Study of how welding methods impact the stress build-up in storage tank walls

THE ARTICLE EXAMINES THE topical issues of vertical tank wall repair by means of welding insert plates into a temporary opening. Currently, welding of insert plates is hardly covered in public sources. Structural elements of steel tanks are subject to wear. Most repairs involve clearing of corrosion damages and distortions of geometric shape of walls, which require repair work. Cumulative operating history of steel tanks designed for crude oil and oil products storage indicates that a more detailed study is necessary to explore engineering problems relating to repair works and development of new repair technologies. One of the main issues encountered when manufacturing and repairing tanks are welding deformations, which reduce the strength and stiffness of metal structures, distort the size and shape of structures, and cause an overall reduction in the quality of repair works. The need to eliminate or partially reduce deformations increases the labour input required to manufacture the structure. The most promising way of improving the quality of repair work using the insert plate method is by choosing the optimal thermal welding cycle (TWC) modes, and selecting methods of TWC parameters control depending on the geometric dimensions of the insert plate and on the welding method. Based on analysis of the results of experimental studies, this article describes the ways to limit the impact of residual welding stresses and deformations on the geometric parameters of vertical steel tank walls during repair work by using insert plates. The analysis covers the impact of various technological factors on the parameters of the heat-induced distortion in the welding cycle. Computer modelling is proposed as a method to monitor the level of residual welding stresses and deformations. The main conclusion of this research is the need for the development and use of computer technology to monitor the level of stresses and deformations which arise during the welding process. The scientific research results presented here are aimed at addressing the issue of improving vertical tank reliability after repair works