Page 271 - International safety guide for oil tankers and terminals

SPECIAL SHIP TYPES

Most dry bulk ports require a gas free certificate to be issued in respect
of a combination carrier presenting to load or discharge dry bulk cargo.
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Such certificates normally relate to holds and other spaces, but will not
confirm that pumps and pipelines are free from oil and/or hydrocarbon
gas.
If, however, slops cannot be discharged and have to remain on board, the์นาวี
14.1.10 Carriage of Slops when Trading as a Dry Bulk Carrier

Before a combination carrier is to be operated as a dry bulk carrier, every
effort should be made to ensure that any oil contained in the slop tanks is
discharged ashore. After discharging the slops, the empty tanks should
be cleaned and either gas freed or inerted prior to loading any dry bulk
งานห้องสมุด ศูนย์ฝกพาณิชย
cargo.

following precautions should be taken:

All slops must be collected in the slop tank specially designated for
this purpose.

Blanking plates or other approved means of closure must be fitted in
all pipelines, including common vent lines leading to or from the slop
tank, to ensure that the contents and atmosphere of the slop tank are
isolated from other compartments.
The slop tank should be purged with inert gas and a positive pressure
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maintained within the tank at all times.
Carbon dioxide must never be used in liquid form to provide inert gas
to the ullage space of the dirty slop tank because of the risk of
generating an electrostatic charge.
Unless the tank is fully inerted, the slops should be handled in such a
way as to avoid a free fall of slops into the receiving tank, as this may
cause a build-up of an electrostatic charge.

Unless the ship reverts to carrying oil, oil slops should not be retained on
board for more than one voyage. If, however, it is impossible to remove
the slops because of a lack of shore reception facilities for oily residues,
the slop tank should be treated as indicated above and appropriate
reports forwarded to the Company and the relevant administration.

14.1.11 Leakage into Ballast Tanks on Combination Carriers
A serious problem occurs if there is leakage of oil from the cargo holds
into the ballast tanks.

On combination carriers, the known weak structural points are as follows:
On ships with vertically corrugated transverse bulkheads, cracks may
occur in the welded seams between these bulkheads and the upper
hopper tanks.
In double hulled ships, leaks may be found in the upper welded seams
of the longitudinal bulkhead between ballast tanks and cargo tanks
abutting the sloped deckhead of the cargo tank.

Due attention should be given to ensuring the integrity of these seams.

© ICS/OCIMF/IAPH 2006 237