There are essentially only two possible choices for joining coiled tubing (CT), namely by welding and mechanical spoolable connectors. Both methods have certain advantages and disadvantages. Except for remote and/or some offshore locations, welding is a more readily available method requiring less pre-planning since some mechanical connectors must be precision machined to suit a specific CT diameter, wall thickness and strength grade in order to obtain maximum plastic bend fatigue performance. Also, a welded joint in CT can readily maintain an external and, with orbital welding processes, internally flush surface.

On the down side, obtaining a high quality CT connection through welding requires specialized skills and welders or welding operators who are qualified for welding tubular goods from one side without backing. A welder qualified in pressure vessel welding is preferred. Tungsten inert gas welding (TIG) is the usual welding process employed for butt or girth joints in CT. A fit up and joint alignment jig such as that shown in Figure 1.

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