A three-dimensional method of calculating wave loads of turret moored FPSO (Flo ating Production Storage and Offloading) tankers is presented. The linearized restoring forces acting on the ship hull by the mooring sys...A three-dimensional method of calculating wave loads of turret moored FPSO (Flo ating Production Storage and Offloading) tankers is presented. The linearized restoring forces acting on the ship hull by the mooring system are calculated according to the catenary theory, which are expressed as the function of linear stiffness coefficients and the displacements of the upper ends of mooring chains. The hydrodynamic coefficients of the ship are calculated by the three-dimensional potential flow theory of the linear hydrodynamic problem for ships with a low forward speed. The equations of ship motions are established with the effect of the restoring forces from the mooring system included as linear stiffness coefficients. The equations of motions are solved in frequency domain, and the responses of wave-induced motions and loads on the ship can be obtained. A computer pro gram based on this method has been developed,and some calculation examples are illustrated. Analysis results show that the method can give satisfying prediction of wave loads.展开更多
Sloshing phenomenon in a moving container is a complicated free surface flow problem. It has a wide range of engineering applications, especially in tanker ships and Liquefied Natural Gas (LNG) carriers. When the tank...Sloshing phenomenon in a moving container is a complicated free surface flow problem. It has a wide range of engineering applications, especially in tanker ships and Liquefied Natural Gas (LNG) carriers. When the tank in these vehicles is partially filled, it is essential to be able to evaluate the fluid dynamic loads on tank perimeter. Different geometric shapes such as rectangular, cylindrical, elliptical, spherical and circular conical have been suggested for ship storage tanks by previous researchers. In this paper a numerical model is developed based on incompressible and inviscid fluid motion for the liquid sloshing phenomenon. The coupled BEM-FEM is used to solve the governing equations and nonlinear free surface boundary conditions. The results are validated for rectangular container using data obtained for a horizontal periodic sway motion. Using the results of this model a new arrangement of trapezoidal shapes with quadratic sidewalls is suggested for tanker ship storage panels. The suggested geometric shape not only has a maximum surrounded tank volume to the constant available volume, but also reduces the sloshing effects more efficiently than the existing geometric shapes.展开更多
Baltic Exchange Dirty Tanker Index (BDTI) is an important assessment index in world dirty tanker shipping industry. Actors in the industry sector can gain numerous benefits from accurate forecasting of the BDTI. Howev...Baltic Exchange Dirty Tanker Index (BDTI) is an important assessment index in world dirty tanker shipping industry. Actors in the industry sector can gain numerous benefits from accurate forecasting of the BDTI. However, limitations exist in traditional stochastic and econometric explanation modeling techniques used in freight rate forecasting. At the same time research in shipping index forecasting e.g. BDTI applying artificial intelligent techniques is scarce. This analyses the possibilities to forecast the BDTI by applying Wavelet Neural Networks (WNN). Firstly, the characteristics of traditional and artificial intelligent forecasting techniques are discussed and rationales for choosing WNN are explained. Secondly, the components and features of BDTI will be explicated. After that, the authors delve the determinants and influencing factors behind fluctuations of the BDTI in order to set inputs for WNN forecasting model. The paper examines non-linearity and non-stationary features of the BDTI and elaborates WNN model building procedures. Finally, the comparison of forecasting performance between WNN and ARIMA time series models show that WNN has better forecasting accuracy than traditionally used modeling techniques.展开更多
A geometrically similar scaling was made from small-scale specimen to full-scale stiffened panels and then their collapse behaviour is investigated. It is considered that the stiffened panel compressive ultimate stren...A geometrically similar scaling was made from small-scale specimen to full-scale stiffened panels and then their collapse behaviour is investigated. It is considered that the stiffened panel compressive ultimate strength test was designed according to geometrical scaling laws so that the output of the test could be used as representative of the stiffened panels of the compressive zone of a tanker hull subjected to vertical bending moment. The ultimate strength of a tanker hull is analysed by a FE analysis using the experimentally developed master stress-strain curves which are obtained by the beam tension test and the compressive test of the stiffened panel, and are then compared with the result achieved by the progressive collapse method.展开更多
