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Performing Risk Analysis for RBI Failure Modes

In the process of evaluating a failure mode, you can quantify the relative risk (criticality) associated with the failure by evaluating the consequences (severity of the effect) and the probability of the failure occurring, assigning values for each factor. APM then calculates the relative risk by multiplying the severity number by the probability value.

When the relative risk is established, APM calculates the failure mode’s priority using a set of customer-defined rules. The consequence priority rules can be based on the failure mode’s severity, relative risk, downtime costs, downtime duration, or a combination. For example, the Extreme priority could be assigned to failure modes whose total severity is equal to 5.0.

You can apply a confidence factor to the analysis to quantify your faith in current maintenance or inspection practices to contain the failure mode’s risk. The confidence factor can adjust the inspection factor or the failure mode’s position in the risk matrix.

After you have analyzed the failure modes, you can compare failure modes and identify the relative importance of addressing them. The Risk Assessment view in the Strategy Development Analysis window includes failure mode lists based on criticality, consequence priority, severity, and relative risk, as well as a risk plot, risk matrix, and lists of the evaluations. This view is also available for the asset.

RBI analyses, typically for assets with Oil and Gas specifications, can use lookup tables and calculations to determine a failure mode’s probability of failure or consequence severity. For example, a health and safety evaluation could calculate the failure mode’s consequence ranking based on the toxicity index value assigned to the asset’s fluid type. For information about using these questionnaires, see Setting up Consequence Severity Evaluations to use Lookup Tables.

APM provides two ways to perform risk analysis:

•	Using evaluation forms for in-depth analysis of a failure mode’s consequences and confidence factors

•	Using a simpler evaluation that allows you to enter weighted severity values, probability values, and confidence factors

With both methods, APM calculates the relative risk and displays it in the risk matrix chart. The method available in the Maintenance Action Plan window depends on the option selected in risk analysis settings.

For instructions on using the simpler evaluation with weighted severities, see Performing RBI Risk Analysis with Weighted Severities.

Note: APM also provides a method of performing risk analysis on safety devices that protect equipment, people, and environments from events such as pressure build-up, fire, or equipment failure. Risk analysis is performed on one or more demand scenarios identified on the failure mode. For more information, see Performing RBI Demand Scenario Risk Analysis.

Note: Before you can perform risk analysis, the severities, probabilities, confidence factors, and risk matrix entries must be set up in the site’s risk analysis settings. If you are using evaluation forms, they must also be set up. For more information, see Setting up APM for RBI Analysis.

This topic explains how:

1.

To Evaluate the Probability of Failure – The probability of failure is the likelihood that the asset will fail due to the failure mode. You can determine the probability score using a questionnaire, selecting a value directly, or entering the estimated time between failure (ETBF). The options available to you depend on the analysis’ risk settings.

2.

To Evaluate Economic Effects of Failure – The economic consequence of failure reflects the financial effect of the failure on assets and production. Labor and material costs associated with lost production and with repairing or replacing the damaged equipment are economic consequences. The options available to you depend on the risk analysis settings. You can use a questionnaire or select a value directly, depending on the analysis’ risk settings.

3.

To Evaluate Health and Safety, Environmental, and Reputation Consequences – Equipment failure can cause hazards in the workplace and environmental damage. Examples are extreme temperatures, noxious fumes, and the release of liquids that cause pollution. Mitigating factors are considered when assessing health and safety and environmental consequences. Reputation consequences measure the impact that negative media attention has on an organization’s ability to operate in good faith. The levels of severity can also be associated with monetary costs. You can use questionnaires or select values directly, depending on the analysis’ risk settings.

When you have finished the probability and consequence evaluations, the risk matrix shows the resulting criticality and consequence scores. In this example, the results are Medium High (criticality) and Medium (consequences):

4.	To Assign a Detectability Value – When support for detectability is enabled in an analysis, the relative risk calculation becomes:

(Economic severity score + Health and safety severity score + Environmental severity score + Reputation severity score) * Probability score * Detectability score = Relative Risk Number

5.

To Evaluate Confidence Factors – The confidence rating reflects the confidence that the inspector and materials or corrosion engineer have in current maintenance or inspection practices to contain the failure mode’s risk. The higher the value, the greater their confidence. The failure mode’s criticality rating, mediated by the confidence factor, results in an inspection factor, interval, strategy, or a combination.

6.	Viewing the Risk Analysis Summary – You can view the most recent evaluation results by clicking Summary on the Criticality tab. The Risk Summary dialog displays tabs for each of the questionnaires used in the analysis.

