Circular letter
MSC/Circ.1143
GUIDELINES ON EARLY ASSESSMENT OF HULL DAMAGE AND POSSIBLE NEED FOR ABANDONMENT
OF BULK CARRIERS
(adopted on 7 December 2004)
1.
The Maritime Safety Committee, at its seventy-sixth session (2 to 13 December
2002), considered recommendations for decision-making emanating from various
formal safety assessment (FSA) studies on bulk carrier safety. In particular,
the Committee agreed that a circular should be prepared addressing bulk
carriers which may not withstand flooding of any one cargo hold and containing
information on the action to be taken in case of flooding of such holds, making
sure that the professional judgment of the master is not undermined.
2.
The Committee, at its seventy-ninth session (1 — 10 December 2004), having
considered the recommendations made by the Sub-Committee on Ship Design and
Equipment at its forty-sixth session, the Sub-Committee on Safety of Navigation
at its forty-ninth session and the Sub-Committee on Standards of Training and
Watch keeping at its thirty-fifth session, approved Guidelines on Early
Assessment of Hull Damage and Possible Need for Abandonment of Bulk Carriers,
as set out in the Annex.
3.
Member Governments are invited to urge Companies, as de-fined in the ISM Code,
that operate bulk carriers flying their flag to issue ship specific guidance,
based on the annexed Guidelines, to the masters of such bulk carriers with a
view to improving the precautionary measures and procedures for emergencies on
board their ships.
Annex.
GUIDELINES ON EARLY ASSESSMENT OF HULL DAMAGE AND POSSIBLE NEED FOR ABANDONMENT
OF BULK CARRIERS
1.
Provoked by the disappearance and loss of a number of bulk carriers from mid
1970s onwards the international shipping community has grown increasingly
concerned that such ships are particularly vulnerable to rapid loss.
Consequently, IMO has been taking action over the years to address the problem
and find appropriate solutions. Among such actions, the Organization has
adopted amendments to the 1974 SOLAS Convention, by introducing chapter XII in
1997 (amended in 2002), and other related provisions in chapter II-1, and has
also amended the Guidelines on the enhanced programme of inspections during
surveys of bulk carriers and oil tankers (resolution A.744(18)) on several
occasions. More recently, a number of formal safety assessment (FSA) studies on
bulk carrier safety have been carried out. From these studies the Maritime
Safety Committee of IMO concluded at its 76th session in December 2002 that
bulk carriers do deserve continued special attention and a number of measures
were approved to address the issues identified, both structural and
operational.
2.
Records of bulk carrier losses indicated, in a large proportion of the cases
studied, that ship's masters often appeared to be unaware of the imminent
danger they were in. Many lost their lives together with the other seafarers on
board as a consequence. Ship losses were frequently so rapid that the ship did
not have time to send a distress signal.
3.
The records studied show that in the event of loss of hull integrity, in many
cases, bulk carriers should be evacuated as quickly as possible. Early
assessment of the situation is therefore imperative, combined with alerting a
maritime rescue coordination centre, alerting all personnel onboard and making
preparations for evacuation. This is of particular importance for single skin
bulk carriers which may not be capable of withstanding flooding of any cargo
hold.
4.
Operators should consider the following advice carefully with a view to
improving their own precautionary measures and procedures for emergencies. The
advice applies equally to ships other than bulk carriers when carrying dense
cargoes.
5.
In most cases in which bulk carriers have been lost, heavy cargoes such as iron
and other dense ores are a common factor. Ships are also vulnerable when
carrying certain break-bulk cargoes such as steel products. This could include
other ship types. The small volume taken up by the cargo in the ships» holds results
in a large unoccupied space. This provides potential in a flooding scenario for
large volumes of water to rapidly destroy the ship's residual buoyancy and, in
the case of smaller vessels, its stability. Larger vessels are also highly
susceptible to structural failure due to increases of weights caused by the
influx of water.
6.
Heavy cargoes place high loads on the structure, and structural failure is
therefore more probable when subjected to the additional forces associated with
flooding.
7.
Deterioration of structure through corrosion, fatigue and damage is identified
as a principal factor in the loss of many bulk carriers. Failing to identify
such deterioration may lead to sudden and unexpected failure. Bulk carrier
crews may be un-aware of the vulnerability of these vessel types. The
consequential loss of a ship carrying heavy cargo can be expected to be very
rapid, should a major failure occur.
8.
