Index 54 Slow Mode Range
This parameter is currently only applicable to IQT actuators. The Slow Mode Range sets the deviation
between the set-point and current position in positioning mode inside which the actuator motor will
slow to minimum speed.
If the set-point (DV) is 50% and the setting for this parameter is 10%, then when the actuator moves
within the range 40% to 60% the motor will adopt low speed. The actuator does not use slow mode for
digital (Open/Close) commands.
Index 55 MIT (Motion inhibit timer)
The Motion Inhibit Timer setting is the period that must elapse between consecutive starts of the
actuator motor when in positioning mode. The idle period can be used to prevent the actuator motor
from exceeding its rated number of starts per hour. In addition, when tuning the valve positioner, the
setting can be used to allow the plant dynamics to stabilise between valve movements.
Index 56 to 58 Comms Failure – Action on loss of signal
This is a Rotork feature that is common for all our network products. The feature is used to enable the
user to set a position to which the actuator is required to go or to take no action at all if the FF CP card
loses communication with the network. If enabled, a timer is used to determine how long the actuator
should wait before carrying out the pre-set action:
• Communications Lost Action (56)
The Action on Loss of Comms parameter defines the actuator action
that will result after the time set for the Comms Fault Timer (parameter
58) if there is no network communication activity detected by the FF
CP card.
• Communications Lost Position (57)
The setting in this parameter determines the position in the range 0 to
100% that the actuator will move to if the FF card’s communications
stop being received, provided the Action on Loss of Comms
(parameter 56) is set to 'Position'. No action will be taken unless the
communications stop for a period equal to or greater than the setting
in the Comms Fault Timer (parameter 58).
• Communications Fault Timer (58)
The Comms Fault Timer setting determines the number of seconds
that the FF card’s communication must be absent for before the
setting for the Fault Mode will be carried out.
Note:
Parameters 56 to 58 relate to how the actuator’s control / main PCB responds to a loss of
comms. With FF there is also the ability to set a comms fail response on the output blocks of
the FF card itself. This is the “Fault state to value”. If this is selected, and the fieldbus block
goes into “faultstate”, the value in the fault state value register will be used by the function
block. As an example, if the upstream block connected to the AO block has problem this will
put the AO block in fault state – if the fault state value is 50, then the actuator will be sent to
50%.
Extreme care is recommend when using both the “action on loss of signal” and “fault state to
value” settings in order to avoid a potential conflict.
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