Figure 2 - Padang Hawk
holds and tanks
Between 17 and 23 July 1999, the Singapore flag bulk carrier Padang Hawk loaded a full cargo of nickel ore from barges at Kouaoua, New Caledonia. Late on 23 July 1999, the ship sailed for Townsville, Australia. During the passage, the Padang Hawk was subjected to rough seas and rolled heavily. At about 22:00 on 26 July 1999, the bulk carrier developed a 15o list to port. A quick examination of the holds showed that the cargo in four of the five holds had settled and appeared to have liquefied. Some water was pooling on the surface of the cargo in number 1 hold. The cargo in the forward holds appeared to be ‘flowing’ with the movement of the bulk carrier. The master reduced speed and altered course to put the wind and seas on the bulk carrier’s port quarter. Ballast was then pumped to correct the list. The bulk carrier’s course was maintained so that it entered the inner route of the Great Barrier Reef by Grafton Passage rather than the more southerly Palm Passage. The bulk carrier finally arrived safely in Townsville, Australia at 20:00 on the evening of 28 July 1999.
Details of Ship
|| Padang Hawk
| IMO No.
| Classification Society
|| Nippon Kaiji Kyokai
| Vessel type
|| Bulk carrier
|| Singa Star Pte Ltd
| Year of build
|| Mitsui Engineering and Ship Building, Japan
| Gross tonnage
|| 27 011
| Summer deadweight
|| 46 635 tonnes
| Length overall
|| 189.80 m
| Breadth, moulded
|| 31.00 m
| Draught (summer)
|| 11.60 m
|| Mitsui Man B&W 6S50MC
| Engine power
|| 6 532 kW
| Service speed
|| 14 knots
|| 20 (Filipino)
The Singapore flag Padang Hawk is a 46,635 tonne deadweight ‘geared’ bulk carrier, owned by Singa Star Pte. Ltd. of Singapore. The ship was built in 1995 by Mitsui Engineering and Ship Building of Japan and is classed with Nippon Kaiji Kyokai (NK). Padang Hawk is 189.8 m in length overall, has a beam of 31 m and a summer draught of 11.6 m. Propulsive power is delivered by a six-cylinder Mitsui MAN B&W 6S50MC slow-speed diesel engine developing 6 532 kW. The main engine drives a single fixed pitch propeller, which provides a service speed of 14 knots. Electrical power is provided by three Daihatsu 6DL-20 generators, each producing 480 kW. The engine room and accommodation superstructure are located at the after end of the vessel, (aft of frame 37). There are five cargo holds; with the exception of number 1 hold at 17.6 m, all are 20.8 m in length and extend to the collision bulkhead at frame 216. The ship has four cranes to service the five holds when ship’s equipment is required for loading or discharging.
At the time of the incident, the shipowners held a current International Safety Management Code (ISM Code) document of compliance for bulk carriers, issued by NK on 24 March 1998, under the authority of the Government of the Republic of Singapore. Padang Hawk had been issued with a Safety Management Certificate on 28 April 1998 by NK.
Padang Hawk is a regular caller at Townsville with cargoes of nickel ore. The ship carried a cargo of nickel ore from the port of Nakety, New Caledonia to Townsville on the previous voyage, number 903. Padang Hawk was to return to Kouaoua, New Caledonia, on voyage number 904 to load another cargo of nickel ore for shipment to Townsville. The master and mate joined the ship at Townsville at the completion of the voyage number 903. They were both experienced in bulk carrier trades and the master had previously commanded a smaller bulk carrier carrying nickel ore on coastal voyages around New Caledonia.
In 1986, Queensland Nickel Pty Ltd (QNPL) started importing limonitic nickel ore for its nickel and cobalt refinery at Yabulu, 25 km north-west of Townsville. The Yabulu refinery utilises nickel ore from the Philippines, Indonesia and New Caledonia. At the time of the incident, in excess of 27.4 million tonnes of ore had been carried in 577 vessels into the port of Townsville.
The Philippines, Indonesia and New Caledonia are estimated to contain 35% of the world’s nickel resources. The nickel occurs in ‘laterite’ deposits, which have been formed by the deep weathering of ultramafic rocks. Typically, the laterite deposits have an upper zone in which the nickel is combined with iron oxides (limonite zone), and a lower zone where the nickel occurs in complex magnesium rich silicates (saprolite zone). Limonite generally contains around 1.5% nickel, and saprolite around 2.5% nickel.
