A valve comprises a valve housing (2) with a valve inlet (11), a valve outlet (12) and a passage (66) extending through the valve housing (2) from the valve inlet (11) to the valve outlet (12). A valve seat (5) is provided in the passage which comprises a valve sealing surface (50). Further, the valve comprises a blocking element (3) adapted to be moved at least partly into the valve seat (5) for blocking the passage by abutment on the valve sealing surface (50), the blocking element being moved along a direction (102) extending under an acute angle to the plane (90) in which the valve seat (5) is arranged. The valve sealing surface (50) of the valve seat (5) is spherical in shape.