Roof Tanks Research Articles

Sloshing Characteristics of Single-Deck Floating Roofs in Cylindrical Storage Tanks

Sloshing Characteristics of Single-Deck Floating Roofs in Cylindrical Storage Tanks

Acanthamoeba spp. in domestic tap water in houses of contact lens wearers in the metropolitan area of Mexico City

A survey was carried out in the metropolitan area of Mexico City to determine the presence of Acanthamoeba in the tap water of houses of contact lens wearers. Water samples were taken from the mains water entry, bathroom sinks and storage containers (roof tanks, cisterns) of 27 houses; and from the solution contained in the contact lens cases. Samples were filtered and cultured onto NNE medium. The isolates were identified based on their morphological features and pathogenicity. Total and fecal coliforms, water temperature, pH, dissolved oxygen and residual free-chlorine were measured by standard methods. Forty five isolates of Acanthamoeba from 200 water samples were obtained. The highest number of amoebae was isolated from cisterns and roof tanks. Most Acanthamoeba isolates were non-pathogenic, however, their presence in tap water is a potential hazard since some species can cause Acanthamoeba keratitis and granulomatous amoebic encephalitis.

ALE and Fluid Structure Interaction for Sloshing Analysis

Liquid containment tanks are, generally, subjected to large deformations under severe earthquake conditions due to coupling forces between tank and the contained liquid. The accurate description of these forces is vital in order to diminish or eliminate the potential risk of tank failure during an earthquake. Yet, analytical formulations derived for the seismic analysis of liquid storage tanks are not capable to capture the complex fluid-structure effects since they include many assumptions and simplifications not only for the behavior of fluid and structure but also for the external excitation. On the other hand, an appropriate numerical method allows us to cope with large displacements of free surface of the fluid, high deformations of the structure and correctly predicts the hydrodynamic forces due to the high-speed impacts of sloshing liquid on a tank wall and roof. For this purpose, a new coupling algorithm based on the penalty formulation of finite element method which computes the coupling forces at the fluidstructure interface is developed in this paper. This algorithm is constructed on a two superimposed mesh systems which are a fixed or moving ALE mesh for fluid and a deformable Lagrangian mesh for structure. The fluid is represented by Navier-Stokes equations and coupled system is solved using an explicit time integration scheme. In order to verify the analysis capability of coupling algorithm for tank problems, numerical method is applied for the analyses of a rigid rectangular tank under harmonic excitation and a flexible cylindrical tank subjected to earthquake motion and numerical results are compared with existing analytical and experimental results. Strong correlation between reference solution and numerical results is obtained in terms of sloshing wave height.

シングルデッキ形浮屋根式円筒タンクのスロッシング特性 : 動液圧モードと浮屋根強度モード(機械力学,計測,自動制御)

シングルデッキ形浮屋根式円筒タンクのスロッシング特性 : 動液圧モードと浮屋根強度モード(機械力学,計測,自動制御)

263 センターポンツーン付きシングルデッキ形浮屋根式タンクのスロッシング

The floating roofs are widely used to prevent evaporation of content in large oil storage tanks. The 2003 Tokachi-Oki earthquake caused severe damage to the floating roofs due to liquid sloshing. Several damaged floating roofs in large diameter tanks were the single deck type with center pontoon. This paper presents the sloshing characteristics of a single deck floating roof with center pontoon in cylindrical storage tank. The hydrodynamic coupling of fluid and floating roof is taken into consideration in the axisymmetric finite element analysis. It is assumed that the fluid is incompressible and inviscid, and the floating roof is linear elastic while the sidewall and the bottom are rigid. The basic vibration characteristics, natural periods and vibration modes and so on, of the floating roof due to the sloshing are investigated. These will give engineers important information on the design.

