Cylindrical Pressure Vessels Research Articles

The Use of an Equivalent Temperature Field to Emulate an Induced Residual Stress Field in a Rotating Disk Due to Full Or Partial Rotational Autofrettage

Abstract The evaluation of equivalent temperature fields for cylindrical and spherical pressure vessels to imitate autofrettage induced residual stresses has been successfully implemented in studying crack growth in autofrettaged vessels by the finite element method. Rotational autofrettage is a recent method that can be employed for strengthening hollow disks used in many turbomachinery. The evaluation of the equivalent temperature field becomes pivotal in the performance assessment of autofrettaged cracked disks subjected to high rotational speed. In this work, an equivalent thermal loading method for emulating the residual stress field in a hollow rotating disk, induced by full or partial rotational autofrettage in a finite element analysis is suggested. An analytical, or a numerical discrete solution, evaluating the equivalent temperature field for an arbitrary axisymmetric residual stress field, induced in a rotating disk due to rotational autofrettage, is developed. This solution is implemented in a finite element analysis to emulate the original rotational autofrettage induced residual stresses in a typical rotating disk. Applying the equivalent temperature field, the residual stresses obtained in the finite element analysis, are further corroborated with the original residual stress field introduced by rotational autofrettage. It is found that the developed equivalent temperature fields excellently reproduce the residual stress fields, within less than 1%, induced by both full or partial rotational autofrettage.

Two‐threshold control limit policy in condition‐based maintenance

AbstractIn this paper, we consider a component exhibiting a continuous monotone degradation modeled as a Gamma process. The maintenance policy is of condition‐based type with periodic inspections. It follows the two threshold control limit policy with a preventive maintenance limit, a switching limit, and a given failure limit. Our interest is to minimize the annual expected maintenance cost subject to a constraint on the average availability. The decision variables are the preventive limit, the switching limit, and the inspections schedule. We derive exact results for the key performance indicators, but since they are numerically involved, we propose a simple, that is, involving necessary spreadsheet calculations, accurate approximation. We apply our model to a case from the process industry, namely, a carbon steel hydrogen dryer consisting of a cylindrical pressure vessel. This vessel suffers from corrosion with thickness growth modeled as a Gamma process. The optimization results show that although the annual maintenance cost increases with the mean and the coefficient of variation of the yearly corrosion thickness, its mean has a higher impact on cost. Based on the cost sensitivity analysis, we find that the impact of a vast increase of the corrective maintenance cost for the same inspection and preventive costs can be mitigated by appropriately reducing the corrective maintenance probability. Finally, we empirically show that the two threshold policy achieves an annual cost savings up to compared to the single threshold policy.

Stress distribution optimization in dished ends of cylindrical pressure vessels

The standard geometries of dished ends of cylindrical pressure vessels were developed at the beginning of the last century. Among them, there are ellipsoidal and torispherical geometries characterized by disadvantageous stress distribution, which is the primary determinant when designing shell structures. This paper focuses on shape optimization of dished ends with the depth equivalent to the standard ones, with the intent to minimize the maximum von Mises stress in a cylindrical pressure vessel. Referring to the Bézier curve (BC), a unique geometry of arbitrary order is developed to describe the parametric shape of the dished end. The optimization is implemented using two approaches. Initially, the fitness function is obtained analytically through the membrane theory (MT). A deterministic optimization algorithm is adopted to complete the procedure. Further, the optimization method is modified to obtain the fitness function using the finite element method (FEM). To process the solution, a genetic algorithm (GA) is employed. The obtained improvement of stress distribution is compelling while maintaining the manufacturability of the shell structure.

Cylindrical shell pressure vessel profile variation footprint in strain comparison of test data with numerical analysis

The strain comparison of a pressure vessel made of HSLA 15CDV6 in a cylindrical shell membrane region in a pressure test is discussed in this paper. Non-linear finite element analysis (FEA) of thin-walled cylindrical pressure vessels has been carried out using ANSYS. Hoop strain obtained from FEA is not compared well with the pressure test data at the membrane location of the cylindrical shell where the strain gauge is mounted. So to explain the reasons for the difference in strains at the membrane region, the profile of the cylindrical shell at strain gauge region has been measured. The 3D FEA of the cylindrical region with the measured profile is performed. It is found that with measured profile the FEA is giving the strain close to measured strain in the hoop direction. This leads to the increase in strain and stress as having been demonstrated through mathematical modeling in the deviated profiles variations of cylindrical shells. Therefore, the stresses in the deviated region are greater than those that would exist in an undeviated cylindrical shell, which reduces the margin of safety with respect to the yield strength of the material and causes stress concentration. The details of the stress analysis carried out including the effect of measured 3D profile variation are discussed in this paper.

