have to solve a major equipment failure while at deeper depths.

The question I post for you is

What would be the best procedure to follow if such an equipment failure occurred to you and why?

1. Isolate manifold
2. Turn off affected post
3. Dive independents
4. Other answer

Next time you&#8217;re in your rig, conduct a test on yourself and your buddy by doing a shut down drill. Not cheating estimate in seconds how long it takes you to shut down you manifold.

By the numbers given above, estimate how much gas you would have lost, would you have enough left even if you where following the rule of thirds or half + 200.

The answers will affect the finished article.

Thanks for your responses

Curt Bowen >>>>

Thanks, this is exactly what I was talking about. FWIW, I've never seen a manifold fail underwater. I have seen one broken when a set of doubles pitched off a bench on a dive boat. My friend had a second stage basically explode in Jackson Blue recently so these types of failures do happen even with modern equipment.