Rockwell Automation T8094 8000 Series TMR System Safety Manual - Manual (Page 24)

SAFETY MANUAL
D oc N umber T8094
I ssue 27 – June 2013
Page 3 of 103
1.3.1 Safety and Functional Safety
Safety: The expectation that a system will not lead to risk to human life or health.
Safety is traditionally associated with the characteristics or hazards resulting from the
system itself; including fire hazards, electrical safety, etc. The requirements to be
satisfied by the integrator here include wiring, protective covers, selection of materials,
etc.
Functional Safety: The ability of a system to carry out the actions necessary to
achieve or to maintain a safe state for the process and its associated equipment.
Functional safety is considered the ability of the system to perform its required safety
function. The requirements on the integrator here are to take the steps necessary to
ensure that system is free from faults, errors, and correctly implements the required
safety functions.
This Manual concentrates on functional safety; it is assumed that the reader is familiar
with the methods of achieving basic safety.
1.3.2 Safety Integrity and Risk Class Levels
The TMR system is certified for use for applications to SIL 3 for subsections of the
system using low density I/O.
A Safety Integrity Level (SIL) is defined in IEC61508/IEC61511 as one of four possible
discrete levels for specifying the safety integrity requirements of the safety functions to
be allocated to the safety-related system. SIL 4 has the highest level of safety
integrity; SIL 1 has the lowest.
However, IEC61508 requires that the complete installation meet these requirements in
order to achieve an overall SIL. The system covered by this technical manual forms
only a part of such requirements.