In chemical tankers one crucial concern is the control of thermal insulation of the tanks. Chemical tanker construction techniques may vary, but usually the tanks, as stand alone sandwich structures, are put inside the bulk almost at the final stage of the ship construction. In the case of the present survey, the tanks were composed of three main layers: a framed inner metal surface; a polyurethane (PU) foam layer; an outer thin metal plate surface. The PU is applied by injection between the metal layers. The main parameter to control during this operation is the PU density: a not homogeneous distribution of PU can lead to a bad insulation. To check the quality of the insulation, the inner space of the tank could
be heated and the temperature distribution of the outer surface monitored through an IR camera (check of thermal leaks). This methodology is well suited if the survey is carried out on the tank before the installation on board. For tanks already installed, as in our case, it is difficult to analyse the tanks by managing the camera in the narrow hollow spaces between tank and bulk. So a refrigeration plant has been used in order to lower the temperature inside each of the tanks below 0 °C. The IR analysis has then been conducted on the tanks inner surfaces in order to highlight possible hot spots
due to thermal fluxes from the outer to the inner surfaces.