Regulation 24 - Freeing ports

  (1)

• (a) Where bulwarks on the weather portions of freeboard or superstructure decks form wells, ample provision shall be made for rapidly freeing the decks of water and for draining them.

• (b) Except as provided in paragraphs (1)(c) and (2), the minimum freeing port area (A) on each side of the ship for each well on the freeboard deck shall be that given by the following formulae in cases where the sheer in way of the well is standard or greater than standard.

• The minimum area for each well on superstructure decks shall be one-half of the area given by the following formulae:

• Where the length of bulwark (l) in the well is 20 m or less:

  

  where l exceeds 20 m:

  

  l need in no case be taken as greater than 0.7L.

• If the bulwark is more than 1.2 m in average height, the required area shall be increased by 0.004 m² per metre of length of well for each 0.1 m difference in height. If the bulwark is less than 0.9 m in average height, the required area may be decreased by 0.004 m² per m of length of well for each 0.1 m difference in height.

• (c) In ships with no sheer, the area calculated according to paragraph (b) shall be increased by 50%. Where the sheer is less than the standard, the percentage shall be obtained by linear interpolation.

• (d) On a flush deck ship with a deckhouse amidships having a breadth at least 80% of the beam of the ship and the passageways along the side of the ship not exceeding 1.5 m in width, two wells are formed. Each shall be given the required freeing port area based upon the length of each well.

• (e) Where a screen bulkhead is fitted completely across the ship at the forward end of a midship deckhouse, the exposed deck is divided into two wells and there is no limitation on the breadth of the deckhouse.

• (f) Wells on raised quarterdecks shall be treated as being on freeboard decks.

• (g) Gutter bars greater than 300 mm in height fitted around the weather decks of tankers in way of cargo manifolds and cargo piping shall be treated as bulwarks. Freeing ports shall be arranged in accordance with this regulation. Closures attached to the freeing ports for use during loading and discharge operations are to be arranged in such a way that jamming cannot occur while at sea.

  (2) Where a ship fitted with a trunk does not comply with the requirements of regulation 36(1)(e) or where continuous or substantially continuous hatchway side coamings are fitted between detached superstructures, the minimum area of the freeing port openings shall be calculated from the following table:

The area of freeing ports at intermediate breadths shall be obtained by linear interpolation.

  (3) The effectiveness of the freeing area in bulwarks required by paragraph (1) depends on the free flow area across the deck of a ship.

 The free flow area on deck is the net area of gaps between hatchways, and between hatchways and superstructures and deckhouses up to the actual height of the bulwark.

 The freeing port area in bulwarks shall be assessed in relation to the net free flow area as follows:

• (a) If the free flow area is not less than the freeing area calculated from paragraph (2) as if the hatchway coamings were continuous, then the minimum freeing port area calculated from paragraph (1) shall be deemed sufficient.

• (b) If the free flow area is equal to, or less than the area calculated from paragraph (1), the minimum freeing area in the bulwarks shall be determined from paragraph (2).

• (c) If the free flow area is smaller than calculated from paragraph (2), but greater than calculated from paragraph (1), the minimum freeing area in the bulwark shall be determined from the following formula:

  
  where:

  F 1	=	is the minimum freeing area calculated from paragraph (1);
  F 2	=	is the minimum freeing area calculated from paragraph (2); and
  f p	=	is the total net area of passages and gaps between hatch ends and superstructures or deckhouses up to the actual height of bulwark.

  (4) In ships having superstructures on the freeboard deck or superstructure decks, which are open at either or both ends to wells formed by bulwarks on the open decks, adequate provision for freeing the open spaces within the superstructures shall be provided.

 The minimum freeing port area on each side of the ship for the open superstructure (A _s) and for the open well (A _w), shall be calculated in accordance with the following procedure:

• (a) Determine the total well length (l _t) equal to the sum of the length of the open deck enclosed by bulwarks (l _w) and the length of the common space within the open superstructure (l _s).

• (b) To determine A _s:

  • (i) calculate the freeing port area (A) required for an open well of length l _t in accordance with paragraph (1) with standard height bulwark assumed;

  • (ii) multiply by a factor of 1.5 to correct for the absence of sheer, if applicable, in accordance with paragraph (1)(c);

  • (iii) multiply by the factor (b _o/l _t) to adjust the freeing port area for the breadth (b _o) of the openings in the end bulkhead of the enclosed superstructure;

  • (iv) to adjust the freeing port area for that part of the entire length of the well which is enclosed by the open superstructure, multiply by the factor:

    

    where l _w and l _t are defined in paragraph (4)(a);

  • (v) to adjust the freeing port area for the distance of the well deck above the freeboard deck, for decks located more than 0.5 h_s above the freeboard deck, multiply by the factor:

    

    where h _w is the distance of the well deck above the freeboard deck and h _s is one standard superstructure height.

• (c) To determine A _w:

  • (i) the freeing port area for the open well (A _w) shall be calculated in accordance with paragraph (b)(i), using l _w to calculate a nominal freeing port area (A'), and then adjusted for the actual height of the bulwark (h _b) by the application of one of the following area corrections, whichever is applicable:

  • for bulwarks greater than 1.2 m in height:

    

  • for bulwarks less than 0.9 m in height:

    

  • for bulwarks between 1.2 m and 0.9 m in height there is no correction (i.e. A _c = 0);

  • (ii) the corrected freeing port area (A _w = A’ + A _c) shall then be adjusted for absence of sheer, if applicable, and height above freeboard deck as in paragraphs (b)(ii) and (b)(v), using h _s and h _w.

• (d) The resulting freeing port areas for the open superstructure (A _s) and for the open well (A _w) shall be provided along each side of the open space covered by the open superstructure and each side of the open well, respectively.

• (e) The above relationships are summarised by the following equations, assuming l _t, the sum of l _w and l _s, is greater than 20 m:

• freeing port area A _w for the open well:

  

• freeing port area A _s for the open superstructure:

  

  where l_t is 20 m or less, the basic freeing port area is A = 0.7 + 0.035l _t in accordance with paragraph (1).

  (5) The lower edges of freeing ports shall be as near the deck as practicable. Two-thirds of the freeing port area required shall be provided in the half of the well nearest the lowest point of the sheer curve. One third of the freeing port area required shall be evenly spread along the remaining length of the well. With zero or little sheer on the exposed freeboard deck or an exposed superstructure deck the freeing port area shall be evenly spread along the length of the well.

  (6) All freeing port openings in the bulwarks shall be protected by rails or bars spaced approximately 230 mm apart. If shutters are fitted to freeing ports, ample clearance shall be provided to prevent jamming. Hinges shall have pins or bearings of non-corrodible material. Shutters shall not be fitted with securing appliances.