Wind turbines experience numerous loading scenarios across the lifecycle of assets and fleets, including temperature cycles, cyclic loading, and static loading. For example, in some geographic regions, such as the southern U.S. and in parts of Europe, temperature extremes at wind turbine sites can vary from about 95 degrees Fahrenheit (°F) in the summer months to about -40°F in the winter months.
On the one hand, wind turbines put in place during a temperature of about 45°F can undergo a shift of about 50°F in the summer months, causing bolts to stretch due to metal expansion at the tower flange joints. On the other hand, the winter months can lead to temperature swings of about 90°F, reducing bolt tension as a result of metal contraction at the tower flange joints.
Further, wind power technology leaders warn that the seasonal cycling of thermal expansion and contraction due to the changes in temperature, compounded by other environmental factors, can significantly loosen bolted joint assemblies — if the proper torque and pre-tensioning values are not used during construction and maintenance, to maintain a minimum clamping force.
Accordingly, it is mission-critical for wind power stakeholders and contractors first to monitor weather conditions and temperature events across the lifecycle of wind turbines, from new construction and commissioning (Cx) to ongoing operations and maintenance (O&M) to repowering and recommissioning (RCx), and second to always use the proper torque and pre-tensioning values when servicing fasteners.
Keywords
Cx, EHS, O&M, RCx, STO, bolted joint assembly, bolts, clamping force, commissioning, construction, construction industry, contractors, environment, environmental factors, environmental work hazards, fastener, fastener service, fastener service conditions, health, offshore wind farm, onshore wind farm, operations and maintenance, pre-tensioning value, recommissioning, repowering, safety, shutdowns-turnarounds-outages, temp, temperature, thermal contraction, thermal expansion, torque, tower flange joints, weather, weather events, weather hazards, wind, wind farm, wind power, wind power contractors, wind power technology, wind turbine, wind-turbine technicians, wind-turbine tower
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(Source: Kilcollins, Wayne. Maintenance Fundamentals for Wind Technicians. Clifton Park, NY: Delmar Cengage Learning, 2013. Print.)
(Image Source: ITH Bolting Technology)
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