Large Oil Tankers Research Articles

Research on the gravity sedimentation law of watery crude oil in large oil tanks

ABSTRACT Based on field survey data, a numerical simulation method that combines an indoor settling experiment with the Mixture multiphase flow model and the Population Balance Model (PBM) was adopted in this article to study and analyze the sedimentation law of water-containing crude oil in a tank under different initial particle sizes and different continuous-phase viscosities. The results indicate that the maximum error in the comparison of the water content changes at different positions in the sedimentation cylinder after 1 h with experimental values is approximately 8.34%, confirming the precision of the developed settling model. When the initial particle size of liquid droplets in the tank increases from 8 μm to 64 μm, the maximum water content in the tank increases by 1.115%, and the magnitude of the increase in the average droplet size decreases by 90%. As the viscosity of the oil increases (from 35.26 mPa · s to 77.77 mPa · s), the maximum water content in the tank decreases by 1.331%, while the height of the stable water content region increases by 13.2%.

SHORT INTRODUCTION ON PRESENT DESIGN AND TRENDS REGARDING

This paper covers some aspects regarding present technology used in large crude oil carriers design and operation, as well as requirements regarding energy management on board. Obviously, due to complexity of such subject, there cannot be an exhaustive presentation. It is intended as a mere starting point for further discussion and research regarding possibilities to improve vessel’s general energy efficiency, including ways of using non-conventional and renewable energy, with due regard to specific trading routes involving large oil tankers. Some practical figures achieved typically on a Very Large Crude Oil Carriers engaged in international voyages are presented. A brief explanation on Energy Efficiency Index (EEI) and Carbon Conversion Factors (CF), as accepted by IMO, is also included. Work may be continued with further theoretical research in energy efficiency improvement on board such vessels. The article is structured in five parts: Introduction, Main Particulars of Large Tankers, Oil Tankers Outfitting, Energy Management Plan and Conclusion.

Pitching Stabilization Control for Super Large Ships Based on Double Nonlinear Positive Feedback under Rough Sea Conditions

Due to the rapid development of a global navigation satellite system and the rapid growth of ships, the traditional control algorithms are not suitable; hence, the longitudinal rocking phenomenon generated by external disturbances is more serious when a ship is sailing. This paper takes a mathematical model of the super large oil tanker “KVLCC2”’s longitudinal motion as the controlled plant, establishing a multi-input multi-output instability control system, using the root trajectory shaping method and a weighting matrix to ensure the stability of its transfer function’s mathematical model. An improved closed-loop gain-shaping algorithm is utilized to design a simple robust controller. And a dual nonlinear positive feedback control algorithm is added to the control system to further improve the controller’s pitching stabilization performance and reduce the controller’s output energy. In order to verify that the controller has a consistently strong robustness, simulation experiments are carried out by adding a level 6, 7 and 8 wind wave model and a perturbation link to the control system, respectively. The results show that when the value of the hysteresis constant is taken as 0.25, the output values of the heave displacement and the pitch angle are greatly reduced, and the longitudinal rocking phenomenon is significantly improved. The dual nonlinear positive feedback control algorithm enhances the ship’s pitching stabilization control capability and further reduces the controller’s output energy, which provides technical support for the smooth and efficient sailing of super large ships under changing sea conditions. Combined with a global navigation satellite system, this algorithm provides a new method for pitching stabilization control of super large ships.

Numerical Investigation of Oblique Currents’ Effects on the Hydrodynamic Characteristics of Ships in Restricted Waters

The influence of oblique currents in narrow and shallow channels causes the fluid flow around ships to become complex. To analyze the hydrodynamic characteristics of a ship in such channels, it is essential to examine the influence of oblique currents on the ship’s hydrodynamic characteristics. In this study, current direction, ship speed, current speed, and water depth were identified as determinants affecting the hydrodynamic characteristics of a ship. Numerical simulations were conducted on a large oil tanker to investigate the effects of these factors on the ship’s hydrodynamic characteristics. The viscous fluid flow was modeled using the unsteady Reynolds-averaged Navier–Stokes (URANS) equations in conjunction with the k-ε turbulence model. The URANS equations were discretized using the finite volume method. The numerical results indicate substantial differences in the hydrodynamic characteristics of ships under oblique current conditions compared to still-water conditions. At a current direction of β = −45°, the direction of the sway force is consistent with that of still water’s sway force, which is an attractive force. The yaw moment at β = −45° changes from a bow-out moment under still-water conditions to a bow-in moment. Conversely, at a current direction of β = 45°, the sway force shifts from an attractive force under still-water conditions to a repulsive force. The yaw moment acts as a bow-out moment, which is consistent with that observed in still-water conditions. Furthermore, the influence of hydrodynamic characteristics on a ship varies significantly with changes in ship speed, current speed, and water depth. To ensure the safe navigation of ships, it is essential to develop and apply comprehensive strategies and countermeasures that account for practical conditions.

