What is the Difference betweem Cv and CFM in Air flow?

Question

I have two solenoid air valves. One has a Cv value for flow and other CFM value. Are they related somehow?

Answer 1

The manufacturer publishing a Cv valve for his valve requires a minimum pressure for the thing to operate. If you dont have enough pressure to overcome the pressure drop across the valve, it wont do what its supposed to do.

The other manufacturer requires a minimum volume of air to work. Without enough air flow, this valve wont do what its supposed to do. My guess is that either valve will work providing you have 90-125 psi air pressure available and sufficient flow capacity as stated on the valve.

Answer 2

The .Cv is the coefficient of flow rating for the valve. This is a calculation of flow at a given PSI through an orifice of a fixed diameter. Usually this rating is given at max operating pressure. The CFM rating is a bad way of sizing valves. A .Cv rating is using SCFM(volume and time) pressure drop through the valve to determine a minimum orifice size. See below.

1. Force/PSIG= Theoretical Area
2. Theoretical Area x 1.25=Area + Safety Factor
3. Square Root of Area/.7854=Bore
4. Pick Bore from that number
5. Area = Bore Squared x .7854
6. Volume= Area x Stroke
7. Delta P = PSIG x .10
8. PSIG2= PSIG – Delta P
9. CF = PSIG + 14.7/14.7
10. SCFM= Volume x CF / Time x 28.8
11. CV = SCFM x 1.024 / Square Root of Delta P x (PSIG2+14.7)

Answer 3

Cv is the valve coefficient and is related the amount of pressure drop that occurs across the valve. The lower the Cv, the more pressure drop occurs for a given flowrate, and therefore the lower flow you can get through it. CFM is the actual flow rate (Cubic Feet per Minute) of air.

The relationship is Q=1360 * Cv * (DP * P1 / SG * T)^0.5 where:
Q=Flowrate (SCFH, std cubic feet per hour)
1360=conversion constant for the given units
Cv= valve coefficient
DP = pressure drop (psi)
P1=upstream pressure (psi)
SG=specific gravity (air = 1)
T=temperature (Rankine)

Of course, it's always easier when comparing two things to have the same unit of comparison. Here's an online calculator for Cv that I've found helpful
http://www.a-tcontrols.com/products/valve_sizing/

Answer 4

As I see it, in case you have 2 instruments pushing out say 60 lbs squareinch into the comparable line you nevertheless basically have 60 lbs squareinch, yet you have got a much better delivery quantity. So relatively it relatively isn't the respond on your situation. you go with a bigger compressor with storage tank.

Answer 5

they are both solenoid air waves and they sharethe same first letter...
blue pill or red pill...