Typical Pressure Vessel Research Articles

Complex design and analysis of filament wound composite pressure vessels using data driven evolutionary algorithms

The typical composite pressure vessel manufactured by means of filament winding consists of three elementary construction parts, that is, cylindrical part, end dome and the junction between its cylindrical part and the end dome which are subject of this article. The pressure vessel may fail in each of these three parts. Therefore, all of them must be considered during the design process. This study shows the possible way how to design an optimal pressure vessel related to chosen parameters (which can be mass of the pressure vessel, depth of the end dome, magnitude of internal pressure etc.), so that it does not fail in any construction parts. Any decision, whether the pressure vessel comply or not in studied places, is based on Hoffman's failure index analysis. The finding of an optimal solution requires performing a multi-objective optimization task, which was solved here using data-driven evolutionary algorithms. From the input data, which were generated through analytical approaches, surrogate models were created using the Evolutionary Deep Neural Nets (EvoDN2). These surrogate models were further used as an input to the optimization module which is based upon Constrained Reference Vector Evolutionary Algorithm (cRVEA). The results show that the pressure vessel designed in this way comply in each analyzed location. Moreover, it also finds the most stressed location, which can be useful for the designers.

Stress relief simulation for post-weld heat treatment process of pressure equipment: Creep constitutive equation considering temperature and stress variations

Due to the limited testing methods and high costs, researches on the evolution law of residual stress in the post-weld heat treatment (PWHT) process of pressure equipment are mainly by numerical simulation, in which the selection of a reasonable and reliable creep constitutive model is crucial to ensure the accuracy of numerical predictions. It is worth noting that the temperature changes and residual stress variation during the heat treatment process result in the following creep characteristics: the creep occurs under different temperatures during the heat treatment processes of heating, holding, and cooling; the creep occurs under different residual stress level where the residual stress varies during the heat treatment stages. Thus, to accurately simulate the stress release behavior during the PWHT process, the proper creep constitutive model must involve the influences of the temperature and the stress state. Meanwhile, current heat treatment simulation usually adopts simplified qualitative approaches, and the creep constitutive models often ignore the physical mechanisms and characteristics of actual creep processes, such as the Norton, the Norton-Bailey, and the Omega models. As a result, the accuracy of heat treatment simulation is limited. In this paper, a new creep constitutive relation under varying temperature and stress is proposed. The hyperbolic-sinusoidal function is used to represent the complete three stages of creep, which compensate the inaccuracy prediction at the first and the third creep stages. Moreover, the Arrhenius function is introduced to characterize the creep response under varying temperature conditions, which enables the prediction of residual stress evolution throughout the entire heating-holding-cooling process of heat treatment. Then, a typical pressure vessel cylindrical circumferential weld is simulated. The stress release during the heat treatment is calculated, and the efficacy of the proposed model is validated through surface residual stress testing. It is found that the creep behavior is a crucial factor in numerical simulation of heat treatment, and the creep constitutive relation can significantly affect the accuracy of heat treatment simulation. The simulation utilizing the hyperbolic-sinusoidal temperature-dependent creep model is much more accurate compared to the classical simulation. The simulation results are much more consistent to the experimental results. Specifically, the traditional model often underestimates the stress state, the residual stress drops abruptly during the heating stage. The residual stress evolution mechanism is simulated using the new model: The majority of residual stress are released during the heating process which primarily relies on the creep strain transformation (contributes up to 85%). The stress state does not change during the holding stage and slight higher at the cooling stage.

