Pressure Vessel Research Articles

Hydroforming and buckling of a longan-shaped pressure vessel with longitudinal tension rods

ABSTRACT The hydroforming process of a longan-shaped multi-segmented preform with longitudinal tension rods and the buckling behaviour of a hydroformed longan-shaped pressure vessel were numerically and experimentally investigated. The shape of the longan followed the Cassini oval equation, with a shape index of 0.1. A preform with a nominal size of 400 mm for the major axis, 396 mm for the minor axis and a wall thickness of 1 mm was fabricated. Two longitudinal tension rods with a radius of 3 mm and a length of 420 mm were employed in the multi-segmented preform, which was the first to use longitudinal tension rods in the preform. The numerical analysis and experimental results showed that the excessive deformation of the polar plates was significantly reduced. Simultaneously, the overall geometric accuracy of the hydroformed pressure vessel was significantly improved. The results of the analytical, experimental and numerical approaches are in good agreement with one another.

Exploring stress and deformation in filament-wound composite pressure vessel liners using PyMAPDL

PyMAPDL, which stands for Python based Mechanical Ansys Parametric Design Language, provides a Pythonic interface to Ansys for automating tasks and managing multiple simulations. The present study focuses on utilizing PyMAPDL to numerically explore the stress and deformation conditions in the domed section of a cylindrical liner, specifically by analyzing ellipsoidal and torispherical dome shapes through the creation of a parametric model in Python. The output suggests a better selection of the dome geometrical parameters. The study extends to filament-wound composite pressure vessels, emphasizing the challenges in determining winding angles and layer thickness variations along the meridian line in dome parts. Cadfil software is used to obtain the thickness and angle variation of the composite layers, and the output data from Cadfil is imported into Ansys ACP as lookup table to generate the composite layer for linear elastic analysis of single composite layer on the liner. The findings suggest that a lower helical angle enhances strength protection in the dome section.

The optimal design of composite overwrapped pressure vessels based on geodesic dome trajectories using population-based techniques

Pressure vessels are frequently fabricated using composite materials which stand out with their high strength-to-weight ratio, and provide considerable advantages compared to conventional steel ones. In our previous study, the impacts of Polar Opening Radius (POR) on the mechanical characteristics of Composite Overwrapped Pressure Vessels COPVs were numerically examined, and it was determined that effective volume and structural weight responses improved with higher POR, but significant deterioration took place in first-ply interlaminar shear stress (ILSS) responses after 20 mm POR. Therefore, to achieve the best possible mechanical and structural behaviors, the present study aimed to discover an optimum POR that provides maximum internal volume as well as minimum weight and ILSS responses. In this regard, the optimum geodesic dome trajectory based on the 10–30 mm POR range was determined using the Bees Algorithm (BA) and the Particle Swarm Optimization (PSO). According to the findings, the optimum POR was found as 17.9643 and 17.9671 mm due to the BA and PSO algorithms, respectively. Moreover, first-ply ILSS, structural weight and effective internal volume for the optimal COPVs design were achieved as 52.444 MPa, 1070.81 g, and 2721.94 cm3 from the BA, and thus COPVs with maximum strength and minimum structural weight has been designed. In this way, thanks to the optimization studies, an approximately 18.31% improvement in ILSS responses was achieved despite the negligible deterioration in weight and volume compared to the COPVs with a 30 mm POR.

Analysis of Shift in Nil-Ductility Transition Reference Temperature for RPV Steels Due to Irradiation Embrittlement Using Probability Distributions and Gamma Process

Reactor pressure vessel (RPV) steels are highly susceptible to irradiation embrittlement due to prolonged exposure to high temperature, high pressure, and intense neutron irradiation. This leads to the shift in nil-ductility transition reference temperature—∆RTNDT. The change in ∆RTNDT follows a certain distribution pattern and is impacted by factors including chemical composition, neutron fluence, and irradiation temperature. Existing empirical procedures can estimate ∆RTNDT based on fitting extensive irradiation embrittlement data, but their reliability has not been thoroughly investigated. Probability statistical distributions and the Gamma stochastic process were performed to model material property degradation in RPV steels from a pressurized water reactor due to irradiation embrittlement, with the probability models considered being normal, Weibull, and lognormal distributions. Comparisons with existing empirical procedures showed that the Weibull distribution model and the Gamma stochastic model demonstrate good reliability in predicting ∆RTNDT for RPV steels. This provides a valuable reference for studying irradiation embrittlement in RPV materials.