Problems experienced during Floating Production, Storage and Offioading （FPSO） tandem offloading operations were investigated. The aim of this research was to improve the reliability of such systems, and it needed a...Problems experienced during Floating Production, Storage and Offioading （FPSO） tandem offloading operations were investigated. The aim of this research was to improve the reliability of such systems, and it needed a means to assess them. Time-domain simulation and analysis of offioading systems was performed using the multi-body mooring software ARIANE 7.0. Hydrodynamic interaction between the vessels was considered. The responses of the offioading system in different loading cases, different parameters of offioading hawsers and the effects of challenging environmental conditions were calculated. There was a focus on the problems of relative motion between the two bodies and its effects on the intensity of hawser forces. Minimum relative distance, maximum relative headings and maximum tension in the hawsers of offloading systems were obtained by time-domain analysis. The time-domain analysis was effective and comparative study can be used to optimize parameters of the system and extend operating limits.展开更多
A two-degree freedom model for an ALT-tanker system is established corresponding to the pitch of the ALT and the surge of the tanker.Tension in the mooring cable between the ALT and the tanker is represented by an uns...A two-degree freedom model for an ALT-tanker system is established corresponding to the pitch of the ALT and the surge of the tanker.Tension in the mooring cable between the ALT and the tanker is represented by an unsymmetrical,piecewise-nonlinear function.Wave load on the tower is evaluated by use of the Morison equation.The first order wave load acting on the tanker is calculated by the linear diffraction theory based on the 2-D Helmholtz equation,and the near field approach of Pinkster is used to evaluate the second order drift force.The dynamic equation of motion is established based on the principle of D＇lembert.Dynamic response and cable tension of a mooring system composed of an 88.4 m ALT and a 100000 t grade tanker are calculated.The influence of wave frequency,wave excitation amplitude,wind and current force on ALT-tanker motion and cable tension is discussed.展开更多
Large Aframax product tanker(more than 100k DWT),with centerline longitudinal corrugated bulkheads and transverse corrugated bulkheads in cargo area,is the largest type of product tanker at present.The external draft ...Large Aframax product tanker(more than 100k DWT),with centerline longitudinal corrugated bulkheads and transverse corrugated bulkheads in cargo area,is the largest type of product tanker at present.The external draft of Harmonized Common Structural Rules(CSR-H)for Bulk Carriers and Oil Tankers is released for external review.More attentions are paid to the impact of CSR-H on the structural design of the corrugated bulkhead of large Aframax product tankers.Based on CSR-OT and CSR-H,it discusses the impact of CSR-H on the corrugated bulkhead by strength assessment of a 115k DWT product tanker.展开更多
The longitudinal strength of turret mooring productive/storage tanker is studied. A numerical example has been implemented according to the method presented in this paper to give practical illustration. From the resul...The longitudinal strength of turret mooring productive/storage tanker is studied. A numerical example has been implemented according to the method presented in this paper to give practical illustration. From the results of the numerical example, it is concluded that the turret hole located near the forward of the amidships has small effect on the longitudinal strength of the ship hull. As for design extreme value of wave bending moment of storage tanker, statistic method is a more reasonable methodology, especially with the consideration of the servere environmental conditions. The primary estimation of design section modulus of turret storage tanker can be determined by this design bending moment.展开更多
In this paper, a six-order nonlinear dynamic model with three degrees of freedom is presented for the study of the 'fishtail' motion of a Single Point Mooring System. The effect of parameter variations on the ...In this paper, a six-order nonlinear dynamic model with three degrees of freedom is presented for the study of the 'fishtail' motion of a Single Point Mooring System. The effect of parameter variations on the equilibrium state of the system is analyzed. In order to study the stability of the equilibrium state, the mooring-line length l is chosen as a bifurcation parameter, so that all eigenvalues of the Jacobian matrix under different parameters can be worked out, and then the Hopf-bifurcation point can be found. Finally, the Hopf-bifurcation periodic solution of the system is computed.展开更多