Development of pressure-temperature limit curves considering unified constraint for reactor pressure vessel

In this work, the pressure-temperature (P-T) limit curves considering unified constraint for a typical large-sized reactor pressure vessel (RPV) with axial surface cracks have been investigated and developed based on the KJ-Ad* two-parameter and the Master Curve (MC) method. The ASME fracture toughness KIc curve and the MC with and without considering unified constraint for irradiated RPV steel were used in the constructions of the P-T limit curves. The effects of crack sizes (constraint levels) and fracture toughness curves on the P-T limit curves have been analyzed for the RPV under heatup and cooldown conditions. The results further show that the P-T limit curves based on traditional ASME KIc curve has the highest degree of conservatism and the use of the MC method can significantly increase the safety margin of P-T limit curves. With increasing crack sizes (increasing constraint levels), the safety region in P-T limit curves reduces, which may lead to the decrease of operating flexibility for nuclear power plants. The accuracy of the P-T limit curves can be improved by considering unified constraint. For smaller size cracks with lower constraint in the RPV, the consideration of constraint can reduce conservatism of the P-T limit curves, and for larger size cracks with higher constraint, it can avoid the non-conservatism. It is recommended to obtain more accurate P-T limit curves based on the MC with considering unified constraint and finite element analysis for RPVs under various operating conditions.

The Study on Fatigue Crack Growth Rate of 4130X Material under Different Hydrogen Corrosion Conditions.

In this paper, the fatigue crack growth rates of typical pressure vessel material 4130X under different corrosion conditions are investigated, and the effects of corrosion modes and loading frequency on the fatigue crack growth rate of 4130X are discussed. The results show that under the same loading conditions, the pre-corroded crack propagation rate is increased by 1.26 times compared with the uncorroded specimens. The plastic deformation mechanism of the crack tip in air is dominated by phase transformation but the hydrogen introduced by pre-corrosion causes a small number of dislocations at the crack tip. The crack growth rate obtained by corrosion fatigue is four times that of the uncorroded specimen, and the fracture surface shows a strong corrosion effect. The molecular dynamics simulation shows that the hydrogen atoms accumulated at the crack tip make the plastic deformation mechanism dominated by dislocation in the crack propagation process, and the coupling interaction between low frequency and the corrosion environment aggravates the hydrogen embrittlement of the crack tip. In the air condition, the loading frequency has no obvious effect on the crack growth rate: when the frequency decreases from 100 Hz to 0.01 Hz and other conditions remain unchanged, the fatigue crack growth rate increases by 1.5 times. The parameter n in the Paris expression is mainly influenced by frequency. The molecular dynamics simulation shows that low frequency promotes crack tip propagation.

Numerical Study on Fracture Behavior of Printed Circuit Heat Exchanger Core Based on Elasto-Plastic Phase Field Method

Abstract Printed circuit heat exchanger (PCHE) is a type of compact heat exchanger with high thermal efficiency, more compact, and suitable for high pressure and high temperature conditions. The safety assessment of PCHE is very important, especially for PCHE core. Because PHCE core is different from the PCHE headers which are typical pressure vessel components. However, there is no standard design method to ensure the structural integrity for PCHE core. Some failure modes of PCHE core are studied in recent years, but seldom researches have been conducted concerning the fracture behavior of PCHE core. In addition, the phase field method for fracture has developed rapidly in recent years with its advantages in predicting crack initiation, bifurcation, and merging. In this work, the fracture behavior of PCHE core with and without defects is investigated based on elasto-plastic phase field method. The model parameter of Ni-based Alloy for elasto-plastic phase field method is first calibrated by comparing the numerical results with tensile test data of diffusion-bonded PHCE core specimen. Then, the influence of loading directions, defect locations, and defect sizes on the fracture behavior of PCHE core with semicircular and semicircular-rectangular channels are analyzed. Some conclusions are discussed.

