The Safety Lifecycle

The Safety Lifecycle (in IMS SIS).

The Safety Lifecycle, a cyclic process where all hazards are identified and analyzed, can be outlined in a few steps:

• Determining the Hazard Scenario and Consequence (via a HAZOP study).
• In case of a high Consequence, initiate a LOPA study.
• During the LOPA, based on the Initiating Event frequencies, and Barrier PFDs, calculate the Overall RRF and Overall SIL level for the Consequence.
• Evaluate the Overall SIL to assess the adequacy of the existing Barriers against the Hazard Scenario.
• If the Overall SIL for the Consequence is not acceptable, start a SIF Analysis and determine the SIF’s minimum required RRF, i.e., its Target PFD, that achieves an acceptable Overall SIL level.
• Design a SIS so that each SIF’s Achieved PFD is less than its Target PFD.
• Lastly assign the selected Tests (with their tuned Test intervals) to the associated Equipment’s Schedules to ensure the SIFs achieve the target PFDs.