Tightening-up on standards
Engineers are considering bolt tightening more carefully as standards, materials and assembly methods change. Should not fitters require similar accreditation to welders? The need for documented records of assemblies on a global basis is critical as design and cost is optimised. The introduction of new coating materials with different friction factors, protection against hydrogen embrittlement, greater appreciation of embedment, and assembly in far flung places by sub-contractors require documented verifiable records of tightening.
Reduction in guarantee claims by itself can justify the small additional cost but the added benefit for Condition Monitoring in later years and the limited access to offshore wind turbines and production platforms are generating a strengthening affection for reliable ultrasonic measurement of the clamp load from erection onwards and a consequent reduction in risk.
The stately rotation of wind turbine blades betray the high wind shear across the rotor, the vibration induced by turbulent air with all the consequent twisting and flexing of the 70 metre long composite blades. When combined with the whip from the tower and the buffeting of the storm driven waves the loads on the anchorage bolts alone cause concern over the measured clamp load.
Tightening to load, be it with an automatic tensioner or wrench working with the Intellifast system is simple, well proven and can be used at ambient and high temperatures up to 310 C. Accuracy of +/- 3 per cent is normal and 6 per cent where bending is occurring. The Intellifast system provides for immediate downloading of all the tightening parameters for rapid inspection. Best of all it is fast and saves valuable time.