SIF Analysis General Tab

Here the SIF is defined in terms of Subsystems, connected LOPA & SIL requirement, and Assessment Details.

Details

Most of the information in the Details Section on this Tab will already be populated based on what you specified when you created the SIF. Additionally, you can also use this section to specify:

• Safety Critical Element (SCE) – When checked all associated Equipment will be SCEs. This is automatically set by IMS when a Severity > 2 is selected in the LOPA Assessment Summary, unless you set the Safety Critical Override.

• Safety Critical Override – If set to “No” this will be set automatically by IMS. Else you can override it to:

  • “Safety Critical” - in this case Safety Critical Element will be checked.

  • “Not Safety Critical” - in this case Safety Critical Element will not be checked.

• Safety Critical Element Reviewed - This needs to be checked when the warning "Require Process Hazard Assessment" (red text next to the Safety Critical Element) shows. When Safety Critical Element Reviewed is checked, the warning will be removed. The checkbox is enabled only when both Safety Critical Element is true (checked) and the warning is present. When the calculation for the SCE is retriggered the Safety Critical Element Reviewed checkbox will be unchecked again. If Safety Critical Element is checked because of the Safety Critical Override then the warning would not be shown and the Safety Critical Element Reviewed checkbox will be disabled. Note: The SIF Analysis cannot be Approved when the warning shows and Safety Critical Element Reviewed is not checked. A warning will also show in the approval panel: "Safety Critical Element not reviewed".

• Assessment Hold – Checked by default. When LOPA is done this can be manually unchecked.

• Design Hold – Checked by default. When the design is done this can be manually unchecked.

• Review Hold – This applies to migrated SIF Analyses. When review is done this can be manually unchecked.

• Waived – This can be checked when the SIF Analysis is waived. When this is checked the Design Hold is removed.

When applicable, the header will show the RS (Review Status), AS (Assessment Status), DS (Design Status), and Final SIL in the header. Click Refresh statuses to refresh them.

Subsystems

The SIF Type (“full” or “sensor only” or “final element only”) as specified in the Details section will determine what Subsystem types you can add: sensors, logic solvers, and final element. You can add existing Subsystems (for which the Equipment are already defined), or you can add new Subsystems.

To add a Subsystem:

• Go to the Subsystem section.

• Click +.

• Select an existing Subsystem, or click + to create a new Subsystem.

If valves are applicable for a Subsystem, it is also indicated if TSO (Tight Shut Off) is required. This is considered when Performance is verified during the Design. You can further edit the Subsystems after you added them:

• Click the Edit button.

• Add/update desired information.

  

• Click Save.

Take Note

Any changes made to a Subsystem will only be reflected in System Settings (Settings / Maintenance  / SIS Specific Data / SIF Analysis / Subsystems) after the SIF Analysis has been Final Approved.

Modifying Subsystem Type

Once the Subsystem is created, changing the Subsystem Type is only possible from Settings.

To modify the Subsystem Type:

• Navigate to Settings / Maintenance / SIS Specific Data / SIF Analysis / Subsystems.

• Find the applicable Subsystem.

• Click the blue Edit button.

• From the Type dropdown menu, select one of the available options.

• Click Save.

After the Subsystem Type is modified from the Settings the following will occur:

• Approved SIFs using the Subsystem with modified Subsystem Type will fall back to Draft.

• Approved & Draft SIFs will be modified.

• Success criteria on the Overall Subsystem level will become red.

• Success criteria on the Subsystem will remain the same.

• A warning for PFD recalculation will appear on the Approve Pane.

Connected LOPA(s)

If the SIF was created from a LOPA, it will show the connected LOPA here. You can click on the hyperlink to navigate to the LOPA.

The LOPA information, including the Assessment Summary and LOPA (with the applicable SIF) highlighted will be shown below this section.

To connect to a LOPA

From here, it is not possible to connect the SIF to a LOPA. However, you can connect the existing SIF to applicable LOPA(s) from the LOPA Details Page(s) - see Adding SIF Analyses to LOPAs.

If connected to multiple LOPAs

It is possible the have multi scenario LOPAs for a SIF Analysis. All LOPAs will show on the SIF Analysis. The worst Overall PFD will be used as the Target PFD for the SIF design verification calculations in the SIF Analysis.

Assessment Summary

The Assessment summary will show the connected LOPA’s Assessment Summary here.

If not connected to a LOPA:

• Click Edit.

• Set the Selected PFD or SIL.

• Click Save.

This will determine the Target PFD.

Continuous vs Demand

When the Demand Rate is calculated in the Assessment Summary for the SIF Analysis, IMS automatically updates the SIF mode to Demand when the Demand Rate is less than or equal to 1, and to Continuous when the Demand Rate is greater than 1 (see SIF Analysis - Overview). You can however use the Manual override toggle in the Assessment Summary to manually choose between Demand and Continuous mode, overriding the automatically calculated SIF mode.

As a rule of thumb, if the Real Demand Rate on the SIF in the LOPA diagram is less than half of the longest calculated testing interval (for Sensors and Final Elements), you should select Continuous mode.

LOPA

The connected LOPA’s Initiating Events and Barriers are displayed here. This is a copy of the LOPA itself, but with the applicable SIF highlighted in blue.

Assessment Details

Most of the Assessment Details will automatically be copied here from the connected LOPA, if available. Where applicable the latest LOPA information will also be available to add as default text.

To add available LOPA information:

• Click Edit

• Select the desired default text

• Click Insert default text.

  

• Click Save.

Hazard – Top event

If connected to a LOPA and the LOPA is connected to a HAZOP, then this will be copied here automatically from the Top Event of the HAZOP’s Consequence.

Design intent (DI)

This is the hazardous situation that is to be protected against. Typical entries are “Prevent P3201 cavitation” or “Prevent run-away reaction”, “prevent overfilling T4312” etc. Do not enter consequences as a design intent. E.g., do not enter “Prevent P3201 damage” because there are many ways to damage the pump and this SIF only prevents one of them!

(You may have already defined this in the popup window when you were creating the SIF Analysis.)

Demand scenario (DS)

If connected to a LOPA, the Initiating Event and Control Barriers information will be copied here automatically from the LOPA.

This section should define the scenario’s that could lead to a demand on the SIF. If connected to a LOPA, this should support the LOPA.

Typically, the most likely Initiating Events are listed. A demand scenario could be something like “Backflow will occur in case of failure of P1101 A/B AND two NRVs in series fail. Additionally, P1101A-B will be tripped in case of low suction head (C1102 level low).”

Consequence of failure on demand (CoFoD)

If connected to a LOPA, the Consequence of failure on demand will automatically be copied from the LOPA (as defined on the ).

This is a narrative describing the sequence of events from failure on demand via hazardous events to ultimate consequences including a verbal assessment of the consequence severity such that the selections in the RAM are supported by this text.

Consequence of spurious Trip

The analysis of the consequences of a safe failure (spurious trip) and the justification of possible additional instrumentation depends on the hardware design of the SIFs.

(This can only be defined here, on the SIF Analysis.)

ALARP notes

If connected to a LOPA, the ALARP notes will automatically be copied from the LOPA (as defined on the). Remember, changes made here will not b synced back to the LOPA.