How important is panel valve directionality?

[stiebs]

Panel valves like the Thermo or Sherwood ones listed below show directionality for gas flow. But connected to a manifold block for a basic fill panel, gas flow is in one direction when filling the storage bank, and in the other direction when decanting. It seems overkill to have a different flow path for filling and decanting, nor do I believe its it's common practice to do so.

Should the gas flow in the direction of the arrow on the valve when filling or when decanting? Does it really matter?

In-Line Valve 7000 psi 1/4" FNPT x 1/4" FNPT

In-line valve, gas flow from 1/4" FNPT to 1/4" FNPT. 7000 psi (482 bar) maximum pressure.

nuvair.com

YVA3010A Panel Mount Line Valve 7000PSI

Panel Mount Line Valve (YVA3010A)7000PSI Air Control Valve 1/4" Male NPT X 1/4" NPT Female thread. Sherwood style.

www.breathingair.com

 

[iain/hsm]

First off. The direction arrow is on all manufactured rising plug panel and In line valves for good engineering design practice and a specific reason.

The wise follow that line while the foolish and stupid do whatever they want.

The reason that you find them fitted back to front on the discharge side of a manifold is frankly utter stupidity from the clowns and dive shops that sell you this stuff and the ignorant.

Of the line valves you suggest the Sherwood is a male/female line valve with or without an optional panel mounting nut. The direction of flow is in a female to male flow direction.

That ensures that the incoming pressure is always under the HP polymer seat and the control valve spindle is out of both the gas pressure and flow. I'm sure now you know the reason why a reverse flow direction is an error of stupidity only a prick would consider.

You only ever see line valves fitted back to front by the cheap clowns in our scuba industry as and I guess having to fit an additional $2 male x male nipple and female to tube adaptor adds a few dollars to cost.
The other give away of a clown at work is the lack of non return valves on the discharge dispensing lines. Others may disagree.

 

[stiebs]

Thanks for your response @iain/hsm, but you haven't answered my question.

I am not advocating fitting valves back to front, but merely asking about an observation.

Consider the following rudimentary cascade panel, of which I have seen many variations of in various installations.

The flow from the compressor is obviously only ever in one direction, but flow through the valves changes depending on whether the compressor is filling the tanks (manifold > bank) or whether gas is being decanted from the banks (bank > manifold).

In order to ensure single directional flow through the valves, there would need to be a separate path for each direction similar to the below. I don't typically see fill panels that have separate valves for filling banks and decanting from them.

 

[iain/hsm]

Thanks for your response @iain/hsm, but you haven't answered my question.

I am not advocating fitting valves back to front, but merely asking about an observation.

Consider the following rudimentary cascade panel, of which I have seen many variations of in various installations.

The flow from the compressor is obviously only ever in one direction, but flow through the valves changes depending on whether the compressor is filling the tanks (manifold > bank) or whether gas is being decanted from the banks (bank > manifold).


View attachment 904109


In order to ensure single directional flow through the valves, there would need to be a separate path for each direction similar to the below. I don't typically see fill panels that have separate valves for filling banks and decanting from them.

You don't see the set up above professionally. Although I have assumed all three are the Sherwood panel valves.

Now if two (2) were rising plug valves and a single line valve off the manifold block would be the sort of thing I would expect for the cheapest vendors in China for a scuba dive shed in Egypt. But as a customer I would tell them to stick it and find a proper supplier.

Enclosed below is a typical rising plug valve from Swagelok you can see the clear gas path and the valve spindle is sealed off from the gas medium. I will try and add a Sherwood line drawing for comparison.

 

[iain/hsm]

Here you go the data sheet on the Sherwood directional line valve for comparison.

 

[TravisD]

Disclaimer: I"m approaching this as a thought exercise - not as any sort of knowledgeable person in the matter.

Is the flow direction a function of where the pressure delta would be seen? If the high pressure is on the center of seat, it will be less likely to defom/leak past the edge of the seal. If any does leak past into the stem 'chamber' it would help seal the outgoing port.

So directional for at-rest/closed purposes, but not really a big deal for while gas is flowing?

 

[rjack321]

The sherwood valves work fine. I would suggest installing them so the gas flow direction is out when the bank is draining. So the gas is pressurizing the HP seat correctly when the valve is closed and the bank bottle is in "storage" mode which is the vast majority of the time.

And reversed for the low flow rate refilling times. This avoids the tiny stem oring being the only thing between your whole bank and the atmosphere when the bank is closed (assuming the individual bottle valves aren't also closed during storage)

 

[SpeedyJ]

You don't see the set up above professionally. Although I have assumed all three are the Sherwood panel valves.

Now if two (2) were rising plug valves and a single line valve off the manifold block would be the sort of thing I would expect for the cheapest vendors in China for a scuba dive shed in Egypt. But as a customer I would tell them to stick it and find a proper supplier.

Enclosed below is a typical rising plug valve from Swagelok you can see the clear gas path and the valve spindle is sealed off from the gas medium. I will try and add a Sherwood line drawing for comparison.

Being one of the ignorant - is a rising plug valve a better valve type to use where gas may be flowing two directions? Something else?

 

[stiebs]

Being one of the ignorant - is a rising plug valve a better valve type to use where gas may be flowing two directions? Something else?

A ball valve is a better option if fine flow control is not required, and I believe a rising plug valve the better option when fine flow control is required. However at scuba pressures, a Sherwood style panel valve is orders of magnitude cheaper than either of the other two options.