Laterite deposits are mined using ‘open cut’ methods. The limonitic and saprolitic ores are mined together and the ores are graded and stockpiled separately. Mine site stockpiles generally consist of ‘windrows’ where the ore is dumped in rows of small piles and turned regularly to aid the drying process. Once the ore has been dried sufficiently, it is transported to larger stockpiles at the ship-loading facility. The ore in many shallow water ports, including Kouaoua on the east coast of New Caledonia, is loaded onto barges at the ship loading facility and transported out to ships at anchor in deeper water. The ship’s cranes are then used to load the ore from the barges into the cargo holds.
The refining processes for limonitic and pure saprolitic ores are different owing to their differing mineral properties. QNPL utilises ore largely from the limonite zone, excluding pure saprolitic ores. The ore is
discharged from ships in the port of Townsville then transhipped by train to the Yabulu refinery where an ammonia leach process is used to refine the ore. Saprolitic nickel ores are refined using a smelting process. A large proportion of the saprolitic ores mined in the Philippines, Indonesia and New Caledonia are shipped to Japan.
Figure 5 - Padang Hawk
’s passage to Townsville
Figure 6 and 7 - Padang Hawk
’s Cargo, hold number 1 (two views)
Figure 8 - Padang Hawk
’s Cargo, hold number 3
Padang Hawk sailed from Townsville on the evening of 13 July 1999 and arrived at the anchorage at Kouaoua, New Caledonia at 12:24 on 17 July 1999. Loading of ore from shore barges commenced at 14:40. The ship’s cranes were manned by shore labour and loading from the barges was carried out from about 05:00 each morning until about 20:30 in the evenings. With the exception of one morning, when there were a few hours of light drizzle, the weather was fine throughout the loading operation. Soundings of the cargo holds for water were taken each day and no bilge During the loading operation, the ship’s
crew noticed that some ‘grabs’ of cargo
had water running from them as they were
lifted out of the barges and into the ship’s
The cargo loading was completed at 21:40
on 23 July 1999. The crew stated that the
hatches were then closed and secured by
the hatch cleats. Following a draught
survey, a pilot embarked and [[Padang
Hawk]] sailed from Kouaoua at 23:07, at a
draught of 11.85 m fore and aft.
After the pilot disembarked in the early
hours of 24 July 1999, the master set a northerly
course along the east coast of New Caledonia. The planned route was to take
Padang Hawk north of Récifs
d’Entrecasteaux, west through the Coral
Sea, north of Bampton Reef and Marion
Reef, to Palm Passage and Townsville (Figure
At 17:00 on 24 July 1999, the bilges of all holds
were pumped dry. The ships log-book
records the course as 303o with the ship
rolling heavily in a south-easterly swell.
The passage proceeded as planned. Just
before 24:00 on 24 July 1999, north of Récifs
d’Entrecasteaux, Padang Hawk altered
course to a true heading of 265°, making
good a speed of 13 knots. The wind was
noted as being east-south-east, force 5, and
the sea was described as rough. The vessel was rolling and pitching heavily in
a south-easterly swell. At 0900 on
25 July 1999, the bilges in all holds were again
pumped. The rough conditions caused the
vessel to roll and pitch heavily, particularly
from 16:00 onwards on 25 July.
At 08:30 on 26 July 199, the bilges in all holds
were pumped. The vessel was still rolling
heavily in the southerly swell and strong
winds that had veered to south to southwesterly.
At noon on 26 July 1999, [[Padang
Hawk]] was in position 18o 11’ S 153o 56’
E, about 100 nautical miles east-north-east
of Marion Reef. Over the preceding day,
the average speed had been 12.7 knots.
During the afternoon, the wind strength
was logged at force 5 with regular notations
in the logbook concerning the ship’s
heavy rolling. Throughout the day, from
time to time, seas broke over the deck and
hatch covers. By 20:00, the wind was
logged at force 6–7 and the vessel was
rolling heavily. The hold bilges were
pumped at 20:00 and again at 21:00.
At 22:00, or a little before, Padang Hawk
suddenly developed a 15o list to port. The
master, who was in his cabin, immediately
went to the bridge and joined the second
mate and lookout. The master altered
course from 265o to 295o to bring the
wind and sea on to the port quarter and
reduced the engine revolutions from 110
RPM to 100 RPM.
The master mustered all the crew. In the
dark, with seas breaking over the port side
and the ship rolling heavily about the
angle of the list, there was general concern
and a very high level of apprehension
amongst all the crew.
The master sent the mate, boatswain and
some deck ratings to check the hatches
and the state of the main deck. The crew
checked and found the cargo hatches and
the small hold access hatches secured.
They opened an access hatch to each of
the holds in turn. They found that the
cargo in all but number 5 hold had settled
and shifted to port. The cargo in the first
3 holds appeared to be semi-liquid, ‘like
melted ice cream’ as the boatswain
The master decided to ballast starboard
side tanks to correct the list. Numbers 3
and 5 starboard topside tanks were filled.
