Lectura Complementaria No 2 - Método de Ciliberti

8/13/2019 Lectura Complementaria No 2 - Mtodo de Ciliberti

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Page 1 of 4January 14, 2001

Cri t ica li ty-Based Maintenanc e Criticality-Based Maintenance (CBM) is a four-step process of identifying andaddressing risk and exposure in a facility. These steps are:

1. Equipment Criticality Ranking (ECR)

2. Follow-up action plans3. Implementation of approved action plans4. Close-out of completed action plans

CBM is consistent with the following industry standards: API RP 580: Risk-Based Inspection NFPA 704 : Standard System for the Identification of the Hazards of Materials for

Emergency Response OSHA 29 CFR 1910.119 : Process Safety Management

Equipment Criticality Ranking

Equipment criticality ranking is a qualitative assessment of potential consequencesassociated with specific equipment items and the likelihood that those consequences willoccur. Potential consequences are evaluated for each equipment item using a cause-event-consequence process. Each failure scenario is a combination of a cause and event,and may have one or more potential consequences. Consequences considered for eachscenario are assessed and given values for consequence severity level and likelihood of occurrence ( Table 1 , Table 2 , and Table 3 ). Likelihood is based on a generic equipmentcase, i.e. what is typical for the specific type of equipment. The consequence andlikelihood values for each consequence are entered into a risk-rating matrix to give a risk rating value ( Figure 1 ). The risk rating for a given equipment item is the worst caserating for all consequences considered. Risk ratings are generated separately for hazard

and process consequences and the respective process and hazard rating values are enteredinto a risk-ranking matrix to give equipment criticality rankings ( Figure 2 ).

Risk ratings are also used to assess an order-of-magnitude level of exposure in monetaryterms ( Table 4 ). Exposure is only present at the equipment items where theconsequences occur and must be assessed in that manner. For example, a pressure vessel

protected by a relief valve has a given level of exposure. The relief valve may cause anoverpressure situation in the vessel if it fails to function, but itself does not haveassociated exposure.

Figure 1. Risk Rating Matrix Figure 2. Risk Ranking Matrix

VH 3 4 5 6 7 4-7 A A A A AH 2 3 4 5 6 4 A A A A AM 1 2 3 4 5 3 B B B A AL 0 1 2 4 2 C C B A A

C o n s e q u e n c e

N 0 0 1 2 3

P C R

0,1 D C B A A N L M H VH 0,1 2 3 4 4-7 Frequency HCR


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Table 1. Safety and Environmental Consequence CategoriesCategory Select highest category for which one criterion is satisfiedVery High Multiple fatalities of company or associated personnel.

Severe injury, illness, or fatalities of one or more members of the community. Catastrophic environmental impact requiring a full-scale response by outside

agencies.High Death of one company or associated person. Severe injury or illness of multiple plant personnel. Major reportable environmental incident requiring significant company resource

commitment as defined by EH&S guidelines. Notification of regulatory agencies,negative press coverage. Any hydrocarbon, produced water, or drilling fluid spillgreater than 12 bbl within the facility boundaries or any spill outside the facilityboundaries. Any spill of acid, caustic, or hazardous chemicals > 0.2 cubic metersregardless of location

Medium Medical treatment required for personnel. Minor reportable environmental incident as defined by EH&S guidelines. Any

hydrocarbon, produced water, or drilling fluid spill greater than 12 bbl within the facilityboundaries or any spill outside the facility boundaries. Any spill of acid, caustic, or hazardous chemicals > 0.2 cubic meters regardless of location.

Low Minor medical treatment or first aid required for plant personnel. Non-reportable environmental incident.

Negligible No safety or environmental consequences.

Table 2. Process Consequence CategoriesCategory Select highest category for which one criterion is satisfiedVery H igh Major production loss.