Experimental and modeling study on irradiation effect of A508-Ⅲ steel

Irradiation can induce microscopic defects in reactor pressure vessel (RPV) steel, resulting in macroscopic hardening and embrittlement. This paper proposes a micro‑meso-macroscale calculation framework for the mechanical properties of irradiated RPV steel based on experimental and numerical investigations. The mean size and number density of Fe-ion-irradiation-induced dislocation loops were measured using transmission electron microscopy (TEM). These parameters were described by a power-function relationship with the irradiation dose at various temperatures and were used as input parameters for the crystal plasticity finite element model (CPFEM). Nano-indentation tests of A508-Ⅲ steel under different irradiation conditions were successfully simulated. In addition, microstructural characterization and molecular dynamics (MD) simulations revealed the phenomenon of dislocation pinning and the sweeping of irradiation defects during dislocation migration, implying that the dislocation-loop interactions could be responsible for the formation of dislocation channels and curved dislocation lines. Furthermore, increase in yield stress and the ductile-brittle transition temperature (DBTT) at various temperatures were investigated. Results indicated that yield stress, DBTT, and the degree of irradiation hardening and embrittlement increased with the irradiation dose and decreased with irradiation temperature. Finally, the adjusted reference temperature (ART), a significant design parameter for nuclear reactors, was calculated and evaluated using the multiscale framework. The framework can serve as a reference text for extending the life of nuclear reactors.

Analysis of remaining life assessment of three-phase gravity separator for oil rectification with the simultaneous usean RBI matrix

The paper presents a detailed description of the oil rectification process used in upstream oil and gas plants, including the significant equipment involved. One such equipment highlighted in the study is a pressure vessel utilized as a separator to separate the liquid and gas phases. This pressure vessel has been in operation for over two decades. A thorough examination of the mentioned pressure equipment was conducted during the process evaluation. It was discovered that the internal side of the vessel, particularly its back elliptical head, had suffered extensive damage due to erosion and corrosion, emerging as the most significant cause of the deterioration. The application of RBI-estimation revealed that the vessel falls under the category of highly risk equipment, and there is a significant risk of both environmental and financial consequences associated with its potential failure (leakage). Such failure is anticipated to occur promptly in the area below the wear plate of the vessel's nozzle.

Effect of gasket material on flange face corrosion

Bolted flanged joints play a crucial role in connecting pressure vessels and piping systems. The corrosion of the flange surface is one of the most common causes of leakage failure in bolted flanged joints. This research investigates the effect of three gasket materials on the corrosion behavior of 321 stainless steel flange material using a novel setup specially designed for corrosion quantification of such assemblies. The results show that graphite gaskets cause more corrosion to flange surfaces under the same working conditions compared to graphite gaskets with metal foil inserts and virgin polytetrafluoroethylene (PTFE) gaskets. The mechanism of flange face corrosion is that, for PTFE gaskets, corrosion propagation mainly occurs at the gasket inner diameter and propagates through the depth of the flange while, for graphite gaskets, corrosion occurs on the whole contact surface of the flange and the gasket.

Effect of layup sequence on cure deformation and accurate prediction of composite pressure vessels

The application of composite winding pressure vessels is becoming more and more widespread, and the magnitude of deformation during curing can have a significant impact on service performance, but there are fewer studies on the accurate prediction of the numerical and experimental validation of the deformation during the curing process of pressure vessels. To accurately predict the effect of different angles of layup on the curing deformation of high-pressure hydrogen storage vessels made of T700S-12 K/4251A4B2 carbon fiber/epoxy composites in cylindrical and dome sections. In this paper, WCM-ABAQUS segmented pressure vessel accurate modeling method is proposed for the first time, using the method of converting the chemical shrinkage coefficient of epoxy resin into thermal expansion coefficient equivalently, the finite element prediction of the deformation of the pressure vessel during the curing process in different layup sequences was carried out, and the deformation values of the pressure vessel in different layup sequences were analyzed comparatively. Finally, the winding curing experiments were carried out on pressure vessels with different layup sequences, and the curing deformation values of the experimental tests on pressure vessels with different layup sequences were compared with the finite element simulation values, respectively, and the minimum error value 13.07%. It provides a reliable basis for accurately predicting the deformation value of the pressure vessel curing process, and also provides a reference for subsequent experiments to reduce the curing deformation value.

