Roof Tanks Research Articles

Investigating the Catastrophic Roof Failure of a Fatty Acid Storage Tank: Causes, Mechanisms, and Safety Implications

This paper investigates the catastrophic failure of the roof weld on a carbon steel storage tank at a Fatty Acids plant, which was attributed to pressure overload. The incident resulted in the tank's roof, weighing over 5 tons and spanning 8 meters in diameter, being propelled 25 meters from the tank. Despite installing several safety devices, including pressure regulating valves, pressure indicator controls, and pressure vacuum relief valves, inadequate maintenance led to their malfunction. This study examines the mechanisms and causes behind the failure, highlighting the crucial role of regular maintenance in ensuring the functionality of safety instruments. While neither toxic nor flammable, the plant's compressed air system poses a significant hazard due to the energy stored at slight overpressure, necessitating vigilant management by the safety department. The findings underscore the importance of robust maintenance strategies and procedural adherence to prevent similar incidents, enhancing industrial storage systems' overall safety and reliability.

Heat transfer research on the cooling process of waxy crude oil storage in the vault tank based on VOF model

This paper focuses on the static cooling process for waxy crude oil stored in dome roof tanks. For the three phases of gas on top, liquid crude oil, and bottom water in storage tank, the VOF method is used to describe the evolution of physical quantities at the “oil–water”/“oil–gas” interface. The porous medium method is used to quantitatively characterize the sol–gel conversion process for waxy crude oil. A physical and mathematical models are established to describe the flow-heat transfer coupling behavior of the three-phase medium of crude oil, gas on top, and water at the bottom of the dome roof tank. In terms of the overall cooling process,The gas at the top of the tank has the simplest and fastest physical field evolution. It has the most uneven distribution (average temperature variance of 4 °C2), the strongest flow (average flow velocity of 0.4 m/s), the highest cooling rate (0.632 °C/h), and the lowest temperature (14.84 °C at the end). Its physical field is influenced by both the atmosphere and crude oil. The evolution of the physical field of crude oil is the most complex. It lags behind the gas at the top of tank and is directly effectted by it. Based on the evolution characteristics of the flow field of crude oil, the cooling process is divided into three stages: Stage I (0–––10 h) is the stage of convection generation and evolution in the crude oil region; Stage II (10 h − 34 h) is the stage of convection stability in the crude oil region; Stage III (after 35 h) is the stage of flow field transformation of crude oil. In stages I and II, the flow and momentum exchange at the oil–gas interface are significant. Crude oil is jointly influenced by the natural convection of the gas at the top of the tank and its own natural convection, forming a counterclockwise large vortex structure. The low-temperature area is near the central axis boundary of storage tank, oil–gas interface, and tank wall. The high-temperature area is within a range of 0.1 m − 3.3 m from the tank wall. After entering stage III, the flow and momentum exchange at the oil–gas interface weaken. The flow field of crude oil is only controlled by its own natural convection and transforms into a clockwise large vortex dominated. The low-temperature area is concentrated in the enclosed area of “oil–gas interface − tank wall” and “oil–water interface − tank wall”. The temperature field changes accordingly. Eventually, the high-temperature area is concentrated in the area slightly above the center of the tank. The physical field evolution of bottom water lags behind crude oil and is most unstable. Its cooling rate is 0.164 °C/h, slightly higher than crude oil’s 0.157 °C/h. The temperature is always slightly lower (33.47 °C at the end), and the physical field is the most uniform (average temperature variance of 0.0003 °C2), affected by the tank bottom environment and liquid crude oil.

Thermal-mechanical coupling characteristics of large-scale molten salt storage tanks under stable operating conditions with varying liquid levels

The large-scale molten salt storage tank is a critical component of the thermal storage system employed in concentrating solar power (CSP) plants. The storage tank is subjected to complex conditions, including high temperature, fluctuating hydrostatic pressure, and thermal stress. Therefore, it is imperative to investigate the thermal-mechanical coupling characteristics of the tank during stable operation under varying liquid levels to comprehensively understand its behavior. The study commences by establishing thermal and stress analysis models for the tank, laying the foundation for subsequent investigation. Subsequently, a comprehensive thermal-mechanical coupling model is constructed using a sequential coupling approach, enabling a more accurate representation of the system's behavior. Finally, an in-depth study is conducted to explore the thermal-mechanical coupling characteristics of storage tanks at various liquid levels. The results indicate that radiation emitted by high-temperature air, confined in the top space of the tank, induces a temperature differential of approximately 5 °C between the tank's roof and the molten salt confined within it. Furthermore, heat loss from the roof accounts for 53 % of the overall heat loss. Thermal stress analysis of each weld seam connecting the tank into an integration reveals that the inner surface experiences tensile stress, while the outer surface undergoes compressive stress, primarily influenced by radial stress. Under the influence of thermal-mechanical, the coupling effect leads to compressive stress in the form of thermal stress, resulting in a decreasing trend in stress on the inner surface of the weld seam. The radial compressive stress on the outer surface reaches approximately 140 MPa, while the tank wall is primarily subjected to circumferential forces. The temperature exerts a negligible impact on the stress of the tank wall, yet it significantly affects its deformation. The stress evaluation of hydrostatic pressure and thermodynamic coupling under different liquid levels is carried out, and the results meet the strength requirements.

