3.6.1 The number of openings in watertight subdivisions
should be kept to a minimum compatible with the design and safe operation
of the unit. Where penetrations of watertight decks and bulkheads
are necessary for access, piping, ventilation, electrical cables,
etc., arrangements should be made to maintain the watertight integrity
of the enclosed compartments.
3.6.2 Where valves are provided at watertight
boundaries to maintain watertight integrity, these valves should be
capable of being locally operated. Remote operation may be from a
pump-room or other normally manned space, a weather deck, or a deck
which is above the final waterline after flooding. In the case of
a column-stabilized unit this would be the central ballast control
station. Valve position indicators should be provided at the remote
control station.
3.6.3 Watertight doors should be designed to withstand
water pressure to a head up to the bulkhead deck or freeboard deck
respectively. A prototype pressure test should be conducted for each
type and size of door to be installed on the unit at a test pressure
corresponding to at least the head required for the intended location.
The prototype test should be carried out before the door is fitted.
The installation method and procedure for fitting the door on board
should correspond to that of the prototype test. When fitted on board,
each door should be checked for proper seating between the bulkhead,
the frame and the door. Large doors or hatches of a design and size
that would make pressure testing impracticable may be exempted from
the prototype pressure test, provided that it is demonstrated by calculations
that the doors or hatches maintain watertightness at the design pressure,
with a proper margin of resistance. After installation, every such
door, hatch or ramp should be tested by means of a hose test or equivalent.
3.6.4 For self-elevating units the ventilation
system valves required to maintain watertight integrity should be
kept closed when the unit is afloat. Necessary ventilation in this
case should be arranged by alternative approved methods.