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1 INTRODUCTION

Liquefaction of cargo is a phenomenon, where a soil-

like material is abruptly transformed from a solid dry

state to an almost fluid state and this problem has

been identifying as one of the deadliest and major

cause of marine casualties in bulk carriers, often

associated with tragic loose and fatalities. Accidents

attributed to cargo liquefaction, mainly results in loss

of stability and subsequently the capsizing of the ship

[4]. The probability of liquidation of cargo in a bulk

carrier vessel, often constitute a wide range of

interaction of several contributing actions, which

often result to a complex risk environment that

increases the chances of occurrence [8]. There has been

an increasing concern over the losses of bulk carriers’

vessels, in recent time with the high fatality rate of

seafarer, and numerous regulatory efforts like the

IMSBC code by IMO has been made, but incidents

suspectedly to be caused by liquefaction continues to

occur with higher fatality rate [10]. The continuous

occurrence of this incidents leads us to question

whether the identified known causes are properly

reflected and addressed by the maritime industry. A

causal factor can be defined as any major unplanned,

unintended contributor to an incident that if

eliminated would have either prevented the

occurrence of the incident or reduced its severity or

frequency. Looking at the literature survey, several

researchers had focused on numerical evaluations and

experiments to reveal the liquefaction potential based

on the characteristics of the cargo, but limited study

had been made on the actual cause of this problem.

Hence, to fill the literature gap, this study has a

significant interest in identifying the root causal

factors of liquefaction incidents, as this will

necessitates the understanding of the interaction of

events through a chronological chain of activity

leading to the liquefaction incidents [5–7, 9, 11].

Assessment of Factors Contributing to the Risks of

Cargo Liquefication Accident in Bulk Carriers (A

Qualitative Approach)

T. Nwigwe & M. Kiyokazu

Tokyo University of Marine Science and Technology, Tokyo, Japan

ABSTRACT: Liquidation of cargo in bulk carrier has been identifying as a major hazard affecting the bulk

carrier shipping and has resulted to several loss of lives. This study assesses the liquidation problem in bulk

carrier shipping, it also discusses the mechanisms by which cargo liquefaction occurs in bulk carrier and the

factors influencing the risks of occurrence, based on a qualitative approach. Based on the findings and survey,

the unsafe storage condition, poor compliance with the testing and certification of cargoes, poor loading plan,

have been identify as some of the root casual factors influencing the risk of liquidation problem in bulk carrier.

This study will contribute to increasing the awareness and understanding of the problem of cargo liquefaction

and will facilitate the development of regulations that reflects the realities of this problem and assist in the

development of future recommendations for mitigation plans against the liquidation problem in bulk carrier.

http://www.transnav.eu

the International Journal

on Marine Navigation

and Safety of Sea Transportation

Volume 16

Number 1

March 2022

DOI: 10.12716/1001.16.01.17

150

2 THE PURPOSE OF THE STUDY

These studies assess the problem of cargo

liquefication to understand the combination of causal

factors leading to the incidence. The study is aimed at

uncovering the problem of liquidation of cargo in

bulk carrier and to increasing its awareness by looking

at the parameters influencing the risks of occurrence.

Finally, some recommendations are presented for

possibly preventing future occurrence.

3 MATERIAL AND METHOD

The study investigated the liquidation incidence using

information gathered from reviews of published

articles of incidence caused by liquification and

Interviews with expert and professionals in the

industry.

_______________________________________________

Name Position Date

_______________________________________________

1 Andrew Moore Consultancy June 2021

& Associates Ltd (Singapore) & Survey

2 Rio Tuba Nickel Minning Operations July 2021

Corporation (Philippine) worker

3 San Roque Metals Operations July 2021

Incorporated (SRMI) worker

(Philippine)

_______________________________________________

Because of all interviewed staff do not want to

disclose their names, the table do not include name of

the participants. The outcome of the information

gathered has been utilized to give a clear picture of

the problem of cargo liquefaction for understanding

the contributing factors influencing the risks of

liquidation of cargo.

4 PROCESS OF LIQUEFACTION

Liquefaction is a phenomenon in which a soil-like

material cargos are abruptly transformed from a solid

dry state to an almost fluid state. As larger particles

generally cannot retain much water and will settle

together with greater voids space between them,

while smaller particles will retain more water because

of their greater contact and increased surface, so

during the voyage of such cargo in an open seaway,

particularly during heavy weather condition, these

cargos are often subject to agitation due to the

vibration of the engine, ship’s rolling, and pitching

impacts and the resultant effect will force the

rearrangement of the cargo particle as they are being

subjected to significant stresses.

