Stainless Steel Pipe Research Articles

Computational modeling and analysis of a fluid test rig

Nanofluids, which are suspensions of metallic or ceramic nanoparticle fillers in a variety of liquids, are a new category of heat-transfer fluids. Owing to the changes in thermal conductivity caused by nanofillers, they have thermal properties that are superior to those of conventional fluids; this leads to a more efficient heat transfer, making them attractive for various industrial applications. Using numerical models to support in situ experiments is necessary to analyze nanofluids’ thermal properties and flow; creating a test ring has been suggested to describe the characteristics and behavior of fluids under controlled conditions. Modeling and computational analysis support such advances, which are essential for understanding and optimizing phenomena occurring during experimental tests; the modeling and computational analysis of a test rig designed to characterize a diphenyl oxide/biphenyl blend base fluid are presented in this research work. The test rig design included an integrated stainless-steel piping system with a flow-controlled pump and heat exchanger; the computational model considers the conjugate effects of fluid dynamics to facilitate the construction of test rigs.

Field test and geologic-thermal-economic analysis of medium-depth borehole heat exchanger

Medium-depth ground source heat pumps with borehole heat exchanger are pivotal in energy-saving and decarbonization. The heat transfer performance of borehole is important for design, with stratum thermal conductivity significantly influencing heat exchange, and economic considerations also act as a vital constraint on technological advancements. However, there is limited on-site testing in severe cold regions, especially in the Songliao Basin. Stratum thermal conductivity usually relies on empirical values, and its diverse impacts are not integrated into borehole heat transfer model. Additionally, previous studies optimized borehole design only from the thermal perspective. To address these gaps, we conducted an inaugural test in Shenyang. Geologic-based heat transfer model explores the geological influences, heat transfer performance, and heat extraction cost. At a depth of 2500 m, the formation's thermal conductivity is 2.45 W⋅m⁻1 K⁻1. The heat extraction, at a flow rate of 26.0 m3 h−1, achieves 352.3 kW with an inlet-outlet temperature differential of 11.7 °C. The effects of saturation, porosity, and lithology on stratum thermal conductivity were also explored. Furthermore, considering heat extraction cost, optimal depths for borehole utilizing PE-RT II and stainless-steel vacuum pipe are 2790 m (10.3 CNY·W−1) and 3140 m (10.2 CNY·W−1), with critical depths, 2910 m, governing the selection of economic inner pipe. This research establishes medium-depth ground source heat pumps as the preferred choice for low-carbon transformation in building heating, domestic hot water, and industrial and agricultural heat applications.

Design and experimental study of electromagnetic ultrasonic single-mode guided wave transducer for small-diameter stainless steel tubes

ABSTRACT Small-diameter stainless steel pipes find widespread application in nuclear power systems. In order to detect surface axial wear defects that may occur during their service life, a circular fully enclosed probe has been developed for inspecting these small-diameter stainless steel pipes. The probe is composed of a periodic permanent magnet (PPM) and a racetrack-shaped coil. Through the optimised design of the PPM structure, two probes were devised to excite single flexural and single torsional modes, respectively. Furthermore, employing the non-equivalent concept, the torsional mode guided wave probe underwent optimisation, resulting in a 54% increase in the received signal amplitude. Finally, two types of guided wave probes were utilised to conduct detection experiments on artificially induced defects in an outer diameter 10 mm sample pipe. The results indicate that both T(0,1) and F(1,2) mode guided waves can detect axial defects. Moreover, the detection amplitude of the T(0,1) mode guided wave surpasses that of the F(1,2) mode guided wave by a maximum of 53%.

Experimental Study on the Erosion-Corrosion Characteristics of Desulfurization Slurry on Stainless Steel Pipe Materials.

