Can an expansion anchor be retightened to its nominal torque once installed?

An expansion anchor must be installed using a calibrated torque wrench and by applying the installation torque stipulated in the applicable documentation.

After a few minutes, the preload between the expansion element and the base material will loosen. This effect can be checked by re-applying the nominal torque to the anchor, which will turn again. This effect does not mean that the anchor is incorrectly installed. However, if the anchor does not rotate when retightening at nominal torque, it is a symptom that the anchor was initially installed with too much torque.

In any case, the anchors do not have to be retightened after installation.

Furthermore, expansion anchors should only be installed with torque wrenches; the use of impact machines is only recommended for concrete screws provided it is specified in their applicable documentation and the power limit is observed where necessary.