On the assessment of non-metallic inclusions by part 13 of API 579 -1/ASME FFS-1 2016

Improvement of nondestructive inspection techniques has allowed more frequent detection of closely spaced zones of non-metallic inclusions in pressure vessels made of low carbon steel. In the present study, closely spaced inclusions in an in-service cylindrical horizontal pressure vessel were detected by Scan-C ultrasonic inspection and considered as laminations to be assessed by Part 13 of the API 579-1/ASME FFS-1 2016 standard. The outcoming results were considered as a rejection for Level 1 assessment, and a repair or replacement of the component was required, even though it retained a significant remaining strength. Thus, an alternative procedure to assess the mechanical integrity of pressure vessels containing zones of non-metallic inclusions is proposed by adopting some criteria of the API 579-1/ASME FFS-1 Part 13 standard procedure and taking into consideration the dimensions and grouping characteristics of the inclusion zones.

Effect of Graphene Nanoplatelets on Progressive Failure Behavior under Internal Pressure of Composite Cylindrical Pressure Vessels

Effect of Graphene Nanoplatelets on Progressive Failure Behavior under Internal Pressure of Composite Cylindrical Pressure Vessels

Buckling analysis of thin-walled metal liner of cylindrical composite overwrapped pressure vessels with depressions after autofrettage processing

Abstract The cylindrical filament wound composite overwrapped pressure vessels (COPV) with metal liner has been widely used in spaceflight due to their high strength and low weight. After the autofrettage process, the plastic deformation of the metal liner is constrained by composite winding layers, which introduce depressions to the metal liner that causes local buckling. To predict the local buckling of the inner liner with depressions of the pressure vessel after the autofrettage process, a local buckling analysis method for the metal liner of COPV was developed in this article. The finite element method is used to calculate the overall stress distribution in the pressure vessel before and after the autofrettage process, and the influence of local depressions on the buckling is evaluated. The axial buckling of the pressure vessel under external pressure is analyzed. The control equation of the metal liner with depressions is developed, considering the changes in the pressure and the bending moment of the liner depressions and its vicinity during the loading and unloading process. Taking the cylindrical COPV (38 L) with aluminum alloy liner as an example, the effects of liner thickness, liner radius, the thickness-to-diameter ratio, autofrettage pressure, and the length of straight section on the autofrettage process are discussed. The results show that the thickness of the inner liner has the most significant influence on the buckling of the liner, followed by the length of the straight section and the radius of the inner liner, while the autofrettage pressure has the least influence.

A comparison of stress analysis and limit analysis approaches for single and multiple nozzle combinations in cylindrical pressure vessels

The finite element method is the most commonly used approach when solving complex practical cylinder-cylinder junctions in pressure vessels. This is used when the geometrical arrangement is out with the permitted scope of the design-by-rule approaches or when detailed stress information is required as in a fatigue assessment. High-stress concentrations occur on the crotch corner for cylinder-cylinder joints, and it is possible to reach solutions for this problem by using both theoretical and numerical solutions. However, those approaches do not fully overlap nor have the same underlying assumptions. As such, an innovative high-fidelity finite element model has been developed to provide a holistic unified approach which can tackle a wide range of problems. In this study, various detailed nozzle design challenges were investigated including single and multiple nozzle combinations, nozzle-cylinder systems with different size ratios, fillet weld applications, limit loads and external loading cases were analyzed. The results obtained are compared with well-respected calculation methods such as WRC537, and a new approach is presented for the analysis of cylinder-cylinder combinations.

Effect of autofrettage on the ultimate behavior of thick cylindrical pressure vessels

Major applications of thick cylinders are in the defense sector. Stress distributions especially under elastic-plastic conditions are more complex in thick cylinders. Though the cylinder may not be strained to ultimate in service, assessment of factor of safety is essential. Simulating elastic-plastic material behavior of cylinders using the uni-axial test data is more dependable and the finite element analysis (FEA) software has got this capability. A procedure using a suitable material model is demonstrated in this study utilizing the FEA software Ansys. The instability criterion followed in Svensson's pressure expansion relationship is used in the process of FEA. The predicted failure pressure is very close to the literature test data as well as few theories that have been highlighted. Moreover, thick cylinders are mostly subjected to autofrettage in applications like gun barrels to enhance service pressure and fatigue life. Hence it is attempted to simulate the development of residual stress due to autofrettage and its effect on the ultimate behavior on the pressure vessels. The residual stress developed is superimposed on the stresses due to internal pressure which causes the redistribution of stresses throughout the thickness. There is a marginal increase in burst pressure due to autofrettage. Though the effect could be made significant by increasing the autofrettage pressure, it gives detrimental effects on the other side by developing tensile residual stresses on the external surface. Hence, with the permissible extent of autofrettage, the effects are found to be marginal and this knowledge helps assess the safe loading limits.

