Pipeline Welding Research Articles

Research status of seam tracking methods for orbital pipe welding robots

This paper first outlines the worldwide oil and gas pipeline laying situation by 2013 and industrial applications,the working characteristics and advantages of orbital pipe welding robots using the gas metal arc metal( GMAW). Then the classifications of commonly used welding seam tracking sensors are comprehensively introduced. The sensor working principles,advantages and disadvantages and the application situation in pipeline welding are analysed in details. The studies show that arc sensors and visual sensors have many advantages such as good real-time characteristic,informativeness and high tracking precision,and are most widely used in pipeline welding. Using single sensor in different process can limit the tracking precision easily,but a system with multiple sensors will greatly improve the tracking precision in oil and gas pipeline welding. A system using visual sensor and arc sensor has been used in the gas field pipeline welding in Japan and a good effect has been achieved. Finally the conclusion is drawn that suitable seam tracking sen-sor should be chosen according to the process features and methods,and using a variety of sensors can improve the welding seam tracking precision,which will become the focus of future researches.

Investigation and development of the technology for automatic welding of pipes of P91 (X10CrMoVNb9-1) steel

The parameters of the technology of automatic argon-shielded arc welding of pipelines of P91 steel using Thermanit MTS3 filler wire are presented. The technology produces welded joints with the required mechanical properties and service characteristics.

Productivity Monitoring of Land Pipelines Welding via Control Chart Using the Monte Carlo Simulation

This article evaluates the efficacy of a tool developed in the Monte Carlo simulation and referred to as control chart. This tool is used in order to detect changes in productivity resulting from the occurrence of a given event during the welding of land pipelines with self shielded flux cored wire (FCAW). The elaboration of this control chart is based on the data from the Cumulative Probability Density Function (CDF) curve, and generated in the Monte Carlo simulation using version 6 of the Palisade Corporation’s @Risk software for Excel, in a sample with productivity data from 29 welded joints, gathered through direct observation which considers the productive and unproductive times. In order to evaluate the control chart efficacy, the performance of welding productivity with a FCAW process with low alloy steels has been assessed during 29 days, summing up to 842 welded joints registered on “Relatorios Diarios de Obras” (Construction Works Daily Reports). The results show that the model developed for the control chart elaboration is effective in monitoring the productivity of the observed welding procedure.

Nondestructive Testing Residual Stress Using Ultrasonic Critical Refracted Longitudinal Wave

Residual stress has significant impacts on the performance of the mechanical components, especially on its strength, fatigue life and corrosion resistance and dimensional stability. Based on theory of acoustoelasticity, the testing principle of ultrasonic LCR wave method is analyzed. The testing system of residual stress is build. The method of calibration of stress coefficient is proposed in order to improve the detection precision. At last, through experiments and applications on residual stress testing of oil pipeline weld joint, vehicle's torsion shaft, glass and ceramics, gear tooth root, and so on, the result show that it deserved to be studied deeply on application and popularization of ultrasonic LCR wave method.

Technology Update: New 3D Ultrasonic System Tests Pipeline Integrity

Technology Update The global oil and gas industry’s vast infrastructure includes many pipelines that were manufactured decades ago, and the intensive quality control processes in place have generally ensured that they have stood the test of time. As the technologies adopted by the industry to optimize drilling campaigns have evolved, the equipment used in the pipeline testing process has improved as well. Nondestructive testing (NDT) is used across the industry to inspect pipelines for defects that are impossible to discover with the human eye. NDT covers a wide range of methods, such as radiography and ultrasonic testing, by which pipelines can be inspected without altering their physical properties. This allows for highly productive testing, saving time and money as well as providing valuable evaluation, troubleshooting, and research. Ultrasonic Inspection Ultrasonic testing makes use of sound energy to examine specific components of a pipeline, such as girth welds, thus allowing for flaw detection and sizing. The testing process is principally used to examine welds in pipelines before they are accepted for use and is vital in ensuring that the pipelines can withstand the kinds of pressures they will be subjected to in an industrial setting. Any defects in the weld could have devastating consequences for safety and the environment. Ultrasonic inspection using the pulse echo (PE) technique or time of flight diffraction (ToFD) is widely used throughout the industry to assess weld integrity. However, quantitative defect characterization with PE remains challenging because the signal caused by the reflection at a point of defect is highly dependent on the defect’s orientation in relation to the ultrasonic beam. ToFD has sizing capabilities, when diffraction signals are present, but is limited in its ability to characterize flaws. In phased-array inspection, the image obtained from sectorial scans cannot be directly related to the defect’s size and orientation. Data display and interpretation are not straightforward and require operator skills and experience. Ultrasonic inspection would be better and more reliable if a method would allow direct imaging of defects. 3D Ultrasonic Imaging A recent significant advance in the field of NDT developed by Applus RTD is a 3D ultrasonic technology that uses inverse wave field extrapolation (IWEX) to enable detailed inspection and mapping of defects within critical pieces of pipework. The technology extrapolates wave field recordings back into space toward all points in the area under investigation. If at one of those points a scatterer (e.g., a defect) is present, the backward-extrapolated wave field has high amplitude, and the resulting image will show increased intensity at that location. If this is done for all points in the image, the location and shape of the scatterer can be determined.

