Orion Instruments Eclipse 705-51AX-XXX SIL Certified Safety Manual - Manual (Page 12)

12 57-651 Eclipse ® SIL Certified Safety Manual for Enhanced Model 705-51AX-XXX
7.0 Report: Lifetime of Critical Components
Although a constant failure rate is assumed by the proba-
bilistic estimation method, this only applies if the useful
lifetime of components is not exceeded.
Beyond the useful lifetime of a component, the result of
the probabilistic calculation method is meaningless, as the
probability of failure significantly increases with time.
The useful lifetime is highly dependent on the component
itself and its operating conditions—temperature in particular.
(e.g., electrolyte capacitors can be very sensitive).
Within the Enhanced ECLIPSE Model 705, tantalum elec-
trolytic capacitors are the limiting factors with regard to the
useful lifetime of the system. The tantalum electrolytic
capacitors that are used in the transmitter have an estimated
useful lifetime of about 50 years.
8.0 Appendices
8.1 Model 705 SIL Values
8.2 PFD Chart
The resulting PFD
AVG
values for a variety of proof test inter-
vals are displayed in Figure 2. As shown in the figure the
PFD
AVG
value for a single ECLIPSE Enhanced Model 705
with a proof test interval of 1 year equals 1.06E-03.
Enhanced ECLIPSE Model 705 GWR Transmitter
Figure 2
PFD
AVG
Values
SIL Values
ECLIPSE
Model 705-51Ax-xxx
SIL SIL 2
HFT 0
SFF (High Trip)
SFF (Low Trip)
91.9%
90.4%
PFD
AVG
9.72E-04
Proof Test Interval Annually
(refer to chart below
for other periods)