--- title: "Approving Corrosion Circuit Calculations" slug: "approving-corrosion-circuit-calculations" tags: ["Approval", "Corrosion", "General", "ONE IMS"] updated: 2026-10-27T23:11:28Z published: 2026-10-27T23:11:28Z canonical: "ims-handbook.cenosco.com/approving-corrosion-circuit-calculations" --- > ## Documentation Index > Fetch the complete documentation index at: https://ims-handbook.cenosco.com/llms.txt > Use this file to discover all available pages before exploring further. # Approving Corrosion Circuit Calculations A Corrosion Schedule is registered for a [Circuit](/v414/docs/pei-circuits) containing the data from NDE examinations (UT, RT, etc). Each Circuit has only one active Corrosion Schedule. Thus, when a Circuit is created the application generates such a Corrosion Schedule by default, which includes an [Event](/v414/docs/inspection-events-approvals) (Inspection Function: "Schd Edit/New Insp", Status: "ADMIN FINAL APPROVED"). There is no required ECH for wall thickness measurements, but in some cases you might enter an ECH to explain the way the inspection was performed or the findings of the inspection. Instead the Circuit [Calculation Summary](/v414/docs/the-calculation-summary) will be used to credit these Schedules. It is important to understand the difference between: - [Crediting](/v414/docs/approving-corrosion-circuit-calculations#crediting-corrosion-schedules-insp-completed) a Corrosion Schedule ("Insp Completed"), and - [Recalculating](/v414/docs/approving-corrosion-circuit-calculations#recalculating-circuits-recalculate) a Circuit ("Recalculate"). ![](https://cdn.document360.io/e492a0e0-a4ba-4aca-8fc6-76b95f91fdf3/Images/Documentation/corrosion-circuit-calculation-image-ibfaa2af.png?sv=2026-02-06&spr=https&st=2026-10-28T12%3A56%3A15Z&se=2026-10-28T13%3A56%3A15Z&sr=c&sp=r&sig=tYrJTa7I48iInh3RTaTM05NW7h9bwucVsQIzQuKzMYU%3D) To credit a Corrosion Schedule, a Calculation Summary must be Approved. ## Crediting Corrosion Schedules ("Insp Completed") Just like other types of Schedules a Corrosion Schedule has a NID and a Scope (i.e. the strategy, Scope or CML Measurement Points). The user dictates which CML Measurement Points (MPs) should be measured using the configuration rules in IMS and creates the Measurement Set (i.e. Workpack) in the configurator. After the NDE reading has been taken they have to be imported or entered into IMS. The user monitors the measurement results and calculates a new Remnant Life (RL) and combines this with the Interval Factor (IF) to predict the Next Inspection Date (NID). ### Draft For such new measurements / readings an "Inspection Complete" event is created when the user calculates the Circuit. The [Event](/v414/docs/inspection-events-approvals) for this Calculation Summary will be by default in "Draft" status. To see the Approval Status, click the *Approval* button. ![](https://cdn.document360.io/e492a0e0-a4ba-4aca-8fc6-76b95f91fdf3/Images/Documentation/image-0ZM2TAFW.png?sv=2026-02-06&spr=https&st=2026-10-28T12%3A56%3A15Z&se=2026-10-28T13%3A56%3A15Z&sr=c&sp=r&sig=tYrJTa7I48iInh3RTaTM05NW7h9bwucVsQIzQuKzMYU%3D) ### Final Approval CORROSION Schedules are completed/credited by a **Final Approval** on the [Calculation Summary](/v414/docs/the-calculation-summary) on new wall thickness measurements. Just like approving an ECH or other type of Schedule this [Event](/v414/docs/inspection-events-approvals) must be "WRITER APPROVED" and/or "LEVEL 1 APPROVED" (depending on user’s [Approval Privileges](/v414/docs/approval-levels)) before a final Approve can be done. When an "Inspection Complete" event for a Calculation Summary is **Final Approved**: - The Approval Status of the Credited Schedule will be "inactive". - The LID of the credited Schedule will be updated with