Cylindrical, refractory, hollow brick

Cylindrical, refractory, hollow brick, the peripheral surface (U) of which extends between a top surface (18) and a bottom surface (16) and comprises eight external surface portions (12f, 14f) disposed at an angle to one another, with in each case two diametrically opposed surface portions (12f, 12f;

• 14f, 14f) extending parallel to one another, having a central longitudinal axis and a through channel (20) extending coaxially relative to the central longitudinal axis (M), characterized by the following features:
• the channel (20) is peripherally delimited by eight internal surface portions (12i, 14i) disposed at an angle to one another;
• in each case two diametrically opposed surface portions (12i, 12i;
• 14i, 14i) extend parallel to one another;
• the hollow brick (10) comprises corner wall regions (14a-d) connected together by interlying wall regions (12a-d), each wall region being externally delimited by one of the eight external surface portions and internally delimited by one of the eight internal surface portions, the external surface portion for each region being parallel to the internal surface portion of the region;
• the corner wall regions (14a-d) have a wall thickness (D2) which is 15 to 35% less than the interlying wall regions (12a-d);
• the hollow brick (10) is fashioned in such a way that upon rotation through 90.degree. about the central longitudinal axis (M) the original geometry is reattained;
• in which the corner wall regions (14a-d) have a wall thickness which is 20 to 22% less than the interlying other wall regions (12a-d);
• in which the corner wall regions (14a-d) have a wall thickness of 30 mm+/-5 mm;
• in which the surface portions (12f, 14f, 12i, 14i) are flat;
• in which the surface portions (12i, 14i) are connected at connecting regions (22), the connecting regions (22) of the surface portion (12i, 14i) of the channel (20) having a rounded-off construction;
• in which the corner wall regions (14a-d) are constructed with recesses;
• in which the interlying wall regions (12a-d) having a greater wall thickness (d1) are constructed with recesses (24),
• in which the recesses (24) extend from the bottom surface (16) of the hollow brick (10);
• in which the recesses (24) have an archway profile;
• in which the corner wall regions (14a-d) have on their top surface (18) raised portions for positively receiving the corresponding recesses;
• in which the interlying wall regions (12a-d) having a greater wall thickness (d1) have on their top surface (18) raised portions (26a, 26b) for positively receiving the corresponding recesses (24),
• in which the height of the raised portions (26a, 26b) (viewed in a direction of the central longitudinal axis (M)) is at the most 20% of the height (H) of the recesses (24);
• in which the recesses (24) at the bottom surface (16) have a width (B) which is greater than their maximum height (H), viewed in a direction of the central longitudinal axis (M);
• and
• in which the recesses (24) at the bottom surface (16) have a width (B) which is at least 80% of the width of the associated outer surface (12f).