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Periodic Proof Testing (PT) is critical to provide assurance that the Safety
Instrument Function (SIF) provides the required risk reduction throughout
its Operational lifecycle.
The purpose of the PT is to detect dangerous undetected failures that
cannot be detected by the systems diagnostics.
However, not all failures can be detected by diagnostics and PT and may
only be identified during overhaul or when a demand is actually placed on
the SIF.
The fraction of undetected dangerous failures detected by the proof test is
referred to as the proof test coverage factor
(
C
PT
)
.
This presentation and the associated paper aims to identify how the C
PT
can be determined; the impact it has on the PFD
AVG
; where this information
can be located and how it can be applied in industry.
Introduction