Axisymmetric virtual elements for problems of elasticity and plasticity

AbstractThe virtual element method (VEM) allows discretization of elasticity and plasticity problems with polygons in 2D and polyhedrals in 3D. The polygons (and polyhedrals) can have an arbitrary number of sides and can be concave or convex. These features, among others, are attractive for meshing complex geometries. However, to the author's knowledge axisymmetric virtual elements have not appeared before in the literature. Hence, in this work a novel first order consistent axisymmetric VEM is applied to problems of elasticity and plasticity. The VEM specific implementation details and adjustments needed to solve axisymmetric simulations are presented. Representative benchmark problems including pressure vessels and circular plates are illustrated. Examples also show that problems of near incompressibility are solved successfully. Consequently, this research demonstrates that the axisymmetric VEM formulation successfully solves certain classes of solid mechanics problems. The work concludes with a discussion of results for the current formulation and future research directions.

Construction of design requirements knowledgebase from unstructured design guidelines using natural language processing

In the manufacturing industry, unstructured documents such as design guidelines, regulatory documents, and failure cases are essential for product development. However, due to the large volume and frequent revisions of these documents, designers often find it difficult to keep up to date with the latest content. This study presents a method for analyzing the characteristics of unstructured design guidelines and automatically constructing a knowledgebase of design requirements from them. A knowledgebase is structured data that a computer can understand, and that can be used to assist designers in the design process. The knowledgebase is constructed using the sections of the document, including design variables and design requirements. The construction process involves pre-processing the documents, extracting information using natural language processing models, and generating a knowledgebase using predefined rules. A requirements knowledgebase was experimentally constructed from a standard document on the general requirements for the design of pressure vessels (American Society of Mechanical Engineers Section VIII Division 1) using the proposed method. In the experiment, the accuracy of information extraction was 86.3 %, and the generation process took 3 min and 50 s. Thus, the proposed method eliminates the need for specialized training of deep learning models and can be applied to various design guideline documents with simple modifications to the design vocabulary and rules. The knowledgebase has applications in design validation, and is expected to enhance the efficiency of the product development process and contribute to reducing the overall development timeline.

DESIGN AND ANALYSIS OF PRESSURE VESSEL USING DIFFERENT MATERIALS

This project explores the field of Finite Element Analysis (FEA) in relation to pressure vessels that have different head configurations, while ensuring that the cylindrical volume and thickness remain uniform. The project adheres to ASME standards, specifically Section VIII, Division I, and focuses on designing a pressure vessel that can withstand a pressure of 8 bar within a volume of 24 liters. The main objective of using FEA is to identify areas of stress concentration in each head design. In industrial settings, pressure vessels play a crucial role in containing fluids or gases under varying pressures. The choice of head configuration significantly impacts the distribution of stress and the overall structural strength. This project specifically utilizes ANSYS software for static and thermal analyses to compare stress distribution in pressure vessels with flat heads, elliptical heads, and other common head designs. The goal is to identify configurations that exhibit lower stress levels, with a particular emphasis on practical scenarios that favor elliptical heads. Additionally, the project explores finite element modeling techniques to evaluate pressure vessels made from different materials such as Nimonic 80A and SA516 Gr70 under high-stress conditions

Numerical simulation of in-vessel steam explosion for China third-generation PWR

In this study, in order to evaluate the Reactor Pressure Vessel (RPV) integrity under in-vessel steam explosion loads for China third-generation Pressurized Water Reactor (PWR), 2D and 3D numerical simulation of in-vessel steam explosion is conducted using MC3D code. The sensitivity analyses for in-vessel steam explosion are performed, including break area, water temperature, water level, melt temperature, and break height. The results show that the premixing stage cannot cause RPV failure and the possibility of the steam explosion blowing the RPV upper head off is almost non-existent. When the break area increases, the maximum pressure and impulse of the RPV inner wall increase obviously first and then generally decrease slightly. With the increase of water temperature, the maximum pressure and impulse first increase and then decrease. When the water level is higher, the maximum pressure variation is small. When the water level is very low, the maximum pressure decreases. The maximum impulse generally decreases with the decrease of the water level. When the melt temperature exceeds 2850 K, the steam explosion is not sensitive to the melt temperature. With the increase of the break height, the maximum pressure and maximum impulse first increase and then decrease. Furthermore, based on the results of sensitivity analysis, two cases of conservative conditions are selected, and the RPV integrity under in-vessel steam explosion loads for China third-generation PWR is considered. The result shows that the integrity of the RPV can be maintained under the in-vessel steam explosion loads for China third-generation PWR with a large margin. These studies provide some reference to improve the severe accident management strategy in China.

