A casing for a rotating machine includes a first fixed segment, and a second segment rotating along an axis of rotation (X-X). The first segment and the second segment are in contact along an interface provided with a sealing element. The sealing element is positioned in a housing connected to the internal volume of the casing, and also to the surrounding medium. The connection between the housing and the surrounding medium is made via a duct. The first casing segment or the second casing segment has a planer positioned at an outer end of the duct.