The Probability of Failure (PoF) calculation varies per Degradation Mechanism. Below this is explained for the Degradation Mechanism EXTERNAL CHLORIDE STRESS CORROSION CRACKING (EXTCLSCC).
Starting RBI 581 and Calculating the PoF
To start the RBI 581 assessment and calculating the PoF:
First, create the Equipment.
Then create a Corrosion Loop (CL).
Next create a Component under your new Equipment and link your Corrosion Loop to that Component.
Next in either the Equipment Detail Page or Component Details Page click the RBI 581 button.
You will be directed to the RBI 581 Detail Page for the specific Equipment. Here, you will see the Component, along with the Inspection History and Specs section.
Below in the Degradation Mechanism section click New D.M.
Select the “Chloride SCC External” DM that you added earlier to the CL.
Click Save.
The RBI 581 calculation tabs will appear. Stay on the Probability of Failure (PoF) tab. Note: One of the first calculations we need for the RBI 581 assessment is the PoF calculation. This calculation varies depending on the type of DM and, in some cases, the Equipment Group or Component Type. In our case, we selected a DM that uses the same calculation across all Equipment Groups and Component Types.
Fill in all the yellow required input fields.
Click the Calculate button. Note: The button will only be enabled once all required parameters are filled in; otherwise, a warning will appear, and the button will remain disabled. Additionally, if any data is modified after a calculation has already been completed, a warning will be shown, and the Calculate button will be re-enabled.
After the calculation the result will show in the right section of the screen.
Click Calculation steps to review the calculation.
Next fill in the Consequence of Failure (CoF) form.
When the RBI 581 assessment is Final Approved the Dynamic Form for the PoF becomes read-only.
Info
The PoF calculation makes use of a Dynamic Form of type "Probability of Failure". The Dynamic Forms used in RBI 581 are Global forms, meaning users cannot edit them unless they have CSA rights. There should be one Dynamic Form per condition, typically based on a DM, though some PoF calculations may vary by Equipment Group or Component Type. The condition used in the Dynamic Form can be viewed in the wizard. In the example of CHLORIDE SCC EXTERNAL it shows that the dynamic form will only apply if the Degradation Mechanism is "CHLORIDE SCC EXTERNAL."
Inspection Effectiveness
The Probability of Failure (PoF) tab also displays the Inspection Effectiveness Type and its Current value. If the Inspection Effectiveness type is "Severity Index," the column will show the current value of the Inspection Effectiveness (e.g., “1E - Ineffective” in the example below). Note that the Current value is also shown in the Inspection History and Specs section.
If the Type is null or any other value, the Current value will not appear. It is also possible that Inspection Effectiveness has not been determined yet because the PoF calculation is pending. In this case, a dash is displayed under the Current value.
The Inspection Effectiveness Type is specified in Settings\Maintenance\RBI Specific Data\Degradation Mechanisms.
Adding PoF Notes
Click Add Note to include additional information about the PoF calculation.
