External Floating Roof Tanks Research Articles

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.

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.

Volatile organic compounds losses simulation during storage of gasoline

This article analyses the simulation of evaporative VOCs losses from storage tanks of gasoline and its anti-knock additives using TANKS 409d software. The VOCs emissions were estimated for different types of storage tanks: internal floating roof tank (IFRT), external floating roof tank (EFRT) from the one tank farmer of Romanian oil company. The obtained results show quantities of evaporated losses of fugitive VOCs emission approximately 165 t annually, between 01 August 2021 – 31 July 2022. The hazard evaluation of some components (toluene and anti-knock additives) from commercial gasoline has done by the computerize tool ALOHA in different scenarios during the operation of storage tanks. Using MARPOL application software, the pollutant threat zone has been mapped from ALOHA Gaussian model application.

Forecasts for the concentration of petroleum gas leakage diffusion under different liquid level heights of a sealing ring of sizeable floating roof tank

The sealing ring of the external floating roof tank is prone to petroleum gas leakage due to material aging and oil corrosion. Petroleum gas leakage and diffusion easily accumulate above the floating deck. When it is within the explosion limit range, there will be the risk of explosion and fire. To deal with the explosion accident of storage tank caused by the concentration distribution of petroleum gas leakage for the sealing ring, and to study the influence of petroleum gas diffusion and concentration distribution after sealing ring leakage on the control area above the floating deck in the tank farm environment, this paper established numerical models of sealing ring leakage under different liquid level heights for 10 × 104 m3 external floating roof tank. Through numerical calculation, it is found that the diffusion concentration of petroleum gas is related to the wind speed, the range of the control area above the floating deck, and leakage when sealing rings leak at different liquid levels. Through dimensionless analysis, the functional relationship of gas leakage diffusion concentration distribution under different liquid level heights of external floating roof tank sealing rings is verified by numerical calculation results. The results show that the numerical results are consistent with those predicted by the formula.

Modeling Large-Size Round Steel Plates With Surface PEEC Method for Lightning Transient Analysis

The round steel plate is the basic component of the external floating roof tank structure. Modeling large-size round steel plates is essential for analyzing the lightning response of external floating roof tanks. This article builds time-domain equivalent circuit models for round steel plates excited by the lightning current. First, a meshing scheme is presented to generate sector and cylindrical surface cells, which make use of the distribution characteristics of the currents and voltages on the round steel plates. Then, the surface partial element equivalent circuit (PEEC) approach is applied to model the plate. A method of calculating the equivalent surface impedance is proposed, which converts the frequency dependence of the skin effect into impedance based on the time domain. Finally, the time-domain surface PEEC approach is validated by the indirect time-domain solution based on the Fourier transform and the commercial software using the finite-difference time-domain technique, respectively. The comparisons show that the calculation results of different methods are consistent with each other. However, the proposed method in this article can greatly enhance the computational efficiency while meeting the accuracy requirements. It has great significance to the study of lightning protection for external floating roof tank.

Application Analysis of Oil and Gas Safety Active Protection System in the Sealing of Large External Floating Roof Tanks

In the use of large-scale external floating roof storage tanks, the application of sealing performance is very critical, which is related to the safety of storage tanks to a certain extent. In the practical application of storage tanks, it is found that the main cause of fire problems in large oil storage tanks with external floating roof is caused by sealing problems. Therefore, it is very important to deal with the sealing performance of large-scale external floating roof tanks when they are put into use. In this paper, the active safety protection system for large-scale external floating roof storage tanks is analyzed, and its application is analyzed, including its structural design, functional design and working principle design, and its specific application in XX project is put forward.

Determining the emission rates of volatile organic compounds and modeling their dispersion from the petroleum and chemical storage tanks of the largest oil terminal in the southwest of Iran

This study aimed to investigate the air pollution caused by volatile organic compounds (VOCs) with an emphasis on benzene, toluene, ethylbenzene, and xylene (BTEX). Due to surface evaporation from the storage tanks of the largest petroleum and chemical product terminal in the export port of the southwestern Iran, the field measurements of the emission sources were performed using the TANKs 4.0.9d software, and VOC emission modeling was performed using the PHAST software. Among 36 point sources (32 external floating roof tanks and four internal floating roof tanks), the emission rates of the VOCs of the storage tanks were determined using the TANKs 4.0.9d software in the area of 3.8 km2 during 12 months (March 2017-January 2018). The highest rate of VOC emissions from the tanks was observed in July, with the highest temperature and wind speed in the region. According to the results, the total emission rate of the VOCs from the storage tanks was 881.74 ton/year, and the highest emission rate was observed in the external floating roof tanks (865.7 ton/year; 98.18%). The contribution of the internal floating roof tanks was 16.04 ton/year (1.81%), and the highest and lowest VOC emission rates in the export port were observed in the light naphtha tank No. 67 and jet naphtha storage tank (56.73 and 4.18 ton/year), respectively. In addition, the highest and lowest BTEX emission rates from the storage tanks were observed in the gasoline tank No. 62 and jet naphtha tanks No. 93 and 94 (0.37 and 0.05 ton/year), respectively.

