Allen-Bradley 1756-L6 Series, Справочное руководство, Страница: 14 / 134

14 Rockwell Automation Publication 1756-RM001I-EN-P - May 2012
Chapter 1 SIL Policy
Boiler and Combustion Considerations
If your SIL 2-certified ControlLogix system is used in combustion-related
applications, you are responsible for meeting National Fire Protection
Association (NFPA) standard NFPA 85 or NFPA 86. A few failures in
ControlLogix SIL2 may take up to eight hours to detect, therefore eight hours is
the worst case reaction time. You should also consider system reaction capability
as explained in
Appendix A .
If your system must meet standard EN 50156, then you must also meet the
requirements identified in the current version of EN 50156. To use FLEX I/O or
1756-series I/O modules in SIL 2 EN50156 applications, you must use a
GuardLogix controller. Refer to the GuardLogix Safety Reference Manual,
publication
1756-RM093 .
SIL Compliance Distribution
and Weight The programmable controller may conservatively be assumed to contribute 10%
of the reliability burden. A SIL 2 system may need to incorporate multiple inputs
for critical sensors and input devices, as well as dual outputs connected in series to
dual actuators dependent on SIL assessments for the safety-related system. See
Figure 2 .
Figure 2 - Typical ControlLogix SIL 2 Systems
IMPORTANT
When using a GuardLogix controller with SIL 2-rated 1756 or 1794 I/O, you
must also follow the requirements defined in this manual.
Actuator
Digital
Output
Module
+V
43383
43384
Input
Module
Sensor
Sensor
40% of the
PFD
10% of the PFD
50% of the PFD
+V
10% of the PFD
Input
Module
Controller
Standard
Output
Module
Input
Module
Input
Module
Monitor-
ing
Input
Module
Sensor
Sensor
40% of the
PFD
Controller
Actuator
50% of the PFD