Liquefaction – Are your hatches putting you at risk?

liquefaction

Your bulk cargo carrier could be at risk of liquefaction.

What is liquefaction?

Granular materials loaded onto a ship hold can turn into a liquid state – which can be disastrous for your ship and crew.

Solid bulk cargo often contains water between solid particles. Present from mining, this moisture level can rise through transport and storing.

Friction between these particles makes these particles act like a solid, despite the liquid presence.

Ship vibrations and movements cause the space between the particles to reduce, increasing pore water pressure. If the pore water pressure increases enough, the “dry” cargo begins to act like a fluid due to the loss of friction between the particles.

The risk to life

The liquefied bulk can shift inside the hold and can solidify again in a shifted position.

This shift can cause the ship to list. If the cargo liquefies again, the angle of the list can increase. At this point, water can enter the hull via hatch covers, or the ship may be unable to recover from a roll.

Water from the liquefied cargo can also move towards the surface, causing further instability.

This happened to the Bulk Jupiter, which sank 300km off the coast of Vietnam.

Only one crew member survived.

The IMO issued warnings over possible liquefication of a solid bulk aluminium ore, Bauxite.

The answer

Beginning at the source, the method for storing, transporting and method of loading can affect the state of the solid bulk cargo.

Hard loading, to load cargo faster, increases the risk of raising pore water pressure. During transit, crews can be put off from draining cargo due to pressures to deliver the same tonnage as was loaded.

Technology may hold the answer, such as sensors to measure cargo water pressure or laser observers.

The problem lies in finding a technology cheap enough, yet also performs to a high enough standard to inform the crew of the dangers in real time.

Once water pressure increase had been detected the crew can look to drain cargo water, change course to reduce motion, or even evacuate the ship.

Summary

Liquefaction is not a new phenomenon – we’ve been aware of it for over a century.

Technology, storage and loading procedures alone aren’t currently in a place where they can reduce the risk of liquefaction. There would be a need for several cross-industry changes to take place.

Hatches can be a cause of sinking should a ship list due to water ingress, never mind the damage to cargo – which makes up over 60% of P&I loss claims.

Traditional methods of testing the tightness of hatches can be unreliable and time-consuming. Only ultrasonic testing ensure hatches are secure at all times.

You can download our whitepaper on hatch cover testing here.