Tip: You can export criticality evaluations for all the analysis’ failure modes to a Microsoft Excel® file. Then add data to the file and import it back into the analysis. For more information, see ......

To Evaluate the Probability of Failure

1.	Open the Maintenance Action Plan window.

2.	Make sure that editing is enabled.

3.	Select the Criticality view. For example:

4.	If probability can be based on the team’s estimate of the time between failures without maintenance tasks, the Criticality view also displays the Estimated TBF without maintenance area:

Enter the amount of time and the unit of measure. The corresponding probability value is selected in the risk matrix.

5.	To use a questionnaire, click Probability. The Probability of Failure Evaluation appears. The evaluation types (Simple, Detailed), categories, and questions available to you depend on the form’s design and the asset properties. Here is an example of a simple evaluation:

You can refer to the History and Barriers tabs for information to aid in the evaluation, for example, historical inspections, failures, and work.

6.

Complete the evaluation, selecting options for each category, entering notes, and using the arrow buttons to move between categories. If different evaluation types have been defined in the form’s design, you can select Simple or Detailed, as required by the complexity of the failure mode that you are analyzing.

As you move through the analysis, the Probability box displays the most severe probability value assigned to your selections. For example, if you select options for three categories, two of which have a result of “Negligible” and one with a result of “High”, the score for the evaluation as a whole will be “High”. This will be the probability used in the risk analysis.

7.	In the Analyzed by list, select the team member performing the evaluation.

8.	In the Notes box, you can provide additional information about the analysis. Notes are collected and available in several locations.

9.	When you have completed the evaluation, click OK. The evaluation form closes and the result (for example, very high, high, medium, low, or negligible) is selected in the risk matrix. For example:

To Evaluate Economic Effects of Failure

1.	In the risk matrix, click Economic. The Economic Effects Evaluation form appears. For example:

At any time, you can refer to the Asset Properties, History, Barriers, and Attachments tabs for detailed information about the asset.

2.	For the simple form, provide the following information. If you wish to perform a detailed analysis, skip to step 3.

Setting Name

Description

Total cost of lost production

Monetary cost of asset downtime in the event of failure. The amount is shown in the site’s currency.

Total repair costs

Monetary cost to repair equipment in the event of the asset’s failure. The repair cost does not include labor. The amount is shown in the site’s currency.

Total labor costs

Monetary cost of labor in the event of the asset’s failure. The amount is shown in the site’s currency.

Lost production quantity

In detailed evaluations, lost production quantity is calculated based on the cost equation’s intervals, which specify monetary values and quantities per duration (for example, hours).

Analyzed by

The analysis team member who performed the evaluation.

Note	Additional information about the analysis. Notes are collected and available in several locations.

As you enter amounts in the Total cost of lost production, Total repair costs, and Total labor costs boxes, APM calculates the total amount and the severity.

3.	To perform a more detailed evaluation, click Detailed. Here is an example of a detailed form:

As information is added to the form, APM calculates the total costs for the failure and displays the Severity score. All monetary amounts are shown in the site’s currency.

4.	Enter information to calculate lost production costs:

Setting Name

Description

Cost equation

If downtime or lost production costs are calculated for the asset, the default cost equation is selected, if applicable. This is the calculation rule used to determine the costs of a downtime incident or reduced throughput.

Tip: Select the Asset Properties tab and then the Downtime and Production Loss tab to view the production loss cost equation.

Downtime

Period of time that the asset will not function in the event of a failure.

Reduced throughput

When the failure mode results in reduced production instead of downtime, record the amount of time that reduced throughput is in effect.

Operating at

The percentage of production achieved when the failure results in reduced throughput.

Reduced throughput cost

APM calculates the cost of reduced throughput using the reduced throughput amount, the operating percentage, and the cost equation.

Downtime costs

APM calculates the downtime cost using the downtime amount and the cost equation.

Miscellaneous costs

Additional costs not included in the downtime or reduced throughput costs.

Total downtime costs

The total is calculated by summing all of the amounts in the Lost production costs area.

Lost production quantity

In detailed evaluations, lost production quantity is calculated based on the cost equation’s intervals, which specify monetary values and quantities per duration (for example, hours).

5.	Enter information to calculate repair costs:

Setting Name

Description

Materials

Monetary cost for materials to repair equipment in the event of the asset’s failure.

Equipment

Monetary cost for equipment to repair the asset in the event of failure.

