Amanda Hawkins, Jason Lawrence, Xiangli Meng
Papers # 2018 Las-Vegas
High Density Polyethylene pipes are used in various applications due to the material’s superior chemical resistance, pressure capability, and ductility. For the material to perform at the optimal design criteria, the connections and fabrications must be fused using repeatable procedures that specify proper fusion temperature, pressure, and process times that allow for the semi-crystalline structures to re-form to achieve appropriate material performance. With the growing acceptance of HDPE into markets dominated by traditional materials like steel, ductile iron, and PVC, improving job site productivity is a key objective to further demonstrating the benefit of using HDPE. Understanding the contribution of different parameters like heat time and ambient temperature is crucial to predicting when the joint has cooled adequately so the machine may move to the next joint. The current industry standards evolved from efforts to harmonize the welding procedures from multiple pipe producers and they are exceptionally conservative given the expectation that the fusion operator is expected to perform a manually controlled fusion process across a wide range of possible job site conditions.. This paper explores the feasibility of accounting for applicable fusion parameters to accurately predict shorter cool times, therefore increasing jobsite productivity. It is recognized that productivity improvements that could impair the mechanical performance of these joints, as measured by failure energy is not acceptable. This work demonstrates that the failure energy of the fusion joints remain constant whether cooled per the existing standard, reducing the fusion cooling time under pressure, nor the different cooling rates caused by changes in ambient temperatures.
