Specification Of The Safety Function - Allen-Bradley GuardLogix 5580 Original Instructions Manual

Specification of the Safety Function

You must create a specification for your safety function. Use this specification
to verify that program logic correctly and fully addresses the functional and
safety control requirements of your application. In some applications, the
specification can be presented in various formats. However, the specification
must be a detailed description that includes the following (if applicable):
• Sequence of operations
• Flow and timing diagrams
• Sequence charts
• Program description
• Program printout
• Written descriptions of the steps with step conditions and actuators to
be controlled, which includes the following:
– Input definitions
– Output definitions
– I/O wiring diagrams and references
– Theory of operation
• Matrix or table of stepped conditions and the actuators to be controlled,
including the sequence and timing diagrams
• Definition of marginal conditions, for example, operating modes and
emergency stop
The I/O portion of the specification must contain the analysis of field circuits,
that is, the type of sensors and actuators.
• Sensors (Digital or Analog)
– Signal in standard operation (dormant current principle for digital
sensors, sensors OFF means no signal)
– Determination of redundancies that are required for SIL levels
– Discrepancy monitoring and visualization, including your diagnostic
logic
• Actuators
– Position and activation in standard operation (normally ON)
– Safe reaction/positioning when switching OFF or power failure
– Discrepancy monitoring and visualization, including your diagnostic
logic
Rockwell Automation Publication 1756-RM012B-EN-P - April 2018
Safety Application Development Chapter 6
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