In this case study, we will explore the reasons why the HARDLOCK NUT has been preferred over standard double nutting for hundreds of noise barrier projects over the past 50 years. Inexpensive loosening prevention systems such as U-Nut, Nyloc Nut have been trialed, but loosening still occurs. U-Nut and Nyloc Nut does not work well with bolts with varied thickness or thick plating such as hot dip galvanized coatings. Maintenance work is also considered to ensure the nuts can be easily installed. HARDLOCK NUT has helped increase the lifetime of noise barriers and are a vital safety component complementing fall prevention cable systems.

Previously, double nutting was the main method of tightening anchor bolts. Of the thousands of nuts installed, if one or two are found loose, it becomes a liability. If anchor bolts are not installed properly (ex: being slightly angled to the concrete surface), it leads to uneven surface pressures on the nut clamping face. The bolts and nuts are plated with galvanized zinc, resilient to corrosion, but do not allow for proper engagement between threads, leaving a considerable gap which can lead to loosening. Wind pressures can also cause vibration, leading to nuts with bad torque to be loosened.

HARDLOCK NUT has been trusted for over 50 years in many major highways and railway barriers. HARDLOCK NUT is suitable for thinner worn-down bolts and galvanized zinc plated bolts, preventing improper engagement, locking the threads with the wedging principal. Unlike other self-lock nuts, HARDLOCK NUT does not utilize the clamping surface to prevent loosening. This allows HARDLOCK NUT to work even for slightly angled anchor bolts. Also, clamp load can be lost due to non- rotational loosening.