Evaluation of Friction Stir Welding Process on Defective Polyethylene Pipes: Experimental Study

Abstract

Polyethylene (PE) pipes are lightweight and easy to handle but are also prone to cracks and defects. Improper use of equipment can cause subsequent damage, resulting in costly repairs. To avoid this, it is essential to take appropriate precautions to prevent damage to the pipes, especially during their installation and assembly. Therefore, it is important to know how to avoid and correct these defects, such as welding them. If the damage exceeds 11% of the pipe thickness, it may cause a hazard that worsens over time in service, requiring costly renovation or replacement. Engineers need research assistance to find ways to weld defective PE pipes. Accurate prediction of the service life of the pipes and consideration of all factors are essential. Therefore, it is wise to choose the friction stir welding (FSW) process, which is often used in technical applications, to check whether the behavior of the studied pipe can be extrapolated after welding the defect. This original study aimed to develop a new methodology to address defects in water, gas, and oil transmission and distribution lines before assembly and in-service. Longitudinal artificial defects were created in 125 mm diameter high-density PE natural gas distribution pipelines. These defects were then welded using the FSW process, and their strength was evaluated using naval ordnance laboratory ring. Tensile tests were performed on samples extracted from the welded sections of the pipelines. The experimental work aimed to know the effect of FSW process on the mechanical properties of artificially defective pipes to develop the method approach and apply it in the desired maintenance.