Allen-Bradley 1756-L6 Series, Reference Manual, Page: 111 / 134

Rockwell Automation Publication 1756-RM001I-EN-P - May 2012 111
PFD Calculations for a SIL 2 System Appendix C
1794-IE8XT/B FLEX I/O-XT 8 analog input module x 1,959,360 5.10371E-07 — 1.40195E-07
1794-IF4I FLEX I/O 4 isolated analog input module x 9,885,959 1.01154E-07 — 1.39343E-07
1794-IF4IXT
(4)
FLEX I/O-XT 4 isolated analog input module x 7,297,140 1.3704E-07 — 1.39416E-07
1794-IF4ICFXT
(4)
FLEX I/O-XT 4 isolated analog input module x 7,297,140 1.3704E-07 — 1.39416E-07
1794-IR8 FLEX I/O 8 RTD input module x 5,016,231 1.99353E-07 — 1.39544E-07
1794-IRT8/B FLEX I/O 8 RTD/thermocouple input module x 1,407,269 7.10596E-07 — 1.40627E-07
1794-IRT8XT/B FLEX I/O-XT 8 RTD/thermocouple input module x 2,046,720 4.88587E-07 — 1.40149E-07
1794-IT8 FLEX I/O 8 thermocouple input module x 2,097,509 4.76756E-07 — 1.40124E-07
1794-IF2XOF2I FLEX I/O 2 input/2 output analog module x 8,464,844 1.18136E-07 — 1.39378E-07
1794-IF2XOF2IXT
(4)
FLEX I/O-XT 2 input/2 output analog module x 6,317,918 1.5828E-07 — 1.3946E-07
1794-IE4XOE2XT/B
(4)
FLEX I/O-XT 4 input/2 output analog module x 11,800,802 8.474E-08 — 1.32931E-07
1794-OE4/B FLEX I/O 4 analog output module 18,433,610 5.42487E-08 — 1.39248E-07
1794-OE4XT/B
(4)
FLEX I/O-XT 4 analog output module 11381744 8.786E-08 — 1.39316E-07
1794-OF4I FLEX I/O 4 analog output module 23,884,409 4.18683E-08 — 1.39224E-07
1794-OF4IXT
(4)
FLEX I/O-XT 4 analog output module 5,493,902 1.80202E-07 — 1.39508E-07
1794-TB3 FLEX I/O terminal base unit 250,000,000 4E-09 — 1.39147E-07
1794-TB3G FLEX I/O generic terminal base unit 100,000,000 0.00000001 — 1.39159E-07
1794-TB3GS FLEX I/O generic terminal base unit 100,000,000 0.00000001 — 1.39159E-07
1794-TB3S FLEX I/O terminal base unit 100,000,000 0.00000001 — 1.39159E-07
1794-TB3T FLEX I/O temperature terminal base unit 100,000,000 0.00000001 — 1.39159E-07
1794-TB3TS FLEX I/O temperature terminal base unit 52,312,000 1.91161E-08 — 1.39178E-07
1794-TBN FLEX I/O terminal base unit 100,000,000 0.00000001 — 1.39159E-07
1794-TBNF FLEX I/O fused terminal base unit 100,000,000 0.00000001 — 1.39159E-07
(1) Refer to the Revision Release List available at http://www.ab.com from the Product Certifications link.
(2) References a series A component if no other series is indicated by / X .
(3) The PFD calculations ControlLogix chassis are completed using an arithmetic average of the MTBFs for all five chassis types (that is chassis 1756-A4, 1756-A7, 1756-A10, 1756-A13,
and 1756-A17).
(4) Calculated values.
(5) Calculated values (615082-010)
(6) 1oo2 is required for compliance to edition 2 of IEC 61508.
(7) SIL 2-rated for non-interference in the chassis. However, I/O is not for use within a safety function.
(8) Calculations for the redundant power supply are completed with the presumption that both power supplies fail simultaneously.
(9) MTBF measured in hours. The values used here represent values available in January 2012.
(10)
λ
= Failure Rate = 1/MTBF.
Table 10 - PFD Calculations - 1-year for ControlLogix Component
Cat. No.
(1) (2)
Description
61508
(2010)
Mean Time Between
Failure (MTBF)
(9)
λ
(10)
Calculated PFD
1oo1
Architecture
1oo2
Architecture
Allen-Bradley Motors