Know-how makes the difference
9
An
Company
B-V-NOTCH-UK-02-2014 REV. C
V-NOTCH BALL - FINDING YOUR FLOW COEFFICIENT
TABLE 1
% OF VALVE ROTATION
0
10
20
30
40
50
60
70
80
90
100
V
30,60,90
Equal %
F
L
0.00
0.96
0.95
0.94
0.93
0.92
0.90
0.88
0.86
0.82
0.75
X
T
0.00
0.72
0.65
0.60
0.54
0.48
0.42
0.36
0.28
0.16
0.12
TABLE 2
P
v
Liquid
Formula
P
v
Acetone
C
2
H
4
47.861
Acetic Acid
C
2
H
4
O
2
0.0273
Ammonia
NH
3
0.7310
Benzene
C
6
H
6
0.1621
Butane
C
4
H
10
2.890
Carbon Dioxide
CO
2
58.420
Ethene
C
2
H
6
47.861
Ethanol
C
2
H
6
O
0.1029
Ethylene Glycol
C
2
H
4
(OH)
2
69.58
-6
Glycerin
C
3
H
5
(OH)
3
110.50
-6
Nitrogen
-
0.988
OIL WT32
-
205.48
-6
OIL WT64
-
306.59
-6
Sulfur Dioxide
SO
2
3.3929
Water
H
2
O
0.0238
TABLE 3
Gas gravity and heatfactor
Gas
Formula
G
g
F
k
Air
-
1.00
1.00
Ammonia
NH
3
0.59
0.92
Argon
Ar
1.38
1.19
Carbon Dioxide
CO
2
1.52
0.91
Carbon Monoxide
CO
0.97
1.01
Ethylene
C
2
H
4
0.97
0.87
Chlorine
Cl
2
2.49
0.96
Ethene
C
2
H
8
1.50
0.87
Helium
He
0.14
1.19
Hydrogen
H
2
0.07
1.00
Methane
CH
4
0.55
0.90
Oxygen
O
2
1.10
1.00
Nitrogen
N
2
0.97
1.00
Saturated steam
H
2
O
-
0.94
Superheated steam
H
2
O
-
0.94
Valve sizing info:
Recovery factor
“F
L
”
The recovery factor of a valve
only depends on the shape of the
body and the trim. The increase in
fluid static pressure that occurs as
fluid moves trough a valve from
the vena contracta (restriction) to
the valve outlet and downstream
piping. The F
L
coefficient is crucial
when approaching to cavitation,
which can be avoided selecting a
valve size with lower recovery fac-
tor.
The recovery factor does not occur
in sizing equations for compress-
ible fluids. Its use is unsuitable for
gas and vaporous medias.
Pressure drop ratio factor
“X
T
”
The X
T
factor is used for gas and
vaporous medias to describe the
point of chritical or maximum flow
through the valve.
V-notch flow control valves from
DVC are not designed to operate
under “critical” conditions. Please
avoid such selections when
dimensioning the size.
Abrasive media
DVC does not recommend the
use of V-notch control valve for
abrasive medias. If used for such
application please expect a signifi-
cant shorter lifespan of seats. Also
the ball surface may be damaged.
Please consult DVC if in doubt.
Flow Equation
K
V
Valve flow coefficient (m
3
/h)
Fluid
Service
Condition
Equation
F
L
Liquid pressure recovery factor of a valve without
attached fittings (dimensionless) – Refer to Table 1
G
L
Liquid specific gravity (1.0 for water at 15
o
C)
Liquid
Sub-chritical
condition
�� � �
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�
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�
��
P
1
Upstream absolute static pressure (kgf/cm
2
A)
�
�
��
�
�
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�
P
2
Downtream absolute static pressure (kgf/cm
2
A)
P
V
Absolute vapour pressure of liquid at inlet temperature
(kgf/cm
2
A) – Refers to Table 2
Chritical
condition
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�
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�
P
Differential pressure (P
1
– P
2
) (kgf/cm
2
A)
Q
L
Volumetric flow rate of liquid (m
3
/h)
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W
L
Weight or mass flow rate of liquid (t/h)
Gas
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G
g
Gas specific gravity – Refers to Table 3
Q
g
Volumetric flow rate of gas (m
3
/h)
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X
Ratio of pressure drop
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X
T
Pressure drop ratio factor (dimensionless) – Refer to
Table 1
�
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�
W
g
Gas or steam mass flow rate (kg/h)
Saturated
Steam
�� ���
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� �√�
1
Specific gravity, upstream conditions (kg/m
3
)
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F
K
Ratio of specific heat factors – Refer to Table 3
Super-
heated
Steam
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Y
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�
T
1
Absolut upstream temperature (
o
K)
�� ���
�
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�
�
�
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�
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�� � �
�
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�
t
Upstream superheated steam temperature (
o
C)
Z
Compressibility factor, dimensionless = 1
