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12
12
-5
Air Operated V
alve/Contr
ol V
alve
Air Operated Valve/Control Valve
Step
2
Nominal Size Selection for Air Operated Valve and Control Valve
Calculation formula for Cv value
Cv value table
Formula for correction of viscosity
(1) For steam
(2) For gas
(3) For liquid
W : Max. steam flow rate [kg/h]
P
1
: Inlet pressure [MPa
·
A]
P
2
: Outlet pressure [MPa
·
A]
ΔP : P
1
- P
2
[MPa]
k : 1 + 0.0013 x {superheated steam temp. [°C]
- saturated steam temp. [°C] }
Q : Max. gas flow rate [m
3
/h (standard condition)]
G : Specific gravity (relative to air for gas, or
relative to water for liquid)
t : Fluid temperature [°C]
V : Max. liquid flow rate [m
3
/h]
Cv : Cv value of each nominal size
Iv : Viscosity index
Mcst: Viscosity [cSt]
When
When
When
When
2
> P
1
2
P
Cv =
Wk
138 ΔP(P
1
+ P
2
)
2
P
1
2
P
Cv = Wk
120P
1
2
> P
1
2
P
(273 + t) G
Cv =
Q
2940 ΔP(P
1
+ P
2
)
2
P
1
2
P
2560P
1
Q
Cv =
(273 + t)G
Cv = 0.365V
G
ΔP
Iv = V
72780
Mcst
(
)
G
ΔP
1
4
1
2
Iv: Viscosity index
Viscosity correction curve
K: Cv correction coefficient
Nominal size
Model
10A
15A
20A
25A
32A
40A
50A
65A
80A
100A
PD-1, 2
5
7
11
16
24
40
PD-3
4
9.2
17.4
27.8
40.6
63.8
CT-1
6
9
14
25
33
50
85
106
175