Session 2002 CIGRÉ. A Proposal for using Value Engineering Technique in a Power Plant to Minimize Maintenance cost

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1 21, rue d'artois, F Paris Session 2002 CIGRÉ A Proposal for using Value Engineering Technique in a Power Plant to Minimize Maintenance cost A.Moazedi* Moshanir Power Engineering Consultants Co. N.Khosravi Niroo Research Institute (N.R.I.) (Tehran, Iran) Summary: Recently, V.E. 1 technique has been developed as an effective method in power system planning. Actually, this method is one of the usual ways for maximizing benefit-to-cost ratio of systems. In power plants, importance and complexity of maintenancebenefit/cost-analysis leads us to apply a systematic method such as VE- for maximizing the benefit-tocost in each section of power plant. In this paper, it is intended to emphasize that V.E. technique is a proper, applicable, and efficient way for decreasing maintenance cost and increasing performance of power plants. Key Words: Value Engineering Function diagram - CCPP 2 Maintenance 1. Introduction Montazer Ghaem is an integrated power plant in Iran that includes following units: MW steam turbine units which have been installed for about 27 years MW gas turbine units which have been installed for about 8 years MW steam turbine units, related to combined cycle section. Each of these 107 MW steam turbine units is connected into two gas turbine units through two separate HRSG 3. These units have been installed for 2 years. The authors have supervised the erection and commissioning of the 107 MW steam turbines as the consultant of the client, and believe that, the problems and mistakes, which occurred during design, erection and commissioning of the plant will probably increase the O&M 4 cost. On the other hand, the declaration of operators -who are also responsible for O&M of old units- shows, the volume of O&M activities for these new units are considerably high comparing to the older ones. It should also be considered that, the old units are almost at the end of their life cycle and logically should have a higher O&M cost. Further more, in new units, thanks to using DCS 5, the human mistakes should be basically reduced and consequently a lower O&M cost should be achieved, but unexpectedly this cost is high. In light of the above description no further investigations such as statistical studies are required to reveal the problem of high O&M cost for the case under study. Besides, these combined cycle units use indirect cooling system (natural draft) with jet condenser. There are few practical cases for this type of plants not only in Iran but also all around the world. Regarding the aforementioned subjects, and considering that, 11 similar units are in the development program of Iran utility, we believe, the technical-financial study of these units is a necessity to achieve the following objectives: To analyze some important technical-financial indices, such as, availability or life cycle cost which are the best indices for decision making in development policy of the generating units. The evaluation of these parameters will not only clarify the shortcomings of the system but also give a proper space for a brain-storm (applicable in speculation phase of VE, which will be explained later). 1 Value Engineering 2 Combined Cycle Power Plant 4 Operation and Maintenance 3 Heat Recovery Steam Generator 5 Distributed Control System * Dept Electrical Machines, Mosahnir Co., P.O. Box 19395, Tehran-Iran

2 To find, proper solutions for increasing the productivity of O&M team and improving the performance of the existing system hardware. In this paper we will concentrate on the second objective. Although, the main structure of study for the first and second objective is similar but there are some differences between them in details, conclusions, indices, and approaches. 2. Definitions And Approach First of all, a systematic definition for a power plant should be presented. A system such as a power plant could be defined as: An integration of components, which have been designed, manufactured and combined to each other to achieve an identified goal. All components of a system could be categorized in two main sections: Prime mission equipment: which are closely involved in implementation of main aim or mission of the system. Logistic support: including the testing equipment, maintenance tools, spare parts, O&M manuals and instructions, technical teams, and etc. The logistic support section has the following subsystems: Maintenance engineering: Gathering the technical data, definition of the management policy, designing the structure of logistic support system and the relationship among the subsystems are the main duties of the maintenance engineering. Technical execution teams: These teams execute the maintenance activities. Spare parts stock: Ordering, stocking and submitting the spare parts to other disciplines are the duties of this section, which will be done based on maintenance-engineering policy. As it could be seen, the maintenance engineering is the brain of system. The responsibility of the maintenance engineering in optimization procedure could be divided into two parts: Solving software problems: Including: Redefining the duties, roles and responsibilities of personnel and, also the reprogramming the predictive maintenance. Solving hardware problems: The maintenance engineering should find the equipments that the technical-financial analysis introduces them as shortcomings of the system. In the next step, these equipments should be replaced with the more effective ones. This study also includes the modernization process or modification in system design. We propose VE technique as a powerful tool, for optimization procedure in both of aforementioned parts. Here below, the basic concept of this method will be explained. 