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Criticality Analysis for optimising OPEX cost lifecycle
3rd IFAC Workshop on Advanced Maintenance Engineering, Service and Technology 3rd IFAC Workshop Advanced Maintenance 3rd IFAC19-21, Workshop on Advanced Maintenance Engineering, Engineering, Service Service and and Technology Technology October 2016.on Biarritz, France 3rd IFAC19-21, Workshop on Advanced Maintenance Engineering, Service and Technology October 2016. Biarritz, France Available online at www.sciencedirect.com October 19-21, 2016. Biarritz, France 3rd IFAC Workshop on Advanced Maintenance Engineering, Service and Technology October 19-21, 2016. Biarritz, France October 19-21, 2016. Biarritz, France
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Criticality Analysis for optimising OPEX cost lifecycle Criticality Analysis for optimising OPEX cost lifecycle Criticality Analysis for optimising OPEX cost lifecycle Criticality optimising OPEX cost lifecycle Criticality Analysis Analysis for for optimising OPEX cost lifecycle Serra Parajes, Javier*
Serra Parajes, Parajes, Javier* Javier* Serra Adolfo Márquez** SerraCrespo Parajes, Javier* Adolfo Crespo Márquez** Serra Parajes, Javier* Adolfo Crespo Márquez** Antonio Sola Rosique*** Adolfo Crespo Márquez** Antonio Sola Rosique*** Rosique*** Adolfo Crespo Márquez** Antonio Sola Antonio Sola Rosique*** Antonio SolaEnagas, Rosique*** *Asset Management Coordinator, Madrid, [email protected] *Asset Management Coordinator, Enagas, Madrid, [email protected] *Asset Management Coordinator, Enagas, Madrid, [email protected] **Escuela técnica de ingenieros de la Universidad de Sevilla [email protected] *Asset Management Coordinator, Enagas, Madrid, [email protected] **Escuela técnica de ingenieros de la Universidad de Sevilla [email protected] *Asset Management Coordinator, Enagas, Madrid, [email protected] **Escuela técnica de ingenieros de la Universidad de Sevilla [email protected] **Escuela técnica de ingenieros de la Universidad de Sevilla [email protected] **Escuela técnica de ingenieros de la Universidad de Sevilla [email protected] Abstract: Identification and quantification of cost and value of industrial assets is a field in which much Abstract: Identification and quantification of cost and value of industrial assets is aa field in which much Abstract: and of and value assets in much terminology is mixed. When we try to analyze the importance of an asset for is our business, to discuss Abstract: Identification Identification and quantification quantification of cost costthe andimportance value of of industrial industrial assets isour a field field in which which much terminology is mixed. When we try to analyze of an asset for business, to discuss Abstract: Identification and quantification of cost and value of industrial assets is a field in which much terminology is mixed. When we try to analyze the importance of an asset for our business, to discuss about its costsis should not be separated from the value provided byofthe asset. Most of business, the times, to managers terminology mixed. When we try to analyze the importance an asset for our discuss about its costs should not be separated from the value provided by the asset. Most of the times, managers terminology is mixed. When we try to analyze the importance of an asset for our business, to discuss about its costs should not be separated from the value provided by the asset. Most of the times, managers only use the term “cost” because it seems to be more objective. Value isMost moreofsubjective and more about its costs should not be separated from the value provided by the asset.is the times, and managers only use the term “cost” because it seems to be more objective. Value more more about its to costs should not be separated from value provided by the asset.isMost ofsubjective the times, and managers only use the term “cost” because it seems to be more objective. Value more subjective more difficult define. However, we must try to the use definitions as amortization, inflation, replacement value only use the term “cost” because it seems to be more objective. Value is more subjective and more difficult to define. we must try to use definitions as amortization, replacement only useto the term However, “cost” because it seems to be more Value isinflation, more subjective and value more difficult to define. we try definitions as in order simplify the concept ofmust “value” to use improve our objective. decisions. difficult to simplify define. However, However, weof must try to to use definitions as amortization, amortization, inflation, inflation, replacement replacement value value in order to the concept “value” to improve our decisions. difficult to simplify define. However, weofmust try to use definitions as amortization, inflation, replacement value in order to the concept “value” to improve our decisions. in to simplify the concept of “value” to improve our decisions. In order the case of regulated companies, the economic valuation of the facilities is based on a legal normative, in order to simplify the concept of “value” to improve our decisions. In the case of regulated companies, the economic valuation of the facilities is based on a legal normative, In the case of regulated companies, the economic valuation of the is legal so the concept of “cost” may turn to be quite useless. Therefore, it facilities is important to useon methodology that In case of regulated companies, the economic valuation of theit facilities is based based onaa aamethodology legal normative, normative, so concept of “cost” may turn to be quite useless. Therefore, is important to use that In the case of regulated companies, the economic valuation of the facilities is based on a legal normative, so concept of “cost” may turn to be quite useless. Therefore, it is important to use a methodology that allows us to estimate the value of our assets. We have developed a criticality analysis of our so the concept of “cost” may turn to of be quite useless.We Therefore, it is important to use a methodology that allows us to estimate the value our assets. have developed aa criticality analysis of our so the concept of “cost” may turn tothe berelative quite useless. Therefore, it is important to use a methodology that allows us to estimate the value of our assets. We have developed criticality analysis of our infrastructures in order to assess value of these items for the company. The target is to allows us to estimate theassess value the of relative our assets. We have items developed a criticality analysis of isour infrastructures in order to value of these for the company. The target to allows us to estimate the value of our assets. We have developed a criticality analysis of our infrastructures in order to assess the relative value of these items for the company. The target is to optimize the operation and maintenance (O&M) strategies at a corporate level. This must have a relevant infrastructures in orderand to maintenance assess the relative value of these items for level. the company. The target is to optimize the operation (O&M) strategies at aa corporate This must have aa relevant infrastructures in order to assess the relative value of these items for the company. The target is to optimize the operation and maintenance (O&M) strategies at corporate level. This must have relevant impact in the the operation OPEX of and our company, and(O&M) may bestrategies also an impact in future level. CAPEX. optimize maintenance at a corporate This must have a relevant impact the OPEX our and may also in CAPEX. optimize maintenance at a corporate This must have a relevant impact in in the the operation OPEX of of and our company, company, and(O&M) may be bestrategies also an an impact impact in future future level. CAPEX. impact in the OPEX of our company, and may be also an impact in future CAPEX. This paper discusses theour methodology andmay presents clear examples of howCAPEX. O&M strategy is transformed impact in the OPEX of company, and be also an impact in future This paper discusses the methodology and presents clear examples of how O&M This paper papertodiscusses discusses the methodology and and presents presents clear clear examples examples of of how how O&M O&M strategy strategy is is transformed transformed according criticalitythe assessments. This methodology strategy is transformed according to criticality assessments. This papertodiscusses the methodology and presents clear examples of how O&M strategy is transformed according criticality assessments. according toMaintenance criticality assessments. Keywords: Strategies, Asset and Maintenance Management, management © 2016, IFAC (International FederationAsset of Automatic Control) Hosting by ElsevierLife Ltd.cycle All rights reserved. & according toMaintenance criticality assessments. Keywords: Strategies, and Management, Keywords: Maintenance Strategies, Asset Analysis, and Maintenance Maintenance Management, Life Life cycle cycle management management & & sustainability, Decision Support, Criticality Risk Management Keywords: Maintenance Strategies, Asset and Maintenance Management, Life cycle management & sustainability, Decision Support, Criticality Risk Management Keywords: Maintenance Strategies, Asset Analysis, and Maintenance Management, Life cycle management & sustainability, Decision Support, Criticality Analysis, Risk Management sustainability, Decision Support, Criticality Analysis, Risk Management sustainability, Decision Support, Criticality Analysis, Risk Management methodology and which have been the key points that have methodology and which have been the key points that have 1. INTRODUCTION methodology have the points that allow us to useand it aswhich an indirect measurement value. 