Rockwell Automation Safety Function: Hinge Switch - Manual (Page 10)

10 Safety Function: Hinge Switch
Rockwell Automation Publication SAFETY-AT096A-EN-P – November 2013
Overall Safety Function’s Functional Safety Data
Fault exclusion was used for the hinge switch subsystem. A PL value of d was
entered manually for this subsystem. Because fault exclusion was used, this
subsystem is not included in the overall safety function probability of failure per hour
(PFH) calculation. This derates the overall safety function to PLd.
E-stop’s Functional Safety Data Hinge Switch’s Functional Safety Data
Safety Relay’s Functional Safety Data Safety Contactor’s Functional Safety Data
Because these are electro-mechanical devices, the safety hinge switch, safety
contactor, and E-stop data includes the following:
• Mean Time to Failure, dangerous (MTTFd)
• Diagnostic Coverage (DCavg)
• Common Cause Failure (CCF)
Electro-mechanical devices’ functional safety evaluations include the following:
• How frequently they are operated
• Whether they are effectively monitored for faults
• Whether they are properly specified and installed