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57-651 Eclipse
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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.
