Development of butt fusion welding equipment and technology for welding dissimilar plastic pipes

Abstract

A plastic pipeline system operating under various environmental conditions (such as corrosion, temperature, and pressure) can be fabricated from dissimilar plastic materials to capitalize on the strengths of each material while reducing costs. The key challenge in welding dissimilar plastics using butt fusion welding lies in individually controlling the heating plate temperature, heat soak time, and fusion joining pressure. However, very few publications explore the use of fusion welding technology for this purpose, and no publication explores how to control the above key welding parameters individually. In this study, we developed a novel butt fusion welding equipment and technology that allows for the independent control of heating plate temperature and heat soak time on both sides of the joint. Then, five case studies were conducted on dissimilar joints between high-density polyethylene (HDPE) and polypropylene random copolymer (PP-R) pipes with the same outer diameter of 110 mm and the same wall thickness of 10 mm. The study evaluated the effects of welding parameters – specifically, heating plate temperature, heat soak time, and fusion joining pressure – on the tensile strength of the welded samples. Our research found that the optimal heating plate temperature for welding is 220 °C for HDPE and 210 °C for PP-R. Furthermore, adjusting the heat soak time within a narrow range (25–35 s for HDPE and 120–130 s for PP-R) resulted in tensile strengths reaching 90 % of the base material HDPE. The maximum tensile strength of 17.5 MPa (about 92 % of the tensile strength of the base material HDPE) was achieved with a heat soak time of 30 s for HDPE and 125 s for PP-R. When the fusion joining pressure was varied between 0.05 MPa and 0.15 MPa, the highest tensile strength (17.5 MPa) was obtained at a pressure of 0.1 MPa (92.1 % of the tensile strength of the base metal HDPE).