The time-to-failure assessment of large crude oil storage tank exposed to pool fire

In large crude oil tank farm, fire is a major primary event in domino effects according to past accidents. The quantitative risk assessment of domino fire accident is a key issue for the accident prevention of large storage tank farm. The most widely used equation for the estimation of the tank's time to failure (TTF) exposed to pool fire is not suitable for 100,000 m3 external floating roof tank. The purpose of this study is to establish simplified models for the calculation of the tank TTF with respect to heat radiation intensity, filling level and the availability of safety protections under different fire conditions. The finite element transient heat transfer modeling of 100,000 m3 external floating roof tank in the case of fire scenarios was performed. The quantitative assessment of safety protection performance in delaying the tank failure under fire conditions was performed according to the simulation results. The application of the TTF equation to case-studies of crude oil tank farm showed the importance of safety protection for the prevention and mitigation of the domino effect. The TTF model provides a basis to the risk management and emergency response in large tank farm.

Emissions of volatile hydrocarbons from floating roof tanks and their local dispersion: Considerations for normal operation and in case of damage

This work investigates the release and dispersion of volatile organic hydrocarbons, which may escape from external floating roof tanks (EFRT) during normal operation or in case of damage. The dispersion will be described using CFD simulations in close range of the EFRT where hazardous areas are assigned. The aim of this work is to investigate which events can lead to emissions in dangerous quantities and to estimate the corresponding likelihood with regard to explosion protection. An emission in hazardous amount is present if the lower explosion limit has been exceeded and if the extent of this emission is not too low. It is discussed in particular whether the used zoning of potentially explosive areas is conservative or over-conservative.

Investigation of the Superposition Effect of Oil Vapor Leakage and Diffusion from External Floating-Roof Tanks Using CFD Numerical Simulations and Wind-Tunnel Experiments

Based on computational fluid dynamics (CFD) and Realizable k-ε turbulence model, we established a numerical simulation method for wind and vapor-concentration fields of various external floating-roof tanks (EFRTs) (single, two, and four) and verified its feasibility using wind-tunnel experiments. Subsequently, we analysed superposition effects of wind speed and concentration fields for different types of EFRTs. The results show that high concentrations of vapor are found near the rim gap of the floating deck and above the floating deck surface. At different ambient wind speeds, interference between tanks is different. When the ambient wind speed is greater than 2 m/s, vapor concentration in leeward area of the rear tank is greater than that between two tanks, which makes it easy to reach explosion limit. It is suggested that more monitoring should be conducted near the bottom area of the rear tank and upper area on the left of the floating deck. Superposition in a downwind direction from the EFRTs becomes more obvious with an increase in the number of EFRTs; vapor superposition occurs behind two leeward tanks after leakage from four large EFRTs. Considering safety, environmental protection, and personnel health, appropriate measures should be taken at these positions for timely monitoring, and control.

Quantitative risk assessment of emissions from external floating roof tanks during normal operation and in case of damages using Bayesian Networks

In this paper, events resulting in an increased or critical emission of volatile organic compounds from external floating roof tanks containing crude and mineral oils with high vapor pressure, e.g. gasoline or naphtha, are investigated. Here normal operations and deviations from normal operations such as tank revision procedures and damages to pipes, seals or deck fittings are included. To record emission-relevant events or damages, a comprehensive literature survey, a Germany-wide survey of companies which use external floating roof tanks and an expert survey were carried out. In addition, the probability of the occurrence of emissions-relevant events was determined and used for risk assessment based on Bayesian networks. This is a well-known method of quantitative risk analysis illustrating and describing causal dependencies. The aim of this work is to show which chains of events can lead to increased or critical emissions of volatile organic compounds. Furthermore, the available data in the literature will be extended by the damage and event rates determined in this work.

Large eddy simulations of wind loads on an external floating-roof tank

Wind load of an external floating-roof tank is analyzed using large eddy simulation (LES). First, the governing equations and a LES solution procedure employing FLUENT software are presented. Subsequently, using two benchmark tank models, the accuracy of LES is examined and the advantages of LES over wind Reynolds-averaged Navier-Stokes (RANS) method in computing the unsteady wind loads and vortex structures around a tank are validated. Finally, using LES, the turbulent flows and wind loads around an external floating-roof tank at varying Reynolds numbers and liquid levels are analyzed. The DSM SGS model was found to have better accuracy when LES is applied to the tank flow. For an external floating-roof tank, the Reynolds number has little influence on the wind load at Re > 106, while the liquid level affects significantly both the wind loads on the tank and the vortex structures in the flow, and the wind pressure on the internal wall distributes more evenly than that on the external wall, due to the recirculation of the flow in the cavity above the roof. In all cases, the pressure on the external floating-roof tank oscillates apparently with time, which indicates the necessity of applying LES to the wind load analysis of tanks.

