Design of the optimal UV LED source for the efficient curing of protective coatings for pipes inner surfaces and compressed gas cylinders

The use of ultra-violet (UV) radiation for the curing of polymeric coatings is a new efficient, and sustainable technology, widely used for the coating of surfaces with easy access by a light source. The recent introduction of the UV-LED lamps has reduced the dimensions of the UV sources, opening the way to new applications such as UV inks for printers and UV protective paint for wood (1). However, the UV protective coatings of steel products with closed narrow spaces, like tubes and gas cylinders, is still an unexplored field. The study of UV irradiance in these environments has specific issues due to the closed geometry; the possibility of UV light reflection; dimensional restrictions; small space of movement and problems of heat disposal released by the lamp. Thus, the irradiation effectiveness of an UV-LED array source, has been here analyzed using as target surface to be irradiated, the inner surface of a cylinder. The study has been developed using an algorithm starting from the geometry of the internal surface and from the curing parameters defined by the UV LEDs producer, can determine an optimized irradiance model and the relative resulting UV-LED source. As a result, the optimal UV-LED radiant source for a certain cylindrical surface has been here defined, based on a hexagonal extruded support with strip LEDs fixed on each side, for a total amount of UV LEDs of 120 units. This shape has been defined as the best compromise between the dimensional constraints and the uniformity of the light flow applied into pipes and gas cylinders diameters about 30 mm.