The resulting effect is the compaction of the inter-

granular spaces, and the removal of interstitial air,

and this will lead to an increasing pores water

pressure, thereby forcing the cargo solid particles to

be separated from its moisture content as (Fig 4). The

cargoes with high moisture content lose its shear

strength due to the loose of direct contact between

their particles and they become prone to sliding,

particularly when the cargo is shallow and subject to

large heel angles. These conditions will make the

cargo material to behave like a liquid and in the

resulting viscous fluid state cargo may flow to one

side of the ship with a roll but not completely

returning with a roll to the other way [1]. Liquefaction

often starts in a small portion of the cargo and rapidly

spreading throughout the entire cargo, resulting in a

sudden shifting of the entire mass and the ship may

be affected, progressively reaching a heavy list and

loss of control, which could result in the vessel

capsizing and sinking in the worst-case scenario due

to lack of stability.

Figure 1. Compaction and subsequent liquefaction

4.1 Cargo prone to liquefaction

Liquefaction may occur in the cargoes categorized in

Group A of the Code of safe practice for solid bulk

Cargoes（BC Code）such as iron ore fines, nickel ore,

coal, particularly when they are loaded in condition

where their moisture content exceeds the

transportation moisture limit value of the cargo [2, 3].

Figure 2. Variation in particle sizes of ores

The granular cargo materials are often consisting

of varying particle sizes and may contain water within

them, which were accumulated during mining

process of the cargo or during storing them on

grounds that are exposed to weather while awaiting

loading. These cargo materials have the characteristic

of cohesion, and may liquefy during voyage, even if

they are cohesive and trimmed levelly. Most of the

popular cargo materials involve in this incident are

briefly outline below.

4.1.1 Nickel ore

The largest exporters of nickel ore are Indonesia and

the Philippines, and these ores are extremely low-

grade ore, with nickel content as low as 1% and the

remaining 99% are fine grained, almost like mud with

traces of nickel ore. Nickel ore are often dug from

open pit mines, hence exposing the fine-grained nickel

ore to wet weather, and increasing their moisture

content and are arguably the most dangerous of all

151

bulk cargoes, suspectedly to have claimed the highest

number of fatalities.

4.1.2 Iron ore fine

Iron ore fine have been associated with several

liquefaction accidents. These are iron ore with larger

proportion of smaller particles and may liquefy if

their moisture content exceeds their TML. The open

mining and storing of the iron ore fine in certain

milling sites prior to loading increase the moisture

content.

4.1.3 Bauxite

Bauxite, which consists of oxide type ores containing

hydrated alumina is mainly used to produce

aluminum. The largest exporters of bauxite ore are

Australia and guinea They are mined in open pit

mines, then converted to alumina (aluminum oxide),

which are further processed to pure aluminum by

electrolysis.

5 RESEARCH FINDINGS

Based on the expert consultation and study of the

available report of incidence suspectedly caused by

liquification of cargo, several actions were identified

to influence the risks of the liquefaction incidence.

Although, the errors resulting from these actions are

independent from one another, but human factor is

the basis of all of them. Below illustrate the key

findings and problem areas.

1. Lack of proper cargo inspection

The cargo is usually stockpiled and transferred in

open barges and trucks and in the event of poor

climate or raining weather, the moisture content

can be increased, creating more chances for cargo

liquefaction. Also, the tropical climatic condition

has a higher moisture content that can be absorbed

by the stockpile’s cargoes of fine-grained minerals

prior to loading, as it has a higher moisture content

that can be absorbed by the stockpile’s cargo prior

to loading.

2. Non-implementation of rules

The neglect for regulation is the main causal

factors in most liquefaction incidence. The

International Convention for the Safety of Life at

Sea, 1974 and its Protocol of 1988, Chapter Ⅵ

(Carriage of Cargoes) (Regulation 1, 2, 7 and 4)

have provided rules and standards for the safe

transportation of solid bulk cargoes. The duties of

all concerned supervising parties, from the

submission of information on cargo, the proper

stowage and down to the shipper’s duty to submit

information about cargo to the master were stated.

Also, where the requirement to load and trim bulk

cargoes to a reasonable level, as necessitated by the

boundaries of the cargo space, to minimize the risk

of shifting and to maintain adequate stability. But,

despite the provisions of code, majority of the

milling yard located in developing countries, had

always neglect the provision.

