1. Seminar 2005-3 Predictive Maintenance Technologies in Nuclear Power Plants - An Introduction 20 June 2005 Center for Advanced Reactor Research Jun-Seok Lee

2. 2 / 24 Contents I.Introduction II.Predictive Maintenance Program III.Predictive Maintenance Technology IV.Summary and Further works V.References

3. 3 / 24 I. Introduction Maintenance Strategies Corrective maintenance Reactive approach. Restoring a failed product or system to an operational state Preventive maintenance Proactive approach. Periodic maintenance Consisting of servicing, parts replacement, surveillance or testing at predetermined intervals. Predictive maintenance Performed continuously or at intervals and governed by observed condition to monitor, diagnose or trend system condition indicators.

4. 4 / 24 I. Introduction Reliability-Centered Maintenance (RCM) A process that is used to determine the maintenance requirements of any physical asset in its operating context. Focus Effect of failure in the mission. Reducing the probability of occurrence of the failure modes RCM ⇒ Periodic maintenance ↓ Predictive maintenance ↑

5. 5 / 24 I. Introduction AdvantagesDisadvantages Corrective Maintenance  Low Cost  Less Staff  Increased cost due to unplanned downtime of equipment.  Increased labor cost, especially if overtime is needed.  Cost involved with repair or replacement of equipment.  Possible secondary equipment or process damage from equipment failure.  Inefficient use of staff resources. Planned Maintenance  Cost effective in many capital intensive processes.  Flexibility allows for the adjustment of maintenance periodicity.  Increased component life cycle.  Energy savings.  Reduced equipment or process failure.  Estimated 12% to 18% cost savings over reactive  maintenance program.  Catastrophic failures still likely to occur.  Labor intensive.  Includes performance of unneeded maintenance.  Potential for incidental damage to components in conducting unneeded maintenance. Predictive Maintenance  Increased component operational life/availability.  Allows for preemptive corrective actions.  Decrease in equipment or process downtime.  Decrease in costs for parts and labor.  Better product quality.  Improved worker and environmental safety.  Improved worker moral.  Energy savings.  Estimated 8% to 12% cost savings over preventive maintenance program.  Increased investment in diagnostic equipment.  Increased investment in staff training.  Savings potential not readily seen by management. Reliability-Centered Maintenance  Can be the most efficient maintenance program.  Lower costs by eliminating unnecessary maintenance or overhauls.  Minimize frequency of overhauls.  Reduced probability of sudden equipment failures.  Able to focus maintenance activities on critical components.  Increased component reliability.  Incorporates root cause analysis.  Can have significant startup cost, training, equipment, etc.  Savings potential not readily seen by management.

6. 6 / 24 II. Predictive Maintenance Program Definition A process that requires technologies and people skills to integrate all available equipment condition indicators (diagnostic and performance data, operator-logged data), maintenance histories, and design knowledge and make timely decisions about maintenance requirements of important equipment. Objectives Improve availability Reduce forced outages Improve reliability Enhance equipment life Reduce wear from frequent rebuilding Minimize potential for problems in disassembly and reassembly Detect problems as they occur Save maintenance costs Reduce repair costs Reduce overtime Reduce parts inventory requirements Earn insurance credits

7. 7 / 24 II. Predictive Maintenance Program Procedure Detect incipient failures of equipment Determine the maintenance actions required Restore equipment to its operable condition after detection of an incipient failure condition Technologies Acoustic analysis Motor testing Oil analysis Thermography Ultrasonic testing Vibration analysis ……

8. 8 / 24 III. Predictive Maintenance Technology Acoustic Analysis Description The science that deals with the sound generation, transmission, reception, and effects. Usage & Application Acoustic Leak Detection The noise level changes with fluid flow indicate system integrity failure or an internal failure. Applications : Feedwater heaters, Valve internals and externals, tubes. Acoustic Crack Detection The transient elastic waves that are generated by the rapid release of energy. Able to detect very early crack growth. Applications : Reactor vessels and related piping, Control rod housing, Main steam lines, Transformers, etc.

9. 9 / 24 III. Predictive Maintenance Technology Oil analysis Description Analyzing used oil to know oil and machine condition. Achieved only by taking frequent samples and trending the data. Especially valuable with reciprocating machines, slow rotating machines, and hydraulic systems.

10. 10 / 24 III. Predictive Maintenance Technology Usage Oil condition Measuring cleanliness, viscosity, acid number, etc. Additional measuring anti-wear additives, corrosion inhibitor, etc. Oil wetted parts wearing Measuring Fe, Cu, Cr, Al, Pb, Ni, etc. Increasing specific wear metals ⇒ Wear taking place in a particular part. Presence of contamination Measuring water content, specific gravity, silicon level. Variation of specific gravity ⇒ contamination of another type of oil or fuel. Presence of silicon ⇒ contamination of dirt. Application Turbines, Electro-hydraulic control systems, Hydraulics, Servo valves, Gearboxes, Roller

11. 11 / 24 III. Predictive Maintenance Technology Thermography Description The process of monitoring condition of equipment through the measurement and analysis of heat. Typically conducted through the use of infra-red cameras and associated software. Usage Detection, identification, and measurement of the heat energy objects radiate in proportion to their temperature and emissivity. Midwave-range instruments detect infrared in the 2-to-5 micron range Longwave-range instruments detect the 8-to-14 micron range.