Experimental measurement of initial evaporation mass flows from gasoline spills and comparison with empirical models

AbstractIn this paper, we investigate the evaporation mass flow originating from spills of gasoline. Large spills of gasoline may form during partial or complete roof sinkings or in the case of perforations at various deck fittings at external floating roof tanks used for the storage. Additionally, spills may form in the retention area in the case of leakages at pipes or at the hull. The aim is to predict the order of magnitude of real‐scale evaporation mass flow. The determined evaporation mass flows will be used in a related project as input values for subsequent dispersion modeling in the vicinity of the tanks. This is relevant for questions of fire and explosion protection as well as for environmental protection aspects in tank farms or refineries, which use external floating roof tanks. The measurements presented in this paper were compared with predictions by empirical models and investigations of evaporations from small floor spills, round‐bottom flask, or from Petri dishes published in the literature. The main goal of this paper is to test the applicability of empirical models to provide reasonable evaporation mass flows as input for CFD dispersion simulations.

Исследование эффективности периферийных уплотнений наружных плавающих покрытий резервуаров

Исследование эффективности периферийных уплотнений наружных плавающих покрытий резервуаров

Prioritizing the Causes of Fire and Explosion in the External Floating Roof Tanks

In the oil industry, many flammable products such as liquid hydrocarbons are usually stored in the atmospheric storage tanks. One type of these suitable tanks is the floating roof tanks. Among the floating roof tanks, external floating roof tanks are mainly used to store large quantities of petroleum products such as crude oil or condensate, gasoline, kerosene. The purpose of this study is prioritizing the causes of fire and explosion in the external floating roof tanks. In this study, firstly, the causes of fire and explosion of the external floating roof tanks were identified and then the obtained variables were scored by the process and safety specialists. In the next step, the causes were weighed and prioritized using the analytic network process method and Super Decisions software. The findings of the study identified 11 main criteria and 71 sub-criteria for fire and explosion of external floating roof tanks. Results revealed that several effective risk factors in the fire and explosion are natural disasters, static electricity, operational error, faulty firefighting system, maintenance error, piping rupture/leak, equipment/instrument failure, open flames, tank crack/rupture, runaway reactions, and sabotage, respectively. This study will help experts to identify the effective risk factors in fire and explosion in external floating roof tanks and their importance. Therefore, they can prioritize and implement the control measures to prevent fire and explosion incidents in external floating roof tanks.

Quantitative risk assessment of direct lightning strike on external floating roof tank

Lightning-related fires and explosions may trigger escalated severe accidents for external floating roof tank (EFRT) farms. Quantitative risk assessment of lightning risk for EFRTs is an effective approach to reduce casualties and property damage. In this research, a quantitative methodology for the risk assessment of direct lightning strike on EFRTs is proposed, in which the risk-attenuating factors are considered by three special sub-models. The first sub-model allows the calculations of the frequencies of major accident scenarios with a small amount of inputs. The second sub-model allows the analysis of the influence of uncertainties on the physical effect due to full surface fire. By the third sub-model, the contribution of automatic firefighting systems and evacuation behavior to the decrease of the damage or death probability can be quantified. The three coherent sub-models constitute the main framework of the methodology in this research, and they are also applicable for other quantitative risk analysis. To demonstrate the applicability of this methodology and the flexibility of the sub-models, a case study is investigated and the contributions of risk-attenuating factors are further discussed. Finally, suggestions are proposed to optimize the lightning risk assessment for EFRTs.

Investigate the Causes of Fires and Explosions at External Floating Roof Tanks: A Comprehensive Literature Review

In recent years, with the development of industry, energy (especially fossil fuels) demand is increasing. This issue is becoming much more serious in the oil industry. The oil industry, and especially refineries, normally uses large storage tanks. Storage tanks in addition to advantages such as saving steel, saving occupied area and cost-effective construction, contain significant amounts of flammable and hazardous hydrocarbon fuels and chemicals. Oil tanks fire and explosion incidents have been common in recent days and occur frequently and repeatedly and are a high threat to life safety. In order to prevent the occurrence of these incidents, it is necessary to identify their causes. The aim of this study was to classify the types of incidents occurred in the floating roof tanks and to determine their causes. In this study, initially, some of fires and explosions occurred in the external floating roof tanks collected by using a large number of various databases. Then, causes of fires and explosions in the external floating roof tanks categorized in 11 criteria and 78 sub-criteria. The results of this study can help the specialists in floating roof tanks design and construction. As well as safety and fire professionals can also use the results from this study to prevent and control fire and explosion accidents in this type of tanks.

Large Storage Tanks Foundation Settlement Structural Mechanics Characteristics Analysis

Foundation settlement is one of significant risks in the process of construction or operation of large storage tanks. In particular, the uneven settlement of the foundation has a significant impact on the safe operation of large storage tanks. In this paper, the Fourier series method is used to extract the harmonic data of large storage tank foundation. Based on the actual measurement foundation settlement data of 100,000 3 m external floating roof tank, the stress and deformation analysis of tank structure is carried out. The stress and deformation of the wall in the dangerous area of the tank is studied, and distribution regulation of the mechanics is revealed. The research results provide some technical guidance for the safety assessment and operation of tank foundation settlement for storage tank enterprise.

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.