您现在的位置: 纽约时报中英文网 >> 纽约时报中英文版 >> 商业 >> 正文

危险的沙石:货轮沉没的隐性杀手

更新时间:2018-10-4 10:39:33 来源:纽约时报中文网 作者:佚名

The cargo ships that 'liquefy'
危险的沙石:货轮沉没的隐性杀手

Think of a dangerous cargo, and toxic waste or explosives might come to mind.

提起危险货物,你可能会想到有毒废物或者爆炸品。

But granular cargoes such as crushed ore and mineral sands are responsible for the loss of numerous ships every year. On average, 10 ‘solid bulk cargo’ carriers have been lost at sea each year for the last decade.

但是粉碎的铁矿石或沙子这样的散粒货物每年造成的沉船难以计数。过去十年中平均每年有10艘载运固体散装货物(solid bulk cargo)的船舶在海上沉没。

Solid bulk cargoes – defined as granular materials loaded directly into a ship’s hold – can suddenly turn from a solid state into a liquid state, a process known as liquefaction. And this can be disastrous for any ship carrying them – and their crew.

固体散装货物指直接装在船舱内的颗粒状物质,能忽然从固态变成液态,这一过程叫做液化,会对装载货物的船舶以及船员造成毁灭性打击。

In 2015, the 56,000-tonne bulk carrier Bulk Jupiter rapidly sunk around 300km (187 miles) south-west of Vietnam, with only one of its 19-strong crew surviving. This prompted warnings from the International Maritime Organisation (IMO) about the possible liquefaction of the relatively new solid bulk cargo bauxite (an aluminium ore).

2015年,一艘56,000吨的货轮散货木星号(Bulk Jupiter)在越南西南方约300公里(187英里)处迅速沉没,19名船员仅有一名幸免于难。对此国际海事组织(IMO)发出警告,新型固体散装货物铝土矿石可能会液化。

A lot is known about the physics of the liquefaction of granular materials from geotechnical and earthquake engineering. The vigorous shaking of the Earth causes pressure in the ground water to increase to such a level that the soil ‘liquefies’. Yet despite our understanding of this phenomenon, and the guidelines in place to prevent it occurring, it is still causing ships to sink and taking their crew with them.

通过地质和地震工程,人们了解了不少颗粒状物质液化的原理。土地发生强烈震动导致地下水压力上升,以致于土壤发生“液化”。尽管我们理解这一现象,且有防止发生液化的指导原则,但液化导致船舶沉没以及船员丧生的事仍在上演。

Solid bulk cargoes are typically ‘two-phase’ materials as they contain water between the solid particles. When the particles can touch, the friction between them makes the material act like a solid (even though there is liquid present). But when the water pressure rises, these inter-particle forces reduce and the strength of the material decreases. When the friction is reduced to zero, the material acts like a liquid (even though the solid particles are still present).

固体散装货物是典型的“两相”物质,固体粒子间含有水。当粒子可以接触时,其间的摩擦力使“两相”物质像固体一样(虽然还有液体)。但当水压力上升时,粒子间作用力减少,物质强度降低。当摩擦力降低到零时,“两相”物质就像液体一样了(虽然还有固体粒子)。

A solid bulk cargo that is apparently stable on the quayside can liquefy because pressures in the water between the particles build up as it is loaded onto the ship. This is especially likely if, as is common practice, the cargo is loaded with a conveyor belt from the quayside into the hold, which can involve a fall of significant height. The vibration and motion of the ship from the engine and the sea during the voyage can also increase the water pressure and lead to liquefaction of the cargo.

在码头上看似稳定的固体散装货物之所以会液化是因为装上船后粒子间水的压力升高。尤其是,通常情况下,货物是通过传送带从码头运上船的,高度会骤然降低。来自船舶引擎以及航行中大海的震动和运动也会使水压升高,导致货物液化。

When a solid bulk cargo liquefies, it can shift or slosh inside a ship’s hold, making the vessel less stable. A liquefied cargo can shift completely to one side of the hold. If it regains its strength and reverts to a solid state, the cargo will remain in the shifted position, causing the ship to permanently tilt or ‘list’ in the water. The cargo can then liquefy again and shift further, increasing the angle of list.

