4.10.1 Units should be provided with an efficient
pumping system capable of ballasting and deballasting any ballast
tank under normal operating and transit conditions. Alternatively,
Administrations may permit controlled gravity ballasting.
4.10.2 The ballast system should provide the capability
to bring the unit, while in an intact condition, from the maximum
normal operating draught to a severe storm draught, or to a greater
distance, as may be specified by the Administration, within three
hours.
4.10.3 The ballast system should be arranged to
provide at least two independent pumps so that the system remains
operational in the event of failure of any one such pump. The pumps
provided need not be dedicated ballast pumps, but should be readily
available for such use at all times.
4.10.4 The ballast system should be capable of
operating after the damage specified in paragraph 3.5.10 and have
the capability of restoring the unit to a level trim and safe draught
condition without taking on additional ballast, with any one pump
inoperable. The Administration may permit counter-flooding as an operational
procedure. Counter-flooding is not to be considered as a means to
improve the suction head available to the ballast pumps when considering
the operability of the ballast system after the damage specified in
paragraph 3.5.10.
4.10.5 The ballast system should be arranged and
operated so as to prevent inadvertent transfer of ballast water from
one tank or hull to another, which could result in moment shifts leading
to excessive angles of heel or trim.
4.10.6 It should be possible to supply each ballast
pump provided to meet paragraph 4.10.3 from the emergency source of
power. The arrangements should be such that the system is capable
of restoring the unit from an inclination specified in paragraph 4.1.4.1
to a level trim and safe draught condition after loss of any single
component in the power supply system.
4.10.7 All ballast pipes should be of steel or
other suitable material having properties acceptable to the Administration.
Special consideration should be given to the design of ballast lines
passing through ballast tanks, taking into account effects of corrosion
or other deterioration.
4.10.8 All valves and operating controls should
be clearly marked to identify the function they serve. Means should
be provided locally to indicate whether a valve is open or closed.
4.10.9 Air pipes should be provided on each ballast
tank sufficient in number and cross-sectional area to permit the efficient
operation of the ballast pumping system under the conditions referred
to in paragraphs 4.10.1 to 4.10.8. In order to allow deballasting
of the ballast tanks intended to be used to bring the unit back to
normal draught and to ensure no inclination after damage, air pipe
openings for these tanks should be above the worst damage waterline
specified in chapter 3. Such air pipes
should be positioned outside the extent of damage, as defined in chapter 3.