The recovery of low-grade waste heat from power plants greatly benefits energy conservation and emission reduction during electricity generation, while the waste heat utilization directly from desulfurization slurry is a significantly promising method to deeply recover such low-grade energy and has been developed in practical application. However, the pipe materials are subjected to erosion and corrosion challenges due to the high level of solid compositions and the presence of harmful ions, such as Cl-1, which requires further evaluation under the condition of slurry heat exchange. The present study aimed at an experimental study on the erosion-corrosion characteristics of desulfurization slurry on three types of stainless steel, including type 304, 316L, and 2205. Both mass loss and micromorphology features were analyzed with possible mechanisms elucidated. The erosion-corrosion rate is weak at low temperatures, while the increase in the slurry temperature clearly promotes its rate. The influence of the temperature on the corrosion resistance of 304 is much greater than that of 2205. With an increase in duration time, the weight loss rate of stainless steel in the desulfurization slurry declines, and the changing trend of metal mass slightly slows down. The present study offers a better understanding of the erosion-corrosion behaviors of three types of stainless steel under flow and heat transfer conditions of a desulfurization slurry.

Analysis of Springback Characteristics of Bending Unloading for Stainless Steel tubes

Stainless steel tubes are widely used in piping systems in aviation, aerospace and other high-tech fields because of their high strength, excellent corrosion and high-pressure resistance, and good resistance to high-temperature oxidation. This paper takes 304 stainless steel pipe as the research object, based on ABAQUS finite element platform, the springback behaviour of stainless steel pipe in the process of precise bending and forming has been studied in depth. The results show that: pipe bending unloading bending springback angle increases with the increase of the bending angle. The results of the study have important theoretical and practical significance for improving the accurate forming and springback of stainless steel tube bending.

Distribution and Characteristics of Residual Stresses in Super Duplex Stainless Steel Pipe Weld

This paper explores the distribution and features of residual stresses formed by super duplex stainless steel pipe welding. Experimental investigations, which encompass an elevated temperature tensile test and metallographic observation along with a hardness test and residual stress measurement, were first conducted to obtain the mechanical properties at high base metal temperatures and to confirm whether or not the duplex stainless steel undergoes martensitic phase development during the welding process. Finally, experiments were performed to scrutinize the residual stress evolution through the metallurgical phase transformation in the weld region and its vicinity. A sequentially coupled 3D thermal, mechanical and metallurgical finite element (FE) model capable of incorporating the experimental consequences was established next. A 3D FE simulation of the girth welding process was conducted, and the axial and hoop residual stress profiles along the girth were evaluated. The results substantiate that martensitic phase evolution occurs in the process of cooling during the welding of super duplex stainless steel, and they also highlight the significance of taking the metallurgical phase transformation into account in the numerical reproduction of the girth welding process for the accurate expression of weld-induced residual stresses, which is especially important for precisely predicting hoop residual stresses.

APPLICATION OF MACHINE LEARNING FOR RECOGNIZING SURFACE WELDING DEFECTS IN VIDEO SEQUENCES

The paper offers a solution to the problem of detecting and recognizing surface defects in welded joints that appear during tungsten inert gas welding of metal edges. This problem belongs to the machine vision. Welding of stainless-steel edges is carried out automatically on the pipe production line. Therefore, frames of video sequences are investigated. Images of some welding defects are shown in the paper. An algorithm proposed by the authors is used to detect welding defects in the video sequence frames, the efficiency of which has been confirmed experimentally. The problem solution of welding defects recognition is based on the use of traditional machine learning methods: support vector machine and artificial neural network. To build classification models, a labeled dataset containing automatically extracted texture features from the areas of welding defects detected in the video sequences was created. An analysis was performed to identify the strength of the correlation of texture features between each other and the dependent variable in the dataset for dimensionality reduction of the feature vector. The models were trained and tested on datasets with different numbers of features. The quality of the classification models was evaluated based on the accuracy metric values. The best results were achieved by the classifier built using the support vector machine with a chi-square kernel on a training sample with two features. The build models allow automatic recognition of such welding defects as lack of fusion and metal oxidation. The computational experiments with real video sequences obtained with a digital camera confirmed the possibility of using the proposed solution for recognizing surface welding defects in the process of manufacturing stainless steel pipes.