An Experimental Study of Steam-Solvent Coinjection for Bitumen Recovery Using a Large-Scale Physical Model

Summary In this paper, we present a solvent-assisted steam-assisted gravity drainage (SA-SAGD) experiment with multicomponent solvent (i.e., condensate) using a large physical model. The sandpack for the experiment had a porosity of 0.33 and a permeability of 5.6 darcies in the cylindrical pressure vessel that was 1.22 m in length and 0.425 m in internal diameter. The sandpack was initially saturated with 93% Athabasca bitumen and 7% deionized water. The main objective of this research was to study the in-situ thermal/compositional flow and produced bitumen properties in SA-SAGD with condensate. After the preheating of the sandpack for 24 hours, SA-SAGD with 2.8-mol% condensate was performed at 50 cm3/min (cold-water equivalent) at 3500 kPa for 3 days. The experimental data of production, injection, and temperature distribution were recorded. Also, 10 samples of produced oil were taken and analyzed for density and asphaltene content. The sandpack was excavated after the experiment to analyze the asphaltene content in the remaining oil at different locations. A numerical simulation model was calibrated based on the data of material balance and temperature distribution, and it was validated with properties of the produced and excavated samples. The simulation model used fluid models based on experimental data of viscosities, densities, and bubblepoints for four condensate/bitumen mixtures. Results showed that SA-SAGD was efficient in bitumen recovery with a cumulative steam-to-oil ratio (SOR) that was two to three times smaller than that in SAGD using the same physical model. Detailed analysis of the calibrated simulation model indicated that SA-SAGD enabled the steam chamber to expand more efficiently with a smaller amount of water throughput than SAGD. Volatile solvent components tended to remain in the chamber, and the condensed solvent components acted as a miscible carrier for bitumen components. The analysis further showed that the more efficient oil recovery in SA-SAGD occurred with predominantly cocurrent flow of oil and water near the chamber edge. SA-SAGD recovered a larger amount of asphaltene components (i.e., less in-situ upgrading) than SAGD likely because of its lower chamber temperature, shorter production period, and enhanced local displacement efficiency.

Explosions of Cylindrical Pressure Vessels Subjected to Fire: Probabilistic Prediction of a Number of Fragments

The aim of this study was to propose a procedure for a prediction of the number of fragments generated by fire induced explosions of cylindrical pressure vessels. The prediction is carried out in terms of probabilities of individual fragment numbers. The prevailing numbers of two to four fragments are considered. The fragment number probabilities are estimated by applying data on vessel fragmentations acquired in investigations of past explosion accidents. The pressure vessel explosions known as BLEVEs are considered. The Bayesian analysis is used for the estimation of the fragment number probabilities. This analysis is carried out on the basis of Poisson-gamma model. An approach to developing a gamma prior distribution for the average number of fragments per explosion accident is proposed. The assessment of the fragment number probabilities is carried out by propagating uncertainty related to the average number of fragments to uncertainty in the fragment number probabilities. The stochastic (Monte Carlo) simulation is used for this propagation. Findings of this study are viewed as a possibility to improve the assessment of risk posed by pressure vessel explosions.

Bayesian reasoning aimed at a prediction of failure patterns of fire induced pressure vessel explosions