1. 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In thisare case, of the times (Crespo Márquez et agreement al., 2016) (based although they most valuable ones? in aa mathematical justification or an based although they are are not the the most most expensive ones, ones, are are not not the the always model most of use the of times Márquez et agreement al., 2016) (based in mathematical justification or an agreement based most valuable ones? on a generally the (Crespo industry). although they are not the most expensive ones, are not the always always in a mathematical justification or an agreement based most valuable ones? on a generally use of the industry). most valuable ones? always in a mathematical justification or an agreement based on a generally use of the industry). 2. THEORETICAL MODEL ADAPTATION most valuable ones? on a generally use of the industry). 2. THEORETICAL MODEL ADAPTATION Despite of this,use when theindustry). methodology has been developed, on a generally of the 2. MODEL ADAPTATION Despite of this, when the methodology has been developed, 2. THEORETICAL THEORETICAL MODEL tries ADAPTATION of this, been Criticality analysis methodology to prioritize the Despite the premise haswhen beenthe thatmethodology the resultshas derived from the 2. THEORETICAL MODEL ADAPTATION Despite of this, when the methodology has been developed, developed, Criticality analysis methodology tries to prioritize the the premise has been that the results derived from the Despite of this, when the methodology has been developed, Criticality analysis methodology tries to prioritize the the premise has been that the results derived from equipment of the facility taking tries in account two main criticality analysis must be aligned with the priorities of Criticality analysis methodology to prioritize the the premise has been that the results derived from the the equipment of the facility taking in account two main criticality analysis must be aligned with the priorities of Criticalitytheanalysis methodology to the prioritize the the premiseanalysis has been that the results derived fromto the equipment of the facility in account two main must be aligned with the priorities of concepts; frequency failuretaking of an tries item, and severity of criticality the company. It implies that methodology must serve the equipment of the facility taking in account two main criticality analysis must be aligned with the priorities of concepts; the frequency failure of an item, and the severity of the company. It implies that methodology must serve to the equipment of the facility taking in account two main criticality analysis must be aligned with the priorities of concepts; the frequency failure of an item, and the severity of the company. It implies that methodology must serve to the the consequence of a hypothetical failure. In this section, we company target,It and not in themethodology opposite way. As serve a result, we concepts; the frequency failure of an item, and the severity of the company. implies that must to the the consequence of aa hypothetical failure. In this section, we target, not in the opposite way. As aa result, we concepts; the frequency failuretheofway an item, and the severitythe of company the company. It and implies that methodology must serve tobeen the the consequence of hypothetical failure. In this section, we company target, and not in the opposite way. As result, we are going to describe shortly we have developed will remark some aspects of the methodology that have the consequence of a shortly hypothetical failure. In this section, the we company target, not inofthe way. As result,been we are going to describe the way we have developed remark someand aspects theopposite methodology thataa have the consequence of a hypothetical failure. In this section, we will company target, and not in the opposite way. As result, we are are going going to to describe describe shortly shortly the the way way we we have have developed developed the the will will remark remark some some aspects aspects of of the the methodology methodology that that have have been been are going to describe shortly the way we have developed the will remark some aspects of the methodology that have been 2405-8963 © 2016, IFAC IFAC (International Federation of Automatic Control) Copyright © 2016 7 Hosting by Elsevier Ltd. All rights reserved. Copyright 2016 7 Peer review© responsibility of International Federation of Automatic Copyright ©under 2016 IFAC IFAC 7 Control. Copyright © 2016 IFAC 7 10.1016/j.ifacol.2016.11.002 Copyright © 2016 IFAC 7
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adapted slightly with the aim that results show as faithfully as we can, the reality of the facility management 2.1 Determine frequency levels and frequency factors The target of criticality analysis is to prioritize assets evaluating its relative importance for the company. The criticality concept is defined as the product of the failure frequency of and item multiplies by the possible consequence of a functional loss:
(CTR = FF *C) The first step is to determine the frequency levels and the frequency factors. Frequency levels let us to differentiate the assets by its failure frequency. Frequency factor is the weight that we assign to each level in order to use it for the criticality calculation.
Acceptable failures
Repetitive failures
Non acceptable failures
In this case, we have defined some concrete values that showed the real management strategy of the company based on the concept of “frequency failures”. This is a clear example of adaptation of the methodology in order to show our real management model. It is known that in this case we will find a higher centralization of assets in a concrete failure frequency (in “possible failure” concept). We preferred to have a distribution of assets that present the reality or our facility. It means that we came from a management style that prioritizes availability to efficiency. It leads to be a little bit over maintained and obviously with a very low failure frequency of our assets.
Acceptable failures; an average value of one failure between two years and one year
Classification
Management definition
2≤f 1≤ f <2 0,5≤ f <1 < 0,5
Very High High Medium Low
Non acceptable failures Repetitive failures Acceptable failures Possible failures
Annual Frequency Failure
Classification
Frequency Factors
2≤f 1≤ f <2 0,5≤ f <1 < 0,5
Very High High Medium Low
2 1,5 1,2 1
2.2 Determine criteria to assess functional loss severity To define criteria to assess functional loss, most of theoretical models propose two main concepts; criteria related with cost and criteria related with safety. In order to assure that methodology is aligned to the company strategy (Crespo Márquez, 2002), we have used the asset management policy of the company as a base for the definition of criteria. This policy is sustained in two main concepts. These concepts are the base of every working line that the company is developing in operation and maintenance. The first base is “integrity”. In this concept are included definitions as personal safety, industrial security and environmental care. The second base is “Efficiency and Improvement” and involved concepts as availability, quality service and maintenance costs.
The frequency factors that define the situation of our items in each level of frequency failure are:
Annual Frequency Failure
Table 2. Frequency Factors
Before fix the frequency factors, we must assign the limits between the different levels of these criteria. Theoretical methods are usually based in mathematical models (e.g. Pareto) that provide us a statistic distribution of the assets in each level. The use of these models guaranteed that all items are distributed equally in the matrix spectrum in order to maximize the sensitivity of the methodology.
Possible failures; an average value lower than one failure every two years
Non acceptable failures; an average value higher than two failures per year
There are many different ways to assign this value. If we had followed the theoretical methodology, this value would be directly related with the limits of the frequency failure defined for each level. In our case, most of the items are in the lowest level of frequency failure. It is logical assuming, as we have exposed before, that during a lot of years we have focused our management model around the concept of availability. So the main aim was to avoid failures doing quite preventive maintenance. To assign values, we start with a single value (“1”) for the lowest level and we increase it gradually for upper levels.
