Weld cooling-rates & the onset of failure during "in-service" welding of gas pipelines

Document Type

Conference Proceeding

Publication Date

1-1-2005

Abstract

Welding onto a live-gas pipeline (In-service welding or hot-tapping) is employed in the repair, modification or extension of gas pipelines and has significant economic advantages for the gas-transmission industry since it avoids the costs of disrupting pipeline operation and secures continuity of supply; and used in pipeline maintenance such as the installation of sleeves around damaged sections and direct deposition of weld-metal onto an active pipe to replenish wall thickness lost through corrosion or local damage of the gas pipelines. Unfortunately, the flowing gas results in an accelerated cooling of the weld; and secondly, the localized heating and loss of material strength during the welding process, since the pipe-wall may burst under internal pressure if this reduction in strength becomes too critical. The useful role of numerical simulation of 'in-service' welding has been demonstrated by earlier work (i.e. work of EW1 & BM1, and Goldak & Others-1992) that applied a general 3D-fmite element method to calculate the thermal fields for circumferential fillet and direct-branch welds. Earlier, current authors developed a preliminary burn-through model of 'in-service' welding and in this work the authors have attempted to increase the accuracy of thermal prediction. Copyright 2005 by ASME.

Publication Source (Journal or Book title)

Recent Advances in Solids and Structures 2005

First Page

133

Last Page

139

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