Prediction of mechanical properties for typical pressure vessel steels by small punch test combined with machine learning

To understand the fitness of different machine learning methods to small punch test (SPT), three machine learning methods, namely, back propagation (BP) neural network, radial basis function (RBF) neural network and random forest (RF) regression model were used to establish machine learning-based correlation models of SPT load–displacement and uniaxial tensile test true stress–strain curves. Five typical pressure vessel steels were tested to reveal the prediction accuracies of different machine learning methods. Statistical analysis, unveiled the following order of prediction accuracy for pressure vessel steels: BP > RBF > RF. However, the differences in the mean absolute percentage erros between BP and RF decreased from 5.64% to 1.59%, with the training data volume increasing from 50 data sets to 629 data sets. Therefore, if a large training data volume is used, then the three machine learning methods can provide acceptable prediction results. However, if the training data volume is insufficient, then the BP, and RBF neural networks are better choices.

Integrity assessment considering unified constraint for reactor pressure vessel under pressurized thermal shock

The integrity assessment methodology based on a new unified constraint parameter Ad* and the Master Curve has been investigated for a typical Chinese reactor pressure vessel (RPV) containing axial surface cracks subjected to pressurized thermal shock (PTS). The thermal–mechanical analysis was carried out under two different PTS transients using finite element method. The integrity assessment has been conducted by comparing the KJ-T curve and KJc-T curve (KJ is elastic–plastic stress integrity, KJc is fracture toughness and T is the crack-tip temperature), and the safety margin was quantitatively analyzed. The results show that the Ad* value does not change with temperature and loads (thermal load and internal pressure load) during PTS due to its load and material independences, and which facilitates the constraint analysis for a RPV under PTS. For smaller size surface cracks usually occurring in the RPV, the integrity assessment considering unified constraint under PTS can reduce excessive conservatism of traditional assessment method. The safety margin of integrity assessment is mainly influenced by constraint levels, PTS transients and fracture toughness of irradiation materials, and methods for increasing safety margin are discussed.

Design and Analysis of a Typical Vertical Pressure Vessel Using ASME Code and FEA Technique

This study aims to address the hazards associated with the design and manufacture of pressure vessels used for storing dangerous liquids, specifically focusing on the increased demand for liquefied petroleum gas (LPG) worldwide. The construction of more LPG facilities necessitates the implementation of safer pressure vessels to mitigate risks such as explosions and leakage. The primary objective of this project is to design a vertical pressure vessel, in accordance with the American Society of Mechanical Engineers (ASME) code, capable of safely storing 10 m3 of pressurised LPG. To ensure the safety of the pressure vessel, the researchers employed Autodesk Inventor Professional 2023 for geometric modelling and utilised Inventor Nastran for finite element analysis (FEA) to investigate displacements, deflections, and von Mises stresses. The vessel is cylindrical in shape and features two elliptical heads, two nozzles, a manway, and four leg supports. The FEA analysis conducted using Autodesk Inventor Nastran enabled the researchers to identify areas where structural modifications were necessary to reduce stress within the vessel. The results revealed an inverse relationship between the displacement and the tank section shell thickness. Additionally, the factor of safety exhibited a linear increase as the shell thickness increased. The researchers carefully considered permissible pressures and determined the required wall thickness to maintain acceptable maximum stresses. The findings indicate that the design of the pressure vessel is safe from failure. Among the components, the manway experiences the highest stresses, followed by the shell, while the heads, nozzles, and leg supports experience lower stresses. The researchers also conducted theoretical calculations for the entire model and ensured that the results fell within acceptable limits, further validating their design approach. The research emphasised the importance of designing pressure vessels in compliance with ASME codes to ensure safety and prevent hazards associated with improper design and manufacturing. The combination of Autodesk Inventor Professional and Inventor Nastran proved to be an effective approach for simulating and evaluating the performance of the pressure vessel. Through the analysis, the researchers found that changes to the pressure vessel structure were necessary to reduce stress. They observed an inverse relationship between displacement and tank section shell thickness, while the factor of safety increased linearly with shell thickness. Stress distribution analysis revealed that the manway and shell experienced the highest stresses, while the heads, nozzles, and leg support exhibited lower stresses. Employing the finite element method, potential stress points within the pressure vessel were identified, enabling necessary modifications to enhance its safety.

