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Safety and SIS · Glossary

What is a Safety Requirements Specification?

Symbol: SRSSIS design basisSafety and SIS

A safety requirements specification defines what each safety instrumented function must do and how well, as the basis for SIS design.

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Safety Requirements Specification Explained

The SRS lists for each SIF the hazard, trip points, safe state, response time, SIL, voting, test intervals, bypass rules and reset requirements.

IEC 61511 requires an SRS before detailed design; it is the reference for testing and later changes.

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Calculators for Safety Requirements Specification

CalculatorPFDavg CalculatorFree online calculator with formula and worked example.CalculatorLOPA SIL CalculatorFree online calculator with formula and worked example.

Free Downloads

Free downloadCause and Effect Matrix Template in ExcelFree download in Excel and PDF.Free downloadAlarm and Trip Setpoint List Template in ExcelFree download in Excel and PDF.

Frequently Asked Questions

What is a Safety Requirements Specification?

A safety requirements specification defines what each safety instrumented function must do and how well, as the basis for SIS design.

Is the cause and effect matrix the SRS?

It is part of it; the SRS also covers SIL, response time, testing and many other requirements.

Who owns the SRS?

Usually the operating company, with input from process, safety and instrument engineers.

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Related Terms

Safety termSafety Instrumented FunctionA safety instrumented function is one protective action of a SIS, from sensing a hazard to the final…Safety termCause and Effect MatrixA cause and effect matrix is a table showing which inputs (causes) trigger which outputs (effects) in a…Safety termProcess Safety TimeProcess safety time is the time from a process fault occurring until the hazardous event happens if no…

More Safety and SIS Terms

Safety termSafe StateSafe state is the process condition a safety function must reach to prevent the hazardous event, such as…Safety termSafety BypassA safety bypass is a temporary override that stops a trip or alarm from acting, for maintenance, testing…Safety termAlarm ManagementAlarm management is the process of designing, rationalising and maintaining alarms so operators get only…Safety termHazardous Area ZoneA hazardous area zone describes how likely an explosive atmosphere is at a location: Zone 0, 1 or 2 for…Safety termGas GroupGas group classifies flammable gases by how easily they ignite and how well flames pass through gaps:…Safety termEquipment Protection LevelEquipment protection level shows how unlikely equipment is to become an ignition source, matching it to…

All safety and sis terms · Full glossary A to Z

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