GasTurbine Engineering HandbookSecond Edition phần 10 docx

G:/GTE/FINAL (26-10-01)/CHAPTER 21.3D ± 723 ± [722±777/56] 1.11.2001 4:00PM Combining the practice of preventive maintenance and total quality con- trol and total employee involvement results in an innovative system for equipment maintenance that optimizes effectiveness, eliminates breakdowns, and promotes autonomous operator maintenance through day-to-day activ- ities. This concept known as Total Productive Maintenance (TPM) was conceived by Seiichi Nakajima and is well-documented in his book ``Intro- duction of TPM'' and is highly recommended reading for all involved in the maintenance area. A new maintenance system is introduced based on the new mantra for the selection of all equipment ``Life Cycle Cost.'' This new system especially for major power plants is based on the combination of total condition monitor- ing, and the maintenance principles of total productive maintenance, and is called the ``Performance Based Total Productive Maintenance System.'' The general maintenance system is fragmented and can be classified into many maintenance concepts. The following are five P's of maintenance for major power plants, petro-chemical corporations, and other process type industries leading to the ultimate maintenance system: 1. Panic maintenance based on breakdowns 2. Preventive maintenance 3. Performance based maintenance 4. Performance productive maintenance 5. Performance based total productive maintenance (PTPM). Performance based total productive maintenance consists of the following elements: 1. Performance based total productive maintenance aims to maximize equipment efficiency and time between overhaul. (overall perform- ance effectiveness) 2. Performance based total productive maintenance aims to maximize equipment effectiveness. (overall effectiveness) 3. Performance based total productive maintenance establishes a thor- ough system of PM for the equipment's entire life span. 4. Performance based total productive maintenance is implemented by various departments (engineering, operations, maintenance). 5. Performance based total productive maintenance involves every single employee, from top management to workers on the floor. 6. Performance based total productive maintenance is based on the promotions of PM through motivation management: autonomous small group activities. Maintenance Techniques 723 G:/GTE/FINAL (26-10-01)/CHAPTER 21.3D ± 724 ± [722±777/56] 1.11.2001 4:00PM The word ``total'' in ``performance based total productive maintenance'' has four meanings that describe the principal features of PTPM: 1. Total overall performance effectiveness indicates PTPM's pursuit of maximum plant efficiency and minimum downtime. 2. Total overall performance effectiveness indicates PTPM's pursuit of economic efficiency or profitability. 3. Total maintenance system includes maintenance prevention (MP) and maintainability improvement (MI) as well as preventive main- tenance. 4. Total participation of all employees includes autonomous maintenance by operators through small group activities. Table 21-1 shows the relationship between PTPM, productive mainten- ance, and preventive maintenance. Performance based total productive maintenance eliminates the following seven major losses: Down time: 1. Loss of time due to unnecessary overhauls based only on time inter- vals. 2. Equipment failure-from breakdowns. 3. Loss of time due to spare part unsuitability or insufficient spares. Table 21-1 Benefits of Various Maintenance Systems Maintenance Performance Based Total Productive Maintenance Performance Productive Maintenance Performance Based Maintenance Preventive Maintenance Panic Maintenance Economic efficiency Yes Yes Yes Yes No Economic and time efficiency Yes Yes Yes No No Total system efficiency Yes Yes No No No Autonomous maintenance by operators Yes No No No No 724 Gas Turbine Engineering Handbook G:/GTE/FINAL (26-10-01)/CHAPTER 21.3D ± 725 ± [722±777/56] 1.11.2001 4:00PM 4. Idling and minor stoppagesÐdue to the abnormal operation of sen- sors or other protective devices. 5. Reduced outputÐdue to discrepancies between designed and actual operating conditions. Defect: 1. Process defectsÐdue to improper process conditions that do not meet machinery design requirements. 