Fracture Research on Preheating Installation of Directly Buried Heating Return Water Pipe with Large Diameter

Pipe fracture and compensator tear may happen when directly buried pipes with large diameter, high temperature and pressure adopt preheated installation. Combined with engineering, this paper analyzes theoretically the fracture accident on DN1200 return water pipe during the period of cold operation and analyzes various factors which cause the pipeline fracture, when adopt open ditch electric preheating. By the numerical simulation, the size of influence factors on fracture was obtained, and the conclusion that the tensile stress is greater than the compressive stress was also obtained, where the preheating temperature was defined by means of “intercycle temperature”. It is worth nothing, the buried pipeline will emerge vertical bending under the main impact of soil and transportation loads. The vertical bending is related to pipe base, and the value of curving stress will be very big if the pipe base is mishandled. The coupling effect of curving stress and the temperature tensile stress can lead the pipeline to fracture, such as the disposable compensator place, the pipeline welding place, corners, the pipe wall flaw place and so on. This paper proposed the effective preventive measure which may reduce the occurrence probability of pipeline fracture during temperature drop process.

Ultrasonic Testing Numerical Simulation of Austenitic Stainless Steel Pipeline Welding Cladding

In the paper, ultrasonic testing of austenitic stainless steel pipeline welding cladding is stimulated based on ultrasonic testing software CIVA. The result shows that the frequency is higher; the sensitivity on small defect testing is higher. When cylindrical defect with length of 6mm and diameter of 2mm is detected, the frequency is higher, the tested length-section result is more accurate, and the width-section (i.e., diameter) is not affected. The optimum frequency scope for testing the defect should be between 5MHz and 10MHz.

Ultrasonic Beam Simulation of Austenitic Stainless Steel Pipeline Welding Cladding

Austenitic stainless steel shows clear acoustic anisotropy. How to detect and evaluate the material becomes research difficulty and popular problem in acoustic detection field. In the paper, Civa software is applied for simulating ultrasonic wave propagation in austenitic stainless steel cladding layer. The influence of included angle between acoustic wave propagation direction and crystal axis on acoustic wave propagation is studied. The study results show that: the focusing property is good when the included angle is 30°-45°, which is beneficial for ultrasonic testing of cladding layer. When the included angle is greater than 70° or so, actual propagation path of acoustic wave and propagation direction of acoustic wave have certain deviation angle with poor acoustic wave focusing property and rapid acoustic attenuation speed, which is not conducive to acoustic detection of cladding layer.

Research on Influencing Factors of Welding Residual Stress of Welded Pipes

Analyzing the pipeline sheet of X70 level, the work also establishes three-dimensional element model of pipeline welding with ANSYS (software of large general purpose with finite element analysis). After comparing different plans, changes of outer diameter and wall thickness are found influencing distributing laws of welding residual stress of welded pipes. Thus, the laws are concluded.