In this paper, the second-order perturbation method in frequency domain is used to calculate RAO and spectra of motion and mooring line tension of a turret-moored tanker in ballast condition. The calculated results ar...In this paper, the second-order perturbation method in frequency domain is used to calculate RAO and spectra of motion and mooring line tension of a turret-moored tanker in ballast condition. The calculated results are compared with corresponding experiment results. In the experiment the wave heading is 180 degrees, and the wave spectra is the P-M spectrum and white noise spectrum. In the theoretical calculations, the damping coefficient of slow oscillation of the tanker is determined on the basis of the damping obtained from a test of irregular waves where the mooring system is replaced by a nonlinear spring with nonlinear stiffness similar to that of the mooring system. From the comparison between theoretical calculations and experiment al results, it can be found that the theoretical results obtained by the second-order perturbation method in frequency domain are in good agreement with the experimental results, indicating that the damping coefficient of slow oscillation of the tanker required in frequency domain calculation can be determined by reference to the damping coefficient of the tanker moored by a spring system in irregular waves, and the second-order perturbation method can be used to analyze the dynamic response of a turret-moored tanker.展开更多
When an oil tanker under the combined action of wind, waves and tidal current and is berthed or moored to a platform, the impact forces on the fenders and the tensile force in the mooring lines are important factors i...When an oil tanker under the combined action of wind, waves and tidal current and is berthed or moored to a platform, the impact forces on the fenders and the tensile force in the mooring lines are important factors in the studies of berthing and mooring conditions. Based on the experiment of a berthing and mooring tanker model under the action of wind, wave and tidal current in the same direction, this paper studies the allowable berthing and mooring conditions by considering the tensile forces of mooring lines and impact forces on the fenders, as well as the impact energy on the fenders. And a method has been proposed here for motion amplitude analysis. A successful method to decrease impact forces on the fenders is put forward. Blowing in wind and blowing off wind and different angles between waves and the fenders are considered in the experimental study. In the berthing tests of the tanker model, the impact forces are measured and the impact energy is calculated, then the berthing conditions are determined. In the mooring tests of the tanker model, the mooring line tensile forces and impact forces are measured, and the allowable mooring conditions are given that will be useful to engineering design.展开更多
Technology evolution has been a driving factor in the oil tanker industry. The technology breakthroughs and historical data served as the main factor of evo-lution in the industry. Nowadays the oil tankers have been m...Technology evolution has been a driving factor in the oil tanker industry. The technology breakthroughs and historical data served as the main factor of evo-lution in the industry. Nowadays the oil tankers have been modified and opti-mized according to the requirements of the cargo and the area in which they are supposed to operate. This paper reviews some technological developments in the tanker industry and driving factors behind them. The issues of environmental pollution, failure prediction, and efficient operations are also discussed in mathematical terms.展开更多
A mathematical model of optimization for cargo hold structure of small and medium-sized duplex stainless steel (DSS) chemical tankers based on the rule is described.The weight of DSS is defined as the objective functi...A mathematical model of optimization for cargo hold structure of small and medium-sized duplex stainless steel (DSS) chemical tankers based on the rule is described.The weight of DSS is defined as the objective function.The explicit formulas of the relevant rules,the explicit geometric relations formed by the structural arrangement and the implicit constraints such as layout,lines,expert experience,workmanship and so on are taken as the constraints.The design variables and the algorithm are determined by analyzing the logical relations among the factors.Besides,the efficiency of the optimum algorithm is improved by utilizing the distribution law of the optimal corrugations.Finally,the comprehensive optimization of the cargo hold DSS is accomplished by C++ programming.The weight of the optimized scheme of the example is 4.93% lower than that of the original scheme.The finite element analysis results show that the optimized scheme is satisfied with the requirements of the rules and has a good structure performance.The optimization method based on the rules and accomplished by the programming is practical for structural preliminary design.展开更多
