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‘Can test’ can save lives
Over the past decade, at least 100 seafarers are known to have lost their lives due to incidents which have been attributed to bulk cargoes liquefying at sea.
Excessively wet cargoes in their ships’ holds can turn quickly to an uncontrollable fluid when under way, resulting in catastrophic capsizes with little warning. Most of the deaths were on ships carrying seemingly solid nickel ore cargoes, but the risk is equally great where cargoes of iron and aluminium ore (bauxite) as well as coal contain undetected and unsafe levels of moisture
More tragic still is that the deaths could have been prevented if a simple test had been carried out and acted upon before the ships left port. The so-called ‘can test’ is exactly what it says: put some cargo in a can, bang it on the ground for a minute and see if the contents start to flow.
If they do, stop the loading and get some proper laboratory tests done – regardless of what it says on the cargo documentation.
These seven videos, which UK P&I Club Loss Prevention has produced in partnership with global cargo experts Minton Treharne & Davis (MTD), explain what a can test is and what it looks like in practice.
An introduction from Allan Ashby – Head of MTD’s solid cargo survey department
In the first video, Allan Ashby – head of MTD’s solid cargo survey department – explains how the can test is specified in the International Maritime Solid Bulk Cargoes as a complementary check for ‘determining the possibility of flow of the cargo’.
Basically you need to find a cylindrical can of 0.5 to 1 litre, half-fill it with a representative sample of the cargo, bang the half-filled can 25 times onto a hard surface from a height of 20 cm at 1–2 second intervals, check the contents for signs of liquefaction, then repeat with further samples throughout the loading.
If more than one of the samples ‘fails’ – that is starts to flow – stop the loading and arrange to have the cargo tested in a laboratory to determine its moisture content and whether this is above or below its safe transportable moisture limit.
But Ashby also warns the can test is not infallible – cargo which passes may still have an unsafe moisture content. If you have any doubts about the appearance or condition of the cargo – such as it looks muddy or clay-like, or spatters when dropped – stop the loading and get laboratory tests.
Iron-rich fine material
Iron ore fines
The next six videos demonstrate the can test for samples of three different types of bulk cargo: coal (videos 2 and 3), iron-rich fine material (videos 4 and 5) and iron ore fines (videos 6 and 7).
For each material, you can see one sample passing the can test (videos 2, 4 and 6) and one sample failing (videos 3, 5 and 7).
Passing the test means the sample shows no sign of free moisture on the surface. It looks dry and crumbles easily, and does not move when you tip or shake the can.
Failing the test means, the sample shows signs of free water at the surface, and the surface itself has become flat and level. The surface may also move when the can is tipped or shaken. This cargo will most likely liquefy at sea and you should not load it without independently verifying its moisture content and transportable moisture limit.
If you do otherwise, you will be leaving the ship and its crew in very real danger.