In this case, the classification proposed by the theoretical model is near the same that the one used by the technicians.
Once we have defined each level and the frequency failure that marks the limits, we must assign a failure frequency factor. This value will be the data of each level that allow us to obtain a criticality value.
Most extended models define four frequency levels (low, medium, high and very high). Our technicians translated these theoretical levels into real management concepts: Possible failures
Repetitive failures; an average value between one and two failures per year
Table 1. Frequency Levels
Criticality = Frequency failure * Consequence
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2.3 Determine criteria effects levels The next step is to define the severity levels for each criterion. These levels will measure the gravity of the consequences of a failure. In the same way that we have defined the failure frequency levels, the first step is to assess how many different levels must be defined for each criterion. We have assumed that four levels is an optimum decision to make precise and massive analysis. For each criterion, we must define the consequences that a functional loss implies in every level. Each definition must be as simple and explicit as possible. If we are able to define it very simply, we will limit the possible debates in the workgroup.
Fig. 1. : Summary of asset management policy To connect criteria proposed by methodology with the asset management policy of the company, we have defined five analysis criteria based in these two pillars. Two of them are related whit integrity and the other three are related with efficiency. It is important to remark that criteria related with costs don’t imply directly “spend money” or “profit lost”. These criteria can be related with reputational lost, stakeholder’s repercussion or even hypothetical penalties for service loss (the reader can refer to Wireman [1998] to review performance indicators to manage maintenance).
The criteria effects levels defined are:: Safety Criteria I; Industrial Safety
External impact on the facility in a inhabitable or vulnerable area or with fatalities or permanent disabilities; (Catastrophic)
High impact on the facility extinguished with external resources or external damage to an invulnerable area; or serious injury causing prolonged temporary disability; (Critical)
High impact on the facility extinguished with internal resources, or minor and reversible injuries to workers; (Moderate)
Slight impact on the facility extinguished with internal resources; or slight injury that does not affect the work; (No impact/Slight)
The criteria defined for consequence analysis are: Safety Criteria:
Industrial safety: The industrial safety factor assesses the consequences of the functional loss of an element related with: o
Injuries to internal or third party personnel in the facility, and/or any other person who could be involved in.
o
Damage to industrial assets, products and materials used in production.
Safety Criteria II; Environmental
Environmental Care: The environmental factor assesses the environmental consequences of the functional loss of an element, including recovery costs, penalties, compensation, etc.
Cost criteria:
Quality service: The quality service factor assesses the impact of the functional loss of an element on the gas reception, delivery service conditions, and any other services that Enagas offers to its clients.
Availability: The availability factor assesses the impact of the functional loss of an element on the installation’s nominal capacity.
External impact on the facility in an inhabitable or vulnerable area (High)
High impact on the facility mitigated with external resources or external damage in an invulnerable area (Medium)
Average or low impact on the facility mitigated with internal resources (Low)
No Impact (No Impact)
Cost Criteria I; Quality Service
Maintenance costs: The maintenance cost factor assesses the impact of the functional loss of an element on the corrective maintenance costs, including costs related with the recovery of the equipment and other equipment that may have been damaged. 9
Immediate lack of service (High)
Loss of critical parameter of gas quality (measure, dust, odorization…) (Medium)
Loss of non-critical parameters of gas quality (pressure, temperature) (Low)
No impact (No Impact)
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Cost Criteria II; Availability
Installation shutdown. Total or main operating loss (Very High)
Loss of nominal capacity of facility (High)
Loss of redundancy capacity of facility (Medium)
No impact (Low)
Cost Criteria III; Maintenance Cost
Maintenance costs derivate from functional loss upper 30.000€ (Very High)
Maintenance costs derivate from functional loss between 5.000€ and 30.000€ (High)
Maintenance costs derivate from functional loss between 600€ and 5.000€ (Medium)
Maintenance costs derivate from functional loss lower than 600€ (Low)
The policy is divided in two main bases, so is logical to distribute equitably the weigh among each of those two pillars; 50% for safety criteria (related with main base of integrity) and 50% for cost criteria (related with efficiency and improvement base)
In safety criteria, we decided to assign more weight to personal safety criteria face to environmental, because personal safety implies human consequences.
In criteria related with cost, it is decided to assign more weight when consequences could have more structural impact, otherwise it could be a long term consequence (reputational impact, stakeholders impact) face to other criteria that could have a more pure economical consequence in short term (as maintenance costs itself).
At the end we get a table as follows:: Table 3. Criteria weigh Main Base Criteria Industrial Environ Safety mental
2.4 Determine non-admissible effect levels At this point, the process requires the definition of those functional loss effects that will be fixed as “non- admissible” for us. It implies to decide in what factor we apply this concept. This characteristic allocates the valued item into the maximum punctuation in consequence (100 in our case) independently of the rest of the assessment.
35%
15%
Quality Service
25%
50%
Secondary Base Criteria Availability Maintenance Costs
20% 50%
5%
2.6 Determine severity per criteria effect The last point to get our assessment table is to fix the severity per criteria effect. As we have done with every criterion, the aim is to assign numeric value for each severity level in order to get a final mark that let us to calculate the criticality level.
Looking back at our asset management policy, we apply this “non-admissible” condition just in the factors that are related with safety criteria and with the main base: integrity. We define as non-admissible consequence, the maximum level of severity in industrial safety and environmental criteria.
Industrial safety: External impact on the facility in a inhabitable or vulnerable area or with fatalities or permanent disabilities
There is no specific method to assign this value, but there are some recommendations, as try to assess the consequences of a possible functional loss in an economical way. After getting these values, you can compare them and fix a more logical distribution of weighs. If two consecutive severity levels have approximately double consequences costs, is logical to assume that we can fix a double weigh for the severity value.
Environmental: External impact on the facility in an inhabitable or vulnerable area
Including every assumption that the workgroup has imagined, the result is the next table:
So we assumed that are not admissible for us the next consequences:
Table 4. Severity per safety criteria
2.5 Criteria weights in the functional loss severity
Safety Criteria
Other key point for the effectiveness of the methodology is a coherent definition of the weights for assessing a functional loss. Criticality analysis is a semi-quantitative method, so the way we turn consequences into marks will be determinant for the results of the analysis.
Industrial Safety
It is know that there is an important subjective component in the definitions used for the assessment. But with the bases of the policy and the common sense, is easier to assess the importance of a consequence for the company. We can describe some premises as example:
10
Environmental
Catastrophic
100
High
100
Critical
35
Medium
15
Moderate
20
Low
5
Slight
0
No Impact
0
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Table 5. Severity per cost criteria
3. VALUE OF CRITICALITY
Cost Criteria
After an assessment of all items of a facility we get the matrix criticality shown in the figure. In this case, we have analysed more than one hundred and fifty items. The difficulty of the assessment is to think about the possible consequence of a functional loss of a concrete item in every criterion. Workgroup must assign the mark of the severity criteria if the possible consequences agree with the definition of this severity criteria level.
