Socket Weld Research Articles

Design and implementation of power socket soldering robot arm system

Abstract In order to solve the problem of high cost and low efficiency in manual welding of power socket welding components, a soldering robot arm system was developed. The gripper, 5-DOF manipulator, clamp, support, and control system were designed. The coordinate system of the robot arm was constructed, and the working space of the robot arm was analyzed by using the MATLAB robot toolbox. It was concluded that the x0 coordinate range of the welding working area was [175mm, 215mm], the y0 coordinate range was [55mm, -55mm], and the z0 coordinate was 90mm. At the same time, the motion trajectory of the robot arm was determined. Using Raspberry PI as a controller, the control system is developed by programming Python language. The prototype is made, and a welding test is carried out. The test shows that the system has completed the welding operation, and the welding effect is good.

Leakage Analysis of Steam Condensate Pipe Elbow

The cause of leakage of a steam condensate pipe elbow has been carried out by means of chemical composition analysis, fracture surface analysis and numerical simulation. The results show that the inner wall of the pipe at the socket welding of the downstream pipe elbow of the steam trap is not enough smooth, and the inner diameter suddenly changes, resulting in a sudden increase in the flow velocity, which increases the erosion-corrosion rate of the pipe wall, and finally leads to the elbow leakage.

Numerical Prediction of Strength of Socket Welded Pipes Taking into Account Computer Simulated Welding Stresses and Deformations.

The paper presents a numerical model based on the finite element method (FEM) to predict deformations and residual stresses in socket welding of different diameter stainless steel pipes made of X5CrNi18-10 steel. The next part of the paper concerns the determination of strength properties of a welded joint in terms of a shear test. A thermo-elastic–plastic numerical model is developed using Abaqus FEA software in order to determine the thermal and mechanical phenomena of the welded joint. This approach requires the implementation of moveable heat source power intensity distribution based on circumferentially moving Goldak’s heat source model. This model is implemented in the additional DFLUX subroutine, written in Fortran programming language. The correctness of the assumed model of thermal phenomena is confirmed by examinations of the shape and size of the melted zone. The strength of the welded joint subjected to shear is verified by performing a compression test of welded pipes as well as computer simulations with validation of the computational model using the Dantec 3D image correlation system.

Realization of Parameterized Serialization Design of Flanges in Chemical Equipment

Flanges are important parts in the fields of machinery, chemicals, wind power, and sewage treatment. They are used in large quantities and have formed a series of products at present. In the paper, the secondary development of AutoCAD was adopted to parameterized series design, and 960 parts from 4 series flange (plate flat welding flange, neck flat welding flange, neck butt welding flange, socket welding flange) were drawn. The efficiency of part design has been significantly improved.

Polyethylene pipe socket welding technology in mining

The proposed technology of polyethylene pipe socket welding can be used in construction of polyethylene piping systems in the mining industry. Based on numerical simulation of thermal process, the effect of low temperatures on the temperature field dynamics in socket weld joint is investigated. The need of preheating and usage of thermal insulation at the cooling stage during welding at low temperatures for the thermal process to develop according to the patterns of welding at acceptable temperatures is shown. A procedure is given for determining the size of a heat-insulating chamber for cooling a welded socket joint at low temperatures from the condition of ensuring the cooling rate characteristic of welding at permissible temperatures.

Socket welding of polypropylene pipes with a heated tool at negative ambient temperatures

The paper presents the results of study, which considered relationship between supramolecular structure and strength of polypropylene pipes joints obtained by socket welding with heated tool at various ambient temperatures, including negative ones.

Experimental evaluation of fatigue strength for small diameter socket welded joints under vibration loading condition

To investigate how the fabrication and repair of socket welded joints could be used to enhance fatigue resistance under vibration condition, experimental test data of installation conditions that potentially influence fatigue strength were analyzed with the S–N curve. It was found that the decreasing fatigue strength of stainless steel socket welded joints was attributed to the effect of high heat input of welding process. The effect of welding method, slip-on gap and radial-gap conditions on fatigue strength was insignificant. The test data of repair technique application, 2 × 1 leg length and of socket weld overlay, clearly showed higher fatigue strength but there was a limitation for higher stress region because of the weld toe crack.

Numerical Study on the Cavitation Flow and Its Effect on the Structural Integrity of Multi-Stage Orifice

