BRONKHORST HIGH-TECH B.V.
page 18
9.17.044
4.4.2 Bellows
valve
These valves are suited for low pressure or vacuum applications. The user should not disassemble this
model.
4.5 K
v
-value calculation
This calculation method can be used to determine the K
v
-value of the main orifice of a control valve.
Determine desired
∆
p across valve.
∆
p must be at least 50% of supply pressure
Kv-value
calculation
1000
p
K
m
v
⋅
∆
Φ
=
ρ
ρ
Units:
flow
-
)
/h
(kg
m
Φ
density
-
ρ
(kg / m ) at 20 C
3
o
and 1 atm.
delta p
-
∆
p(bard)
The orifice bore diameter can be determined by:
d
7.6 K
v
=
[mm]
For C2 type of valves the diameter of the orifice can be calculated as shown above or looked up in the graph
below.
Φ
Φ
v
2
v
2
H O =
customer
customer
H O
ρ
ρ
in which:
Φ
v
= volume flow
ρ
=
density
10
4
10
3
10
1
10
-1
10
1
10
0
10
4
10
3
10
2
10
1
P (bar)
d = 0.1 mm
d = 0.37 mm
d = 0.3 mm
d = 0.2 mm
d = 0.14 mm
10
2
10
0
10
-2
O
H O (ml/h)
2
10
-1
10
1
10
0
d = 1.0 mm d = 0.7 m m
d = 0.5 mm
P m ax.
v
If liquids have viscosity’s >15 cs (water = 1 cs), the flat orifice and plunger type control mechanism cannot be
used. For measuring systems only check maximum possible viscosity with factory.
4.6 Calibration
procedure
All instruments are factory calibrated. For re-calibration or re-ranging contact supplier or factory.
