Session: MF-24-01 Materials and Fabrication for Refining-1

Paper Number: 153149

153149 - Weldability and Corrosion Resistance Evaluation of Branch Joint With Branch Outlet Fittings on Process Piping With Heavy Wall Made of Cra Clad Material 

Abstract: 

Where sizes of run pipe and branch are largely different, e.g., large bore run pipe with small bore branch for drain and vent, branch outlet fittings set on run pipes are usually selected to compose branch joints.

CRA (corrosion resistant alloy) solid piping materials are often selected when process fluids are corrosive. To optimize cost of process plant construction, CRA clad or weld overlay on CS (carbon steel) /LAS (low ally steel) parent metal (hereafter CRA clad material) may be applied to process piping. However, manufacturing process of piping materials constrains the minimum diameter of CRA clad piping materials such as NPS 6 (DN 150), therefore, CRA solid materials are applied to lesser diameters than the minimum.

CRA clad materials also constrain the minimum size of fabricated branch design because branch holes on CRA clad piping material must be also protected by CRA weld overlay against direct exposure of corrosive process fluids. And accessibility of welding torch/arc and visibility of molten pool during weld overlay work on small bore holes must be considered from viewpoints of weldability and weld overlay quality. Where wall thickness of CRA clad piping material is thick such as 50 mm (2 inch), the minimum diameter of branch such as NPS 1 (DN 25) should be enlarged to NPS 4 (DN 100) for example due to the accessibility and the visibility. If the branch design with small diameter on heavy wall run pipe of CRA clad piping is for drain, piping layout may be affected because enlarged hole from original design on run piping materials requires insert of additional reducer(s) between the branch outlet fitting and drain piping materials to match with drain piping size.

To make up for these shortcomings, other protection method for holes on CRA clad run piping materials, such as insert sleeve made of CRA materials welded with groove joint on the holes, were introduced. And the mockup coupons of the sleeve design branch and conventional CRA weld overlay design were prepared with branch outlet fitting, and weldability and corrosion resistance were studied by the comparison using both mockup coupons. In addition, materials selection for the branch joint with branch outlet fitting on CRA clad piping materials were studied considering PWHT (postweld heat treatment) or as weld condition.

This report discusses and evaluates the weldability, corrosion resistance and materials selection of both branch designs and potentials that can eliminate the piping design constrains with their comparison.

Presenting Author: Atsushi Takahashi JGC CORPORATION

Presenting Author Biography: Atsushi Takahashi has been working for JGC CORPORATION since 2006 and assigned as Chief Engineer Welding since 2019, and been in charge of developing welding requirements for EPC project, welding and casting related trouble shooting, providing educational programs of welding engineering and welding activity at fabrication shop and construction site, and carrying out welding related R&D programs.
He is a deputy chairman of Chemical Plant Welding Research Committee in Japanese Welding Engineering Society since 2022.

Authors:

Atsushi Takahashi JGC CORPORATION
Masahiro Kawai JGC CORPORATION