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April
10, 2001
Following
an exhaustive inspection and analysis of the damaged product tanker
Castor, the Cyprus Department of Merchant Shipping and ABS
have jointly announced preliminary findings that point to hyper-accelerated
corrosion as the probable principal cause behind the structural
failure.
"The
Castor has become a floating laboratory which is providing
us with some surprising findings," said ABS Chairman and CEO Frank
J. Iarossi in announcing the preliminary results of the investigation.
"If these initial conclusions hold up, there will be significant
implications for class and possibly wider implications for the manner
in which the new generation of double hulled tankers should be constructed
and maintained."
A
formal report into the casualty will not be issued by the Cypriot
authorities and by ABS until the conclusion of detailed laboratory
testing of steel samples cut from the damaged section of the tanker.
"It will take some time to scientifically verify that our interpretation
of events is correct," said Iarossi.
"The
Castor represents an unprecedented level of cooperation between
the class society and the Flag State involved in a casualty," said
Captain Andreas Constantinou, Senior Marine Surveyor for the Cyprus
Department of Merchant Shipping. "The relationship that developed
during the nearly six week effort to save the vessel and its cargo
has been continued through the investigative phase. In my experience,
never before has class and the Flag State worked so closely to understand
the causes of a casualty and to develop necessary changes in the
regulatory requirements."
The
600 tons of steel, primarily in the deck plating and underdeck longitudinals,
that was renewed on the Castor at Special Survey in late
1997 has provided the key to understanding what transpired in the
interim.
"Although
further testing is still being undertaken, our gaugings indicate
that sections of this steel have already wasted by as much as 30
percent," said Iarossi. "This indicates an annual corrosion rate
of as much as 1.5mm compared to normal rates of about 0.1mm or less."
The
critical element, according to the preliminary findings, is the
presence, and absence of coatings. "The original steel had been
coated," explained ABS Chief Surveyor Gus Bourneuf. "This coating
had begun to break down with age. At the fourth special survey,
the new steel was not coated. There were no sacrificial anodes in
the tanks so the uncoated steel in the underdeck area acted as the
anode with the partially corroded, original steel providing the
principal point of attack."
According
to an independent corrosion expert, brought in by ABS to analyze
the condition of the ship, three other elements are considered likely
to have contributed to the rapid deterioration. The vessel had been
engaged in the gasoline trades, the most corrosive of all oil products.
The critical Number 4 tanks were used for ballast purposes, introducing
salt water into the chemical equation. And the vessel had been trading
into hot areas, such as West Africa, greatly raising the ambient
temperatures in the ullage spaces and creating a fertile environment
for the corrosive action.
"Given
the scantlings applicable to this size of ship, the loss of nearly
5mm of the new steel in just over three years of trading represents
a very high percentage loss of section," said Bourneuf. "The loss
of section of the uncoated steel that was not replaced was clearly
greater. It is reasonable to conclude that this loss of strength
in this critical area of the vessel may have contributed to the
buckling, and subsequent cracking of the deck plating in the severe
weather conditions encountered on passage."
Iarossi
stressed that the focus of the on-going investigation will be on
necessary remedial steps that need to be taken by ABS, recommended
to IACS and, if necessary, proposed at IMO. "Once we have definitive
conclusions to the investigations, Cyprus will raise the need for
any changes in IMO requirements at the governmental level," Constantinou
confirmed.
Some
of the questions ABS and Cyprus are investigating are:
- Is there
a need to change survey requirements governing the gauging of
tankers to include additional girth bands, particularly in the
forepart of the tanks, wider girth bands and greater density of
readings per plate or structural member?
- To what extent
should detailed requirements for coatings be incorporated into
class requirements?
- Should the
survey requirements for Intermediate, and possibly Annual surveys
of certain vessel types after a specified age be substantially
upgraded to include additional close up inspection of critical
areas within the hull.
- What are
the implications of these findings relative to the ballast spaces
of double hulled tankers, particularly as they begin to suffer
coating breakdown?
"As
more information is obtained from the on-going metallurgical and
corrosion studies, we will develop and distribute to our colleagues
in IACS and to the industry our specific recommendations for changes
to Rule requirements," said Iarossi.
"It
must be remembered that the Castor had met all class requirements
when the major steel replacement was completed, and had remained
in class with no outstandings" he added. "We have always felt that
the Rules are sufficiently conservative for any operational environment.
Although it must be emphasized that the Castor was structurally
sound, it did not sink, it did not lose any cargo or cause any pollution,
and no one was injured or lost their life, if there are shortcomings
in the requirements we need to rectify that, and do so quickly."
Background:
The Castor suffered heavy weather damage while on passage
from Romania to Nigeria on December 30, 2000. It was denied a sheltered
area to tranship the cargo of 29,500 tons of unleaded gasoline by
seven coastal states in the Mediterranean area. The vessel was towed
over 1000 miles, through repeated storms while in a damaged condition
until a successful salvage of the cargo was completed at sea some
39 days later. The vessel is currently undergoing inspection and
repair in Piraeus.
The
Vessel: The «CASTOR», IMO No. 7423641, is a steel single hull
product carrier vessel with a gross tonnage of 18,565 and a deadweight
of 31,068 metric tons, built at the Busan shipyard of the Korea
Shipbuilding & Engineering Corporation. The vessel is equipped
with an Hitachi Zosen engine of 8653 KW giving a service speed of
15 knots. The vessel was registered in the Register of Cyprus Ships
on the 14 August 1985 and has flown the flag of the Republic of
Cyprus since that time.
ABS:
Founded in 1862, ABS is a leading international classification society
devoted to promoting the security of life, property and the marine
environment through the development and verification of standards
for the design, construction and operational maintenance of marine-related
facilities. For the last two years, ABS has been ranked by the United
States Coast Guard (USCG) as the best major classification society
for port state control performance. (www.eagle.org)
The
Republic of Cyprus: Responsibility for the development of maritime
activities lies with the Ministry of Communications and Works. Its
authority and jurisdiction are exercised through the Department
of Merchant Shipping. The Department's activities include, amongst
others, the control of shipping and enforcement of international
conventions and investigation of marine casualties. The Government
of the Republic of Cyprus systematically monitors the performance
of all Cyprus flag ships and in particular those considered to be
of a high risk.
The
actions taken during the monitoring process range from occasional
surveys, structural strength analysis, joint surveys with classification
societies, suspension and withdrawal of statutory certificates and,
when necessary, withdrawal of the Document of Compliance of the
ships operators. In addition, the work of classification societies,
that have been authorized to act on behalf of the Government of
the Republic of Cyprus, is closely monitored and corrective actions
are required whenever the circumstances so warrant. (www.shipping.gov.cy)
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