A significant amount of world trade has been carried out by maritime transportation. In 2016, world maritime trade volume increased by 2% and reached 10.3 billion tons, 55,057 global ton-miles. There has been a signif...A significant amount of world trade has been carried out by maritime transportation. In 2016, world maritime trade volume increased by 2% and reached 10.3 billion tons, 55,057 global ton-miles. There has been a significant increase in quantity and tonnage of tankers, with the requirement for well qualified and experienced personnel in the maritime industry. Therefore, employment has become a serious problem. Major Oil Companies (MOCs), port states, classification societies, and flag states have increased the number of inspections on tankers due to safety concerns. Tanker inspections are becoming more difficult and inefficient due to intensive cargo operations. Inefficient, subjective or substandard inspections/evaluations are usually leading to incorrect decisions, and causing an unfair market. In addition, corrective actions cannot be carried out properly, and decision making authorities cannot give the best decisions about vessels and their operator companies due to lack of scientific methods. In this study, details are identified such as finding the root causes, identifying the risks, understanding the possible consequences, and determining the working areas during the ship crews’, operators’, auditors’ and charterers’ working and ship selection periods. Pairwise comparisons were carried out by means of surveys on ship masters (captains), chief officers, deck officers, and superintendents. Five criteria—Crew, Equipment, Company, Structure, and ISM (International Safety Management) were weighted using Analytical Hierarchy Process (AHP). Finally, Bridge Safety Support System (BSSS) was developed according to criteria weights. In this way, best choices can be offered to ship charterers about which ship is better for a company’s interests. And, carrying out bridge inspections and corrective actions will be more reliable and effective for maritime transportation. Statistical data and vessel improvements will be obtained in BSSS. As a result, fair market conditions will be available in maritime industry with the help of this study.展开更多
One of the major hazards when working onboard Tankers is working in confined spaces, improving the procedures in working in such spaces is obvious, but developing the equipments used in rescue operation is rare to hap...One of the major hazards when working onboard Tankers is working in confined spaces, improving the procedures in working in such spaces is obvious, but developing the equipments used in rescue operation is rare to happen, that＇s why this paper is focusing on differentiating between the manual ＆ more developed equipments used specially in rescuing the crew in such an adequate time, to save the workers＇ life. The manual way is called ＂MUCKY CRANE＂ which is used for rescue purposes onboard tankers, in any of the confined spaces, should be replaced by excel crane which is air or hydraulic driven machine, to achieve better results. As safety precautions measures taken in such tasks are not enough for the required objective achievement. Such safety procedures have been discussed and critical situations have been pointed out.展开更多
Ballast water is essential for cargo ships since it stabilizes vessels at sea.Most ships are equipped with a ballast water system(BWS)to maintain safe operating conditions.This paper attempts to perform a risk assessm...Ballast water is essential for cargo ships since it stabilizes vessels at sea.Most ships are equipped with a ballast water system(BWS)to maintain safe operating conditions.This paper attempts to perform a risk assessment for the BWS on-board tanker ship as it poses a major threat to the operational safety of the ship,marine environment,and cargo.To achieve this purpose,the paper utilizes a robust methodology integrating D-S evidence(Dempster-Shafer)theory and FMECA(Failure mode effects and criticality anal-ysis).In the methodology,while the D-S evidence theory introduces a proper mathematical framework to handle epistemic uncertainty in the assessment of risk parameters and to prioritize failure modes as intended,the FMECA is capable of evaluating system potential failures and their causes.Hence,the risk priority number(RPN)can be calculated to assess potential hazards and their consequences in BWS on-board ships.Besides its theoretical insight,the paper contributes to marine safety inspectors,safety researchers,and HSEQ(Health,Safety,Environment,and Quality)managers to identify potential hazards,effects,and consequences in case of BWS failures on-board tanker ships.展开更多
