Threaded Bolt Crack and Corrosion Mapping

Customer Need

Threaded bolts are an essential part of any large construction such as bridges, offshore platforms and even buildings. To ensure the structural integrity of such large structures the full volume of the bolt, especially the threaded area should be evaluated on a regular basis. A simple phased array exam may be performed without dismounting the bolts.

The phased array image is capable of readily displaying thread degradation such as corrosion, defects and cracking and facilitates the decision making process for further action.

The detection of corrosion within the threaded area is preferably carried out using the sector scan of straight beam phased array probes. The probe is rotated by 360° on the bolt such that the sector scan fully covers the threads. The lefthand figure displays such a sector scan, in which single threads are resolved and the corroded area is detected by a significantly increased reflection signal (red area). To ensure steady and uniform coupling, the probe features uses a non-abrasive protective membrane allowing for coupling on rough surfaces and increasing the probes’ lifetime. These features result in an improved measurement, reliability and accuracy.