6.1 When a deck is fitted with bulwarks such that shipped water may be trapped behind
them, the bulwarks should be provided with efficient freeing ports that will ensure the
deck can be effectively drained. This section is not intended to apply to inflatable
boats or boats fitted with a buoyant collar, as these requirements are dealt with in
other parts of the Code.
6.2 The area of freeing ports should be at least 4% of the bulwark area and be situated
in the lower third of the bulwark height, as close to the deck as practicable.
6.3 A vessel of less than 12 metres in length, having a well deck aft which is fitted
with bulwarks all round and which is intended to operate no more than 60 miles from a
safe haven (Area Categories 2, 3, 4, 5 and 6), should be provided with freeing ports
required by section 6.2 or may be provided with a minimum of two ports fitted (one port
and one starboard), which may be in the transom, each having a clear area of at least
225cm2 (0.0225m2). Ports may only be fitted in the transom on
vessels where under all foreseeable conditions water will drain.
6.4. Smaller ports may however be accepted in a vessel having only small side deck areas
in which water can be trapped, the reduced area being based on the volume of water which
is likely to become so trapped. The following correction to the required freeing port
area may be applied:-
-
FPREQ = FPMAX *( AACT / AMAX )
Where
FPREQ = Freeing port area required
FPMAX = Maximum freeing port area required
AACT = Actual area of deck fitted with enclosed bulwarks, excluding
superstructure or deckhouse area
AMAX = Area of maximum sized well (0.7L x B) where L and B are the
dimensions of the vessel
6.5 When a non-return shutter or flap is fitted to a freeing port it should have
sufficient clearance to prevent jamming and any hinges should have pins or bearings of
non-corrodible material.
6.6 Structures and spaces considered to be non-weathertight should be provided with
efficient drainage.
6.7 Where cargo is to be stowed on deck, the stowage arrangement should be such as to
not impede the free flow of water from the deck.
6.8 A vessel intended to operate in sea areas where ice accretion can occur should be
specially considered with regard to water freeing arrangements (also see section
11.1.1.4).
6.9 Where independent self-contained wheelhouses are fitted, provisions are to be made
so that such wheelhouses can drain quickly, typically in the event of wheelhouse window
failure and consequential flooding.