Abstract: For cleaning and/or drying the inner walls of projected pipelines the pressure in the interior of the pipeline is decreased and the vapor formed by evaporation of the substance adhering to the pipe inner wall and, if applicable, present foreign gases are exhausted from the pipeline. Upon exit from the pipeline and prior to entry into the exhausting apparatus, the exhausted medium passes through a condensating apparatus whose cooling surfaces are maintained at a temperature that is lower than the pipe wall temperature. With a temperature difference sufficient to condense the substance vapor on said cooling surfaces it was possible to considerably enhance the drying rate as compared to pure vacuum-type drying.