EB 8389-1S EN
37
On/off valve
5
On/off valve
The travel range of open/close (on/off) is
defined by the fail-safe position and the op
-
erating point. As a result, the following pa-
rameters to determine the working range
and set point range are not analyzed and
cannot be changed.
−
Lower travel/angle range value
−
Upper travel/angle range value
−
Lower travel/angle limit
−
Upper limit for travel/angle
−
Lower set point range value
−
Upper set point range value
The discrete analysis of the reference vari-
able is performed in automatic mode.
If the set point ( ) is below 'Operating point
limit' when the automatic mode starts, the
valve ( ) moves to the fail-safe position.
If
the set point increases and exceeds 'Operat
-
ing point limit', the valve moves to the 'Op
-
erating point'. The valve moves back to the
fail-safe position (0 % in the example) if the
set point then falls below 'Fail-safe action
limit'.
Operating point
Operating point limit
Fail-safe action limit
Fail-safe position
t [s]
25
50
∆
t > 6 s
x [%]
w [%]
If the set point ( ) is above 'Operating
point limit' when the automatic mode
starts, the valve ( ) moves to the operating
point.
The valve moves back to the fail-safe
position (0 % in the example) if the set point
then falls below 'Fail-safe action limit'.
Operating point
Operating point limit
Fail-safe action limit
Fail-safe position
t < 6 s
t [s]
25
50
x [%]
w [%]
Starting the partial stroke test (PST)
A partial stroke test is started when the set
point ( ) moves in the range between 25
and 50 % of the travel range and remains
there for longer than six seconds. See
u
Operating point =
Lower range value (PST)
Fail-safe action limit
Fail-safe position
Upper range value (PST)
Operating point limit
Stop PST
Start PST
> 6 s
t [s]
x [%]
w [%]
t
25
50