162920171-Maintenance[1].ppt

C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power PlantUnderstanding Maintenance Strategies Reactive Maintenance

The oldest maintenance approach is reactive, or "run to-failure." Equipment isn't repaired or replaced until it breaks.Companies that rely solely on reactive maintenance find they have:Costly downtime. Equipment fails with little or no warning, so the process could be down until replacement parts arrive, resulting in lost revenue.

C&I Department, Bakreswar Thermal Power Station

C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power PlantHigher maintenance costs. Unexpected failures can increase overtime labor costs, as well as expedited delivery of replacement parts.Safety hazards. Failure with no warning could create a safety issue with the failing equipment or other units that might be affected.Reactive maintenance can be appropriate in some circumstances, such as for non-critical and low cost equipment with little or no risk of collateral damage or lost production. It makes little sense to change a light bulb before it burns out. It's important, however, to make sure that a failure won't create a chain reaction to more critical equipment.


C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power PlantAdverse consequences of run to failure include: Compromised safety or environmental complianceCollateral damage where failure increases the cost of repairLoss of product qualityLoss of process availabilityReduced throughputIncreased waste and rework cost


C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power PlantIf equipment failure makes any of these consequences likely, run to failure is not recommended. In a typical plant 50% of maintenance is reactive. In an ideal plant 10-25% of maintenance would still be reactive or run to failure. C&I Equipment Covered in Reactive MaintenanceBurner Tilting Pneumatic Drives.All Control Valve Pneumatic Drives.DCS Modules.


C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power PlantPreventive Maintenance The preventive maintenance philosophy is also known as time-based or planned maintenance. The goal of this approach is to maintain equipment in a healthy condition. Selected service and part replacements are scheduled based on a time interval for each device whether it needs it or not. For example, transmitter calibrations may be performed every six months in critical areas. While this approach may uncover possible problems, most of the checks are unnecessary because they're performed on healthy instrumentation.


C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power PlantPreventive Maintenance (PM) is typically used on equipment that has a high cost of failure. For this purpose, "failure" means more than when equipment ceases to functionit also covers situations where the equipment is unable to perform its intended function at needed quality, cost, and throughput.

To avoid high cost of failure, preventive maintenance often includes periodic lubrication, adjustment, replacement of parts, and cleaning. It is often based on the assumption that wear is a slow and continuous process that accelerates over time. Preventive maintenance is intended to stop the acceleration of wear, and return it to a low level.


C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power PlantUnfortunately, most wear is episodic in nature. That is, there is little or no wear until some outside stress ranging from lubricant contamination to exceeding equipment constraints triggers the rapid onset of wear. Maintenance in the absence of an outside stress is frequently not required. Failure to maintain equipment immediately after a stress can result in dramatic wear and rapid shortening of equipment life. The net result is that much preventive maintenance is either not required, or too late to be effective.


C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power PlantThe curves below show how preventive maintenance applies to the equipment-failure cycle.


C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power PlantThe cycle starts with a high probability of premature (infant) failures that result from manufacturing or installation errors. The probability of failures is then relatively level until the equipment begins to wear out. Preventive maintenance is scheduled to take place before this probability increases significantly.In reality, the maintenance schedule is rarely optimal. Time-based preventive maintenance is typically carried out too soon, which increases costs and decreases reliability (because the failure cycle again begins with a higher rate because of maintenance errors). Or the preventive maintenance comes too late, increasing the risk of wear-out failures.


C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power PlantTo time the maintenance correctly, you need to know the actual equipment condition and be able to predict the failure point. Disadvantages of depending solely on the preventive approach include:Wasteful. Equipment or components may be replaced prematurely, while they still have plenty of useful life left.Inventory costs. A larger inventory is typically needed to support a preventive maintenance program.Application-dependent wear often ignored. In light wear applications, equipment may receive excessive and unneeded maintenance.


C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power PlantIn severe wear applications, equipment may receive insufficient maintenance. In addition, identical equipment in different applications may require different maintenance intervals. No complete prevention of failures. A misalignment could be causing bearing wear, creating a possible failure before the next scheduled maintenance.

While preventive practices can be an important part of maintenance strategy, there's a growing need to include predictive and proactive maintenance as well


C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power PlantC&I Equipment Covered in Preventive MaintenanceFlame ScannersAll Damper Pneumatic Drives for Pulveriser System.Analysers for Flue Gas & SWASCoal Feeder Weighing System


C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power PlantAdverse consequences of preventive maintenance include:Over-maintenance, where unnecessary or ineffective maintenance is performedgenerally the cost of unnecessary maintenance and failures induced by incorrectly performed maintenanceUnder-maintenance, where failure conditions exist and are not correctedleading to the consequences described earlier for reactive or run to fail strategies


C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power PlantPredictive MaintenancePredictive maintenance improves on preventive maintenance by using actual equipment performance to determine when maintenance should occur.In predictive maintenance, equipment condition rather than time intervals determines the need for service. Online condition monitoring helps identify when wear-out risk begins to increase and predict when failure is likely to occur. This approach can save time and money because it enables to correct the problem before the equipment actually fails


C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power Plant Avoid the downtime and repair costs caused by unexpected failure as well as the costs and lost production caused by unnecessary preventive maintenance. Advanced predictive maintenance programs frequently modify the definition of a failure. Traditionally, a failure is defined as the point where the equipment breaks down and is no longer available for production. A more appropriate definition is that the equipment is no longer able to produce the right quality at the right production rate and the right cost. At this point, the plant is losing profitability and maintenance should be considered.


C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power PlantWith this strategy, periodic or continuous monitoring detects the onset of wear or degradation, and the information is then used to predict potential problems and the best time for maintenance. Predictive maintenance is typically used where failure cost is high Monitoring for predictive maintenance is available for rotating equipment, electrical equipment, process equipment, transmitters and valves, and other equipment types.