The master sent a radio message to the
‘designated person’, as described in the
ship’s ISM Code documentation. The
message detailed the situation and the
remedial action taken. A message was
also sent to the ship’s agent in Townsville,
who informed the [[Australian Maritime
Safety Authority]] of the ship’s message and
the report that the cargo had liquefied.
At 01:45, the master received a reply from
the vessel’s owners advising him to use
double bottom tanks to correct the list.
The message noted that countering lists by
using topside tanks had caused vessels to
capsize and it continued:
Although your vessel is having very high
GM due to dense cargo, still high risk of
cargo shifting to one side with the roll is
The ship’s list had been reduced to about
5o by the early morning. The strong wind
and heavy swell continued and seas broke
regularly over the vessel’s quarter.
Because of the heavy swell, the master
decided to wait before turning toward Palm Passage. The cargo hold bilges were
pumped at regular intervals throughout the
day. The disposition of ballast was adjusted
in accordance with the advice from the
At noon on 27 July, Padang Hawk was at
position 17o 16’ S 148o 58’ E. The
weather had not abated and the master
judged it unsafe to try and make Palm
Passage, as this meant altering course to
bring the wind on the port beam. He
decided to maintain the course with the
wind astern. Fortunately the course of
295o took the ship directly towards Grafton Passage. Even with reduced
engine revolutions, Padang Hawk made
good speed. In the early hours of 28 July 1999,
the ship was approaching Grafton passage
and, by 04:00, it was safely in the calmer
waters inside the Great Barrier Reef.
In the afternoon of 28 July, Padang Hawk
anchored off Townsville and final adjustments
were made to the ballast to minimise
the list and reduce the ship’s
draught. The anchor was weighed at 1737
and the pilot boarded at 18:20. The ship
arrived safely alongside in Townsville at
19:28 on 28 July.
Comment and Analysis
When Padang Hawk arrived alongside at
Townsville in the evening of 28 July 1999,
investigators inspected the ship’s cargo
holds. Cargo in holds 1, 2, 3 and 4 had
settled and shifted. In each hold, the
surface of the ore showed that a portion of
the ore had apparently ‘liquefied’ into a
glutinous thick slurry. In number 1 hold,
water was pooled on the surface of the ore
and the whole cargo in this hold had
settled to be almost level. The inner sides
of the hold showed the cargo still
‘hanging’ to port, about 5.5 m below the
deck level, and there was evidence of significant
‘mud’ splash (figs. 6, 7, and 8).
The cargo in holds 2, 3, and 4 showed
varying amounts of liquefaction with a
central mound of unaffected cargo surrounded
by cargo that had liquefied.
In number 5 hold, the cargo retained the
form in which it was loaded, with cargo
forming a flattened pyramid which
reached to the level of the bottom of the
topside hopper tank, 3.5 m below the deck
level. The disposition of the cargo in
number 5 indicated the way in which the
cargo had been trimmed and what the
cargo must have looked like in holds 1, 2,
3, and 4 after the completion of loading.
Test ‘grabs’ were taken from number 1
hold on the morning of 29 July 1999, using the
shore-based discharge crane. The cargo
lifted in the test grabs remained in a bulk
solid form, with some water or slurry
running from the surface when lifted from the hold. The ‘holes’ left in the surface of
the cargo after each grab was removed,
maintained their approximate size and
shape without excessive ‘slump’ in the surrounding
The hatch covers aboard Padang Hawk are
hydraulically operated steel covers, with
two sections folding and opening forward
and two sections folding and opening at
the after end of the hatch. The hatch seal
consists of neoprene rubber packing. Locking dogs fixed at intervals around
their periphery ensure that the hatch
covers are watertight.
Padang Hawk presented as a well-maintained
ship with hydraulic deck equipment
in good order. Examination of the hatch
covers, coamings and other openings into
the cargo holds, showed no obvious sign
of any ingress of water. The neoprene
packing on the hatch covers was in good
condition and showed that it had sealed
against the coaming channel bar. Inside
the coamings there was no obvious sign of
any ingress of water, although some water
was lying in the trackways associated with
the hatch coamings.
The state of the cargo in the forward four
holds was caused by excessive moisture in
the nickel ore and indicated two possibilities:
either seawater had gained access to
the holds in the rough weather, or the
cargo had been loaded in an excessively
If the moisture present in the cargo had
been due to seawater ingress through
poorly secured or failed hatch covers, it
would have been ‘salty’. Conversely, if
the cargo had been loaded in an excessively
moist condition, the origin of the water would have been rain in the mining and/or
stockpiling phases of the operation and
would consequently have been ‘fresh’.
Investigators took samples of the nickel ore from just beneath the top layer and
between 20–30 cm below the cargo
surface in number 1 and number 5 holds.
