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Functional Safety 2016
November, 2016 - London
Page 14 of 17
Table 4: Comparision of HIPPs PFDAVG taking into account C
PT
Equipment
Voting
λ
DU
Hours
λ
DU
Years
β
(%)
C
PT
(%)
MT
(Years)
Ti
(YEARS)
PFD
AVG
PFD
AVG
including C
PT
Ref:
Pressure
Transmitter
E+H PMD70
(FAIL HIGH)
2oo3 5.70E-08 4.99E-04 10 99 15
1 2.52E-05 6.24E-05 [9]
Logic Solver 1oo1 1.51E-10 1.32E-06 5 95 20 10 6.61E-07 1.29E-06 [15]
Solenoid 1oo2 1.36E-09 1.19E-05 10 84
5
1 5.96E-07 5.36E-06 [12]
Final
Element
(Actuator &
Valve
Assembly)
1oo1 1.29E-07 1.13E-03 0 95 20
1 5.65E-04 1.10E-03 [13]
Total
5.97E-04 1.18E-03
RRF
1674
850
Hardware SIL Rating
SIL 3
SIL 2
From this table it can be seen when the implimentation of the proof test coverage is accurately
applied to this high pressure protection system the calculated risk reduction provide decreases
by a factor 1.97. In certain circumstances the potential impact may be significant to the end-
user.
As discussed earlier the unrevealed failures will accumulated over time causing an increase in
PFD
AVG
over time until revealed by an actual demand on the SIF or during overhaul at the
mission time.