Galvanic corrosion of electric resistance welded X52 steel in CO2-containing solution

Purpose – This paper aims to report an experimental investigation of the galvanic corrosion that occurs between the base metal and the welds in X52 carbon steel petroleum pipelines when exposed in carbon dioxide (CO2)-containing saltwater at pH 4 at room temperature. The pipeline was fabricated by electric resistance welding (ERW). Design/methodology/approach – The experimental setup was a closed glass cell equipped with a silver/silver chloride (Ag/AgCl) reference electrode, two working electrodes (the weld metal and the parent steel specimens) and a gas bubbler. The corrosion potential and polarization resistance of the base metal and the weld were determined using electrochemical testing methods: potentiodynamic polarization scans and linear polarization resistance measurement. The galvanic currents of the base metal when coupled to the weld metal were measured using zero resistance ammetry. Findings – The weld metal was the anode of the couple for a very short time at the beginning of the experiment and then became the cathode until the end of the experiment. This indicates that electric resistance welded X52 steel pipe is a promising material to be operated in CO2-containing saltwater at pH 4 and 25°C because the weld area is cathodic to the parent metal, the value of the galvanic current is very low (in the order of nanoamps) and the area of the anode (i.e. the parent metal) is significantly larger than that of the cathode (weld metal). Research limitations/implications – Further experimental research could be performed to investigate the galvanic corrosion behavior between the parent metal and the weld area of X52 carbon steel petroleum pipelines in CO2-containing saltwater at different pH values, temperature and velocity. Practical implications – Electric resistance welded X52 steel pipe is a promising material for use with CO2-containing saltwater environments at pH 4 and 25°C. Originality/value – The new information presented in the paper is the galvanic corrosion behavior between the parent metal and the ERW weld metal of X52 carbon steel in CO2-containing solutions. The paper should be useful to researchers working in the field of oil industry corrosion.

Investigating the Significance of Bicarbonate with the Corrosion of High-Strength Steel in CO2-Saturated Solutions

This paper presents an electrochemical study on the corrosion behavior of API-X100 steel, heat-treated to have microstructures similar to those of the heat-affected zones (HAZs) of pipeline welding, in bicarbonateCO2 saturated solutions. The corrosion reactions, onto the surface and through the passive films, are simulated by cyclic voltammetry. The interrelation between bicarbonate concentration and CO2 hydration is analyzed during the filming process at the open-circuit potentials. In dilute bicarbonate solutions, H2CO3 drives more dominantly the cathodic reduction and the passive films form slowly. In the concentrated solutions, bicarbonate catalyzes both the anodic and cathodic reactions, only initially, after which it drives a fast-forming thick passivation that inhibits the underlying dissolution and impedes the cathodic reduction. The significance of the substrate is as critical as that of passivation in controlling the course of the corrosion reactions in the dilute solutions. For fast-cooled (heat treatment) HAZs, its metallurgical significance becomes more comparable to that of slower-cooled HAZs as the bicarbonate concentration is higher.

An Improved Weld Seam Extraction Method Using Saliency Detection for Pipe-Line Welding Based on GMAW and Passive Light

To meet the need of the automation and intelligence of welding process, it’s very important to extract the edge of weld seam accurately for seam tracking. According to the characteristics of GMAW (gas metal arc welding), an image sensing system of weld pool region based on CCD (Charge-coupled Device) is established. An improved method of weld seam extraction is presented. Firstly, weld pool region localization method using saliency detection is proposed, and weld seam region is obtained from the right edge of weld pool, then Sobel transformation and computation model is used to extract the edge of weld seam. Experimental results show that our method can obtain a more accurate weld seam edge and cost less than other method.

Dynamic Response of Free-Span Sub-Sea Pipelines under Vortex Induced Vibrations

Study of dynamic behavior of pipeline is required to access fatigue life of pipeline welds. Semi-empirical mathematical model is thus proposed to calculate responses of free-span pipelines under vortex induced vibrations. A two equation model interacted through velocity coupling with a non-linear stiffness term for pipeline model and a non-linear damping term for wake is considered. The proposed model is found to represent the real situation of responses to a greater extent.

Research of Pipeline Weld Detection Based on Magnetic Memory Technology

Ensuring the safe operation of pipeline and monitoring it to prevent sudden accidents are an important task of current nondestructive testing work because of our country is in the peak period of long-distance pipeline construction. Welding cracks are common and most dangerous flaw in the root of the failure of the welded joints . Metal magnetic memory method is the only viable detection , evaluation method currently used for diagnosing the stress-strain state of serving welding crack in the early stages. So this article designs weld cracks of the general pipeline, establish a method to detect pipeline weld crack by metal magnetic memory method.

