RAID Cave 1 - Good Course?

[JonG1]

Is there any one failure on BM that could preclude access to at least some of the gas that they hold, provided the correct post/isolator is shut down in a timely fashion.

 

[txaggie08]

Sure. A catastrophic reg failure( either fully free flow, or shut down) or leak on one post with any failure inducing a leak or reg shutdown on the second post.

 

[JonG1]

Isn't that 2 failures though, I think worst issue could be failed tank neck o ring or burst disc, cos post isolation wont fix it but with isolator closed you still have half of what was left at point of shut down.

 

[txaggie08]

Just like with sidemount, there's no single point failure that will take away all your air.

 

[leadduck]

Is there any one failure on BM that could preclude access to at least some of the gas that they hold, provided the correct post/isolator is shut down in a timely fashion.

The most probable point of failure is the regulator or first stage; in that case, provided the correct post/isolator is shut down in a timely fashion, you survive. The problem here is that you survive if you notice the leak in time, if you identify, and close the correct post, and if you do so fast enough. That's too many "ifs" for most people to consider it safe enough for solo diving without another backup such as independent stage bottles or gas sharing with a buddy.
The most critical (although less likely) single point of failure is a broken manifold valve (e.g. mechanically damaged but seems to work until too late), as it could leak all gas quickly and you cannot do anything about it. Assessing the probability of these events is impossible because the probabilities are small, there's usually no detailed information made public about the causes for most accidents, and near misses don't make it into the news at all.

 

[JonG1]

Ive no axe to grind on either config, I am new to OHE but not to deco diving which shares characteristics. I usually dive solo and usually CCR which is arguably the tool of choice for my closest OHE.

That said I like to keep sharp on oc but only dive doubles and stages at present. SM will be added this winter.

I find the discussion interesting tho and if diving oc I carry what is effectively redundant bailout.

My point was that at the time of discovering a leak if you did nothing more than shut the isolator you would retain half the gas in the doubles.

No argument that identification and ease of shutdown is improved on SM.

Assuming that in both configs you identified and shut down at the same time at furthest point of pen the same vol of gas would still be available, if my maths is right!

 

[CaveSloth]

I'm a firm believer in choosing a configuration based on the requirements of the dive.

Other than "there are a lot of restrictions", when would sidemount be a requirement?

I am thinking we need something like what they would have in the military... a long list with a lot of situational modifiers, as you said, describing the exact way that various situations are to be handled in both backmount and sidemount and the sticky situations you may end up in with either. Those kinds of things are easy to forget so it would be good to have them documented.

 

[helodriver87]

Other than "there are a lot of restrictions", when would sidemount be a requirement?

I am thinking we need something like what they would have in the military... a long list with a lot of situational modifiers, as you said, describing the exact way that various situations are to be handled in both backmount and sidemount and the sticky situations you may end up in with either. Those kinds of things are easy to forget so it would be good to have them documented.

Logistics. Really isolated locations that require dry caving or paddling a small boat/kayak to access, as a couple examples. Much easier to get there with sidemount gear than doubles. Trust me on that one...

 

[JonG1]

Backmount: Not Dead Yet

 

[JonG1]

Backmount vs. Sidemount for cave diving - CaveDiving.com