Pneumatic Clean Series

258Flow Characteristics of Solenoid Valve(How to Express Flow Characteristics)2-2 Effective sectional area S(1) Calculation with subsonic conductance C:S = 5.0 X C(2) Test methodPipe the test equipment to the test circuit shown in Figure 3.Fill the air tank with compressed air and keep the pressure ata constant level above 0.6MPa. Then discharge the air untilthe pressure in the tank drops to 0.25MPa. Measure the timerequired to discharge the air and the residual pressure in theair tank after leaving it until the pressure becomes stable inorder to calculate the effective sectional area S by thefollowing formula. Select the capacity of the air tankaccording to the effective sectional area of the testequipment.V Ps+0.1 293S =12.1—log 10 ( ———— ) ——t P+0.1 TS: Effective sectional area [mm 2 ]V: Air tank capacity [dm 3 ]t : Discharge time [s]Ps: Pressure in the air tank before discharge [MPa]P: Residual pressure in the air tank after discharge [MPa]T: Temperature in the air tank before discharge [K]2-3 Flow coefficient Cv factorThe flow coefficient Cv factor is defined with the followingformula in the U.S. standard ANSI/(NFPA)T3.21.3: 1990:Pneumatic fluid power - Flow rating test procedure andreporting method - For fixed orifice componentsQCv= ———————————P(P2+Pa)114.5 ——————T1P: Pressure drop between static pressure output ports [bar]P1: Pressure at ustream output port [bar gauge]P2: Pressure at downstream output port [bar gauge]: P2=P1– PQ: Flow rate [dm 3 /s standard atmosphere]Pa: Atmospheric pressure [bar absolute]T1: Upstream absolute temperature [K]Test conditions are P1+Pa=6.5±0.2 bar absolute, T1=297±5K,0.07bar≤P≤0.14 bar.This concept is similar to the effective area in ISO 6358,which is described to be applicable only if the pressure dropis so small compared with the upstream pressure that aircompression is negligible.Pressure controlequipmentAirsupplyFilterTemperaturegaugeShut-offvalvePressureswitchControlcircuitAir tankPressuregaugeor pressuretransducerTimer (watch)Pressure recorderPower supplySolenoidvalveTest equipmentUpstream Downstreamrectifier rectifiertube tubeDirectionalControl ValveFigure 3. Test circuit of JIS B 8390239