Cylindrical Pressure Vessels Research Articles

Three-Dimensional Stress Analysis for Semi-Elliptical Cracks in the Connection of Cylinder-Hemispherical Head for Thick-Walled Cylindrical Pressure Vessels

These pressure vessels are made by different type of heads. One of them is hemi-spherical head. The area of geometrical discontinuity, like the connection of the cylinder to its hemi-spherical head, are the most susceptible areas for crack initiation along their welds. So it is worthwhile to consider cracks located at this connection. The purpose of this article is to investigate the effect of variation of stress field and geometry of problem on distribution of Stress Intensity Factor (SIF) for a semi-elliptical surface crack which is located at the connection of cylinder to its hemispherical head. The three dimensional finite element analysis is performed by employing singular elements along the crack front. The ratio of crack depth to crack length (a/c) ranged from 0.3 to 1.2; the ratio of crack depth to wall thickness (a/t) ranged from 0.2 to 0.8; and the cylinder geometry parameter of vessel ranged from 1.2 to 2. For better comparison the results are normalized and reported in non-dimensional formats. The results show that the crack configuration, vessel thickness and radius have significant influence on the stress intensity factor distribution along the crack front. Also For a fixed and the maximum value of SIF occur in the cylindrical part and approximately near the deepest point of crack; not on the deepest point of crack depth and this may be due to changing stress field in this connection. The stress intensity factors are presented in suitable curves for various geometrical configurations providing useful tool for the fracture mechanics design of cracked pressure vessels.

Predicting the ejection velocities of fragments from explosions cylindrical pressure vessels: Uncertainty and sensitivity analysis

The purpose of this study was a refinement of knowledge on predicting the ejection velocities of fragments generated by explosions of cylindrical horizontal pressure vessels. A procedure is proposed for assessing these velocities by means of the stochastic simulation. The procedure is used to quantify uncertainties related to the ejection velocities and to carry out a simulation-based sensitivity analysis. The main finding is that the currently available information on phenomena related to the vessel fragmentation is sparse and, therefore, predicting ejection velocities will require a substantial amount of subjective judgement. It was found that ejection velocities are functions of a relatively large number of random input variables, many of which must be modelled subjectively. The study revealed also the need to choose subjectively between several alternative mathematical models used to specify input variables that influence the ejection velocities. The most critical choice must be made between several models used for an assessment of the energy liberated during vessel explosions. Results of the sensitivity analysis indicate that the ejection velocities are influenced mainly by input variables used to express energies involved in the prediction problem. Increased sensitivity to filling ratio of a two-phase pressure vessel was also detected. Results of the study can be used for an improvement of estimation of fragment impact probabilities and design of protective barriers that are built close to the pressure vessels posing explosion hazard.

Numerical Analysis of Filament Wound Cylindrical Composite Pressure Vessels Accounting for Variable Dome Contour

In this work, the stress distribution along cylindrical composite pressure vessels with different dome geometries is investigated. The dome contours are generated through an integral method based on shell stresses. Here, the influence of each dome contour on the stress distribution at the interface of the dome-cylinder is evaluated. At first, the integral formulation for dome curve generation is presented and solved for the different dome contours. An analytical approach for the calculation of the secondary stresses in a cylindrical pressure vessel is introduced. For the analysis, three different cases were investigated: (i) a polymer liner; (ii) a single layer of carbon-epoxy composite wrapped on a polymer liner; and (iii) multilayer carbon-epoxy pressure vessel. Accounting for nonlinear geometry is seen to have an effect on the stress distribution on the pressure vessel, also on the isotropic liner. Significant secondary stresses were observed at the dome-cylinder interface and they reach a maximum at a specific distance from the interface. A discussion on the trend in these stresses is presented. The numerical results are compared with the experimental results of the multilayer pressure vessel. It is observed that the secondary stresses present in the vicinity of the dome-cylinder interface has a significant effect on the failure mechanism, especially for thick walled cylindrical composite pressure vessel. It is critical that these secondary stresses are directly accounted for in the initial design phase.

Evaluation of structural responses of natural fibre reinforced composite plates and pressure vessels

The present work discusses the bending, buckling and free vibration of natural fibre reinforced composite (NFC) plates initially. Numerical formulation is done based on higher order shear deformation theory and programming in Matlab environment is performed. The results for NFC plates are presented for several parametric variations. Finally, as an application of NFC panels, the cylindrical pressure vessel structure is analysed by considering flax-epoxy as inner laminate layers in combination with carbon-epoxy as outer laminate layers. The deformation and stress values are presented for various load conditions on the NFC pressure vessel.

