Check valve head loss
Check valve head loss
(OP)
Hi,
Can anyone confirm this to me please.
Does a check valve has a different had loss value, if it's installed in a vertical or horizontal pipe?
Thanks
Can anyone confirm this to me please.
Does a check valve has a different had loss value, if it's installed in a vertical or horizontal pipe?
Thanks





RE: Check valve head loss
It depends on the style of the check valve.
There are check valves that will not operate in a vertical or horizontal position ("flapper check and ball check).
What is "a different had loss value"...???
-MJC
RE: Check valve head loss
I mean head loss (pressure loss) in the check valve.
I ask this, because my idea is that if we have a check valve vertically, it has an upper resistance due to the water weight, that hasn't when is installed horizontally.
Am i correct?
RE: Check valve head loss
"If everything seems under control, you're just not moving fast enough."
- Mario Andretti- When asked about transient hydraulics
http://virtualpipeline.spaces.msn.com
RE: Check valve head loss
RE: Check valve head loss
P = rho*g*h
rho is mass density, g is accel. due to gravity, and h is the vertical height difference. P then is the pressure differential between two points seperated by vertical distance h.
RE: Check valve head loss
Flow_GPM / Cv_GPM/psi^(1/2) = (diff_Press_psi)^(1/2)
"If everything seems under control, you're just not moving fast enough."
- Mario Andretti- When asked about transient hydraulics
http://virtualpipeline.spaces.msn.com
RE: Check valve head loss
RE: Check valve head loss
Caution units of Cv may vary.
"If everything seems under control, you're just not moving fast enough."
- Mario Andretti- When asked about transient hydraulics
http://virtualpipeline.spaces.msn.com
RE: Check valve head loss
I'm a bit confused about the answers. Normally i use the formula that i use with any local loss, wich includes that Cv factor that BingInch mentioned.
My doubt, and that was yet clarified, is related to this factor. Does it change if we consider vertical or horizontal pipe? (knowing that the rest of the formula stays the same: velocity,etc)
Thanks
RE: Check valve head loss
So use the formula above for frictional head or pressure loss, being sure that your known inlet or outlet pressure includes that due to elevation considerations, as it should, then the total pressure drop across the valve will be the sum of that calculated by Cv formula plus or minus the fluid density x valve length x sin(alpha), where alpha = angle that the valve makes with the horizontal plane.
"If everything seems under control, you're just not moving fast enough."
- Mario Andretti- When asked about transient hydraulics
http://virtualpipeline.spaces.msn.com
RE: Check valve head loss
Now i understood perfectly what you said!
One last thing: isn't this elevation loss consideration included in the total height elevation between the lower and upper point of the pipe, used to calculate also the pump head needed?
Thanks once more
RE: Check valve head loss
Generally you can assume the valve is a point, without any length and calculate the pressure due to elevation change and frictional loss up to that point, then apply the Cv friction loss equation to get the pressure drop across the valve, and lastly, calculate the unknown pressure on the other side of the valve.
I can imagine some special type of flow element where the point assumption might not be true, a very very long valve for example, but that's stretching it pretty far outside the customary problem.
"If everything seems under control, you're just not moving fast enough."
- Mario Andretti- When asked about transient hydraulics
http://virtualpipeline.spaces.msn.com
RE: Check valve head loss
RE: Check valve head loss
Please start a new thread.
"If everything seems under control, you're just not moving fast enough."
- Mario Andretti- When asked about transient hydraulics
http://virtualpipeline.spaces.msn.com
RE: Check valve head loss
If the check valve poppet is big and heavy, as it might be for a very large valve, then the weight of the poppet may change the restoring force, and affect the Cv of the valve slightly, at pressure drops near the cracking pressure of the valve. I.e. until the poppet has moved from its seated position to its full-open position, the Cv of the opening is dictated by the balance of spring, gravity, and fluid dynamic (e.g. drag) forces.
RE: Check valve head loss
"If everything seems under control, you're just not moving fast enough."
- Mario Andretti- When asked about transient hydraulics
http://virtualpipeline.spaces.msn.com
RE: Check valve head loss
"If everything seems under control, you're just not moving fast enough."
- Mario Andretti- When asked about transient hydraulics
http://virtualpipeline.spaces.msn.com