Transfer-Learning-Based Temperature Uncertainty Reduction Algorithm for Large Scale Oil Tank Ground Settlement Monitoring.

Sensors operating in open-air environments can be affected by various environmental factors. Specifically, ground settlement (GS) monitoring sensors installed in oil tanks are susceptible to non-uniform temperature fields caused by uneven sunshine exposure. This disparity in environmental conditions can lead to errors in sensor readings. To address this issue, this study aimed to analyze the impact of temperature on GS monitoring sensors and establish a mapping relationship between temperature uncertainty (fluctuations of measurement caused by temperature variation) and temperature variation. By collecting the temperature information and inferring the temperature uncertainty being introduced, this interference can be removed. However, it is crucial to note that in real-world complex scenarios, the relationship between temperature uncertainty and temperature variation is not always a constant positive correlation, which limits the data available for certain periods. Moreover, the limited availability of data presents a challenge when analyzing the complex mapping relationship. To overcome these challenges, a transfer-learning-based algorithm was introduced to develop a more accurate model for predicting temperature uncertainty based on temperature variation, even with limited data. Subsequently, a practical test was conducted to validate the proposed algorithm's performance. The results demonstrated that the algorithm outperformed a simple linear fitting model using the least squares method (LSM), achieving an improvement of up to 21.9%. This outcome highlights the algorithm's potential for enhancing the performance of GS sensors in daytime monitoring and contributing to the safe operation of oil tank facilities and infrastructure health monitoring.

Environmental impact assessment of green ammonia-powered very large tanker ship for decarbonized future shipping operations

Maritime transport has been critical for the world economy and trade for centuries. Greenhouse gases and their environmental impacts are significant contributors to global warming and climate change and have compelled authorities to take substantial steps toward decarbonizing the energy system. Since then, the International Maritime Organization, policymakers, classification societies, shipping companies, and related stakeholders have been increasingly concerned about the environmental impacts of carbon-based fuels. Green ammonia as an energy vector is considered one of the top contenders for future energy systems. However, gaps remain in the literature regarding environmental impact assessment and usage. This study assessed the environmental impacts and performance of a newly built green ammonia-powered, very large oil and chemical tanker designed for the Atlantic Ocean route from Rotterdam to New York Port. This life cycle assessment study considers a tanker's entire transport life cycle from its manufacturing process to the production, material transportation, energy required for manufacturing, operation, maintenance, disassembly, scrap processing, and using green ammonia as a marine fuel. Performed an environmental impact assessment using IPCC, Environmental footprint, and ReCiPe midpoint Hierarchist (H) methodologies for five broad impact groups: Eutrophication, ozone, Climate change, Human and Ecotoxicity, and analyzed green ammonia process impacts. This study performed a comparative environmental performance assessment of HFO, LNG, blue ammonia, and green ammonia using impact categories such as GWP 100 and GTP 100. Green ammonia exhibited the most substantial negative percentage difference values (higher than −90%) per tonne-kilometer, indicating a lower environmental impact than all fuels in both categories. Adequately managing the ammonia-powered marine energy system would be indispensable for reducing environmental footprints and successfully lowering carbon, nitrogen oxide, and ammonia-based emissions.

Improved solid radiation model for thermal response in large crude oil tanks

In a crude oil tank farm, a fire in a large crude oil storage tank can spread to its neighbouring tanks due to thermal radiation causing wall rupture. To better understand the thermal radiation of tank fires and the thermal response of their neighbouring tanks, a semi-empirical radiation model is proposed in this paper. The model takes into account the smoke generation and its effect in reducing thermal radiation, as well as the variation of flame temperature and emissivity along the flame axis. Compared with existing models, the model is able to predict the radiant heat flux of the flame more accurately, and this advantage becomes more pronounced as the diameter of the pool fire increases.Using the improved model, the effect of different crude oil contents on the thermal response and failure time of the storage tank under the action of thermal radiation was innovatively explored by numerical simulation. An in-depth analysis of the failure time was performed, and an empirical equation was derived to provide a reference for fire emergency management of large storage tanks.