The ore was a red sand or dust with larger
pieces of solid greenish rock interspersed
throughout. These larger pieces were generally
less than 5 mm in size.
The samples were sealed in tins and delivered
to SGS Australia Ltd, at Port Kembla
for analysis to determine:
To ascertain whether the cargo had been
contaminated by seawater, SGS used two
different tests; the Mohr’s Method
Chlorine test and the High Temperature
Chlorine test. Both tests showed conclusively
that the water within the holds was
Tests of the actual moisture contained in
the samples resulted as follows:
- the surface sample from number 1 hold, 41 %;
- the sub-surface sample number one hold, 36.5 %;
- the sub-surface sample number five hold, 38.9 %.
To obtain the flow moisture point of the
nickel ore sample, SGS used the ‘Flow Table’ method described in ‘appendix D’
of the BC Code and then derived the value
for TML. This resulted in a TML of 29.2 %. All of the ore samples represented had
moisture contents that significantly
exceeded the TML determined using the
IMO standard flow table test.
Nickel ore has not been considered to be
prone to liquefaction. This cargo is regularly
carried with total moisture contents
in excess of 36%. On this occasion,
however, the cargo in Padang Hawk’s 1, 2,
3 and 4 holds had every outward appearance
of having suffered ‘liquefaction’
during the voyage.
in granular cargoes that are loaded with
excessive moisture and subjected to energy
from ship motions. There are any number
of scientific definitions of liquefaction.
The 1997 annual of the American Society
for Testing and Materials defines ‘spontaneous’
- …the sudden large decrease of the shearing resistance of a cohesionless soil. It is caused by the collapse of a structure by shock or other type of strain and is associated with a sudden but temporary increase of the prefluid pressure. It involves a temporary transformation of the material into a fluid mass.
In excess of 90 % by weight of the ore
loaded by Padang Hawk had a particle size of less than 1 mm, 82.5 % of the cargo
had a particle size of less than 0.053 mm.
This cargo was typical of the limonitic
nickel ores being mined in New
Caledonia. The small relative particle size
and chemical properties of the mineral
mean the amount of moisture in these
nickel ore cargoes can be large without an
appreciable change in the appearance or
static handling properties. Limonitic
nickel ores adsorb any free intergranular
water into the mineral structure over a
period of time. Adsorption of any free
water continues until the ore is ‘saturated’
and unable to take up any more water.
Handling problems may occur when saturated
ore is subject to vibration or stress,
or if there is a significant amount of unadsorbed
intergranular free water.
At some time during voyage number 904,
despite the fact that the crew pumped the
hold bilges regularly and effectively on 24,
25 and 26 July, a portion of [[Padang
Hawk]]’s nickel ore cargo liquefied and
moved to port causing the vessel to list.
After listing to port on the evening of 26
July, the crew inspected the cargo holds
and observed the cargo flowing with the
movement of the ship. On arrival in
Townsville the cargo in the forward four
holds displayed clear evidence of liquefaction
in the fluid form of the cargo and the
free water present on the surface of the
cargo in number 1 hold. The varying
degree of liquefaction of the cargo, with
the forward holds being the most affected,
may be explained by the motion of the
ship in the rough sea. Padang Hawk was
pitching and rolling heavily on 25 and 26
July. All of the cargo would have been
similarly effected by the rolling. However,
the amplitude of the pitching, and thus its
effect on the cargo, would have been
greater at the forward holds. The cargo in number 1 hold would also have been the
most effected by any ‘pounding’ and this
probably accounts for the particularly poor
state of the cargo in this hold.
By the time the test ‘grabs’ were taken
from number 1 hold on the morning of 29
July, sufficient free water had been readsorbed
by the nickel ore for the cargo to
return to a solid state.
The shipment of the limonitic nickel ore
from New Caledonia to Townsville is
subject to a detailed agreement between
the cargo sellers (Nickel Mining
Corporation) and Queensland Nickel Pty
Ltd (QNPL). The agreement specifies the
minimum characteristics of the ore and the
conditions under which it should be
shipped. This agreement includes provision
- an agreed maximum moisture content (free water) of 35 %, with a lower refer ence price for ore with a moisture content in excess 36 % and, conversely, a higher reference price for ore with a moisture content less than 34 %;
- a particle size not to exceed 200 mm;
- flow tests prior to loading to demonstrate to the satisfaction of the buyer and the ship’s master that the shipment will not flow; and
- a statement by the seller acknowledging the master’s right to refuse to load the cargo based on the results of the flow tests.
With regard to the flow tests, the agreement requires that:
- Ten representative samples from the stockpile to be loaded aboard the ship are to be tested no later than seven (7) days prior to the scheduled arrival of the ship.
