rotork Mk3 - Page 29

Actuator Input Output Signals
Publication PUB089-005-00_0618 29 of 116
The FF commands operate on the Transducer block through Digital Output (DO) blocks that are
already connected in the default configuration. The network commands will operate the actuator
provided:–
• Local/Local Stop/Remote selector is in ‘Remote’ (or “Run” in a CVA).
• Foundation commands are not inhibited by the ‘Inhibit/HW_DI-4’ input parameter setting
and HW_DI-4 condition.
• No interlock is active.
• There is no active hard-wired control input or FF control input present.
• No alarm condition prevents the actuator from moving.
• The Transducer and Resource blocks are in AUTO.
 Open A digital command to cause the actuator to open to the fully open
position as indicated by the Open limit switch. Under correct operation
the actuator stops either when the open limit switch is reached, when
the torque exceeds the value set and the open limit switch has been
reached, or a new command is sent over the network.
 Close A digital command to cause the actuator to close to the fully closed
position as indicated by the Close limit switch. Under correct operation
the actuator stops either when the close limit switch is reached, when
the torque exceeds the value set and the close limit switch has been
reached, or a new command is sent over the network.
 Stop With no other command present, this digital command causes an
actuator motor that is running to stop.
 Emergency Shut Down
A digital command that causes the actuator to drive to its Emergency
position. There are settings within the actuator to determine if this is a
closed, open or stay-put action.
 Analogue Position Demand
This function is only available over the Foundation network. To initiate
Analogue Position Control this bit must be set to 1 and all other
actuator control bits must be set to 0. This enables the AO block to
function. The actuator will then move to within the deadband of
whatever position value has been set in the AO block output
parameter (range 0-100%, resolution 0.1%).
Provided limited range positioning is not invoked, the values 0% and
100% written to the AO output parameter produce a special case
output where the command is revised so as to fully close the valve to
its tight shut-off position (0%) and to fully open the valve (100%).
Note:
Many multi-turn actuators are set to open until the open limit switch is reached and close until
the closing on torque switch trips, but it is dependent on the type of valve. The quarter turn
actuators normally operate 90-degree valves, use stop-bolts on the actuator or gearbox, and
stop when these are reached. The control room indication is always taken from the end of travel
limit switch settings