Abstract: A shut-off device (1) includes a housing (2) and a butterfly valve (4). The butterfly valve (4) can be swivelled using a drive shaft (3). When the butterfly valve (4) is closed, the butterfly valve (4) is sealed off from the housing (2) and from the pipe connection by an annular seal (7). The annular seal (7) is held on a face (5) of the housing (2) by a backup ring (6). The annular seal (7) is attached to the backup ring (6) using two annular projections (11, 12). The two annular projections (11, 12), respectively, interface with annular grooves (13, 14) provided on the backup ring (6). A fluid pressure chamber (22) is formed between the backup ring (6) and the annular seal (7), and a fluid connection pipe (24) extends through the backup ring (6) into the fluid pressure chamber (22).

Abstract: The invention relates to a shut-off device (1) comprising a single-part housing (2) insertable in a pipeline, and a butterfly valve (4) swivellable by a drive shaft (3) wherein said butterfly valve (4) in its closed position is sealed off from the housing (2) and from the pipe connection, by a distensible entropy- elastic annular seal (7) of U-shaped cross section to which fluid can be applied, with said annular seal (7) being held by a backup ring on a face (5) of the housing (2).