Doubles manifold for partial pressure blending?

[211ratsbud]

Is there a manifold suitable for partial pressure blending?

 

[tbone1004]

what do you mean? If the manifold is O2 cleaned, there is no reason you can't PP blend thru it...

 

[guruboy]

The following will not work to mix gas -
1) close isolator
2) fill first tank with O2
3) fill second tank with Air
4) open isolator to "blend"

 

[DA Aquamaster]

As noted above, you can't put one gas in one side and another gas in the other and expect them to mix. Well....I suppose browning motion might take care of it in a year or so.

You'll be putting the O2 or the HE in first depending on what the pressures are in your supply tanks, and then you'll be topping with air or 32 percent.

I've found it helps to put the last few hundred PSI in fairly aggressively to ensure there is enough flow to mix the gas in the tanks thoroughly, particularly with a bottom mix with a lower oxygen content. As an example, when I first started blending nitrox and would be doing a higher percentage deco mixes like 50% or 80%, we'd use very slow fill rates in the 50 psi per minute range. The end result in an upright tank would be a very low O2 percentage from the topping gas in the top of the tank not mixing with the O2 in the bottom of the tank. We'd have to roll the tanks on the floor for several minutes to get the gasses to mix.

My fill rates have gotten a bit faster even with pure O2, and I'll still put the last couple hundred psi in fairly quickly even with a deco mix, to ensure there is enough turbulence in the tank actually mix the gasses. But don't go crazy.

 

[boulderjohn]

I am wondering if the OP's concern is that the manifold he has says it cannot be used for pure oxygen (actually anything over 40%).

If that is the concern, then no, there are no manifolds that can be used for partial pressure blending. Similarly, there are no scuba valves of any kind that an be used either for partial pressure blending or for use with high oxygen mixes. That, at least, is what the manufacturer will tell you. It was covered in my PSI recertification course this year, in fact. The path of gas flow has to many sharp turns.

BUt everyone does it, don't they? And a PSI inspector will certify your tank for oxygen service, knowing full well that it technically does not qualify.

 

[211ratsbud]

The following will not work to mix gas -
1) close isolator
2) fill first tank with O2
3) fill second tank with Air
4) open isolator to "blend"

Hahaha

 

[211ratsbud]

I am wondering if the OP's concern is that the manifold he has says it cannot be used for pure oxygen (actually anything over 40%).

If that is the concern, then no, there are no manifolds that can be used for partial pressure blending. Similarly, there are no scuba valves of any kind that an be used either for partial pressure blending or for use with high oxygen mixes. That, at least, is what the manufacturer will tell you. It was covered in my PSI recertification course this year, in fact. The path of gas flow has to many sharp turns.

BUt everyone does it, don't they? And a PSI inspector will certify your tank for oxygen service, knowing full well that it technically does not qualify.

This is my question. We have special valves that have no right angles for singles.

Thnx

 

[DA Aquamaster]

That's one of the primary reasons to keep the flow rates slow, particularly with higher O2 percentage mixes. Gas flowing across a sharp edge can cause it to heat up, and that can create an ignition source.

Similarly, you want to avoid any sudden stops for the gas for the same reason as the sudden compression can cause heat - just like a diesel engine. Open valves slowly.