Numerical Study on the Influence of Various Design Variables on the Behavior Characteristics of Oil and Gas in Internal Floating Roof Tanks

Numerical Study on the Influence of Various Design Variables on the Behavior Characteristics of Oil and Gas in Internal Floating Roof Tanks

Identification of patterns of the stress-strain state of a standard plastic tank for liquid mineral fertilizers

In this study, using the method of probabilistic deterministic planning (PDP), the optimum design parameters of a standard polyethylene tank used worldwide for transporting liquid mineral fertilizers (LMF) were determined. By the finite element method, the effect of the density of liquid mineral fertilizer, tank wall thickness and four motion modes (braking, acceleration, jump and landing) on the strength of standard polyethylene tanks was studied. According to the results of the study, the five most informative areas in the tank design were identified, for which the values of maximum stresses (σmax) were obtained: filler neck, pockets, walls, tap-in points and wall transition to the tank roof. As the LMF density increases, σmax in the tank increases linearly. Increasing the tank wall thickness by 1.5 times reduces the maximum stresses by 30 to 50 %. It was found that motion mode has a significant effect on the stress-strain state of a standard tank. The “heaviest” mode for a standard tank is “braking”. The “acceleration” motion mode causes σmax of no more than 60 % of the “braking” mode values. The “lightest” mode is “landing”, in which σmax is no more than 28 % relative to “braking”. Based on the PDP method, equations were derived for calculating maximum stresses depending on LMF density, wall thickness and motion mode of the tank. Nomograms were built that make it possible to quickly determine the wall thickness of a standard tank without calculations, depending on external factors. The results of the study can be used in practice when designing safe and durable tanks for transporting liquid mineral fertilizers.

Wind-induced response of the flexible floating roofs of large storage tanks considering liquid sloshing

Most large storage tanks are built in coastal ports and are prone to strong wind. The deformation and stress fatigue problems of the flexible floating roof of tanks under wind loads are worthy of attention. However, current research and standards mainly focus on seismic excitation, and the effect of wind loads is rarely discussed. Therefore, this paper derives a solution for the response of single-deck floating roofs under wind loads considering the liquid sloshing in storage tanks. The displacement of floating roof and velocity potential of liquid are expressed by modal superposition, and the wind pressure is measured by wind tunnel tests and expanded by Fourier series. The vertical displacement, Von Mises stress and hydrodynamic pressure of the floating roof are calculated for various liquid levels. The difference in response and fatigue damage between single-deck and double-deck floating roofs are discussed and the effect of various size parameters is analyzed. The results show that the response increases significantly with the increase of liquid level. Large Von Mises stresses are generated at the junction between the deck and the pontoon due to the difference in stiffness, which may lead to fatigue failure of the weld. A sufficiently wide pontoon or the choice of a double-deck floating roof can effectively avoid stress concentration. The proposed method can quickly estimate the wind-induced response of floating roofs and is expected to be applied to large-scale parametric design and reliability analysis.

Structural behaviour of single-deck floating roof tanks subject to seismic loading

During a seismic event, fluid storage tanks are subject to sloshing phenomena; their effect on the structural components of the tanks is one of the main aspects to be considered during the design. The movement in successive modal forms of the roof-fluid system determined by the earthquake can cause severe damage to both the containment shell and the floating roof. The fluid-structure interaction imposes extremely complex out-of-plane deformation fields, mainly in the presence of floating roofs with lower flexible resistance. Such deformations can cause severe structural damage and subsequent catastrophic events such as those experienced in the past in Japan and Turkey. In fact, recently recorded earthquakes in Japan and Turkey, characterized by oscillation periods between 3 and 8 sec (long-period ground motion), compatible with the natural first and second slosh frequencies of the fluid-structure system, led to conspicuous problems of instability failure with the consequent sinking of the floating roof. These events dictated a new starting point for the research into the seismic behaviour of roof-fluid-tank systems.

