Session: OAC-06-02 Continued Safe Operation of Existing Assets - 2

Paper Number: 101684

101684 - Numerical Investigation for an Optimized Procedure of Overlay Welding Repair for the Metal Loss of Large-Scale Structures 

For pressure equipment in plants that has been in service for an extended period of time, aging degradation, such as corrosion metal loss, has emerged as a prevalent industrial problem, which has increased the demand for repairs recently. In particular, for metal loss degradation, overlay welding repair is often adopted. However, welding inevitably induces deformation and may even cause excessive deformation beyond the allowed dimensional tolerance. Consequently, several concerns have been raised regarding the increasing maintenance costs and failure resulting from the repair process. Herein, numerical studies on the effects of the interpass temperature and welding pass order were conducted to optimize the welding procedure to reduce the deformation of the pressure equipment owing to overlay welding repair. To predict the deformation, a large-scale thermal–elastic–plastic analysis based on the idealized explicit finite element method (IEFEM)  was conducted, wherein the multi-pass overlay welding repair for the external metal loss of a cylindrical pressure vessel made of low carbon steel was simulated. This method accomplished the large-scale computation of 18 or more multi-pass welds within a practical duration that was much shorter compared to that required by the implicit FEM using commercial software. Based on the deformation study with varying interpass temperatures, we clarified that as the interpass temperature decreased, the deformation in the repaired part could be reduced, and the reduction effect peaked when the interpass temperature was less than a certain temperature. In addition, an analysis of various patterns of the welding order also indicated an evident difference in deformation due to the overlay welding order. Based on these results, it is suggested that the deformation resulting from overlay welding repair could be reduced by controlling the interpass time and welding order, and the concept for setting the optimal repair procedure are clarified.

Presenting Author: Junya TAKAHASHI Sumitomo Chemical Co., Ltd.

Presenting Author Biography: Junya Takahashi studied fracture mechanics and welding engineering at Osaka University and received a master's degree in engineering.
Since joining Sumitomo Chemical Japan in 2017, he has been working as a plant engineer to support the solution of problems of plant materials such as damage due to welding or mechanical loads, in addition, working as a researcher to develop material related technologies using numerical analysis and FFS techniques.
And since 2020, he has been working on the optimization and popularization of the Japanese FFS standard as a member of the WES 2820 Revision Sub-committee of the Chemical Plant Welding Research Committee in the Japan Welding Engineering Society.

Authors:

Junya TAKAHASHI Sumitomo Chemical Co., Ltd.
Yuki Yamauchi Graduate School of Engineering, Osaka Metropolitan University
Masakazu Shibahara Graduate School of Engineering, Osaka Metropolitan University