Rockwell Automation did not need to create a special line of products to meet stringent SIL 2 requirements for its ControlLogix family. Sophisticated diagnostics and high levels of reliability are standard design in ControlLogix processors, I/O modules, and communication products.
Achieving a Safety Integrity Level 2 for systems using standard, off-the-shelf ControlLogix products requires no additional training and ensures that spares are readily available. Independent analyses have confirmed Safe Failure Fractions for the processors at well over 95 percent. Diagnostic I/O, including outputs that pulse test to verify that outputs are working, provide pre-emptive warnings of potential issues before they become a reality. These I/O modules also provide field-side testing for shorts, open circuits, and broken wires.
Analysis of field data confirms reliability metrics, including high Mean Time Between Failures (MTBF). For example, ControlLogix components for a sample 24V dc safety loop can result in MTBFs of more than a million hours or 100 years. This same field data, when used to estimate a Probability of Failure on Demand, yields values of 10-6. Such performance sets a new standard for reliability and availability, increasing safety, productivity, and profits while reducing down time, nuisance trips, and lifecycle costs for all customers.
