Polyethylene Pipeline Systems - Avoiding the Pitfalls of Fusion Welding

Proceedings Publication Date:

05 Sep 2016
Presenter
Dr. Chris O'Connor
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Author
Chris O'Connor
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Abstract
Polyethylene (PE) has revolutionized low pressure pipe system design on a global basis and is testimony to PE’s unique combination of properties, which have driven the replacement of traditional pipe engineering materials during the last 50 years. PE pipes and fittings are used extensively in operating gas and water distribution systems safely, reliably and economically, and enjoy an excellent performance track record. PE offers the pipe industry:
  • Economical, high volume manufacture – extrusion, injection moulding;
  • Design flexibility – easily shaped;
  • Integrated design – multifunction, ready assembled components – couplers and fittings;
  • Low material cost;
  • Light-weight design – ease of transport and handling;
  • Flexibility – ease of transport and handling, use in conjunction with trenchless technologies and resistance to seismic activity;
  • Relative ease of jointing (compared to metallic pipe systems);
  • Corrosion and chemical resistance;
  • Biologically inert capabilities;
  • Toughness, impact resistance, abrasion resistance and long term durability – technical lifetime of >50 years;
  • Low temperature performance;
  • Leak-free fusion jointing - low maintenance costs;
  • Low friction bore - no scale build-up and efficient flow of transfer medium; and
  • Environmental benefits - recyclable
The success of PE for pipeline applications has been achieved through a long legacy of historical development, catering for pipe industry requirements. Over the past 50 years, PE materials have evolved and now provide a good balance of strength, stiffness, toughness and durability consistent with demands of long-term gas and water pressures, ground loading and the service environment. Key to the success of PE pipeline system is the ability to form end load resistant fusion joints with strength equivalent to the parent pipe materials with a minimum design life of 50 years. However, there is an ever increasing awareness that the technology and reliability is being undermined by operative workmanship in the field, posing a risk to the pipe network. This is a particular concern for gas distribution where premature failure can have catastrophic effects resulting in loss of life. In order to reduce the risk to networks there is a need for increased increased requirements for training and qualification of installers, including tooling requirements and servicing of tooling. The aim this presentation is to provide an overview of key parmeters which influcence fusion weld performance, typical failure modes seen in the field and preventative actions which can help mitigate the incidence of failure.

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