Abstract: A closure for a pressure vessel having a collar connectable to the pressure vessel and to a cap, a seal disposed in an area where the collar and cap contact each other, and a plurality of clamping elements for generating the surface pressure between the collar and the cap. The collar comprises an integral sealing flange having an upper flat sealing surface and a lower circumferential annular bead at least partially circular in cross-section. A plurality of C-shaped clamps are displaceably, releasably and form-fittingly held on said lower circumferential annular bead. Each C-shaped clamp comprises one pressure screw and constitutes a clamping element. In the operational state of the closure, the C-shaped clamps press on the edge region of the cap resting on the sealing flange of the collar.