Section 7 Piping systems and their fittings

7.1.1 Suctions from the main bilge line, i.e. branch bilge suctions, are to be arranged to draw water from any hold, compartment, watertight section or machinery compartment of the ship, excepting small spaces such as those mentioned in Pt 5, Ch 13, 3.1 General 3.1.6, Pt 5, Ch 13, 3.6 Fore and after peaks and Pt 5, Ch 13, 3.7 Spaces above fore peaks, after peaks and machinery spaces, where manual pump suctions are accepted, and are not to be of smaller diameter than that required by the formula in Pt 5, Ch 13, 5.2 Branch bilge suctions to cargo and machinery spaces 5.2.1, see also Pt 5, Ch 13, 7.4 Machinery space suctions − Mud boxes 7.4.1 and Pt 5, Ch 13, 7.5 Hold and other compartment suctions – Strum boxes 7.5.1. For special arrangements for oil tankers, see Pt 5, Ch 15 Piping Systems for Oil Tankers.

7.1.2 Where passenger or cargo ships are of a design having enclosed car decks or cargo spaces located on the bulkhead deck or on the freeboard deck special consideration will be given to the drainage arrangements where any fixed pressure water spray system is fitted, see also Pt 3, Ch 12, 4.1 General and Pt 5, Ch 13, 9.1 Bilge drainage requirements.

7.2.1 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 sea or with tanks. For this purpose, screw-down non-return 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 main bilge line.

7.3.1 Bilge pipes which are required for draining cargo or machinery spaces are to be entirely distinct from sea inlet pipes or from pipes which may be used for filling or emptying spaces where water or oil is carried. This does not, however, exclude a bilge ejection connection, a connecting pipe from a pump to its suction valve chest, or a deep tank suction pipe suitably connected through a changeover device to a bilge, ballast or oil line.

7.4.1 Suctions for bilge drainage in machinery spaces and tunnels, other than emergency suctions, are to be led from easily accessible mud boxes fitted 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 or to the emergency bilge suctions.

7.5.1 The open ends of bilge suctions in holds and other compartments outside machinery spaces and tunnels 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 having 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.

7.6.1 Bilge wells required by Pt 5, Ch 13, 3.2 Cargo holds 3.2.3 and Pt 5, Ch 13, 4.2 Machinery space with double bottom 4.2.2 are to be formed of steel plates and are to be not less than 0,15m³ capacity. In small compartments, steel bilge hats of reasonable capacity may be fitted.

7.6.2 In passenger ships, the depth of bilge wells in double bottom tanks will be specially considered.

7.6.3 Where access manholes to bilge wells are necessary, they are to be fitted as near to the suction strums as practicable.

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

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

7.8.2 Where relief valves are fitted to pumps having sea connections, these valves are to be fitted in readily visible positions above the platform. The arrangements are to be such that any discharge from the relief valves will also be readily visible.

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

7.9.2 Bilge pipes which have to pass through these tanks are to have a wall thickness in accordance with Table 12.2.4 Minimum thickness for steel pipes. (The thickness of pipes made from material other than steel will be specially considered).

7.9.3 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.

7.10.1 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 12.2.4 Minimum thickness for steel pipes in Pt 5, Ch 12 Piping Design Requirements, with welded joints or heavy flanged joints. The number of joints is to be kept to a minimum. Consideration will be given to pipes made from materials other than steel, see also Pt 5, Ch 12, 5 Plastic pipes.

7.10.2 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 13, 7.11 Hold bilge non-return valves 7.11.1.

7.10.3 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.

7.11.1 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.

7.12.1 In case of deep tanks and cargo holds which may be used for either water ballast or dry cargo, provision is to be made for blank flanging the water ballast filling and suction pipes when the tank or hold is being used for the carriage of dry cargo, and for blank flanging the bilge suction pipes when the tank or hold is being used for the carriage of water ballast. Change-over devices may be used for this purpose.

7.12.2 For arrangements when fuel oil or cargo oil (having a flash point of 60°C or above) is carried in deep tanks, see Pt 5, Ch 14, 4.14 Deep tanks for the alternative carriage of oil, water ballast or dry cargo.

7.12.3 Where a ship is designed for the alternative carriage of dry cargo or oil having a flash point below 60°C, the blanking arrangements will be specially considered.