Flowserve MX Electronic Actuator SIL Safety IOM - Manual (Page 23)

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Limitorque MX Electronic Actuator FCD LMENIM2350-01 – 9/13
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8
Safety Instrumented
System (SIS) Assessment
The actuator is a type B product that is fit for function in SIS that may require Safety Integrity Levels 2 or 3.
All Safety Instrumented Functions may be employed for SIL2 and SIL3 SIS (see section 5 Limitorque MXa Safety
Instrumented Functions [SIF])
a CAUTION: It is the responsibility of the SIL design engineer to carry out an overall SIL calculation for any Safety
Instrumented System for which a Limitorque SIL rated actuator may be incorporated.
When SIL2 is required, then a single actuator may be employed in a single, one out of one configuration with a
Hardware Fault Tolerance = 0. ( See section 6 MXa Safety for an example of how deployment of an MXa actuator could
affect the SIL capability of a SIF)
When SIL3 is required, then two actuators may be employed with a Hardware Fault Tolerance = 1.
The SIL certificate and assessment report are public domain documents and should be reviewed by the SIL design
engineer. These documents may be found on the internet at http://www.exida.com/index.php/resources/sael/.