Fracture investigation at 300oC on carbon-steel and austenitic stainless-steel pipes of NPPs under cyclic loads

The Leak-Before-Break (LBB) of high enthalpy piping of Indian NPPs require fracture stability demonstration of pipelines with postulated cracks under design basis earthquake loads. Earlier large number of cyclic fracture and corresponding monotonic fracture tests on large sized pipe components were conducted at room temperature. In current program, monotonic/cyclic fracture experiments are extended to reactor operating temperature (300 oC). The aim of this study is to demonstrate the structural integrity of SA333Gr6 piping and Stainless Steel (SS) 304LN welds under monotonic/cyclic loading which simulates extreme earthquake events and operating temperatures. Total six pipes/pipe welds of carbon steel (8-inch NB ~219 mm outer diameter and 19 mm thick) and SS304LN (12-inch NB~324 mm and outer diameter ~25 mm thick) with through-wall cracks have been tested under four-point bending. Two monotonic fracture tests have been conducted at 300 oC under monotonic loadings. Different experimental results like LLD (Load Line Displacement), Total Load, CMOD (crack mouth opening displacement), Crack Growth values have been obtained. Based on this data the load carrying capacity are obtained for both 8-inch and 12-inch cracked pipes. The cyclic fracture tests have also been conducted at 300 oC under fully reversing cyclic loading on four pipes. Three 8-inch SA333Gr6 pipes have been tested under different magnitude of peak load values. Similarly, one 12-inch SS pipe is also tested under cyclic loading. For carbon steel pipes, the reduction in load capacity is slightly higher under cyclic loadings at 300 oC compared to that at room temperature. However, for stainless steel pipes the load reduction factor at 300 oC is in good agreement with that at room temperature.

Thermal aging effects on Tensile and Metallurgical characteristics of Stainless steel weld joint

A girth austenitic stainless steel (say, SS) weld joints are invariably used for joining piping components in typical light water based nuclear power reactor. To avoid hot cracking during the welding of SS, some 5-8% delta ferrite is required in the filler material, which remains in the metastable phase in weld pool. Under prolonged exposure at operating temperature (300 ℃), these delta ferrite which remains in weld metal may get transformed to brittle phases that leads to reduction in its ductility and toughness. Hence, for prolonged safe operation of these piping components in power reactors, it is important to quantify the amount of degradation in toughness and ductility because of thermal aging. Therefore, present work aims at quantifying the reduction in toughness in SS weld joint by carrying out accelerated thermal ageing and thereafter carrying out micro-structural examinations, hardness and tensile tests on specimens machined from different regions of weld joint. Austenitic stainless steel (SA312 Type 304LN) pipe weld joints have been prepared using Gas Tungsten Arc Welding (GTAW) for root passes and Shielded Metal Arc Welding (SMAW) for filling passes. Full-scale pipe weld were subjected to thermally ageing for 10,000 and 20,000 hours at temperature 400 ℃. The effects of thermal aging on the structural morphology, hardness at macro and micro-scale and tensile characteristics of different zones of these joints have been quantified. Micro-structural examination reveals vermicular and lathy morphology in the ferrite and austenite phase. It has been found that, thermal aging leads to significant increase in ferrite hardness and reduction in ductility for the weld specimen from SMAW compared to that of the GTAW and no effect in heat affected zone.

Modeling and simulation of welded joints of SS304H & P91 Steels: A Review

Most of the structures are fabricated by welded joints in various manufacturing units because of low cost and high strength. Welding process is largely used in almost all manufacturing units. Welded joints usually subject to welding deformation patterns. Welding deformation may lead to low dimensional accuracy, shape and aesthetics of the product, strength of the welded joint. Welding of two different materials having different mechanical properties is called dissimilar welding. Dissimilar welded joints are commonly used in power plants to connect martensitic steel components and austenitic stainless steel piping systems. Our approach involves conducting dissimilar welding on P91 and SS304H steels, and subsequently assessing the properties of the welded joints using simulation software. A 3-D thermal elastic plastic finite element computational process is designed to accurately forecast welding deformation by numerical method. Numerical and experimental outcomes were compared in terms of temperature distributions during welding and in terms of distortion. P91 is a chromium-molybdenum alloy known for its remarkable strength and exceptional resistance to high temperatures. Alloy SS304H represents an adaptation of the chromium-nickel austenitic stainless steel. This variant, Grade 304H stainless steel, offers enhanced heat-resistant properties, increased tensile yield strength, and improved short- and long-term creep strength.