Analysis of the electromagnetic effects on the large floating roof oil tanks by nearby lightning strike based on TLM

Lightning fire is one of the biggest dangers for chemical and petrochemical storage tank farms, particularly in floating roof oil tanks (FROTs). To improve the lightning protection of FROTs, the process of floating roof tanks affected by lightning is analyzed. Lightning inductive effects can result in the undesired operation of the above-ground storage tank equipment and endanger exploitation safety. The time domain finite element analysis based on the transmission line model (TLM) method is regarded as a numerical technique to solve field problems by implementing circuit equivalents. This study aims to analyze lightning strike characteristics using the Heidler current function and simulate electromagnetic field strength (EMFS) distribution and surface current density (SCD). Calculation of minimum possible effective strike distance and shielding effectiveness (SE) is performed. Parametric modeling ensures accurate modeling of the roof's bypass conductor to the shell. By utilizing the Parameter Sweep technique, multiple simulations can be carried out with varying structure parameter values. This approach ensures optimal efficiency and accuracy in the results obtained.

Flow coupling analysis and evaluation of different working conditions for crude oil storage tanks under dynamic heating

AbstractDuring periods of sharp demand increase, there is a need for significant expansion in the fundamental requirements for crude oil storage. As demand rapidly escalates, the prerequisites for crude oil storage necessitate substantial expansion. To scientifically and effectively reduce energy waste associated with heating oil, it is essential to study the heating methods and efficiency of crude oil storage tanks. Considering environmental temperature, solar radiation, and the physical properties of the oil, we have proposed a new heating model to elucidate the dynamic heating process of large floating roof storage tanks equipped with coils. Computational fluid dynamics (CFD) software was used to analyze the impact of the dynamic heating model on the temperature and velocity fields within the floating roof tank, taking into account different initial oil temperatures, oil levels, wind speeds, and types of crude oil during the winter heating process. Additionally, the research suggests the optimal maintenance heating temperature and duration for crude oil storage tanks during the winter season, introducing heating efficiency and inhomogeneity of temperature field as two evaluation metrics to compare the advantages of the dynamic heating method over traditional heating methods. This study provides fresh insights into the coil heating domain in crude oil storage tanks.

Remotely sensed above-ground storage tank dataset for object detection and infrastructure assessment

Remotely sensed imagery has increased dramatically in quantity and public availability. However, automated, large-scale analysis of such imagery is hindered by a lack of the annotations necessary to train and test machine learning algorithms. In this study, we address this shortcoming with respect to above-ground storage tanks (ASTs) that are used in a wide variety of industries. We annotated available high-resolution, remotely sensed imagery to develop an original, publicly available multi-class dataset of ASTs. This dataset includes geospatial coordinates, border vertices, diameters, and orthorectified imagery for over 130,000 ASTs from five labeled classes (external floating roof tanks, closed roof tanks, spherical pressure tanks, sedimentation tanks, and water towers) across the contiguous United States. This dataset can be used directly or to train machine learning algorithms for large-scale risk and hazard assessment, production and capacity estimation, and infrastructure evaluation.

Time-dependent earthquake-fire coupling fragility analysis under limited prior knowledge: A perspective from type-2 fuzzy probability

Earthquake-triggered fire domino scenarios (E-FDSs) arise frequently from the interaction between earthquakes and chemical installations, resulting in catastrophic multi-hazard coupling events. The complicated mutually amplified phenomena between natural disasters and chemical accidents significantly aggravates the escalation of domino accidents, which has posed great challenges for modeling and preventing E-FDSs. Under this impetus, this work proposes an advanced type-2 fuzzy probabilistic methodology to obtain the time-dependent failure probability of steel cylindrical tanks (SCTs) subjected to the earthquake-fire sequence. To cope with the limited prior knowledge on E-FDSs, a basic universal is established to describe the fire resistance attenuation caused by the seismic damage. The coupling failure criterion of SCTs is formulated by a type-2 fuzzy time-dependent limit state equation. A credibility-based stochastic simulation algorithm is developed for the hybrid uncertainty analysis (combining ambiguity and stochasticity). The proposed methodology is validated by case studies of a 5000 m3 fixed roof tank. Compared to the existing accident probability model, the proposed methodology can not only capture the fire resistance attenuation caused by the seismic damage but also provide a dynamic estimation of tank failure probability with respect to the fire exposure time. The proposed methodology can effectively and dynamically capture the accident evolution process, which in turn helps mitigate and prevent the spatiotemporal propagation of domino effects.