the latest Measurement Date from the included measurements (see [Managing Measurement Sets](/v414/docs/managing-measurement-sets#completing-measurement-sets)). - The NID will be updated to show the next inspection, because the Schedule is now credited. - A new (active) Corrosion Schedule will be generated with Status "ADMIN FINAL APPROVED", which uses the calculated or time-based NID from the Calculation Summary as Next Inspection Date for the Schedule (based on the horse race applied). - If the [Circuit is inherit to an RBI Component](/v414/docs/relationship-between-cls-components-and-circuits), the Calc Summary will automatically be applied to the [RBI](/v414/docs/risk-based-inspection-rbi-theory) Analysis Inspection History. This will update the RBI Last Inspection Date (LID). For further explanation see [Step 13](/v414/docs/software-step-13) (Barrier Verification - when the Corrosion Schedule is being executed) and [Step 5](/v414/docs/software-step-5) (Inspection History) of the Degradation Management workflow. ## Recalculating Circuits ("Recalculate") A "Recalculation" Event is being triggered when circumstances or the context of the Circuit and/or CMLs will change. Instead of crediting a Corrosion Schedule and create a new one like we do with the "Inspection Complete" (on new measurements), the "Recalculation" Event is being used to update the Corrosion Schedule because of changed factors in determining the Next Inspection Date (NID) and the Remnant Life (RL). Because this is such a critical activity (i.e., NID can be changed), this [Event](/v414/docs/inspection-events-approvals) must be **Approved** to become in effect. Actions that trigger a "Recalculation" Event: - Click on the *Recalculate* button (both available on Circuit details and in S-IDAP). ![](https://cdn.document360.io/e492a0e0-a4ba-4aca-8fc6-76b95f91fdf3/Images/Documentation/corrosion-circuit-calculation-image-490viw02.png?sv=2026-02-06&spr=https&st=2026-10-28T12%3A56%3A15Z&se=2026-10-28T13%3A56%3A15Z&sr=c&sp=r&sig=tYrJTa7I48iInh3RTaTM05NW7h9bwucVsQIzQuKzMYU%3D) Recalculating the Calc Summary will cause the Status to go back in Draft. - Activate / deactivate CMLs. - Changing Circuit IF Strategy. - Changing Circuit Interval Factor. - Changing Circuit Calc Method. - Changing Ignore Calc Interval. - Changing Measurement data (reading, date, quality). Note: This is only possible to change data from the last measurement set and only when there is already a Recalculation Event in status other than Final Approved. - Delete a Measurement Set. - Perform RBI analysis. - Etc. ### Final Approval When a "Recalculation" Event occurs, the [Calc Summary](/v414/docs/the-calculation-summary) will go back into the Status "DRAFT". It will thus need to be **Final Approved** again. When the "Recalculation Event" has Final Approval status: - The Measurements from the last Measurement Set are not editable anymore (until a new "Recalculation" Event is generated). - The existing Corrosion Schedule is updated based on the current Calculation Summary results (and automatically Approved). > [!NOTE] > Take Note > > The recalculation date WILL NOT impact the Circuit’s Last Inspection Date and therefore also not the RBI LID via the [RBI Inspection History](/v414/docs/software-step-5). The inspection date is recorded in the [Measurement Set](/v414/docs/managing-measurement-sets#completing-measurement-sets) itself via the Measurement Date and is not impacted by the recalculation date. > > ![](https://cdn.document360.io/e492a0e0-a4ba-4aca-8fc6-76b95f91fdf3/Images/Documentation/image-RWQWR8OE.png?sv=2026-02-06&spr=https&st=2026-10-28T12%3A56%3A15Z&se=2026-10-28T13%3A56%3A15Z&sr=c&sp=r&sig=tYrJTa7I48iInh3RTaTM05NW7h9bwucVsQIzQuKzMYU%3D) Shell-Inspection Design Analysis and Plotting