How about some physics talk? mechanical engineering?

[derekcw83]

If I'm using a manifold in my keezer to gas up 5 kegs, please explain how gas (oxygen) can't get from one keg to another?

I get it that most manifolds are made with ball check valves, however how does the ball check valve really operate? Under equilibrium pressure from the keg side and the tank side, is the valve really closing if it isn't spring loaded?

Or are most manifold ball check valves spring loaded??

 

[GilaMinumBeer]

When there is flow in the operating direction the ball moves to an open position. If the flow reverses the ball shifts backwards against a seal and the valve is closed. Check valves a.k.a. Backflow Preventer.

 

[derekcw83]

So if there is no flow (equilibrium) then the ball stays open?

 

[GilaMinumBeer]

So if there is no flow (equilibrium) then the ball stays open?

Not entirely sure there. I expect it just stays in whichever position it is in unless flow changes it's position.

 

[day_trippr]

Check valves typically found inside gas shutoffs are spring loaded balls in a tight race with a mating seat at the "closed" end.
When there is insufficient flow to displace the spring-loaded ball, the path remains closed.

I've found the springs typically require around .5 psi minimum to overcome, but have found check valves that need almost a full psi to open.
This can actually matter: I have a fixed 11" WC regulator for use when cold-crashing my carboys, and it feeds my two ferm fridges through a pair of four port manifolds with integrated checks. I had to remove the checks from two of the ports on each manifold because the springs were too stiff to pass ~.4 psi...

Cheers!

 

[jmcquesten]

I switched to just check valves. I got some decent ones like these because I was convinced that the cheap shutoff/check valves were junk and leaked. Since I've switched, my co2 tank hasn't budged. I don't know if these are the exact ones I got, they are at least similar. The have a very low crack pressure (like can be opened by blowing through).


https://m.ebay.com/itm/Circle-Seal-...347032?hash=item43f8e1a818:g:rl0AAOSwo4pYI2ZN

 

[day_trippr]

I have five regulators and a 6 way and three 4 way manifolds in service, totalling 23 shut-offs, all (except for the previously noted four) with integrated check valves. When new all were cleaned and dunk tested with all of the permanent plumbing connected save for the permanent feed lines. Never found any valves that leaked. Manifolds, plugs, swivels and QDs, yes - I had all kinds of leaks that if not detected then would have haunted me forever. But never the valves themselves.

So I haven't run into any, but I've certainly read of folks experiences with shut-off valves that leaked around the stem packing.
I expect there's a cost threshold below which valve quality rapidly falls off.
Some things don't pay to go cheap, and imo a shut-off valve is one of those....

Cheers!