Vertical pipe column assembly method

Abstract

A vertical pipe column assembly procedure involves the simultaneous welding and ultrasonic testing activity by using a plurality of welders progressing peripherally around a joint with the ultrasonic testing work similarly progressing peripherally around the joint between the welders. The temperature rise from welding activity is reduced by only partially completing the weld at a selected joint, then lowering the joint by the usual process of lowering or driving it downward one section length and completing the weld deposit at a lower work station. At the lower work station, ultrasonic testing again proceeds simultaneously between the peripherally progressing welders. An optional step used to improve joint strength, usable at selected joints needing the most strength, involves the application of an axial pull on the section above the finish welding activity. This axial pull places an axial stress in the partially completed weld. When the finishing weld metal cools it shrinks and is itself axially tension stressed. When the last weld metal applied cools, the axial pull on the pipe column is removed and the axially stressed weld is in a lower stressed state. By this external stress application process the outer weld metal places less compressive stress on the inner weld metal with a consequent reduction in the intrinsic stresses induced by the welding process. A stronger joint is the final product.