Shuttle tankers scheduling is an important task in offshore oil and gas transportation process,which involves operating time window fulfillment,optimal transportation planning,and proper inventory management.However,c...Shuttle tankers scheduling is an important task in offshore oil and gas transportation process,which involves operating time window fulfillment,optimal transportation planning,and proper inventory management.However,conventional approaches like Mixed lnteger Linear Programming(MlLP)or meta heuristic algorithms often fail in long running time.In this paper,a Graph Pointer Network(GPN)based Hierarchical Curriculum Reinforcement Learning(HCRl)method is proposed to solve Shuttle Tankers Scheduling Problem(STSP)The model is trained to divide STSP into voyage and operation stages and generate routing and inventory management decisions sequentially.An asynchronous training strategy is developed to address the coupling between stages.Comparison experiments demonstrate that the proposed HCRL method achieves 12%shortel tour lengths on average compared to heuristic algorithms.Additional experiments validate its generalizability to unseen instances and scalability to larger instances.展开更多
文摘A three-dimensional method of calculating wave loads of turret moored FPSO (Flo ating Production Storage and Offloading) tankers is presented. The linearized restoring forces acting on the ship hull by the mooring system are calculated according to the catenary theory, which are expressed as the function of linear stiffness coefficients and the displacements of the upper ends of mooring chains. The hydrodynamic coefficients of the ship are calculated by the three-dimensional potential flow theory of the linear hydrodynamic problem for ships with a low forward speed. The equations of ship motions are established with the effect of the restoring forces from the mooring system included as linear stiffness coefficients. The equations of motions are solved in frequency domain, and the responses of wave-induced motions and loads on the ship can be obtained. A computer pro gram based on this method has been developed,and some calculation examples are illustrated. Analysis results show that the method can give satisfying prediction of wave loads.
文摘Sloshing phenomenon in a moving container is a complicated free surface flow problem. It has a wide range of engineering applications, especially in tanker ships and Liquefied Natural Gas (LNG) carriers. When the tank in these vehicles is partially filled, it is essential to be able to evaluate the fluid dynamic loads on tank perimeter. Different geometric shapes such as rectangular, cylindrical, elliptical, spherical and circular conical have been suggested for ship storage tanks by previous researchers. In this paper a numerical model is developed based on incompressible and inviscid fluid motion for the liquid sloshing phenomenon. The coupled BEM-FEM is used to solve the governing equations and nonlinear free surface boundary conditions. The results are validated for rectangular container using data obtained for a horizontal periodic sway motion. Using the results of this model a new arrangement of trapezoidal shapes with quadratic sidewalls is suggested for tanker ship storage panels. The suggested geometric shape not only has a maximum surrounded tank volume to the constant available volume, but also reduces the sloshing effects more efficiently than the existing geometric shapes.
文摘Baltic Exchange Dirty Tanker Index (BDTI) is an important assessment index in world dirty tanker shipping industry. Actors in the industry sector can gain numerous benefits from accurate forecasting of the BDTI. However, limitations exist in traditional stochastic and econometric explanation modeling techniques used in freight rate forecasting. At the same time research in shipping index forecasting e.g. BDTI applying artificial intelligent techniques is scarce. This analyses the possibilities to forecast the BDTI by applying Wavelet Neural Networks (WNN). Firstly, the characteristics of traditional and artificial intelligent forecasting techniques are discussed and rationales for choosing WNN are explained. Secondly, the components and features of BDTI will be explicated. After that, the authors delve the determinants and influencing factors behind fluctuations of the BDTI in order to set inputs for WNN forecasting model. The paper examines non-linearity and non-stationary features of the BDTI and elaborates WNN model building procedures. Finally, the comparison of forecasting performance between WNN and ARIMA time series models show that WNN has better forecasting accuracy than traditionally used modeling techniques.
