HIGH THICKNESS AND LARGE DIAMETER PIPES MANUFACTURING WITH... #2021

In the Middle East and India, PE pipes have expanded their applications in a big way for water supply, industrial effluents, corrosive chemical transportation, slurry transportation, city gas distribution networks and agriculture irrigation purposes over ductile iron, cast iron and other conventional pipes. PE pipes have become the most preferred material of construction for sea intake/outfall and industrial use against competing materials like steel, rubber lined metal and GRP/FRP pipes. The successful use of PE pipes especially for industrial applications like intake and outfall lines for desalination, thermal power, industrial chemicals / effluent increases demand for large diameter and thick-walled pressure pipes. Tailor made solutions are required for industrial applications like high-pressure pipelines requiring extra high wall thickness.

PE pipes manufacturing has progressed in these regions from diameters over 630mm in the 1980s and 1990s to recent diameters of 2000-2500mm. Simultaneously, there is also increased consideration of higher temperature, pressure and safety factors as well as requirements for pipes < SDR 11. Production of large diameter and thick-walled pipes is still considered the biggest challenge in the industry. Achievement of uniform wall thickness distribution, optimisation of production losses, jointing of non-uniform wall thickness in field are also big concerns. Ease of production of large diameter pipes from very high molecular weight PE in many cases is an unmet need. This requirement can be met by PE100 material characterized with even better low sag properties (achieved through higher viscosity) and support from machinery development.

Novel extra low sag pre-compounded material produced using bi-modal technology has been tried successfully for 2500mm OD x 105mm wall thickness as well as for 1600mm x SDR 17 thick wall pipe production. The results of commercial production of several kilometres of 2000mm x SDR 27 pipes produced easily with uniform distribution will be showcased. This paper will describe the challenges of developing extra low sag PE100 material. The methodology for describing characteristics of raw material will be discussed. The advantage of extra low sag material compared to standard PE100 material for production cost optimisation in large diameter and thick-walled pressure pipes will also be showcased, through case studies. Efforts taken in including extra low sag material along with inclusion of large diameter pipes in Indian Standards IS: 4884-2016 for polyethylene pipes will be highlighted.