FIELD: metallurgy. SUBSTANCE: arrangement has inner tube secured to vessel and having at least one hole. End flange of outer tube rotates about inner tube. Outer tube moves from closing to opening position. To prevent bridging in holes of outer tube, relative positioning of hole in inner tube and end flange of outer tube is fashioned so that end flange extends through the hole in the course of movement of the outer tube. EFFECT: enhanced efficiency of the arrangement. 6 cl, 6 dwg
