Pedestal-mounted rotating cranes are fitted with slewing bearings to allow 360-degree rotation. The slew bearing is subject to high loads and frequently harsh conditions, which can give rise to rapid catastrophic failure and unwanted consequences, including severe injury or fatalities.
Regular tilt clearance measurements (frequently known as The Rocking Test) are essential to identify a failing slewing bearing.
The video "The Rocking Test" shows the most common method to correctly carry out a rocking test and obtain meaningful data, which will identify if the slewing bearing is failing and if the crane needs to be withdrawn from use for repair before catastrophic failure.
Full video at the following link: