Operation And Maintenance Plan; Maintaining Functional Safety; Functional Safety Assessment - Allen-Bradley AADvance T9110 Safety Manual

Chapter 2 Functional Safety Management
Functional Safety
Assessment
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The validation shall confirm that each functional safety requirement has been
implemented at the specified safety integrity level, and that the realization of
the function achieves its performance criteria, specifically that the process
safety time requirements have been met.
The validation shall also consider the potential external common cause failures
(power sources and environmental conditions) and ensure that the system will
provide fail-safe operation when these conditions exceeded its design
capabilities.

Operation and Maintenance Plan

The provision of an Operation and Maintenance Plan ensures that functional
safety can be maintained beyond the commissioning of the system. The in-
service operation and maintenance is normally outside the responsibility of the
system integrator, but the system integrator can provide guidance and
procedures to ensure that the persons or organizations responsible for
operation and maintenance can ensure the system operates to the specified
safety levels.
The Operating and Maintenance Plan shall include the following items:
• Clear definitions of power up and down sequences. These definitions
shall ensure that the sequences cannot result in periods when the system
is unable to respond safely whilst a hazard may be present.
• The procedures for re calibrating sensors and actuators. The
recommended calibration periods shall also be included.
• The procedures for periodically testing the system, together with
definitions of the maximum intervals between testing.
• Definitions of the overrides to be applied to be able to carry
maintenance of the sensors and actuators.
• The procedures for maintaining system security.

Maintaining Functional Safety

Design changes will inevitably occur during the system life-cycle; to ensure that
the system safety is maintained, such changes shall be carefully managed.
Procedures defining the measures for updating the plant or system shall be
defined and documented. These procedures are the responsibility of the end
user, but the system integrator shall provide sufficient guidance so that the
procedures maintain the required level of functional safety during and after the
changes.
The functional safety assessment (FSA) is intended to confirm the effectiveness
of the functional safety performance of the SIF's implemented by the SIS.
Rockwell Automation Publication ICSTT-RM446N-EN-P - April 2018