A valve for draining off gas from a centrifugal separator includes a valve body having a central axis around which the valve may be rotated; a cavity arranged at a radial distance from the central axis and including a valve ball and a valve seat; at least one drain channel extending from the valve seat of the cavity to the outside of the valve body; and at least one gas intake extending from the outside of the valve body to the cavity. The valve ball is in a relaxed state within the cavity and thereby arranged to float on a liquid surface present within the cavity, and thereby being movable in the cavity in the radial direction from rotational axis from a closed position, in which the ball rests against the valve seat and thereby blocking gas in the cavity from entering the at least one drain channel, to an open position, in which the valve ball is at a longer radial distance from the axis compared to the closed position, and in which open position the valve ball does not block the valve seat and thereby allowing gas in the cavity to drain from the valve via the drain channel. A centrifugal separator and a method for draining gas from the inlet of a centrifugal use the valve.