Functional safety components
The mission time of functional safety components is 20 years which equals the time
during which failure rates of electronic components remain constant. This applies to the
components of the standard Safe torque off circuit as well as any modules, relays and,
typically, any other components that are part of functional safety circuits.
The expiry of mission time terminates the certification and SIL/PL classification of the
safety function. The following options exist:
• Renewal of the whole drive and all optional functional safety module(s) and
components.
• Renewal of the components in the safety function circuit. In practice, this is
economical only with larger drives that have replaceable circuit boards and other
components such as relays.
Note that some of the components may already have been renewed earlier, restarting
their mission time. The remaining mission time of the whole circuit is however determined
by its oldest component.
Contact your local ABB service representative for more information.
Maintenance 159
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