One reason of offset pipe joints is system deterioration in both pipes and manholes. Another one is ground movement, sometimes caused by nearby deep excavations. With the introduction of more ductile materials, bending stresses have become less of a concern; however, this is still of great concern for the old cast iron mains that can fail as a brittle fracture at a low strain. Rigid pipe deforms along with the ground displacement profiles as rigid links connected by points that are free to rotate. The effects of the ground movements on the pipe are concentrated in the joints.
To repair offset pipe joints, Eckard Brandes Inc. uses a diamond cutter to lengthen the transition of the offset joint. This requires access to the upstream and downstream pipe. Once the offset joint material has been removed, a fiberglass / epoxy partliner is installed to provide a smooth inside surface to the offset joint area.
The fiberglass epoxy partliner is used because of its adhesion to the host pipe, its durability and non-shrinking characteristics. It is 2 to 3 times stronger than the original pipe. Although it decreases the inside diameter of the pipe, it increases flow throughput because of its seamless design.