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Setting up Probability of Failure Evaluations to use Lookup Tables

You can automate the process of analyzing a failure mode’s probability of failure using lookup tables and delivered calculations. You can also define your own custom calculations.

Note: Support for criticality evaluation calculations is generally available. However, you must first enable feature 115 to use the functionality in APM. In the Enterprise window, select the Features view and the Enabled Features tab. Click Browse, select “Practical RBI - criticality evaluation calculations” and click OK. If APM is running as a smart client, click Refresh Enabled Features on the server. Then restart the client to use the functionality.

This topic explains:

•	Calculation of Criticality Evaluation Rankings

•	RBI Lookup Tables

•	Setup Tasks for Practical RBI Evaluations

•	To Set up a Probability Evaluation Based on Degradation Ratio

•	To Use the Questionnaire

•	To Set up a Probability Evaluation to use Damage Factors

•	To Use the Questionnaire

Calculation of Criticality Evaluation Rankings

You can calculate the probability of failure and consequences for a failure mode based on various lookup tables and calculations to produce criticality evaluation rankings.

The calculation function supports calculations that determine ranking values for criticality evaluations. In the criticality evaluation, the user is presented with a series of evaluation categories. Each evaluation category consists of a series of questions or impact statements.

Typically, the user would select the appropriate question for the failure mode being evaluated. The selected question has a ranking assigned to it. The ranking is used to select the corresponding probability or severity (health and safety, environmental, or reputation).

The ranking calculation provides an option to automate the determination of the ranking based on one or more inputs and the formula defined for the calculation. In most cases, the formula consists of a lookup table or a series of lookups. Once the ranking has been calculated, APM selects the corresponding question associated with the evaluation category.

In this example of a probability of failure evaluation, the user selected a degradation mechanism and entered the actual degradation rate. APM then determined:

1.	Degradation rate

2.

Ranking

3.	Lookup table used

4.	Probability question

5.	Probability

You can create or update questionnaires to calculate:

•	Probability of failure based on damage factor (based on damage mechanism, degradation rate, number of inspections, and inspection effectiveness)

•	Probability of failure based on actual degradation as a ratio of design degradation rate

•	Consequence of failure based on the Liquid Release Calculation

RBI Lookup Tables

You can view, edit, and create lookup tables. In the Site window, select the Strategy Development view, Settings tab, and either the Probabilities or Severities tab. Select the Evaluations tab. For example:

This tab lists the RBI lookup tables sets for the site. Double-click a set to view its lookup tables. For more information, see Setting up RBI Lookup Tables and Sets.

Setup Tasks for Practical RBI Evaluations

Setting up APM to use the lookup tables and calculations involves the following objects:

•

Asset types – Practical RBI evaluations are designed for assets that use oil and gas specifications, for example, piping, pressure vessels, centrifugal pumps, heat exchangers, and transformer subtypes. All types should allow degradation settings and some should have values for fluid type, maximum service temperature, and degradation design rate

•	RBI lookup tables – Populate the lookup tables that your organization requires. See Setting up RBI Lookup Tables and Sets

•	RBI lookup table sets – Create one or more sets of lookup tables to be assigned to risk matrices. Assign the default set for the site. See Setting up RBI Lookup Tables and Sets

•	Risk matrices – Create or modify risk matrices and assign RBI lookup table sets. See Setting up Risk Matrices

•	Probability and severity evaluations – Create or modify questionnaires. For each category, you can set evaluation options for simple evaluations, detailed evaluations, or both. A lookup table or calculation can be assigned to each. Ensure that each category supports automatic answer selection

•	Analysis types – Ensure that risk options for your RBI analysis types specify the following:

•	Evaluation forms by failure mode

•	Risk matrix that supports criticality evaluation settings (RBI lookup tables)

•	Evaluation forms (probability, health and safety, environmental, reputation) with categories that support practical RBI evaluation settings

See Setting Risk Analysis Options for Analysis Types

•	Calculations – Set up custom calculations for your organization, if needed. See Calculations

Setting up a Probability Evaluation Based on Degradation Ratio

This topic explains how to set up and use an existing probability of failure questionnaire to determine a consequence ranking based on the ratio between the failure mode asset’s actual degradation rate and design rate. Inputs for this calculation are:

•	The failure mode’s degradation mechanism

•	The actual degradation rate, as set on the failure mode

•	The failure mode asset’s design degradation rate. If a rate has not been set on the asset or an ancestor in the hierarchy, the theoretical rate on the failure mode is used

From the inputs, APM calculates the ratio and selects the probability score.

The degradation ratios lookup table must be populated.

For detailed information about other aspects of creating the evaluation, see Setting up Probability of Failure Questionnaires.

To Set up a Probability Evaluation Based on Degradation Ratio

1.	On the site’s Strategy Development view, select the Settings tab, the Probabilities tab, and the Probability Settings node in the tree.

