“Lack of Maintenance Leads to Costly Repairs”
The main component causing downtown for turbines is the gearbox, which if it fails can cost 15-20% of the price of the turbine to replace. Furthermore, failure to monitor and replace oil as needed can lead to wear on bearing and gears, causing greater financial loses than simply replacing the part.
Wind Turbine Maintenance & Condition Monitoring
Wind turbines are unmanned, remote power plants which, unlike conventional power stations are very much exposed to highly variable, harsh weather conditions, ranging from calm to severe winds and conditions ranging from tropical heat, lightning, arctic cold, hail and snow. In addition, because of these external variations, wind turbines undergo constantly changing loads, unlike conventional power plants.
As a result of these highly variable operational conditions, there is high mechanical stress on wind turbines unmatched in any other form of power generation, and they therefore demand a high degree of maintenance to provide a safe, cost effective and reliable power output with acceptable equipment life.
Maintenance approaches in all industries can be broadly classified into three major groups:
Reactive Maintenance (run to failure)
Preventive Maintenance (time-based)
Predictive Maintenance (condition-based)
The wind industry currently uses only Reactive Maintenance (fix it when it breaks) and Preventive Maintenance (following the wind turbine manufacturer’s service manual), and is not yet well versed in the newer forms of maintenance collectively known as Predictive Maintenance, which uses high tech condition monitoring technologies. Predictive Maintenance techniques and strategies are well known in more mature industries, such as in the energy (oil & gas) and utilities (coal and nuclear) sectors, as well as in the aircraft, military and major processing sectors, and the purpose of this paper is to demonstrate the benefits which the wind industry can expect from adopting these more modern predictive techniques and strategies to maintenance (collectively known as “PDM”) from these other, more mature industries.
Preventive and Predictive Maintenance Strategies for Wind Turbines for a Proactive Approach to Wind Turbine Maintenance:
Preventive, or time-based, maintenance activities should, at a minimum, be followed according to the turbine manufacturer’s manual, supplemented by additional time-based items prescribed as a result of the real-world experience of the maintenance contractor. These activities usually comprise time-based turbine visits set at 6 month intervals, and include mechanical activities such as fluid level checks, greasing, bolt torque checks, filter changes, inspection of blades, inspection of brake pads, as well as electrical activities such as inspection of cable connections, fuse checks, voltage level checks, battery inspections, trip tests and electrical cable inspections.
These activities are essential, and their effectiveness can be greatly enhanced by the feedback obtained from coordinated predictive maintenance activities. It is even possible that some time-based activities may be reduced in frequency and scheduled only when indicated by the test results from the predictive maintenance activities.
Predictive, or condition-based, maintenance activities can be broadly summarized as comprising equipment tests based on the use of on-line and off-line sensors and tests. The goal from these predictive maintenance activities is to produce an equipment condition assessment. They allow the plant owner/operator to plan in advance for ordering parts, scheduling work and planning for the repair-refurbish activities. A well organized predictive maintenance strategy, using state of the art sensors and tests will minimize unplanned turbine outages and maximize turbine energy output and revenue generation.
Experience has shown that wind turbine components routinely fail, to varying degrees, significantly before their design life is reached, resulting in significant unplanned (unscheduled) and therefore costly repairs, which is a problem be-devilling the wind industry in relation to the modern MW-class of wind turbines. Predictive maintenance tools installed on critical components, like gearboxes and generators, dramatically reduce the threat of sudden and unexpected failures in these components.