12. 12 / 24 III. Predictive Maintenance Technology Inspection Qualitative inspection : relative differences, hot and cold spots, and deviations from normal or expected temperatures. Quantitative inspection : accurate measurement of the temperature of the target. It must conduct by technicians who are thoroughly trained in the operation of the equipment and interpretation of the imagery. Application Electrical System : Transmission lines, distribution lines/systems, substations, generator facilities, in-plant electrical systems, etc. Mechanical System : Steam systems (reactor, valves, etc), Fluids, Motor, Rotating equipment

13. 13 / 24 III. Predictive Maintenance Technology Ultrasonic testing Description Sensing ultrasound waves produced by operating machinery and turbulent flow of leakage. Measuring methods Hearing sounds through a noise-isolating headphone. Incremental readings on a meter or display panel. Benefits Provide fast, accurate diagnosis of defects in the equipment. Easy (requiring minimal training) and the inexpensive instruments. Defects Insufficient for isolating the sources or causes of those vibrations.

14. 14 / 24 III. Predictive Maintenance Technology Usage Ultrasonic inspection of wear Deforming metal ⇒ Producing irregular surface ⇒ Increasing ultrasonic wave emission. Ultrasonic inspection of leak Small gap in the fitting ⇒ Fluid leakage ⇒ Ultrasonic noise emission. Ultrasonic inspection of arc, corona Jumping electricity across a gap ⇒ Disturbing air molecules ⇒ Ultrasound generation. Application Mechanical System : Bearings, Pumps, Motors, Gearboxes, Fans, etc. Electrical System : Switchgear, Transformers, Insulators, Junction boxes, Circuit breakers, etc. Pressure/Vacuum leaks : Heat exchanger, Chillers, Tanks, Pipes, Valves, Steam traps, etc. (1 mils = 1/1000 inch)

15. 15 / 24 III. Predictive Maintenance Technology Vibration analysis Description Detecting repetitive motion of a surface. Sensing displacement, velocity, acceleration of the motion. Determination of the cause and severity of faults or problem conditions. Usage Root of vibration Crack, pits and roughness in rolling elements. Unbalance of rotating parts. Shaft misalignment. Coupling problems. Bends, bows, and cracks in shafts Excess sleeve bearing wear Loose parts Misaligned or damaged gear teeth Deterioration caused by broken or missing parts Deterioration caused by erosion or corrosion Resonance of components Electrical effects

16. 16 / 24 III. Predictive Maintenance Technology Procedures Attaches a sensor to several specific places and records readings electronically. Downloads the data from sensor to a computer and analyzes with a software with the hand held instrument. Application Diesel Engine, Feedwater heater, Generators, Gears, Motor, etc.

17. 17 / 24 III. Predictive Maintenance Technology Motor Analysis Description Detecting an unsatisfactory condition before failure. Motor failures are attributable to bearings. Requiring high degree of skill and knowledge.

18. 18 / 24 III. Predictive Maintenance Technology Usage Electrical surge comparison Testing turn-to-turn insulation and conductor-to-ground insulation. Identifying insulation deterioration Applying a high frequency transient surge to equal parts of a winding Comparing the resulting voltage waveforms. Current signature analysis Using electric motor with a mechanical load as a transducer. Mechanical load variations ⇒ Electric current variations

19. 19 / 24 III. Predictive Maintenance Technology Miscellaneous Technologies Eddy Current Testing Description : Recording the effect on a field changes electromagnetic coil in a probe. Application : thickness of metal components, crack identification. Flow Testing Description Using Flow meter, Doppler flow meter, time difference flow meter. Measurement of reflection time of frequency of sound transmitted into the fluid. Application : Heat exchanger, diesel engine, etc. Precise timing testing Description Valve : Measurement of the elapsed time of an event series in sequence. Breaker : Measurement of the response time during the opening and/or closing operation. Application : Air operated valve, Motor operated valve, Circuit breaker, etc.

20. 20 / 24 III. Predictive Maintenance Technology Wireless technology Marketplace currently putting pressure on predictive maintenance groups Reduce size of data, hard-wire, sensor, etc. Monitor more equipment. Description Monitoring any sensor from which data are being transmitted without conventional hard- wire method. Detecting incipient faults more readily. Monitoring plant equipment independent of operation. Monitoring critical equipment on an as-needed basis, avoiding high capital costs to install new wiring. Increasing the amount of on-line monitoring is necessary! Wireless technology is an attractive method!

21. 21 / 24 III. Predictive Maintenance Technology Guidelines for Wireless Technology in Nuclear Power Plants (EPRI) Benefits and Consideration in the wireless technology application Implementation and Regulatory Issues in wireless technology application

22. 22 / 24 III. Predictive Maintenance Technology Future of predictive maintenance technology Fewer personnel collecting data and performing analysis. Bring the data to the analyst > the analyst going to get the data. Archiving data from similar machines. Combination of wireless transducer, plant network and internet.

23. 23 / 24 IV. Summary and Further works Summary Predictive maintenance program Predictive maintenance technology Acoustic analysis Motor testing Oil analysis Thermography Ultrasonic testing Vibration analysis Motor analysis … Future of predictive maintenance technology Further works Data analysis Advanced maintenance technology Maintenance optimization

24. 24 / 24 V. References 1.R. Keith Mobley, “An introduction to predictive maintenance”, Butterworth-Heinmann, 2002. 2.“Predictive Maintenance Primer”, EPRI technical report, 2003. 3.Nelson Baxter, “What is the future of predictive maintenance?”, Sound and Vibration, May, 2004.

25. 25 / 24 II. Predictive Maintenance Program Equipment and Predictive Maintenance Technologies