Flowserve MX Electronic Actuator SIL Safety IOM - Manual (Page 9)

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Limitorque MX Electronic Actuator FCD LMENIM2350-01 – 9/13
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3
Safety Requirements
3.1 Monitor Relay Annunciation
Any operating mode or self-detected system failure that could prevent the actuator from performing its Safety
Instrumented Function on demand from the Safety Instrumented System shall cause the actuator’s monitor relay to
de-energize, thus providing indication to the user via the alarm contacts on the monitor relay that the actuator may need
to be serviced.
Operating modes Local and Stop shall force the monitor relay to de-energize (indicates that the actuator is not available
for demands from remote control wiring).
Loss of power at the actuator terminals shall force the monitor relay to de-energize.
Built-in diagnostic scans shall be automatically performed by the actuator no less frequently than once every 10
seconds.
3.2 Local Control Knobs Sensors
Sensors for local control knobs shall be redundant such that a single sensor failure can be detected by the actuator’s
Built-In Self-Test [BIST] system. Self-detected hardware failures of the local control knobs shall force the monitor relay
to de-energize. However, while such failures shall be indicated by the monitor relay, the actuator shall be configured
such that a demand from the ESD input shall ignore any hardware failures at the local control knobs and shall respond
to SIF demands from the SIS.
3.3 ESD Override for Knobs
The actuator should be configured such that ESD demand signals will take priority over local control knob “STOP” and
“LOCAL” operating modes.
3.4 The LCD Display May Also Indicate Warnings and Alarms
NOTE: Because the LCD and its drive components may fail, the user must rely solely on the state of the monitor relay
for accurate SIF availability status.
3.5 Partial Stroke Test Interval
User should perform the partial stroke test sequence at least once per month during the mission life of the actuator.