IHF Fasteners are specially optimized for tension loaded bolted joints in steel and mechanical engineering and designed for hydraulic friction- and torsion-free tightening "ITH Stretch Method". The combination of fastener and tightening method forms the IHF Bolting System.
The ETA-certified fasteners IHF Stretch Bolt, IHF Stud Bolt and IHF Round Nut have been specially designed for tension-loaded bolted joints in steel construction, such as those found on ring flanges of wind turbine tower segments. A long-term study based on ultrasonic measurements proves this: The measured residual preload forces are within a narrow tolerance band and are so precise that the bolted joints are installed according to a specified bolting process and do not need to undergo any further checks. For this purpose, online cloud ultrasonic-based measurement techniques are also used serially to provide verification.
From this circumstance, the bolted joint is defined as "maintenance-free".