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Proof Test Strategy
Where Proof Testing Cannot Detect All Dangerous Failures
IEC 61508-6 / B.3.2.5 / Edition 2
Faults in the safety system that are not detected by either diagnostic tests or
proof tests may be found by other methods arising from events such as a
hazardous event requiring operation of the safety function
or
during an
overhaul of the equipment
. If the faults are not detected by such methods it
should be assumed that the
faults will remain for the life of the equipment
.