15
57-657 SIL Certified Safety Manual for ECLIPSE Model 706
9.3
Specific Model 706 Values
9.4
Report: Lifetime of Critical Components
According to section 7.4.9.5 of IEC 61508-2, a useful life-
time, based on experience, should be assumed.
Although a constant failure rate is assumed by probabilistic
estimation method, this only applies provided that the
useful lifetime of components is not exceeded. Beyond their
useful lifetime the result of the probabilistic calculation
method is therefore meaningless, as the probability of failure
significantly increases with time. The useful lifetime is
highly dependent on the subsystem itself and its operating
conditions.
The assumption of a constant failure rate is based on the
bathtub curve. Therefore it is obvious that the PFDavg
calculation is only valid for components that have this
constant domain and that the validity of the calculation is
limited to the useful lifetime of each component.
The expected useful life of ECLIPSE Model 706-512x-xxx
is at least 50 years.
It is the responsibility of the end user to maintain and
operate the Model 706-512x-xxx per manufacturer’s instruc-
tions. Furthermore, regular inspection should indicate that
all components are clean and free from damage.
When plant experience indicates a shorter lifetime than
indicated here, the number based on plant experience
should be used.
Product
ECLIPSE
Model 706-512x-xxx
SIL
SIL 2
HFT
0
SFF
93.1%
PFDavg
Refer to FMEDA report
