Datasheet

2.3 Flow coefficient Cv factor
The United States Standard ANSI/(NFPA)T3.21.3: 1990: Pneumatic fluid power—Flow rating test
procedure and reporting method-For fixed orifice components
Defines the flow coefficient, Cv factor by the following formula which is based on the test conducted by the
test circuit analogous to ISO 6358.
Q
Cv
=
…………………………………………………
(7)
ΔP (P2 + Pa)
114.5
T1
ΔP : Pressure drop between the static pressure tapping ports [bar]
P1 : Pressure of the upstream tapping port [bar gauge]
P2 : Pressure of the downstream tapping port [bar gauge]: P2 = P1 – ΔP
Q
: Flow rate [dm
3
/s standard condition]
Pa : Atmospheric pressure [bar absolute]
T1 : Upstream absolute temperature [K]
Test conditions are P1 + Pa = 6.5 ±0.2 bar absolute, T1 = 297 ±5 K, 0.07 bar ≤ ΔP ≤ 0.14 bar.
This is the same concept as effective area A which ISO 6358 stipulates as being applicable only when the
pressure drop is smaller than the upstream pressure and the compression of air does not become a problem.
3. Process fluid control equipment
(1) Conformed standard
IEC60534-2-3: 1997: Industrial-process control valves. Part 2: Flow capacity, Section Three-Test proce-
dures
JIS B 2005: 1995: How to test flow coefficient of a valve
Equipment standards: JIS B 8471: Solenoid valve for water
JIS B 8472: Solenoid valve for steam
JIS B 8473: Solenoid valve for fuel oil
(2) Definition of flow-rate characteristics
Av factor: Value of the clean water flow rate represented by m
3
/s which runs through a valve (equipment for
test) when the pressure differential is 1 Pa. It is calculated using the following formula.
Av = Q
………………………………………………………………….
(8)
Av : Flow coefficient [m
2
]
Q : Flow rate [m
3
/s]
ΔP : Pressure differential [Pa]

: Fluid density [kg/m
3
]
(3) Formula for flow rate
Described by the practical units. Also, the flow-rate characteristics are shown in Graph (2).
In the case of liquid:
ΔP
Q
= 1.9 x 10
6
Av
……………….………………………………………
(9)
G
Q
: Flow rate [L/min]
Av : Flow coefficient [m
2
]
ΔP : Pressure differential [MPa]
G : Specific gravity [water = 1]
In the case of saturated steam:
Q = 8.3 x 10
6
Av ΔP (P2 + 0.1)
……………………………….…………
(10)
Q : Flow rate [kg/h]
Av : Flow coefficient [m
2
]
ΔP : Pressure differential [MPa]
P1 : Upstream pressure [MPa]: ΔP = P1 − P2
P2 : Downstream pressure [MPa]

Δ
P
Solenoid Valve Flow-rate Characteristics
Series VX21/22/23
33