Simulation of crack propagation in piping components using phase field approach

Understanding the fracture behaviour in pipelines transporting steam and other resources is vital for its longevity and structural integrity. The prediction of crack initiation and propagation, involving crack branching, and the nucleation of new cracks, etc. in fracture processes are challenging tasks. The phase field method (PFM), based on variational formulation, emerged as a competitive mathematical tool to address fracture mechanics problems. PFM does not require the presence of predefined cracks, handles the crack initiation and propagation within the same system. This feature provides an added advantage to PFM and overcomes the limitations of Griffith’s approach-based linear elastic fracture mechanics (LEFM). In the present work, simulation of the crack propagation in the piping components by employing phase field methodologies has been carried out. Two parameters namely; a phase field parameter (ϕ) that varies between 0 and 1 differentiating between broken and intact material, and a length scale parameter (l_0) that approximates the sharp crack into the diffused crack with exponential distribution are introduced in the mathematical modeling. Numerical modeling is solved using the staggered algorithm in three layered scheme defining the displacement field and phase field within a 3-D finite element framework and implemented in Abaqus via user-defined element (UEL) subroutine codes. PFM simulates the crack path and predicts the load-displacement response, which is validated with benchmark problems, and extended for piping components under monotonic loading. The proposed study accurately captures the crack growth behaviour as observed in experiments on SA312 Type 304LN stainless steel pipes and hence, demonstrated the robustness of the proposed formulation.

Prediction of Residual Stresses in 316 Stainless Steel Pipes Welded Joint

Due to the extremely complicated thermal cycle for the welding process, the fusion zone and heat-affected zone (HAZ) produce irreversible elastic-plastic deformation and residual stresses. The differential heating of the pipes caused by the weld heat source causes residual stress as a result of the welding process. However, the strength and lifetime of the component are also decreased as a result of residual stresses in and around the weld zone. The objective of this research is to analyze the residual stresses created during the welding process and select the best welding parameters that give the lowest residual stresses in 316SS pipes with 50 mm diameter and 4 mm thickness that were manually welded by used (316) welding wire and using shielded metal arc welding (SMAW) in a single-pass butt joint with the various values for each of current (58, 68, 78, 88) amperes and voltage (22, 23, 24, 25, 26) volts. The shielded metal arc welding process involves heating, melting, and solidifying the parent metals and filler material in a localized fusion zone by a transient heat source to create a junction between the parent metals. The welding process free from preheating and heat treatment will be obtained. ANSYS Finite Element methods are used to calculate the welding residual stress distribution. The mechanical and thermal models were used to carry out the theoretical analysis. In general, the numerical study found that the residual stress distribution at the weld zone’s center is continuous, rising, and has a value of about (1738 MPa). Additionally, the residual stress at the boundary between the heat-affected zone and the weld zone climbs to a maximum value of around (3799.6 MPa). On the other hand, the magnitude of the residual stress in the heat-affected zone of the weld reduces significantly and achieves a minimum value at a position of (20 mm) with a value near zero.

