7.1 Tanks for the purposes mentioned above should
be arranged to satisfy the intended service of the ship.
7.2 Oil residue (sludge) tanks may be separate
and independent but may also be combined, as suitable, depending on
the size and the service of the ship.
7.3 The merits of arranging an independent tank
for the collection of separated sludge should be considered, having
regard to the smaller tank volume that needs to have cleaning and
heating arrangements and the reduced space requirement for tank capacity
that should preferably be arranged above the tank top.
7.4 If an oily bilge water holding tank is arranged,
it should be separate and independent from other tanks for the collection
of oil residue (sludge).
7.5 Ships operating with heavy fuel oil of a relative
density greater than 0.94 at 15°C should be provided with an oily
bilge water holding tank of adequate capacity and fitted with heating
facilities to preheat the oily mixture prior to the discharge of the
tank's contents into the sea through the 15 ppm bilge separator.