Section 3 Air and sounding pipes

3.1.1 Air pipes located on the exposed deck over the forward 0,25L of the rule length, of ships of sea-going service of length 80 m or more, where the height of the exposed deck in way of the item is less than 0,1L or 22 m above the summer load waterline, whichever is the lesser, are to comply with the requirements of Section 5. All other air and sounding pipes are to comply with the following requirements in addition to the applicable requirements of Pt 5, Ch 13, 12 Air, overflow and sounding pipes and Pt 5, Ch 15, 2 Piping systems for bilge, ballast, fuel oil, etc..

3.1.2 Striking plates of suitable thickness, or their equivalent, are to be fitted under all sounding pipes.

3.1.3 On offshore supply ships, air pipes are to be situated clear of the cargo containment areas.

3.2.1 The height of air pipes from the upper surface of decks exposed to the weather, to the point where water may have access below, is normally to be not less than:

• 760 mm on the freeboard deck;
• 450 mm on the superstructure deck;

these heights being measured above deck sheathing, where fitted.

3.2.2 Lower heights may be approved in cases where these are essential for the working of the ship, provided that the design and arrangements are otherwise satisfactory. In such cases, efficient, permanently attached closing appliances of an approved automatic type will generally be required.

3.2.3 The height of air pipes may be required to be increased on ships of Type `A', Type `B-100' and Type `B-60' where this is shown to be necessary by the floatability calculations required by the International Convention on Load Lines, 1966. An increase in height may also by required or recommended by individual Administrations when air pipes to fuel oil and settling tanks are situated in positions where sea water could be temporarily entrapped, e.g. in recesses in the sides and ends of superstructures or deckhouses, between hatch ends, behind high sections of bulwark, etc. This may entail an increase in tank scantlings, see also Pt 3, Ch 3 Structural Design.

3.2.4 Air pipes are generally to be led to an exposed deck. For alternative arrangements in an enclosed space on a main vehicle deck, see Pt 4, Ch 2, 9 Subdivision structure on vehicle deck.

3.2.5 Where air pipes are led through the side of superstructures, the opening is to be at least 2,3 m above the summer load waterline.

3.2.6 The minimum wall thickness of air pipes in positions indicated in Pt 3, Ch 12, 3.2 Height of air pipes 3.2.1 is to be:

• 6,0 mm for pipes of 80 mm external diameter or smaller;
• 8,5 mm for pipes of 165 mm external diameter or greater.

Intermediate minimum thicknesses are to be determined by linear interpolation.

3.2.7 Where permitted by the National Authority, air pipe coaming heights may be reduced on ships engaged on protected or extended protected water service. Coaming heights are to be as high as practicable, with a minimum height of 450 mm on the freeboard deck and 300 mm on a superstructure deck.

3.3.1 All openings of air and sounding pipes are to be provided with permanently attached, satisfactory means of closing to prevent the free entry of water, see also Pt 3, Ch 12, 3.2 Height of air pipes 3.2.2.

3.3.2 In general, closing appliances are to be of an approved automatic type where, with the ship at its summer waterline, the openings are immersed at an angle of heel of 40° or, the angle of down flooding if this is less than 40° which may be agreed on the basis of stability requirements. On ships such as passenger ships where the angle of down flooding is greater than 40°, the extent of approved automatic type is to be suitably increased to extend up to the actual angle of down flooding.

3.3.3 Where the closing appliances are not of an automatic type, provision is to be made for relieving the vacuum when the tanks are being pumped out.

3.3.4 Pressure/vacuum valves as required by Pt 5, Ch 15, 4 Cargo tank venting, purging and gas-freeing may be accepted as closing appliances for cargo tanks.