Improvement of integrity management for pressure vessels based on risk assessment - A natural gas separator case study

The process of oil and gas processing plant is complex, the types of pressure vessels are rich, and the functions are critical. However, the working medium is mostly untreated medium, and the hazard factors are complex, which poses a threat to the safe production of oil and gas processing plant. Based on PDCA cycle, this paper establishes a six-step links of integrity management for sustainable improvement of pressure vessels. The typical failure modes of pressure vessels are determined, and the fishbone diagram of risk factors under each failure mode is compiled. Risk quantification and classification of pressure vessels based on failure modes (RBFM) is innovatively proposed. Avoiding incalculable failure frequency index, the process quantification of failure possibility is formed according to the development of hazard factors. A failure consequence calculation model based on the leakage affected area was established. Combined with the failure probability level and risk level, the hierarchical inspection strategy for pressure vessels under different failure modes is established. Finally, the method is applied to the natural gas separator of H processing plant. The research results show that RBFM proposed in this paper can meet the requirements for rapid and accurate risk assessment of pressure vessels in oil and gas processing plant. This paper establishes a safe production barrier for the pressure vessel and improves the intrinsic safety of the equipment.

Assessment of the influence of scaling on turbulent mixing in downcomer and core-inlet flow distribution

In the present article, Computational Fluid Dynamics (CFD) simulations are used to assess the effects of classical scaling approaches on turbulent mixing in the downcomer and core-inlet regions of typical Reactor Pressure Vessels (RPVs), applying validated CFD models in two sets of numerical tests. In the first set, simulations of ROCOM Tests 1.1. and 2.2 performed under two different geometric scales showed that the modeling of single-phase flow with mixed convection on a scaled-down geometry is able to provide a very good approximation of the core inlet mixing dynamics in the reference reactor. For the second set, the effects of the selection of global non-dimensional parameters to compare RPVs of varying designs under steady-state operating conditions are studied via the injection of a passive component, and a radial grouping of the mixing scalar is proposed for comparisons involving different core configurations.

Finite Element Analyses of Stresses Developed in Oil Separator Composite Tank Used in Screw Type Compressor Systems

Pressure vessels are geometrically cylindrical, spherical or conical work equipment used for the storage and transportation of pressurized fluid. In the case of design and/or manufacturing deficiency, or for the case of improper applications of such vessels due to working conditions, the damages that may occur can cause serious harm to the environment and employees. The aim of this study is to estimate the performance of a typical oil separator pressure vessel used in screw compressor systems, exposed to high pressure and temperature, using finite element method. Here, the aim is to estimate performance of this tank after modifications in design and to compare the results with that of pressure vessel designed using conventional materials. The inner liner of the separator tank is metal material and the other layers are wrapped with three different composite materials, including carbon fiber/epoxy, glass fiber/epoxy and kevlar fiber/epoxy, at different angles, and then were exposed to high pressures in the environment of finite element simulation software. As a result of the study, stress and deformation values were examined and the most suitable material and orientation angle for the composite pressure vessel were decided.

The Effect of Pressure and Temperature of Residual Life on Separator as Types of Pressure Vessel in “Z” Oil and Gas Field

Field Z is a mature oil and gas field with several production facilities that have passed their service life design, re-assessment of service life for the critical equipment is needed to carry out. This study focuses on identifying the damage mechanism, determining the residual life assessment, and assessing the effect of pressure and temperature on the residual service life of four separators in field Z. The approach is to recalculate the maximum allowable pressure and the minimum thickness of the separator, estimates the corrosion rate using API 510 and API 581, and estimates the residual life assessment of the separator. The result shows that estimation of corrosion rate with API 581 provide lower value than API 510 due to different methodology. However, the result prove that the operating pressure and temperature of separator will affect to the residual life through minimum thickness and corrosion rate, respectively. The higher operating temperature, the higher corrosion rate. Both of these will reduce the residual life. The calculation estimates that at current operation condition, three of four separators in field Z still can be utilize d at least until next five years. While one separator needs to replace immediately considering to the negative remaining service life.