In Situ Changes in Mechanical Properties Based on Gas Saturation Inside Pressure Vessels.

In previous studies, difficulties were encountered in measuring changes within high-pressure vessels owing to limitations such as sensor connectors and sensor failures under high-pressure conditions. In addition, polymer-gas mixtures experience instantaneous gas desorption upon exiting high-pressure vessels owing to pressure differentials, leading to measurement errors. In this study, a device using magnetic sensors was developed to measure the real-time changes in gas-saturated polymers inside pressure vessels. Experiments on polymethyl methacrylate gas adsorption were conducted with parameters including pressure at 5 MPa and temperatures ranging from -20 to 40 °C for 60 and 180 min. It was observed that at -20 °C, the maximum magnetic field force density and deflection were 391.53 μT and 5.83 mm, respectively, whereas at 40 °C, deflection did not occur, with a value of 321.79 μT. Based on gas saturation experiments, a new model for deflection in high-pressure atmospheres is proposed. Additionally, an ANSYS analysis was conducted to predict the changes in Young's modulus based on gas saturation. In previous studies, mechanical properties were measured outside the pressure vessel, resulting in an error due to a pressure difference, while the proposed method is characterized by the ability to directly measure polymer behavior according to gas saturation in high-pressure vessels using a magnetic sensor in real time. Therefore, it is possible to predict polymer behavior, making it easy to control variables in high-pressure polymer processes.

Validation of the added mass effect in the narrow gaps of nuclear reactor pressure vessels

Nuclear reactor pressure vessels (RPVs) must be robust to external environmental excitations such as seismic loads. Precise numerical models that predict the dynamic responses to external loads are crucial for evaluating the safety of RPVs. Notably, in RPVs submerged in reactor coolant, it is necessary to examine the added mass effect of the fluid via fluid-structure interaction (FSI) analysis, employing either an analytical approach or a numerical analysis. The present study focuses on modeling and analyzing the added mass effect in the narrow gaps associated with the dense structural layout in the reactor. In this context, this paper validates analytical and numerical models that accurately describe the added mass effect for two cases: (i) simple concentric cylinders with a narrow gap filled with fluid and (ii) a complex small-scale RPV with narrow gaps also filled with fluid. Initially, the analytical model, employing Lagrange's equation of motion and velocity potential, and the numerical model, utilizing FE modeling in acoustic FSI through ANSYS, were validated through experimental modal testing for the added mass effect in the narrow gap between simple concentric cylinders. The analytical model for the concentric cylinders indicates that the added mass diverges to infinity as the gap approaches zero, which should be examined carefully. Through experiments for the concentric cylinders, the analytical and FEM-based added mass effects were validated with a natural frequency error of 3 %. Subsequently, based on the results for the concentric cylinders, a complex numerical model of the small-scale reactor with complex boundary conditions was developed and cross-validated through corresponding experimental modal testing of the small-scale RPV. The added mass model for the narrow gaps in the RPV was validated by substantial agreement of eight representative modes, as demonstrated by a 5 % natural frequency error.

New test rig for biaxial and plane strain states on uniaxial testing machines

The increasing interest in hydrogen technology and storage systems has also significant influence on material characterization. Storage solutions such as cryo-compressed hydrogen (CcH2) or compressed gaseous hydrogen (CGH2) use high pressure to improve the energy density. The pressurized hydrogen is stored in a pressure vessel. This leads to various strain states in the vessel, which are difficult to reproduce with standard testing equipment, such as a uniaxial testing machine. This contribution presents a new test rig for uniaxial testing machines that is able to generate a biaxial load on a cruciform specimen. A hinged structure converts the uniaxial load into a biaxial load. Different attachments allow both equi-biaxial and plane strain states. In addition, the test rig provides access to both sides of the specimen, extending the possibilities for testing under load, such as optical measurement, specimen cooling or permeability measurement. Finally, experiments show the functionality of the test rig and the desired strain states in the specimen.