2. Reduced yieldÐfrom machine startup to stable production due to the inability of the machine to operate at proper design conditions. Maximization of Equipment Efficiency and Effectiveness High machine efficiency and availability can be attained by maintaining the health of the equipment. Total performance condition monitoring can play a major part here as it provides early warnings of potential failures and performance deterioration. Figure 21-1 shows the concept of a total performance condition monitoring system. Pure preventive maintenance alone cannot eliminate breakdowns. Break- downs occur due to many factors such as, design and or manufacturing errors, operational errors, and wearing out of various components. Thus, changing out components at fixed intervals does not solve the problems and in some cases adds to the problem. A study at a major nuclear power station indicated that nearly 35% of the failures occurred within a month of a major turnaround. Figure 21-2 shows the life characteristics of a major piece of turbomachinery. What-If Analysis D-CS System Gas and Steam Turbine Control System Aerothermal Data D-CS System Gas and Steam Turbine Control System Dynamic Vibration Data Mechanical Data Analyze Data Diagnose Data Report Results Figure 21-1. Total performance-based condition monitoring system. Maintenance Techniques 725 G:/GTE/FINAL (26-10-01)/CHAPTER 21.3D ± 726 ± [722±777/56] 1.11.2001 4:00PM The goal of any good maintenance program is ``Zero Breakdown.'' To achieve this goal, there are five counter measures. These are listed below: 1. Maintaining well-regulated basic conditions (cleaning, lubricating, and bolting). 2. Adhering to proper operating procedures. 3. Total condition monitoring (performance, mechanical, and diagnostic based). 4. Improving weaknesses in design. 5. Improving operation and maintenance skills. The interrelationship between these five items is shown in Figure 21-3. The division of labor between operations and maintenance is shown in Figure 21-4. It is the primary responsibility of the production department to establish and regulate basic operating conditions, and it is the primary responsibility of the maintenance department to improve defects in design. The other tasks are shared between the two departments. Preventive and Maintainability Improvement Proper Operation Trial runs at acceptance and startup controls Counter Measures Maintenance Prevention Wear OutOperational Errors Design Manufacturing Errors Cause Wear Out Failure Chance Failure Start up Failure Category Useful Life Chance Failure Period Failure Rate Start Up Failure Period Wear Out Period Operational Hours Reduction of Failure Through Maintenance Figure 21-2. Machinery life cycle characteristics. 726 Gas Turbine Engineering Handbook G:/GTE/FINAL (26-10-01)/CHAPTER 21.3D ± 727 ± [722±777/56] 1.11.2001 4:00PM The successful implementation of total productive maintenance requires: 1. Elimination of the six big losses to improve equipment effectiveness 2. An autonomous maintenance program with total condition monitoring 3. A scheduled maintenance program for the maintenance department 4. Increased skills of operations and maintenance personnel 5. An initial equipment management program Maintain Basic Conditions Adhere to Operating Procedures Discover and Predict Deterioration Establish Repair Methods Restore Deterioration Correct Defects in Design Prevent Operation Errors Prevent Repair Errors Prevent Human Errors The Five Types of Breakdown Countermeasures Improve Operation Skills Improve Maintenance Skills Figure 21-3. Breakdown countermeasures. Establish and regulate basic conditions Adhere to operating procedures Total Condition Monitoring Improve defects in design Improve skills Uncover Hidden Defects Product Department Maintenance Department Figure 21-4. Responsibilities of the operations and maintenance departments. Maintenance Techniques 727 G:/GTE/FINAL (26-10-01)/CHAPTER 21.3D ± 728 ± [722±777/56] 1.11.2001 4:00PM Organization Structures for a Performance Based Total Productive Maintenance Program Typically successful implementation of PTPM in a large plant takes three years. Implementation calls for: 1. Changing peoples attitudes 2. Increasing motivation 3. Increasing competency 4. Improving the work environment The four major categories in developing a Performance Based Total Productive Maintenance program are: 1. Preparation for the PTPM program 2. Preliminary implementation 3. PTPM implementation 4. Stabilization of the program Implementation of a Performance Based Total Productive Maintenance There are several steps involved in implementation of a PTPM pro- gram. 1. Announcement of decision to implement PTPM. A formal presentation must be made by top management introducing the concepts, goals, and benefits of PTPM. Management commitment must be made clear to all levels of the organization. 2. Educational campaign. The training and promotion of PTPM philo- sophy is a must. This is useful to reduce the resistance to change. The education should cover how PTPM will be beneficial to both the corporation and the individuals. 