Stress Measurement of Stainless Steel Piping Welds by Complementary Use of High-Energy Synchrotron X-rays and Neutrons

Probabilistic fracture mechanics (PFM) is increasingly recognized as a viable approach for evaluating the structural integrity of nuclear components, such as piping, primarily affected by stress corrosion cracking (SCC). PFM analysis requires several input parameters, among which welding residual stress is critically important due to its significant influence on SCC initiation and propagation. Recently, a novel technique involving a double-exposure method (DEM) utilizing synchrotron X-rays was introduced as an effective means for measuring welding residual stress with high spatial resolution. In this paper, we applied DEM to assess the residual stress of a plate specimen, which was extracted from a welded pipe through electrical discharge machining. Consequently, detailed stress maps under a plane stress state were generated. Additionally, the residual stress distributions in the welded pipe under a triaxial stress state were evaluated using neutron diffraction. Based on these findings, we proposed a methodology to acquire detailed stress maps of welded pipes by combining high-energy synchrotron X-rays and neutron diffraction.

Predictive modeling of coke formation in ethylbenzene cracking on 304 H austenitic steel surface using response surface methodology (RSM)

In ethylbenzene dehydrogenation process, the produced coke is the main source of catalyst deactivation, deterioration of stainless steel piping (carburization) and the flow pass plugging. The novelty of this work is determination, ranking and modeling of influencing factors and their interactions on the rate of coke formation in ethylbenzene dehydrogenation process including independent parameters such as styrene and toluene concentrations, surface temperature, the reactor shape factor and steam to ethylbenzene (St/EB) weight ratio. A laboratory setup was used to investigate the effect of above listed parameters and the response surface methodology (RSM) was used to analyze the experiments and optimize the parameters. The ANOVA results illustrated that the model is significant and able to predict coke. The p-values for all parameters are less than 0.05, indicating these parameters are effective factors on coke formation. The results revealed that by increasing styrene and toluene concentrations and surface temperature, the rate of coke formation increases. In such circumstances, surface temperature showed maximum effect due to the increase of cracking reactions and the production of coke precursors such as stilbene, anthracene etc. On the other hand, the effect of St/EB weight ratio on the rate of coke formation is inverse. The results obtained from SEM/EDS analysis showed the filamentous coke forms on the surface of 304 H austenitic steel.

Parameter Optimization in Orbital TIG Welding of SUS 304 Stainless Steel Pipe

The influence of welding angle, welding current, travel speed, pulse time, and torch height on the geometry, macrostructure, and mechanical properties of Tungsten Inert Gas (TIG) orbital welding on an SUS 304 stainless steel pipe is investigated in this study. The results show that an electrode angle of 45° produces better weld joints than angles of 30°, 60°, 90°, and 120°. Furthermore, the electrode angle of 30° results in an acceptable weld width but a low depth of penetration (DOP) value. Welding current and weld speed have a significant impact on heat dispersion during TIG welding of an SUS 304 stainless steel pipe. The high welding current may result in blow-hole flaws, particularly near the conclusion of the welding process when heat is accumulated. A long torch height of 2 mm causes unevenness in the weld joints because the arc may be distorted when compared to shorter torch height cases. The pulse time of 0.2 s is too lengthy for a low-welding current situation because it will generate a small weld pool. As a result, the weld pool solidification process speeds up, and porosity emerges in the weld bead. A pulse time of 0.1 s results in a better weld joint. To avoid blow-hole creation, the welding current should be gradually reduced during the process. In addition, the Taguchi results demonstrate that the welding current has the greatest effect on the ultimate tensile strength (UTS) value, followed by welding speed, pulse time, electrode angle, and torch height. Furthermore, the ideal parameters for the UTS value are an electrode angle of 45°, a torch height of 2.0 mm, a welding current of 174 A, a welding speed of 72 mm/min, and a pulse time of 0.3 s.

АВТОМАТИЧЕСКОЕ РАСПОЗНАВАНИЕ ПОВЕРХНОСТНЫХ ДЕФЕКТОВ СВАРКИ ПРИ ПРОИЗВОДСТВЕ ГИБКИХ ТРУБ ИЗ НЕРЖАВЕЮЩЕЙ СТАЛИ

The paper describes the automatic recognition of surface welding defects on video stream frames while manufacturing flexible stainless steel pipes. The defects that appear during automatic tungsten inert gas welding are studied. A universal algorithm based on the background subtraction method is presented for detecting and localizing various welding defects on video stream frames. A solution to the problem of recognizing such defects as lack of fusion and scaled surface is also proposed. A dataset containing texture features of defects was created. Classifiers were trained using the support vector machine. Experimental studies have shown that the proposed solutions allow for prompt detection of any deviations occurring during metal welding and recognize certain welding defects on the processed frames of the video stream.

