Section 7 Pipe systems and their fittings

7.1.1 The arrangement of valves, cocks and their connections is to be such as to prevent the possibility of one watertight compartment being placed in communication with another, or of dry cargo spaces, machinery spaces or other dry compartments being placed in communication with the waterway or with tanks. For this purpose, screw-down nonreturn valves are to be provided in the following fittings:

• Bilge valve distribution chests.
• Bilge suction hose connections, whether fitted direct to the pump or on the main bilge line.
• Direct bilge suctions and bilge pump connections to the main bilge line.

7.2.1 Bilge pipes which are required for draining cargo or machinery spaces are to be entirely distinct from water inlet pipes or from pipes which may be used for filling or emptying spaces where water or oil is carried.

7.3.1 Suctions for bilge drainage in machinery spaces are so far as practicable to be led from easily accessible mud boxes with straight tail pipes to the bilges and having covers secured in such a manner as to permit their being expeditiously opened or closed. Strum boxes are not to be fitted to the lower ends of these tail pipes.

7.3.2 Where compliance with Pt 5, Ch 11, 7.3 Machinery space suctions – Mud boxes 7.3.1 is not practicable, strum boxes as described in Pt 5, Ch 11, 7.4 Hold and other compartment suctions – Strum boxes 7.4.1 are to be fitted to the bilge suctions in the machinery space.

7.4.1 The open ends of bilge suctions in holds and other compartments outside machinery spaces such as cofferdams and tanks other than those permanently arranged for the carriage of fresh water, water ballast, fuel oil or liquid cargo and for which other efficient means of pumping are provided are to be enclosed in strum boxes. The strum boxes are to be provided with perforations of not more than 10 mm diameter, whose combined area is not less than twice that required for the suction pipe. The boxes are to be so constructed that they can be cleared without breaking any joint of the suction pipe.

7.5.1 The distance between the foot of all bilge tail pipes and the bottom of the bilge is to be adequate to allow a full flow of water and to facilitate cleaning.

7.6.1 Bilge valves, cocks and mud boxes are to be fitted at, or above, the machinery space platforms. Where this is not practicable, they may be situated just below the platform, provided readily removable traps or covers are fitted, and nameplates indicate the presence of these fittings.

7.7.1 Bilge suction pipes are not to be led through double bottom tanks if it is possible to avoid doing so.

7.7.2 Bilge pipes which have to pass through these tanks are to have a wall thickness in accordance with Table 10.2.3 Minimum thickness for steel pipes. The thickness of pipes made from material other than steel will be specially considered.

7.7.3 Expansion bends, not glands, are to be fitted to these pipes within the tanks, and the pipes are to be tested, after installation, to the same pressure as the tanks through which they pass.

7.8.1 In way of deep tanks, bilge pipes should preferably be led through pipe tunnels but, where this is not done, the pipes are to be of steel, having a wall thickness in accordance with Table 10.2.3 Minimum thickness for steel pipes, with welded joints or heavy flanged joints. The number of joints is to be kept to a minimum.

7.8.2 Expansion bends, not glands, are to be fitted to these pipes within the tanks, and the open ends of the bilge suction pipes in the holds are to be fitted with non-return valves of the special type approved for use in holds, see Pt 5, Ch 11, 7.9 Hold bilge non-return valves 7.9.1.

7.8.3 The pipes are to be tested, after installation, to a pressure not less than the maximum head to which the tanks can be subjected in service.

7.9.1 Where non-return valves are fitted to the open ends of bilge suction pipes in cargo holds in order to decrease the risk of flooding, they are to be of an approved type which does not offer undue obstruction to the flow of water.