Cylindrical Steel Storage Tanks Research Articles

Experimental Investigation on the Effect of Seal Presence on the Behavior of Double-Deck Floating Roofs in Cylindrical Steel Storage Tanks

Liquid storage, particularly oil and petrochemical products which are considered hazardous liquid, are an important part of the oil industry. Thin-walled vertical cylindrical steel storage tanks are widely used in recent years. Due to high sensitivity of these structures in an earthquake and other external excitations may lead to catastrophic consequences. For instance, huge economic losses, environmental damages, and casualities, many studies have been done about these structures. past studies showed that liquid storage tanks, equipped with a floating roof, are potentially vulnerable while subjected to seismic loads and earthquake has been considered as one of the most destructive natural hazards. The reason is that such tanks are made of two separated parts (shell and roof) which each may have its own responses; sometimes causing resonance phenomenon and so that, roof movements, roof-fluid interaction, roof-shell interaction, and also the way they are attached should still be investigated. Experimental tests of floating roof’s vertical fluctuation was performed in a full-scale reservoir tank and assessing of the results demonstrated that presence of a seal between floating roof and shell plate can significantly increase damping ratio in liquid sloshing and also suppress the roof`s vertical displacements. In other words, seal can control a floating roof and make it stop moving vertically over few cycles.

Multi-objective optimal design and seismic assessment of an inerter-based hybrid control system for storage tanks

In this paper, a hybrid control system (HCS) endowing a base isolation system (BIS) with a Tuned Mass Damper Inerter (TMDI) is proposed for the protection of steel storage tanks from severe structural damages induced by seismic events. Among all the components of industrial plants, cylindrical steel storage tanks are widely spread and play a primary role when subjected to seismic hazard, since they suffer of many critical issues related to their dynamic response such as high convective wave height and base shear force. The adopted base isolation system is realized with spring and damper elements, whereas the TMDI is realized with a tuned mass damper connected to the ground by the inerter. The developed mechanical model consists of a MDOF system, which considers the impulsive and convective modes as well as the TMDI dynamics. An optimal design problem is tackled, making use of a multi-objective approach, with the scope to mitigate simultaneously the convective and impulsive response of the storage tank. A zero mean white noise excitation is assumed as input in the optimal design procedure. Once the HCS is optimally designed, a systematic investigation of its seismic effectiveness is reached through parametric analysis. Modal parameters and frequency response functions are discussed. A literature case study comparing the effectiveness of the proposed optimally designed HCS with traditional base isolation is illustrated and performances are assessed through stochastic excitation and natural earthquakes.

Three-Dimensional Nonlinear Dynamic Analysis of Base Isolated Cylindrical Steel Tank

Failure of a tank during an earthquake can result in significant financial, human, and environmental losses. Thus, their lack of resiliency against strong earthquakes may result in refinery disruption. This has the potential to have a considerable impact on any economic system. As a result, more research into the seismic performance of tank structures is required to attain the highest possible level of resistance against strong earthquakes. In this paper, we aim to look into the installation of seismic isolation systems in cylindrical steel storage tanks. A nonlinear 3D finite element model is developed with ANSYS software. Moreover, tank wall material nonlinearity, fluid-structure-interaction, and sloshing components are considered. The bilinear hysteretic LRB is used for modal and time-history analysis. In this work, three tanks with varying aspect ratios are studied: "Model A", "Model B", and "Model C". Furthermore, the fixed tank's fundamental frequencies were compared to the analytical results of the American API 650 Standard. Subsequently, the dynamic behavior response of the researched tanks to the horizontal component of the El-Centro 1940 earthquake with PGAs of 0.34g and 0.5g is investigated. As a result, the dominating frequency of the seismic isolation system is within the effective frequency range of seismically isolated systems. The results illustrate that the base isolation limits the tank wall movement with a large displacement in the isolators; the mode shape is a cantilever beam in all isolated circumstances. The total seismic response reduction in the slender tanks is greater as compared to the broad case in the base-isolated tanks. The sloshing displacement increases with an increase in the tank aspect ratio. Additionally, the isolation device eliminates tank buckling at the base and top of the tank shell during seismic excitation (elephant foot and diamond buckling). It can be concluded that the seismic isolation technique has a more significant impact on reducing the dynamic response of ground-supported tanks, particularly in taller tanks as compared to broad tanks. Doi: 10.28991/CEJ-2022-08-06-013 Full Text: PDF

