Reducing the cost of ballast tank corrosion: an economic modeling approach

One of the most relevant problems in ship construction and maintenance nowadays concerns the corrosion in the double hull space ballast tanks of modern merchant vessels. On the one hand, there is a general consensus that the economic life span of such a vessel depends primarily upon the corrosion state of its ballast tanks, while on the other hand, the position of these tanks, squeezed between the outer hull and the loading tanks, makes routine inspection and maintenance almost impossible.Today, ship's ballast tanks are usually constructed in grade A steel and protected with a standard epoxy coating, backed up with sacrificial zinc anodes. Such a construction has been applied without significant alterations for many years. However, the objective of this economic study is to compare this construction method with some feasible alternatives. The considered alternatives are: (1) an increase of the scantlings, eliminating the necessity to replace corroded steel but diminishing the cargo carrying capacity of the ship, (2) application of the novel and more durable TSCF₂₅ coating (3), the use of corrosion resistant steel in ship construction or (4) a standard PSPC₁₅ coating combined with lifetime lasting aluminum sacrificial anodes. After running each alternative through a cost model including an extensive sensitivity analysis, it is concluded that the durable coating and the use of lifetime lasting aluminum anodes are bound to improve the actual basic tank concept. Corrosion resistant steel becomes attractive depending upon the evolution of the international steel market.     

A field study of the effectiveness of sacrificial anodes in ballast tanks of merchant ships

Sacrificial anodes have become a standard practice for the protection of ballast tanks of merchant vessels against corrosive damage. A well protected tank should extend the life span of a ship and consequently enhances its economic value. An in situ survey comprising more than 100 merchant vessels provided the opportunity to measure the impact of these anodes on the life expectancy of these vessels. Contrary to the general belief of these anodes’ beneficial effect, no significant difference was found in our observations in terms of corrosion occurrence between ship populations with and without sacrificial anodes, across all ship ages. This may be explained by the highly variable conditions and the complex geometry in a ballast tank severely impede optimal and straightforward installation of these anodes in these tanks. Also, poorly placed anodes in it may harm the integrity of the coating of the tank. We therefore plead for uniform and clear rules on anode installation and inspection.     

牺牲阳极和包覆材料联合保护在友谊港的防腐应用

根据不同海洋腐蚀区域的特点,采取涂层保护、冷包缠防腐保护和牺牲阳极阴极保护组合保护的形式,对毛里塔尼亚友谊港钢管桩进行防腐修复。施工过程中严格质量控制,达到了预期的实施效果,顺利通过了友谊港业主的验收。     

全压式LPG船液货罐安装技术研究

以航通公司建造的一艘3700立方全压式LPG远洋运输船液货罐安装技术为例,分析和介绍了全压式LPG船液货罐安装的特点和需要解决的问题,在实船安装中采取环氧胶泥和层压木组合安装技术,文章介绍有关安装技术关键,并结合有关规范要求进行分析计算研究,提出合理模型。实践证明,该施工技术对类似船舶液货罐的安装具有参考价值。     

Sacrificial anode stability and polarization potential variation in a ternary Al-xZn-xMg alloy in a seawater-marine environment

In this paper, the effects of zinc (Zn) and magnesium (Mg) addition on the performance of an aluminum-based sacrificial anode in seawater were investigated using a potential measurement method. Anodic efficiency, protection efficiency, and polarized potential were the parameters used. The percentages of Zn and Mg in the anodes were varied from 2% to 8% Zn and 1% to 4% Mg. The alloys produced were tested as sacrificial anodes for the protection of mild steel in seawater at room temperature. Current efficiency as high as 88.36% was obtained in alloys containing 6% Zn and 1% Mg. The polarized potentials obtained for the coupled (steel/Al-based alloys) are as given in the Pourbaix diagrams, with steel lying within the immunity region/cathodic region and the sacrificial anodes within the anodic region. The protection offered by the sacrificial anodes to the steel after the 7th and 8th week was measured and protection efficiency values as high as 99.66% and 99.47% were achieved for the Al-6%Zn-1%Mg cast anode. The microstructures of the cast anodes comprise of intermetallic structures of hexagonal Mg₃Zn2 and body-centered cubic Al₂Mg₃Zn₃. These are probably responsible for the breakdown of the passive alumina film, thus enhancing the anode efficiency.     

