The Inspection of Tube Fitting Systems in use for Drinking Water Supply by Means of Neutron Imaging Methods

Metallic fittings as the connection between tube ends are heavily applied in domestic, public and industrial buildings where drinking water is distributed. Given by the manufacturing and joining process, there are spaces left between the fitting and the tube, which either can stay empty or filled with residual water amounts over time. We looked for an efficient non-destructive method which allows measuring the filling of the system as well as the subsequent water exchange in order to evaluate new designs. It was tried with the help of neutron imaging techniques to detect and to visualise the amounts of such residual water under different conditions in respect to the applied external pressure. Neutrons are preferable for such kind of investigations because they can easily penetrate the metallic structure, while detecting small water amounts with high sensitivity. Due to the performance of the used digital detection system, it was possible to enhance the contrast and the image quality by using a referencing procedure. The successfully performed investigations at the neutron radiography facility NEUTRA at PSI can now be compared with model calculations based on dedicated diffusion approximations.