Quality Service
Availability
High
25
Medium Low No Impact
Maintenance Costs Very High
5
Very High
20
15
High
10
High
4
5
Medium
5
Medium
3
0
Low
0
Low
1
One of the key points in the methodology is that we don’t care about the prize of the item. Even we don’t care about the replacement costs of the item. These are concepts that are not considered into criticality concept. At this point, is shocking to discover that these criteria are not directly related with the function of the item.
2.7 Determine criticality limits The last step is to calculate the criticality and to obtain the graphical display on criticality matrix. Multiplying frequency failure factor (remember that it is the value we have assign to each level and not the value of frequency failure itself) plus consequence assessment, we obtain a non-dimensional value that represent the criticality level. Following the theoretical models, we have defined three criticality levels. The limits fixed among the different levels are: •
Limit of low-medium criticality: 50 units
•
Limit of medium-high criticality: 90 units
The strength of the methodology is that we have obtained quite an objective assessment of the value of the equipment from the company, starting out from a subjective analysis of possible failure consequences. The criticality matrix is not a target itself. We have used the methodology as a tool for optimising cost opex lifecycle. The main point for us is to consider this methodology into a general continuous improvement model. In this line, the Maintenance Management Model proposed by Ingeman (referred) suggests different maintenance engineering methodologies to develop in function of the relative position of the equipment into the matrix. In other words, the Model suggests different methodologies in function of the relative value of the equipment for the company.
With the three values of the equation, we can picture the item into the matrix criticality. The matrix used for the development of the methodology has as dimensions 4*10 (rows by columns). The value of frequency failure is fixed in Y axis. The value of consequence failure is fixed in X axis. This value is obtained as the result of the equation IS+E+QS+A+MC. The assessment of the severity of each criterion must be turned into the weights assignment for each level. In the graphical model, the number of items that are classified in a concrete cell of the matrix is indicated into the cell.
For example, for that equipment with a high value of criticality (high consequences and high failure frequency) a failure root cost analysis (FRCA) is proposed. This methodology probably won’t be able to decrease our maintenance costs or optimise our maintenance plan, but we will be able to limit unscheduled stops in critical systems. As a result, we will avoid problems with our clients or the availability of the facility. As the reader can deduce, this assessment is indirectly done in the criteria definition.
Criticality matrix used for the example let us to distribute the equipment among three areas: •
Non critical area (blank zone)
•
Semi-critical area (soft grey zone)
•
Critical area (dark grey zone)
For non-critical equipment, the methodology suggests you a Risk-Cost Optimization (RCO). We have also adapted this methodology in order to review all maintenance plans of noncritical equipment. In a first phase we have focused the efforts in lighten frequency of preventive maintenance. As a consequence, we hope to have an important decrease of our maintenance budget. But the most important point is that we hope to obtain a deeper knowledge of our failure mode equipment. Coming from an intensive preventive maintenance plan, most of the times we avoid the failure, which is probable the most comfortable point, but not the most efficient one. If we have an analysis that let us run to failure or at least reduce the preventive maintenance to these items that are non-critical for the company, we were able to manage the facility from a safe situation into an efficient one.
Table 6. Criticality Matrix FF 2 2
1,5
3
1
2
1,2
11
1
1
57
35
20
15
3
1
5
1
9
12
C
010
1020
2030
3040
4050
5060
6070
7080
8090
90100
11
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4. CONCLUSIONS To limit the concept of value to cost terms is to limit the capability of the asset management. Depends on the nature and the specific sector of the company, many other factors must be taken in account. Criticality analysis allows allocating with a simple methodology your items assigning them a relative value in function of the strategy and target of the company. It is a very powerful tool and a solid starting point for an optimising policy of OPEX in the lifecycle.
5. REFERENCES Crespo Márquez, A., Moreu de León, P., Sola Rosique, A. and Gómez Fernández, J.F. (2016). Criticality Analysis for Maintenance Purposes: A Study for Complex Inservice Engineering Assets. Qual. Reliab. Eng. Int. 32, 519-533. Crespo Márquez, A. (2007). The Maintenance Management Framework: Models and Methods for Complex Systems Maintenance. Springer-verlag. London. Puente, J., Pino, R., Priore, P., De la Fuente, D. (2002). A decision support system for applying failure mode and effects analysis. Int. J. Qual. Reliab. Manag. 19(2), 137–150. Moss, T.R., Woodhouse, J. (1999). Criticality analysis revisited. Qual. Reliab. Eng. Int. 15, 117–121. EN 13306:2010. (2010). Maintenance terminology. European Standard. CEN (European Committee for Standardization). Brussels. Wireman, T. (1998). Developing Performance Indicators for Managing Maintenance. Industrial Press. New York.
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Criticality Analysis for optimising OPEX cost lifecycle Criticality Analysis for optimising OPEX cost lifecycle Criticality Analysis for optimising OPEX cost lifecycle Criticality optimising OPEX cost lifecycle Criticality Analysis Analysis for for optimising OPEX cost lifecycle Serra Parajes, Javier*
Serra Parajes, Parajes, Javier* Javier* Serra Adolfo Márquez** SerraCrespo Parajes, Javier* Adolfo Crespo Márquez** Serra Parajes, Javier* Adolfo Crespo Márquez** Antonio Sola Rosique*** Adolfo Crespo Márquez** Antonio Sola Rosique*** Rosique*** Adolfo Crespo Márquez** Antonio Sola Antonio Sola Rosique*** Antonio SolaEnagas, Rosique*** *Asset Management Coordinator, Madrid, [email protected] *Asset Management Coordinator, Enagas, Madrid, [email protected] *Asset Management Coordinator, Enagas, Madrid, [email protected] **Escuela técnica de ingenieros de la Universidad de Sevilla [email protected] *Asset Management Coordinator, Enagas, Madrid, [email protected] **Escuela técnica de ingenieros de la Universidad de Sevilla [email protected] *Asset Management Coordinator, Enagas, Madrid, [email protected] **Escuela técnica de ingenieros de la Universidad de Sevilla [email protected] **Escuela técnica de ingenieros de la Universidad de Sevilla [email protected] **Escuela técnica de ingenieros de la Universidad de Sevilla [email protected] Abstract: Identification and quantification of cost and value of industrial assets is a field in which much Abstract: Identification and quantification of cost and value of industrial assets is aa field in which much Abstract: and of and value assets in much terminology is mixed. When we try to analyze the importance of an asset for is our business, to discuss Abstract: Identification Identification and quantification quantification of cost costthe andimportance value of of industrial industrial assets isour a field field in which which much terminology is mixed. When we try to analyze of an asset for business, to discuss Abstract: Identification and quantification of cost and value of industrial assets is a field in which much terminology is mixed. When we try to analyze the importance of an asset for our business, to discuss about its costsis should not be separated from the value provided byofthe asset. Most of business, the times, to managers terminology mixed. When we try to analyze the importance an asset for our discuss about its costs should not be separated from the value provided by the asset. Most of the times, managers terminology is mixed. When we try to analyze the importance of an asset for our business, to discuss about its costs should not be separated from the value provided by the asset. Most of the times, managers only use the term “cost” because it seems to be more objective. Value isMost moreofsubjective and more about its costs should not be separated from the value provided by the asset.is the times, and managers only use the term “cost” because it seems to be more objective. Value more more about its to costs should not be separated from value provided by the asset.isMost ofsubjective the times, and managers only use the term “cost” because it seems to be more objective. Value more subjective more difficult define. However, we must try to the use definitions as amortization, inflation, replacement value only use the term “cost” because it seems to be more objective. Value is more subjective and more difficult to define. we must try to use definitions as amortization, replacement only useto the term However, “cost” because it seems to be more Value isinflation, more subjective and value more difficult to