Floating Roof Tanks Research Articles

Reduction of seismic sloshing in floating roof liquid storage tanks by using a Suspended Annular Baffle (SAB)

Sloshing in floating-roof cylindrical oil storage tanks subjected to earthquake has been known as a damaging phenomenon, resulting in devastating consequences such as sinking of the roof and/or vast destructive fires. Most of the previous studies have focused on clarifying the mechanism of the dynamic failure of floating roofs subjected to seismic loads. However, applicable remedies have been rarely suggested. In this paper, an innovative and practical method is proposed to reduce the floating roof motion during earthquakes, and an experimental study, conducted by shaking table to show the efficiency of this technique is presented. This new proposed passive control technique reduces the maximum sloshing height by using a Suspended Annular Baffle (SAB), hanging from the floating-roof by some strings with adjusted length, so that the baffle is located as much likely as possible inside the impulsive part of the fluid. The tests, conducted by using various baffle widths, included both sine sweeps and seismic excitations. The experimental results prove that using SAB reduces the maximum seismic sloshing height, in average, to almost 80% and 40% of its values of non-baffled case, respectively, for harmonic and seismic excitations, in a small model tank. Results also show that the presence of SAB reduces the swirling of the floating roof to a great extent. With regard to damping of the convective mode, the results of harmonic tests related to the highest depth of liquid in the tank show that the presence of floating roof increases the damping ratio almost 2.5 times, and the presence of SAB increases it more than 6 times comparing to the case with no floating roof. It is notable that the benefits of the SAB are not limited to only floating roof tanks, and in all cases in which sloshing may have adverse effects, such as elevated tanks, and other types of roofed and even open top tanks employing the SAB can be recommended as a sloshing reduction remedy.

Study on Intelligent Fire Fighting System for Large External Floating-roof Tank

Fire on sealing ring is the main fire form of large external floating-roof tanks. Once fire occurs on the large-scale external floating-roof tank ring, the existing fixed fire extinguishing equipment cannot put out the fire quickly and efficiently, which would result in giant losses. The fire signal can be detected, the fire source can be located automatically and the fire can be extinguished precisely through the combination of the applicable imagine fire monitoring system of the intelligent fireextinguishing system and the automatically fire-fighting gun control system. The capacity of self-explosion prevention and control, fire control and extinguishing of the large scale oil tank will be promoted by extinguishing the fire at the early stage, which will ensure the safety of the operation of the large scale oil tank storage base.

Research on heat transfer characteristic of waxy crude oil during the gelatinization process in the floating roof tank

By means of additional specific heat capacity and momentum source terms methods, the heat transfer characteristic of waxy crude oil during the gelatinization process in the floating roof tank is investigated by numerical simulation. A new kind of division method for the cooling based on the heat transfer mechanism and behavior is proposed. Special concern is taken on the evolution of gelatinization structure and its relationship with the temperature profile. The gelatinous crude oil first generates in the bottom corner of the tank, and there is always the position where the thickest gelatinization layer locates. The integrated gelatinization layer first generates on the top wall, and then it covers the sidewall. The gelatinization interface is not a plane and variates as the cooling proceeds. The temperature profile is constituted by three low temperature regions near walls and a high temperature region in the center of the tank. Moreover, the evolution of temperature profile, positions with the maximal and minimal temperature, as well as the heat transfer coefficient near walls is illustrated in detail. In addition, the effect from environment temperature and oil property on the gelatinization process is also discussed.

Improving Fire Protection of Pontoon Tanks or Floating Roof Tanks

The paper presents research of new solutions to improve fire protection of pontoon tanks or floating roof tanks. Extinguishing efficiency of the subsurface supply system is boosted by a different configuration of the pontoon or floating roof, and also with a cooling system used for oil product evacuation. Efficiency of the proposed methods is more than doubled compared to the existing subsurface extinguishing method.

Research on the variation law of heating temperature field and the effective energy utilization rate of a steam coil for the floating roof tank

ABSTRACTAs per the way of heat transfer and its main characteristics for oil tank, the theoretical model of steam coil heating in large oil storage tanks was established. The Visual Basic language was applied for calculating the temperature field of crude oil in the heating process by the trial method procedure, and the variation law of temperature field and the energy effective utilization rate of oil tank could be obtained. Results show that the temperature of crude oil and the energy effective utilization rate became higher with the increase of the ambient temperature, steam pressure, and the reduction of storage liquid level. The temperature of crude oil near the steam coil became higher with the increase of steam pressure. The oil temperature at the tank outlet presented periodic change, which was affected simultaneously by the steam pressure and the ambient temperature.

