∆ p

Kv values GEMÜ 674, GEMÜ 675, GEMÜ 620

Measurement order and Kv value determination based on EN 60534

Medium: WaterTesting order according to the schematic diagram below: SCHEMATIC DIAGRAM Kv measurement section:
Pk p1 Test piece p2 Volume and airaccumulatorVolume flow measurement device Vol. flow in m³/h V1V2 Kv value calculation:Kv = volume flow x √ (1 / ∆ p) ∆ p = pressure difference p1 - p2 (inlet pressure minus outlet pressure) Kv value definition: The Kv value is the flow coefficient of valves based on water, in m3/h, with a pressure differentialof 1 bar at the valve. Cv value definition: The Cv value is the flow coefficient of valves based on water, in gallons per minute, with a pressure differential of 1 psi at the valve.For US gallons:(Kv) 1 m³/h = 1.1576gal/min as a Cv value For UK gallons :(Kv) 1 m³/h = 0.9639gal/min as a Cv value Definition of valve stroke: 100 % stroke means: Valve in "OPEN" position Resistance correction value The resistance correction value z (zeta) can be calculated using the connection diameter z (zeta):

or inner pipe diameter

z = 0.0016 x D4 / Kv²Kv value in m³/hPipe diameter D in mm
Qualitative Kv value diagram 10080 60 40 200 Kv value in % Valve body GG 25 (cast iron)Valve body GGG 40.3 (S.G.iron) with plastic linerThe diagram shown is an approximation of the course of the Kv valuecurves. Dependent on the valve body, nominal size, diaphragm, valve stroke and working pressure, the curves may differ. Opening stroke in %0102030405060708090100 26 Industrial valves I Kv values