Flow leakage due to cavitation erosion occurred at the socket welding part downstream of the multi-stage orifice installed in the auxiliary feedwater (AFW) pump recirculation line of the domestic nuclear power plant (NPP). To assess the adequacy of the changed operating flow rate proposed by a domestic NPP operator as the corrective measure concerning the flow leakage in the AFW pump recirculation line, the pattern of the cavitation flow in the eight-stage orifice and the connecting pipe depending on the magnitude of the operating flow rate was predicted by using ANSYS CFX R19.1. Additionally, using ANSYS Mechanical, the structural analysis was conducted under the same operating flow rate condition used for the flow analysis, and the structural integrity was evaluated for the allowable stress. Based on the flow analysis results, it was found that the operating flow rate was the main factor to influence the cavitation behavior inside the multi-stage orifice, and cavitation flow still happened even in the vicinity of the corrected operating flow rate, so it should be necessary to fundamentally review the adequacy of the multi-stage orifice design. On the other hand, the geometric dimensions and arrangement of orifice hole position at the individual stage of the multi-stage orifice may have a significant influence on the characteristics of pressure drop and flow patterns (including cavitation). Therefore, these effects were examined by simulating an analysis model in which the hole diameter of the eighth-stage orifice was changed under the design flow rate condition. As a result of flow analysis, it was found that reducing the hole diameter in the eighth stage orifice resulted in increasing the pressure drop. In relation to the structural integrity of the eight-stage orifice and the connecting pipe, it was found that its integrity could be maintained under the design and operating flow rate conditions.

Selective Corrosion of Socket Welds of Stainless Steel Pipes Under Seawater Atmosphere

Stainless steel has excellent corrosion resistance. The drawback is that pitting occurs easily due to the concentration of chloride. In addition, corrosion of socket weld, which is structurally and chemically weaker than the other components of the pipe, occurs rapidly. Since these two phenomena overlap, pinhole leakage occurs frequently in the seawater pipe socket welds made of stainless steel at the power plants. To analyze this specific corrosion, a metallurgical analysis of the stainless steel socket welds, where the actual corrosion occurred during the power plant operation, was performed. The micro-structure and chemical composition of each socket weld were analyzed. In addition, selective corrosion of the specific micro-structure in a mixed dendrite structure comprising γ-austenite (gamma-phase iron) and δ-ferrite (iron at high temperature) was investigated based on the characteristic micro-morphology and chemical composition of the corroded area. Finally, the different corrosion stages and characteristics of socket weld corrosion are summarized.

DEVELOPMENT OF TECHNOLOGY OF POLYETHYLENE PIPES SOCKET WELDING FOR MINING INDUSTRY

DEVELOPMENT OF TECHNOLOGY OF POLYETHYLENE PIPES SOCKET WELDING FOR MINING INDUSTRY

Structure and strength research of polymer pipe welded joints

Research results of the effect of low ambient air temperatures during welding on structure and strength of polymer pipes welded joints are given. The connection of polymer pipes was made in two main ways: by hot element butt welding and socket welding. Structure studies of the material of welded joints have shown that the welding technologies developed at IOGP SB RAS provide formation of the same structure in the material of welded joints as in standard welding.

Welding Polymer Pipes at Low Climatic Temperatures

The results of the research on development of technology for welding polymer pipes at low climatic temperatures in open air without the use of temporary heated structures are presented. The most common welding methods are considered: butt welding with a heated tool, electrofusion welding with embedded heating element and socket welding. Tests on welded joints show that the developed technology for welding in open air without the construction of shelters provides the same level of quality as when welding at admissible temperatures.

沙特哈拉德项目场站承插焊接质量控制

沙特哈拉德项目场站承插焊接质量控制

Evaluation of Stress Relaxation Cracking on 800HT Pigtails of the Steam Reformer

Stress relief cracking occurs when susceptible alloys are subjected to thermal stress after welding to reduce residual stresses and improve toughness. Cracks were observed on the external surface of the outlet pigtails of a steam reformer. The failures (cracks) occurred at the toe of the socket weld connecting the pigtail to the catalyst tube. Design parameters are 900 °C and 22 barg; the actual operating conditions are 875 °C and 20 barg. The material of construction is Alloy 800HT, which is an iron–nickel–chromium alloy. The outlet pigtail was used to transfer the process fluid of the steam reformer which is connected to a manifold header. It was requested to conduct a failure analysis on damage in the outlet pigtail tubes that occurred in the form of cracks. The failure analysis study is described in detail in this paper, and the mechanism of the crack is identified and proper recommendation is given to avoid such issues in future operations.

Effects of stress concentration and residual stress on vibration fatigue behavior of socket weld

The vibration fatigue behavior in socket weld of 304L stainless steel was investigated using experimental and numerical. The vibration fatigue test results indicate that original socket weld at a higher stress tend to occur toe failures while for the case of lower stress failures tend to originate at the root. In addition, the socket welded with groove can improve the fatigue property of weld root, but it has a bad influence on the weld toe. From the simulation results, the groove can decrease the stress concentration factor of weld root, and improve the fatigue property of root; whereas the groove can also increase the tensile residual stress of toe, resulting in having a detrimental effect on fatigue property of toe.

Study on residual stress in socket weld by numerical simulation and experiment

In this paper, welding residual stress in socket weld of 304L stainless steel pipe was investigated using numerical simulation and validated by X-ray stress measurement. From the simulation results, the maximum tensile residual stresses were located at weld root and weld toe on both sides of the weld along pipe, which led to the fatigue failure. Pre-bevelling and low transformation temperature (LTT) dressing could decrease tensile residual stress both in hoop and axial direction at weld root and weld toe. After LTT dressing, compressive residual stress was generated throughout weld toe. Compressive stress can delay fatigue crack initiation and propagation. Therefore, pre-bevelling and LTT dressing can improve the fatigue life of socket weld.

