Programme of work
TWI, as a certified holder of HSE consent for industrial radiography practices, had to ensure all necessary safety practices were in place prior to commencement of any inspection using ionising radiation. This included creation of, and adherence to, bespoke Local Rules, Risk Assessment and Method Statement.
Selection of the correct radiographic equipment was crucial to the success of such a large-scale, complex inspection. The X-ray generator needed to be suitably portable to be manoeuvred around the boat
and to allow all shot angles to be accomplished. It also needed to have a suitably low focal spot size so as not to introduce blurring from the inherent geometric magnification in the image. The key factor for the digital X-ray detector was its portability, ability to be positioned independently of cabling and being able to communicate wirelessly. The boat, constructed from relatively low-density composite, also required a sensitive 16-bit detector to distinguish subtle image contrast changes.
The most suitable approach that allowed the inspection of the entire hull-to-deck joint, including bulkheads, required that both the digital detector and the X-ray generator were positioned on the outside of the boat (Figure 1).
Initially, only the port side of the boat was inspected which resulted in the acquisition of 102 individual digital radiographs. The use of digital radiography as opposed to film radiography considerably reduced inspection time as chemical processing of film was not required.
The interpretation of the radiographs revealed some internal features in the joint region. Figure 2 shows a radiographic image demonstrating minor flaws where
the adhesive, injected from different points had not quite met, creating two small gaps.