Signal Priorities; Detection Of Valve Seat - Siemens Acvatix SAX Series Basic Documentation

Examples
Example
Siemens
Building Technologies
4.8

Signal priorities

The actuators are controlled via different interlinked positioning signal paths
(positioning signal "Y", forced control input "Z", manual adjuster). The signal paths
are assigned the following priorities:
Priority
1 The manual adjuster always has priority 1, thus overriding all signals active at
(highest)
"Z" or "Y", independent of whether or not power is applied.
Only SA..61..: As soon as a valid positioning signal is active at input "Z", the
2 position is determined via positioning signal "Z" (forced control). Prerequisite:
The manual adjuster is not used.
3 The position is determined via positioning signal "Y". The manual adjuster is
(lowest)
not used and on Z there is no active signal.
Manual Forced
adjuster control (Z)
Automatic Not
mode connected
Automatic
G
mode
Automatic
G0
mode
Operated
(30%) and G
engaged
Bold printing = positioning signal currently active
4.9

Detection of valve seat

The actuators feature force-dependent valve seat detection. After calibration, the
exact valve stroke is filed in the actuator's memory. When the actuator reaches the
respective end of stroke, it does not hit the valve's seat at full speed, but stops for 5
seconds at about 1% before the stored position is reached. If the positioning signal
stays at 0% or 100%, the actuator travels to the calculated end position at reduced
positioning speed and builds up the required nominal force.
This function extends the actuator's service life since the dynamic forces are
reduced when approaching the valve seat and there will be less strain on the gear
train.
In addition, the actuator's oscillations in the case of instable control are
suppressed.
If no force is built up in the calculated end position (e.g. in the event of temperature
effects for instance), the actuator continues to operate at a reduced positioning
speed until the nominal positioning force is restored. This ensures that the valve
always fully closes.
After a power failure, valve seat identification is not active – the actuators define
their stroke position on power resoration to be at 50%. From now on, the actuator
follows the positioning signal.
When the valve plug reaches its seat for the first time, the actuator readjusts its
stroke model.
The supposed position is 50%, Y = 2 V, the actuator travels 30% of the stored
valve stroke in the direction of "Actuator's stem retracted".
If the actuator reaches the seat within this 30% travel, it interprets the position as
"Valve fully closed" and shifts the position of the valve's stroke accordingly without
changing the extent of travel.
From now on, the actuator follows the changed valve stroke position.
This means: New position 0%, Y = 2 V, actuator travels 20% of the stored valve
stroke in the direction "Actuator's stem extended".
Actuators SAX.., SAL.. for valves
Functions and control
Description
Positioning
Stroke actuator
signal (Y)
Actuator's stem travels to
5 V
position (50%)
3 V Actuator's stem extends
3 V Actuator's stem retracts
Actuator's stem retracts
8 V
manual (to 30%)
Z
Y
Rotary actuator
Actuator's spindle travels to
position (50%)
Actuator's spindle turns in
clockwise direction
Actuator's spindle turns in
counter-clockwise direction
Actuator's spindle turns
manual in counterclock-wise
direction (to 30%)
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CE1P4040en
22.12.2010