1.16
p Pm r
p
r
C V
=
= 1.16
C V
F L Pipeline ancillaries Ball valves
C V = 10
P
31
Simplified equations for sizing (K v values = C v x 0.86)
1.16
p Pm r
C V
=
C V
=
F L
865
P
pr
C V =
13
For steam and gases
Sub-critical flow
Critical flow
Where:
C V
=
C V
=
C V =
865
F L
pr
Pm
C V = Flow coeffecient of the valve F L = Pressure recovery factor pr = Specific density of gas (air = 1)
865
P
pr
11
When: P < 0.5 F L
When: P > 0.5 F L
2 P
2 P
1
1
C V
=
p
T
r
C V =
865
F L
pr
Pm
C V
=
P 1 = Upstream pressure (bar a) P 2 = Downstream presure (bar a) T = Inlet temperature in °K (°C + 273) = Flowrate of gas in Nm³/h (at 15°C and 1 bar a) = Flowrate of gas in in kg/h T SO = Superheating of steam in °C 2 When P ≤ v 2 1 When P V P P use Pm= P - 0.96- 0.28 ≤ v 2 When P ≤ v 2 1 When P V P P use Pm= P - 0.96- 0.28 ≤ v P C 2 When P ≤ v C V p = 1.16 r
P 1
295
2 - P
2
For gases (volumetric flowrate)
For gases (volumetric flowrate) 2
T
P V P C P V P C
P use Pm= P - 0.96- 0.28
P V
C V =
1
360 (P 1
2 - P
2 )pr
p
T
r
p F L P 1 r
T
2
C V =
C V
=
T
C V C V = = C V = C V =
P 1 P V P C
295 P use Pm= P - 0.96- 0.28 P use Pm= P - 0.96- 0.28 1
2 - P
257
2 P V
2
360 (P 1 360 (P 1
T 2 - P
2 )pr
2
P V
T
1
P V P V
C V =
2 - P
2 )pr
T 311F L P 1 pr T 311F L P 1 pr T 311F L P 1 pr 13.81 P 1 2 - P
2
C V For gases (mass flowrate) p F L P 1 r T 360 (P 1 = 257 360 (P 1
T 2 - P
2 )pr
For gases (mass flowrate)
2
P V P C P r P P C r p p
2 - P
2 )pr
C V = C V = C V T (Temperature of superheated steam - Temperature of saturated steam) S = Flowrate of steam in kg/h 2 Note: These equations are only a simplified version of the original sizing equations of the ISA and IEC regulations. The results are sufficiently close for practical use. There could be a maximum error of 8% in the transition of non-choked flowrate to choked flowrate. 360 (P 1 360 (P 1 2 - P 2 - P P 2 2 )pr 2 )pr T r P 2 = 1.16 P 1 When C V P use Pm= P - 0.96- 0.28 P V ≤ v p = 1.16 r C V = 1.16 = 1.16 1.16 C V F L p Pm r = 1.16 F L p = 1.16 1.16 F L 1.16 C V C V p Pm r = 1.16 p r = C V F L p Pm r = C V P = pr 865 P
2
C V =
T
C V = C V = C V =
C V = =
360 (P 1 T 311F L P 1 pr 2 - P T 311F L P 1 pr T 311F L P 1 pr 13.81
C V
P V P C
2 )pr
P V P C
P V
2
2
8
P V
2
=
C V
13.81 13.81 11.95 11.95 11.95
P 1
2 - P
2
p Pm r p Pm r p Pm r pr
2
For saturated steam
C V V = For saturated steam =
C V C V C V
T
F
P 1 L P 1
2 - P
C V = C V =
2
2
P 1 P 1
2 - P
2
T 311F L P 1 pr F L
60 (P 1
2 - P 2
2 )pr 2
=
T 311F L P 1 pr
2
C V
=
C V = C V =
2
C V
=
1
2
C V
=
865 865
P
pr
F L P 1
13.81
2 - P
2
F L P 1 (1 + 0.00126 T SO ) 13.81 P 1 (1 + 0.00126 T SO ) 13.81 P 1 (1 + 0.00126 T SO ) 13.81 2 - P (1 + 0.00126 T SO ) 11.95 F L P 1 2 2 (1 + 0.00126 T SO ) 11.95 F L P 1 (1 + 0.00126 T SO ) 11.95 F L P 1 2 - P 2 2 P 1 2 - P 2 2
2
C V V
=
=
C V
=
C V
1.16
P pr F L
pr Pm
C V C V C V C V C V C V
= =
= = =
C V C V C V C V C V C V
865
P
13.81 11.95 11.95
P 1 F L P 1 F L P 1
F L
T 11F L P 1 pr L 1
=
2 - P
C V
=
2
2 For superheated steam
For superheated steam
=
C V
C V
=
865
2 - P 2 - P pr P
865
F L
pr
Pm
=
C V
13.81 13.81
P 1
2
P 1
2
C V
=
2
F L P 1 (1 + 0.00126 T SO ) 13.81 P 1 (1 + 0.00126 T SO ) 13.81 (1 + 0.00126 T SO ) 11.95 F L P 1 2 - P 11.95 F L P 1 2 2 (1 + 0.00126 T SO ) 11.95 F L P 1 P 1 P 1 2 - P 2 2 2 - P (1 + 0.00126 T SO ) 13.81 2 2
2
=
C V C V =
865
F L
pr
Pm
= = =
p
T
r
= = =
865
F L
pr
Pm
C V
=
P 1
295
2 - P
2
865
P
pr
11.95
2
=
C V
11.95 11.95 865
pr
Pm
=
C V
F L P 1 F L P 1 L
p
T
r
C V =
3.81
P 1 1
2 - P 2
2
C V
2
=
2
2
P 1
295
p 2 - P T
2
r T
2
C V =
P 1 p F L P 1 p F L P 1 r r
C V
C V C V C V
= =
7.3.110
=
p
T
r
=
C V
295
2 - P
=
C V
2
P 1 (1 + 0.00126 T SO ) 13.81 (1 + 0.00126 T SO ) 13.81 2 - P 2 - P 2 2 P 1 2 2 pr 2 - P F L Pm 865 p P 1 P 1 2 - P 2 2 T 295 r 2 2 295 (1 + 0.00126 T SO ) 11.95 F L P 1 (1 + 0.00126 T SO ) 11.95 F L P 1 P 1 2 - P 2 2 p F L P 1 T r p p F L P 1 r T 295 257 257 r T
257
2
=
C V
=
C V
F L P 1 1.95 L 1
C V =
T
=
=
C V
257
p F L P 1 r
T
=
C V
257
P 1 2 (1 + 0.00126 T SO ) 13.81 2 - P 2 2 2 )
C V =
= = =
C V V
C V = C V = C V
1
2
p F L P 1 r
T
(1 + 0.00126 T SO ) 11.95 F L P 1 )
=
C V
257
L 1
10.3 95
TI-P133-46 CMGT Issue 2
Page 3 of 4
M15 ISO Ball Valve for Control of Fluids - Sizing Sheet
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