Rice, despite being a seemingly ordinary commodity, poses unique dangers when transported by sea.
The core of this danger lies in a little-known physical concept — the angle of repose.
The angle of repose defines the maximum angle relative to the horizontal plane at which an object can remain stationary without sliding, crucially overcoming static friction with dynamic friction.
As a granular substance, rice is subject to the laws governing the angle of repose.
At sea, ships inevitably experience rolling and pitching, which can cause cargo to tilt during transport.
When the tilt angle of rice is less than its angle of repose, static friction can prevent further movement and keep it stationary.
However, if the tilt angle exceeds the angle of repose, static friction fails to prevent rice from shifting, leading to a change in the ship's center of gravity.
Since rice cannot immediately return to its original position, the ship loses its self-stabilizing ability, greatly increasing the risk of capsizing.
This situation is not unique to rice; other dry bulk cargoes face similar risks.
Recalling the 2014 sinking of the Bulk Jupiter, which was carrying bauxite bound for Malaysia, inadequate consideration of continuous rainfall during loading resulted in bauxite exceeding safe moisture levels for transport.
Despite encountering a tropical storm and severe rolling, the ship lost balance, ultimately leading to a tragic sinking.
Bauxite, when exposed to moisture, shifts from a powdered substance to a solid-liquid mixture, making it more susceptible to shape changes and accumulation during ship rocking.
This directly shifts the ship's center of gravity, exacerbating the risk of sinking.
One might ask why not use bagged rather than bulk transport if bulk transport carries such high risks?
Bagged transport reduces the likelihood of cargo being affected by the angle of repose during transport.
In practice, despite the risks of shifting that bulk transport entails, these risks are much lower than those of air transportation disasters.
Therefore, based on economic and efficiency considerations, bulk transport remains the more common choice.
Bulk transport not only saves on packaging costs but also allows for direct loading and unloading using vacuum suction or grab equipment, saving on labor costs and time.
To mitigate risks during bulk cargo transport, the maritime industry employs specially designed bulk carriers.
These ships' holds undergo special treatment, with reinforced structures at the corners and compartmentalized holds using binning techniques to minimize cargo shifting and changes in the ship's center of gravity during operation.
These specialized bulk carriers also feature filling ports to maximize hold space utilization, ensuring cargo loading tightness and stability.
This design significantly reduces the risk of cargo movement during navigation, effectively ensuring the safety of both the ship and its cargo.
In conclusion, despite the inherent risks of transporting rice and other bulk cargoes by sea, these risks can be effectively controlled and mitigated through proper design and professional management.
The economic viability and efficiency of bulk transport make it an indispensable part of maritime shipping today, whether for cost savings or improved transport efficiency, making it a prudent choice.
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