Active sloshing control in a smart flexible cylindrical floating roof tank

An exact three dimensional fully-coupled hydro-elastic analysis for transient liquid sloshing in a partially-filled vertically-standing flexible circular cylindrical shell container fitted with a freely floating smart piezo-sandwich thin elastic circular plate is presented. The problem formulation is based on the linear water wave theory, the classical (Kirchhoff/Sanders) thin plate and shell models, Maxwell's equations of electrodynamics, Stokes’ transformation, and eigen-function expansions in cylindrical coordinates. The control action is achieved by combined volume displacement and volume velocity feedbacks (VDF, VVF) implemented in a second order active damping (AD) compensator via two competent evolutionary heuristic optimization techniques that systematically tune the controller gain parameters while constraining the floating panel displacement and control voltage. The uncontrolled and controlled transient responses of the coupled hydro-elastic system under various external disturbances (i.e., a harmonic base excitation, a real seismic event, a severe launch vehicle liftoff event, and a distributed impulsive transverse load on the floating panel) are calculated by means of Durbin's numerical inverse Laplace transform scheme. Moreover, the free vibration characteristics of the coupled fluid/structure interaction (FSI) system are briefly studied. The superior performance of the proposed active floating roof control configuration in effective suppression of the key hydro-elastic parameters (panel displacement, and shell displacements/stresses) is demonstrated. It is also found that, in the current FSI control problem, the Multi-objective Particle Swarm Optimization (MOPSO)-based ADC outperforms the Non-dominated Sorting Genetic Algorithm (NSGA-II)-based method, in terms of convergence rate and computational effort. Limiting cases are examined and the precision of results is verified by comparisons with the existing data as well as with the results produced by a commercial finite element package.

A framework for minimizing domino effect through optimum spacing of storage tanks to serve in land use planning risk assessments

The recent interest in optimizing land use through integrated risk assessment, which intensified after Buncefield oil depot incident in 2005, calls for, among other things, determination of domino effects, which can be severe. The recommended tanks spacing and water application rates by design codes vary widely and are sometimes contradicting, if not subjective. This paper introduces a novel framework to determine the water application rate for protection of storage tanks against thermal radiation from an external non-contacting fire through first principles modeling. This new approach has been applied to assess the appropriate cooling water rate needed for the protection of an existing crude oil tank farm which includes three one-million barrel and two 500,000-barrel floating roof tanks. The tanks are to be protected from the thermal radiation of an adjacent tank with a full surface fire by application of cooling water and in the present arrangement they are so widely spaced that this is only attributable to a generous ‘overdesign’. It has been shown that applying the new approach could have resulted in at least 25% saving in tank farm area.

Buckling of steel tanks under measured settlement based on Poisson curve prediction model

Buckling behavior of large steel tanks under measured settlement has been researched and analyzed in this paper. The settlement prediction model based on Poisson curve is established by applying least square principle and Lagrange quadratic interpolation. Settlement of each measuring point at any time can be obtained applying this prediction model. The discrete settlement data at any time beneath the tank wall is transformed into global settlement expression distributed in the circumferential direction by using the method of Fourier series expansion. Settlement variation with time beneath the tank wall is predicted accurately then. Based on the predicted settlement beneath the tank wall at any time, bucking behavior of the tank is researched by numerical simulation method and the critical buckling time of the tank is predicted. Hydrostatic pressures are applied to inner surface of the tank wall to research the buckling behavior of the tank with different liquid storage. The present method is applied to a fixed roof tank and result shows that the tank wall presents stable linear variation under settlement in initial stage. As time and settlement increase, a typical snap-through buckling occurs to the tank wall, which indicates that the buckling analysis method presented in this paper can be used to predict the buckling behavior of the tank effectively. Buckling behavior analysis of a floating roof tank with the same size and under the same settlement with the fixed roof tank is also made. It indicates that compared to the buckling of fixed roof tanks, the radial displacement on the top of the floating roof tank wall is regarded as the controlling factor to determine the tank failure.

Research on heat transfer characteristic for hot oil spraying heating process in crude oil tank

The finite volume method and standard k−ε turbulence model are used to numerically investigate the heat transfer features of crude oil inside the floating roof tank under the hot oil spraying heating mode. The results indicate that this heat transfer process has the essential features of the thermal buoyancy jet flow. The jet flow is divided into the strong buoyancy, weak buoyancy and common buoyancy process according to Froude number of the jet flow. Bigger Froude number of the jet flow indicates stronger heat exchange strength and more uniform distribution of oil temperature. Smaller Froude number indicates stronger buoyancy, weaker heat exchange strength and more obvious hierarchical distribution feature of the oil temperature inside the tank. Two indices (efficiency and uniformity) are introduced and examined which could be of practical usage. According to the simulated result, higher nozzle speed and proper spraying temperature which results in a lager Froude number can achieve better heating effect by taking two previous indices as evaluation criterion. For the practical engineering usage, the spraying temperature and nozzle speed should be adjusted synchronously based on Froude number.