Влияние скорости воздушного потока на тепловое излучение от углеводородного пожара в резервуаре для хранения нефти

Purpose. The article assesses the effect of air flow velocity on the intensity of thermal radiation from a fire in a vertical steel tank with a floating roof of 65 000 m3 capacity (VSTWFR-65000) with crude oil. The indicators of hazardous fire factors - open flame, smoke and temperature at different wind speeds – have been studied. Methods. The method of numerical modeling in the Fire Dynamics Simulator software package, as well as the method of processing the obtained research results have been used in the study. Findings. The dependence of the flame inclination angle at different air flow speeds has been obtained. The simulation results have been shown: smoke distribution at different wind speeds, as well as temperature change at a distance from the fire source depending on the air flow velocity. Research application field. The results of the study can be used in the development of design documentation for measures to ensure fire safety of a tank farm with floating roof tanks, as well as in adjusting fire extinguishing plans. Conclusions. Based on the simulation results it has been found that with an increase in the air flow velocity the intensity of thermal radiation initially increases and then decreases. It has been found that at an air flow velocity of 9 m/s the maximum thermal radiation reaches 23.43 kW/m2 at the nearest point of the adjacent tank in the projection from the central axis of the burning tank. At an air flow velocity of 6.5 m/s the temperature at the top of the adjacent tank reaches 176 °C, and at 9 m/s – 426 °C, which is higher than the autoignition temperature of oil, which is within 222–256 °C, there by creating a threat of fire spread. The study has defined the maximum distances from the burning VSTWFR-65000 for the safe presence of people, amounting to 47.3; 48.9; 50.2; 53.4; 55.7; 56.8; 59.4 m for wind speed of classes 0, 1, 2, 3, 4, 5 and 6 respectively.

Explosion damage effects of aviation kerosene storage tank under strong ignition

In order to study the blast damage effects of aviation kerosene storage tanks, the out-field explosion experiments of 8 m³ fixed-roof tanks were carried out. The fragments, shock wave and fireball thermal radiation of the tank in the presence of bottom oil, half oil and full oil, as well as empty tank, were investigated under internal explosion by various TNT charge contents (1.8 kg, 3.5 kg and 6.2 kg). The results showed that the tank roof was the only fragment produced, and the damage forms could be divided into three types. The increase of TNT charge content and oil volume enlarged the deformation of the tank, while the hole ratio presented a trend of increase first and then decrease. The Hr, max and Vmax values positively increased as increasing the TNT charge content and oil volume (from empty to half oil), but decreased in full oil. The Pmax values had a progressive increase with the increment of TNT charge content, but not the case with the increase in oil volumes. The development of fireball was divided into three stages: tank roof ‘towed’ flame, jet flow flame tumbling and rising, and jet flow flame extinguishing. The Dmax and Hf, max values both increased as increasing TNT charge content and oil volumes. The oscillation phenomenon of fireball temperature was observed in the cooling process. The average temperature of fireball surface was positively correlated with TNT charge content, and negatively correlated with oil volumes.

The Reliability Assessment of Firefighting Systems Using Fuzzy Bayesian Network in the Floating Roof Tanks of a Petrochemical Company

The Reliability Assessment of Firefighting Systems Using Fuzzy Bayesian Network in the Floating Roof Tanks of a Petrochemical Company

ANALYSIS AND IDENTIFICATION OF FACTORS CAUSING FLOODING AT SUKABUMI CITY TERMINAL

The plumbing system is an inseparable part of a multi-storey building. The plumbing system at the hotel is used to provide clean water and hot water needs. To meet the need for clean water in the design of an 8 floors building with a total of 45 inhabitants, an average number of 2,706 people per month and 100 visitors per day, a ground water tank capacity of 404.5 is required. m3 / and for the top water tank (Roof Tank) used a water reservoir of 21.59 m3. Based on the results of calculations for hot water needs where the toll of hot water needs per day is 12,900 liters including heat loss with 100% hotel occupancy and for heating time, it is obtained 9.79 hours / day using 2 units of heater heater 21.04 Kw

Experimental investigation of flame behaviors of turbulent diffusion flames with different ullage heights

This work is aimed examine the effect of ullage height (tank roof to fuel surface) on the flame behavior of turbulent diffusion flames. A series of experiments with eight ullage heights (h = 0–28 cm) were conducted. Propane was issued from a gas burner (D = 20 cm) with different fuel supply rates. Experimental results showed that the total flame consists of an upper flame (Lupper, outside the tray) and a down-reaching flame (Ldown, inside the tray). It was found that Ldown decreases with fuel supply flow rate and there is a critical fuel supply flow rate (Q˙s,c), independent of the ullage height, above which there is no down-reaching flame. Depending on the ullage height and fuel supply rate, the flame behaviors can be divided into three regimes: (Ⅰ) restricted down-reaching, (Ⅱ) free down-reaching and (Ⅲ) no down-reaching. Based on the dimensionless analysis, correlations were developed to predict the down-reaching, upper, and total flame lengths, respectively. These correlations were validated against the experimental data in the paper and the previous literature. The present results are of importance to understand the flame behaviors for the burning of fires with large ullage heights and provide guidance in risk assessment of tank fires.

