Liquefaction: what you need to know
The shipping industry has been aware of the hazards of liquefaction for over a century. However, it still continues to be a major problem for cargo vessels despite updated procedures and amended legislation.
What is liquefaction?
The process takes place at a molecular level but it has a dramatic impact on the properties of solid cargo. Mining means that granular materials contain moisture in the form of water between particles and it’s the friction between these particles that causes problems.
How the cargo is stored and transported will have an effect on how this moisture behaves. Movement and vibration reduce the space between particles, increasing the pore water pressure and causing the dry cargo to act like a liquid. This is liquefaction.
Liquefied bulk can shift inside the hold and solidify again several times which causes the ship to list. Water can then enter the hull from hatch covers or, in the worst-case scenario, the ship will be unable to cover from a roll.
This is exactly what happened to the Bulk Jupiter when liquefaction caused the vessel to sink off the coast of Vietnam in 2015. The loss of 18 of its 19 crew members prompted the IMO to release a warning about liquefaction for ships carrying cargoes of bauxite.
Unfortunately, this was not an isolated incident. In the last ten years, liquefaction has resulted in the loss of another vessel carrying bauxite, 6 ships carrying nickel ore and 2 more that were carrying clay.
According to the Bulk Carrier Casualty Report from Intercargo, there was a total of 202 lives lost between 2008-2017. Liquefaction or cargo shift was responsible for 101 of them – exactly half. It was the highest single cause of seafarer deaths in the years studied.
UPDATE: All contacts lost with bulk carrier NUR ALLYA since Aug 20 2019, last known position was in Banda Arc N of Ambon, capital of Maluku province, Indonesia.
Bulk carrier with 25 crew and cargo of nickel ore was en route from Weda island, North Maluku, to Morosi, southeast Sulawesi. SAR launched on Aug 25, there was no distress signal. Most probably, it was ore liquefying, causing capsizing and sinking.
The last known location of the Nur Allya was reported to be approximately 44 nautical miles from Namlea, Indonesia, located off the north-east coast of the island of Buru.
Indonesia’s Ministry of Transportation said the ship was underway from the Sepo Port area on the Indonesia island of Halmahera to the Port of Morose in southwest Sulawesi, Indonesia.
Nickel ore has earned the reputation of being perhaps the world’s deadliest cargo because of its liquefaction properties, especially when exposed to wet conditions. Cargo liquefaction can result in a vessel to lose stability and even capsize at a moment’s notice.
Due to the increasing concerns about the dangers of liquefaction, The International Maritime Solid Bulk Cargoes Code (IMSBC Code) was amended in January this year. The recent changes include:
- A new test procedure for determining the Transportable Moisture Limit (TML) of coal.
- Specification that the ship operator is responsible for the testing and sampling of TML and moisture content.
- Strengthening and clarifying the designation of coal as Group A and B cargo in the Individual Coal Schedule.
The dangers of liquefaction are increased even further by faulty hatch covers. If a ship is already listing, water ingress can tip the balance and result in sinking.
Unfortunately, poorly maintained or defective hatch covers are widespread in the shipping industry. Over 40% of all P&I claims are due to damaged cargo – worth an estimated $46.9m per year. The 50 million GT, A- rated North of England P&I club says that it continues to experience three to four claims each year valued between US$ 500,000 and US$ 1,000,000 for water-damaged cargoes resulting from hatch cover defects.
The responsibility for hatch covers again lies with the ship’s operator. The ‘Standards for Owners’ Inspections and Maintenance of Bulk Carrier Hatch Covers’ states that: ‘more attention should be paid to hatch cover securing mechanisms and the issue of horizontal loads, especially with regard to maintenance and frequency of inspection.’
Gaskets, seals, retaining channels and resting pads are all subject to wear and tear so monitoring is essential to make sure they’re kept weather tight. Regular checking and maintenance is much cheaper and more effective than major repairs or incidents caused by neglect.
Ultrasonic testing is the most effective way of making sure your hatches are functioning correctly. It’s much more accurate than water-hose leak detection and chalk testing as it shows when you have the required compression and provides a precise location for any leakages.
In terms of efficiency, ultrasonic testing equipment can be easily stowed and carried on a ship so that you can check your hatch covers regularly. The tests can be carried out by one person and doesn’t rely on the hold being empty so they won’t interrupt your operations.
Hatchtite is even more low-maintenance as it has a runtime of 40 hours and only needs calibrating after five years instead of the usual one. It’s also Type Approved by ABS, fully compliant with IACS Unified Requirement U.R.Z17 and approved by insurers and P&I clubs.
Contact us to find out more about liquefaction and how we can help keep your crews and vessels safe.