双相不锈钢化学品船压载水舱涂装工艺

双相不锈钢化学品船的货舱壁采用双相不锈钢材质，可直接接触装载的化学品，货舱内壁无须进行涂装施工，但货舱外壁作为如压载水舱等其他舱室的舱壁，需要进行涂装施工。不锈钢原则上不能使用工厂常规使用的钢砂进行表面处理，为避免污染不锈钢板，须选用棕刚玉等非金属磨料。在制订38 000 DWT双相不锈钢化学品船压载水舱涂装工艺过程中，结合船厂的实际施工条件，兼顾建造成本，将压载水舱按照材质构成进行划分，针对不同情况进行表面处理和涂装施工，保证该船建造的顺利开展。     

獭山港码头钢管桩牺牲阳极阴极保护效果的评定

獭山港某码头钢管桩采取防腐涂层和牺牲阳极阴极保护措施已10余a。通过对该码头钢管桩阴极保护系统防腐效果的检测，计算牺牲阳极的剩余使用寿命，测量保护电位和检查钢管桩腐蚀状况，并对牺牲阳极保护效果进行评价和分析。     

《原油油船货油舱保护涂层性能标准》的应用研究

文章简要介绍了《原油油船货油舱保护涂层性能标准》(以下简称"货油舱PSPC"),通过与压载舱保护涂层性能标准(以下简称"压载舱PSPC")的比较,分析了货油舱PSPC与压载舱PSPC相异的技术条款对船舶建造的影响,研究了大连中远川崎船舶工程有限公司满足货油舱PSPC实施难点的对应措施。     

Corrosion analysis of bulk carriers, Part I: operational parameters influencing corrosion rates

This paper considers the physical processes of corrosion that occur in bulk carriers. Three main types of corrosive environments are identified within a bulk carrier, namely, immersion in seawater, exposure to an enclosed atmosphere, and exposure to porous media. Fundamental variables influencing corrosion in each environment of the cargo hold region, ballast tanks and void spaces are identified. These serve to identify operational parameters that affect bulk carrier corrosion. It is proposed that such parameters can be used to obtain corrosion rate databases representative of vessel operation.     

250000 DWT超大型矿砂船总体设计

上海船舶研究设计院为山东海运股份有限公司研发和设计的250 000 DWT超大型矿砂船,主要用于中国和澳大利亚之间铁矿石运输,是能够进入澳大利亚主要港口的最大型船舶。着重介绍了该超大型矿砂船的主尺度及主要参数选取、船舶快速性研究、总布置及分舱布置和压载水配置优化等。该船设计充分体现了"安全、经济、环保、舒适"的原则,满足EEDI、压载水处理等最新的国际规范规则和环保要求。     

用于船舶平衡的压载物分布和重量计算

散货船在不同货物舱装货时选择哪个压载舱来配平,在货物舱注入货物时候如何调节流量来保持船舶即时平衡,这些问题涉及到船舶的重心和稳心。本文依据力学平衡理论,选择出最优压载舱;依据船舶静态平衡理论和微积分算法,计算出装货过程中船舶变化的重心和稳心,以及船舶倾斜角度与装载货物的关系。当达到船舶允许的最大倾斜角后,操作者就必须给压载舱注入压载物以避免船舶过度倾斜。利用计算机控制阀门开度可以有效控制压载物的流量。     

毛里塔尼亚友谊港阴极保护翻新工程

介绍了毛里塔尼亚友谊港引桥及码头钢管桩原防腐系统达到设计使用年限后,在传统防腐保护方法的基础上,对腐蚀最严重的区域引进了PTC新型包覆防蚀技术。通过采取涂料、PTC包覆和牺牲阳极阴极保护三种防腐方法的有效结合,解决了水位变动区和海洋浪溅区部位腐蚀严重部位的涂料修复困难问题,保证钢管桩具有更长久、更全面、更有效的保护效果。工程实施后,保护电位测量结果表明钢管桩防腐保护效果良好,该工程设计与施工合理。     

东营港码头工程钢管桩防腐措施及应用

东营港扩建工程二号泊位承台部分桩基共有钢桩458根,为了保证工程设计使用年限,对钢管桩采取涂层和牺牲阳极联合防腐措施。经检测,保护电位满足设计要求,防腐措施科学、合理。     

