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Application Notes:
Thermal Predictive Maintenance at a Coal Plant |
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As monopolies, electric utilities are charged with providing the highest quality product to the public at the lowest possible cost. Simultaneously, as publicly owned companies, they also need to generate a return on investment for their shareholders. They have a fiduciary responsibility to operate efficiently, and predictive maintenance is an essential component in fulfilling this responsibility. While many people in the power generation industry are familiar with annual infrared thermography surveys as part of PdM, the coal plant in this case study uses a thermal imager year round. There are two differences in their approach.
Power distributionDelivering consistent, reliable electricity is the highest priority for a power generator. For this reason, the primary use of infrared thermography at this plant is regular monitoring of power distribution equipment.
SwitchyardSwitchyard inspections are normally performed during the pre-dawn hours in order to avoid solar reflections and effects from wind. During pre-dawn, the load is lighter but the air is usually calm, so any problems that are observed are certain to be significant, as they will be much hotter during the period of peak load.
Boilers, pipes, traps and valvesWhile delivery of electricity is essential, efficient production is equally important. At this coal plant, for example, steam is produced from coal fired boilers and electricity is produced from steam driven turbines. When steam valves leak or fail, high energy content steam or water blows through to the condenser.
MotorsAt most plants with in-house imagers, nearly all of the infrared analysis is qualitative and comparative, examining similar pieces of equipment under similar load. A primary example is the inspection of the pulverizer motors.
In advanced PdM systems, each aspect of the system may have its own monitoring program. For example, this coal plant should have a motor casing monitoring program, where the case temperature for each motor is regularly examined.
Prioritizing problemsInfrared thermography helps identify maintenance needs but prioritizing the problems requires thoughtful evaluation of many factors. The most significant problem is not necessarily the one with the hottest apparent temperature.
Basic vs. advanced thermographyMuch of the equipment in coal-fired power generating stations can be efficiently inspected using comparative infrared analysis. In this case, the plant continued to hire out the annual survey, so that it had professional thermal images of all critical equipment to compare their own images to during the year.
While issues like emissivity are minimized by dirty metal surfaces, other issues like reflections, convective losses due to wind, and other conditions can lead to erroneous conclusions.
More advanced infrared thermography involves learning the principles of heat transfer...
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