- All results of flow tests should be recorded, conveyed and delivered to:
- The Ship’s Master (before the commencement of loading):
- Seller, and
The master received details of voyage
number 904 from the shipowner’s Brisbane
representative. For information on the
cargo and loading, the master was referred
to the detailed instructions provided for
voyage number 903. This telex included
standard details of the cargo, loading and
discharge ports, agents, and advice relating
to demurrage. It did not contain any
specific details of the moisture limits,
density, or other cargo characteristics. Nor
did it contain any direction pertaining to
the acceptability of the cargo.
The master was not provided with the
results of the flow tests or the moisture content of the nickel ore prior to loading
the cargo on voyage number 904. There is
some doubt that the master knew that this
information had to be provided under the
terms of the agreement and that he had the
right to refuse the cargo based on the
results of the flow tests. By failing to
provide the master with this information,
however, the cargo shippers were not only
in breach of the agreement but also the
provisions of the International Convention
for the Safety of Life at Sea (SOLAS).
On 27 July, the day after the incident, the
shippers did send the ship a facsimile with
a copy of the ‘Moisture Certificate’ certifying
that the ore loaded had a maximum
free moisture of 37 %. A second document
detailed the results of a series of 10
flow tests carried out between 11 July and
16 July. The results are shown in table 1:
Table 1: Flow test results, New Caledonia.
| Sample No.
|| Date of test
|| Deformation (mm)
These tests showed sample ‘deformations’
(the degree to which the cargo ‘flowed’ in
the test) of 1.7–2.3 mm. All of the
samples indicated that the cargo loaded
aboard Padang Hawk in Kouaoua on
voyage number 904, was fit for carriage
using the QNPL criteria which stipulates a
maximum acceptable deformation of 3
According to information obtained independently
on behalf of the Inspector of
Marine Accidents by the French Marine
Casualties Investigation Board, the moisture content of the ore was 37.4 % which
agrees reasonably well with the information
provided to the master on the
‘Moisture Certificate’. QNPL also provided the investigation with a chemical analysis
of the nickel ore cargo shipped by
Padang Hawk on voyage number 904,
which indicated that the average moisture content was 36.55 %.
The QNPL agreement with the seller stipulates
that 10 ‘representative samples’
must be tested ‘no later than seven (7)
days prior to the scheduled arrival of the
vessel’. The wording of this portion of the
agreement is somewhat ambiguous. It can
be read to mean that the cargo should be
tested at least 7 days before it is to be
loaded when in fact the final testing
should take place just prior to the time of
In the case of Padang Hawk’s voyage
number 904, according to the flow test
records supplied by the shipper after the
incident (shown in table 1), 10 tests were
in fact performed in the week prior to the
ship’s arrival at Kouaoua on 17 July 1999. The
last tests were conducted the day before on
16 July 1999. Given the subsequent liquefaction
of the cargo, the results of these flow tests
would indicate that either; the flow test
procedure is flawed in some way, or that
the samples tested were not representative
of the cargo as a whole.
QNPL provided information as to how the
samples are collected from the ore stockpiles:
- The method by which the samples are taken will vary according to the type and size of the ore stockpile. The supplier is required to utilise his expertise to obtain a representative sample from the stockpile. Typically, samples are taken from the stockpile at a depth which will ensure that the ore has not been affected by the prevailing either wet or dry climatic conditions and is representative of the material to be loaded. This is normally done by a small backhoe and depth of sample is approximately 0.5 to 1.0 metre.
Rainfall records for Kouaoua for July
1999 from the Meteorological Office of
New Caledonia showed that in the first
half of the month of July, Kouaoua had
received 171 mm of rain, 105 mm of
which was recorded on 14 July, three days
before Padang Hawk arrived. At the
Kouaoua nickel mine and ship-loading
facility, the stockpiles of ore are stored in
the open. The cargo intended for Padang Hawk would have been fully exposed to
the rain. The flow tests conducted on 14,
15, and 16 July showed sample deformations
of between 1.8 and 2.3 mm and thus
no significant increase as a result of the
heavy rain on 14 July. Nevertheless, the
nickel ore loaded aboard Padang Hawk on
voyage number 904 was saturated to the
point where free water was observed
running from the cargo as it was loaded.
The cargo was not fit for carriage in spite
of the fact that the records of the sample
tests conducted in the week prior to
loading failed to indicate any abnormality
with the nickel ore.