C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power PlantProactive maintenance While predictive maintenance uses online condition monitoring to help predict when a failure will occur, it doesn't always identify the root cause of the failure. That's where proactive maintenance comes in. Proactive maintenance relies on information provided by predictive methods to identify problems and isolate the source of the failure.Take the case of a pump that has periodic bearing failures. A condition-monitoring program may apply vibration sensors to the bearings, monitor the bearing temperature, and perform periodic analysis of the lube oil. These steps will tell when but not why the bearings are failing.


C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power PlantProactive maintenance might add equipment balancing during installation to reduce bearing stress, lowering failure rates and extending bearing life. But it will also take the next step to find the sources of failures for example, looking at cleaning procedures before tear-down to see if contamination during rebuild is a root cause for early bearing failures. By determining these root causes and acting to eliminate them, can not only prolong the life of the equipment. It also eliminates many seemingly random failures and avoid repairing the same equipment for the same problem again and again.


C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power PlantReducing Cost by Changing Work Practices Work practice changes are critical to reduce maintenance and operations cost. Often, however, the prospect of changing work practices convinces us that change is too difficult to be worthwhile.

The key to success in changing work practices is, therefore, to start with small, easy to accomplish changes that have big benefit. Some examples that illustrate the point are


C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power PlantChanging instrument maintenance practices such as calibration One of the easiest ways to reduce maintenance cost is to calibrate devices less frequently.

Look at the maintenance records. Devices that show very little drift between calibrations are candidates for longer intervals between device calibrations. This simple change can save money on most of the transmitters in the plant. Nothing needs to be purchased; just do what do less often.


C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power Plant

Calibration cost can be further reduced by using intelligent calibrators and PC-based calibration management software to reduce the time and effort required.


C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power PlantWith such tools, calibration schemes can be automatically entered into the calibrator from the PC software package. Calibration routes can be maintained in the PC as well.

Calibration of a device consists of attaching the calibrator, attaching the process variable source (for example, a pressure pump), and applying the process variable as the test scheme progresses. At the end of the calibration exercise, the smart calibrator will capture "as-found" and "as-left" information. In this way calibration is done faster, and with fewer errors.

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C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power PlantData lookup and data entry can consume up to half of an instrument technician's work time. Automating the input of calibration routes and schemes, and automating the upload of device calibration information to the calibration manager, can eliminate most of the data look-up and entry timeCalibration management software can automate calibration routes and calibration schemes. It can also automate the transfer of calibration data to the instrument record system. This combination of functions can save time, reduce cost, and improve calibration and record accuracy.


C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power PlantUpdating Maintenance Practices Changes in work practices are critical to reducing maintenance cost. Maintenance practices were typically developed long ago when most plant equipment was "dumb"that is, unable to provide or communicate information other than the basic measured variable or control signal. This limitation led to preventive maintenance, since actual equipment performance or condition was poorly known. Most of the maintenance procedures, data entry, record keeping, and work order management was manual.


C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power PlantMost of the equipment was over-maintained to reduce unscheduled downtime. Maintenance intervals were determined by the failure frequency of the highest failure unitsThese practices have tended to remain even after advances have made them unnecessary, locking in excess maintenance activity and cost. To reduce cost, budgets and staff are cut, but without changes in work processes. The result is a growing backlog of activities and an increase in urgent work. These practices need to be updated to reflect new technology and capabilities.


C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power PlantResponsibilities :The Manager is having overall responsibility for the establishment, implementation, and performance of the maintenance program as described below:maintaining equipment in accordance with applicable manufacturer's recommendations and the requirements of this guideline;specifying maintenance methods, procedures, and controls to ensure the quality of materials, parts, and workmanship


C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power Plantensuring maintenance personnel are appropriately qualified;ensuring an adequate supply of suitable spare parts, materials, and supplies to service equipment covered by the maintenance program;maintaining maintenance history files, analyzing causes of off-normal equipment, and performing failure analyses;coordinating maintenance with the owner/operator to establish proper plant conditions


C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power Plantmonitoring the overall effectiveness of the maintenance program and incorporating program changes based on plant history, performance, and industry experience;approving revisions to the program.


C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power PlantThe Assistant Manager is having direct responsibility for execution of maintenance activities as follows:Obtaining work permits to conduct maintenance activities ensuring maintenance results are recorded in maintenance history;reviewing, trending, and analyzing data to detect any degradation of equipment condition;coordinating with Operation and technical support, as required, to perform additional testing to confirm suspected deficient conditions;



providing recommendations to the Manager to upgrade maintenance programsproviding periodic summary reports to maintenance management describing the current status of the maintenance program and summarizing problems recently identified or corrected; ensuring that baseline data is updated after any maintenance or modifications.


C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power PlantInfrastructure & LogisticsTools & Equipment for Field As Well As Indoor Maintenance activitiesHandheld Temperature CalibratorPortable Pneumatic CalibratorDocumenting CalibratorMultimetersTong Testers (DC & AC)Multipoint Event RecordersShaker Table / Calibrator For Vibration Pick UpsStroboscope


C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power PlantLaboratory & Calibration Set Up

Electronic Test BenchPneumatic Test BenchOscilloscopePC Based Onboard IC TesterSoldering Station with Temperature ControllersTemperature Bath Dry Block Temperature Calibrator With RTIStandard Pressure GaugesVacuum Pump


C&I Department, Bakreswar Thermal Power Station*A Note on Maintenance of C&I Systems In Thermal Power PlantChallenges Before C&I MaintenanceThe Obsolescence FactorDeveloping the Knowledge BaseImport Substitution



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162920171-Maintenance[1].ppt