196 Rockwell Automation Publication 1756-UM001M-EN-P - February 2012
Chapter 13 SIL 2 Certification
High-availability Configuration
In the high-availability configuration, redundant controller chassis are used to
increase the availability of the control system. The modules in the redundant
controller chassis include the redundancy modules and ControlNet modules
for redundant communication, as well as the ControlLogix controllers.
Figure 44 - Typical SIL Loop with Controller Chassis Redundancy
Plant-wide Ethernet/Serial
ControlNet
SIL2-certified ControlLogix components’ portion of the overall safety loop.
Software
For SIL applications, a programming
terminal is not normally connected.
HMI
For Diagnostics and Visualization (read-only access to controllers in the safety
loop).
Sensor Actuator
EN
2 T
CN
2
ControlNet
To nonsafety related systems outside the ControlLogix portion of the SIL2-
certified loop.
To other safety
related
ControlLogix and
remote
I/O chassis.
Overall Safety Loop
CN
2
CN
2
EN
2 T
CN
2
CN
2
I/O
Primary Chassis
Secondary Chassis
Remote I/O Chassis
R
M
R
M
The high-availability ControlLogix system is fault-tolerant only for the devices in the primary/
secondary controller chassis. The rest of the high-availability system is not considered to be fault-
tolerant.
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