Investigation of the Effect of Solid Wire and Flux Combinations Used in Submerged Arc Welding of the LPG Cylinders on Mechanical Properties

Liquefied petroleum gas (LPG) cylinder is a type of pressure vessel that used to store and transport liquefied gases. In this study, S460MC steel with a thickness of 1.50 mm and submerged arc welding method were used in the manufacturing of LPG cylinders. Selection of the welding consumables (wire, flux) and optimization of the welding parameters (current, voltage, travel speed) are the primary focus of the study. Selected welding parameters have been verified as a result of visual and radiographic (X-ray) tests and macroscopic examinations. In order to analyze the effects of welding consumables on mechanical properties, test specimens were prepared, then tensile and hardness tests were performed and it was observed that molybdenum element increased the mechanical strength. In order to fulfill the requirements of the LPG cylinder production standard, bursting & volumetric expansion tests and pressure fatigue tests were performed and the requirements were met.

Experiment and Theoretical Investigation on Fatigue Life Prediction of Fracturing Pumpheads Based on a Novel Stress-Field Intensity Approach

Fracturing pumpheads are typical pressure vessels that experience frequent fatigue failure under the effect of notches in their cross-bore. To enhance the fatigue life of fracturing pumpheads, the study of the notch effect is indispensable and important to establish a reliable mathematical model to predict their fatigue life. In the present paper, two novel fatigue life prediction models are proposed for notched specimens. In these models, two new geometric fatigue failure regions are defined to improve the weight function. Finally, the elaborated novel stress-field intensity approach was applied to three different types of notched specimens. Experiment results indicate that the new SFI approach achieves 47.82%, 39.48%, and 31.85% higher prediction accuracy than the traditional SFI approach, respectively. It was found that the modified SFI approach provided better predictions than the traditional SFI approach and the TCD method. The II-th novel SFI approach had the highest accuracy, and the I-th novel SFI approach was more suitable for sharply notched specimens.

Key parameters governing the ground risk from reentering pressure vessel debris

The present study discusses the state of the art concerning the multitude of aspects contributing to or inhibiting the aerothermal demise of various types of spacecraft pressure vessel designs. The respective impacts of the parent spacecraft's entry trajectory, the structural integration and subsequent separation of the pressure vessel during break-up, the tank's physical characteristics and in-flight aerodynamics are examined. Special attention is given to the role of key material properties governing the surface heating interface and demise behaviors as observed in past and recent experimental activities, such as the surface emissivity and catalysis. The extraction of relevant material properties from ground experiments is outlined and values presented for materials of relevance to typical spacecraft pressure vessel designs.Based on the aggregated findings of this work as well as previous studies, a parametric study of pressure vessel demise is conducted with an emphasis on a realistic representation of heating conditions. The study concludes with a critical assessment of the most notorious issues preventing pressure vessel demise and potential pathways towards their resolution.

INFLUENCE OF SHAPE OF PRESSURE VESSEL SHELL ON BOLT WORKING LOAD AND TIGHTNESS

The area of flange joints with gasket includes many types of pressure vessels, which are mainly defined by the purpose of use and specific load conditions. These differences in definitions caused the existence of many types of pressure vessels with different shell shapes. Calculations of basic shapes are defined by standards. However, in some fields of engineering practice, these shapes are atypical. The article discusses the issue of circular sealed flange joints with a nonstandard shape of the pressure chamber shells. The aim of this article is to describe influence of shape of pressure vessel shell on bolt working load and the final tightness of the sealed joint using FEM.

