Old OMS manifold still considered "safe"

[SomeGuy509]

Hi All,

When I picked up a bunch of gear over the summer one item I got was a 300 bar OMS manifold like the one pictured below. I was after some HP120s and this was thrown in as part of the deal. I noticed that it uses a single o-ring and setup as a face seal for the isolator between the two posts. Newer manifolds seem to use 2 o-rings per side that seal circumferentially.

I seem to recall reading something about certain manifolds being less safe due to the possibility of leaking if they are bumped. The single o-ring face seal seams a bit less secure then the double concentric but I'd like to try and confirm one way or another.

I'd like to try and do Into to Tech in the next year or two and I am wondering if I need to factor in the cost of one of the newer XS Scuba manifolds since I only have 7/8in neck tanks. The other thought may be that just for ITT and "lighter" tech diving the risk is low enough for the design to not matter.

Thanks!

 

[runsongas]

the weakness of the face seal manifold is that the center to center distance is not adjustable. you then end up having to match bands, manifold, and tanks exactly.

 

[SomeGuy509]

So in my case I am lucky there since the guy sold the 120s banded with pressure in them. I split them apart since I wanted them for recreational use but I have all the parts to build them back up.

Good info.

 

[Caveeagle]

I still use a couple of them. No worries.. they are fine.

 

[rjack321]

they are fine, but parts for those valves will almost exceed the price of new valves (((

 

[guruboy]

Replacement parts and even caps for splitting the valves into L/R stand-alone can still be obtained. Look up Lake Jocassee scuba (or something like that). There’s a couple threads that mention them.

 

[happy-diver]

Here's parts, what parts

and if you're stuck bronze your spindles back

and punch your washers and seats from teflon or nylon

and punch your copper washers from copper

and get your orings from the oring shop



and I've been abusing one of those manifolds on and off a couple of faber 100s for 20 yrs
without a problem, just make sure the valve and manifold faces are aligned flush, tight before
you final tighten the bands, before you do the final tighten nip on the crossover if required

and don't be trying to rotate the crossover once assembled and under pressure

like some dumkopfs would have you do

 

[tmassey]

the weakness of the face seal manifold is that the center to center distance is not adjustable. you then end up having to match bands, manifold, and tanks exactly.

To be more specific: these manifolds are fixed at 207mm (8 1/8”) spacing between the valves. Current manifolds have 215mm (8.5”) spacing to allow for 8” tanks. If you have 7.25” tanks and all the parts why should you care?

The biggest issue is the bands. I’ve only seen crappy bands in 207mm. They work if you’re careful, but they’re not rugged. But I’ve got two sets of them, and absolutely no hesitation to dive them.

 

[Caveeagle]

they are fine, but parts for those valves will almost exceed the price of new valves (((

My local shop does a lot of valve rebuilds, and had everything needed right in his bulk kit. Nothing more, or less difficult than other valves.

I do have a couple of “OMS” kits I bought a couple years ago, and I paid around $15 per kit, but that’s pretty typical for a “convenience” fee.

 

[tmassey]

I'm not so sure of the parts availability as others...

Notice the link that rjack included (for valve seats): they clearly state 'not for Genesis valves'. Your valves are clearly not actual-Genesis valves: they don't have the slanted ports. BUT: OMS didn't design those valves, and I've personally only seen one *manufacturer* of manifolds that used the face-sealed configuration: Sherwood/Genesis.

Here's my question: while they say OMS on the outside, what type of parts are in the *inside*? Especially the seat. For the most part, everything else is pretty generic, but the seat might be an issue.

Now that I type this, I'm not certain what type of seat a Genesis *manifold* valve uses. I've always *assumed* that it used the same seat as the single-tank 6300 slant-back valve. And it's not impossible to get parts even for those (Northeast Scuba Supply has seats for the 6300-series, for example), just not from your LDS. Can anyone with specific knowledge comment on that? (I've never had to replace a valve seat.)

Your question was safety: there is none, especially without the slant back. (With the slant back: allows water to pool in the valve, and elevates the first stage which can make it stick out more and easier to whack.) If you have all of the parts and they're functional, use them, no problem.

However, for long-term issues: they require matching valves, isolator and tank bands, and the only bands I've ever seen are narrow and thin and spot-welded. If any of them break, you'll need to likely replace them all, or try to cannibalize another set.

Or, replace the entire set (after something breaks) with a modern-style manifold. Such things do exist in 7/8" both new and used, and (should) use the same parts as a 3/4" valve/manifold from the same manufacturer. And this would allow you to use modern (thick, wide and fully welded) tank bands, too.