Safety Instrumented Functions (SIF) Posted on 21st December 20159th May 2021 by ThePD (The Project Definition) Safety Instrumented Functions (SIF) refers to the SIF (Safety Instrumented Function) Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window)Click to share on LinkedIn (Opens in new window) Related Posted in HSE and tagged process, safety, term. ThePD (The Project Definition) ThePD has been developing the Preferred Project Definitions based on the actual project execution and operation experiences and knowledge with the Project Language, and sharing with you daily basis.