Brittle Fractures of Cylindrical Steel Storage Tanks for Petroleum and Petroleum Products in the North

This article discusses brittle fracture accidents of petroleum and petroleum products storage tanks that occurred in Yakutia. Operational safety of tanks in the cryolithozone is reduced by harsh natural and climatic conditions, the uniform and differential settlements of the shell and bottom, long-term operation associated with the degradation of structures and materials in such climatic conditions. The main factor contributing to brittle fracture is extreme low ambient temperature, which reduces the ductility and resistance to brittle fracture of steel of structures and welds. The uniform and differential settlements of the tank lead to appearance of dangerous stress-strain state of shell and its general and local deformations. A sharp change in the air temperature causes thermal stresses in the statically indeterminate structures of the tank. Analysis of tank accidents in Yakutia shows that places of crack initiation are assembly welds and their heat-affected zones, the metallurgical and corrosion defects of the base metal. Dangerous areas of the tank are shell-to-bottom connections and attachments of piping nozzles to the shell. The main cause of the considered accidents is the use of low-carbon steel that does not recommend to the oil tank operation in the climatic conditions of the cryolithozone.

Stability of Open‐Top Cylindrical Steel Tanks with Primary Stiffening Ring under Wind Loading

AbstractCylindrical steel tanks are very thin shell structures and vulnerable to buckling under external pressure due to wind or partial vacuum due to rapid emptying or blocked vents when they are either empty or partially emptied. A primary stiffening ring is commonly used at or near the top of the tank wall to increase its strength against external pressure instability. Most traditional design treatments largely ignore the non‐uniform circumferential variation of the wind and treat the tank as subject only to uniform external pressure when sizing the primary stiffening ring. Moreover, the interior of the tank also experiences suction pressures due to the leeward suction on the tank. Wind tunnel tests have shown that the magnitude of these suctions can be very significant compared with the external wind pressures. This study has investigated the buckling resistance of a range of cylindrical steel storage tanks with primary stiffening rings subjected to non‐uniform wind loading modeled as harmonic variations, including the suction, using finite element analyses. A criterion for the required primary stiffening ring stiffness is developed, which is found to depend on its value relative to the stiffness of the cylindrical shell under each harmonic of wind loading. The effects of the shell‐ring stiffness ratio on the buckling capacity are studied and it is found to be a powerful measure that is critical to the design of the ring. Improved design rules are directly obtainable from this new treatment.

Dynamic response of polyurea coated thin steel storage tank to long duration blast loadings

Cylindrical steel storage tanks are often under the threat of long duration blast loadings induced by the explosion of flammable vapor clouds, and therefore the blast response and mitigation method of the tanks are of great importance to related industries. In the meantime, polyurea coating material, which has been proved to be effective in the blast mitigation of different structures, is employed in this study for the protection of steel storage tanks. Gas blast experiments, as well as numerical and theoretical models, are utilized to investigate the response and energy absorption mechanism of steel tanks and analyze the effect of polyurea coatings. The numerical results showed that the bending of the plastic hinge lines and the tension of the connect zone of the cylindrical shell are the main energy absorption ways of the tank. The modified beam-on-foundation model is then established and verified and the model indicates that the polyurea coatings mainly influence the displacements of the tanks by increasing the area density and bending moments of the tanks. Quantitative analysis on the effect of polyurea is conducted utilizing the response spectrum of the tank’s equivalent system and the range of displacement reducing ratio caused by polyurea and the appropriate spraying strategy of polyurea are acquired accordingly. At last, further numerical simulations are performed and give results that validate the theoretical predictions.