define. we try definitions as in order simplify the concept ofmust “value” to use improve our objective. decisions. difficult to simplify define. However, However, weof must try to to use definitions as amortization, amortization, inflation, inflation, replacement replacement value value in order to the concept “value” to improve our decisions. difficult to simplify define. However, weofmust try to use definitions as amortization, inflation, replacement value in order to the concept “value” to improve our decisions. in to simplify the concept of “value” to improve our decisions. In order the case of regulated companies, the economic valuation of the facilities is based on a legal normative, in order to simplify the concept of “value” to improve our decisions. In the case of regulated companies, the economic valuation of the facilities is based on a legal normative, In the case of regulated companies, the economic valuation of the is legal so the concept of “cost” may turn to be quite useless. Therefore, it facilities is important to useon methodology that In case of regulated companies, the economic valuation of theit facilities is based based onaa aamethodology legal normative, normative, so concept of “cost” may turn to be quite useless. Therefore, is important to use that In the case of regulated companies, the economic valuation of the facilities is based on a legal normative, so concept of “cost” may turn to be quite useless. Therefore, it is important to use a methodology that allows us to estimate the value of our assets. We have developed a criticality analysis of our so the concept of “cost” may turn to of be quite useless.We Therefore, it is important to use a methodology that allows us to estimate the value our assets. have developed aa criticality analysis of our so the concept of “cost” may turn tothe berelative quite useless. Therefore, it is important to use a methodology that allows us to estimate the value of our assets. We have developed criticality analysis of our infrastructures in order to assess value of these items for the company. The target is to allows us to estimate theassess value the of relative our assets. We have items developed a criticality analysis of isour infrastructures in order to value of these for the company. The target to allows us to estimate the value of our assets. We have developed a criticality analysis of our infrastructures in order to assess the relative value of these items for the company. The target is to optimize the operation and maintenance (O&M) strategies at a corporate level. This must have a relevant infrastructures in orderand to maintenance assess the relative value of these items for level. the company. The target is to optimize the operation (O&M) strategies at aa corporate This must have aa relevant infrastructures in order to assess the relative value of these items for the company. The target is to optimize the operation and maintenance (O&M) strategies at corporate level. This must have relevant impact in the the operation OPEX of and our company, and(O&M) may bestrategies also an impact in future level. CAPEX. optimize maintenance at a corporate This must have a relevant impact the OPEX our and may also in CAPEX. optimize maintenance at a corporate This must have a relevant impact in in the the operation OPEX of of and our company, company, and(O&M) may be bestrategies also an an impact impact in future future level. CAPEX. impact in the OPEX of our company, and may be also an impact in future CAPEX. This paper discusses theour methodology andmay presents clear examples of howCAPEX. O&M strategy is transformed impact in the OPEX of company, and be also an impact in future This paper discusses the methodology and presents clear examples of how O&M This paper papertodiscusses discusses the methodology and and presents presents clear clear examples examples of of how how O&M O&M strategy strategy is is transformed transformed according criticalitythe assessments. This methodology strategy is transformed according to criticality assessments. This papertodiscusses the methodology and presents clear examples of how O&M strategy is transformed according criticality assessments. according toMaintenance criticality assessments. Keywords: Strategies, Asset and Maintenance Management, management © 2016, IFAC (International FederationAsset of Automatic Control) Hosting by ElsevierLife Ltd.cycle All rights reserved. & according toMaintenance criticality assessments. Keywords: Strategies, and Management, Keywords: Maintenance Strategies, Asset Analysis, and Maintenance Maintenance Management, Life Life cycle cycle management management & & sustainability, Decision Support, Criticality Risk Management Keywords: Maintenance Strategies, Asset and Maintenance Management, Life cycle management & sustainability, Decision Support, Criticality Risk Management Keywords: Maintenance Strategies, Asset Analysis, and Maintenance Management, Life cycle management & sustainability, Decision Support, Criticality Analysis, Risk Management sustainability, Decision Support, Criticality Analysis, Risk Management sustainability, Decision Support, Criticality Analysis, Risk Management methodology and which have been the key points that have methodology and which have been the key points that have 1. INTRODUCTION methodology have the points that allow us to useand it aswhich an indirect measurement value. 1. INTRODUCTION methodology and which have been been the key key of points that have have 1. INTRODUCTION allow us to use it as an indirect measurement of value. methodology and which have been the key of points that have us to use it as an indirect measurement value. In this paper, we 1. tryINTRODUCTION to explain how we have used the allow allow us to use it as an indirect measurement of value. 1. INTRODUCTION process follows theindirect next steps: In this paper, we try to explain how we have used the The us to use it as an measurement of value. In we try to we The process follows the next steps: criticality analysis purposes as a used base the for allow In this this paper, paper, we for try maintenance to explain explain how how we have have used the The process follows the next steps: criticality analysis for maintenance purposes as a base for The process follows the next steps: In this paper, we try to explain how we have used the criticality analysis for maintenance purposes as a base for different working lines of operation and asmaintenance. Determine frequency levels and the frequency follows the next steps: criticality analysis for maintenance purposes a base for The process different working lines of operation and frequency levels and the frequency criticality analysis maintenance purposes asmaintenance. base for different working lines and maintenance. Determine Determine frequency levels Although the main for target ofof theoperation methodology is toa optimize factors different working lines of operation and maintenance. Determine frequency levels and and the the frequency frequency Although the main target of the methodology is to optimize factors different working lines of operation and maintenance. factors Determine frequency levels and the frequency Although the main target of the methodology to optimize the maintenance strategies (as defined in EN is 13306:2010), Although the main target of the methodology is to optimize factors the maintenance strategies in EN Determine criteria to assess functional loss severity Although the of main target of(as thedefined methodology is13306:2010), to optimize the maintenance strategies (as EN the concept criticality us toin an indirect factors Determine criteria to assess functional loss severity the maintenance strategies allows (as defined defined inobtain EN 13306:2010), 13306:2010), Determine criteria to functional the concept of criticality allows us to obtain an indirect the maintenance strategies (as defined in EN 13306:2010), the concept of criticality allows us to obtain an indirect Determine Determine criteria criteria effect to assess assess functional loss loss severity severity value of our facilities. the concept of criticality allows us to obtain an indirect levels to assess functional loss severity value of our our facilities. facilities. the concept of criticality allows us to obtain an indirect Determine criteria effect levels value of Determine criteria effect levels value of our facilities. Determine criteria effect levels The adaptation of the theoretical methodology to make it value of our facilities. Determine non-admissible functional loss effects criteria effect levels The adaptation of the theoretical methodology to make it The adaptation of the theoretical methodology to make it Determine non-admissible functional loss effects confluence with the company strategy provides you an Determine non-admissible functional loss The adaptation of the theoretical methodology to make it Determine non-admissible functional loss effects effects loss confluence withofthe the company strategy provides you an an The adaptation the company theoretical methodology to make it confluence with strategy provides you Determine criteria weights in the functional non-admissible functional loss effects loss analysis of the