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Bolts are used as the fasteners on various sections of the Offshore Wind Turbine (OWT), and they require regular Non Destructive Testing (NDT). The current procedure requires permanent strain gauges, single element ultrasonic inspection, or a mixture of both in order to ensure that the specific preload is maintained throughout an OWT’s operative cycle. Both of these methods have drawbacks: Strain gauges are mainly used on a smaller, experimental scale; and the ultrasonic method, traditionally carried out using single element transducers, has low accuracy and, additionally, the existence of the volumetric defects in the bolt (or a corrosion layer) can affect the stress measurement. This paper suggests a novel method to test bolts in an OWT quickly and efficiently, using a Phased Array Ultrasonic Transducer (PAUT) probe as opposed to a single element transducer. A PAUT probe has the ability to produce both a swept scan and a linear A – scan for each pair of transmitting and receiving elements or, if using the Full Matrix Capture (FMC) technique, a number of acoustic paths equal to the number of elements squared (i.e. 400 paths if using a 20 element probe). A sector scan was initially performed to identify and roughly size defects, and if any were detected that were within the acceptance criteria a second, targeted scan was performed. Following this, the probe was moved to an optimum position where the acoustic paths will have minimal interaction with the defects and an FMC scan to measure Time of Flight (ToF) was performed, which allowed for stress calculation. To justify the necessity of considering small acceptable defects in the follow-on …