The standard IMO flow moisture point test
is described in appendix D of the [[BC
Code]]. Part of the test requires that a representative
sample of test material is
placed in a standard ‘mould’ and compacted
in a prescribed fashion with a standard
‘tamper’. The sample, now in the form of
a truncated cone, is then turned out of the
mould onto a standard ‘flow table’ and the
table is raised and ‘dropped’ 50 times,
from a height of 12.5 mm, at the rate of 25
times per minute. If the sample shows
‘plastic deformation’ after this process, it
indicates that the sample has reached a flow state. If the sample does not show
plastic deformation, it is placed in a
mixing bowl and a small amount of water
is added. It is then returned to the mould,
tamped, and retested on the flow table.
The whole process is repeated until the
sample shows plastic deformation indicating
that a flow state has been reached.
The IMO procedure requires that the moisture content of a sample just above the flow point and another just below the flow point are to be ascertained using a standardised
drying procedure. An average of
these values forms the flow moisture point
of the ore. The TML is then calculated
and is 90 % of the flow moisture point
expressed as a percentage of water by
The agreement between QNPL and the
seller states that the standard IMO flow moisture point test procedure is not suitable
for limonitic ores. As a result, QNPL have adapted the standard IMO flow moisture point test to form the ‘flow test’ procedure
detailed in their agreement with the seller.
The equipment used, the sample preparation,
and the actual methodology of the
QNPL ‘flow test’ are almost the same as
those described in the BC Code for the
flow moisture point test. The main difference
between the two tests is that the simplified
QNPL test requires no addition of
water. QNPL explained the reasons why
the adaptation of the IMO procedure was
necessary and these are detailed in the below section titled "The adapted flow test procedure".
The QNPL-adapted flow test only prescribes
a maximum allowable sample
deformation of 3 mm and does not stipulate
that the actual flow moisture point or
the transportable moisture limit must be
According to the flow moisture point test
in the BC Code, ‘plastic deformation’ of
the sample indicates that a flow state has
been reached. The Code does not indicate
an ‘acceptable’ level of deformation. By
the definition adopted in the BC Code, all
of the samples tested prior to loading the
Padang Hawk’s voyage number 904 cargo
had reached a ‘flow state’.
The Japanese Experience
Around 4 million tonnes of saprolitic
nickel ore is shipped to smelters in Japan
each year. There have been a number of
reported instances where this cargo has
‘shifted’, as a result of excessive water content, while being carried from mines in
the Philippines, Indonesia and New
Caledonia to Japan. After researching
marine casualty databases, the ATSB
found there had been a recent incident
where a ship was lost while carrying
nickel ore to Japan.
In August 1998, the Panama flag ship Sea Prospect foundered with the loss of ten
seafarers from a crew of 21. The ship had
a full cargo of nickel ore loaded in
Indonesia and was en route to Hiroshima
in Japan. The ship broadcast an SOS
signal in a 2 m sea with wind speeds of
less than 20 knots. There is no information
as to whether the loss of the ship
could be attributed to the shift of cargo,
the deformation of cargo, or to high moisture
The Japanese authorities have been concerned
for some time about the propensity
of nickel ore cargoes to shift, and the
Journal of the Society of Naval Architects
of Japan (vol 187, June 2000) contains a
Study on Prevention of Sliding Failure of
Nickel Ore in Bulk. The study details a
new procedure for evaluating the [[shear
strength]] of nickel ore and thus the suitability
for carriage of the cargo. The test procedure
utilises a ‘cone penetrometer’ to
measure the shear strength of a graded
sample of nickel ore suitably compacted in
a standard container. Advice from
Professor Tamaki Ura of the University of
Tokyo, one of the authors of the nickel ore
study, is that when the moisture content of
nickel ore is higher than a critical value, it
loses shear strength. The Japanese study
refers only to nickel ore and does not differentiate
between limonitic and saprolitic
In submission QNPL reiterated:
- QNPL utilises ore from the limonite zone, while the Japanese and New Caledonian smelters utilise saprolite ore, which exhibits different handling characteristics due to its differing mineralogy and particle size distribution. Consequently the comments from Professor Tamaki Ura may not be applicable to limonite, as they almost certainly are related to saprolite.
The accepted practice on bulk cargo ships
is to calculate the vessel’s stability prior to
departing both loading and discharge
ports. Stability calculations are performed
using: data relating to the vessel’s draft;
the quantity and location of known masses
including, ballast, fuel, fresh water, etc;
and the vessel’s stability curves and tables,
(usually in tabulated format and often
computer based). These calculations are
performed, usually by the mate, to ensure
the vessel has adequate stability for the
planned passage and any contingencies
that might be encountered en route. On
Padang Hawk, this was not an onerous
task as the ship was equipped with a
When Padang Hawk completed loading
the cargo of nickel ore at Kouaoua on
24 July 1999, no stability calculations were
undertaken prior to the vessel departing
the port. The master knew from previous
experience with the cargo that the vessel
had a surplus of stability after loading.