3. Creation of organization to promote PTPM. The PTPM promotio- nal structure is based on an organizational matrix. Obviously, the optimal organizational structure would change from organization to organization. In large corporations, PTPM promotional headquarters must be formed and staffed. Thus, any questions can be addressed here on a corporate level. 4. Establishment of basic PTPM goals. Establishing mottos and slogans can do this. All goals must be quantifiable and precise specifying: 728 Gas Turbine Engineering Handbook G:/GTE/FINAL (26-10-01)/CHAPTER 21.3D ± 729 ± [722±777/56] 1.11.2001 4:00PM a. Target (what) b. Quantity (how much) c. Time Frame (when) 5. Master plan development for PTPM. A master plan must be created. Total condition monitoring equipment should be designed, and equipment should be purchased. 6. Initiation of PTPM. This represents a ``kickoff '' stage. At this point, the whole staff must start to get involved. 7. Improvement of equipment effectiveness. This should start with a detailed design review of the plant machinery. A performance analysis of the plant could point to a specific area known to have problems (i.e., section of plant) must be selected and focused on, project teams should be formed and assigned to each train. An analysis should be conducted that address the following: a. Define the problem. Examine the problem (loss) carefully; com- pare its symptoms, conditions, affected parts, and equipment with those of similar cases. b. Do a physical analysis of the problem. A physical analysis clarifies ambiguous details and consequences. All losses can be explained by simple physical laws. For example, if scratches are frequently produced in a process, friction or contact between two objects should be suspected. (Of the two objects, scratches will appear in the object with the weaker resistance.) Thus, by examining the points of contact, specific problem areas and contributing factors are revealed. c. Isolate every condition that might cause the problem. A physical analysis of breakdown phenomena reveals the principles that control their occurrence and uncovers the conditions that produce them. Explore all possible causes. d. Evaluate equipment, material, and methods. Consider each condi- tion identified in relation to the equipment, jigs and tools, mater- ial, and operating methods involved, and draw up a list of factors that influence the conditions. e. Plan the investigation. Carefully plan the scope and direction of investigation for each factor. Decide what to measure and how to measure it and select the datum plane. f. Investigate malfunctions. All items planned in step 5 must be thoroughly investigated. Keep in mind optimal conditions to be achieved and the influence of slight defects. Avoid the traditional factor analysis approach; do not ignore malfunctions that might otherwise be considered harmless. Maintenance Techniques 729 G:/GTE/FINAL (26-10-01)/CHAPTER 21.3D ± 730 ± [722±777/56] 1.11.2001 4:00PM g. Formulate improvement plans. Define consultants who could do re-design the given piece of equipment. Discuss with manufac- turers your plans. 8. Establishment of autonomous maintenance program for operators. This is focused against the classic ``Operations'' versus ``Mainte- nance'' battle. Operators here must be convinced that they should maintain their own equipment. For example, an attitude has to be developed for operators to understand and act on the reports pro- duced by the on-line performance condition monitoring systems. 9. Setup of scheduled maintenance program. Scheduled maintenance conducted by the maintenance department must be smoothly coor- dinated with autonomous maintenance done by the plant operators. This can be done by frequent meetings and plant audits. In most plants an undeclared conflict exists between the operations and maintenance groups. This arises from the false perception that these two groups having conflicting goals. The PTPM philosophy will go a long way in bringing these groups together. 