Stability Analysis of Local Thinned Shallow Spherical Roof of Oil Storage Tank

The analytical evaluation and finite element methods are used to analyze the critical stability of the shallow spherical roof of oil storage tank with an axial symmetrical corrosion region. At first, the nonlinear finite element method is adopted to calculate the global critical load of the storage tank roof, and the local corrosion region is equivalent to a circular corrosion pit with uniform depth. The results show that the tank wall and inner pressure of the stored oil have slight effects on the stability of the roof. To build the formula of local critical load of the tank roof, the circular corrosion pit is separated from the whole roof and treated as a shallow spherical shell which is elastically supported on the rest part of the roof. The equivalent support stiffness is obtained by the deformation compatibility at the edge of the corrosion pit. The resulted nonlinear stability equation is solved with a modified iteration method to determine the local critical load. The local critical load for an in-service corroded oil tank roof is analyzed by the proposed approach and the results are compared with those calculated by the conventional nonlinear finite element method with good agreement and the geometrical parameter of the corrosion region corresponding to the minimal critical load is 9.5.

Axisymmetric Finite Element Analysis for Sloshing Response of Floating Roofs in Cylindrical Storage Tanks

The floating roofs are widely used to prevent evaporation of content in the large oil storage tanks. The 2003 Tokachi-Oki earthquake caused severe damage to the floating roofs due to liquid sloshing. The structural integrity of the floating roofs for the sloshing is urgent issue to establish for the petrochemical and oil refining industries. This paper presents the axisymmetric finite element analysis for the sloshing response of floating roofs in cylindrical storage tanks. The hydrodynamic coupling of fluid and floating roof under seismic excitation is taken into consideration in the analysis. It is assumed that the fluid is incompressible and inviscid, and the roof is linear elastic while the sidewall and the bottom are rigid. The theory for the finite element analysis in which the behavior of the fluid is formulated in terms of dynamic pressure as the Eulerian approach is developed. The basic vibration characteristics of the floating roof, such as natural frequencies and vibration modes, can be obtained from the analysis. These give engineers important information on the floating roof design.

Lessons Learned from Fires of Inner Roof Tanks Outside Japan National Research Institute of Fire and Disaster

Lessons Learned from Fires of Inner Roof Tanks Outside Japan National Research Institute of Fire and Disaster

11706 浮屋根式円筒タンクのスロッシング応答の軸対称有限要素解析(振動工学(1),一般講演,学術講演)

11706 浮屋根式円筒タンクのスロッシング応答の軸対称有限要素解析(振動工学(1),一般講演,学術講演)

Sloshing Characteristics of Single Deck Floating Roofts in Cylindrical Storage Tanks (Natural Periods and Natural Vibration Modes)

The floating roofs are widely used to prevent evaporation of content in the large oil storage tanks. The 2003 Tokachi-Oki earthquake caused severe damage to the floating roofs due to liquid sloshing. The structural integrity of the floating roofs for the sloshing is urgent issue to establish in the petrochemical and oil refining industries. This paper presents the sloshing characteristics of single deck floating roofs in cylindrical storage tanks. The hydrodynamic coupling of fluid and floating roof is taken into consideration in the axisymmetric finite element analysis. It is assumed that the fluid is incompressible and inviscid, and the roof is linear elastic while the sidewall and the bottom are rigid. The basic vibration characteristics, natural periods and vibration modes, of the floating roof due to the sloshing are investigated. These will give engineers important information on the floating roof design.

820 シングルデッキ形浮屋根式円筒タンクのスロッシング動液圧と強度の特性(OS24.一般セッション(5) 流体、流体-構造連成解析,オーガナイズドセッション)

820 シングルデッキ形浮屋根式円筒タンクのスロッシング動液圧と強度の特性(OS24.一般セッション(5) 流体、流体-構造連成解析,オーガナイズドセッション)

171 シングルデッキ形浮屋根式円筒タンクのスロッシング特性

171 シングルデッキ形浮屋根式円筒タンクのスロッシング特性

Effect of foundation embedment on seismic behavior of elevated tanks considering fluid–structure-soil interaction