基金financed by the Portuguese Foundation for Science and Technology (Fundao para a Ciência e Tecnologia), under contract SFRH/BD/65120/2009
文摘A geometrically similar scaling was made from small-scale specimen to full-scale stiffened panels and then their collapse behaviour is investigated. It is considered that the stiffened panel compressive ultimate strength test was designed according to geometrical scaling laws so that the output of the test could be used as representative of the stiffened panels of the compressive zone of a tanker hull subjected to vertical bending moment. The ultimate strength of a tanker hull is analysed by a FE analysis using the experimentally developed master stress-strain curves which are obtained by the beam tension test and the compressive test of the stiffened panel, and are then compared with the result achieved by the progressive collapse method.
基金Supported by China National 111 Project foundation from the State Administration of Foreign Experts Affairs of Chinathe Ministry of Education of China under Grant No.B07019
文摘Problems experienced during Floating Production, Storage and Offioading （FPSO） tandem offloading operations were investigated. The aim of this research was to improve the reliability of such systems, and it needed a means to assess them. Time-domain simulation and analysis of offioading systems was performed using the multi-body mooring software ARIANE 7.0. Hydrodynamic interaction between the vessels was considered. The responses of the offioading system in different loading cases, different parameters of offioading hawsers and the effects of challenging environmental conditions were calculated. There was a focus on the problems of relative motion between the two bodies and its effects on the intensity of hawser forces. Minimum relative distance, maximum relative headings and maximum tension in the hawsers of offloading systems were obtained by time-domain analysis. The time-domain analysis was effective and comparative study can be used to optimize parameters of the system and extend operating limits.
基金supported bythe Ph.D.Programs Foundation of Ministry of Education of China(Grant No.20050056052)the National High Technology Research and Development Program of China(863 Program,Grant No.2007AA09z304)
文摘A two-degree freedom model for an ALT-tanker system is established corresponding to the pitch of the ALT and the surge of the tanker.Tension in the mooring cable between the ALT and the tanker is represented by an unsymmetrical,piecewise-nonlinear function.Wave load on the tower is evaluated by use of the Morison equation.The first order wave load acting on the tanker is calculated by the linear diffraction theory based on the 2-D Helmholtz equation,and the near field approach of Pinkster is used to evaluate the second order drift force.The dynamic equation of motion is established based on the principle of D＇lembert.Dynamic response and cable tension of a mooring system composed of an 88.4 m ALT and a 100000 t grade tanker are calculated.The influence of wave frequency,wave excitation amplitude,wind and current force on ALT-tanker motion and cable tension is discussed.
文摘Large Aframax product tanker(more than 100k DWT),with centerline longitudinal corrugated bulkheads and transverse corrugated bulkheads in cargo area,is the largest type of product tanker at present.The external draft of Harmonized Common Structural Rules(CSR-H)for Bulk Carriers and Oil Tankers is released for external review.More attentions are paid to the impact of CSR-H on the structural design of the corrugated bulkhead of large Aframax product tankers.Based on CSR-OT and CSR-H,it discusses the impact of CSR-H on the corrugated bulkhead by strength assessment of a 115k DWT product tanker.
文摘The longitudinal strength of turret mooring productive/storage tanker is studied. A numerical example has been implemented according to the method presented in this paper to give practical illustration. From the results of the numerical example, it is concluded that the turret hole located near the forward of the amidships has small effect on the longitudinal strength of the ship hull. As for design extreme value of wave bending moment of storage tanker, statistic method is a more reasonable methodology, especially with the consideration of the servere environmental conditions. The primary estimation of design section modulus of turret storage tanker can be determined by this design bending moment.