10. Training for improvement of operation and maintenance skills. This is a key part of PTPM. Ongoing training in advanced maintenance techniques, tools, and methods must be done. This could cover areas such as: a. Bearings and seals b. Alignment c. Balancing d. Vibration e. Troubleshooting f. Failure analysis g. Welding procedures h. Inspection procedures i. NDT 11. Equipment management program. Startup problems, solutions, and design changes should be clearly documented and available for a good equipment management plan. All items that can reduce Life Cycle Costs (LCC) should be considered. These include: a. Economic evaluation at the equipment-investment stage b. Consideration of MP or maintenance-free design and economic LCC c. Effective use of accumulated MP data d. Commissioning control activities e. Thorough efforts to maximize reliability and maintainability 730 Gas Turbine Engineering Handbook G:/GTE/FINAL (26-10-01)/CHAPTER 21.3D ± 731 ± [722±777/56] 1.11.2001 4:00PM 12. Final implementation of PTPM. This stage involves the refinement of PTPM and the formulation of new goals that meet specific corporate needs. Maintenance Department Requirements To ensure the success of the PTPM program, the maintenance department must be well equipped and trained. The following six basic categories are prerequisite to the proper functioning of the Maintenance Department under the PTPM: 1. Training of personnel 2. Tools and equipment 3. Condition and life assessment 4. Spare parts inventory 5. Redesign for higher machinery reliability 6. Maintenance scheduling 7. Maintenance communication 8. Inspections Training of Personnel Training must be the central theme. The days of the mechanic armed with a ball-peen hammer, screwdriver, and a crescent wrench are gone. More and more complicated maintenance tools must be placed in the hands of the mechanic, and he must be trained to utilize them. People must be trained, motivated and directed so that they gain experience and develop, not into mechanics, but into highly capable techni- cians. While good training is expensive, it yields great returns. Machinery has grown more complex, requiring more knowledge in many areas. The old, traditional craft lines must yield before complicated equipment maintenance needs. A joint effort by craftsmen is necessary to accomplish this. I. Type of Personnel a. Maintenance Engineer. In most plants, the maintenance engineer is a mechanical engineer with training in the turbomachinery area. His needs are to convert what he has learned in the classroom into actual hands-on solutions. He must be well versed in a number of areas such as performance analysis, rotor dynamics, metallurgy, lubrication systems, and general shop practices. His training must be well planned so that he can pick up Maintenance Techniques 731 G:/GTE/FINAL (26-10-01)/CHAPTER 21.3D ± 732 ± [722±777/56] 1.11.2001 4:00PM these various areas in steps. His training must be a combination of a hands- on approach coupled with the proper theoretical background. He should be well versed in the various ASME power test codes. Table 21-2 is a listing of some of the applicable codes for gas turbine power plants. Attendance at various symposiums where users of machinery get together to discuss problems should be encouraged. It is not uncommon to find a solution to a problem at these types of round table discussions. b. Foremen and Lead Machinist. These men are the key to a good maintenance program. They should be sent frequently to training schools to enhance their knowledge. Some plants have one foreman who is an ``in-house serviceman;'' he supervises no personnel, but acts as an in-house consultant on maintenance jobs. c. Machinist/Millwright. The machinist should be encouraged to oper- ate most of the machinery in the plant maintenance shop. By rotating him among various jobs, his learning and development is accelerated. He should then become as familiar with a large compressor as a small pump. Encour- agement should be given to the machinist to learn balancing operations and to participate in the solution of problems. Spreading around the hardest jobs develops more competent people and is the basis of any PTPM program. Restricting a man to one type of work will probably make him an expert in that area, but his curiosity and initiative, prime motivators, will eventually fade. II. Types of Training a. Update Training. This training is mandatory for all maintenance personnel, so that they may keep abreast of this high technology industry. Table 21-2 Performance Test Codes 1. ASME, Performance Test Code on Overall Plant Performance, ASME PTC 46 1996, American Society of Mechanical Engineers, 1996 2. ASME, Performance Test Code on Test Uncertainty: Instruments and Apparatus PTC 19.1, 1988 3. ASME, Performance Test Code on Gas Turbines, ASME PTC 22 1997, American Society of Mechanical Engineers, 1997 4. ASME, Performance Test Code on Gas Turbine Heat Recovery Steam Generators, ASME PTC 4.4 1981, American Society of Mechanical Engineers, Reaffirmed 1992 5. ASME Gas Turbine Fuels B 133.7M Published: 1985 (Reaffirmed year: 1992) 6. ISO, Natural GasÐCalculation of Calorific Value, Density and Relative Density International Organization for Standardization ISO 6976-1983(E) 732 Gas Turbine Engineering Handbook [...]