Welding Stress Numerical Simulation and Analysis of High-Pressure Pipeline

Welded stress has an important impact on quality and life of of high-pressure pipeline. Based on pipeline material performance, considered welding arc force and its mining action, selected double ellipsoidal heat source model, simulated welding process of of high-pressure pipeline, analysised welding temperature field and stress field, determined the distribution disciplines of welding stress, provides useful help on exploring the disciplines of pipeline welding.

A comprehensive study on the microstructure of high strength low alloy pipeline welds

The microstructural characteristic of HSLA welds containing different amounts of titanium were evaluated carefully. It was observed that the microstructure of welds consisted of ferrite with mixed morphologies, and small amounts of pearlite and martensite–austenite micro-constituents. Because of insufficient time for diffusion of carbon, formation of pearlite lamellae could not be completed in the weld region. Martensite was formed from carbon enrichment of austenite during nucleation and growth of acicular ferrite and bainitic ferrite. While coarse manganese sulfide particles had weak interface strength with matrix and formed some micro-fissures; increasing titanium amount of welds dispersed different modified morphologies of inclusions in the microstructure. Several types of precipitates including spherical, cubical, fine and irregular titanium carbonitride were found in the microstructure and they were favorite sites for nucleation of acicular ferrite. The size of cubical/spherical and fine precipitates was measured between 70–100 and 10–20nm, respectively. Low energy interface of inclusion/matrix and the depletion of carbon in austenite were proposed as the nucleation mechanisms of acicular ferrite from nano-sized inclusions.

Demagnetisation of gas pipeline during welding and safety measures and reliable of welded pipe construction in exploatation

When welding some alloye steels with high nickel and carbon steel greater thickness may occur magnetic fields on working piece. Magnetism causes problems and difficulties in establishing the arc, leading to elimination of blowing port on desired direction, does not melt uniformly edges of groove and cause lack of fusion, non penetrating roots errors or even completely prevents welding. Due to the comlexity of problems of construction and welding of pipelines and the importance of safety and reliabilty of the entiry pipeline is prescribed welding technology that will provide the best features of welded joints. Preliminary tests were made of welded samples for welding procedure qualification. The paper presents a welding gas ipeline with a high concentration of magnetic lines of force. Base material is carbon steel resistant to low temperatures A333 Gr.6 which dimensios are φ 406,4 x 12,7 mm and (API) 5L X Gr. 52, φ 406,4 x 6,35 mm. Demagnetisation pipeline was determined by winding the cable around the workpiece (pipes). After demagnetisation and provides arc welding was done on schedule and welding parameters given in technological lists. Since gas pipelines carry a high risk to the safety in operation, leaking gas can cause sudden explosion and fire, so that the welds tested radiographic method, and the regulation require.

A Smart System to Determine and Control for the Process Parameters in Pipeline Welding

Determination of the optimal welding parameters to achieve specific weldments on a new material is usually an expensive and time consuming. To determine the welding parameters using Artificial Intelligence (AI) technologies, one must consider many factors including productivity, thermal input, defect formation, and process robustness. Determination of the welding parameters for pipeline welding is based on a skilled welders long-term experience rather than on a theoretical and analytical technique. In this paper, a smart system develops which determines welding parameters and position for each weld pass in pipeline welding based on one database and FEM model, two BP neural network models and a C-NN model. The preliminary test of the system has indicated that the system could determine the welding parameters for pipeline welding quickly, from which good weldments can be produced without experienced welding personnel. Experiments using the predicted welding parameters from the developed system proved the feasibility of interface standards and intelligent control technology to increase productivity, improve quality, and reduce the cost of system integration.

