User manual

Publication 1756-RM093F-EN-P - January 2010 101

Appendix

Probability of Failure on Demand (PFD) and

Probability of Failure per Hour (PFH) Data

Introduction

The following examples show probability of failure on demand (PFD)

and probability of failure per hour (PFH) values for GuardLogix 1oo2

SIL 3 systems.

GuardLogix Controller and

Guard I/O Safety Data

All of the examples use the following data.

Topic Page

GuardLogix Controller and Guard I/O Safety Data 101

PFD Values 102

PFH Values 102

GuardLogix Controller Safety Specifications

Attribute 1756 GuardLogix

Controllers

1768 Compact GuardLogix

Controllers

Hardware fault tolerance 1 1

Safe failure fraction 99.1% 99.0%

Functional test interval (T1) 20 years 20 years