船舶压载舱的牺牲阳极保护

论述了船舶压载舱产生腐蚀的原因、防腐蚀保护的方法。介绍了中国船级社有关牺牲阳极阴极保护的原则规定、设计要求、安装要求、定期检查项目。最后,将腐蚀的舱壁采用涂装或牺牲阳极阴极保护两种方法进行了经济效益对比分析,得出安装牺牲阳极阴极保护的经济效益显著的结论。     

基于专家系统的船舶配载智能控制策略

利用专家系统控制策略的思想,提出船舶装卸载分轮次序的控制原则、约束条件及实现原理。通过控制船舶的浮态提高船舶压载水的速率及排放能力,保证货物装载过程中压载水与货物操作相适应。利用专家系统的反向推理和正向推理相结合多级控制的控制策略,确定了船舶配载方案及船舶装卸载分轮次序,并提供船舶货物装卸载操作每一步的货物装舱顺序、时间及船舶浮态等性能指标,并通过实船计算验证系统的准确性和可操作性。本方法能迅速、准确地确定船舶配载方案及操作步骤,提高船舶的配载效率,避免船舶配载中的盲目性。     

晃荡要求对散货船压载舱结构的影响探讨

协调版共同结构规范（CSR-H）对散货船液舱的晃荡强度提出新的要求。针对散货船专用压载舱,通过对晃荡载荷的规范计算,并结合实船统计数据对比,探讨了基于CSR-H的晃荡要求对散货船专用压载舱结构设计的影响,包括有效晃荡长度、有效晃荡宽度和构件尺寸等。     

Analytical modelling of ship collision based on full-scale experiments

This paper presents a theoretical model allowing us to predict the consequences of ship–ship collision where large forces arise due to the sloshing in ship ballast tanks. The model considers the inertia forces of the moving bodies, the effects of the surrounding water, the elastic bending of the hull girder of the struck ship, the elasticity of the deformed ship structures and the sloshing effects in partially filled ballast tanks. The study focuses on external dynamics. Internal mechanics, presenting the collision force as a function of penetration, was obtained from experiments. The model was validated with two full-scale collision experiments, one with a significant sloshing effect and the other without it. The comparison of the calculations and the measurements revealed that the model predictions were in good agreement, as the errors at the maximum value of penetration were less than 10%.     

铝基牺牲阳极在天津港海泥中的应用

由于天津港的回淤性特质,使得一些码头(尤其是老码头)钢结构的牺牲阳极被不同程度的掩埋,导致牺牲阳极阴极保护系统使用寿命和效果降低,从而影响整个码头结构的安全和使用寿命。针对上述问题,提出了一种采用Al-Zn-In-Si系牺牲阳极复合外包填包料的海泥区阴极保护新方法,并将其应用于实际工程中。工程实践表明,该牺牲阳极阴极保护系统的保护效果良好,对解决天津港中被海泥严重掩埋的钢结构的阴极保护具有积极意义。     

大型集装箱船压载舱溢流保护系统设计和研究

减少船舶自重以增加货运量是现代造船的重要课题之一。对大型集装箱船的压载水和压载舱透气管路进行系统性优化,可以达到船舶减重、节约钢材和节能减排的目的。以某大型集装箱船为例,分别给出了货舱区域和机舱区域两种压载舱溢流保护系统的布置方案,并运用管路阻力公式计算出两种方案下压载水舱的设计载荷,结果显示优化减重效果显著。同时,还列出了两种方案的优缺点,对不适用的船只进行了说明。     

30000 DWT载货教学实习船破舱稳性研究

30000 DWT载货教学实习船是上海船舶研究设计院为大连海事大学专门开发设计的无限航区多用途船兼教学实习船。作为教学实习船,保障实习生、教师和船员的生命安全至关重要,而破舱稳性是考核该船是否足够安全的重要性能指标。分析了2008年《特种用途船安全规则》及SOLAS 2014对特种用途船和普通干货船的概率破舱稳性计算要求的区别,通过采取设计U型压载水舱和特殊布置管系及阀等措施,最终得到了较小的破舱稳性GM限制,提高了货物装运能力。