Pipeline ancillaries Ball valves
10
Sizing 1. Determine the required C V for the ball valve using the appropriate equation detailed below. With the first approximation for this calculation it is suggested to use a factor FL = 0.68, that corresponds to an opening of the valve of 72°. 2. Calculate the diameter of the pipe for maximum flow within the limits of velocity and pressure drop for the fluid. 3. With the C V and pipe diameter, use the table on page 4 starting with the column that corresponds to the rotation of 72°, that gives FL = 0.68. 4. In this column, choose the combination of ball valve diameter and pipe diameter that gives a Cv result the same or superior to the one calculated in step 1. 5. It is recommended not to use a ball valve with a diameter less than half the pipe diameter, because of excessive tension that can produce vibrations.
Simplified equations for sizing (K v values = C v x 0.86) For liquids Where: Pm = Maximum P for sizing, When P 2 > P V use Pm = F L 2 (P 1 - P V )
Sub-critical flow
Critical flow
When: P < Pm
When: P > Pm 2 When P When P 2
1 P use Pm= P - 0.96- 0.28 ≤ v P use Pm= P - 0.96- 0.28 ≤ v 1
T
P V P C
When P 2 > P V use Pm = P 1 - 2 1 When P ≤ v
P use Pm= P - 0.96- 0.28
P V
C V =
360 (P 1
2 - P
2 )pr
P V P C P r V P r
2
When
P
P use Pm= P - 0.96- 0.28
P V V
≤
C V =
p
v
2
1
p
2
1
= 1.16 = 1.16
C V
V
36
C V C v = Flow coeffecient of the valve F L = Pressure recovery factor pr = Density at inlet temperature (water = 1.0 at STP) p P = 1.16 r C V P 1 = Upstream pressure (bar a) P 2 = Downstream presure (bar a) P V = Vapour pressure of the liquid at inlet temperature (bar a) P C = Thermodynamic critical pressure (bar a) = Flowrate in m ³ /h = Flowrate in in kg/h F L p Pm r = 1.16 C V P = pr 865
C V
Volumetric flowrate
Volumetric flowrate
T 311F L P 1 pr p r r
C V =
1.16 1.16
p Pm r p Pm r
= 1.16
C V V
=
C V
C V
=
P
F L
C V =
F L
31
V
=
C V
1.16
p Pm
2 - P r r
13.81
P 1
2
=
C V V
2
C V
=
C V
=
F L L
C V =
865 865
P
pr
P
pr
13
V
Mass flowrate
Mass flowrate
=
C V
11.95
F L P 1
C V
=
C V V
=
C V
=
C V =
865 865
F L
pr
Pm Pm
865
P
pr
11
F L
pr
V
P 1 (1 + 0.00126 T SO ) 13.81 2 - P 2 2
C V
=
=
C V
865
F L
pr
Pm
C V V
=
C V =
p
T
r
865
F L L
pr
Pm
p
T
r
C V
V
=
C V
=
P 1
295 295
2 - P 2 - P
2
P 1
2
2
(1 + 0.00126 T SO ) 11.95 F L P 1
2
p
T
r
C V =
C V
=
P 1
295
2 - P
2
2
p
T
r
r
p F L P 1 r p F L P 1 r T T
C V =
C V V
=
=
C V
V
P 1 1
295
2 - P 2
2
=
C V
2
257 257
10.3 246
2
2
p F L P 1 r
T
=
C V
257
p F L P 1 r L 1 r T
=
C V V
257
TI-P133-47 CMGT Issue 2
Page 2 of 4
M45 ISO Ball Valve for Control of Fluids - Sizing Sheet
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