EFFECT OF WELDING ON A HIGH-DENSITY POLYETHYLENE LINER

This paper describes part of an ongoing research project concerning hi gh-density polyethylene (HDPE) liners used for pipeline rehabilitation . Tests were conducted in the laboratory, where a steel sleeve was wel ded on the outside surface of a steel pipe lined with a HDPE liner. Re commendations were made to establish welded joints using stitch welds of length equal to the minimum length specified by the applicable code s, with a center-to-center spacing of three times the weld length. A w aiting period may be required between consecutive stitch welds, especi ally for small-diameter pipes. A second group of tests was conducted t o evaluate the material performance of a liner strengthened by butt-fu sed HDPE rings. The overall stiffness of the liner increased with the addition of the butt-fused rings. Tension tests were conducted on dog- bone-shaped samples extruded from the stiffened liner. The butt-fusion process used to attach the stiffening rings increased the average ten sile strength and average elasticity modulus of the material in the fu sion area.