The pressure drop across a valve is related to the flow rate passing through it, i.e. the greater the flow rate the higher the pressure drop and the lower the flow rate the lower the pressure drop.
Manufacturers publish a Flow Coefficient value to allow the calculation of pressure drop based on flow rate.
For metric units, i.e. m3/hour and bar or l/s and kPa, the flow coefficient is Kv, whereas, for imperial units, i.e. gpm and PSI, it is Cv.
As l/s and kPa are most commonly used, we will concentrate on Kv and not Cv.
The formula for calculating pressure drop is: Δp = (36Q/Kv)2
Where:
Δp = pressure drop (kPa)
Q = flow rate (l/s)
Kv = flow coefficient (no units)
Example :
A flow rate of 0.225l/s passes through a D921 ¾” DRV (Double regulating Valve), calculate the pressure drop when the valve is fully open (FO).
Look up Kv value for ¾” D921 (Fully Open) (Check Manufacturers published Flow Coefficient value in Datasheet)
Kv = 3.61
Δp = (36 x Q / Kv)2
Δp = (36 x 0.225 /3.61)2
Δp = 2.2442
Δp = 5.035 kPa
Also Read: Valves Questions & Answers
Similar Articles:
- Summary of Valve Types Characteristics
- Valves Pressure Loss – Questions and Answers
- How Quick Opening, Linear & Equal Percentage Valve Characteristics Derived
- Basics of Butterfly Valves
- Calculate Flow Coefficient Kv of Solenoid Valve
- Swing Check Valves
- 5 Valve Manifold Operation
- Pneumatic Valves Questions & Answers
- Stop Check valve
- Piston Check Valve
1 comment
Excellent