Abstract: Detensioning of expanded tubes is brought by way of an installation using a rotopeening method. The tool is constituted by a cage moved along a helical path centered on the axis of the tube to be treated. The cage supports in rotary manner a shaft, whose axis is parallel and offcentered with respect to that of the cage. The shaft carries flexible plates, called brushes, whose ends are equipped with shot able to peen the inner wall of the tube during the rotation of the shaft. The helical path ensures a regular distribution of the impacts and consequently a uniform treatment of the surface.