3. An Introduction To VE A complete VE study is consisting of following phases: Orientation phase, including following steps: - Team selection - Goals Definition Information phase, including following steps: - Gathering information - Drawing and evaluation of function diagram Speculation phase A function diagram with further details is applicable both in evaluation phase, and in speculation phase. In the speculation phase thanks to innovative space, created in the information phase, new alternatives for defective parts will be introduced. Evaluation phase Finally the suggested alternatives have to be evaluated and the best will be selected. Implementation and follow up phase VE team will have a supervisory control on implementation of the proposed modification. In a complete VE procedure, effects of this modification will be practically observed and analyzed. This analysis logically should demonstrate that, the cost saving of the proposed system, overcomes the modification cost and also the cost of VE study. [1, 2, 6] 4. Software Problems In order to improve the performance of the logistic support team, the software (policy) of the team should be properly defined. This software includes the programs and methods that define: Predictive maintenance procedure Emergency or unscheduled maintenance procedure Roles and duties of personnel and teams This optimized software will have following advantages: Minimized level of reworking losses. A high level of productivity of personnel A minimized level of quality defect and so on. All of the aforementioned advantages could be summarized as a low maintenance cost. As described before, the proposed optimization method is VE, which can be implemented as follows: 4.1 Team selection This is a key element to the success of any VE study. Two factors should be considered: The problem or opportunity determines the required talent-mix for its resolution. The selection of people (team participant) to represent that talent and proficiency should be compatible with the results expected. 4.2 Goals The team can set the following goals: To define the roles and responsibilities of personnel in the maintenance of equipment clearly.

3 To create an organization to support the recommended solutions. To develop an implementation plan for the recommend solutions. 4.3 Gathering information A series of questions are developed to gather information, supplementary to that obtained from the position descriptions. Some of the specific information, which must be requested, is: List all the tasks that you believe they are your responsibility to perform, for which you are held accountable. Give a percentage of time for each. List all the tasks you consider part of your responsibility to perform but are not included in your position. (Give a percentage of time for each) What tasks are you performing as part of your position responsibilities that you feel you should not be responsible or held accountable for? (Give a percentage of time for each) What tasks are not you currently performing that you would like to or feel should be part of your position responsibilities? Give a percentage of time for each. 4.4 Function diagram Now, it is time to draw the function diagram. Since drawing the function diagram of a maintenance management system is difficult, so it is suggested to draw an individual function diagram for each of the following questions. Then a combined function diagram will give a complete one. These questions are: How does a maintenance center perform maintenance of equipment? How do we prepare a business plan? How do we perform major overhauls and repairs? How do we modify equipment? How do we conduct root cause analysis? Figure (1): maintenance engineering function diagram The resultant function diagram will be tested for intuitive logic and function dependency, by asking how and then why. Diagram represents the necessary function, which are essential to maintenance of equipment. Figure (1) typically shows some parts of the final function diagram. Thanks to this diagram and also the information obtained in gathering information phase, it would be possible to revise and redefine the structure of maintenance engineering management. But, in the first step it is required to find out the defects. This will be done by SA 1 method. 4.5 Sensitivity analysis Function diagrams are typically produced without dimension. SA, is one of the techniques that, gives dimensions to the functions of function diagram considering value criteria (e.g. cost, time, responsibility, decisions, etc.) and indicates the sensitivity of functions to a selected value criteria. In order to evaluate the drawn functions diagram we propose to use an enhanced SA technique. This technique will be applied to both the critical and noncritical path function of diagram, to provide a more defined determination of responsibility. This enhancement requires a new method of producing the SA matrix. [1, 3] For producing this matrix, the first step is to define the A matrix, in which the aij element is the participation percentage of jth unit in ith function activity. We assume that the system logistic support is consisting of n units and m functions; therefore the A matrix is n m matrix. The units should be extracted 1 Sensitivity Analysis

