Welding techniques for pipe jointing include butt welding and electrofusion welding for Polyolefin (PO) pipes. For certain applications like directional drilling and slip lining, PVC butt welding is also recommended. For applications such as slip-lining, where tensile resistance of the joints is a must, welded joints are required.
Tensile resistant end-joints are necessary for long pipe sections due to pipe shortening caused by the Poisson effect under pressure. The reliability of these standard jointing techniques influences market acceptance. Welded PVC joints are used in situations where tensile strength is important, but there is no specific data provided on the mechanical strength values of butt-welded or electrofusion PVC joints. It notes that PE materials perform well in crack propagation tests, resulting in a low safety factor (as low as 1.25 for water pipes), whereas UPVC has a safety factor of 2-2.5. Biaxial oriented PVC (PVCO) has layers acting as crack stoppers and a lower safety factor of 1.6. However, this information pertains to the pipe material's strength, not specifically the mechanical strength of the weld itself.