Section 3 Drainage of compartments, other than machinery spaces

3.1.1 All ships are to be provided with efficient dewatering arrangements, having suctions and means for drainage so arranged that any water within any compartment of the ship, or any watertight section of any compartment, can be pumped out through at least one suction when the ship is on an even keel and is either upright or has a list of not more than 5°. For this purpose, wing suctions will generally be necessary, except in short, narrow compartments where one suction can provide effective drainage under the above conditions.

3.1.2 The dewatering system arrangements are to be capable of draining any watertight compartment under all practicable conditions after a casualty, whether the ship is upright or listed.

3.1.3 The requirements for dewatering system arrangements recognise that naval ships commonly use eductors for dealing with large amounts of water ingress into machinery spaces and other compartments.

3.1.4 Bilge piping systems for dealing with small amounts of oily water accumulation in machinery spaces and installed for the prevention of pollution of the sea by oil are not considered an effective means of dealing with large amounts of water ingress referred to in Vol 2, Pt 7, Ch 2, 3.1 General 3.1.3. The arrangement of valves and fittings is however, to comply with the requirements of Vol 2, Pt 7, Ch 2, 7 Pipe systems and their fittings for the prevention of communication between compartments.

3.1.5 Where it is intended to carry flammable or toxic liquids in enclosed spaces, the bilge system shall be designed to prevent pumping of such liquids through piping and pumps in machinery or other spaces where a source of ignition may exist. Depending on the quantities of such liquids carried, an additional means of drainage may be required for their compartments.

3.1.6 For a normally inaccessible small void compartment, such as an echo sounding compartment, which is accessed from within a normally inaccessible space, such as a forepeak tank, alternative drainage arrangements to those required by Vol 2, Pt 7, Ch 2, 3.1 General 3.1.1 may be considered. For such arrangements, a warning notice is to be located in a prominent position specifying the precautions to be taken prior to opening the manhole of the small void compartment. Means are to be provided to indicate flooding of the compartment without opening, such as fitting indicator plugs to the manhole. Drainage arrangements are to be submitted to LR for approval.

3.2.1 All tanks (including double bottom tanks), whether used for ballast or fuel oil, are to be provided with suction pipes, led to suitable power pumps, from the after end of each tank. Ballast tanks may be drained by the use of eductors and filled by using a suitable sea water supply system. Where the sea water supply system for filling ballast tanks is used for other purposes, the availability of supply is to be sufficient for all operational requirements.

3.2.2 In general, the drainage arrangements are to be in accordance with Vol 2, Pt 7, Ch 2, 3.1 General. However, where the tanks are divided by longitudinal watertight bulkheads or girders into two or more tanks, a single suction pipe, led to the after end of each tank, will normally be acceptable.

3.2.3 Similar drainage arrangements are to be provided for cofferdams, except that the suctions may be led to the bilge or dewatering system.

3.3.1 Fuel oil, lubrication oil and other flammable liquids are not to be carried in forepeak tanks.

3.3.2 Where the peaks are used as tanks, a power pump or suitable eductor suction is to be led to each tank, except in the case of small tanks used for the carriage of domestic fresh water, where hand pumps may be used.

3.3.3 Where the peaks are not used as tanks, and bilge or dewatering suctions are not fitted, drainage of both peaks may be effected by hand pump suctions, provided that the suction lift is well within the capacity of the pumps and in no case exceeds 7,3 m.

3.3.4 Pipes piercing the collision bulkhead are to be fitted with suitable screw-down valves operable from above the damage control deck. The valve chest is to be fitted to the aft side of the bulkhead unless the use of that space precludes the valve being readily accessible in all service conditions, in which case the valve chest is to be secured to the bulkhead inside the fore peak. An indicator is to be provided to show whether the valve is open or closed.

3.4.1 Provision is to be made for the drainage of the chain locker and watertight compartments above the fore peak tank by hand pump, power pump or eductor suctions.

3.4.2 Steering gear compartments or other small enclosed spaces situated above the after peak tank are to be provided with suitable means of drainage, either by hand pump, power pump or eductor suctions.

3.4.3 Subject to special approval of any applicable subdivision requirements, compartments referred to in Vol 2, Pt 7, Ch 2, 3.3 Fore and after peaks 3.3.2 that are adequately isolated from the adjacent tween decks, may be drained by scuppers of not less than 38 mm bore, discharging to the tunnel (or machinery space in the case of ships with machinery aft) and fitted with self-closing cocks situated in well lighted and visible positions.

3.5.1 The intactness of the machinery space bulkheads, and of tunnel plating required to be of watertight construction, is not to be impaired by the fitting of scuppers discharging to machinery space or tunnels from adjacent compartments which are situated below the bulkhead deck. These scuppers may, however, be led into a strongly constructed scupper drain tank situated in the machinery space or tunnel, but closed to these spaces and drained by means of a suction of appropriate size led from the bilge or dewatering system through a screw-down non-return valve.

3.5.2 The scupper tank air pipe is to be led to above the vertical limit of watertight integrity, and provision is to be made for ascertaining the level of water in the tank.

3.5.3 Where one tank is used for the drainage of several watertight compartments, the scupper pipes are to be provided with screw-down non-return valves.

3.5.4 No open ended drain valve or cock is to be fitted to the collision bulkhead. Drain valves or cocks are not to be fitted to other watertight bulkheads if alternative means of drainage are practicable.

3.5.5 Where drain valves or cocks are fitted to bulkheads other than the collision bulkhead, as permitted by Vol 2, Pt 7, Ch 2, 3.5 Maintenance of integrity of bulkheads 3.5.4, the drain valves or cocks are to be at all times readily accessible and are to be capable of being shut off from positions above the bulkhead deck. Indicators are to be provided to show whether the drains are open or shut.