ABB - Page 1E x t e n d e d A u t o m a t i o n S y s t e m 8 0 0 x AFunctional safety Engineering - Safety Requirement Specification ABB - Page 2Functional safetySafety Requirement Specification?SRS Definition?SRS Input?SRS problems ABB - Page 3Functional safetySafety Requirement Spesification - SRS?Definition of Safety Requirement Specification, SRS?IEC 61511 part 1, 3.2.78?specification that contains all the requirements of the safety instrumented functions that have to be performed by the safety instrumented systems?Objective?Specify all requirements of SIS needed for detailed engineering and process safety information purposesFunctional safety ABB - Page 4Functional safetySRS Input Requirement?The safety requirement specification step occurs after SIL selection in the safety lifecycle?The following inputs should be considered?Process and hazards information (PHS report)?Regulatory requirements affecting SIS design?List of required Safety Instrumented Functions (SIF) including?The Hazards?Frequency of occurrence?Consequence?SIL level required ABB - Page 5Functional safetySRS Elements?The SRS contains two types of requirements?Functional Requirements?Description of the functions of the SIF?How it should work?Integrity Requirements?The risk reduction and reliability requirements?How well it should work ABB - Page 6Functional safetySRS Requirements?The SRS should contain these functional requirements?Definition of the safe state?Process inputs and their trip points?Process parameters normal operating range?Process outputs and their actions?Relationship between inputs and outputs?Selection of energize-to-trip and reenergize-to-trip?Response time requirement?Operator interface requirement ABB - Page 7Functional safetySRS Requirements?The SRS should contain these functional requirements?Considerations for manual shutdown?Considerations for bypass and override?Action on loss of power to the SIS?Response time requirements for the SIS to bring the process to a safe state?Response actions for overt faults?Reset functions ABB - Page 8Functional safetySRS requirement (cont)?The SRS should contain these integrity requirements?The required SIL for each SIF?Requirements for diagnostics to achieve the required SIL?Requirement for maintenance and testing to achieve the required SIL?Reliability requirements if spurious trips may be hazardous ABB - Page 9Functional safetySRS Quality?The measure of quality for any documentation, including a SRS, is not the number of pages or the documents weights but rather how precisely, quickly and clearly all required information is passed to the reader ABB - Page 10Functional safetyPotential SRS Problems?Hazard and Risk Analysis was done poorly (not at all), providing a bad input for the SRS?SRS out of date, not maintained?SRS revision control poor?SRS missing important requirement ABB - Page 11Functional safetySafety Requirement Specification?SRS Definition?SRS Input?SRS problems ABB - Page 12Functional safety