当固体散装货物液化时,它会在船舱内流动,船体因此变得不那么稳定。液化的货物可能完全流到船舱的一侧。如果重新变回固态,货物会保持在移动后的位置,造成船体永久倾斜。货物可能会再一次液化、移动,倾斜角度变得更大。

At some point, the angle of list becomes so great that water enters the hull through the hatch covers, or the vessel is no longer stable enough to recover from the rolling motion caused by the waves. Water can also move from within the cargo to its surface as a result of liquefaction and subsequent sloshing of this free water can further impact the vessel’s stability. Unless the sloshing can be stopped, the ship is in danger of sinking.

当倾斜角度大到一定程度时,水会通过舱口进入船身或者船体无法在翻滚的波浪中恢复平衡。由于液化,水到处流动,也可能从货物内部流到表面,影响船体的稳定性。除非能阻止流动,船只都会面临沉没的危险。

The International Maritime Organisation has codes governing how much moisture is allowed in solid bulk cargo in order to prevent liquefaction. So why does it still happen?

为了防止液化,国际海事组织规定了固体散装货物能含有多少水分。但为何这种情况仍在发生?

The technical answer is that the existing guidance on stowing and shipping solid bulk cargoes is too simplistic.

专业的回答是,现有的关于储运固体散装货物的指导原则太过简单。

Liquefaction potential depends not just on how much moisture is in a bulk cargo but also other material characteristics, such as the particle size distribution, the ratio of the volume of solid particles to water and the relative density of the cargo, as well as the method of loading and the motions of the vessel during the voyage.

液化可能不只取决于散装货物水分含量,而且取决于其它物质特征,比如粒子大小分布,固体粒子与水分的比例,货物相对密度,装载方法以及船只航行中的姿态。

The production and transport of new materials, such as bauxite, and increased processing of traditional ores before they are transported, means more cargo is being carried whose material behaviour is not well understood. This increases the risk of cargo liquefaction.

新材料的生产和运输,比如铝土矿,以及传统矿石在运输前的深加工,意味着越来越多货物的材料属性我们还没能了解。这增加了货物液化的风险。

Commercial agendas also play a role. For example, pressure to load vessels quickly leads to more hard loading even though it risks raising the water pressure in the cargoes. And pressure to deliver the same tonnage of cargo as was loaded may discourage the crew of the vessel draining cargoes during the voyage.

商业日程也是原因之一。比如,快速装货的压力导致硬装,造成货物水压升高的风险。装载和运达货物的重量必须相同,这让船员不敢在航行中把液化的货物排出去。

To tackle these problems, the shipping industry needs to better understand the material behaviour of solid bulk cargoes now being transported and prescribe appropriate testing. New technology could help. Sensors in a ship’s hold could monitor the water pressure of the bulk cargo. Or the surface of the cargo could be monitored, for example using lasers, to identify any changes in its position.

为了应对这些问题,船运业需要更加深入地了解所运输的固体散装货物的材料属性,并进行适当的测验。新科技会有所助益。船舱内的传感器可以监控散装货物的水压。或者监控货物表面,比如用激光识别有没有位置变化。

The challenge is developing a technology that is cheap enough, quick to install and robust enough to survive loading and unloading of the cargo. If these challenges can be overcome, combining data on the water pressure and movement of the cargo with information on the weather and the ship’s movements could produce a real-time warning of whether the cargo was about to liquefy.

关键在于研发出便宜,安装迅速并且足够结实能耐得过货物装卸的技术。如果能够战胜这些挑战,将水压和货物运动的数据与天气和船体运动的信息结合在一起,就能够发出货物是否会液化的实时警告。

The crew could then act to prevent the water pressure in the cargo rising too much, for example, by draining water from the cargo holds (to reduce water pressure) or changing course of the vessel to avoid particularly bad weather (to reduce ship motions). Or if that were not possible, they could evacuate the vessel. In this way, this phenomenon of solid bulk cargo liquefaction could be overcome, and fewer ships and crew would be lost at sea.

接着船员能够阻止货物水压过高,比如,排出货物舱内的水(降低水压)或者改变航行路线来规避极度恶劣天气(减少船体运动)。如果可能的话,还可以清空船舶。这样就能够克服固体散装货物液化的问题,船只沉没和船员丧生失踪的事件就会减少。

“全文请访问纽约时报中文网,本文发表于纽约时报中文网(http://cn.nytimes.com),版权归纽约时报公司所有。任何单位及个人未经许可,不得擅自转载或翻译。订阅纽约时报中文网新闻电邮:http://nytcn.me/subscription/”

相关文章列表