1 Damage stability requirements for passenger
ships are set forth in regulation
II-1/8 of the International Convention for the Safety of Life
at Sea, 1974, as amended. The 1989 amendment to this regulation requires
specific stability characteristics at angles of heel beyond the angle
of equilibrium. For the purpose of calculating the required righting
arms, it is necessary to establish flooding boundaries above the bulkhead
deck.
2 Regulation II-1/20 addresses watertight integrity
above the margin line, which is effectively equivalent to the bulkhead
deck. Although paragraph 1 addresses the spread of water above the
bulkhead deck, it is insufficient to establish boundaries for calculation
purposes. For the purpose of establishing boundaries to satisfy the
residual stability requirements of regulation
II-1/8, enclosed spaces included in the damage stability calculations
may have weathertight subdivision if they do not become submerged
during any stage of flooding, otherwise the subdivision should be
watertight. This procedure extends the principle of a weathertight
envelope, put forward in paragraph 2, for boundaries which are intermittently
submerged.
3 A primary concern with the integrity of boundaries
above the bulkhead deck is the design and control of doors. Modern
passenger ships often have doors in main vertical zone bulkheads and
other bulkheads that are routinely used. Compliance with regulation II-1/8 necessitates that
such doors be power operated and remotely controlled sliding watertight
doors. Watertight doors installed in the spaces included in the damage
stability calculations should meet the requirements of regulation
II-1/15 (now II-1/13) for
power operated sliding watertight doors, except that the scantlings
and sealing requirements could be reduced to the maximum head of water
for their location.
4 The use of watertight sliding doors above the
bulkhead deck affects the escape provisions of regulation II-2/28. When such doors are used above the bulkhead
deck, there should be at least two means of escape from each main
vertical zone or similarly restricted space or group of spaces, at
least one of which should be independent of watertight doors and at
least one of which should give access to a stairway forming a vertical
escape. Sliding doors that will be used frequently by passengers must
not create a tripping hazard.
5 Doors fitted above the bulkhead deck which are
required to meet both fire-protection and watertight requirements
shall comply with the fire requirements in regulation
II-2/30 and the watertight requirements in 3 above. Notwithstanding
the ultimate sentence of regulation II-2/30.2,
watertight doors fitted above the bulkhead deck should be insulated
to the standard required by table 26.1 and regulation
II-2/24.1.1. The door must be capable of operation using both
the remote fire door control circuit and the remote watertight door
control circuit. If two doors are fitted, they must be capable of
independent operation. The operation of either door separately must
not preclude closing of the other door. Both doors must be capable
of being operated from either side of the bulkhead.