Cloud cover and expected oil returns

Satellites can “sense” oil inventory, but cloud cover prevents observation, which reduces the flow of information into the oil market and creates uncertainty about information availability. The effects of the availability of such information on oil prices need to be thoroughly explored. Therefore, using time-series prediction, this paper examines the effects of the availability of satellite-based information on oil returns. The cloud cover above the floating roof tanks in major oil storage areas is measured to predict oil returns through regression approaches. The empirical results indicate that higher cloudiness in a week leads to lower oil returns in the following week. The predictive ability of cloudiness is significant from both in-sample and out-of-sample perspectives. The ability of cloudiness measures to predict oil returns can be explained by information uncertainty and information flow channels. The findings have important implications for asset pricing and risk management using big data.

A novel dynamic risk assessment method for the petrochemical industry using bow-tie analysis and Bayesian network analysis method based on the methodological framework of ARAMIS project

In order to obtain the actual risk level and assess the performance of the safety barriers, bow-tie (BT) approach proposed by ARAMIS project is applied to accident scenarios identification and risk analysis, but this approach has limitations in dynamic risk assessment due to its static nature. This study takes the floating roof tank as the research object, and further proposes a dynamic risk assessment method based on the methodology proposed by the ARAMIS project. The BT model of the major leak of external floating roof tank was established by comprehensive consideration of the barrier functions and the logical relationship between causes and events. Furthermore, The BT to Bayesian network (BN) mapping algorithm was proposed to characterize system dynamics and uncertainty. The analysis results show that not only the dynamic assessment of the risk level for safety barriers in different states can be implemented, but also whether the current overall safety protection capability of the system is sufficient can be judged. The proposed method and findings can help managers identify safety barriers that play a key role in various accident risks, and provide effective support for risk management decision-making and implementation of preventive strategies.

Modified analytic hierarchy process for risk assessment of fire and explosion accidents of external floating roof tanks

AbstractTo ensure the safe operation of external floating roof (EFR) tanks, it is important to conduct risk assessments for fire and explosion accidents. In this study, we develop a modified analytic hierarchy process to overcome the subjectivity in traditional analytic hierarchy analysis, improved analytic hierarchy process, and fuzzy fault tree analysis. We propose a parameter with a correction factor: the role of the parameter in the model can be gained from further modifying the structural importance of each basic event so as to overcome the subjectivity in traditional analytic hierarchy analysis, improved analytic hierarchy process, and fuzzy fault tree analysis. The judgment matrix for the analytic hierarchy process is constructed based on the modified structural importance of each basic event in a fault tree. The weight factor for each index to the top goal, combined with the fuzzy comprehensive assessment method, is adopted to conduct risk assessments for the fire and explosion accidents of EFR tanks.

Thermo-economics evaluation of crude oil heating arranged with finned coil in floating roof tank

The crude oil in the floating roof tank is troubled by the problem of gelling at low temperature which eventuate the storage of crude oil needs to be assisted by coil heating technology. However, the low heating performance of the technology restricts the benefits of crude oil storage due to the limited heat exchange area between coil and crude oil. A finned coil heating technology is proposed to address the above issues. The influence of the fin number and the inclination angle on the heating effect of crude oil is analyzed by FLUENT software. The results indicate that increasing the number of fins has a more significant effect on improving crude oil temperature than adjusting the inclination angle. The increase in the number of fins shows a nonlinear relationship with the increase in crude oil temperature, and there is an optimal combination for coils with different fin numbers and different inclination angles. From the perspective of thermos-economics, the optimal arrangement is the coil with 2 fins inclined at 60°, which can increase the crude oil zone average temperature by 2.83% (1.021 °C), and reduce the temperature inhomogeneity by 6.31%, as well as increase the cost saving by 91.65%, compared with the bare coil inclined at 0° (i.e. existing engineering formation). This paper is of great significance for ensuring the safe storage of crude oil.