Numerical study of the process of bending small diameter stainless steel pipes

Numerical study of the process of bending small diameter stainless steel pipes

Numerical Simulation of the Effect of Fusion Welding Processes on Residual Stress in Stainless Steel Pipe Weld Joints Used in Fast Reactors

The main structural material used in the building of Fast Breeder Reactors (FBR) is stainless steel of type 316L(N). Finite Element Model (FEM)-based simulations were carried out to understand the effect of various welding processes on the residual stresses induced in 316L(N) stainless steel primary sodium-carrying pipes with an inner diameter of 208 mm and a wall thickness of 5.6 mm. The welding processes considered include multi-pass Tungsten Inert Gas (TIG) welding, A-TIG, laser, hybrid laser-TIG, and Hybrid laser-Metal Inert Gas (MIG). First, single or hybrid heat sources are chosen based on the welding process, and then weld bead profiles obtained during simulation are made to match with that of the actual weld bead profiles obtained during experiments. Then, the optimised heat source is employed for the thermal analysis. The thermal analysis output is then successively linked and provided as input to the mechanical analysis, which uses an isotropic hardening model to predict hoop and axial residual stresses in pipe weld joints. The results show that the A-TIG weld joint exhibited lower hoop stress (165 MPa at inner diameter and -2 MPa at outer diameter) in comparison with that of the other weld joints. The lower residual stress is attributed due to the straight-sided weld bead, lower peak temperature, and slower cooling rate of the A-TIG welding. Therefore, A-TIG welding is recommended among the chosen fusion welding processes for welding of 316L(N) stainless steel primary sodium carrying pipes to minimise the residual stresses and mitigate the premature failure of the pipe weld joints.

Study of welding parameters’ effects on residual stress and hardness in 316 stainless steel pipes: Experimental and analytical investigations

Study of welding parameters’ effects on residual stress and hardness in 316 stainless steel pipes: Experimental and analytical investigations

The interaction between extracellular polymeric substances and corrosion products in pipes shaped different bacterial communities and the effects of micropollutants

There are growing concerns over the effects of micropollutants on biofilms formation and antibiotic resistance gene (ARGs) transmission in drinking water distribution pipes. However, there was no reports about the influence of the interaction between extracellular polymeric substances (EPS) and corrosion products on biofilms formation. Our results indicated that the abundance of quorum sensing (QS)-related genes, polysaccharide and amino acids biosynthesis genes of EPS was 6747–8055 TPM, 2221–2619 TPM, and 1461–1535 TPM in biofilms of cast iron pipes, respectively, which were higher than that of stainless steel pipes. The two-dimensional correlation spectroscopy (2D-COS) analysis of attenuated total reflectance–Fourier transform infrared spectrometry (ATR–FTIR) results indicated that polysaccharide of EPS was more easily adsorbed onto the corrosion products of cast iron pipes. Therefore, more human pathogenic bacteria (HPB) carrying ARGs were formed in biofilms of cast iron pipes. The amide I and amide II components and phosphate moieties of EPS were more susceptible to the corrosion products of stainless steel pipes. Thus, more bacteria genera carrying mobile genetic elements (MGE)-ARG were formed in biofilms of stainless steel pipes due to more abundance of QS-related genes, amino acids biosynthesis genes of EPS and the functional genes related to lipid metabolism. The enrichment of dimethyl phthalate (DMP), perfluorooctanoic acid (PFOA) and sulfadiazine (SUL) in corrosion products induced upregulation of QS and EPS-related genes, which promoted bacteria carrying different ARGs growth in biofilms, inducing more microbial risks.