Two Risk Calculation Methods are available for the RBI 581 assessment:
Risk Matrix (Balanced or Unbalanced).
Specifying which Risk Calculation Method to use
To specify which to use:
Click the Edit button.
Select the Risk Calculation Method: “Risk Matrix” or “ISO Risk Plot”.
Select additional details:
In case the “Risk Matrix” is selected check Risk Matric Balanced in case the Balanced matrix is desired. If not checked, the Unbalanced matrix will be used for the site’s RBI 581 calculations. Also select the Risk Target Criteria.
Selecting “ISO Risk Plot” disables Risk Matrix Balanced and Risk Target Criteria fields, and instead requires defining: Area Acceptable Risk Target and Economic Acceptable Risk Target. These values will be used in ISO‑based MII and future‑risk calculations and will be shown in the assessment when ISO Risk Plot calculation method is enabled.
Click Save.
Caution
Only users with the CSA role can modify these settings.
Specifying the Risk Target Criteria
To specify which to use:
Click the Edit button.
In case the “Risk Matrix“ is selected, then select the relevant Risk Target Criteria. In case the “Iso Risk Plot“ is selected, specify the rea Acceptable Risk Target and Economic Acceptable Risk Target instead.
Click Save.
Risk Matrix
Two Risk Matrices are available for the RBI 581 assessment:
Balanced, and
Unbalanced.
The Risk Matrix is shown on the RBI 581 Details Page in the Risk tab and in the right section of the RBI 581 assessment details. The gray circle represents the current Risk value, while the blue line indicates the Criticality Target. The blue circle shows the Next Inspection Date (NID), and the Maximum Inspection Interval (MII) is the number of years it will take for the Risk to reach the NID, which is why an upward arrow is displayed.
Below is an examples of the matrix in the Risk tab: showing only the Risk circle and the target line. In this case the Risk Target Criteria was set to Medium (M).
Below is the matrix in the Results (right) Pane. It shows a more detailed view with the NID circle, Risk circle, target line, and arrow. In this case the Risk Target Criteria was set to Medium (M).
Timeline
The "timeline" (a black line with dots) indicates which cells contain dates. Hover on the dot to see the date. Additionally, a moving blue dot represent the current risk (our position on the timeline).
Risk Chart and Table (Risk Overview per Assessment)
When the PoF and the CoF has been calculated, the Calculate button in the Results Pane becomes enabled. You can then click Calculate. The calculation provides a comprehensive series of results that trace the progression of risk from PoF at Age 0 up to PoF at Age 50 years. These results include:
Age: The component's age at a certain point in time.
Date: The date when a certain PoF level is exceeded.
PoF (Probability class): The class of probability.
PoF (Calculated Probability): The calculated probability.
CoF: The Consequence of Failure.
Risk Category: The risk category at a certain point in time.
To provide a clear overview of the risk assessment, the data is visually represented in both a chart (on the Chart tab) and a table view (on the Risk Overview per Assessment tab).
The Risk Chart (plot) visually highlights the remaining time until the next predicted change in the Probability of Failure.
To see the information in table format click the Risk Overview per Assessment tab.
Additional Information shown on the Risk tab
The Risk tab also shows the Risk Matrix Type and the Risk Target Criteria, which are defined in the Criticality and Probability Default Values table found in the RBI 581 Specific Data settings. Alternatively to the Risk Target Criteria, the Legal/Local Inspection Interval Target can be set to be used as Criticality Target. The Risk Matrix Type and Risk Target Criteria values originate from either site, plant, or unit level and this location name is shown in the Location field. Clicking on the Location name will take you to the settings, where you can modify the default values and access more information (if you have a relevant Role).
Non-Age-Related and Strategy Based Degradation Mechanisms
For a NAR or Strategy-based Degradation Mechanism, Age is not considered - meaning the risk remains constant over time. As a result, the Risk Target Criteria, chart and table tabs, and the blue risk target line (seen with Age-Related DFs) are not shown. The future risk indicator is also omitted, since the risk does not change.