This paper investigates the effects of foundation embedment on the seismic behavior of fluid-elevated tank-foundation–soil system with a structural frame supporting the fluid containing tank. Six different soil types defined in the well-known seismic codes were considered. Both the sloshing effects of the fluid and soil-structure interaction of the elevated tanks located on these six different soils were included in the analyses. Fluid-elevated tank-foundation–soil systems were modeled with the finite element (FE) technique. The fluid-structure interaction was taken into account using Lagrangian fluid FE approximation implemented in the general purpose structural analysis computer program, ANSYS. FE model with viscous boundary was used to include elevated tank-foundation–soil interaction effects. The models were analyzed for the foundations with and without embedment. It was found that the tank roof displacements were affected significantly by the embedment in soft soil, however, this effect was smaller for stiff soil types. Except for soft soil types, embedment did not affect the other response parameters, such as sloshing displacement, of the systems considered in this study.

222 石油タンク浮屋根のスロッシング応答

222 石油タンク浮屋根のスロッシング応答

223 FEMによる浮屋根式タンクのスロッシングシミュレーション

The 2003 Tokachi-Oki earthquake caused severe damage of oil storage tanks due to long-period ground motions. After that, the technical standards of the Fire Service Act regarding the sloshing with floating roof tanks were revised. The influences of non-linearity of liquid behavior and 2nd mode sloshing were taken into consideration using FEM(Finite Element Method) at this time. However, it is not enough that sufficient description about FEM model such as contact definition, time steps, number of element division, hourglass control and seal model. In this paper, the authors present the suitable model of sloshing simulation for floating roof in oil storage tanks using FEM.

Earthquake Induced Sloshing in Tanks with Insufficient Freeboard

Earthquake induced sloshing in tanks is caused by long-period ground motions which attenuate slowly with distance. A minimum freeboard is needed to accommodate the sloshing waves. Since freeboard results in unused storage capacity, many tanks lack the required freeboard. As a result, sloshing waves impact the roof, generating additional forces on the roof and tank wall. Tanks have suffered extensive damage due to sloshing waves, but the effect of sloshing waves is usually ignored in seismic design of tanks. This paper presents a simple method of estimating sloshing loads in cone and dome roof tanks.

Organic Liquids Storage Tanks Volatile Organic Compounds (VOCS) Emissions Dispersion and Risk Assessment in Developing Countries: The Case of Dar-Es-Salaam City, Tanzania