4 from the organization chart of existing system. Also the required units, which the study reveals the necessity of them, should be added. The functions could be determined from the function diagram of existing system. The desirable functions, which the study demonstrates the necessity of them should also be included. Now, we define the B matrix, it is exactly the same as A matrix, but, bij element introduces the desirable relationship between each unit and its relevant responsibilities, where aij introduces the existing relationship between these two. Assume, C and D matrix, in them: aij c ij = and d ij = c ij 1 (1), (2) bij Now, assume E vector, which ei element is the weight of ith function comparing to total activities of logistic support. The E vector could be determined by MCDM 1 methods (i.e. will be described later). Then, the F matrix is defined with the following equation: f n = e d = { total deviation from } (3) expected duty for jth unit j i ij i= 1 fj is a normalized parameter, and is less than one. Logically the fj should be a small quantity and it is expected that it be approximately equal to zero. Therefore, if for some specific j the fj had a high amount (e.g. more than 0.1), it could be considered as a defect. In other words, a f > 0. 1 means, the deviation j of expected duty for the unit j is more than a desirable amount. The defective units should be revised and a new roles and responsibilities must be defined for them. New divisions and new management schemes, which will be achieved at this stage, are required to be evaluated. The method is to employ SA matrix as described above. Through the application of a try & error procedure an optimum scheme -with the least deviation from expected duty and also the least modification in the structure of the system- will be obtained. In order to complete the VE procedure, the achieved scheme should be implemented and followed up. 5. Hardware Problems As seen before, it is possible that, some hardware compartments do not have a suitable technical-financial specification. In order to optimize the performance, these compartments should be identified. In the next step some other alternatives, should be found, then a complete evaluation is necessary to allow a reasonable selection. Obviously, the compartment with the low performance will be replaced with the best choice. Implementation of this procedure is one of maintenance engineering duty. Complexity of this procedure, and wide variety of the items and parameters, in such plants, lead us to use a systematic evaluation method. Similar to previous section, our suggestion is to employ VE technique for this purpose. 5.1 Approach When the primary phases of VE made up, we are at the function-diagram-drawing stage. For a power plant we use an object-oriented hierarchy model. Hierarchy models are useful where a complex -with various compartments- is to be analyzed. A subject-oriented model is not suitable for this purpose, and usually is used for innovations in design, however for optimizing an existing plan the object-oriented one is preferred. Figure (2) shows a hierarchy model of the under study CCPP. The main question for drawing this figure is, How electrical energy would be generated. Evidently, the diagram shows the energy flow path, and each box only transform or transmit the energy. It should be noted that, this diagram have been drown based on a primary analysis, however, the VE team for a practical case should carry out a more accurate study.[4] As could be seen in figure (2), this diagram is very simple. Actually, for following reasons we are not interested to use a complex-diagram (which includes all details) at this stage: Drawing a complete function diagram is very difficult and unnecessary. The evaluation of a detailed diagram is very complex. When the function diagram completed, the value of each function must be calculated. The proposed approach is to employ following equation: importance value = (4) life cycle cost Importance of each function is a normalized quantity, which will be derived with MCDM method. This method will briefly described in the next section. Life cycle cost is a well-know index in tech-financial evaluation of the systems, however the parameters, which should be considered in LCC 2 computation, differ from one system to another. For this reason we will also give a brief description about the method of LCC calculation in this paper. [5, 6] 5.2 MCDM methods When it is intended to make a decision among some identified alternatives, and there are various quantitative and qualitative criteria -which should be considered in decision making- a standardized method is required, however, there is no standard for measurement of qualitative criteria. On the other hand, generally there is no reference for comparing the criteria -both quantitative and qualitative criteria-to each other. 1 Multi Criteria Decision Making 2 Life Cycle Cost