Effects of The Shell Thickness On The Directional Deformation And Buckling On The Cylindrical Steel Water Tanks Under The Kobe Earthquake Loading

Cylindrical steel storage tanks are widely used for the storage of various liquids, industrial chemicals and firefighting waters. They have been used for cooling purposes in nuclear power plants in recent years. Liquid-storage tanks have many different configurations; however, in this study, cylindrical ground-supported liquid steel tanks were preferred because of their simplicity in design and construction as well as their efficiency in resisting hydrostatic and hydrodynamic applied loads, when compared with other configurations. If liquid steel tanks are damaged in an earthquake, they can also cause great financial and environmental damage with their hazardous chemical contents. These tanks may be exposed to some damages such as elephant-foot buckling, diamond-shape buckling, overturning and uplifting during earthquakes. Dimensions of cylindrical open-top, flat-closed and torispherical-closed top tanks were determined for 3D-finite element method (FEM) models in an ANSYS workbench software. This article focuses on the seismic-activity-resistant ground-supported cylindrical (vertical) steel storage liquid tanks. Seismic analyses were conducted under Kobe earthquake loads. The frequency values calculated with API 650 were verified with the FEM model results. Directional deformation, buckling results were presented for both impulsive and convective regions. According to API 650 standard, the tank shell thickness is 6 mm. Simulations were performed with 4 mm and 8 mm shell thickness for tanks. In this study, directional deformation and buckling were observed with simulations made by choosing the shell thickness under (4 mm) the standard and above (8 mm) the standard, unlike the approaches in the literature. As a result, it was observed that the 8 mm shell thickness determined above the standard increased the deformation in the flat-closed tank. In addition, torispherical dome-shaped tanks have been observed to lower directional deformation and buckling in any case. The differences obtained are detailed with

Typical damage in steel storage tanks in operation

The safe and long service life of structures could be assured only when adequate design and construction are combined with a proper and regular maintenance. The principal objective of this paper is to identify the most common failures that may occur in above ground cylindrical steel storage tanks in operation, to suggest better design decisions, possible solutions for repair and provide guidelines for appropriate care and maintenance of this type of structures.A group of specialists was assigned the task to conduct a site inspection and provide a statement for the operational condition of 7 new and 13 steel storage tanks in service, owned by State agency “State reserve and war-time stocks”. The facilities contain different oil products – petrol, diesel and mixed fuel stored at ambient temperature and atmospheric pressure. The anchorage conditions vary. Some of the examined storage tanks were built in the 1970s, others – in the period 2009 - 2014. The audit was carried out in accordance with the Agency’s internal directive and standards API 650, API 653, EN 1993-4-2, EN 14015.Based on this representative study and the practical design experience of the authors, this paper classifies the most frequently reported damage in different elements of tanks in operation – foundations, anchorage (if present), annular plates, tank bottom, shell, roof (fixed or floating), attached accessories and systems. Illustrative examples are presented, along with explanations for the critical aspects of adequate maintenance. Finally, some conclusions are drawn in the form of guidelines for failure prevention and if the damage already exists - possible ways for restoration of the facility to its proper operational state.

The Effects of Carbon Fiber Reinforced Polymer Strengthening on Cylindrical Steel Storage Tanks under Bending Shear Load

Large thin-walled cylindrical steel storage tanks play important roles in the development of economy and infrastructures. Storage tanks subjected to internal pressure can cause buckling modes, especially elephant foot bulge at the bottom of the tanks. The design of tanks against buckling is very necessary. In this paper, the load-carrying capacity and the failure modes of the storage tanks subjected to internal pressure under bending shear load will be calculated by the finite element analysis. The results will be compared with the design method from Architectural Institute of Japan. Moreover, this paper will also consider the effects of the use of carbon fiber reinforced polymer layers to strengthen storage tanks against buckling and the increase of the load-carrying capacity of the tanks under bending shear load.

