An improved tool assembly for enhancing the surface of a heat transfer tube is provided. In the opening, a source electrode is formed to cover an insulator. In addition, the tank includes a leaktight bell arranged inside said container, said bell being over the over-pressure valve and surrounding the over-pressure valve at least in part so as to hold air captive in order to isolate the over-pressure valve from the fuel content when said pressure is below said threshold. At all times, the axes of rotation of the handholds are parallel to each other and extend along a plane that contains the axis of circumduction of the user’s shoulders.