ABB CPTC-02, Руководство пользователя

Страница: 57 / 78

and the STO circuit of the drive do not have electromechanical
outputs.
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.
Competence
The person who does the maintenance and proof test activities of
the safety function must be a competent person with expertise and
knowledge of the safety function and functional safety, as required
by IEC 61508-1 clause 6 and Ex regulations.
Residual risk
The safety functions are used to reduce the recognized hazardous
conditions. In spite of this, it is not always possible to eliminate all
Maintenance 57