3. Drainage arrangements for passenger ships
3.1 Arrangements above the bulkhead deck
3.1.1 Above the bulkhead deck, except as provided in paragraph 1.1.2 above, an adequate number of properly-sized drains should be provided on each deck to ensure that the combined water flow from the fixed fire-extinguishing system and the required number of fire hoses can be rapidly discharged overboard or drain to a bilge system with a reservoir tank fitted with a high water level alarm.
3.1.2 At least four drains should be located on each side of the protected space, uniformly distributed fore and aft. Freeing ports should not be installed in enclosed superstructures, as defined by regulation 3.10 of the ICLL 66.
3.1.3 The drainage system on each side of the deck should have an aggregate capacity of not less than 125% of the maximum flow rate of the fixed fire-extinguishing system water pumps plus the flow from two fire hoses (four if required by SOLAS regulation II-2/19.3.1.2). In case an automatic deep well or submersible pumping system is installed, the bilge pump capacity can be subtracted from the required drainage capacity.
3.1.4 Minimum capacity of drains
The minimum capacity of scuppers, freeing ports or a combination thereof should be determined in accordance with the provisions of paragraphs 3.1.4.1 or 3.1.4.2, respectively.
3.1.4.1 The minimum required area of scuppers and connected piping should be determined by the following formula:
where:
A is the total required sectional area of the drains on each side of the deck in m2;
Q is the combined waterflow from the fixed fire-extinguishing system and the required number of fire hoses in m3/s;
h is the elevation head difference between the bottom of the scupper well or suction level and the overboard discharge opening or highest approved load line in m; and
hl is the summation of head losses corresponding to scupper piping, fittings and valves in m.
In no case should the area of each individual drain be less than 0.0078 m2 or 125 mm diameter piping.
3.1.4.2 The minimum required area of freeing ports should be determined by the following formula:
where:
A is the total required sectional area of freeing ports on each side of the ship in m2;
Q is the combined waterflow from the fixed fire-extinguishing system and the required number of fire hoses in m3/s; and
h1-h2 is the depth of water on the deck determined in accordance with paragraph 4.2.
If the cross-sectional area of freeing ports required by the ICLL 66 is equal to or greater than determined above, additional freeing ports are not required.
3.2 Arrangements below the bulkhead deck
3.2.1 Below the bulkhead deck, except as provided in paragraph 1.1.2 above, an efficient bilge pumping system should be provided to ensure that the combined waterflow from the fixed fire-extinguishing system and the required number of fire hoses can be rapidly collected and led to suitable arrangements for discharge overboard. The bilge system capacity should be not less than that required by paragraph 3.2.3.
3.2.2 The bilge piping system should be arranged in accordance with SOLAS chapter II-1. At least four bilge wells should be located on each side of the protected space, uniformly distributed fore and aft.
3.2.3 The bilge pumping system on each side of the ship should have an aggregate capacity of not less than 125% of the maximum flow rate of the fixed fire-extinguishing system water pumps plus the flow from two fire hoses (four, if required by SOLAS regulation II-2/19.3.1.2).
3.2.4 The required area of the main and branch bilge pipes for the protected space should be adequate to ensure a maximum waterflow of 2 m/s in each section of piping in accordance with paragraphs 3.2.4.1 to 3.2.4.3.
3.2.4.1 If the drainage system is a bilge pumping system, the following three criteria should be satisfied:
where:
Qbpump is the combined capacity of all power bilge pumps except the emergency bilge pump in m3/s;
Q is the combined waterflow from the fixed fire-extinguishing system and the required number of fire hoses in m3/s;
AM is the sectional area of the main bilge pipe of the protected space in m2;
AB is the total sectional area of branched bilge pipes for each side in m2.
3.2.4.2 If the drainage system is based on gravity drains leading to a reservoir tank, the minimum required area of drains and connected piping should be determined by paragraph 3.1.4.
3.2.4.3 If the drainage system is a combined system, the relevant dimensioning for each part of the system should be determined using paragraphs 3.2.4.1 and 3.2.4.2.
3.2.5 The required capacity of each bilge well should be at least 0.15 m3.
3.2.6 If the system includes a reservoir tank, the tank should have adequate capacity for at least 20 min of operation at the required drainage capacity for the affected space.