Pressure Drop at Pipe Junction

[mjpetrag]

I calculated the line resistance and matched the system curve with the pump curve, but I found a mysterious 20 psig drop in the system that cannot locate. I'm guessing it is at the junction with the other pipe the line discharges into but I can't find a good equation to calculate the drop.

The line looks like this

-------------------------------> 8", Pstat = 32 psig, 5 ft/s, water
^
|
|
|
3", Pstat = 24 psig, 5 ft/s, water, Velocity pressure ~ 26 psig

Can this junction create a 20 psig resistance in the 3" line? The 3" line comes into the 8" line at a right angle.

-Mike

 

[rneill]

Physically what was used for the junction between the 3" and 8" lines? Was it a reducing tee,an O-Let type connection, or a fabricated stub in connection?

The pressure drop seems high for a tee or stub in connection but if the cut-out on an O-Let was much smaller than the nominal 3" size (which is not uncommon) then that might be a possible source of the problem.

 

[mjpetrag]

well just found out the problem was a broken check valve, which failed the same time last year...

thanks for the responses

-Mike

 

[itsmoked]

Can you describe how it broke to cause the restriction?

Keith Cress
kcress -

http://www.flaminsystems.com