1756-RM001B-EN-P, Using ControlLogix in SIL2 ... - Tuv-fs.com

1-10 SIL PolicyCatalogNumberDescriptionFor a 1oo2 architecture, the PFD equation is much more complex. SeeIEC61508 Part 6 Annex B.The PFD values in Table 1.3 are given for the architecture that mustbe used for specific products to achieve SIL 2.Table 1.4 includes the same MTBF and Failure Rate values asTable 1.3 but adds calculated PFH values for high demand/continuousmode operation.The equation for PFH, from IEC61508, for a 1oo1 architecture is:PFH = λ DU = λ/2 (1 - DC)1756-Axx ControlLogix Chassis 40,143,919 (2)For a 1oo2 architecture, see Part 6 of IEC61508. The values inTable 1.4 are given for the architecture that must be used for specificproducts to achieve SIL2.Table 1.3ControlLogix Product Probability of Failure on Demand CalculationsMean Time λ (5) Calculated PFD:Between Failure(MTBF) (1) 1oo1 architecture 1oo2 architecture(average (3) )2.49E-085.58E-061756-CNB ControlNet Bridge 3,596,087 (2) 2.78E-07 6.23E-051756-CNBR Redundant ControlNet Bridge 3,385,813 (2) 2.95E-07 6.62E-051756-IA16I AC Isolated Input 4,144,192 2.41E-07 4.30E-061756-IA8D AC Diagnostic Input 3,856,320 2.59E-07 4.63E-061756-IB16D DC Diagnostic Input 7,386,774 1.35E-07 2.40E-061756-IB16I DC Isolated Input 3,562,624 2.81E-07 5.02E-061756-IF8 Analog Input 1,690,694 5.91E-07 1.08E-051756-IR6I RTD Input 3,456,960 2.89E-07 5.17E-061756-IT6I Thermocouple Input 4,784,000 2.09E-07 3.72E-06Publication 1756-RM001B-EN-P - October 2003