Analyses and application of the magnetic field at girth welds in pipelines

This paper proposes a novel method of utilizing weld identification to improve the positioning accuracy of an in-pipe detector in pipelines. The distributions of the magnetic field inside a single pipe are analysed using the equivalent magnetic charge method. Then the causes and characteristics of abnormal magnetic fields near the welds in the pipelines when pipes are welded together are discussed. A spherical carrier equipped with a magnetic sensor is designed and is used to measure the magnetic field inside an annular experimental pipeline when the carrier is pushed forward by the fluid in the pipeline and is rolling along the pipeline. Theory and experimental research show that there are very obvious abnormalities of the magnetic field at the girth welds in the pipelines. The abnormal magnetic field near the welds can be remarkably enhanced and accurately located using the signal enhancement method of continuous wavelet transformation and the peak detection method based on quadratic polynomial fitting respectively, thus enabling the identification and location of the welds. Different approaches are adopted to process magnetic field signals of different intensities in the pipelines in different directions. Finally, by considering construction information on the pipelines recorded previously, the positioning error is kept to less than 5 cm.

Strengthening of Misaligned Welded Pipes with Outer Circumferentially Crack Using FRP Bandage Finite Element Analysis

Finite element analysis is used to investigate the effectiveness of Fiber Reinforced Polymers (FRP) bandage in rehabilitating misaligned welded pipes with outer circumferential surface crack. It is assumed that the pipes are subjected to an axial tensile stress. Linear Elastic Fracture Mechanics (LEFM) regime is adopted to estimate the stress intensity factor (SIF). ANSYS software is used in the study through 3D-axisymmetric finite element analysis. The results demonstrated that stiffening with FRP bandage has a great influence on the reduction of the stress intensity factor at the crack tip improving the fracture integrity of the misaligned welded pipes. The most common solution of the rehabilitation process for damaged pipes fabricated from metals is very important mater. The rehabilitation technique for pipes is needed because of external erosion and corrosion for pipes or due to external damages .Usually such process requires using heavy machines and skilled workers in addition to the time needed. By using Fiber Reinforced Polymers (FRP) techniques to increase the strength for existing pipes, it is very important for the corroded and damaged pipes to increase the resistance to the surrounding environment. The conventional techniques for repairing damaged pipes need operation of cutting, welding and inspecting in addition. This may also require stopping the system during the repair period. Furthermore, for many cases the repair process is undesirable because of the residual stress induced in the pipe during the welding process which tends to decrease the fatigue performance of the pipe material in addition to the weakness of the pipe wall due to any of corrosion types such as pitting. Therefore, the final rehabilitation cost using FRP is low compared with the traditionally usual trends using welding techniques. Pipeline welding contractors are very often used in mechanized and semi-automatic welding processes. It is generally accepted that the most welded structures enter service containing tiny cracks or flaws (1). Moreover, these flaws may extend to a size where the safety of the structure becomes dangerous. It is therefore essential that engineers and designers have methods of assessing the significance of flaws detected during manufacture or after the structure has entered its service life, especially the structures that are connected with the human safety, such as pipes. Generally, cracks in piping system often occur at welding joint and around it (2). Most of these cracks are located in circumferential direction. For this reason circumferential cracks play an important role in the safety analysis of pipes (3). Strengthening techniques have drawn attention by many researchers to investigate the effectiveness of the stiffeners in the rehabilitation processes through using experimental as well as finite element methods. Ahmed et al. (4-6) investigated the effect of using FRP strengthening techniques to rehabilitate structural members under numerous loading conditions through FEA. Mourad et al. (7-18) have studied the effect of stiffening on crack growth through three-point bending TPB, compact tension CT and compact shear CS specimens. Chang-Young Oh et al. (19) investigated existence methods to estimate stress intensity factors due to welding residual stresses and compared with finite element (FE) solution for welding residual stress profiles, generated by simulating repair welds and compared with analytical solution. On the other hand, finite element analysis (FEA) was carried out to obtain the elastic stress distribution at cylinder to cylinder junction in pressurized shell structures that have applications in space vehicle design (20). The peak stress value is found to reduce due to filleted butt joint as expected and also confirmed through test results. Pipes with a flawed girth weld for two common girth weld tension tests: the curved wide plate test and the full scale pressurized pipe tension test, and subjected to global plastic deformation were studied by finite element models (21). Xiaohui Chen et. al. (22) presented an overview of recent progresses in experimental investigation and finite element analysis (FEA) of ratcheting behaviour of pressurized piping. The stress-intensity factor for the circumferential semi-elliptical surface cracks in a hollow cylinder's cross