importance of the equipment. The study of the confluence with the company strategy provides you an Determine criteria weights in the functional analysis of the importance of the equipment. The study of the Determine criteria weights in the functional loss confluence with the company strategy provides you an analysis of the importance of the equipment. The study of the severity consequences of a functional loss and the frequency of these Determine criteria weights in the functional loss analysis of theof importance of the equipment. The study of the consequences aa functional loss and the frequency of these severity Determine criteria weights in the functional loss severity analysis of the importance of the equipment. The study of the consequences of functional loss and the frequency of these failures approach us to the concept ofthe relative valueofofthese the severity consequences of a functional loss and frequency Determine severity per criteria effect failures approach to the concept relative valueofof the severity consequences a us functional loss andof the frequency these failures approach us to concept of relative of Determine severity severity per per criteria criteria effect effect asset (Puente etofal, 2002; Moss et al., 1999). The value most critical failures approach us to the the concept of relative value of the the Determine asset (Puente et al, 2002; Moss et al., 1999). The most critical Determine criticality severity per criteria effect failures approach us to the concept of relative value of the asset al, 2002; Moss et al., 1999). The most items (Puente won’t beet probably the most expensive ones, evencritical won’t Determine limits severity per criteria effect asset (Puente et al, 2002; Moss et al., 1999). The most critical items won’t be the most expensive ones, even won’t Determine criticality limits asset etprobably al,with 2002;the Moss et al., 1999). Themost most critical items won’t be probably the most expensive ones, even won’t Determine criticality limits be the(Puente equipment maintenance plans detailed, items won’t be probably the most expensive ones, even won’t Determine criticality limits be thewon’t equipment with the plans most detailed, process of the criticality work team for the development of the items themaintenance most ones, even won’t Determine limits be the plans most detailed, but the theyequipment willbe beprobably thewith equipment in expensive which we spend time The The process process of the the work work team team for the the development development of of the the be the equipment with the maintenance maintenance plans mostmore detailed, The of for but they will be the equipment in which we spend more time project has followed the steps defined in the theoretical be the equipment with the maintenance plans most detailed, but they will the equipment which we process of the work team for the development of the and efforts tobe make them workin properly. Inspend this more case, time and The project has followed the steps defined in the theoretical but they will be the equipment in which we spend more time The process of the work team for the development of the project has followed the steps defined in the theoretical and efforts tobemake make them work workinproperly. properly. Inspend this more case, time and project model most the timesthe (Crespo (based but they will thenot equipment which weIn has of followed steps Márquez defined et inal., the2016) theoretical and efforts to them this case, although they are the work most expensive ones, are notand the model most of the times (Crespo Márquez et al., 2016) (based and efforts to make them properly. In this case, and project has followed the steps defined in the theoretical model most of the times (Crespo Márquez et al., 2016) (based although they are not not the work most expensive expensive ones, notand the model alwaysmost in a mathematical justification or an based and efforts to make them properly. In thisare case, of the times (Crespo Márquez et agreement al., 2016) (based although they most valuable ones? in aa mathematical justification or an based although they are are not the the most most expensive ones, ones, are are not not the the always model most of use the of times Márquez et agreement al., 2016) (based in mathematical justification or an agreement based most valuable ones? on a generally the (Crespo industry). although they are not the most expensive ones, are not the always always in a mathematical justification or an agreement based most valuable ones? on a generally use of the industry). most valuable ones? always in a mathematical justification or an agreement based on a generally use of the industry). 2. THEORETICAL MODEL ADAPTATION most valuable ones? on a generally use of the industry). 2. THEORETICAL MODEL ADAPTATION Despite of this,use when theindustry). methodology has been developed, on a generally of the 2. MODEL ADAPTATION Despite of this, when the methodology has been developed, 2. THEORETICAL THEORETICAL MODEL tries ADAPTATION of this, been Criticality analysis methodology to prioritize the Despite the premise haswhen beenthe thatmethodology the resultshas derived from the 2. THEORETICAL MODEL ADAPTATION Despite of this, when the methodology has been developed, developed, Criticality analysis methodology tries to prioritize the the premise has been that the results derived from the Despite of this, when the methodology has been developed, Criticality analysis methodology tries to prioritize the the premise has been that the results derived from equipment of the facility taking tries in account two main criticality analysis must be aligned with the priorities of Criticality analysis methodology to prioritize the the premise has been that the results derived from the the equipment of the facility taking in account two main criticality analysis must be aligned with the priorities of Criticalitytheanalysis methodology to the prioritize the the premiseanalysis has been that the results derived fromto the equipment of the facility in account two main must be aligned with the priorities of concepts; frequency failuretaking of an tries item, and severity of criticality the company. It implies that methodology must serve the equipment of the facility taking in account two main criticality analysis must be aligned with the priorities of concepts; the frequency failure of an item, and the severity of the company. It implies that methodology must serve to the equipment of the facility taking in account two main criticality analysis must be aligned with the priorities of concepts; the frequency failure of an item, and the severity of the company. It implies that methodology must serve to the the consequence of a hypothetical failure. In this section, we company target,It and not in themethodology opposite way. As serve a result, we concepts; the frequency failure of an item, and the severity of the company. implies that must to the the consequence of aa hypothetical failure. In this section, we target, not in the opposite way. As aa result, we concepts; the frequency failuretheofway an item, and the severitythe of company the company. It and implies that methodology must serve tobeen the the consequence of hypothetical failure. In this section, we company target, and not in the opposite way. As result, we are going to describe shortly we have developed will remark some aspects of the methodology that have the consequence of a shortly hypothetical failure. In this section, the we company target, not inofthe way. As result,been we are going to describe the way we have developed remark someand aspects theopposite methodology thataa have the consequence of a hypothetical failure. In this section, we will company target, and not in the opposite way. As result, we are are going going to to describe describe shortly shortly the the way way we we have have developed developed the the will will remark remark some some aspects aspects of of the the methodology methodology that that have have been been are going to describe shortly the way we have developed the will remark some aspects of the methodology that have been 2405-8963 © 2016, IFAC IFAC (International Federation of Automatic Control) Copyright © 2016 7 Hosting by Elsevier Ltd. All rights reserved. Copyright 2016 7 Peer review© responsibility of International Federation of Automatic Copyright ©under 2016 IFAC IFAC 7 Control. Copyright © 2016 IFAC 7 10.1016/j.ifacol.2016.11.002 Copyright © 2016 IFAC 7
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adapted slightly with the aim that results show as faithfully as we can, the reality of the facility management 2.1 Determine frequency levels and frequency factors The target of criticality analysis is to prioritize assets evaluating its relative importance for the company. The criticality concept is defined as the product of the failure frequency of and item multiplies by the possible consequence of a functional loss:
(CTR = FF *C) The first step is to determine the frequency levels and the frequency factors. Frequency levels let us to differentiate the assets by its failure frequency. Frequency factor is the weight that we assign to each level in order to use it for the criticality calculation.