Financial impact at a corporate level.400,000 4,000,000+BBL$10 7 - $10 8 + USD

High Significant loss of production capacity (50-100%) for shortterm (


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Table 4. Exposure Matrix (Consequence x Likelihood)

VH 1.00E+08 $1,000 $10,000 $100,000 $1,000,000 $10,000,000H 1.00E+07 $100 $1,000 $10,000 $100,000 $1,000,000M 1.00E+06 $10 $100 $1,000 $10,000 $100,000L 1.00E+05 $1 $10 $100 $1,000 $10,000

C o n s e q u e n c e

N 1.00E+04 $0 $1 $10 $100 $1,0001.00E-05 1.00E-04 1.00E-03 1.00E-02 1.00E-01

N L M H VHFrequency/Probability

Total Exposure = (Hazard & Process Risk Amounts)

Furthermore, due to the qualitative nature of the ECR assessment, careful considerationmust be given as to whether the sum of the exposure of subsets of systems equals thetotal exposure for the system. For example, the Mainline Pipeline has been evaluated by

piping segments between valve stations. The maximum consequence level associatedwith each segment leak was very high. The likelihood of such a consequence wasconsidered as Medium: one occurrence is credible in the facility lifetime, based on thatfact that such failures are known to occur in industry. It would be inaccurate to state thatthe level of exposure of the Mainline Pipeline is the sum of the exposure level determinedfor each segment. Exposure level for this item would instead be the maximum exposurelevel of its components.

Follow-up Action PlansFollow-up is a process of reviewing high-risk equipment items and preparing andimplementing action plans for risk reduction. Figures 1 and 2 identify Red, Gray,and White zones associated with criticality ratings for each equipment item. Action

plans should be brought forward for items in the red and gray zones; no action is requiredfor white-zone items as they are at acceptable risk levels. In general, all red zone itemsshould be reduced to a minimum of gray zone. Gray zone items should all be evaluatedfor risk reduction, but in some cases risk cannot be feasibly reduced.

Preparation of Action PlansAction plans are used to identify a course of action for reducing risk; they do not includea design package for recommended changes, but rather bring forward a plan for risk reduction for approval by management. The action plan is prepared as a document thatidentifies the current situation and level of risk, proposed action, and residual risk oncethe action has been implemented.Actions plans should be prepared with the low-cost solution in mind. The first step is todo more detailed analyses of equipment items in question to see if action is warranted.Some review questions might be:

Were assumptions too conservative? What is the specific versus generic case likelihood of the consequence? Is the design basis adequate where it was assumed inadequate in the ECR study? Are spare parts inventory levels adequate?


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If analyses show that action is warranted, low cost solutions should be reviewed first.These might include:

Implementation of procedures Implementation or improvement of predictive or preventive maintenance. Adjustment of spare parts inventory levels

Exhausting these possibilities, facilities changes should be evaluated.

Approval of Action PlansAction plans are presented to a management forum for approval in a sign-off meeting.Typical attendees at a sign-off meeting include engineering, production, and maintenancemanagers.

As a rule-of-thumb, a minimum of 100 actions plans should be presented at each meeting.These should be grouped for expeditious presentation, typically by type of action. Sign-offs are generally done by groups of action types once management is comfortable withthe basis and rationale for the respective types.

As part of the approval process, action plans should be assigned to specific people andgiven completion dates.

Implementation of Action PlansOnce action plans are assigned to the appropriate people, implementation becomes theresponsibility of the assignee. However, the CBM Lead Engineer has responsibility for monitoring the status of all action plans.

When risk for a given equipment item is reduced by implementing new procedures,inspections, by taking credit for protective equipment, etc., the following considerations

must be taken:1. Effectiveness of risk reduction measure. Use as a guideline the proceduresoutlined in API Recommended Practice 580, Risk-Based Inspection.

2. Risk reduction via procedure or inspection requires that the procedure or inspection assume the criticality of the risk that it reduced prior to implementationof that procedure or inspection.

Management of Change procedures must accompany any facilities changes.

Close-Out of Completed Action PlansAfter disposition of approved action plans, process safety information (PSI) must be

finalized and confirmed. Confirmation is documented by attaching appropriate copies of process safety information to an Action Plan Resolution Form. The Action PlanResolution Form gives a statement of the initial condition, the action taken, and asummary of before and after risk. The CBM Lead Engineer signs off the Action PlanResolution Form when the action has been satisfactorily implemented and applicable PSIupdated.

Lectura Complementaria No 2 - Método de Ciliberti

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