A pre-stressed concrete pipe is made by casting a concrete pipe inside a metal cylinder and then being pre-stressed by injecting solidifying compound under pressure into the boundary between the metal cylinder and concrete pipe, and includes a pair of end rings within the metal cylinder, each having a metal ring with an annular groove and an elastic band having a curved end to provide a rounded corner on the concrete pipe. After the solidifying compound is solidified, the concrete pipe retains the compression increasing its strength to withstand pressure, and moments caused by external loads. The pre-stressed concrete pipe further includes a bell ring mounted at one end and a spigot ring having a gasket ring at the other end. A bell clamp is mounted on the bell ring.

Method for rotolining metallic hollow articles with metallocene-produced polyethylene.

Method for rotolining metallic hollow articles with metallocene-produced polyethylene.

A method for producing a round tube from a ceramic material or a glass-ceramic material or mixtures thereof is described. The method comprises introducing a silicate-ceramic, oxide-ceramic and/or non-oxide-ceramic material-forming agent into a melting vessel, which has along a longitudinal axis a tubular wall which defines a tubular cavity, wherein the melting vessel rotates about its longitudinal axis. A uniform layer of the ceramic and/or glass-ceramic material-forming agents is thereby formed, lying on the inner side of the wall, by means of centrifugal forces generated by rotation and is heated by means of a heat source arranged in the inner cavity of the melting vessel until at least the inner side of the layer of material-forming agents has melted. Such tubes can be used for various industrial purposes.

A method for producing a round tube from a ceramic material or a glass-ceramic material or mixtures thereof is described. The method comprises introducing a silicate-ceramic, oxide-ceramic and/or non-oxide-ceramic material-forming agent into a melting vessel, which has along a longitudinal axis a tubular wall which defines a tubular cavity, wherein the melting vessel rotates about its longitudinal axis. A uniform layer of the ceramic and/or glass-ceramic material-forming agents is thereby formed, lying on the inner side of the wall, by means of centrifugal forces generated by rotation and is heated by means of a heat source arranged in the inner cavity of the melting vessel until at least the inner side of the layer of material-forming agents has melted. Such tubes can be used for various industrial purposes.