Rotating Crossbar vs Captured O-Ring?

[mahjong]

Can anyone explain the benefits of a captured O-ring manifold over the rotating crossbar manifold. Looking at the OMS website, for example, they offer both. The two manifold's look identical in function, with one exception: the rotating crossbar manifold centerline is adjustable, from 209mm - 222mm, whereas the captured O-ring manfold centerline is fixed at 215mm. I cannot seem to find another difference between these two manifolds, so why have the captured O-ring manifold? Is it a less expensive alternative when you know with certainty what your centerline is?

OMS SCUBA Valves & Manifolds http://www.OMSdive.com

 

[D_B]

... OMS FAQ http://www.OMSdive.com

the difference (if I understand correctly) is much like a DIN valve , the captured O ring is a face seal and not on the side like on the roatating one and can not blow out/slip out the gap that is needed for the O ring on the rotating crossbar

 

[Tortuga68]

D_B is correct - the face seal provides (technically) better sealing with a DIN-style captured o-ring. The rotating crossbar uses a barrel seal (usually 2 or 3 o-rings in case of failures), so you get the benefit of being able to adjust the length with the sacrifice of the (technically) less secure seal

In practice, unless you're bashing your manifold on overheads all the time, the rotating crossbar/barrel seal is just as good

The other difference is that you can alter the angle of the isolation valve knob - towards or away from your head - on the rotating style

 

[mahjong]

Got it. Makes sense. Many thanks!

 

[cool_hardware52]

D_B is correct - the face seal provides (technically) better sealing with a DIN-style captured o-ring. The rotating crossbar uses a barrel seal (usually 2 or 3 o-rings in case of failures), so you get the benefit of being able to adjust the length with the sacrifice of the (technically) less secure seal

Current barrel oring style manifolds are *NOT* adjustable for varying center to center distances on doubles.

They do allow for the two modular valves to be positioned facing the same direction.

Tobin

 

[mahjong]

Here's the reply from the people at Thermo when I asked them about the adjustability of their rotating crossbar manifold:

"The Center to Center on this valve is 215mm or 8.46". It is adjustable +/- 0.1"."

That's not much adjustability, but I guess it is something--hopefully it will be enough to accommodate my twin Faber 72's (new shorter ones, with 6.84" diameter), which I am mounting onto bands custom build for 6.9" diameter and 8.5" spacing.

You said "current," did anyone ever make adjustable barrel O-ring style manifolds? Or were you leaving open future possibilities?

Current barrel oring style manifolds are *NOT* adjustable for varying center to center distances on doubles.

They do allow for the two modular valves to be positioned facing the same direction.

Tobin

 

[cool_hardware52]

Here's the reply from the people at Thermo when I asked them about the adjustability of their rotating crossbar manifold:

"The Center to Center on this valve is 215mm or 8.46". It is adjustable +/- 0.1"."

That's not much adjustability, but I guess it is something--hopefully it will be enough to accommodate my twin Faber 72's (new shorter ones, with 6.84" diameter), which I am mounting onto bands custom build for 6.9" diameter and 8.5" spacing.

You said "current," did anyone ever make adjustable barrel O-ring style manifolds? Or were you leaving open future possibilities?

I have no plans to produce manifolds. We have produced extensions for special purposes.

The barrel type provide one turn or less per side. This is not for adjusting the center to center length, but to allow the valve orifices to be oriented as needed.

If you exceed one turn per side (1mm) the outer barrel oring is un ported.

Tobin

 

[Tortuga68]

Current barrel oring style manifolds are *NOT* adjustable for varying center to center distances on doubles

So when OMS say, as per the OP, that their rotating crossbar manifolds have a manifold centreline distance of 209mm - 222mm, what is it that they mean?

 

[mahjong]

Interesting, Tobin...I've no doubt you are correct, but now I am thoroughly confused.

1. It would appear that there is plenty of room for adjustment without the outer O-ring becoming unported--the arm extension on the modular elbow valves is quite long. That said, the Thermo guy's response surprised me because I would have thought there was more adjustability. So, again, you are correct and I haven't yet figured it out.

2. My local technician, in reference to his Scubapro isolation manifold, said it was "very" adjustable. Is this because the Scubapro manifold is an older style, ie, not a "current" manifold? Or is 1mm each way "very" adjustable, in comparison to the fixed nipple-to-nut or captured O-ring designs?

I have no plans to produce manifolds. We have produced extensions for special purposes.

The barrel type provide one turn or less per side. This is not for adjusting the center to center length, but to allow the valve orifices to be oriented as needed.

If you exceed one turn per side (1mm) the outer barrel oring is un ported.

Tobin

 

[cool_hardware52]

Interesting, Tobin...I've no doubt you are correct, but now I am thoroughly confused.

1. It would appear that there is plenty of room for adjustment without the outer O-ring becoming unported--the arm extension on the modular elbow valves is quite long. That said, the Thermo guy's response surprised me because I would have thought there was more adjustability. So, again, you are correct and I haven't yet figured it out.

2. My local technician, in reference to his Scubapro isolation manifold, said it was "very" adjustable. Is this because the Scubapro manifold is an older style, ie, not a "current" manifold? Or is 1mm each way "very" adjustable, in comparison to the fixed nipple-to-nut or captured O-ring designs?

If you did a cutaway on the valve (female) and assembled the ISO bar you'd see the engagement of the outer oring is quite short.

In order to produce the ISO bar extensions I mentioned I had to carefully investigate this relationship.

Are the SP manifolds different? I don't know, but I can say many folks in scuba incorrectly assume all barrel manifolds are "adjustable"

Tobin