Thermoelastoplastic response of FGM linearly hardening rotating thick cylindrical pressure vessels

An analytical solution is presented to analyze the thermoelastoplastic response of a rotating thick-walled cylindrical pressure vessel made of functionally graded material (FGM). The analysis is based on Tresca's yield condition, its associated flow rule and linear strain hardening material behaviour. The uncoupled theory of thermoelasticity is used, and the plane strain condition is assumed. The material properties except for Poisson's ratio, are assumed to vary nonlinearly in the radial direction. Elastic, partially plastic, fully plastic, and residual stress states are investigated. The heat conduction equation for the one-dimensional problem in cylindrical coordinates is used to obtain temperature distribution in the vessel. It is assumed that‏ the inner surface is exposed to an airstream and that the outer surface is exposed to a uniform heat flux. Tresca's yield criterion and its associated flow rule are used to formulate six different plastic regions for a linearly hardening‏ condition. All these stages are studied in detail. It is shown that the thermoelastoplastic stress response of a rotating FGM pressure vessel is affected significantly by the nonhomogeneity of the material and temperature gradient. The results are validated with those of other researchers for appropriate values of the system parameters and excellent agreement is observed.

Experimental Research on Rapid Localization of Acoustic Source in a Cylindrical Shell Structure without Knowledge of the Velocity Profile.

Acoustic source localization in a large pressure vessel or a storage tank-type cylindrical structure is important in preventing structural failure. However, this can be challenging, especially for cylindrical pressure vessels and tanks that are made of anisotropic materials. The large area of the cylindrical structure often requires a substantial number of sensors to locate the acoustic source. This paper first applies conventional acoustic source localization techniques developed for the isotropic, flat plate-type structures to cylindrical structures. The experimental results show that the conventional acoustic source localization technique is not very accurate for source localization on cylindrical container surfaces. Then, the L-shaped sensor cluster technique is applied to the cylindrical surface of the pressure vessel, and the experimental results prove the applicability of using this technique. Finally, the arbitrary triangle-shaped sensor clusters are attached to the surface of the cylindrical structure to locate the acoustic source. The experimental results show that the two acoustic source localization techniques using sensor clusters can be used to monitor the location of acoustic sources on the surface of anisotropic cylindrical vessels, using a small number of sensors. The arbitrarily triangle-shaped sensors can be arbitrarily placed in a cluster on the surface of the cylindrical vessel. The results presented in this paper provide a theoretical and experimental basis for the surface acoustic source localization method for a cylindrical pressure vessel and lay a theoretical foundation for its application.

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

Improvement of nondestructive inspection techniques has made more frequent the detection of zones containing 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 of 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 with by adequation of some criteria of the API 579-1/ASME FFS-1 Part 13 standard procedure, taking into consideration the dimensioning and grouping characteristics of the inclusion zones, providing more reasonable results.

Acoustic pressure oscillation effects on mean burning rates of plateau propellants

• Influence of acoustic pressure oscillations on mean burning rates of plateau propellants. • Non-aluminized and aluminized propellants exhibit plateau burning trends are examined with corresponding matrixes. • Magnitudes of imposed acoustic amplitudes are varied from 0.1% to 1.4% with respect to mean chamber pressure conditions. • Both non - aluminized propellants and aluminized propellants show significant enhancement in the mean burning rate due to the fluctuations imposed by acoustic pressure amplitudes and frequencies on the propellant combustion. • Maximum burning rate augmentation factors of non-aluminized and aluminized are 1.27 and 1.47 respectively. Combustion instabilities constitute a well pronounced problem in all large rocket motors due to the inherent acoustic pressure oscillations established based on the port geometries. Suppression of the combustion instabilities in the solid rocket motor is required for controlling the mean burning rate variation which arises due to the interaction of acoustic pressure wave with propellant combustion. An experimental study has been carried out to investigate the effects of acoustic pressure oscillations on mean burning rates of non-aluminized and aluminized propellants which exhibit low pressure exponent index (n) in the burning rate trends. Steady and unsteady mean burning rates are determined from combustion photography method using a window bomb test facility over the pressure range of 17 MPa. A rotary valve is coupled with the window bomb setup to generate acoustic pressure oscillations inside the test chamber (cylindrical pressure vessel), which imposes the required frequencies of 140, 180 and 240 Hz respectively. The acoustic pressure amplitudes are varied from 0.04% to 1.4% of the mean chamber pressure. Both non-aluminized propellants and aluminized propellants have shown significant enhancement in the mean burning rate due to the fluctuations imposed by acoustic pressure amplitudes and frequencies on the propellant combustion. The enhancement in the mean burning rate also depends upon dynamic response of the flame to the excited frequencies and acoustic pressure amplitudes. The plateau burning behaviour of the non-aluminized propellant is completely distorted whereas it is retained in aluminized compositions. Conversely, it also shifts the mean pressure range of plateau burning rate trend. The maximum burning rate augmentation factors resulted from imposed acoustic pressure wave on non-aluminized and aluminized propellants are observed as 1.27 and 1.47 respectively.