Stability of Open Top Cylindrical Steel Storage Tanks: Design of Top Wind Girder

Design of the top wind stiffeners of aboveground storage tanks designed to the requirements of API 650 is investigated. The current design methodology is based on intuition and experience without a sound technical justification. This paper investigates a diameter limit to be used in the design of the top stiffener ring by using finite-element analysis (FEA) in a parametric study. Linear bifurcation analysis (LBA) and geometrically nonlinear analysis including imperfections (GNIA) were performed on cylindrical storage tanks. By modeling tanks with different diameters and limiting the design of top stiffener ring for a diameter of 170-ft (52-m), the buckling loads are investigated. It was found that the 170-ft (52-m) diameter is a suitable upper limit to design the top stiffener rings for larger diameters.

Multilevel Methodology of Numerical Seismic Analysis of Coupled Systems “Foundation – Shell – Pontoon (Floating Roof) –Column(s) – Fluid”

The distinctive paper is devoted to multilevel methodology of numerical seismic analysis of coupled systems “foundation – shell – pontoon (floating roof) – column(s) – fluid” (Methodology). It can be effectively used to help to ensure the safety of vertical cylindrical steel storage tanks for oil and petroleum products (hereinafter – tanks). Authors of Methodology have analyzed and taken into account of corresponding Russian design codes dealing with the safety of reservoirs, experience of design and analysis of reservoirs, international publications on issues of mathematical (computer) simulations of behavior of tanks.

The effects of long term uniform corrosion on the buckling of ground based steel tanks under seismic loading

Material degradation due to corrosion significantly alters the seismic response of ground-based cylindrical steel storage tanks. A numerical study is conducted to investigate the effects of internal shell corrosion on the dynamic buckling of three cone roof ground-based, steel cylindrical tanks with height to diameter ratios (H/D) of 0.40, 0.63 and 0.95, subjected to horizontal seismic base excitations. Internal corrosion is considered as a time dependent uniform thinning of the wall at the upper and the lower parts of the tank being in contact with, respectively, atmospheric oxygen and acid gases and residual water. Detailed numerical models of the tank–liquid systems at different stages of corrosion degradation are subjected to two representing accelerograms and for each model the critical peak ground acceleration (PGA) for dynamic buckling of the shell and its associated mode of failure are evaluated. It is found that in all three tanks, the critical PGA is markedly reduced with thinning of the shell, irrespective of the type of ground input. The buckling mode of failure of the tanks also changed from an elastic diamond-shaped failure at the top of the shell to an elasto-plastic elephant foot type failure near the base, after 10 years for the shorter tanks (H/D=0.4 and 0.63) and after 15 years for the tallest tank. The effects of uniform corrosion degradation on the critical buckling load of the tanks were found to be such that after 20 years of thinning due to corrosion, the static loading alone was responsible for the elephant foot buckling of the shell.

Buckling strength of cylindrical steel tanks under harmonic settlement

Large vertical cylindrical steel tanks for bulk and fluid storage are usually constructed in soft foundations, so it is not surprising that tank foundations are susceptible to various types of settlement beneath the tank wall, which is usually decomposed as a Fourier series in harmonics. In this paper, buckling strength of cylindrical fixed-roof steel storage tanks under harmonic settlement is investigated through great deal of numerical analyses by the FE computer package ANSYS. Three types of buckling analyses are carried out which are the LBA, GNA, GNIA proposed also by Eurocode 3. The results show that the equilibrium path from both GNA and GNIA is highly nonlinear, and it seems ungrounded to establish design criterion on the principle of superposition based on the linear elastic theory. The influences of the harmonic wave number n, the radius-to-thickness ratio r/ t, the height-to-radius ratio h/ r, and the geometric imperfection δ 0/ t on the buckling strength of the storage tanks are mainly investigated. The ultimate harmonic settlements for various tank geometries are addressed and plotted in each analysis together with the buckling modes. The buckling modes from GNA and GNIA agree well with the lowest linear bifurcation buckling modes from LBA, and take mainly two types of deformations: shearing buckling extending throughout the entire height for the lower wave number n=2–4 and the elephant's foot failure occurring at the upward settlement zone caused by the meridional compression for the higher wave number n>4. It is also indicated from the results that both the ultimate harmonic settlement and the buckling mode of the tank are closely correlative with the geometric parameters: the wave number n, the radius-to-thickness ratio r/ t, the height-to-radius ratio h/ r, and the initial geometric imperfection δ 0/ t.

