2
0
1
8
-0
7
52
Channel-Related Parameters for the Valve Coupler Modes
Conditions when the fail-safe handling is stipulated:
■
Status change to "GOOD (NC)-IFS" status. The fail-safe time is not awaited.
The safe position is approached immediately.
■
The status of the specified setpoint value is BAD.
If communication is aborted with the DP watchdog activated, the status automatically
changes to BAD.
■
The device is switched ON.
The fault state position is left, as soon as the conditions for approaching the fault state
position have ceased to exist.
This is the case if the control system has reset the status of the specified setpoint value to
"GOOD (NC)-OK".
8.2.4
Operating Mode "Remote-Cascade (RCas)"
The RCas mode is used to prevent the channel from automatically restarting when switching
ON the device or when the status of the setpoint value has become BAD. The setpoint value is
specified via the variable RIN_D.
In the Auto mode, a valve connected to the valve coupler leaves the fault state position and
follows the setpoint value, as soon as the condition for approaching the fault state position has
ceased to exist.
In the RCas mode, the channel can change to another than the specified operating mode. This
state is called "actual mode". If the status of the setpoint value RIN_D is BAD for a longer
period than the "fail-safe time", the actual mode changes to Auto. In this case, the channel
behaves as described in see chapter 8.2.3.
Thus, an alternative setpoint value specification via SP_D can take place if the status of SP_D
is "GOOD (NC)-OK". If the status of SP_D is BAD, the valve is set to the fault state position. In
this case, it is not necessary to wait for the fail-safe time again.
Changing back into the RCas operating mode takes place only after a handshake via the status
values of RIN_D and ROUT_D.
When changing the actual operating mode to Auto, the status of ROUT_D changes to "GOOD
(C)-IR" at the same time, in order to indicate that the actual mode does not correspond to the
target mode.
The status "GOOD (C)-IR" of ROUT_D must be acknowledged by the status "GOOD (C)-IA" to
RIN_D. Next, the channel changes over back to RCas and the status of ROUT_D is set to
"GOOD (C)-OK".
In case of abortion and restart of communication, the also set the status of RIN_D to "GOOD
(C)-OK". This prevents the channel to change over immediately to RCas via the status "GOOD
(C)-IA".
8.3
Functional Parameters
This section describes the channel-related functional parameters.
8.3.1
Actuator Fail Action
The Actuator Fail Action parameter defines the fail-safe handling of the valve.
The following values can be selected:
■
Open, valve is self-opening when not activated.
■
Close, valve is self-closing when not activated.
Ensure that you take the entire signal chain into account, e. g., including a pilot valve and the
final control element.
If the initialization run is used, setting this parameter is not required.
For more information on the initialization run, see chapter 6.4 and in the DTM, see chapter
10.4.6.