Acceptable failures
Repetitive failures
Non acceptable failures
In this case, we have defined some concrete values that showed the real management strategy of the company based on the concept of “frequency failures”. This is a clear example of adaptation of the methodology in order to show our real management model. It is known that in this case we will find a higher centralization of assets in a concrete failure frequency (in “possible failure” concept). We preferred to have a distribution of assets that present the reality or our facility. It means that we came from a management style that prioritizes availability to efficiency. It leads to be a little bit over maintained and obviously with a very low failure frequency of our assets.
Acceptable failures; an average value of one failure between two years and one year
Classification
Management definition
2≤f 1≤ f <2 0,5≤ f <1 < 0,5
Very High High Medium Low
Non acceptable failures Repetitive failures Acceptable failures Possible failures
Annual Frequency Failure
Classification
Frequency Factors
2≤f 1≤ f <2 0,5≤ f <1 < 0,5
Very High High Medium Low
2 1,5 1,2 1
2.2 Determine criteria to assess functional loss severity To define criteria to assess functional loss, most of theoretical models propose two main concepts; criteria related with cost and criteria related with safety. In order to assure that methodology is aligned to the company strategy (Crespo Márquez, 2002), we have used the asset management policy of the company as a base for the definition of criteria. This policy is sustained in two main concepts. These concepts are the base of every working line that the company is developing in operation and maintenance. The first base is “integrity”. In this concept are included definitions as personal safety, industrial security and environmental care. The second base is “Efficiency and Improvement” and involved concepts as availability, quality service and maintenance costs.
The frequency factors that define the situation of our items in each level of frequency failure are:
Annual Frequency Failure
Table 2. Frequency Factors
Before fix the frequency factors, we must assign the limits between the different levels of these criteria. Theoretical methods are usually based in mathematical models (e.g. Pareto) that provide us a statistic distribution of the assets in each level. The use of these models guaranteed that all items are distributed equally in the matrix spectrum in order to maximize the sensitivity of the methodology.
Possible failures; an average value lower than one failure every two years
Non acceptable failures; an average value higher than two failures per year
There are many different ways to assign this value. If we had followed the theoretical methodology, this value would be directly related with the limits of the frequency failure defined for each level. In our case, most of the items are in the lowest level of frequency failure. It is logical assuming, as we have exposed before, that during a lot of years we have focused our management model around the concept of availability. So the main aim was to avoid failures doing quite preventive maintenance. To assign values, we start with a single value (“1”) for the lowest level and we increase it gradually for upper levels.
In this case, the classification proposed by the theoretical model is near the same that the one used by the technicians.
Once we have defined each level and the frequency failure that marks the limits, we must assign a failure frequency factor. This value will be the data of each level that allow us to obtain a criticality value.
Most extended models define four frequency levels (low, medium, high and very high). Our technicians translated these theoretical levels into real management concepts: Possible failures
Repetitive failures; an average value between one and two failures per year
Table 1. Frequency Levels
Criticality = Frequency failure * Consequence
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9
2.3 Determine criteria effects levels The next step is to define the severity levels for each criterion. These levels will measure the gravity of the consequences of a failure. In the same way that we have defined the failure frequency levels, the first step is to assess how many different levels must be defined for each criterion. We have assumed that four levels is an optimum decision to make precise and massive analysis. For each criterion, we must define the consequences that a functional loss implies in every level. Each definition must be as simple and explicit as possible. If we are able to define it very simply, we will limit the possible debates in the workgroup.
Fig. 1. : Summary of asset management policy To connect criteria proposed by methodology with the asset management policy of the company, we have defined five analysis criteria based in these two pillars. Two of them are related whit integrity and the other three are related with efficiency. It is important to remark that criteria related with costs don’t imply directly “spend money” or “profit lost”. These criteria can be related with reputational lost, stakeholder’s repercussion or even hypothetical penalties for service loss (the reader can refer to Wireman [1998] to review performance indicators to manage maintenance).
The criteria effects levels defined are:: Safety Criteria I; Industrial Safety
External impact on the facility in a inhabitable or vulnerable area or with fatalities or permanent disabilities; (Catastrophic)
High impact on the facility extinguished with external resources or external damage to an invulnerable area; or serious injury causing prolonged temporary disability; (Critical)
High impact on the facility extinguished with internal resources, or minor and reversible injuries to workers; (Moderate)
Slight impact on the facility extinguished with internal resources; or slight injury that does not affect the work; (No impact/Slight)
The criteria defined for consequence analysis are: Safety Criteria:
Industrial safety: The industrial safety factor assesses the consequences of the functional loss of an element related with: o
Injuries to internal or third party personnel in the facility, and/or any other person who could be involved in.
o
Damage to industrial assets, products and materials used in production.
Safety Criteria II; Environmental
Environmental Care: The environmental factor assesses the environmental consequences of the functional loss of an element, including recovery costs, penalties, compensation, etc.
Cost criteria:
Quality service: The quality service factor assesses the impact of the functional loss of an element on the gas reception, delivery service conditions, and any other services that Enagas offers to its clients.
Availability: The availability factor assesses the impact of the functional loss of an element on the installation’s nominal capacity.
External impact on the facility in an inhabitable or vulnerable area (High)
High impact on the facility mitigated with external resources or external damage in an invulnerable area (Medium)
Average or low impact on the facility mitigated with internal resources (Low)
No Impact (No Impact)
Cost Criteria I; Quality Service
Maintenance costs: The maintenance cost factor assesses the impact of the functional loss of an element on the corrective maintenance costs, including costs related with the recovery of the equipment and other equipment that may have been damaged. 9
Immediate lack of service (High)
Loss of critical parameter of gas quality (measure, dust, odorization…) (Medium)
Loss of non-critical parameters of gas quality (pressure, temperature) (Low)
No impact (No Impact)
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Cost Criteria II; Availability
Installation shutdown. Total or main operating loss (Very High)
Loss of nominal capacity of facility (High)
Loss of redundancy capacity of facility (Medium)
No impact (Low)
Cost Criteria III; Maintenance Cost
Maintenance costs derivate from functional loss upper 30.000€ (Very High)
Maintenance costs derivate from functional loss between 5.000€ and 30.000€ (High)
Maintenance costs derivate from functional loss between 600€ and 5.000€ (Medium)
Maintenance costs derivate from functional loss lower than 600€ (Low)
The policy is divided in two main bases, so is logical to distribute equitably the weigh among each of those two pillars; 50% for safety criteria (related with main base of integrity) and 50% for cost criteria (related with efficiency and improvement base)
In safety criteria, we decided to assign more weight to personal safety criteria face to environmental, because personal safety implies human consequences.
In criteria related with cost, it is decided to assign more weight when consequences could have more structural impact, otherwise it could be a long term consequence (reputational impact, stakeholders impact) face to other criteria that could have a more pure economical consequence in short term (as maintenance costs itself).
At the end we get a table as follows:: Table 3. Criteria weigh Main Base Criteria Industrial Environ Safety mental
2.4 Determine non-admissible effect levels At this point, the process requires the definition of those functional loss effects that will be fixed as “non- admissible” for us. It implies to decide in what factor we apply this concept. This characteristic allocates the valued item into the maximum punctuation in consequence (100 in our case) independently of the rest of the assessment.