Once the cargo had become fluid, and
Padang Hawk had developed the 15o list to
port, the master’s initial response was to
pump ballast into 3 and 5 starboard
topside tanks. No stability calculations
were undertaken prior to this ballasting
operation to ensure that the vessel would
remain stable. Once again, the master
relied on his experience and judgement in
correcting the vessel’s list without using
the hard facts available from the ship’s
The owners of the vessel were consulted
once the list had been corrected using the
two topside tanks. Their advice was to
transfer the ballast from the topside tanks
to the double bottom ballast tanks. The
owners expressed concern that the ballast
in the topside tanks compromised the
vessel’s stability. The ballast was subsequently
transferred in accordance with the
directions of the owners. The most critical
times during these operations were the
‘transient’ conditions when the topside and
double bottom tanks were being emptied
or filled with a consequent ‘free surface’.
The vessel’s stability was not calculated
for any of these operations.
The relevant stability data for Padang Hawk was obtained for the purpose of the
investigation. The vessel’s stability was
calculated independently for the purposes
of the report using the departure data from
Kouaoua, for an initial condition, and the
subsequent conditions of the starboard
topside tanks ballasted, and the double
bottom tanks ballasted. The calculations
showed that the vessel exceeded the intact
stability criteria recommended in the
‘Code of Intact Stability for all Types of
Ships Covered by IMO Instruments
(Resolution A.749 (18))’. In using the
topside tanks on this occasion the ship was
not in fact put at risk through the possible
loss of intact stability. The topside tanks
do have a higher centre of gravity than the
double bottoms, but have much smaller
‘free surface’ and bigger righting effects.
While recognising the circumstances and
the imperative to right the ship’s list, the
master took a significant risk in ballasting
the vessel, by adding weight centred high
and outboard with an accompanying free
surface, without first checking the likely
effect on the vessel’s stability. Although
the master was correct in his assessment of
the stability, there was a risk of far worse
consequences for the vessel and crew,
should his intuitive judgement have been
faulty. It would have been prudent to use
the available resources to calculate the stability
of the vessel for all of the conditions
prior to transferring any ballast.
These conclusions identify the different
factors contributing to the incident and
should not be read as apportioning blame
or liability to any particular organisation
The factors contributing to the shift of
Padang Hawk’s nickel ore cargo and the
consequent port list include, but are not
- The cargo was loaded with excessive moisture content.
- The vessel was subjected to heavy seas, which led to the cargo changing state from a solid to a viscous liquid in 4 of the 5 holds.
- Insufficient knowledge of the characteristics of nickel ore as a cargo and its propensity to become fluid when the moisture content is high and it is subjected to sufficient physical stress.
- There is no test to specifically ascertain the ‘transportable moisture limit’ of nickel ore.
- The owners/agent of the vessel did not include in the master’s voyage instructions the relevant information pertaining to the cargo moisture content, flow tests, and the master’s right to refuse to load the cargo under the terms of the agreement between QNPL and the cargo sellers.
- The ore seller did not provide the master with the agreed data pertaining to the cargo’s moisture content and flow tests as required by SOLAS.
- The master loaded the nickel ore without insisting on the provision of the data concerning the moisture content and flow tests.
- The mined nickel ore was stockpiled in areas open to the ingress of rainwater.
- The agreement between QNPL and the seller did not stipulate a reasonable, maximum, acceptable moisture content, based on the nickel ore’s ability to be carried safely by sea.
- The vessel’s stability should have been calculated for the loaded condition leaving Kouaoua and subsequently checked prior to the pumping of ballast into the topside and double bottom tanks to correct the list.
Granular materials have void spaces
between the particles caused by the irregular
shape of the particles. These void
spaces may be filled with air, water or a
combination of both. When a cargo containing
moisture is subjected to energy
such as ship motions, the cargo particles
move to compress the void spaces and
pressurise any free water present in the
spaces (pore water pressure). In addition,
moisture may be released from the mineral
structure of some types of cargo when
subjected to ship’s motions. This release
of adsorbed water increases the amount of
free water in the cargo and leads to a
further increase in the pore water pressure.
If the pore water pressure becomes high
enough, it overcomes the friction forces
binding the individual particles of material
and the shear strength of the cargo falls to
the point where liquefaction occurs. The
cargo becomes a viscous fluid with the
ability to flow.
The BC Code provides guidance to administrations,
shipowners, shippers and
masters on the standards to be applied in
the safe stowage and shipment of [[solid
bulk cargoes]], excluding grain. There is a
specific section on cargoes liable to liquefaction
and an appendix,
which contains a list of such cargoes.
Nickel ore is not contained in the appendix.