文摘In this paper, a six-order nonlinear dynamic model with three degrees of freedom is presented for the study of the 'fishtail' motion of a Single Point Mooring System. The effect of parameter variations on the equilibrium state of the system is analyzed. In order to study the stability of the equilibrium state, the mooring-line length l is chosen as a bifurcation parameter, so that all eigenvalues of the Jacobian matrix under different parameters can be worked out, and then the Hopf-bifurcation point can be found. Finally, the Hopf-bifurcation periodic solution of the system is computed.
基金National Natural Science Foundation of China(Grant No.59709002)
文摘In this paper, the second-order perturbation method in frequency domain is used to calculate RAO and spectra of motion and mooring line tension of a turret-moored tanker in ballast condition. The calculated results are compared with corresponding experiment results. In the experiment the wave heading is 180 degrees, and the wave spectra is the P-M spectrum and white noise spectrum. In the theoretical calculations, the damping coefficient of slow oscillation of the tanker is determined on the basis of the damping obtained from a test of irregular waves where the mooring system is replaced by a nonlinear spring with nonlinear stiffness similar to that of the mooring system. From the comparison between theoretical calculations and experiment al results, it can be found that the theoretical results obtained by the second-order perturbation method in frequency domain are in good agreement with the experimental results, indicating that the damping coefficient of slow oscillation of the tanker required in frequency domain calculation can be determined by reference to the damping coefficient of the tanker moored by a spring system in irregular waves, and the second-order perturbation method can be used to analyze the dynamic response of a turret-moored tanker.
文摘When an oil tanker under the combined action of wind, waves and tidal current and is berthed or moored to a platform, the impact forces on the fenders and the tensile force in the mooring lines are important factors in the studies of berthing and mooring conditions. Based on the experiment of a berthing and mooring tanker model under the action of wind, wave and tidal current in the same direction, this paper studies the allowable berthing and mooring conditions by considering the tensile forces of mooring lines and impact forces on the fenders, as well as the impact energy on the fenders. And a method has been proposed here for motion amplitude analysis. A successful method to decrease impact forces on the fenders is put forward. Blowing in wind and blowing off wind and different angles between waves and the fenders are considered in the experimental study. In the berthing tests of the tanker model, the impact forces are measured and the impact energy is calculated, then the berthing conditions are determined. In the mooring tests of the tanker model, the mooring line tensile forces and impact forces are measured, and the allowable mooring conditions are given that will be useful to engineering design.
文摘Technology evolution has been a driving factor in the oil tanker industry. The technology breakthroughs and historical data served as the main factor of evo-lution in the industry. Nowadays the oil tankers have been modified and opti-mized according to the requirements of the cargo and the area in which they are supposed to operate. This paper reviews some technological developments in the tanker industry and driving factors behind them. The issues of environmental pollution, failure prediction, and efficient operations are also discussed in mathematical terms.
文摘A mathematical model of optimization for cargo hold structure of small and medium-sized duplex stainless steel (DSS) chemical tankers based on the rule is described.The weight of DSS is defined as the objective function.The explicit formulas of the relevant rules,the explicit geometric relations formed by the structural arrangement and the implicit constraints such as layout,lines,expert experience,workmanship and so on are taken as the constraints.The design variables and the algorithm are determined by analyzing the logical relations among the factors.Besides,the efficiency of the optimum algorithm is improved by utilizing the distribution law of the optimal corrugations.Finally,the comprehensive optimization of the cargo hold DSS is accomplished by C++ programming.The weight of the optimized scheme of the example is 4.93% lower than that of the original scheme.The finite element analysis results show that the optimized scheme is satisfied with the requirements of the rules and has a good structure performance.The optimization method based on the rules and accomplished by the programming is practical for structural preliminary design.
