Know-how makes the difference
5
B-3500-UK-06-2013-REV. A
General Information
Bar (o)
Bar (o)
Control pressure
Differential pressure
Size of actuator
Valve size
50
8
6
4
2
8
4 8 12 16
DN25
DN20
DN15
DN10
The curves describe the relation between the differential pressure and the needed
minimum control pressure of the actuator.
On the chart shown above, which is for a single acting normally close execution where the
media enters above the seat, a DN25 valve equipped with a size 50 actuator needs a control
pressure of min. 3 bar(o) in order to open if the differential pressure is 4 bar(o). The same
execution needs a control pressure of 4.5 bar(o) in order to open if a differential pressure of
16 bar(o) is present.
Reading the charts:
When reading the charts one has to distinguish between handling a NC (normally close) or NO
(normally open) valve.
In case of a NC valve -
the curves for the valves describes the minimum control pressure to
open the valve at a certain differential pressure.
In case of a NO valve -
the curves for the valves describes the minimum control pressure to
close the valve at a certain differential pressure.
Warning
WARNING: Liquids with high flow velocity flowing from above the seat may cause water
hammering.
Flow comes from below the seat to avoid water hammer.
Graph description - how to read the graphs.