Cortical tension overrides geometrical cues to orient microtubules in confined protoplasts

In plant cells, cortical microtubules (CMTs) generally control morphogenesis by guiding cellulose synthesis. CMT alignment has been proposed to depend on geometrical cues, with microtubules aligning with the cell long axis in silico and in vitro. Yet, CMTs are usually transverse in vivo, i.e., along predicted maximal tension, which is transverse for cylindrical pressurized vessels. Here, we adapted a microwell setup to test these predictions in a single-cell system. We confined protoplasts laterally to impose a curvature ratio and modulated pressurization through osmotic changes. We find that CMTs can be longitudinal or transverse in wallless protoplasts and that the switch in CMT orientation depends on pressurization. In particular, longitudinal CMTs become transverse when cortical tension increases. This explains the dual behavior of CMTs in planta: CMTs become longitudinal when stress levels become low, while stable transverse CMT alignments in tissues result from their autonomous response to tensile stress fluctuations.

Revisiting classic problems of exact solutions for stresses in functionally graded pressure vessels

In 2001, Naki Tutuncu and Murat Ozturk obtained analytical solutions for stress distribution of functionally graded material (FGM) cylindrical and spherical pressure vessels [COMPOS. PART. B-ENG, 32(8):683–686 (2001)]. The previous paper belongs to the classical study of elastic mechanics analysis of FGM, but their analytical expressions for the circumferential stress have some errors. The present letter corrects some analytical solutions in the classic problems of exact solutions for stresses in functionally graded pressure vessels. We prove correctness of the proposed analytical solutions by comparing with classical theory and finite element results.

An Experimental Study of Steam-Assisted Gravity Drainage

Summary In this paper we present a large-scale experimental study of the compositional effect on produced bitumen properties in steam-assisted gravity drainage (SAGD). The SAGD experiment used a sandpack in the cylindrical pressure vessel that was 1.22 m in length and 0.425 m in internal diameter. The pore volume of the sandpack was 58 L, and the porosity and permeability were 0.33 and 5.5 darcy, respectively. The sandpack was initially saturated with 93% bitumen and 7% deionized water. The SAGD experiment after preheating was operated mostly at a steam injection rate of 35 cm3/min (cold-water equivalent) at 3,600 kPa (244°C). The produced fluids (gas, oil, and water) were analyzed; for example, 10 oil samples were analyzed in terms of carbon number distribution (CND), the asphaltene content, density, and viscosity to investigate the compositional change of the produced bitumen. After the experiment, the sandpack was excavated, and samples were taken for analysis of solid, water, oil, asphaltene, and sulfur contents. Experimental data (e.g., propagation of a steam chamber and production of oil and water) were history matched using a numerical reservoir simulator. The produced bitumen was lighter and contained 1- to 5-wt% less asphaltenes than the original bitumen. Also, the remaining oil inside the steam chamber contained 6-wt% more asphaltenes. As a result, the produced bitumen was 1- to 6-kg/m3 less dense than the original bitumen. This is an increase in API gravity from the original 7.9° to 8.6°. In the actual operations, bitumen is diluted with condensate to decrease the oil viscosity for pipeline shipping. This decrease in bitumen density corresponds to a decrease of the diluent cost by 5 to 10%. The produced bitumen became less dense with increasing steam-chamber volume. Results were history matched with a simulation model that considers capillary pressures to properly model the mixed flow regimes of oil/water countercurrent and cocurrent flow with an expanding steam chamber. The history-matched simulation indicated that the progressively decreasing density of the produced bitumen can be attributed to the vaporization of the relatively volatile components in the remaining oil and condensation of those components near the chamber edge.

