The Isolation Manifold, lessons not learned and a small defence of the IUCRR

[sea_ledford]

Isolation manifolds, where the solution to fix one leaking o-ring is to add 5 more (or 4 and a crush washer).
People go on and on about not adding failure points, but the weakest link in any valve is the handle and the serviable guts. So how does it make sense to add a third weak link to just-in-case solve an incredibly rare in-water problem (blown burst disk or massive leak of a tank neck o-ring)? Oh, and let's put it where its hard to get to, and set at a different orientation to every other valve.

I'm actually surprised that with the wide acceptance of sidemount (and the absolute aversion of the UDT sidemount isolator) that independent doubles haven't been widely adopted.

 

[DiveGearExpress]

These two tektips have been on our site for years...

Manifold Crossbar Isolator Valves May Not Improve Safety | Dive Gear Express®

Manifold Crossbar Isolator Valves May Not Improve Safety The use of an isolator valve on the manifold cross bar of doubles is a relatively recent introduction in the sport, but their use is now nearly ...

www.divegearexpress.com

Pressure Release Devices aka Burst Disk | Dive Gear Express®

Burst Disks in SCUBA Valves Are Not What You Think In the U.S. at the turn of the twentieth century, a series of boiler explosions caused significant loss of life. The most famous of the accidents, ...

www.divegearexpress.com

 

[TrimixToo]

I think burst disks are a vestige of when scuba tanks had tapered thread valves. O ring sealed valves aren’t the same and burst disks don’t make a lot of sense in them, imo.

Is that because you believe the O-ring will fail before the burst disc would blow? (That might be the case, I just want to know the reason.)

 

[rx7diver]

A couple of months ago I purchased a NOS U.S. Divers solid-bar (single-piece), single-outlet doubles manifold (to use with my DH reg). It is absolutely beautiful in its lack of complexity.

When I first received it, while I was venerating it, I began thinking how neat it would be if some manufacturer would produce a solid-bar, dual-outlet manifold (sans isolator). I cannot imagine this being difficult to manufacture. I would be all over it! (Manufacture it so that it will accept 200 Br DIN regulators, please.)

I dive an old-school Y-valve for my single-tank recreational solo diving to moderate depths in temperate water, and absolutely love this simple configuration.

I did try--once (!!)--diving a Y-valve on my one huge tank (an OMS/Faber LP 121/125 that I last week listed for sale in the Scubaboard Classifieds), and absolutely hated it. Now, a solid-bar, dual-outlet manifold (which behaves like a Y-valve), though, would allow me to BM a pair of moderately-sized cylinders, instead of a single huge cylinder, a configuration that almost certainly will satisfy!

Imagine: A dual outlet manifold without that other valve, and without all those other O-rings!

rx7diver

 

[Angelo Farina]

Do you mean something like this?

That is 300 bars not-insulated manifold, great with our European 7 liters, 300 bars tanks...
No burst disks, O-ring encapsulated in a conical cavity at the entrance of the tank (impossible to extrude), double O-rings on the manifold connector...

 

[PfcAJ]

Is that because you believe the O-ring will fail before the burst disc would blow? (That might be the case, I just want to know the reason.

O ring should fail before the tank fails.

 

[Angelo Farina]

O ring should fail before the tank fails.

It depends. Here in Europe the O-ring is lodged in a conical cavity inside the tank. The valve has a flat surface pressing the O-ring inside the cavity.
This means that the O-ring cannot be extruded.
In fact, during periodic pressure test, you can overpressurize the tank with water to the point of breaking it (around 400-450 bars) and the O-ring does not fail...
In the past (in the seventies) we had tanks with no cavity (flat surface on the top surface above the thread), the O-ring was lodged in a circular cavity inside the body of the valve, and this was possible to extrusion, particularly if the O-ring had small Shore rating.

 

[rx7diver]

Do you mean something like this? ...

@Angelo Farina ,

Not quite. I am thinking of a manifold that is a single piece--i.e., milled from a single piece of brass. (So, no center section to screw in.) Use "standard" C-C tank spacing.

I would prefer to be able to mount a DH reg in (below) the center of the manifold. And that the second reg could be mounted over the diver's right-hand cylinder, in the "usual" position of a primary reg.

This would be quite simple, and quite slick! A Y-valve on steroids!! I would use it for recreational solo dives to moderate depths using EAN that would permit very long NDL times.

rx7diver

 

[Daedalus]

@Angelo Farina ,

Not quite. I am thinking of a manifold that is a single piece--i.e., milled from a single piece of brass. (So, no center section to screw in.) Use "standard" C-C tank spacing.

I would prefer to be able to mount a DH reg in (below) the center of the manifold. And that the second reg could be mounted over the diver's right-hand cylinder, in the "usual" position of a primary reg.

This would be quite simple, and quite slick! A Y-valve on steroids!! I would use it for recreational solo dives to moderate depths using EAN that would permit very long NDL times.

rx7diver

How would you thread the tanks on?

 

[tursiops]

How would you thread the tanks on?

LOL. Just pick up one of the tanks and spin it around.