The problem of assessing damage due to explosions of cylindrical pressure vessels is considered. The attention is focussed on a prediction of the arrangement of cracks in the vessel wall prior to its explosion. This arrangement of cracks is called the failure pattern. It is seen as essential information for forecasting ejection and projection of fragments generated by an explosion. Thermally induced explosions known as boiling liquid expanding vapour explosions are studied. The problem of prediction of failure patterns is formulated as a problem of estimating probabilities of these patterns. The scarcity of data on occurrences of failure patterns in the past explosion accidents was an incentive to estimate the failure pattern probabilities by means of Bayesian statistics. The main finding of the study is that the failure pattern probabilities can be handled within the Dirichlet-multinomial model and the epistemic uncertainty in these probabilities expressed by Dirichlet prior and posterior distributions. The Bayesian estimation of failure pattern probabilities is viewed as a way allowing to introduce the prediction of vessel fragmentation into the formal probabilistic risk analysis. The so-called minimally informative Dirichlet prior distribution is suggested for the probability estimation as a prior suitable to Bayesian updating with scarce data. It is stated that currently the probabilistic prediction of failure patterns on the basis of past accident data is the only practicable way to assess the potential type of vessel fragmentation. A conventional (deterministic) mechanical and/or metallurgical analysis does not provide reliable models for failure pattern prediction in case of explosions under study.

Experimental study of accidental leakage behaviour of liquid CO2 under shipping conditions

CO2 shipping is a viable transport alternative when pipelines are impractical. Lack of experience in large-scale CO2 shipping projects implies uncertainty in selecting optimal cargo conditions and operational safety procedures. The risk of uncontrolled release of CO2 arises in case of mechanical failure of storage or cargo vessels, and a thorough understanding of the discharge phenomena, including the propensity for solid formation, is necessary to develop safety protocols. A refrigerated experimental setup is established in this study to investigate the release phenomena of liquid CO2 under shipping conditions. The rig features a dome-ended cylindrical pressure vessel, a discharge pipe section and a liquid nitrogen refrigeration system that enables conditioning near the triple point – at ∼0.7 MPa, 223 K - and higher liquid pressures (∼2.6 MPa, 263 K). Pressure, temperature and mass monitoring were considered to enable an extensive observation of the leakage behaviour under typical operation scenarios. Three different sets of experiments were considered to inform the designer in the selection of optimal process conditions, with low-pressure (0.7 – 0.94 MPa, 223–228 K), medium-pressure (1.34–1.67 MPa, 234–245 K) and high-pressure tests (1.83–2.65 MPa, 249–259 K) demonstrating distinct behaviours relative to phase transitions, leakage duration and solidification of inventory.

Effect of length in rotational autofrettage of long cylinders with free ends

Thick-walled cylindrical and spherical pressure vessels are often subjected to autofrettage, a process in which the vessel is loaded at the inner wall to cause a partial or complete plastic deformation emanating from the inner wall, followed by unloading. This introduces the beneficial compressive residual stresses in the vicinity of the inner wall. Depending on the type of the loading, there are five different types of autofrettage processes— hydraulic, swage, explosive, thermal and rotational. This article analyzes the rotational autofrettage, in which the cylinder to be autofrettaged is loaded by rotating it about its longitudinal axis. The centrifugal forces cause the required plastic deformation in the cylinder. Hence, when the cylinder is unloaded by bringing it to rest, compressive hoop residual stresses are introduced in the vicinity of its inner wall. When long cylinders are rotated about their axes, the distribution of axial stress changes with length of the cylinder and affects the generation of the residual stresses in the autofrettaged cylinder. This effect is investigated here by a finite element method (FEM) analysis of rotational autofrettage of cylinder made up of A723 gun steel. The FEM analysis using ABAQUS® package reveals the presence of tensile axial residual stresses in the vicinity of the inner wall of the cylinder, which increase with length. The tensile residual stresses can be mitigated by constraining the ends of the cylinder during the rotational autofrettage.

Generation of interaction diagrams of pad-reinforced and non-padded vessel/nozzle structures via employing various plastic collapse techniques

The present research investigates the effect of pad reinforcement on the load-carrying capacities of a thin-walled pressurized cylindrical vessel with a radial nozzle structure. The main objective is to generate the plastic collapse moment boundaries versus a spectrum of steady internal pressures employing various criteria, namely the Plastic Work Curvature (PWC) and the Plastic Work (PW) criteria in addition to the Twice-Elastic-Slope (TES) Method. Initially, a validation study is conducted utilizing the finite element method to determine the out-of-plane (OP) plastic collapse moments utilizing the TES Method concerning two experimentally tested pad-reinforced vessel/nozzle structures. The validation study revealed very good outcomes. A non-padded vessel/nozzle is also analyzed for comparison purposes. The pad reinforcement enormously enhanced both the in-plane and the OP load-carrying capacities. The TES Method displayed a noticeable deficiency in determining the plastic collapse moments for the non-padded structure concerning the late medium to the high internal pressure spectra.