... ratio and higher firing temperature, has led to the building of large gas turbines producing G:/GTE/FINAL (26 -10- 01)/CHAPTER 21.3D ± 738 ± [722±777/56] 1.11.2001 4:00PM 738 Gas Turbine Engineering Handbook 100 96 85 90 80 70 60 45 50 40 35 Availability Efficiency 30 20 10 0 Below 100 MW Above 100 MW Figure 21-5 Comparison of availability and efficiency for large frame type gas turbines nearly 300 MW... Industry Services, 4th Edition, August 1998 API Std 617, Centrifugal Compressors for Petroleum, Chemical and Gas Industry Services, 6th Edition, February 1995 API Std 618, Reciprocating Compressors for Petroleum, Chemical and Gas Industry Services, 4th Edition, June 1995 API Std 619, Rotary-Type Positive Displacement Compressors for Petroleum, Chemical, and Gas Industry Services, 3rd Edition, June 1997... 1994) ANSI/API Std 610 Centrifugal Pumps for Petroleum, Heavy Duty Chemical and Gas Industry Services, 8th Edition, August 1995 (-1995) API Std 613 Special Purpose Gear Units for Petroleum, Chemical and Gas Industry Services, 4th Edition, June 1995 API Std 614, Lubrication, Shaft-Sealing, and Control-Oil Systems and Auxiliaries for Petroleum, Chemical and Gas Industry Services, 4th Edition, April 1999... efficiencies in the mid forties The availability factor for units with mature technology, below 100 MW, are  between 94±97%, while the bigger units above 100 MW have availability  factors of 85±89% The bigger units produce twice the output, but the avail ability factor has decreased from 95% to 85% A decrease of 7 10 points for all manufacturers Part of this decrease may be related to larger machinery... from cylindrical and/or 30 27 25 21 20 17 15 15 10 7 5 4 5 2 2 0 Compressor Combustor First Stage First Stage Blades Cans Nozzles Blades Controls Bearings Seals Couplings Generator Figure 21-6 Contributions of various major components to gas turbine down time G:/GTE/FINAL (26 -10- 01)/CHAPTER 21.3D ± 740 ± [722±777/56] 1.11.2001 4:00PM 740 Gas Turbine Engineering Handbook pressure dam babbitted sleeve... 21-2 They should be encouraged to work closely at the various maintenance schedules and turnarounds so that they are familiar with the machinery G:/GTE/FINAL (26 -10- 01)/CHAPTER 21.3D ± 734 ± [722±777/56] 1.11.2001 4:00PM 734 Gas Turbine Engineering Handbook Table 21-3 Mechanical Specifications ASME Basic Gas Turbines B 133.2 Published: 1977 (Reaffirmed year: 1997) ASME Gas Turbine Control and Protection... and Gas Industry Services, 3rd Edition, June 1997 ANSI/API Std 670 Vibration, Axial-Position, and Bearing-Temperature Monitoring Systems, 3rd Edition, November 1993 API Std 671, Special Purpose Couplings for Petroleum Chemical and Gas Industry Services, 3rd Edition, October 1998 They should be sent to special training sessions where hands-on experience can be gained After the completion of basic machinist... higher pressure ratio has lead to an increase in overall  gas turbine efficiency The increase in efficiency of 7 10% has in many cases lead to an availability decrease of the same amount or even more as seen in Figure 21-5 A 1% reduction in plant availability could cost $500,000/yr in income on a 100 MW plant, thus in many cases offsetting gains in efficiency Reliability of a plant depends on many parameters,... lathes, mills, drill presses, slotters, bores, grinders, and a good balancing machine A balancing machine can pay for itself in a very short time in G:/GTE/FINAL (26 -10- 01)/CHAPTER 21.3D ± 736 ± [722±777/56] 1.11.2001 4:00PM 736 Gas Turbine Engineering Handbook providing a fast turnaround and accurate dynamic balance Techniques to check the balance of gear-type couplings for the large high-speed compressors... increas ing the load carrying capacity In some instances, a 50 100 % load carrying capacity improvement can be achieved Some equipment manufacturers are offering bearing-upgrading kits for their machine in service Design of turbine blades to obtain higher efficiency and damping has been  done In some cases, this has improved efficiency by 8 10% , and stopped failures in these blades Steam injection has . costs. 96 35 85 45 0 10 20 30 40 50 60 70 80 90 100 Below 100 MW Above 100 MW Availability Efficiency Figure 21-5. Comparison of availability and efficiency for large frame type gas turbines. 738 Gas Turbine Engineering. Monitoring Systems, 3rd Edition, November 1993 API Std 671, Special Purpose Couplings for Petroleum Chemical and Gas Industry Services, 3rd Edition, October 1998 734 Gas Turbine Engineering Handbook G:/GTE/FINAL. this. All goals must be quantifiable and precise specifying: 728 Gas Turbine Engineering Handbook G:/GTE/FINAL (26 -10- 01)/CHAPTER 21.3D ± 729 ± [722±777/56] 1.11.2001 4:00PM a. Target (what) b.