A high humidity content can often accumulate at different stages in the production process in thin metal pipes such as, for example, brake lines, cooling pipes and pressure pipes. This condensation insite pipes cannot escape independently with pipe lengths of more than 6m and leads to a too high tube interior humidity. Hence, quality control checks must be carried out during production on the residual moisture in these pipes which are of high-grade steel, brass or copper in order to detect and dry out the condensation insite the pipes.