文摘A significant amount of world trade has been carried out by maritime transportation. In 2016, world maritime trade volume increased by 2% and reached 10.3 billion tons, 55,057 global ton-miles. There has been a significant increase in quantity and tonnage of tankers, with the requirement for well qualified and experienced personnel in the maritime industry. Therefore, employment has become a serious problem. Major Oil Companies (MOCs), port states, classification societies, and flag states have increased the number of inspections on tankers due to safety concerns. Tanker inspections are becoming more difficult and inefficient due to intensive cargo operations. Inefficient, subjective or substandard inspections/evaluations are usually leading to incorrect decisions, and causing an unfair market. In addition, corrective actions cannot be carried out properly, and decision making authorities cannot give the best decisions about vessels and their operator companies due to lack of scientific methods. In this study, details are identified such as finding the root causes, identifying the risks, understanding the possible consequences, and determining the working areas during the ship crews’, operators’, auditors’ and charterers’ working and ship selection periods. Pairwise comparisons were carried out by means of surveys on ship masters (captains), chief officers, deck officers, and superintendents. Five criteria—Crew, Equipment, Company, Structure, and ISM (International Safety Management) were weighted using Analytical Hierarchy Process (AHP). Finally, Bridge Safety Support System (BSSS) was developed according to criteria weights. In this way, best choices can be offered to ship charterers about which ship is better for a company’s interests. And, carrying out bridge inspections and corrective actions will be more reliable and effective for maritime transportation. Statistical data and vessel improvements will be obtained in BSSS. As a result, fair market conditions will be available in maritime industry with the help of this study.
文摘One of the major hazards when working onboard Tankers is working in confined spaces, improving the procedures in working in such spaces is obvious, but developing the equipments used in rescue operation is rare to happen, that＇s why this paper is focusing on differentiating between the manual ＆ more developed equipments used specially in rescuing the crew in such an adequate time, to save the workers＇ life. The manual way is called ＂MUCKY CRANE＂ which is used for rescue purposes onboard tankers, in any of the confined spaces, should be replaced by excel crane which is air or hydraulic driven machine, to achieve better results. As safety precautions measures taken in such tasks are not enough for the required objective achievement. Such safety procedures have been discussed and critical situations have been pointed out.
文摘Ballast water is essential for cargo ships since it stabilizes vessels at sea.Most ships are equipped with a ballast water system(BWS)to maintain safe operating conditions.This paper attempts to perform a risk assessment for the BWS on-board tanker ship as it poses a major threat to the operational safety of the ship,marine environment,and cargo.To achieve this purpose,the paper utilizes a robust methodology integrating D-S evidence(Dempster-Shafer)theory and FMECA(Failure mode effects and criticality anal-ysis).In the methodology,while the D-S evidence theory introduces a proper mathematical framework to handle epistemic uncertainty in the assessment of risk parameters and to prioritize failure modes as intended,the FMECA is capable of evaluating system potential failures and their causes.Hence,the risk priority number(RPN)can be calculated to assess potential hazards and their consequences in BWS on-board ships.Besides its theoretical insight,the paper contributes to marine safety inspectors,safety researchers,and HSEQ(Health,Safety,Environment,and Quality)managers to identify potential hazards,effects,and consequences in case of BWS failures on-board tanker ships.
基金supported by the National Natural Science Foundation of China(Nos.22178383 and 21706282)Beijing Natural Science Foundation(No.2232021)Research Foundation of China University of Petroleum(Beijing)(No.2462020BJRC004).
文摘Shuttle tankers scheduling is an important task in offshore oil and gas transportation process,which involves operating time window fulfillment,optimal transportation planning,and proper inventory management.However,conventional approaches like Mixed lnteger Linear Programming(MlLP)or meta heuristic algorithms often fail in long running time.In this paper,a Graph Pointer Network(GPN)based Hierarchical Curriculum Reinforcement Learning(HCRl)method is proposed to solve Shuttle Tankers Scheduling Problem(STSP)The model is trained to divide STSP into voyage and operation stages and generate routing and inventory management decisions sequentially.An asynchronous training strategy is developed to address the coupling between stages.Comparison experiments demonstrate that the proposed HCRL method achieves 12%shortel tour lengths on average compared to heuristic algorithms.Additional experiments validate its generalizability to unseen instances and scalability to larger instances.