The tapered beam model for bottom plate uplift analysis of unanchored cylindrical steel storage tanks

During severe earthquakes, the most important parameter affecting the uplift response of unanchored tanks is the highly nonlinear behavior of their bottom plates. This study mainly focuses on the investigation of this phenomenon using a tapered beam which is resting on a rigid foundation. Analytical equations of the beam are derived and solved numerically; the results are compared with those of the constant width beam presented in other studies. Convergence difficulties at small uplift lengths are investigated. The solution of the model at zero uplift length is presented, and the effects of shell deformations, due to hydrostatic pressures, on uplift response are investigated.

The Checking of Horizontal Cylindrical Steel Storage Tanks

The deformation of the cross sections of the compartments of horizontal cylindrical storage tanks, which occurs during manufacture and when they are loaded during use, is analyzed. Volumetric and geometric methods of checking storage tanks are also analyzed. Recommendations are made on choosing the function for describing the close-to-circular cylindrical shape of storage-tank compartments and on the use of volumetric and geometric methods of checking horizontal cylindrical steel storage tanks.

Settlement limitations for cylindrical steel storage tanks : Rosenberg, P; Journeaux, N L Can Geotech J, V19, N3, Aug 1982, P232–238

Settlement limitations for cylindrical steel storage tanks : Rosenberg, P; Journeaux, N L Can Geotech J, V19, N3, Aug 1982, P232–238

Settlement limitations for cylindrical steel storage tanks: Discussion

Settlement limitations for cylindrical steel storage tanks: Discussion

Erratum: Settlement limitations for cylindrical steel storage tanks

Erratum: Settlement limitations for cylindrical steel storage tanks

Settlement limitations for cylindrical steel storage tanks

Tank inspections in the petroleum industry often include an evaluation of settlement effects. Tank failures and floating-roof problems have often been attributed to distortion of tanks due to settlement. In geotechnical practice evaluation of excessive settlement is done by referring to empirically derived limits that vary considerably.In this study the authors took settlement data from the literature and their own studies, and compared the results with limits commonly used in tank evaluations. On this basis tentative limit criteria are suggested that can be used in estimating the probability of the occurrence of tank problems.

Foundations and earthworks for cylindrical steel storage tanks : Harris, G Ground Engng. V9, N5, July, 1976, P24–31

The design and construction techniques for steel storage tanks for storing oil and general bulk commodities are reviewed. The nature of storage tanks are described, the effects of settlement of tanks are discussed, and comments are made on tank loadings, foundations, water testing and settlement records, dyke compount areas, and underwriting considerations. Shell bearing plates are used for fixed roof tanks where shell bearing pressures are in excess of 100 kilopascals or where floating roof tanks are involved. Large size cone roof tanks have their roofs supported on columns and generally a center column. The dead load on columns normally ranges from 50 to 100 kn, whereas live load can add a further 100 to 150 kn per column. Foundation solutions for varying soil conditions are diagramatically illustrated and relate to shallow foundations in competant graound, foundations for poor ground conditions, fill replacement technique, piled foundations, and foundation preloading. Tests to ensure that the storage tank is water tight, and that the foundation is adequate to carry the loadings are discussed. The dyking (to retain spillage and prevent flooding and pollution) precaustions to be adopted in any instance will depend on the nature of the commodity being stored. Underwriting consideraions are discussed related to the storage of hydrocarbons.