Tip: You can also select the site’s Administration menu, Strategy Development Settings, Risk Analysis, and then Probabilities. The Strategy Development – Probability of Failure Settings dialog appears.

2.	Select the Questionnaires tab and open the questionnaire you wish to edit. The Evaluation Form Properties window appears. Click Edit. For example:

This example uses a simple evaluation, but this functionality is also supported on detailed evaluations.

The selection of a degradation ratio is based on sequence number first, then ratio. That is, the calculation looks for the first value, according to sequence, that meets or exceeds the input value. When setting up the lookup table, you might find it most effective to give each value a sequence number of “1” so that the selection is based on the ratio instead.

3.	Select the Categories tab. Create a consequences category called “Degradation ratio”.

4.	Enter the simple evaluation heading, for example, “Degradation ratio”.

5.	Add questions that correspond to the probabilities defined in the risk matrix that RBI analyses will use. For example:

6.	Select the Evaluation tab:

7.	On the Simple Evaluations tab, select Level 1 only. The Lookup or calculation area is added:

8.	Click Lookup table and select “Degradation ratio lookup” from the list.

Tip: Click to view or edit the values in the lookup table. For example:

9.	Ensure that Answer selection is set to “Automatic”.

10.	Set the default ranking number.

11.	Provide more information, if needed, in the Explanation box.

12.	Click OK to close the category. Then click OK to close the evaluation form.

To Use the Questionnaire

1.	Create an RBI analysis for an asset that supports degradation.

2.	In the Properties view, select the Risk Options tab.

3.	Ensure that the analysis uses evaluation forms by failure mode.

4.	Check that the standard RBI Lookup Tables set is assigned to the risk matrix used in the analysis:

5.	Select the Probability tab and ensure that the correct evaluation form is selected.

6.	Add a failure mode to the analysis. In the Maintenance Action Plan window, select the Degradation Rates tab.

7.	Select the asset design rate in the Selected rate list. For example:

8.	Select the Criticality view and click Probability in the matrix. The Probability of Failure Evaluation window appears:

The initial values are from the default ranking number selected in the category properties and failure mode’s Degradation Rates tab.

9.	On the Evaluation tab, select the degradation mechanism and enter the actual degradation. The degradation ratio is calculated, the ranking selected, the impact statement is selected, and the probability is selected. For example:

Tip: Select the Selections tab to view the results for this and other categories.

10.	Click OK to close the evaluation. The matrix is updated with the result.

To Set up a Probability Evaluation to use Damage Factors

1.	On the site’s Strategy Development view, select the Settings tab, the Probabilities tab, and the Probability Settings node in the tree.

Tip: You can also select the site’s Administration menu, Strategy Development Settings, Risk Analysis, and then Probabilities. The Strategy Development – Probability of Failure Settings dialog appears.

1.

2.	Select the Questionnaires tab and open the questionnaire you wish to edit. The Evaluation Form Properties window appears. Click Edit. For example:

This example uses a simple evaluation, but this functionality is also supported on detailed evaluations.

3.	Select the Categories tab and add a new consequences category called “Damage factor”.

4.	In the FM Consequences Evaluation Category window, General tab, add the simple evaluation heading, for example, “Damage Factor”.

5.	Add questions or impact statements that correspond to the probabilities defined in the risk matrix that RBI analyses will use. For example:

6.	Select the Evaluation tab:

7.	On the Simple Evaluations tab, select Level 1 only. The Lookup or calculation area is added:

8.	Click Lookup table and select “Thinning damage factor lookup” from the list.

Tip: Click to view or edit the values in the lookup table. For example:

9.	Ensure that Answer selection is set to “Automatic”.

10.	Set the default ranking number.

11.	Provide more information, if needed, in the Explanation box.

To Use the Questionnaire

1.	Create an RBI analysis for an asset that supports degradation.

2.	In the Properties view, select the Risk Options tab.

3.	Ensure that the analysis uses evaluation forms by failure mode.

4.	Check that the standard RBI Lookup Tables set is assigned to the risk matrix used in the analysis:

5.	Select the Probability tab and ensure that the correct evaluation form is selected.

6.	Add a failure mode to the analysis. In the Maintenance Action Plan window, select the Degradation Rates tab.

7.	Select the asset design rate in the Selected rate list. For example:

8.	Select the Criticality view and click Probability in the matrix. The Probability of Failure Evaluation window appears.

9.	Navigate to the Damage Factors category, for example:

10.	On the Evaluation tab, select the degradation mechanism from the list.

11.	The degradation ratio is defaulted from the failure mode’s selected rate. Adjust the number as needed.

12.	Enter the number of inspections and inspection effectiveness. The damage factor and ranking number are calculated, the impact statement is selected, the probability is selected. For example:

Tip: Select the Selections tab to view the result of this and other categories.

13.	Click OK to close the evaluation The matrix is updated with the result.