The Research Application of 3D Laser Scanning Technology in the Deformation Detection of Large Cylindrical Oil Tank

In order to ensure the safety in using a large cylindrical storage tank, it is necessary to regularly detect its deformation. The traditional total station method has high accuracy in determining the deformation, however, it has a low measurement efficiency. Long-term observation means, there are more risks in the petrochemical plant, therefore, this paper proposes the usage of the 3D laser scanner, replacing the traditional total station to determine the deformation of a large cylindrical storage tank. The Matlab program, is compiled to calculate the point cloud data, while the tank deformation is analyzed from two different points which are, the local concave convex degree and the ovality degree. It is concluded that, the difference between the data obtained by 3D laser scanning, and total station is within the range of oil tank deformation limit, therefore, 3D laser scanner can be used for oil tank deformation detection.

Course keeping control strategy for large oil tankers based on nonlinear feedback of swish function

In order to solve the problem of the course instability and massive energy consumption of large oil tankers in navigation, a simple control strategy is proposed. Regard the large oil tanker as an unstable plant with zero points and poles in the right half plane, map its Nomoto model into the corresponding minimum phase system，then the final control law can be derived based on the closed-loop gain shaping algorithm. In this paper, to realize the purpose of energy saving, a nonlinear feedback link of swish function is applied in the system. According to the theoretical analysis above, take the large oil tanker KARASEA as a test plant, the simulation experiments are carried out in both the general sea conditions and severe sea conditions to verify if the controller is effective. Furthermore, for further test of the robustness of the controller, the Norrbin model of ship motion is also used to carry out the simulation experiments. According to the simulation results, it can be known that the control effect is satisfactory and has great ability in anti-interference. After adding the nonlinear feedback link, the average rudder angle decreases by 15%–20%，the change range of rudder angle decreases by 19%–30%, which means the decrease of the wear and energy consumption of steering engine, so the control strategy proposed in this paper has certain engineering practical significance.

Vibrations of rigid cantilevered plates in a rectangular tank filled with liquid

The article presents the developed analytical (exact) methods for solving problems of calculating the frequencies of natural vibrations of rigid and elastic partitions in a rigid rectangular tank filled with liquid. The results of solving these problems can be used in the design of hydraulic structures, as well as in shipbuilding when analysing the dynamics of structural elements of large oil tankers and gas carriers.

Financial and Economic Indicators of Shipping Companies in 2010-2019 Years

Financial and Economic analysis of shipping companies conducted based on main maritime industry segments - Crude Oil, Products, Liquefied Natural Gas (LNG), Dry bulk commodities and Container cargo. Each of them is represented as one or several companies, which are the leaders in these business sectors. The revenues of shipping companies specialized in crude oil and product transportation have been increased significantly in 2010-2019 years, which was a result of increasing ship quantities and tonnage as well as income from time-charter. Stability can be seen in the revenues of liquefied natural gas shipping companies. The growth rate of container shipping company income was comparatively low. Moreover, the share of voyage costs have been increased in bulk commodities transportation in 2010-2019 (From 8% to 25%), decreased operating expenses, amortization of assets, charter and general costs. In the cost structure of liner shipping companies’ transportation and terminal expenses have been increased (From 10% to 26%), while the share of fuel, charter and logistics costs have been decreased. The high and stable profitability incurred in liquified natural gas transportation field as well as in oil shipping transporation with modern, new and large size oil tankers. The dry bulk and liner shipping companies were characterized with sharp unsteadiness and comperatively low profitability. The crude oil and product shipping companies had positive financial results in 2014-2016 and 2019 years, in other years they reported loss. The liquified natural gas transportation companies had a stable profit. Within the same period, dry bulk shipping companies were characterized with the lower or even unprofitability. Container shipping companies had unsteady financial results, in particular their net profit was peaking in 2010, 2014 and 2018 years and ended up with loss in 2011 and 2016 years. Keywords: The revenues of shipping companies, voyage costs, operational costs, charter costs, bunker costs, terminal costs, intermodal costs, port costs.