3. Poor knowledge of cargo

The wrongly categorization of iron ore fine as

normal iron ore, which according to the IMSBC

Code, are cargo that poses no liquefaction risk are

linked to most liquefaction accidents. Also, the

wrong labeling of cargo in the IMBSC code such as

bauxite, whose material behavior are not well

understood, may increase the risk of cargo

liquefaction as most workers are ignorant of their

characteristic’s behavior. Although, bauxite is

listed under Group C cargo in the IMSBC Code,

meaning that it poses neither chemical nor

liquefaction risks, but they sometimes behave like

Group A due to their material behavior. Their

listing in the Group C only covers relatively dry

and relatively coarse-grained bauxite but if the

bauxite has a large proportion of powder, or if the

moisture content is above 10%, the cargo is

potentially unsafe and behave like Group A.

4. Lack of functional equipments

This problem is related to poor tmt testing

materials resulting to incorrect result are the main

causal factor. The lacks proper equipped facility to

perform the necessary testing required for

preventing cargo liquefaction. lacks proper

equipped and facility for performing the necessary

TML test which is required to prevent cargo

liquefaction. The procedures for testing the

moisture content by IMO were generated for

concentrates ore and not for fine ore, and in this

case testing methods for calculating the

transportable moisture limit of the cargo can be

characterized as inadequate and often result to a

wrong result.

5. Problem of working condition

The practices like the open storage of the ore

material prior loading, especially in the humid

climate can contribute to increasing the moisture

content of the cargo. Also, most of the mines are in

very remote areas, and often engage in an

improper loading condition of which makes TML

testing difficulty and the locations of the ports

where these materials are loaded When any of

these types of cargoes is to be transported by sea in

a solid bulk state, the TML should be determined.

For a general cargo vessel, each of these cargoes

must be loaded for transportation only when the

Moisture Content of the cargo is lower than TML

6 DISCUSSION

The continuous efforts towards safeguarding against

liquefaction problem in bulk carrier has led to the

implementation of the IMSBC Code. The IMSBC Code

introduces the upper bound of moisture content of

cargo called the Transportable Moisture Limit (TML).

The TML is defined as 90% of the Flow Moisture

Content (FMP), which depends on the characteristics

of cargo and should be measured experimentally.

However, the objective of this code has not been fully

achieved as certain human negligence resulting to the

poor enforcement of the regulation continue to occur.

The IMSBC Code's stated the application

requirements and oblige the shippers to test and

declare the properties and moisture content of the

cargo, verification of the vessel's safety was to be

confirmed by the tripartite agreement of the Port State

of the exporting country, Port State of the receiving

152

country and Flag State of the vessel and the master of

the vessels was confirmed all test result and ensure

the proper loading and monitoring of the vessel. But

unfortunately, based on available report of cargo

liquidation incidents and the interview from experts

involved in the industry, there has been failure in

most of the operation activities lading to the risks of

accident. It is evident from recent accident statistics

that most of the accident relating to liquefaction like

the Emerald Star (2017), the Nur Allya (2019) occurs

in developing countries, particularly in southeast Asia

of Indonesia and Philippines and are attributed to

improper human actions and wrong TML testing

result of the cargo. These contributing factors which

include human actions negligence like the poor

compliance with the testing certification of cargoes,

unsafe storage condition, insufficient loading plan

and lack of proper monitoring from relevant parties,

has been identify as some of the factors increasing the

risks of liquidation and can be seen as a major

legislative gap in the implementation of provision of

the code.

7 CONCLUSION

The present study discusses the problem of cargo

liquefaction in bulk carrier and assess the contributing

factors influencing the continuous occurrence of this

problem. Although, several efforts have been made to

manage this problem, but accident suspected caused

by cargo liquefaction continue to occur, but human

errors, operation errors and regulation negligence

during the loading and testing operation are the

contributing factors to liquefaction of cargo incident.

It may be concluded that there are several

contributing factors influencing the continuous

occurrence of this problem is can be traced to poor

operation human negligence. The successful

prevention of this problem will be achieved when

proper measures are taken before cargo loading

operation, during loading process, at the completion

of loading and during the voyage of the vessel which

will all depend on the cooperation of relevant parties

involve doing their job efficiently.

ACKNOWLEDGMENT

The author is grateful to Professor Minami Kiyokazu for his

assistance and support towards this research

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