Section 4 Additional bilge drainage requirements for column-stabilised units and self-elevating units

4.1.1 In accommodation units, the power bilge pumps required by Pt 5, Ch 13, 6.1 Number of pumps 6.1.5 of the Rules for Ships are to be placed, if practicable, in separate watertight compartments which will not readily be flooded by the same damage. If the engines and boilers are in two or more watertight compartments, the bilge pumps are to be distributed throughout these compartments so far as is possible. See also Pt 5, Ch 13, 6 Pumps on bilge service and their connections of the Rules for Ships.

4.1.3 The bilge main is to be so arranged that no part is situated nearer the side of the unit than B/5, measured at right angles to the centreline at the level of the deepest subdivision load line, where B is the breadth of the unit.

4.1.4 Where any bilge pump or its pipe connection to the bilge main is situated outboard of the B/5 line, a non-return valve is to be provided in the pipe connection at the junction with the bilge main. The emergency bilge pump and its connections to the bilge main are to be so arranged that they are situated inboard of the B/5 line.

4.2.1 Provision is to be made to prevent the compartment served by any bilge suction pipe being flooded, in the event of the pipe being severed, or otherwise damaged by collision or grounding in any other compartment. For this purpose, where the pipe is at any part situated nearer the side of the unit than B/5 or in a duct keel, a non-return valve is to be fitted to the pipe in the compartment containing the open end.

4.3.1 All the distribution boxes, valves and cocks in connection with the bilge pumping arrangements are to be so arranged that, in the event of flooding, one of the bilge pumps may be operative on any compartment. If there is only one system of pipes common to all pumps, the necessary valves or cocks for controlling the bilge suctions must be capable of being operated from the bulkhead deck. Where, in addition to the main bilge pumping system, an emergency bilge pumping system is provided, it is to be independent of the main system and so arranged that a pump is capable of operating on any compartment under flooding conditions; in this case, only the valves and cocks necessary for the operation of the emergency system need be capable of being operated from above the bulkhead deck.

4.3.2 All valves and cocks in Pt 5, Ch 13, 4.3 Arrangement and control of bilge valves 4.3.1 which can be operated from above the bulkhead deck are to have their controls at their place of operation clearly marked and provided with means to indicate whether they are open or closed.

4.4.1 Where divided deep tanks or side tanks are provided with cross-flooding arrangements to limit the angle of heel after side damage, the arrangements are to be self-acting where practicable. In any case, where controls to cross-flooding fittings are provided, they are to be operable from above the bulkhead deck. Additional bilge drainage requirements for column-stabilised units and self-elevating units are given in Pt 5, Ch 13, 4.5 General to Pt 5, Ch 13, 4.7 Self-elevating units.

4.5.1 The bilge system is to be capable of operating satisfactorily under the conditions specified in Table 1.1.2 or 1.1.3 in Chapter 1.

4.5.2 Dry compartments below the lowest continuous deck on self-elevating units, and below the main deck on column-stabilised units, containing essential equipment for the operation and safety of the unit, or providing essential buoyancy, are to have a permanently installed bilge pumping system.

4.5.3 Where the open drain pipe is carried through a watertight bulkhead or deck, it is to be fitted with an easily accessible self-closing valve at the bulkhead or deck, or a valve capable of being closed from above the damage waterline.

4.5.4 A mimic panel showing all the compartments and arrangements of the bilge and drainage systems is to be suitably positioned at the central control station.

4.6.1 The internal diameter of branch suctions from each compartment is not to be less than stipulated by the following formula, rounded to the nearest 5 mm size:

d

=

where

A is wetted surface m² of the compartment, excluding stiffening members when the compartment is half filled with water.

4.6.2 The internal diameter of any bilge line is not to be less than 50 mm.

4.6.3 The cross sectional area of the main bilge line is not to be less than the sum of the cross sectional areas of the two largest branch bilge lines.

4.6.4 Each bilge pump is to be capable of giving a speed of water through the bilge main of not less than 2 m/s under ordinary working conditions.

4.6.5 At least one of the pumps referred to in Pt 5, Ch 13, 6 Pumps on bilge service and their connections of the Rules for Ships is to be arranged solely for bilge pumping duties. This pump and the pump-room bilge suction valves are to be capable of both remote and local operation.

4.6.6 Bilge drainage systems as defined above are not to directly connect compartments of different hazard classifications.

4.6.7 All distribution boxes and manually operated valves in connection with the bilge pumping arrangements are to be in positions which are accessible under normal circumstances. Where such valves are located in normally unmanned spaces below the assigned load line which are not provided with high bilge water level alarms, they are to be operable from outside the space. A means to indicate whether a valve is open or closed is to be provided at each location from which the valve can be controlled. The indicator is to rely on movement of the valve spindle.

4.6.8 Propulsion rooms and pump-rooms in lower hulls, which are normally unattended, are to be provided with two independent systems for bilge water high level detection, providing an audible and visual alarm at the central control station.

4.6.9 Chain lockers which, if flooded, could substantially affect the unit’s stability are to be provided with a remote means to detect flooding, a permanently installed means of dewatering and remote indication provided at the central control station. The dewatering system is to be independent of the main bilge system and the pumps are to have adequate reserve capacity to keep the chain locker empty in any damage condition. The minimum discharge capacity of the pumps is not to be less than the flow rate calculated using the internal diameter of the chain pipe when subjected to a head of water measured from the top of the chain pipe to the 4 m waterline defined in Pt 4, Ch 7, 4.7 Weathertight integrity related to stability 4.7.2

4.7.1 The bilge system is to be arranged so that essential compartments such as machinery and pump-rooms can be emptied even when the unit is in the flooded condition. The control and position indication system for the bilge valves is to be suitable for operation if the equipment should become submerged.

4.7.2 At least one of the pumps referred to in Pt 5, Ch 13, 6 Pumps on bilge service and their connections of the Rules for Ships is to be arranged solely for bilge pumping duties.

4.7.3 Chain lockers, if fitted, may be emptied by means of portable pumps or permanently installed pumps or ejectors. Where the utilisation of portable pumps is intended, two units are to be carried on board.