fax 01-972-952-9435. AbstractThis paper describes the development of a Time Domain Reflectometry (TDR) method applied subsea to verify the insulation integrity of electrically heated flowlines 1 . The proven TDR method is suited to direct electrical heated flowlines in deepwater remote locations post-installation and during operational life of the flowlines. The paper describes the qualification philosophy, the creation of robust components through testing, the equipment operation and example TDR results. The Time Domain Reflectometer (TDR) for this application delivers risk reducing data to the benefit of offshore exploration and production operators where electrical heating pipe-in-pipe flowlines (EHPIP, or referred as EHF) have been employed in subsea developments.