Numerical Simulation of Stress Intensity Factor for Socket Weld Toe Cracks in Small Branch Pipes

Vibration fatigue of small branch pipes usually induces weld toe cracks. Some cracks will cause advertently shutdown of the Nuclear Power Plants (NPPs). Moreover, to judge the vibration fatigue failure is the bottle neck in structure health monitoring of the small branch pipes in NPPs. In order to solve this problem, a socket weld pipe was simplified as the cantilever beam model, and the stress intensity factor (SIF) was calculated by the ABAQUS software and ZENCRACK software in this paper. The effects of crack depth, circumferential crack size and working load on SIF were discussed. The analysis results show that the SIF for outer surface circumferential crack distributes as an upside down “U” alphabet. And the maximum value of SIF is at the deepest point of the crack and is a linear increasing function of external load P. Basing on the plane strain fracture criterion, critical crack sizes bearing different external loads were calculated. With the increasing of loads, the critical crack size decreases. These critical values can be applied as the benchmark for evaluating the vibration fatigue failure in the structure health monitoring of small branch pipes in NPPs.

Steam generator small bore piping socket weld inspection using the phased array ultrasonic technique

As nuclear power plants age, the likelihood of failures in the small bore piping used in those plants caused by exposure to mechanical vibrations during plant operations increases. While small bore piping failures rarely cause plant shutdown, the management of small piping has been a keen area of interest since their repair or maintenance requires a reactor trip. Steam generator (SG) drain pipe socket welds are small diameter piping connections (nominal pipe schedule 3–4 inches) susceptible to mechanical vibration. SG drain pipe socket weld failures have caused coolant leakage. Therefore, more reliable inspection technologies for small bore piping need to be developed to detect problems at an early stage and prevent pipe failures. This research aims to improve the reliability and accuracy of small bore piping inspections through the design, manufacture and application of a new phased array ultrasonic testing technique and inspection system for SG drain line socket welds.

Control of the thermal process of welding polyethylene pipes at low temperatures

Results of investigation of the effect of the temperature of the surrounding air on the dynamics of the temperature field in socket welding of polyester and pipes are presented. It is shown that in order to ensure the permissible dynamics of the temperature field at the air temperature below standard temperatures, it is necessary to preheat the socket prior to welding together with the welded sections of the pipes, and the welded joint should be cooled under a layer of heat-insulating material.

원전 소구경 배관 소켓용접부 위상배열 초음파검사 기술 개발

소구경 배관 용접부 손상은 원자력발전소에서 빈번하게 발생되고 있는 문제이며, 이러한 손상은 보수를 위한 불시정지를 야기하고 결과적으로 발전소에 경제적인 손실을 초래한다. 따라서 소켓용접부의 제작결함 검출과 초기 성장 결함의 검출은 매우 중요하다고 할 수 있다. 지금까지 해당부위에 대한 검사는 ASME Code Section XI 요건에 의하여 표면검사를 적용하여 왔으나 강화검사로 체적검사기법인 초음파검사를 병행하여 수행하고 있다. 그러나 가동중에 발생되는 피로균열을 검출하기 위하여 적용되고 있는 일반 수동 초음파검사는 소켓용접부의 접근성과 초음파 탐촉자의 접촉 문제 등으로 인하여 검사 결과의 신뢰성에 문제가 있어 왔다. 본 연구에서는 위상배열 초음파검사 기술을 적용하여 소구경 배관 소켓용접부의 검사 신뢰성과 속도를 향상하고자 하였다. 이를 위하여 소구경 배관 소켓용접부 검사를 위한 3.5 MHz 위상배열 초음파 탐촉자를 제작하고 탐촉자의 접촉 조건과 일정한 신호 품질을 유지하기 위하여 수동 엔코더 스캐너를 개발하였다. 또한 검사 시스템을 구성하고 현장 검사를 위한 절차서도 개발하였다. Failure of small bore piping welds is a recurring problem at nuclear power plants. And the socket weld cracking in small bore piping has caused unplanned plant shutdowns for repair and high economic impact on the plants. Consequently, early crack detection, including the detection of manufacturing defects, is of the utmost importance. Until now, the surface inspection methods has been applied according to ASME Section XI requirements. But the ultrasonic inspection as a volumetric method is also applying to enforce the inspection requirement. However, the conventional manual ultrasonic inspection techniques are used to detect service induced fatigue cracks. And there was uncertainty on manual ultrasonic inspection because of limited access to the welds and difficulties with contact between the ultrasonic probe and the OD(outer diameter) surface of small bore piping. In this study, phased array ultrasonic inspection technique is applied to increase inspection speed and reliability. To achieve this object, the 3.5 MHz phased array ultrasonic transducer are designed and fabricated. The manually encoded scanner was also developed to enhance contact conditions and maintain constant signal quality. Additionally inspection system is configured and inspection procedure is developed.