Improvement in closing covers of apparatuses such as concentrators-evaporators, ultracentrifugal and centrifugal apparatuses, in which a centrifugal rotor rotates in an enclosure in which a vacuum may be established. The cover is formed by a plate (11) which is guided in translation by projections (14a, 14b) traveling in guide rails (12) so as to maintain the cover in a horizontal position when it overlies the opening and allow the pivoting of the cover when it has been displaced in its plane to a releasing position.