5 Figure (2): A hierarchy model of the under study CCPP Regarding aforementioned problems, multi criteria decision making, is a difficult procedure. Actually, these problems lead us to an uncertain and inaccurate decision, which should be generally made by an individual person and according to its own interests. Some practical methods have been developed to overcome these problems. These are generally known as MCDM methods. 5.3 Extracting the importance of functions One of the most applicable MCDM methods is the SAW 1. By means of this method a number of questionnaires could be designed in order to find out the importance of each function. These questionnaires will give some indices and criteria to asked persons. Obviously, these persons must have enough skill and experience in O&M of the power plants. The analysis of questionnaires will be summarized to an importance table of functions. In the next steps a normalized importance volume is required, therefore the importance table has to be normalized. 5.4 Life cycle cost The LCC of each function can be calculated from following formula: LCC=LCA+LCS+LCU+LCD (5) In which: LCA: Acquisition Cost LCS: Life Support Cost LCU: Life Unavailability Cost = λ jtop / 8760[ CF j + CL j Td j + CR j MTTR j ] (6) j MTTR j : Mean Time To Repair for mode j failure [h] Top: Operating hours per year Td j : Average down time due to mode j failure [h] CL j : Loss and compensation expenses per hour of down time do to j failure λ j : Average failure rate for a mode j failure [1/a] CR j : Repair labor cost per hour for a mode j failure 1 Simple Added Weighting CF j : Duration dependent costs arising from each mode j failure LCD: Disposal cost It should be noted, each function consists of numbers of specific equipment; Therefore aforementioned parameters for an individual function could be calculated as the sum of the same parameters of its relevant equipment Some of the parameters used in this formula, can be obtained by means of statistic study, and some of them might be achieved from the manufacturer/utility technical-financial data. [7] It is clear that, LCC calculation is a difficult procedure and needs a lot of data. The main question is, if such a wide range of activities is economic or not. Implemented research reveal that for each dollar paid for VE analysis, $ have been saved. On the other hand, as mentioned before, LCC study -which is the most difficult part in our study- is not only necessary for this purpose but also for the policy of utility development in Iran. 5.5 Value calculation When the importance and LCC calculations made up, dividing the importance of each function to its LCC will give the value of the function. If the differences among the values were not considerable all the subsystems are defective, however, this event hardly occurs. 5.6 Next steps Anyhow the defective subsystems ought to be revised. For this purpose the function diagram of each subsystem will be sketched, and a complete VE study will be implemented for it. The method of function diagram drawing and also, the evaluation method depends on the subsystems and the type and number of relevant functions, however, for a power plant, aforementioned evaluation method could be employed for many of subsystems. As an example it is assumed the MV supply system is introduced as a shortcoming through the primary evaluation. Figure (3) is a typical function diagram for

6 Figure (3): A typical function diagram for MV supply system this system. The evaluation method used in primary phase can be easily employed for this phase too. However, the LCC calculation formula may be simplified. Some of the parameters can be ignored and some of them could be estimated with a sort of statistic or comparative methods. The similar transformers or switchgear, which have been installed in other plants, would be a good reference in this manner. [8] Also, the manufacturer experiences may be useful for such a simplification. Shortcomings of the system will be recognized at the end of this stage, as described before. In order to complete VE procedure, speculation, evaluation, and implementation phases should also be accomplished subsequently based on the information obtained in previous phases. [6] 6. Conclusion In this paper a systematic method which is generally applicable for optimization of industrial, civil, and other projects is proposed for minimizing O&M cost of a specified power plant. Meanwhile the benefits of this method and the practical proposal for its implementation have been described. Considering the successes of this method in other applications, and regarding the explanations given in this paper, we believe that a VE study will introduce some effective and practical suggestions, which can considerably reduced the O&M cost in the involved power plant. Obviously the saved cost should compensate not only the VE study cost, but also the cost of required modifications (if any). [9] Acknowledgement: The authors wish to thank J. Saiy, M. Fetanat, M. Ipackchi, N. Hashemi, H. Morshed beig M. Jalali and Z. Kamali for their kindly cooporation in prepairing this paper. References: [1] Barrie.D.S, Paolson.B: Professional construction management. MC Graw Hill, Newyork, [2] Bryant.N, Revere.P: Function definition and analysis. SAVE international [3] Golver.N: Value management applied to organizational effectiveness. [SAVE conference proceeding, 1992] [4] Bryant.W: Function logic hierarchy. SAVE international, [5] Kudo.T: Value analysis in system equipment maintenance. [SAVE conference proceeding, 1993] [6] Miles.L.D: Techniques of value analysis and engineering. MC Graw Hill, Newyork, 1961, P.I [7] D. Braun, A. Gureig: Life Management for Generator Circuit Breakers. [CIGRE. August/ eptember ] [8] Morin.C, Carer.P, Croguennoc.A, Biasse.J.M, Blanc.J.Y, Verrier.P: Optimization of the design of future HV/MV EDF substations using dependability studies and value analysis, the example of a medium voltage switchboard. [CIRED, 12 th International conference on electricity distribution, vol. 1, 1993] [9] Kenneth Elder: Implementing value engineering on a major project of the US department of energy [SAVE proceedings,1997].