SIF Design Status

Each SIF Analysis has a DS (Design Status) associated with it. This is shown on the Analysis Main Screen, as well as on the Details Page General Tab and Design Tab.

DS Indicator for Unrated (-) SIFs

• Not Applicable - When the Assessment Status is OK implying that no SIL is required.

• NOT OK - When the Assessment Status in NOT OK.

DS Indicator for SIL A rated SIFs

• NOT OK - When AS is NOT OK, or when Success Criteria is not OK, or when Achieved PFD > Target PFD, or Process Safety Time > SIF response time. (Brownfield project)

• OK – When AS is OK, design is completed, and Achieved PFD < Target PFD, and Process Safety Time > SIF response time. A Fault Tolerance check is not applicable for SIL A rated SIFs.

• A – When the design is not completed. (Greenfield project)

DS Indicator for SIL ≥ 1 rated SIFs

• OK – When AS is OK and all design criteria are met (see below).

• NOT OK – When AS is NOT OK, or when any of design criteria is not met.

Design Criteria

The achieved values from a SIF design are checked against the following criteria before the design is deemed to be OK.

1. Subsystem populated with Equipment Tags.

2. Success Criteria on Subsystem and Equipment Tag level OK.

3. The Fault tolerance is checked against the requirement for the Target SIL.

4. Achieved PFD < Target PFD.

5. Process Safety Time > SIF response time.

Other Status Indicators shown on the Main Screen

In addition to the DS indicator also the PS, FT, SC, and PFD indicators show on the SIF Analysis Main Screen.

Performance

The Performance check considers two criteria: The Sensor Accuracy (on the Sensor), and the Tight Shut-Off (TSO) for valves (on the Final Element). The Sensor Accuracy of each Sensor Subsystem is the highest of the accuracies of the individual Equipment. If smaller than the target Accuracy specified, the Sensor Subsystem Performance is set “OK”. The Final Element Subsystem is TSO if all Equipment of the valve family in the Subsystem are TSO. If the Subsystem is TSO required and all valves in the Subsystem are TSO, the Performance is set “OK”. See Verifying SIF Performance.

FT (Fault Tolerance)

This dangerous Fault Tolerance requirements check is performed based on Route 2H as specified in IEC 61508 paragraph 7443. See Verifying SIF Dangerous Fault Tolerance requirements

SC (Success Criteria)

The SC indicates whether the Success Criteria is filled in Correctly in the SIF Design. See Defining SIF Success Criteria

PFD (Probability of Failure on Demand)

The PFD indicates whether the calculated SIF Achieved PFD is less than the Target PFD. See Calculating SIF Achieved PFD and Verifying Integrity.