Flowserve MX Electronic Actuator SIL Safety IOM - Manual (Page 19)

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Limitorque MX Electronic Actuator FCD LMENIM2350-01 – 9/13
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While PST signals are in their normal state, the user may command an ESD action by momentarily asserting the ESD
signal. The actuator will move the valve to its configured ESD position and keep it there until it receives an ESD release
command. Once released, the actuator may be returned to its normal position via the switches on its control cover
(local mode) or with the handwheel.
MXa may be easily configured such that ESD may override protection features such as over-torque, over temperature,
valve jammed, local stop, local open, local close, remote stop, remote open, remote close, close inhibit, open inhibit.
Reference section 10, ESD (Emergency Shutdown) Overrides, on page 31.
To fully test actuator health and availability for emergency service, the user may choose to run a partial stroke test. To
ensure that the complete ESD function is operational, PST testing should be initiated by the ESD signal.
In this scenario, asserting BOTH PST enable signals will cause the actuator to run a partial stroke test when the ESD
signal is asserted.
Asserting an ESD command with an NC contact allows an ESD action to occur when a failure occurs in the 24Vdc
supply or if the wiring for the remote input opens.
7.2.1 Monitor Relay Behavior when Configured as Enhanced PST
Relay de-energizes when PST is active (two PST ENABLE signals are asserted).
Relay de-energizes when PST enable signals are invalid (either both or zero PST enable signals are valid; a single signal
is invalid).
Relay de-energizes when momentary ESD release signals are invalid (either both or zero ESD release signals are valid; a
single signal is invalid).
7.3 Basic PST Configuration Options and Operation
7.3.1 Remote Input Option for Digital Input 1 (Terminal 34 or D2)
7.3.1.1 Target Position
Target position may be configured from 0 to 100%.
Default PST target position is 50%.
On acceptance of PST command, actuator will:
• Move toward the target position
• Stop within 2% of the target position
• Wait 5 to 10 seconds while Built-In Self-Tests are conducted
• Return to within 2% of start position and return to normal operation
7.3.1.2 Signal Logic
May be configured to initiate PST sequence when signal is present or removed.
7.3.2 Monitor Relay Actions During PST
Monitor relay is intended to indicate that an actuator is not available for operation from remote signals. As such, the
monitor relay will not provide any special indication of PST activity.