ISO Risk Plot
The ISO Risk Plots provides a continuous, log–log representation of risk, and allow for more detailed analysis of Area and Economic consequences.
ISO Risk Plot (for Economic Consequence)
The ISO Risk Plot for Economic Consequence gives you a continuous, two-dimensional view of risk for an RBI 581 assessment. This plot becomes available when “ISO Risk Plot” is selected as the Risk Calculation Method at the site, plant, or unit level.
The plot maps the relationship between:
Economic Consequence of Failure — x-axis (displayed in the selected currency)
Probability of Failure — y-axis (events/year)
Both axes use a logarithmic scale, so you can analyze risk behavior across a wide range of values — something a discrete risk matrix cannot show. The x-axis automatically expands to fit the range of the displayed risk points, ensuring all economic consequence values (including those reaching into the billions) remain fully visible. All values on the plot are shown in the active currency.
What appears on the chart
ISO Risk Category Lines: The plot includes ISO risk category threshold lines based on hard-coded values from API RBI 581 (3rd edition). These diagonal lines divide the chart into risk zones (e.g., Low, Medium, Medium-High, High) and are calculated using standard ISO risk equations. They are displayed as dashed lines so you can easily distinguish them from the acceptable risk target.
Economic Acceptable Risk Target: If an Economic Acceptable Risk Target has been configured in Settings, it appears on the plot as a solid blue line. This line represents your organization's acceptable risk level for economic consequences and is displayed alongside the standard ISO category lines, letting you directly compare calculated risk against your defined target. The configured target value is also shown above the plot.
Risk Points: Risk points on the plot mark the moments when risk reaches an ISO risk category threshold line. Calculations always start from age 0 and identify the points in time at which each ISO risk category line is crossed. Each dot therefore represents a transition into a new ISO risk category, rather than a continuous time-based projection. If the MII calculation stops at MaxRL, a corresponding risk record is created as well. All risk records are listed in the grid below the plot and serve as the source data for the plotted risk dots.
Note
Hover over any risk dot to view its details in a tooltip — Area, CoF, PoF, Risk, Date, and Age at which that risk level will be reached.
ISO Risk Plot for Area Consequence
The ISO Risk Plot for Area Consequence offers a continuous, two-dimensional view of risk for an RBI 581 assessment. It becomes available when you select “ISO Risk Plot” as the Risk Calculation Method at the site, plant, or unit level, under.
The plot illustrates the relationship between:
Area Consequence of Failure — plotted on the x-axis (m²/year or ft²/year)
Probability of Failure — plotted on the y-axis (events/year)
Both axes use a logarithmic scale, enabling you to examine risk behavior across a wide range of values — a level of detail not achievable with a discrete risk matrix. The x-axis can expand dynamically depending on the range of displayed risk points, ensuring all Area Consequence values stay fully visible. Values on the plot follow the active unit system.
Chart contents
ISO Risk Category Lines: These threshold lines are based on hard-coded values from API RBI 581 (3rd edition) and divide the chart into distinct risk zones (e.g., Low, Medium, Medium-High, High), calculated using standard ISO risk equations. Because they're shown as dashed lines, they're easy to tell apart from the acceptable risk target.
Area Acceptable Risk Target: When an Area Acceptable Risk Target has been set up in Settings, it's shown on the plot as a solid blue line, representing your organization's acceptable risk level for area consequences. Displaying it alongside the ISO category lines lets you compare calculated risk directly against this target. The configured target value also appears above the plot.
Risk Points: Each risk point marks the moment at which risk reaches an ISO risk category threshold line. Calculations begin at age 0 and identify the point in time where each threshold is crossed — meaning every dot represents a transition into a new risk category, not a continuous timeline. If the MII calculation stops at MaxRL, a corresponding risk record is generated as well. These records populate the grid beneath the plot and serve as the underlying data for the risk dots shown.
Note
Hovering over a risk dot displays a tooltip with the Area, CoF, PoF, Risk, Date, and Age at which that risk level is reached.