03/11/2016
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© Engineering Safety Consultants Limited
Page 19
Proof Testing
Reason for Proof Testing:
Functional safety is based on achieving a SIL with a
PFD
avg
in a defined band
PFD will increase with time until the Proof Test is
undertaken
If proof testing is not carried out at the prescribed
intervals the level of risk reduction assigned to the
during the design phase is not achieved
© Engineering Safety Consultants Limited
Page 20
PFD Calculations
PFD
S
PFD
L
PFD
FE
PFD
SYS
•
PFD = PFD
Undetected
+ PFD
Detected
•
Proof Testing focussed on Undetected Failures