35%
15%
Quality Service
25%
50%
Secondary Base Criteria Availability Maintenance Costs
20% 50%
5%
2.6 Determine severity per criteria effect The last point to get our assessment table is to fix the severity per criteria effect. As we have done with every criterion, the aim is to assign numeric value for each severity level in order to get a final mark that let us to calculate the criticality level.
Looking back at our asset management policy, we apply this “non-admissible” condition just in the factors that are related with safety criteria and with the main base: integrity. We define as non-admissible consequence, the maximum level of severity in industrial safety and environmental criteria.
Industrial safety: External impact on the facility in a inhabitable or vulnerable area or with fatalities or permanent disabilities
There is no specific method to assign this value, but there are some recommendations, as try to assess the consequences of a possible functional loss in an economical way. After getting these values, you can compare them and fix a more logical distribution of weighs. If two consecutive severity levels have approximately double consequences costs, is logical to assume that we can fix a double weigh for the severity value.
Environmental: External impact on the facility in an inhabitable or vulnerable area
Including every assumption that the workgroup has imagined, the result is the next table:
So we assumed that are not admissible for us the next consequences:
Table 4. Severity per safety criteria
2.5 Criteria weights in the functional loss severity
Safety Criteria
Other key point for the effectiveness of the methodology is a coherent definition of the weights for assessing a functional loss. Criticality analysis is a semi-quantitative method, so the way we turn consequences into marks will be determinant for the results of the analysis.
Industrial Safety
It is know that there is an important subjective component in the definitions used for the assessment. But with the bases of the policy and the common sense, is easier to assess the importance of a consequence for the company. We can describe some premises as example:
10
Environmental
Catastrophic
100
High
100
Critical
35
Medium
15
Moderate
20
Low
5
Slight
0
No Impact
0
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Table 5. Severity per cost criteria
3. VALUE OF CRITICALITY
Cost Criteria
After an assessment of all items of a facility we get the matrix criticality shown in the figure. In this case, we have analysed more than one hundred and fifty items. The difficulty of the assessment is to think about the possible consequence of a functional loss of a concrete item in every criterion. Workgroup must assign the mark of the severity criteria if the possible consequences agree with the definition of this severity criteria level.
Quality Service
Availability
High
25
Medium Low No Impact
Maintenance Costs Very High
5
Very High
20
15
High
10
High
4
5
Medium
5
Medium
3
0
Low
0
Low
1
One of the key points in the methodology is that we don’t care about the prize of the item. Even we don’t care about the replacement costs of the item. These are concepts that are not considered into criticality concept. At this point, is shocking to discover that these criteria are not directly related with the function of the item.
2.7 Determine criticality limits The last step is to calculate the criticality and to obtain the graphical display on criticality matrix. Multiplying frequency failure factor (remember that it is the value we have assign to each level and not the value of frequency failure itself) plus consequence assessment, we obtain a non-dimensional value that represent the criticality level. Following the theoretical models, we have defined three criticality levels. The limits fixed among the different levels are: •
Limit of low-medium criticality: 50 units
•
Limit of medium-high criticality: 90 units
The strength of the methodology is that we have obtained quite an objective assessment of the value of the equipment from the company, starting out from a subjective analysis of possible failure consequences. The criticality matrix is not a target itself. We have used the methodology as a tool for optimising cost opex lifecycle. The main point for us is to consider this methodology into a general continuous improvement model. In this line, the Maintenance Management Model proposed by Ingeman (referred) suggests different maintenance engineering methodologies to develop in function of the relative position of the equipment into the matrix. In other words, the Model suggests different methodologies in function of the relative value of the equipment for the company.
With the three values of the equation, we can picture the item into the matrix criticality. The matrix used for the development of the methodology has as dimensions 4*10 (rows by columns). The value of frequency failure is fixed in Y axis. The value of consequence failure is fixed in X axis. This value is obtained as the result of the equation IS+E+QS+A+MC. The assessment of the severity of each criterion must be turned into the weights assignment for each level. In the graphical model, the number of items that are classified in a concrete cell of the matrix is indicated into the cell.
For example, for that equipment with a high value of criticality (high consequences and high failure frequency) a failure root cost analysis (FRCA) is proposed. This methodology probably won’t be able to decrease our maintenance costs or optimise our maintenance plan, but we will be able to limit unscheduled stops in critical systems. As a result, we will avoid problems with our clients or the availability of the facility. As the reader can deduce, this assessment is indirectly done in the criteria definition.
Criticality matrix used for the example let us to distribute the equipment among three areas: •
Non critical area (blank zone)
•
Semi-critical area (soft grey zone)
•
Critical area (dark grey zone)
For non-critical equipment, the methodology suggests you a Risk-Cost Optimization (RCO). We have also adapted this methodology in order to review all maintenance plans of noncritical equipment. In a first phase we have focused the efforts in lighten frequency of preventive maintenance. As a consequence, we hope to have an important decrease of our maintenance budget. But the most important point is that we hope to obtain a deeper knowledge of our failure mode equipment. Coming from an intensive preventive maintenance plan, most of the times we avoid the failure, which is probable the most comfortable point, but not the most efficient one. If we have an analysis that let us run to failure or at least reduce the preventive maintenance to these items that are non-critical for the company, we were able to manage the facility from a safe situation into an efficient one.
Table 6. Criticality Matrix FF 2 2
1,5
3
1
2
1,2
11
1
1
57
35
20
15
3
1
5
1
9
12
C
010
1020
2030
3040
4050
5060
6070
7080
8090
90100
11
2016 IFAC AMEST 12 October 19-21, 2016. Biarritz, France
Serra Parajes Javier et al. / IFAC-PapersOnLine 49-28 (2016) 007–012
4. CONCLUSIONS To limit the concept of value to cost terms is to limit the capability of the asset management. Depends on the nature and the specific sector of the company, many other factors must be taken in account. Criticality analysis allows allocating with a simple methodology your items assigning them a relative value in function of the strategy and target of the company. It is a very powerful tool and a solid starting point for an optimising policy of OPEX in the lifecycle.
5. REFERENCES Crespo Márquez, A., Moreu de León, P., Sola Rosique, A. and Gómez Fernández, J.F. (2016). Criticality Analysis for Maintenance Purposes: A Study for Complex Inservice Engineering Assets. Qual. Reliab. Eng. Int. 32, 519-533. Crespo Márquez, A. (2007). The Maintenance Management Framework: Models and Methods for Complex Systems Maintenance. Springer-verlag. London. Puente, J., Pino, R., Priore, P., De la Fuente, D. (2002). A decision support system for applying failure mode and effects analysis. Int. J. Qual. Reliab. Manag. 19(2), 137–150. Moss, T.R., Woodhouse, J. (1999). Criticality analysis revisited. Qual. Reliab. Eng. Int. 15, 117–121. EN 13306:2010. (2010). Maintenance terminology. European Standard. CEN (European Committee for Standardization). Brussels. Wireman, T. (1998). Developing Performance Indicators for Managing Maintenance. Industrial Press. New York.
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