FIELD: operation of trunk pipelines and branching systems of pressure pipelines. SUBSTANCE: collars are made flexible with different diameters. With piston moving horizontally or in sloping pipeline down ward, diameters of two latter collars of shutoff piston and of three first collars of the smoothing piston are larger than the inner diameter of the pipeline. When piston move upward in inclined pipeline the diameters of the three latter collars of shutoff piston and two first collars of smoothing pistons exceed the internal diameter of the pipeline inner diameter. EFFECT: increased uniformity in thickness of applied protective layer with simultaneous improvement of adhesion and setting the parameters of protective layer thickness in pipeline of different gradient in laying. 3 cl, 4 dwg