A numerical approach to design a type II box-shaped pressure vessel with inner tension struts

The use of shared vehicle architectures with BEVs offers a high potential for FCEVs in terms of cost reduction. Therefore, the hydrogen must be stored in the box-shaped design space in the underbody of the vehicles, where the battery in BEVs is located. Box-shaped pressure vessels show the potential to store high amounts of hydrogen in this design space. An optimal design of a type I box-shaped pressure vessel with inner tension struts is investigated in literature. In this study, the relatively low efficiency of this type of pressure vessel is presented first. This motivates to work out the possibilities to increase the efficiency by reducing the total weight. Therefore, a numerical analysis is conducted to reinforce the vessel wall with fiber reinforced composite in the main section of this study. In a first step the possible measures to reinforce the pressure vessel are analyzed and evaluated. Then, a basic design, which serves as a baseline for the numerical studies, is determined analytically. Using a numerical model, the structure of the reinforcement and the acting loads are investigated with finite element method in parametric studies varying several parameters. Based on the knowledge gained, optimal design parameters are derived. These design parameters allow a comparison of the pressure vessel efficiency with other pressure vessel types and enable the evaluation of this vessel concept.

J-resistance curve testing of a pressure vessel steel and a clad pipe girth weld using clamped SE(T) specimens and the normalization method

This work addresses an exploratory application of the normalization method to determine crack growth resistance curves for a typical pressure vessel steel and a clad pipe girth weld using clamped SE(T) specimens. A primary objective is to verify the effectiveness of the methodology in providing accurate descriptions of the ductile properties for the tested materials using clamped SE(T) specimens. Fracture toughness testing conducted on an A285 Gr C pressure vessel steel and a dissimilar Nickel–Chromium girth weld provides the load–displacement data from which J-resistance curves are evaluated on the basis of the normalization procedure. For the tested pressure vessel steel and clad pipe girth weld, the normalization method provides experimental measurements of ductile crack extension in terms of J−Δa curves which are in good agreement with experimentally measured crack growth responses derived from the UC procedure.

Analysis of residual stress and strain in the cylindrical part of the composite pressure vessel with load-sharing metallic liner

As a result of experimental studies of the composite pressure vessel with load-shearing metallic liner during the unloading and cyclic-loading processes, the deformation of structure is nonlinear [1,2]. A method for purpose of describing and analyzing residual stress and strain in the cylindrical part of a composite pressure vessel type 3 after autofrettage is developed, which is based on the linear-elastic model of the fibrous composites and the relations of the theory of plasticity with translational hardening for isotropic material [3]. The theoretical results obtained from constitutive equations are written in matrix form and fit the experimental data well. In comparison, the results based on finite element method and classical Prandtl-Reuss flow rule are proposed. The results show that it is necessary to consider the plastic deformation in metallic liner of composite pressure vessel type 3 when analyzing the stress-strain state.

Effect of step cooling and P-segregation to grain boundaries on the tensile and fracture toughness properties of A533B plate and A508 forging steels

Although available data do not report significant thermal ageing of reactor pressure vessel materials, this should be reconsidered in the perspective of long term operation where exposure time is significantly higher than the available reported experimental data. One of the element that is reported to promote thermal ageing degradation is phosphorus. The thermal ageing embrittlement susceptibility is assessed by submitting reactor pressure vessel steels to a step cooling heat treatment known to induce P-segregation to grain boundaries resulting in intergranular rather than transgranular cleavage fracture. Thermal ageing susceptibility was experimentally assessed on two typical reactor pressure vessel steels with P-content of 0.017% and 0.006%. The experimental data including tensile, Charpy impact and fracture toughness tests, show a very consistent picture of the various mechanical properties. Upon step cooling, intergranular fracture is promoted and P-content has a major effect on the thermal ageing susceptibility. However, quantitative assessment shows that the effects of step cooling on the mechanical properties of both steels in their as received condition are not sufficiently high to induce thermal ageing embrittlement and therefore their susceptibility to thermal ageing is low. Consequently, given the low P-content of most Belgian RPV materials, it can be concluded that they will be not prone to thermal ageing in the perspective of long term operation.