Contractors

Monetary cost for contract workers to repair equipment in the event of the asset’s failure.

Miscellaneous

Additional monetary cost to repair the asset in the event of failure.

Total repair costs

APM calculates the total repair costs.

6.	Select the Labor and Miscellaneous tab. For example:

7.

Enter information to calculate labor costs. The number and types of trades listed in the Labor costs area are defined in the Economic Evaluations settings. They vary depending on the trades defined for the site and selected for the evaluation. For each trade, enter the amount of time required to respond to the failure. APM calculates the cost based on the trade’s rate.

8.	Secondary damage is additional damage caused to other assets by the initial or primary failure. If appropriate, select Secondary damage costs and enter an amount and a description of the damage. This information is included in the total costs and shown on the failure mode’s Failure Data tab.

9.	In the Occurrence costs box, enter the estimated fixed cost associated with a downtime occurrence. For example, this could be a fixed cost associated with restarting a machine after it has been shut down.

When failure mode optimization requires Isograph Availability Workbench, this attribute is mapped to project effect per occurrence cost in AWB.

10.	In the Cost of multiple failures box, enter the estimated cost if a protected function fails while its protective device or protective system is in a failed state.

11.	In the Notes box, you can enter additional information about the evaluation. Notes are collected and available in several locations.

12.	Select the Details tab. In the Analyzed by list, select the team member who performed the evaluation.

Note: For information about creating production cost rules, see Setting up Production Loss Rules on an Asset.

13.	When you have finished the evaluation, click OK. The result of the economic evaluation is shown in the risk matrix. For example:

To Evaluate Health and Safety, Environmental, and Reputation Consequences

1.	Click Health and Safety, Environmental, and Reputation in turn. The evaluation form appears. The evaluation types (simple, detailed), categories, and questions available to you depend on the form’s design and the asset properties.

At any time, you can refer to the Asset Properties tab for detailed information about the asset.

2.

Complete each of the evaluations, selecting options for each category, entering notes, and using the arrow buttons to move between categories. If different evaluation types have been defined in the form’s design, you can select Simple or Detailed, as required by the complexity of the failure mode that you are analyzing.

As you move through the analysis, the Severity box displays the most severe score assigned to your selections. For example, if you select options for three categories, two of which have a result of “Negligible” and one with a result of “High”, the score for the evaluation as a whole will be “High”. However, if a mitigation category has been defined for the evaluation, its score can raise or lower the severity. The resulting ranking is used in the risk matrix.

3.	In the Analyzed by list, select the team member performing the evaluation.

4.	In the Note box, you can provide additional information about the analysis. Notes are collected and available in several locations.

5.	When you have completed an evaluation, click OK. The evaluation form closes and the result is selected in the risk matrix. For example:

To Assign a Detectability Value

1.	In the Criticality view, select the appropriate value from the Detectability list below the risk matrix. This number is used in the relative risk calculation.

To Evaluate Confidence Factors

1.	Select the Confidence view. For example:

The Criticality box shows the result of the evaluations you performed on the Criticality view. If the degradation type has been identified in the failure mode’s degradation details, it is selected here.

Note: Degradation types, their confidence statements, and the scores assigned to them are set up in confidence settings and will vary depending on your organization’s requirements.

2.	In the Confidence evaluation area, select a degradation type. One of the following occurs:

•	The Confidence factor box displays the default for the degradation type. If the degradation type’s settings allow, you can select another value from the Confidence factor list.

•	If the degradation type supports confidence statements, they are displayed in this area. For example:

For each confidence statement, click a response, for example, No, Yes, or Intermediate. The Confidence factor box displays the result of your selection, indicating if confidence is low or high. The inspection factor, inspection interval, integrity group, and inspection strategy might also be supplied.

3.	The Lining tab is available if the asset has lining properties and the degradation type requires a separate confidence evaluation. Select the Lining tab. You will see one or more of the following:

•	The Condition list is available. Select a value from the list to describe the state of the lining at the time of inspection.

•	Confidence statements are presented as they are on the Asset tab. Select the appropriate responses.

Note: If both the Condition list and either confidence statements or an evaluation are available, the lesser of the two results determines the life adjustment factor shown in the Details area.

•	The Evaluation button is available. For example:

Click Evaluation to open the Confidence Evaluation window. For example:

Select a statement and click OK. The form closes and the statement is shown in the Lining tab. The Details area displays the inspection factor, inspection interval, or both, depending on the evaluation form’s properties.