Spaces forward of the collision bulkhead will, in the event of flooding,
significantly affect the trim of the ship and reduce freeboard at the bow. In
extreme weather this further threatens the ship as green seas come inboard and
impact on hatch covers and other fittings that protect the water or weather
tight integrity of the ship. Shell plating in the region of the bow protects
the fore peak tank and other spaces as do air pipes and ventilators. If any of
them are damaged the ship's ability to resist further escalation of flooding is
compromised.
9.
Damage to side shell, externally through contact with docksides or tugs and,
internally from impact by cargo dislodging equipment during discharge, can
result in initiating fractures and/or fatigue of the structure. In single
side-skin bulk carriers, bulkheads, trunks and ballast tank boundaries, can
present "hard spots» that concentrate forces where the change in
construction occurs (e.g. longitudinal to transverse framing). This may lead to
undetected fractures.
10.
Internal degradation through corrosion may be accelerated through chemical
action from certain cargoes. Welds in particular may be subject to
"grooving» corrosion, in which the material forming the weld corrodes at a
faster rate than the plating to which it is attached. Fatigue failure may
result due to loss of cross-sectional area in the plating joints.
11.
In ballast holds, sloshing forces due to partially filled spaces (such as may
occur when changing ballast for environ-mental reasons) may result in damage to
the structure. This damage may go unnoticed if it is in inaccessible positions.
Sloshing is also a known cause of secondary damage after a space has become
flooded.
12.
Damage to bow plating such as is possible through impacts associated with
swinging or loosely stowed anchors may cause an initiating fracture or fatigue
in bow shell plating that could lead to failure and subsequent flooding.
Internal integrity of forward spaces (that are usually used for ballast and/or
stores) is therefore of vital importance. Corrosion degradation will seriously
reduce the ability of plating and stiffening to withstand the forces to which
it will be subjected. In larger ships, partially filled forepeak tanks may set
up destructive sloshing forces un-less the tank structure is designed for this.
13.
External forces — horizontal and/or vertical — may cause hatch cover
dislodgement. The cargo hatchway, if it loses its protection in this way, is a
major access for water ingress and a serious threat to the integrity of the
hull.
14.
When it occurs or is likely to occur, masters should quickly assess damage to
their ships by being alert to water ingress and its consequences. The following
guidelines are given to assist them in this assessment.
15.
If a ship takes on an unusual trim or heel, or if her motions become changed,
breach of the hull envelope should be suspected immediately:
- Unusual
collections of water on decks may be indicating trim or heel abnormality.
- Sudden changes
of heel or trim will indicate flooding or in smaller ships with lighter cargoes
it may indicate cargo shift.
— Jerky lateral
motions can be indicative of large scale sloshing as would be the case if a
hold were flooded.
— On smaller
ships, slowing of the ship's roll period may indicate excessive water within
the hull — a serious threat to stability. Ships fitted with GM meters should be
able to identify any unexpected changes in GM.
— Increases of
water boarding forward decks may indicate flooding of a forward compartment. Trim
and freeboard changes are notoriously difficult to assess from an after bridge.
16.
Methods of detection
— Hatch covers
may be dislodged by pressure and/or sloshing from within a hold if flooding
occurs through side shell or bulkhead.
— Sudden pressurisation
of compartments adjoining those that are damaged or flooded will indicate
failure of internal subdivision, most notably bulkheads.
— Spaces may be
monitored, either using gauging or bilge/ water level alarms. Forward store
spaces can also be monitored audibly using "talkback» telephones that may
be fitted in forward spaces. Anchor impacts and water in the space can be
detected using telephones of the type that remain active until switched off
from the bridge.
— Hull Stress
Monitors, where fitted, may be able to detect unexpected longitudinal hull
girder bending. Torsional stresses may also be detected through differential
changes between port and starboard strain gauges.
- Visual
monitoring from the bridge using binoculars, where fitted, by closed circuit
television, can give indication of abnormal water on deck and local damage.
How-ever, assessment of trim or freeboard using this method is difficult.
— Assessment of
trim changes can in certain conditions be detected by noting the level of the horizon,
when visible, against a known reference point on the foremast.
— Draught and
trim can be assessed using draught gauges. Changes are much more discernible
using this method than by visual means from above decks.
Early readiness for
evacuation
17.
In the event of identifying or even suspecting that the ship may have sustained
damage, ship's personnel should immediately be called to their emergency
stations. A high priority should be placed on preparing equipment for
evacuation. Abandonment should however only be invoked on the spoken orders of
the master following assessment of the risk.
18.
Contact with a Maritime Rescue Co-ordination Centre (MRCC)