Abstract: A valve consisting of a housing (1) provided with a flow-through passage (4), of a closing member (2) having the shape of a rotational body or part of a rotational body and provided with an aperture (6), and turnably disposed in said flow-through passage, and of a sealing member (3) disposed between the closing member and the housing. Between the sealing member (3) and the housing (1) has been arranged an intermediate space (8) in which when the valve is in closed position prevails a pressure urging the sealing member against the closing member (2). From said intermediate space (8) leads a passage (12) to a point close to that portion of the sealing member (3) adjacent to which an aperture communicating with the flow passage is first established when the valve is being opened.

Abstract: Valve which consists of a body (1) provided with a flow passage, of a closing member (2), such as, e.g., a flap, fitted in the flow passage (3) pivotably or turnably and having no passage opening, and, if necessary, of jointly operative sealing members (6) fitted between the closing member (2) and the valve body (1). In the flow passage (3) in the valve body (1), after the closing member (2), at the outlet side of the flow, one or several attenuation member or members (9) are fitted, which are placed one after the other at a distance from each other and from the closing member (2), which the closing member is in the closed position, and which reduce the cross-sectional area of the flow passage (3). The attenuation member or members (9) may be provided with holes or openings (12) passing through them.