Quantitative risk assessment of external floating roof tank areas based on the numerical simulations

Large floating roof tanks usually contain a large amount of flammable liquids which can lead to catastrophes. This study analyzes accident scenarios based on 88 large external floating roof tank accident case analyses.Fire dynamics simulator(FDS)is used to compute the heat flux distribution under a rim seal fire,a full surface fire,and a bund fire.The personal vulnerability model is then used to calculate the individual risk based on the heat fluxes.The effect of wind on the risk distribution is discussed and the safety distances for firefighters are identified.The results provide useful reference for firefighting.

Measured and estimated benzene and volatile organic carbon (VOC) emissions at a major U.S. refinery/chemical plant: Comparison and prioritization

Estimates of emissions for processes and point sources at petroleum refineries and chemical plants provide the foundation for many other environmental evaluations and policy decisions. The most commonly used method, based on emission factors, results in unreliable estimates. More information regarding the actual emissions within a facility is necessary to provide a foundation for improving emission factors and prioritizing which emission factors most need improvement. Identification of which emission factors both perform poorly and introduce the largest error is needed to provide such a prioritization. To address this need, benzene and volatile organic compound (VOC) emissions within a major chemical plant/refinery were measured and compared with emission factor estimates. The results of this study indicate estimated emissions were never higher and commonly lower than the measured emissions. At one source location, VOC emissions were found to be largely representative of those measured (i.e., the catalytic reformer), but more often, emissions were significantly underestimated (e.g., up to 448 times greater than estimated at a floating roof tank). The sources with both the largest relative error between the estimate and the measurement and the largest magnitude of emissions in this study were a wastewater treatment process, an aromatics concentration unit and benzene extraction unit process area, and two sets of tanks (sets 7 and 8). Emission factors for these sources are priorities for further evaluation and improvement in this chemical plant/refinery. This study presents empirical data that demonstrate the need to validate and improve emission factors. Emission factors needing improvement are prioritized by identifying those that are weak models and introduce the largest error in magnitude of emissions. The results can also be used to prioritize evaluations of the emissions sources and controls, and any operational conditions or erroneous assumptions that may be contributing to the error.Implications: Emissions measured at processes and point sources at a major petrochemical plant complex were compared to emission factor estimates. The results of this study indicate estimated emissions were never higher and commonly lower than the measured emissions. The comparison was used to prioritize emission factors needing improvement by identifying those that were weak representations and that introduce the largest error in emissions. The results can also be used to prioritize evaluations of the emissions sources and controls, and any operational conditions or erroneous assumptions that may be contributing to the error.

믹서의 가동 수 및 각도 변화에 따른 유동형 지붕 탱크의 유동특성

In this study, there are 6 mixers that are installed in a 600,000 barrel tank. We identified internal flow characteristics of floating roof tank with varying the number of operation from 4 to 6 because mixer is a variable that influence flow characteristics of the tank. And while varying an angle from Right 60°, Right 30°, Left 30° to Left 60°, we identified internal flow characteristics of the tank. As a result, maximum velocity of flow was 0.02m/s stationarily when we changed the number of operation from 4 to 6. Maximum velocity of flow by change of an angle was from 0.42m/s to 0.47m/s. Therefore, we identified that these factors don

Heat Loss Test and Estimate for the Large-scale Floating Roof Tank

The heat loss and surface temperature of the top surface and sidewall of large-scale floating roof tank is tested by the heat flow meter and surface temperature method. Based on the test data, the heat loss from the top surface is about twice more than that of the sidewall which means the top surface is the weakest insulation part of the floating roof tank. On the surface, the heat loss profile is in accord with the surface temperature distribution. Special attention is given on the calculation of thermal conductivity for the top surface and sidewall which finally deduced the total heat transfer coefficient of large floating roof tank. Moreover, the heat loss of floating roof tank in different working conditions is predicted. According to the calculation results, the level of 6m is regarded as a critical level determining the heat loss. And the centralization storage of oil is a more energy conservation storage pattern.

Research of Curve Fitting Method on the Measured Settlement of Tanks

The settlement data of oil storage tanks made of steel are measured by the measurement points located around the base of the tank wall. The measured settlement data need to be curve fitted in order to reflect the settlement distribution around the whole tank wall base. Considering about the disadvantage of measured settlement data treatment methods on tanks in current standards, an optimization method of curve fitting on the measured settlement data is presented. The Fourier series expansion is used to analyze the measured settlement data, the fitting curves and mean square error according to different order are obtained. The fitting curve with minimum mean square error is selected as the most appropriate one that reflects the actual displacement of the tank base. The optimization method of curve fitting present is applied to analyze the measured settlement data obtained from the floating roof tank and the fixed roof tank. Results show that different effects can be obtained with different order of the fitting curve. Curve fitting referring to different order is necessary to the measured settlement data in actual engineering in order to find the most appropriate one that reflects the real tank base displacement distribution.

