How did the old J valves work?

[PerroneFord]

Any particular reason?

The critical question here is which is more likely:

1) A failure of the isolator itself.

2) A failure of the right tank burst disc, left tank burst disc, right tank neck o-ring, or left tank neck o-ring.

"It's just better" is not an answer.

Walter appears to be arguing that failure #1 is more likely, and introducing this failure to deal with any of the #2 failures is foolish.

I've never seen an o-ring fail in the manifold. I have seen several burst discs go, and I have seen a neck o-ring fail. So for my money, I'll take the isolator. Others may feel differently and that's fine.

 

[Walter]

I've never seen an o-ring fail in the manifold. I have seen several burst discs go, and I have seen a neck o-ring fail.

So have I - when the tank was being filled.

 

[jonnythan]

I think you two are at an impasse unless either one of you can come up with some hard data concerning failure rates.... and I don't think that's going to happen.

So, agree to disagree?

 

[PerroneFord]

So, agree to disagree?

I did that a long time ago.

 

[stas]

One benefit of an isolation manifold (in my opinion, much bigger then protecting against neck failures) is that the isolator affords you the option ofbeing wrong about where the problem is. The first step in a shutdown procedure is close the isolator. That is because when a major failure occurs, there might be lot of confusion imediatley after the event. It may not always be clear where the problem is. One possibility that I have personaly seen happen was a guy was entering a wreck, caugh his drysuit inflation hose, which was running from the right post to the left hand side, and cut it. The first thing he did was shutdown the isolator. Its easy to make a mistake about where such a leak is. Thats why isolating the tanks first is a good idea.
Stas