Techno-economic and sensitivity analysis of hybrid electric sources on off-shore oil facilities

Owing to the low efficiency of off-shore oil ships and the dangerous atmospheric pollutants of the environment that the cause of ships, solar photovoltaic and the energy storage batteries in a ship system are highly attracting attention. The basic objective of this article is to enterprise an optimal model suitable for large oil tanker ships. Therefore, most of this article discussed a design for hybrid renewable energy systems (HRESs) on an oil ship using a common optimization HOMER software. However, the incorrect sizing of HRES in the oil ships system will transpire higher greenhouse gasses (GHGs) and investment costs. So, this article presents a strategy of HRES on the ships between Egypt and China. The electric load’s profile data used are accurate and real, dependent on the sailing route of the ships directed from Dalian/China to Hurghada/Egypt. The optimal hybrid system contains solar photovoltaic (SPV), batteries storage, and diesel generator engine with a yearly capacity shortage of zero which is assigned to be the system completely reliable. The optimal system can decay the number of GHGs and the fuel consumption by 15,592,000 kg and 5,765,575L respectively in comparison with some stand-alone diesel generations during a project period. This reduction refers to an incentive factor that will lead to an essential role in raising the capacity of SPV installation on the off-shore oil. So, the HRESs minimized the total fuel prices and fuel consumption amounts. This article also discusses a comparison of HRESs on land and off-shore oil in a brief method.

Modeling and Sliding Mode Control for Chaotic Yawing Phenomenon of Large Oil Tanker

Modeling and Sliding Mode Control for Chaotic Yawing Phenomenon of Large Oil Tanker

Advanced dynamic modeling study of fire and smoke of crude oil storage tanks

The combustion properties of large-scale crude oil pool fire have great significance for security design and firefighting of current crude oil reserves. Burning rate, flame shape and radiation intensity are the most important parameters for fire properties. The novelty of this study is that the Fire Dynamics Simulator (FDS) is adopted to simulate pool fires in a tank farm. It does not only investigate and analyze heat radiation flux, but also the temperature difference rise and flame/smoke temperature contours behavior. This simulation is performed in order to predict the potentials of a large crude oil storage tank fire outbreak and the smoke temperature distribution that counters in and around the tank. These data are used in designing tank farms and applying the firefighting strategy. A super CPU with large RAM is used to operate the simulation program, to simulate one of the largest crude oil farms in the world. The model will be investigated for identifying the worst-case scenarios that might occur in a large crude oil tank. One of these scenarios might be fire outbreak in rim seal in one of the four storage tanks, where the fire is transferred to full surface fire. The model predicts the potential of tank fire outbreak, smoke tracing and both smoke/flame temperature that spreads at wind speed of 3 m/s, 9 m/s, 18 m/s in south-west direction. FDS model provides qualitative data that increase the level of safety, such as the minimum safe separation distances and the location of firefighters during the firefighting process. It also determines the most critical area, which is needed for water-cooling system. This study also tackles the duration after which human beings feel pain after being exposed to heat radiation.

COURSE-KEEPING CONTROL FOR DIRECTIONALLY UNSTABLE LARGE TANKERS USING THE MIRROR-MAPPING TECHNIQUE

This study examines the course-keeping control of directionally unstable large oil tankers involving a pole in the right half plane. Treated as an unstable plant in control engineering, tankers are theoretically and experimentally investigated during the controller design process. First, the unstable plant is mirror-mapped to its corresponding stable minimum phase plant using the mirror-mapping technique, which enables an easy controller design. Then, a linear proportional-differential and a first-order filter controller is designed based on the closed-loop gain shaping algorithm, which requires only one controller parameter to be properly selected based on the system’s characteristics. Numerical simulation results confirmed that the designed controller can successfully stabilise an unstable plant subjected to external wind and wave disturbances. The controller designed with the proposed method is suitable for course-keeping control of directionally unstable large tankers. The controller design method is simple with an uncomplicated structure that can easily be implemented in engineering endeavours. Moreover, the rudder motion is small and soft.

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.

Causes and Consequences of the Black Sea Ecosystem Pollution with Petroleum Products

Until the beginning of the 21st century concerns related to the management of protected areas have been reduced to the voluntary initiatives of nature lovers, rarely materializing in specific conservation measures carried out by the authorities or administrators of those areas. As the concern for the management of protected areas is relatively new in Romania and the information related to this subject is relatively scarce, especially those regarding marine ecosystems, we considered necessary this study on the management of marine protected areas in relation to oil pollution. Marine protected areas, in particular, delimited as areas where the main purpose is the protection of nature and cultural values, are important for all segments of society. They have great potential to become models of harmonious society development, promoting more than other protected areas the sustainable resource management. At the same time, the management measures promoted, sometimes imposed, can affect the communities inside or in the immediate vicinity of the areas, and can significantly influence the development of the economy. Recently (as a reference 1970-2020), the pollution of the marine environment with petroleum products has gained dramatic accents. The maritime transport of oil, the exploration and exploitation of marine deposits, their processing in refineries located in the vicinity of the coastal area, to which are added other anthropogenic activities, have generated and still generate a number of risk factors, which involve numerous pollution incidents. Navigation accidents of large oil tanks or incidents at offshore drilling rigs caused, in the same period, major environmental disasters, with the most severe consequences. Marine ecosystems in polluted regions have thus suffered major losses and disturbances, which have been felt for a long time. Through this paper we aim to review some aspects of oil pipeline pollution of the Planetary Ocean, respectively the associated pollution in the Black Sea ecosystem. Following the analyzes carried out on the basis of the data from the consulted literature, as well as following other observations, we came to the conclusion that the protected areas associated with the Black Sea, as well as the marine ecosystem itself, are far from being affected by such accidents.