4.	In the Details area, add the regulatory inspection frequency and the last inspection date. APM calculates the next regulatory inspection date, which you can change if required.

Note: If you selected a degradation rate on the Degradation Rates tab, as explained in Adding Degradation Rates to RBI Failure Modes, the selected yearly rate and next inspection date are copied to the Details area. Otherwise, you can enter these values here.

In this example, the confidence evaluations resulted in an inspection factor of 0.50, as shown in the Details area:

The information in this area includes:

Setting Name

Description

Confidence factor

The confidence factor represents the analysis team’s faith in current maintenance or inspection practices to contain the failure mode’s risk. The confidence factor can adjust the inspection factor or likelihood of failure up or down.

Analyzed by

Team member’s name.

Regulatory frequency

Interval between inspections as mandated by the appropriate regulatory agency. This value is defaulted from the analysis asset (or its closest ancestor with a default regulatory frequency). Note: The regulatory frequency is copied to any indicators that are added to the RBI action plan, if permitted by the analysis’ failure mode settings for indicator collection information.

Next regulatory inspection

APM calculates the next inspection date based on the last inspection date and regulatory frequency.

Inspection factor

An inspection factor is the portion of the asset’s remaining life calculated for the current degradation rate to be used when calculating indicator collection dates. For example, an inspection factor of “0.5” means that the indicator reading should be collected at half of remaining life. The greater the confidence factor, the higher the inspection factor, meaning that the interval between inspections is greater. The inspection factor is based on the confidence factor, degradation type, and the consequence priority (criticality) of the failure mode.

Life adjustment factor

A life adjustment factor is a portion of an asset’s by-design life span, for example, one tenth of its original estimated life. Typically, a life adjustment factor is used to estimate asset lining’s remaining life based on its condition at the time of inspection. This information is used to track the asset’s degradation.

Note: When the failure mode is marked Facilitation or Implementation Complete (or the study is promoted) its indicator can be updated with the life adjustment factor. If the indicator’s degradation rate supports lining, APM surveys the indicator on all of the failure modes where it is used. The shortest (non-zero) life adjustment factor is copied to the degradation rate’s Life Adjustment Factor setting. The analysis’ failure mode settings must specify that existing indicators use the values from the action plan.

Note: If the failure mode is based on an entry in the Damage Mechanism Library, the entry’s settings might specify that only one of inspection factor, inspection interval, or inspection strategy is permitted for the failure mode.

Inspection interval

An inspection interval is the period of time (usually years) between regularly scheduled inspections. Intervals are typically used with failure modes for assets prone to non-age related degradation, where process monitoring is more effective in avoiding degradation.

Integrity group

Integrity group assigned to this entry in the inspection factor matrix. Integrity groups provide an easy mechanism to group similar assets, for example, piping systems or heat exchangers.

Inspection matrix

Inspection interval factor assigned to the combination of degradation type, criticality, and confidence factor. This factor defines the inspection factor and whether inspections, strategy, and no inspections are allowed.

Inspection strategy

The inspection strategy describes the action to be taken for this combination of degradation type, criticality, and confidence factor. An example is “Maintain current inspection / monitoring”.

Last inspection date

Most recent inspection. By default, this field shows the date of the most recent indicator reading. You can change this date, if needed.

Selected yearly rate

Degradation rate selected on the failure mode to apply to the failure mode’s indicator.

Number of inspections

The number of inspections that returned the inspection effectiveness value. When the Evaluate Inspection Effectiveness function is run for the site, APM identifies processed indicator readings that specify an inspection effectiveness value within the specified time period. Using the rules set up for the site, the process calculates the inspection effectiveness value for each indicator.

Inspection effectiveness

Inspection effectiveness provides a measurement of the thoroughness, sensitivity, and efficiency of the inspection strategy. When the Evaluate Inspection Effectiveness function is run for the site, APM identifies processed indicator readings that specify an inspection effectiveness value within the specified time period. Using the rules set up for the site, the process calculates the inspection effectiveness value for each indicator.

Next inspection date

Date on which the next inspection is to be performed.

Viewing the Risk Analysis Summary

1.	In the Criticality view, click Summary to display the results of the risk analysis. For example:

A tab is displayed for the confidence evaluation and each of the questionnaires that were used to evaluation probability of failure and consequence severities.

2.	Select a tab to view information about the questionnaire.

3.	Click Close to dismiss the window.

When you have performed risk assessments for all of the failure modes in the analysis, you can compare them using the Risk Assessment view. For more information, see Viewing Risk Analyses for RBI Failure Modes.