The emission estimation of nine volatile organic compounds (VOCs) from eight organic liquids storage tanks companies in Dar-es-Salaam City Tanzania has been done by using US EPA standard regulatory storage tanks emission model (TANKS 4.9b). Total VOCs atmospheric emission has been established to be 853.20 metric tones/yr. It has been established further that petrol storage tanks contribute about 87% of total VOCs emitted, while tanks for other refined products and crude oil were emitting 10% and 3% of VOCs respectively. Of the eight sources (companies), the highest emission value from a single source was 233,222.94 kg/yr and the lowest single source emission value was 6881.87 kg/yr. The total VOCs emissions estimated for each of the eight sources were found to be higher than the standard level of 40,000 kg/yr per source for minor source according to US EPA except for two sources, which were emitting VOCs below the standard level. The annual emissions per single source for each of the VOCs were found to be below the US EPA emissions standard which is 2,000 kg/yr in all companies except the emission of hexane from company F1 which was slightly higher than the standard. The type of tanks used seems to significantly influence the emission rate. Vertical fixed roof tanks (VFRT) emit a lot more than externally floating roof tanks (EFRT) and internally floating roof tanks (IFRT). The use of IFRT and EFRT should be encouraged especially for storage of petrol which had highest atmospheric emission contribution. Model predicted atmospheric emissions are less than annual losses measured by companies in all the eight sources. It is possible that there are other routes for losses beside atmospheric emissions. It is therefore important that waste reduction efforts in these companies are directed not only to reducing atmospheric emissions, but also prevention of the spillage and leakage of stored liquid and curbing of the frequently reported illegal siphoning of stored products. Emission rates for benzene, toluene, and xylene were used as input to CALPUFF air dispersion model for the calculation of spatial downwind concentrations from area sources. By using global positioning system (GPS) and geographical information system (GIS) the spatial benzene concentration contributed by organic liquid storage tanks has been mapped for Dar-es-Salaam City. Highest concentrations for all the three toxic pollutants were observed at Kigamboni area, possibly because the area is located at the wind prevailing direction from the locations of the storage tanks. The model predicted concentrations downwind from the sources were below tolerable concentrations by WHO and US-OSHA. The highest 24 hrs averaging time benzene concentration was used for risk assessment in order to determine maximum carcinogenic risk amongst the population exposed at downwind. Established risk for adult and children at 2.9x10(-3) and 1.9x10(-3) respectively, are higher than the acceptable US-EPA risk of 1x10(-6). It is very likely that the actual VOCs concentrations in some urban areas in Tanzania including Dar-es-Salaam City are much higher than the levels reported in this study when other sources such as petrol stations and motor vehicles on the roads are considered. Tanzania Government therefore need to put in place: an air quality policy and legislation, establish air quality guidelines and acquire facilities which will enable the implementation of air quality monitoring and management programmes.

Dynamic buckling of anchored steel tanks subjected to horizontal earthquake excitation

We investigate dynamic buckling of aboveground steel tanks with conical roofs and anchored to the foundation, subjected to horizontal components of real earthquake records. The study attempts to estimate the critical horizontal peak ground acceleration (Critical PGA), which induces elastic buckling at the top of the cylindrical shell, for the impulsive hydrodynamic response of the tank–liquid system. Finite elements models of three cone roof tanks with height to diameter ratios ( H / D ) of 0.40, 0.63 and 0.95 and with a liquid level of 90% of the height of the cylinder were used in this study. The tank models were subjected to accelerograms recorded during the 1986 El Salvador and 1966 Parkfield earthquakes, and dynamic buckling computations (including material and geometric non-linearity) were carried out using the finite element package ABAQUS. For the El Salvador accelerogram, the critical PGA for buckling at the top of the cylindrical shell decreased with the H / D ratio of the tank, while similar critical PGAs regardless of the H / D ratio were obtained for the tanks subjected to the Parkfield accelerogram. The elastic buckling at the top occurred as a critical state for the medium height and tallest models regardless of the accelerogram considered, because plasticity was reached for a PGA larger than the critical PGA. For the shortest model ( H / D = 0.40 ) , depending on the accelerogram considered, plasticity was reached at the shell before buckling at the top of the shell.

Sloshing Loads in Liquid-Storage Tanks with Insufficient Freeboard

Seismic ground motions excite long-period sloshing response in liquid-storage tanks. A minimum freeboard is needed to prevent the sloshing waves from impacting the roof of tanks. Since freeboard results in unused storage capacity, many tanks are not provided with the sufficient freeboard. As a result, sloshing waves impact the roof, generating additional forces on the roof and tank wall. This article presents a simple method of estimating these forces.

Calculating Benzene Concentration Emitted During Tanker Loading

Benzene emissions occur during marine vessel loading operations. These emissions are regulated in several countries. Accordingly, we developed a one-dimensional benzene diffusion model advancing in the vertical direction within cargo tanks. Unlike other models, the model presented in this paper is based on a 1/10 scale modeling of eddy diffusion at the liquid surface during initial loading operations and advection under the tank roof during final loading operations. The model input parameters include loading rate, flow rate, cargo tank size, and temperature dependent saturated concentrations. The validity of the model is demonstrated by comparisons with onboard measurements. Other models exist. However, they are based on empirical estimates rather than rational modeling.