3-D computational method of wave loads on turret moored FPSO tankers

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.

A New Arrangement with Nonlinear Sidewalls for Tanker Ship Storage Panels

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.

Forecasting Baltic Dirty Tanker Index by Applying Wavelet Neural Networks

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.

Ultimate Strength Assessment of a Tanker Hull Based on Experimentally Developed Master Curves

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.

Time-domain Analysis of FPSO-tanker Responses in Tandem Offloading Operation

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.

Analysis on Motion and Cable Dynamic Tension for An ALT-Tanker System

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.

Comparison analysis between CSR-OT and CSR-H for corrugated bulkhead of large product tankers

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.

Strength Analysis of Turret Mooring Productive/Storage Tanker

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.

Horizontal Slow Oscillation of a Moored Tanker and Numerical Method of Hopf-Bifurcation

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.

Dynamic Analysis of a Turret-Moored Tanker

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.

Experimental Study on Allowable Berthing and Mooring Conditions of An Oil Tanker

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.

Uncertainty Modeling for Oil Tankers and Operational Guidance

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.

Safety Indications of Navigation Audit for Tankers to Develop a Bridge Inspection Method

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.

Accidents during Tanker Accident in Confined Spaces

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.

Omni Tanker:代表澳洲制造走向世界

2007年首推碳复合材料罐体概念在传统的观念里,专用汽车产品的进步应该是循序渐进一步一个脚印的。但是一个产品爆发性的进步会打破和挑战原有的市场平衡基础。2007年,一家位于澳大利亚悉尼的年轻的罐式车生产新军推出了一款名叫＂Evolution Tanker＂（进化罐车）的产品,带来了世界上第一款使用碳复合材料的罐体,用于散装液体化学品领域。

液罐车防波板对液体纵向晃动及车辆动力学的影响

为研究液罐车防波板对液体纵向晃动及车辆动力学的影响,进行液罐车的液体纵向晃动受力预测及动力学分析。首先基于计算流体力学(CFD)软件FLUENT对罐体施加纵向加速度激励,获得不同充液率下有无防波板的液体纵向晃动力和晃动力矩。利用仿真数据,训练得到有无防波板的罐内液体纵向晃动Elman神经网络预测模型,以此建立一个简化的双轴液罐车整车纵向动力学模型。通过模型直线制动工况的仿真,考察防波板不同布置方式下制动距离的响应。结果表明:Elman神经网络预测模型可以有效地预测有无防波板的罐体受力;罐体内设置防波板可以减小车辆制动距离,且防波板两头小(等间距)中间大的布置方式的制动距离较小,有利于液罐车的纵向制动稳定性。

缆绳材质对不同波浪工况下系泊油船运动影响研究

运用MIKE 21 Mooring Analysis系泊分析软件,针对15万t系泊油船,研究在横浪、顺浪作用下,缆绳属性变化对于系泊油船运动量以及缆绳受力的影响。研究结果表明,在横浪的工况下,系泊油船的横移、纵移、回转三个运动量随着缆绳刚度的增大而减小;在顺浪的工况下,在入射波浪周期较小的情况下,随缆绳刚度的增大,系泊油船的纵移运动量减小、纵摇略有增大。在入射波浪周期较大的情况下,随缆绳刚度的增大,系泊油船的纵移运动量增大、纵摇减小。横摇、回转、横移三个运动量大体上随缆绳刚度的增大而增大,但是变化幅度较小。两种工况下升沉量基本不随缆绳刚度变化。

穿梭油轮新型卧式艏装载系统设计研究

穿梭油轮在现代海洋原油运输中扮演着重要角色,艏装载系统是其核心组成部分之一,在原油串靠外输过程中至关重要。目前,我国海洋原油外输作业多采用船舯软管外输方式,与艏装载系统的船艏输送相比,存在一些局限性。针对南海东部地区船舶使用原油外输艏装载技术所面临的问题,从介绍艏装载系统船艏输送的作业流程出发,通过与国外传统穿梭油轮的艏装载方式相比,提出一种新型卧式艏装载系统布局方案,优化艏装载系统的结构,为穿梭油轮艏装载改造设计提供参考。

常压罐车罐体检验机构资质管理与技术要求研究

我国常压罐车罐体的第三方检验分为出厂检验和定期检验,常压罐车罐体检验机构管理和检验技术要求存在较多问题。通过分析我国常压罐车罐体检验机构资质要求和技术要求,提出了相应的对策建议,可为常压罐车罐体的生产、检验、认可、监管提供参考。

基于油轮惰性气体灭火的研究

传统油轮烟气灭火系统存在灭火效果不理想,烟气处理不彻底等问题,本文将传统烟气和燃烧两种惰气生产模式进行融合,形成多功能惰气系统的油轮惰性气体灭火系统(IGS)的设计方案,该方案具有灭火高效率且安全等特点,指明了该系统日后的发展方向主要为优化惰气风机的结构。该系统对于油轮安全和环境保护等方面均有重要意义。