Study on the flow characteristics of nitrogen gas foam in horizontal foam generator

With the rapid deployment of large oil tank, a quick and efficient fire extinguishing foam generator becomes particularly critical to relieve the safety concerns. In this work, a cryogenic fluid/bulk fluid mixing apparatus, composed of a horizontal channel and a conical spoiler in it, is developed to generate stable and homogeneous foam flow. The flow and temperature characteristics of the mixing flow field, including flow pattern, contour of velocity and phase fraction, temperature and pressure profiles, are studied by a visualization experiment and numerical simulation. From the results, a typical flow pattern of liquid nitrogen jetting into bulk fluid (water or foam liquid) in the mixing channel is proposed. The rapid phase transition (RPT) of nitrogen liquid in bulk fluid is found to effectively enhance the mass and heat transfer between phases. Besides, the introduction of conical spoiler facilitates the flow mixing effectively. The nitrogen liquid jet is broken into small liquid blocks and vaporizes rapidly in the conical spoiler zone. A backflow zone appears at the downstream of the spoiler and further promotes the homogeneous foam flow. Moreover, compared to the liquid nitrogen/water mixing flow, the direct mixing of liquid nitrogen/foam liquid could accomplish higher foaming ability, and more homogenous and stable foam flow due to its lower surface tension, higher dispersivity, faster interphase heat and mass transfer. The study of characteristics of the mixing flow in this work could provide an important guidance for the design and optimization of foam generators in the compressed air foam systems (CAFSs).

Field test of composite ground improved by different methods in red soil areas of China

Large oil tanks are often vulnerable to weak bearing capacity and uneven settlement of foundations, which gives rise to potential losses of both lives and property. Although the pile foundation is commonly used for large oil tanks, its high costs make it less applicable in many cases. Recently, improved ground has been adopted as a tank foundation because it is highly cost-effective. In this study, typical composite grounds improved by dynamic compaction, dynamic replacement and cement fly-ash gravel piles were adopted to work as the foundation for ten large, heavy oil tanks under various geological conditions in red soil areas in China. The results relating to improvement of the composite ground were studied comparatively in detail using in situ tests, including the dynamic penetration test, plate-load test and water injection test. Field studies show that the bearing capacity of the composite ground after treatment is over 260 kPa within the improvement depth, meeting the design requirement for the long-term service of the ten oil tanks. The field test and relevant findings indicate a promising future for composite ground in relation to large, heavy oil tanks.

Dynamic Response Analysis of Large Arch-Roof Oil Tank Subjected to the Coupling Impact of Two-Source Blast Waves Based on Finite Element Method

Research on failure law of target oil storage tank subjected to the coupling impact of multiple blast waves is one of the theoretical bases for domino effect accident prevention and control of chemical industrial parks. Taking the coupling impact of two-source blast waves as an example, the propagation law of blast waves in air and the distribution law of peak overpressure on the surface of tank wall are analyzed, and the dynamic response laws of displacement, stress, strain and energy for a 5000 m3 atmospheric steel arch-roof oil tank are studied by using ANSYS/LS-DYNA. The results are compared with those subjected to single blast wave and show that the maximum overpressure peak value is formed near the ground in 0° direction on the surface of tank wall, which is 79.6% larger than that subjected to single blast wave. The peak values of displacement, stress and strain for the tank wall subjected to the coupling impact of two-source blast waves are 114.9%, 39.6%, 134.9% larger than those subjected to single blast wave, respectively. The failure mode of arch-roof tank subjected to two-source blast waves is to form multiple concave plastic deformation zones on the explosion face, which extend to the surrounding area and produce plastic hinge lines and form irreversible residual deformation and cracking finally. The analysis results can provide reference for explosion-resistant design of tank structure and reasonable layout of tank area scene.