Series
KNAR/F, KNARP/F, KNAR-D/F, KNARP-D/F,
Page
5
KNAR-S/F, KNARP-S/F
ASME
9520-032-en
Revision 15
TM 9549
Edition 11/2018
1.4 Actuating torques
Test medium: water 68 °F (20 °C)
Higher actuating torques may occur with other media.
DN
Δ
p in psi
≤
45
85
145
235
max. adm.
[inch] [in-lbs] [in-lbs] [in-lbs] [in-lbs]
[in-lbs]
½“
71 71 71
89
620
¾“
71 71 71
89
620
1“
106 106 106
106
620
1½“
177 177 177
221 1990
2“
221 221 221
266 1990
3“
531 531 575
708 4425
4“
708 708 797
1505 4425
6“
1770 2213 3098
-- 19470
8““
1770 2213 3098
-- 19913
1 in-lbs = 0.112 Nm
The actuating torque of the actuator must be at least
as high as the actuating torque of the valve, about
20% higher being better however.
With highly viscous media and/or solids in the medium
it may be necessary to consider other safety
allowances in dimensioning the actuator. This is
particularly true for non-Newtonian fluids such as high
polymer substances, suspensions, pastes, lubricants,
resins, lacquers etc.
Admissible factors of safety lie in the range of 20 -
50% of the actuating torque.
In order to avoid damage to the valve, it is imperative
to observe the max. admissible actuating torque!
1.5 Cavitation coefficient z for
75% duty (Cv/Cv
100
=0,75)
There are at least 3 different V-control ball/stem units
for each nominal size
DN
z1
z2
z3
z4
z5
z6
½“
0.65
0.60
0.60
0.60
0.58
0.43
¾“
0.65
0.60
0.60
0.60
0.58
0.43
1“
0.65
0.60
0.60
0.60
0.58
0.43
1½“
0.53
0.50
0.35
2“
0.47
0.39
0.32
3“
0.31
0.29
0.22
4“
0.27
0.24
0.16
6“
0.15
0.13
0.08
8“
0.15
0.13
0.08
𝑋
𝐹
=
∆𝑝
𝑝
1
− 𝑝
𝑣
X
F
= Differential pressure ratio
Δ
p = Differential pressure input/outlet
p
1
= Absolute pressure at inlet
p
v
= Vapour pressure at operating temp.
X
F
≤
z
: non-critical conditions
X
F
≤
1,4 x z : tolerable cavitation
X
F
> 1,4 x z : inadmissible cavitation
1.6 Flow values Cv in %
Opening
[%]
Cv
[%]
Characteristics
equal percentage
rangeability 25:1
Best control range
20-90% of angle of
opening
10
5.5
20
7.6
30
10.5
40
14.5
50
20.0
60
27.6
70
38.1
80
52.5
90
72.5
100
100.0
1.7 Flow rates
There are 3-6 different V-control ball/stem units per
nominal size
DN
Cv
[inch]
[USgpm]
½“
0.93 1.86 4.66
9.32
16.3
23.3
¾“
0.93 1.86 4.66
9.32
16.3
23.3
1“
0.93 1.86 4.66
9.32
16.3
23.3
1½“
18.64
29.12
46.6
2“
18.64 29.12
46.6
69.9
3“
46.6
93.2
139.8
186.4
4“
69.9
116.5
186.4
291.25
6“
186.4
291.25
466
8“/6“
186.4
291.25
466
8“
1165