Effect of the Internal Pressure and External Loads on Nozzles in Cylindrical Vessel

Understanding the potential for supporting the maximum loading conditions in the system is a key feature in the design and analysis of pressure vessel applications. This is especially important for thin-walled pressure vessels, when stresses even reaching the initial material yield point could lead to very dangerous situations. Pressure vessels may be subjected to stresses arising from a variety of loading conditions including internal pressure and multiple external loads from attached piping systems. Once the yield point has been exceeded, the structure can accommodate more loading until the plastic zone becomes excessive leading to plastic collapse. This can be challenging to establish especially when external loads act in tandem with internal pressure. Therefore, this paper develops a finite element method for the limit load analysis of a single-nozzle cylindrical pressure vessel under internal pressure and external loading in a variety of combinations. Thereafter, a parametric study is presented covering various loading conditions, both singly and in combination. Finally, a comparison is made shown the interaction effects of the effects on the limit load for changes in vessel geometry and appropriate conclusions drawn.

\u201cN\u201d-shaped Y/X coda spectral ratio observed for in-line-type OBS networks; S-net and ETMC: interpretation based on natural vibration of pressure vessel

We have identified “N”-shaped Y/X amplitude spectral ratios in S-coda records from a significant number of OBSs (ocean bottom seismometers) belonging to in-line-type ocean bottom networks of S-net and ETMC deployed around the Japan Trench and Sagami Trough, respectively. The “N”-shape reflects a sharp peak and notch at approximately 5–13 Hz and 10–23 Hz, respectively. This shape does not characterize OBSs belonging to node-type ocean bottom network of DONET deployed near the Nankai Trough. For S-net stations, the “N”-shape is not clearly formed for stations installed within grooves dug in the seafloor. We interpret the “N”-shaped Y/X amplitude spectral ratio is caused by the natural vibrations of a cylindrical pressure vessel that is placed sideways (long-axis lies in the horizontal plane) on the seafloor. The notch and peak frequencies in the Y/X amplitude spectral ratio likely correspond to natural frequencies of longitudinal (X-direction) and torsional and/or bending (Y-direction) vibrations, respectively. These natural vibrations are not observed for buried OBSs or those installed within grooves in the seafloor probably because they are better coupled to the seafloor. We propose a simple model to evaluate the extent to which the peak and notch have formed, which depends on the natural frequencies and coupling of the pressure vessel. We suggest users of in-line-type OBSs carefully examine if there are different responses between the X and Y components when frequencies about > 3 Hz are used. When installing OBS networks in the future, installing OBSs and cables within grooves dug in the seafloor or by burial will be effective in suppressing such natural vibrations.

Pressure Vessel Design by Design by Analysis Route

Pressure vessels are conventionally designed based on the Design by Rule (DBR) approach. Standard vessel geometries are designed using simple formulae and charts, formulated as standards and codes based on the rules proposed in the ASME Boiler and Pressure Vessel Code and the European Standard prEN13445-3. The stress categorization problem faced employing DBR methodology was overcome by employing Limit Load Analysis using the DBA approach. A simple unfired vertical cylindrical pressure vessel with torispherical pressure head and Y-forged skirt support was analyzed for its structural integrity using ANSYS software. The results obtained for two different materials, high strength steel P500-QT and the conventional low strength steel P355 employing DBA approach was compared with the calculated results using the DBR approach. The maximum allowable pressure (PMAX) for P500-QT material was found to be 2.5X the maximum pressure calculated using the DBR approach as per ASME codes and 3X times as per EN13445-3 standard. For P355 material the maximum allowable pressure (PMAX) was found to be 2.32X the maximum pressure calculated using the DBR approach as per ASME codes and 2.6X times as per EN13445-3. The DBR methodology proves to be highly conservative whereas the use of DBA leads to less conservative design parameters.

Stress Intensity Factor of Inclined Internal Edge Crack in Cylindrical Pressure Vessel

In this work, the stress intensity factor of inclined edge cracks introduced on the inner surface of a cylindrical pressure vessel is analyzed through numerical simulation. The fracture analysis was performed using a two-dimensional axisymmetric finite element model. The results reveal that, as the crack inclination increases beyond 30o, mode II loading becomes dominant. As the crack length increases, mode II loading acts in a profound manner in the component. In addition, the stress intensity factor of inclined crack was examined in the presence of multiple cracks. It was found that after a certain spacing between the inclined and neighboring crack, the ratio of mode I to mode II remains constant due to the non-interaction of stress fields around the crack.