Particle filter for fatigue crack growth prediction using SH0 wave on-line monitoring

Fatigue crack is one of the main failure modes of pressure vessels. Online monitoring and predicting methods of crack growth play an important role in the operation of important pressure vessel. The SH0 wave is non-dispersive, and it is not disturbed by internal media of pressure vessel and very sensitive to cracks, therefore it is suitable for fatigue crack growth monitoring. Moreover, fatigue crack growth in industry is affected by material properties, loads, which usually shows some uncertainty. And the particle filter (PF) is well suited to deal with prediction problems affected by uncertainty. Hence, the prediction method of crack growth based on SH0 wave monitoring and PF is proposed (short for SH0-PF). The basic theory of crack monitoring method using SH0 wave is introduced, and the signal feature extraction using the damage index is studied. The state equation characterizing the fatigue crack growth is established by Paris model, and the observation equation is established based on the normalized correlation moment damage index according to monitoring signal using SH0 wave. The prediction reliability of the fatigue crack growth applying SH0-PF is verified by experiment with the single edge notched specimen. The experimental results indicate that the prediction accuracy of SH0-PF is better than that of the traditional Paris model.

Compact cryogenic hydrogen test environment for small devices and material characterization

Currently, there is a great need for testing capabilities for material samples and components in LH2. This includes low temperature compatibility at 20 K, H2 compatibility and potential degradation or permeation effects. The test environment required for this is challenging and quite costly due to LH2 supply. Therefore, an alternative test concept was developed whereby the required amount of LH2 (typically 2–3 L) is generated directly on-site by simple condensation. This is achieved with a power-controlled cryocooler (115 W @ 80 K, 18 W @ 20 K). A cylindrical pressure vessel with an inner diameter of d = 109 mm and a length of approx. 500 mm designed for 2.1 MPa is used to hold the LH2 bath and the samples. The cryocooler and the sample chamber are installed in a common vacuum cryostat and are thermally coupled at the lower end. At the 20 K level, thermal coupling is achieved by a sophisticated thermosiphon arrangement. Hydrogen is taken from a pressure reservoir, pre-cooled at the cryocooler 80 K level, and then injected and liquefied within a couple of hours.

Free-field three-transducer spherical-wave reciprocity calibration for hydrophone at hydrostatic pressure of 10 MPa

Free-field three-transducer spherical-wave reciprocity method has been reviewed and employed to calibrate the hydrophone of TC4033 in a high hydrostatic pressure vessel. To reduce the measurement uncertainty, a reciprocal calibration bracket and reciprocal transducers were designed and developed. The calibration bracket can locate the transducers in the high hydrostatic pressure vessel. The reciprocal transducer can reduce the errors caused by the deviation of reciprocity. A correcting sensitivity method based on complex electrical impedance measurement has been described, which can obtain the original open-circuit sensitivity of a hydrophone. It is more accurate than correcting method based on the measurement of extension cable capacitance especially near the resonant frequency range. The TC 4033 hydrophone was calibrated in the one-third octave frequency points from 2 kHz to 200 kHz at a high hydrostatic pressure of 10 MPa. The calibration results were analyzed, and the measurement uncertainty was estimated to be 0.5 dB (k=2).

A Study on the Microstructure and Mechanical Properties of Electron Beam Welds of SA508 Gr.3 Cl.1 steel with Different Heat Treatment conditions for Small Modular Reactor

Electron beam welding was conducted on SA508 Gr.3 Cl.1 steel, which is being considered as a material used in the pressure vessel steel of small modular reactors. The characteristics of the welds were analyzed under various heat treatment conditions. The heat treatment conditions were categorized as as-welded, post weld heat treatment(PWHT), quality heat treatment(QHT), and their features were examined and compared through cross-sectional structure and composition analyses, as well as mechanical property tests. The electron beam welded joints displayed no defects, including pores or cracks. weld metal of the as-welded specimen revealed a needle-type martensite with high hardness, whereas the base metal was characterized by tempered bainite. The weld cross-section bead of the QHT specimen exhibited no significant difference in microstructure compared to the base metal. Tensile testing revealed that both the as-welded and PWHT specimens fractured at the base metal, whereas the QHT specimen fractured at the weld metal. The PWHT specimens showed enhanced impact values in the welds compared to the as-welded specimens. In the QHT specimens, both the base metal and the weld metal demonstrated similarly favorable impact values, approximately 200 Joules. It is evident that post-welding heat treatment improves the toughness value, and quality heat treatment can result in the weld metal being similar to the base metal.

Hot-tube spinning process for manufacturing ultra-high pressure vessels (Type-I): process planning and implementation

Hot-tube spinning process for manufacturing ultra-high pressure vessels (Type-I): process planning and implementation