5-5-12 - 5
Wanted:
Presetting for a 1” valve at a desired flow rate of 6.7 GPM and a pressure drop of 3 ft.
Solution:
Draw a straight line joining 6.7 GPM and 3 ft. This gives Cv=5.9. Now draw a horizontal line from Cv=5.9.
This intersects the bar for a 1” valve at the desired pre-setting of 2.35.
NOTE:
If the flow rate is out of the scale in the diagram, the reading can be made as follows: Starting with the example above, we get 3
ft., Cv=5.9 and flow-rate 6.7 GPM. At 3 ft. and Cv=0,59 we get the flow-rate 0,67 GPM, and at Cv=59, we get 67 GPM. That is, for
a given pressure drop, it is possible to read 10 times or 0.1 times the flow and Cv-values.
Diagram 1/2” - 2”