Application of Corrugated Core Sandwich Structures in Thin Cylindrical Pressure Vessels

the need for the high strength to weight structures is increasing day by day. The structures with high strength to weight ratio helps in reducing the costs in transport of materials. The sandwich structures are being developed to meet this criterion. A sandwich structure consists of two flat sheets with core between them. The material of core and outer flat surfaces may or may not be the same depending upon the application of the structure. In this project, the corrugated core sandwich structure will be used for the cylindrical shell of the pressure vessels. Pressure vessel with corrugated core sandwich structures will be designed and various analyses will be performed. The results will be compared with thin cylindrical shell pressure vessel under similar conditions. The pressure vessels will be designed in solidworks software and structural analysis will be performed in ansys workbench.

Effects of geometry of a local thin area defect on remaining strength and fitness of pressure equipment

As an important equipment for production, pressure vessels are important equipment in the factory and can be dangerous when there is structural damage. In recent years, the development of applicability assessment technology has enabled various defects to be properly evaluated. The local thinning defect (LTA) basically uses the RSF as an indicator to measure the eligibility of the device. In the evaluation process using API 579 Level 1 and Level 2, different LTAs have the same residual strength results, so the availability evaluation results may have doubts. However, when using API 579 Level 1 and Level 2 for defect evaluation, it was found that two defects of the same length but different widths had the same residual strength. Therefore, this study explores its causes in depth.In addition, the practice of treating the defect thickness profile in CTP mode in API 579 Level 2 is considered to be relatively conservative and hence be safer. However, reordering the defect profile in fact smooth out the stress concentration effect and offers an overly optimistic estimate on the fitness of the device.First of all, the experiment started off with a set of real defect data, which was taken from measuring a localized thin area on a cylindrical pressure vessel. By changing the width of the LTA, a list of defects were generated and finite element analysis was performed. What follows is to compare results of finite element models with defects modeled with true thickness profile, critical thickness profile(CTP), and parabolic profile.For a square LTA, results from API 579 Level 2 approach is quite close to those from finite element analysis. However, the variation increases as the aspect ration of width to length of LTA becomes large. Contrary to the API 579 Level 2, the width dimension of LTA does have influence RSF, and should be taken into account. Also, in API 579, a rearranged CTP was used instead of the true profile of LTA on a belief that results from using CTP is more conservative, which later was found to be incorrect. Hence, the true thickness profile is preferred in most cases.

Free Vibration Analysis of FG-CNTRC Cylindrical Pressure Vessels resting on Pasternak Foundation with Various Boundary Conditions

Free Vibration Analysis of FG-CNTRC Cylindrical Pressure Vessels resting on Pasternak Foundation with Various Boundary Conditions

A dimensionally adaptive technique for computationally efficient cylindrical discrete ordinates radiation calculations

The use of high aspect ratio cylindrical pressure vessels and rotationally periodic burners in Pressurized Oxy-Coal (POC) furnaces leads to physical behavior that is 3D periodic near the burner, but which transitions to axisymmetric towards the outlet. A fully 3D model would consume unneeded resources, and an axisymmetric model would fail to capture periodic features of the near burner region, such as recirculation zones. The present work evaluates the ability of a dimensionally adaptive mesh (i.e., one that transitions from 3D to axisymmetric and 1D) to improve computational speed while still accurately calculating heat flux for such cylindrical systems. The Discrete Ordinates Method (DOM) was used to solve the cylindrical Radiative Transfer Equation (RTE) on both a dimensionally adaptive mesh and a fully 3D mesh. The effects of both spatial and angular refinement on speedup and agreement between the adaptive and fully 3D mesh were studied. For the four cylindrical combustor configurations studied, speedups ranged from 46.6% on a coarse adaptive mesh to 49.1% on a fine mesh. Increasing angular resolution decreased speedups from 48.0% at S2 to 37.1% at S8. Increasing angular resolution from S2 to S4 reduced the overall percent difference between adaptive and 3D meshes from 0.656% to 0.381%. Increasing angular resolution beyond S4 did not significantly improve agreement between mesh types.

Gas pressure and density effects on vibration of cylindrical pressure vessels: analytical, numerical and experimental analysis

The present research deals with the natural frequencies and mode shapes of cylindrical pressure vessels filled with different gasses in various internal pressures. The Hamilton’s principle is employed to derive the governing equations, which are solved using analytical and finite element analyses, and a closed form relation as the equivalent density is obtained to include the gas properties. The experimental modal analysis is performed and the obtained results are compared and validated with analytical and finite element results. The results show that the type of the gas, as well as the gas pressure have significant effect on vibrational behavior of the structure and should be accounted in the design and analysis of vessels.