Shutoff device

A shut-off device for shutting-off and opening flow through a conduit comprising a housing (10) provided with a passage (11), a device (13) movable in said housing (10), said device (13) having an opening portion which registers with said passage (11) in a first position and a closing portion which registers with said passage (11) in a second position, an opening (14) in said opening portion, an annular sealing body (28) arranged around the passage (11) on each side of the device (13), each annular sealing body (28) having a contact surface (34) which contacts a contact surface (38, 39) on each side of the device (13) at the respective opening and closing portions thereof in the first and second positions, the device contact surfaces (38, 39) being a hard material layer which is harder than the material of the device (13) and has a surface roughness of less than 10 μm, said device contact surfaces (38, 39) are each of a substantially annular configuration, one of said annular device contact surfaces (38) at each side of said device (13) at said opening portion substantially surrounds said opening (14) in said first position, and another of said annular device contact surfaces (39) at each side of said device (13) at said closing portion seals against said annular sealing body contact surfaces (34) in said second position.