The International Convention for the Safety of Life at Sea, regulation 2, part A, chapter VI, ‘Cargo Information’ states:
- The shipper shall provide the master or his representative with appropriate information on the cargo sufficiently in advance of loading to enable the precautions which may be necessary for proper stowage and safe carriage of the cargo to be put into effect. Such information shall be confirmed in writing and by appropriate shipping documents prior to loading the cargo on the ship.
And further: The cargo information shall include:
The Adapted Flow Test Procedure
The flow test procedure used to test the
nickel ore carried by Padang Hawk on
voyage number 904 is outlined in the
agreement between the cargo seller and
QNPL. The flow test is adapted from the
BC Code procedure for ascertaining flow moisture point and, like the Code, it identifies that:
- …a flow state is considered to have been reached when the moisture content and compaction of the sample produces a level of saturation such that plastic deformation occurs. At this stage, the moulded sides of the sample may deform, giving a convex or concave profile.
The agreement goes on to set a limit on
the ‘acceptable’ amount of sample deformation:
- Under plastic deformation, if the increase in the diameter of the moulded sample measured at any part of the cone exceeds 3 mm, the cargo which it represents is considered unsuitable for shipment.
QNPL provided the following explanation
as to why the BC Code procedure is not
suitable for testing limonitic ores:
- The IMO Test was developed for concentrates which have no specific structure and involves mixing of water with the material. In the case of limonitic nickel ore, this test changes the structure of the macro particles and the test material becomes a different material to the product being transported, therefore it is not suitable for use in testing the suitability for transport of limonitic nickel ore.
Specifically relating to the ore structure,
QNPL said that:
- …the sample preparation of limonite nickel ore for the flow moisture test, and the act of adding water to this sample, increases the amount of free water present as opposed to adsorbed or absorbed water. There are two main reasons for this:
- Firstly most of the water in an undisturbed piece of limonite is adsorbed onto the very high surface area possessed by the very fine grained (to almost amorphous) goethite dominated mineralogy. This is why undisturbed pieces of limonite containing >40% moisture can appear dry. Water entering a piece of limonite will probably take much more time than a flow moisture test would allow to change from being intergranular free water to becoming water adsorbed onto the goethite minerals. Unlike adsorbed water, free water moves amongst the pieces of limonite and lubricates them allowing them to move freely, leading to slumping or collapse.
- Secondly and perhaps most importantly, the above effect is compounded when:
- preparation of the sample for the flow moisture test disturbs the material. This disturbance (which is greater than any mining and loading operation does to ore) leads to compaction or slicking of limonite pieces (1mm-10cm range), thus reducing the permeability of the surface of these pieces,
- then added water cannot be absorbed into the pieces and runs or slurries as free water amongst the surfaces of the grains.
- The stability coefficient of a limonite sample is probably more dependent on the amount of free water than on the amount of adsorbed water, so for example:
- sample A with 40% absorbed water and 0% free water is much more stable than:
- sample B with 30% absorbed water and 10% free water.
- All of this is independent of the effect of liquefaction caused when adsorbed or absorbed water is released from near saturated limonite by vibration.
In 1986, QNPL commissioned a study of the behaviour of limonitic nickel ore during shipping. Gutteridge Haskins & Davey and Chalmers University, Gothenburg, carried out tests specifically related to the likely behaviour of nickel ore to evaluate ship unloaders. The investigations were related to the determination of the shear strength of nickel ore, density and stability of ships cargoes under the conditions encountered at sea. A further report by Gutteridge Haskins & Davey in 1990 titled Gag Island Nickel Laterite Deposit Report on Ship Stability, Trial Shipments V3/90 and V4/90 concluded in part that ‘no significant strength changes have been observed within Gag Island limonite or saprolite as a result of shipment’. These reports form the basis of QNPL’s third-party verification of their adapted flow test.
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Australian Transport Safety Bureau, Report #148, "Investigation into the shift of cargo on board the Singapore flag bulk carrier Padang Hawk in the Coral Sea on 26 and 27 July 1999", September 2000. (Download PDF)
- ↑ 2.0 2.1 International Maritime Organisation, International Maritime Solid Bulk Cargoes Code, 2013 Edition, London: International Maritime Organization.
Sources of Information
- The master and crew of Padang Hawk
- Queensland Nickel Pty Ltd
- Australian Maritime Safety Authority
- LLP Ltd, Information Service Department
- International Transport Workers Federation
- Nippon Kaiji Kyokai Survey Department
- Meteorological Office of New Caledonia
- SGS Australia Pty Ltd
- Professor Tamaki Ura, University of Tokyo
- Marine Casualties Investigation Board, France
- Queensland Department of Mines and Energy
Portion of chart Aus 4060 reproduced with permission of the Hydrographic Office, RAN.