Predictive Maintenance in Wind Turbines
Maintenance in any form of machinery can be reactive when machineries are run to failure points. Preventive maintenance, is time based and predictive maintenance is condition based.
Wind turbines are power plants set up generally in remote areas and largely remain unmanned.
They operate totally exposed to the vagaries of the weather whether it be heat, cold, rain or storms. In addition to all these unpredictable conditions, wind turbines because of the nature of their motive power which is the wind, have to operate at constantly varying speeds. Wind turbine operators generally perform maintenance on turbines which is either reactive or preventive. The remoteness of these turbines is a factor in maintenance.
Reactive maintenance costs are the highest because attendance follows breakdown of machinery and probably replacement of costly parts and downtime of the equipment. Preventive maintenance requires the posting of personnel to follow the required schedules and for wind turbines logistics can be a major problem. Predictive maintenance is like the JIT principle and is maintenance done exactly when it is required. Therefore, costs tend to be lower with vibration predictive maintenance.
Predictive maintenance is essentially condition based maintenance and it is possible to install equipment on critical equipment in wind turbines like gearboxes and generators. Because of the low and constantly varying speeds in wind turbines, vibration frequencies have to be noted over a much broader range of operating conditions. Measuring the overall vibration level by locating the transducer measuring the vibration as close to the bearings on gear boxes is a simple way of measurement.
Vibration measurements are best taken in all three dimensional axes, as certain vibrations may otherwise remain undetected. These measurements have to be trended over time and compared with known vibrations when the turbine is running smoothly. It is possible to set up equipment measuring vibrations that will send information from these remote locations to control centers. These control centers have software that constantly evaluates the data and posts warnings whenever such vibrations are near to limits or deviating constantly from safe conditions. This allows the plant operators to immediately rush maintenance crews to a wind turbine location to rectify the faults that are predicted.
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