PRESTRESSED PRESSURE CAST CONCRETE OR MORTAR LINED STEEL PIPES WHEN IN OPERATIONAL USE THE PIPE PRESTRESS IS ELIMINATED

摘要

588368 Disclosed is a pressure cast lined steel pipe that is placed into fluid transport service providing improved mechanical properties. The pipe comprises an annular concrete or mortar liner forming an inside diameter of the pipe and a metal shell surrounding the liner. The liner is in direct contact with an inside wall surface of the metal shell, and the liner is in a prestressed state by the metal shell in an initial state prior to the pipe being placed into fluid transport service, and the prestress of the liner in a final state when placed into fluid transport service is essentially eliminated. The ratio of the wall thickness between the liner and the metal shell is in the range of from 5:1 to 80:1 and the wall thickness of the metal shell is in the range of from 0.06 to 0.75 inches, and the wall thickness of the liner is in the range of from l.5 to 10 inches. A coating of dielectric material is disposed along an outside surface of the metal shell. The concrete liner is formed in situ while an uncured concrete or mortar composition and the metal shell is pressurized by direct contact between uncured concrete or mortar composition and a fluid pressurizing medium to place the liner into a state of compression when the liner is cured and the pressure is released.