Safety Considerations Guide, Tricon v9.0 - Tuv-fs.com

12 Hazard and Risk Analysis▼PES Steps in a Safety Life Cycle:1 Develop a safety requirement specification.An SRS consists of safety functional requirements and safety integrityrequirements. An SRS can be a collection of documents or information.Safety functional requirements specify the logic and actions to be performed byan SIS and the process conditions under which actions are initiated. Theserequirements include such items as consideration for manual shutdown, loss ofenergy source, etc.Safety integrity requirements specify a SIL and the performance required forexecuting SIS functions. Safety integrity requirements include:• Required SIL for each safety function• Requirements for diagnostics• Requirements for maintenance and testing• Reliability requirements if the spurious trips are hazardous2 For conceptual design, an engineer should:• Define the SIS architecture to ensure the SIL is met; e.g. voting 1oo1,1oo2, 2oo2, 2oo3• Define the logic solver to meet the highest SIL if different SIL levels arerequired in a single logic solver• Select a functional test interval to achieve the SIL• Verify the conceptual design against the SRS3 Develop a detail design including:• General requirements• SIS logic solver• Field devices• Interfaces• Energy sources• System environment• Application logic requirements• Maintenance or testing requirementsTricon Safety Considerations Guide