The appts. intended for blocking high-temp. gaseous media consists of a housing (1) with cooled seats (2,3) and a cooled movable blocking element. With the exception of the seats and the blocking element, all surfaces of the appts. coming in contact with hot gases are provided with a refractory lining which at least in parts is made up of two or more layers. There is layer with high heat insulation between the metal structure (13) of the housing and the layer (15) of the lining in contact with hot gases. The layer has micro and/or macro cavities (14).
