A Quantitative Index to Assess the Influence of Joint Fit-Up on Pipeline Weld Root Discontinuities

2020 ◽  
Author(s):  
M. R. Grams ◽  
L. Ludwig ◽  
P. F. Mendez
Keyword(s):  
Pipe Wall ◽  
Latent Root ◽  
Angular Distortion ◽  
Quantitative Index ◽  
Objective Criterion ◽  
Joint Geometry ◽  
Weld Root ◽  
Low Offset ◽  
Welding Procedure ◽  
Numerical Index

Abstract Field experience on pipelines suggests that under the unique conditions of tie-in welding, a high-low offset at the inner pipe wall is related to an increased occurrence of latent root weld discontinuities such as cold cracking. Codes and standards offer conflicting and unclear guidelines regarding acceptance criteria for high-low offset. This study presents a numerical index to quantify the influence of non-ideal joint geometry on the latent discontinuity susceptibility of the root pass for circumferential pipeline welds. The index is based on the stress concentration at the root and the angular distortion associated with plastic strains produced during welding. This index relates geometric considerations such as pipe diameter, wall thickness, and the cross section of the root pass with welding procedure variables and the mechanical properties of the pipeline material. Although this study is meant for steel pipelines, the conclusions obtained are also applicable to other materials. The index presented is a contribution towards an objective criterion for acceptance of high-low offset during field welding, ranking the susceptibility to latent discontinuities as a function of variables available to practitioners during field welding.

On the Mechanics of Residual Stresses in Girth Welds

2006 ◽  
Vol 129 (3) ◽  
pp. 345-354 ◽  
Author(s):  
P. Dong
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Relative Importance ◽  
Stress Distributions ◽  
Unified Framework ◽  
Joint Geometry ◽  
Weld Residual Stress ◽  
Girth Welds ◽  
Welding Procedure

In this paper, some of the important controlling parameters governing weld residual stress distributions are presented for girth welds in pipe and vessel components, based on a large number of residual stress solutions available to date. The focus is placed upon the understanding of some of the overall characteristics in through-wall residual stress distributions and their generalization for vessel and pipe girth welds. In doing so, a unified framework for prescribing residual stress distributions is outlined for fitness-for-service assessment of vessel and pipe girth welds. The effects of various joint geometry and welding procedure parameters on through thickness residual stress distributions are also demonstrated in the order of their relative importance.

On the Mechanics of Residual Stresses in Girth Welds

2004 ◽  
Author(s):  
P. Dong
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Relative Importance ◽  
Stress Distributions ◽  
Unified Framework ◽  
Joint Geometry ◽  
Weld Residual Stress ◽  
Girth Welds ◽  
Welding Procedure

In this paper, some of the important controlling parameters in governing weld residual stress distributions are presented for girth welds in pipe and vessel components, based on a large number of residual stress solutions available to date. The focus is placed upon the understanding of some of the overall characteristics in through-wall residual stress distributions and their generalization for vessel and pipe girth welds. In doing so, a unified framework for prescribing residual stress distributions is then outlined for fitness-for-service assessment of vessel and pipe girth welds. The effects of various joint geometry and welding procedure parameters on through thickness residual stress distributions are also demonstrated in the order of their relative importance.

Proper Design and Fabrication of Socket Welds for Use in Sour Service

2010 ◽  
Vol 638-642 ◽  
pp. 3649-3654
Author(s):  
Robert D. Caligiuri ◽  
Lawrence E. Eiselstein ◽  
L.N. Eastep
Keyword(s):  
Chemical Species ◽  
Gas Tungsten Arc ◽  
Piping Systems ◽  
Proper Design ◽  
Stress Environment ◽  
Process Fluid ◽  
Weld Root ◽  
The Right ◽  
Welding Procedure ◽  
Sour Service

Socket welds are commonly used to assemble small-bore carbon steel process piping systems because they can be fabricated fairly quickly and are somewhat tolerant of field fit-up issues. In the most simplistic terms, these welds are made by inserting the pipe into a socket and then seal welding using gas tungsten arc welding around the gap between the outside pipe wall and the end of the fitting. This leaves a notch in the root of the seal weld that is open to the process fluid. This notch can act both as a stress riser and a crevice capable of concentrating chemical species. In many process applications, these socket weld notches do not cause any in-service problems. However, in the case of sour service, these notches can become problematic because of the potential for sulphide stress corrosion cracking (SSCC). For SSCC to occur, the right combination of stress, environment, and material susceptibility must be present. Therefore, for socket welds to be used in sour service without the risk of failure, these parameters need to be controlled by proper design and fabrication of the welded joint. Since a crevice is created as a natural by-product of a socket weld geometry, where the SSCC environment will be present, the parameter most readily controlled to minimize susceptibility to SSCC is the microstructure and residual stress of the weld filler metal. As will be shown, this resistance to SSCC can be accomplished by designing a welding procedure specification to include the combination of both a second pass seal weld and by post-weld heat treatment (PWHT). It will also be shown that a complete second pass is crucial to proper tempering and refining the microstructure of the root pass. Without this microstructural tempering and refining by the second pass, the root pass can still undergo SSCC even with subsequent application of PWHT. Examples of SSCC initiating from crack-like weld root defects caused by poor welding techniques and propagating into single-pass socket welds that had been subjected to PWHT will be presented.

scholarly journals Electron Beam Welding of Gear Wheels by Splitted Beam

2014 ◽  
Vol 22 (34) ◽  
pp. 35-41
Author(s):  
Daniel Dřímal
Keyword(s):  
Electron Beam ◽  
Critical Point ◽  
Electron Beam Welding ◽  
High Strength ◽  
Optical Measurements ◽  
Welding Parameters ◽  
Case Hardening ◽  
Weld Root ◽  
Gear Wheels ◽  
Welding Procedure

Abstract This contribution deals with the issue of electron beam welding of high-accurate gear wheels composed of a spur gearing and fluted shaft joined with a face weld for automotive industry. Both parts made of the high-strength low-alloy steel are welded in the condition after final machining and heat treatment, performed by case hardening, whereas it is required that the run-out in the critical point of weldment after welding, i. e. after the final operation, would be 0.04 mm max.. In case of common welding procedure, cracks were formed in the weld, initiated by spiking in the weld root. Crack formation was prevented by the use of an interlocking joint with a rounded recess and suitable welding parameters, eliminating crack initiation by spiking in the weld root. Minimisation of the welding distortions was achieved by the application of tack welding with simultaneous splitting of one beam into two parts in the opposite sections of circumferential face weld attained on the principle of a new system of controlled deflection with digital scanning of the beam. This welding procedure assured that the weldment temperature after welding would not be higher than 400 °C. Thus, this procedure allowed achieving the final run-outs in the critical point of gearwheels within the maximum range up to 0.04 mm, which is acceptable for the given application. Accurate optical measurements did not reveal any changes in the teeth dimensions.

Numerical simulation and experimental validation of angular distortion and residual stresses in a T-joint

2015 ◽  
Vol 57 (7-8) ◽  
pp. 628-634
Author(s):  
Jing Chen ◽  
Liying Wang ◽  
Zhendong Shi ◽  
Zhen Dai ◽  
Meiqing Guo
Keyword(s):  
Numerical Simulation ◽  
Residual Stresses ◽  
Experimental Validation ◽  
Angular Distortion
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