Effect of Weld Parameters and Stacked Errors on the Quality of PE Welds

Following the 2011 Christchurch earthquake the use of welded polyethylene (PE) pressure pipelines for water supply networks and for pressure sewer mains continues to increase. 

To achieve the design lives required from these pipelines the welded joints must be fully fused and be ductile. Despite the increasing use of this pipeline material the incidence of brittle welds with varying degrees of fusion is still causing concern.

This paper reviews options that Designers and Contract Supervisors can employ to improve the quality of PE welding in construction.

These options include:

• guidelines for acceptance of pipe and materials offered at time of tender
• the development of useful pre-construction welding trials to reduce the downstream construction risks to the Contractor, the Principal, and the Materials Supplier.
• selection of welding parameters, including comparison of some of the welding parameters available to the industry and likely to be submitted at time of tender.
• consideration of the effect of stacked errors during the welding process and the control of these.

These options are based on lessons learned from investigations of welding failures and theoretical considerations of welding parameters offered by the industry.