STRUCTURAL THERMAL TRANSIENT NUMERICAL ANALYSIS OF RESIDUAL STRESSES IN CYLINDRICAL PRESSURE VESSELS SUBMITTED TO WELD REPAIR ACCORDING TO STANDARD ASME PCC-2-2015

This paper presents the calculation of residual stresses present in cylindrical pressure vessels subjected to weld repairs using the ASME PCC-2-2015 via numerical multiphysical thermal structural analysis using the finite element method. The methods of analysis of residual stress by numerical analysis are increasingly part of the dynamics of structural integrity in equipment such as pressure vessels, flanges, heat exchangers, in addition to observing the behavior of these stresses in the thermally affected areas due to welding processes. In welding repair, the sleeve is attached to the pressure vessel through two longitudinal welds and two transverse welds. The modeling of the pressure vessel, repair and welding were carried out according to the aforementioned standard. The welding parameters were adopted with what happens in practice, and with that the temperature distribution and heat flow were obtained. The objectives were to analyze the longitudinal, tangential and residual stresses in the regions of the weld, pressure vessel and repair during the welding period, and to verify the behavior of these stresses after the cooling period. This work shows that numerical analysis can be used efficiently and objectively in situations of control and knowledge of the structural integrity of equipment.

Analysis of cylindrical pressure vessels with dissimilar ends and material comparison

The current work deals with the methodological study of pressure vessel (Cylindrical or spherical) with different ends or heads. The pressure vessel is designed for 24 L volume and 8 bar pressure vessels are done following ASME standard section VIII, Division I. The thickness of all cylindrical heads is calculated by different formulae and the thickness vary accordingly. However, in this project, the thickness is kept constant irrespective of cylindrical heads or ends to study its effect. FEA is performed to evaluate or study the stress parameters. The software took for Finite Element Analysis (FEA) in Ansys 19.2. Before that, the 3D modelling was done using SolidWorks software. After concluding the better cylindrical end or head for constant thickness, the comparison of the material is made to compare with the current state of the art and find out the better material by analyzing the circumferential stress and longitudinal stress.

Mechanical Design of Slug Catcher

In the upstream oil and gas industry Slug Catcher is a separator to separate heavy liquid hydrocarbons and the gaseous lighter fraction. Slug Catcher is a cylindrical pressure vessel which has a horizontal orientation designed with an internal pressure of 84.37 kg/cm2 , 73,89 °C temperature, 3 mm corrosion allowance, 3,500 mm length, and 1,750 mm diameter. This paper aims to design a Slug Catcher from a mechanical side that is safe and able to withstand the stress caused by internal pressure. General design which includes calculation of thickness of shell, heads, and nozzles, maximum allowable working pressure (MAWP), and minimum design metal temperature (MDMT) using ASME BPVC Section VIII Division 1. Based on the results obtained the nominal shell thickness is 60 mm, head minimum thickness 58 mm, material specification for shell and head is SA 516 Gr 70. In general, the selected material use low carbon steel; flange rating class 600; vessel’s Maximum Allowable Working Pressure is 87.60 kg/cm2 ; hydrostatic test pressure is 113 kg/cm2 .

Lockhart with a twist: Modelling cellulose microfibril deposition and reorientation reveals twisting plant cell growth mechanisms

Plant morphology emerges from cellular growth and structure. The turgor-driven diffuse growth of a cell can be highly anisotropic: significant longitudinally and negligible radially. Such anisotropy is ensured by cellulose microfibrils (CMF) reinforcing the cell wall in the hoop direction. To maintain the cell’s integrity during growth, new wall material including CMF must be continually deposited. We develop a mathematical model representing the cell as a cylindrical pressure vessel and the cell wall as a fibre-reinforced viscous sheet, explicitly including the mechano-sensitive angle of CMF deposition. The model incorporates interactions between turgor, external forces, CMF reorientation during wall extension, and matrix stiffening. Using the model, we reinterpret some recent experimental findings, and reexamine the popular hypothesis of CMF/microtubule alignment. We explore how the handedness of twisting cell growth depends on external torque and intrinsic wall properties, and find that cells twist left-handedly ‘by default’ in some suitable sense. Overall, this study provides a unified mechanical framework for understanding left- and right-handed twist-growth as seen in many plants.

Design and strength estimation of composite multi-cavity pressure vessels

The article discusses a layer-by-layer method for calculating of composite products, and the “thread analogy” is provided for pressure vessels calculating. Stress fields at the multi-cavity cylindrical and spherical pressure vessels are calculated using FEM. Gas injection system is designed.