Cristian Hedesiu, Roger Jepson, Mohamed Hageb, Mohana Murali
Papers # 2012 Barcelona
It was found that welding high modulus polypropylene (PP-HM) material in accordance with the parameters of DVS 2207-11 did not produce welds which met the requirements of the Guide. The optimum welding conditions for butt fusion welding of large diameter pipes e.g. 2000 mm and 3000mm, made from PP-HM were investigated on the basis of tensile, bending tests and visual inspection results as per DVS 2203-1, DVS 2203-2, DVS 2203-5 and DVS 2207-11 guides. The initial welding trials were undertaken by using various weld temperatures, pressures and heating-up times following DVS guideline and within 10% of the DVS quoted parameters to assess the effect of these changes and confirm the optimum weld parameters. No significant improvement in welding factor was observed in trials and the requirements of the DVS Technical Guides for the tensile and bend tests did not meet the specifications. Further welding trials were undertaken using a dual pressure method and longer joining times following UK’s WIS-32-08 :1994 methodology. Although, this standard was developed for Polyethylene (PE) pipes and not Polypropylene (PP) pipes the results of welding tests following this method indicate an average strength of around 25N/mm2 for the optimum welding parameters and a weld factor of 0.92.The obtained weld factor meets the DVS requirements and well exceeds the proposed Inspection and Test Plan (ITP) acceptance of 15N/mm2 derived from design considerations.