Channel-Related Parameters for the Valve Coupler Modes
2
0
1
8
-0
7
51
8.2
Modes of Operation
The Target Mode parameter determines the required mode of operation of the channel.
You can select one of the following modes.
8.2.1
Device Maintenance Modes
■
O/S (Out of Service):
In this mode, the channel is out of service. The valve output is
disabled so that the valve moves into the mechanical safety position. Use this mode in
either of the following cases:
•
Disable an unused channel.
•
Avoid unintended control of the valve during parameterization of a channel.
Otherwise the control value of the valve might be unintentionally modified by the
Actuator Fail Action or Invert Setpoint parameters.
■
Man (Manual):
In this mode, you can manually control a channel by acyclic data
exchange. You can use a configuration tool, e. g., a device type manager, for maintenance
and servicing functions.
8.2.2
Operating Modes
■
Auto (Automatic):
This is the standard mode of operation (default setting) for cyclic user
data exchange. The control system sets the valve setpoint value via the cyclic
communication variable SP_D. In case of a failure, the valve is set to the parameterized
fault state position specified by "fail-safe mode".
■
RCas (Remote Cascade):
This is a modified form of the Auto mode. This mode specifies
a certain behavior in a failure case. In a failure case, the channel changes over to the Auto
mode and returns to RCas only if requested by the master (control system). This way, it is
possible to prevent the channel from automatically restarting when the status of the
setpoint value changes from GOOD to BAD and back to GOOD.
8.2.3
Operating Mode "Auto" in Case of Fault
If the device is in the Auto mode, the setpoint value is specified via the variable SP_D, as long
as the related state is "good (NC)-OK". If the status changes to BAD, the valve is set to the fault
state position after a time, as defined in the Fail-Safe Time parameter.
If the fail-safe state is active, a bit is set in the variable CB_D.
The Fail-Safe Time parameter indicates the time interval, in seconds, between the occurrence
of the fault and the control of the valve into fault state position. The fault state position is
determined by the Fail-Safe Mode parameter.
The following fail-safe modes are selectable:
■
Mode
“
Keep the last position
”
: last valid setpoint value.
■
Mode
“
Move into the mechanical safety position
”
, specified by Actuator Fail Action
parameter. The mechanical fail–safe position is always reached by switching the valve off.
■
Mode
“
Set position
”
specified by "fail-safe default value". The "fail-safe default value" can
be set to OPEN or CLOSED.
Example!
Example 3: "Invert Setpoint" is ON
■
The Actuator Fail Action parameter is set to "closed".
■
The actuator moves into the closed position ("closed"), when the current of the auxiliary
valve is OFF.
■
If the setpoint value is "0" ("open"), the auxiliary valve is triggered.
=> In this case, "0" means "current ON".
