Acronyms & Terms Glossary

Safety Instrumented Function SIF

Safety Instrumented Function (SIF) is a safety function with specified Safety Integrity Level (SIL) implemented by SIS to ensure the safe operation of a process. Pre-determined guidelines are used to allow a process to continue or to enter a safe state if said guidelines are violated. The hazard and risk assessments identify the need for Independent Protection Layers (IPLs) to bring the risks associated with the various hazard scenarios in line with corporate risk tolerance guidelines. Where one or more IPLs are determined to be SIFs aeSolutions has the experience and expertise to:
- Confirm the SIL required for the SIF to avoid overdesign
- Create a preliminary design for the SIF that conforms to ISA/IEC 61511
- Identify the failure rates and parameters needed to calculate the Probability of Failure on Demand (PFD) of the SIF
- We use the most appropriate tool for calculating PFDs (or use the tool the client requires); for complex SIFs we can use Fault Tree Analysis for the calculations
- Optimize the SIF to meet the desired proof test interval and spurious trip frequency
- Recommend specific field devices for the SIF
- Document the calculations including the data and parameters used