33
Saunders diaphragm valves offer
excellent control capabilities within a
broad range of pressure, flow or level
control applications.
Rangeability (ratio of maximum flow vs. minimum
control flow) of Saunders weir type valves is 35:1
extending beyond the range of most process
and service control systems.
The positive shut-off characteristics of the valve
can, inmany instances, eliminate the need for
independent block valves, a major component in
the piping system cost.
The inherent flow characteristics illustrated
shows linearity up to 60% of travel (80% of flow).
The chart illustrates installed characteristics
affected by the dynamic friction loss for the
remainder of the piping system. Equal %
characteristics can be obtained through the
use of characterised positioners.
Pressure recovery factor = 0.7.
PneumaticValveActuation
Valve Throttling and FlowControl
100
90
80
70
60
50
40
30
20
10
0
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15
InstrumentSignalpsi
%MaximumFlow (Constant
∆
P)
100
90
80
70
60
50
40
30
20
10
0
0 10 20 30 40 50 60 70 80 90 100
PercentofRatedTravel
PercentofRatedFlow
QUICKOPENING
LINEAR
EQUALPERCENTAGE
100
90
80
70
60
50
40
30
20
10
0
0 10 20 30 40 50 60 70 80 90 100
SHUT
OPEN
PercentValveTravel
%MaximumFlow (Constant
∆
P)
ž
Actuator
with digital
foundation
fieldbus
positioner
% flow/% travel, weir
type diaphragm valve
Diaphragm valve
characteristic curves
Hysteresis for weir
type diaphragm valve
fittedwith actuator
plus valve positioner