多重動吸振器を用いた浮屋根式タンクに生じるスロッシングのパッシブ制御

多重動吸振器を用いた浮屋根式タンクに生じるスロッシングのパッシブ制御

Study on Floating Roof Tank Nitrogen Lightning Protection System

In order to study the feasible floating roof tank lighting protection technology, this paper put forward making oxygen concentration remain below 8% through inerting sealed space, thus reduces fire risk. By analyzing the oxygen concentration change after injecting nitrogen into the sealed space, sets up the relationship between the oxygen concentration change and nitrogen injection volume. Mean while, through the experiment when the sealed space maintains the micro positive pressure, established a formula about the nitrogen flow and micro positive pressure, which can obtain nitrogen amount directly under different wind velocity and lightning time to complete inerting. Finally, design a nitrogen protection system which can protect lighting fire, and can put out floating roof tanks initial fire.

Financial Analysis of the Internal Floating Roof Installation in Gasoline Gasohol (E10, E20) and Ethanol Tank

Vapor emission in vertical fixed roof tank (VFRT) and internal floating roof tank (IFRT) of oil tanks was evaluated by emission estimation procedures. This report presents the results of a comparison of standing losses between actual data with calculation data in the fuel tanks of various sizes (using 2013 data from diameter 5 to 50 meter). The volatile oil, gasoline, gasohol (E10, E20) and ethanol in VFR and IFR was evaluated by Tank 4.0d, which is evaluated program. The program shown that the calculated evaporation was close to the emission actual data only oil tank that didn’t mix ethanol in VFRT. But the IFRT, the calculated evaporation data is not close to the emission actual data. Finally, financial analysis of the IFR installation in gasoline gasohol (E10, E20) tank shown the mostly of tank have value for investment criteria and comply with company rule.

Potential Damages of Atmospheric Storage Tanks due to Volcanic Ash Aggregations in Presence of Water

Recent studies of the effects of the volcanic ash fallout on storage tanks have shown the potential causes of failure for both fixed and floating roof tanks. The vulnerability of these facilities has been defined through the estimation of threshold values of the ash load on their roofs and exceedance probabilities of these limits. It has been observed that the amount of the overhead on the roof is much greater when the ash is saturated with rain because of the formation of aggregates. This paper aims to analyse the influence of this phenomenon on the potential damage of tanks located in the area surrounding Mt. Etna.

Transient Cooling of Waxy Crude Oil in a Floating Roof Tank

The transient cooling of waxy crude oil stored in a floating roof tank located in alpine region is studied by means of numerical simulation, accomplished with a two-dimensional model in cylindrical coordinates with the finite volumes method. The typical evolution of transient natural convection and temperature distribution is investigated which can be divided into four stages. For the transient natural convection, it is concluded as the formation, expansion, degradation, and vanishing stage, along with it is the evolution of temperature field regarded as the local cooling, integral cooling, the thermal stratification, and heat conduction course. Special attention is given to the solidified process of waxy oil and its influence on the cooling process of crude oil. Moreover, the effect of tank size, the temperature gradient between oil and ambient, viscosity, and Cp of waxy crude oil on the cooling rate is investigated. The main characteristic of cooling process obtained from numerical results shows a good agreement with the temperature test results from a large floating tank in the oil depot.

Study of Charging Nitrogen to External Floating Roof Tank to Prevent Rim-seal Fires from Lightning

It is estimated that 95% of rim seal fires are caused by lightning strikes. To avoid rim-seal fires caused by lightning, the existing methods mainly focus on the use of secondary sealing to reduce volatilization of oil and the electrical connections measures such as air terminals, deflectors, grounding device, discharge shunts and scalable grounding device to avoid sparks caused by lightning current. But these devices can’t eliminate the spark generation thoroughly. A new method charging nitrogen to external floating roof tank seal ring is proposed to prevent rim-seal fires from lightning. In this paper, the safe oxygen content is set as the goal to charge nitrogen. An annular nitrogen charging pipe network is designed and its reliability is verified by experiment. The time of filling nitrogen to the seal ring of an external floating roof tank with the capacity of 10×104 m3 at the rate of 63.38 m3/h to reach the nitrogen charging goal is proved within the time of lightning warning through experiment. And this experiment can provide some reference to the application of nitrogen charging.