Section 5 Air, overflow and sounding pipes

5.1.1 Air pipes are to be fitted to all tanks, cofferdams, and other compartments which are not fitted with alternative ventilation arrangements.

5.1.2 Air pipes are to be fitted at the opposite end of the tank to that which the filling pipes are placed and/or at the highest part of the tank. Where the tank top is of unusual or irregular profile, consideration will be given to the number and position of the air pipes.

5.1.3 Air pipes to tanks containing flammable liquids which are located in or pass through compartments of high fire risk, or are in the open, are to be of steel or other equivalent material.

5.2.1 Air pipes to tanks and cofferdams extending to the shell plating, or tanks which can be run up from the sea are to be led to above the weather deck.

5.2.2 Air pipes from storage tanks containing hydraulic oil may terminate in the machinery space, provided the open ends are so situated that issuing oil cannot come into contact with electrical equipment or heated surfaces.

5.3.1 Closing appliances fitted to tank air pipes are to be of a type which will allow the free passage of air or liquid to prevent the tanks being subjected to a pressure or vacuum greater than that for which they are designed, and prevent the free entry of water into the tanks.

5.3.2 Air pipe closing devices are to be type tested in accordance with the test requirements of LR’s Type Approval Test Specification Number 2. The flow characteristic of the closing device is to be determined using water. See Pt 4, Ch 5, 5.5 Size of air pipes.

5.3.3 If closing appliances are not fitted, air pipes are to be fitted with a goose neck at the open end.

5.4.1 Nameplates are to be affixed to the upper ends of all air and sounding pipes.

5.5.1 In all cases, whether a tank is filled by on-board pumps or other means, the total cross-sectional area of air pipes is to be not less than 25 per cent greater than the effective area of the respective filling pipe.

5.5.2 Air pipes are to be generally not less than 38 mm bore. In the case of small gravity filled tanks smaller bore pipes may be accepted but in no case is the bore to be less than 25 mm.

5.6.1 For all tanks which can be pumped up, overflow pipes are to be fitted where the pressure head corresponding to the height of the air pipe is greater than that for which the tank is designed.

5.6.2 In the case of tanks containing flammable liquids, the overflow pipe is to be led to an overflow tank of adequate capacity or to a storage tank having a space reserved for overflow purposes. Suitable means are to be provided to indicate when overflow is occurring.

5.6.3 Overflow pipes are to be self draining under normal conditions of operation.

5.6.4 Where overflow sight glasses are provided, they are to be in a vertical dropping line and designed such that the oil does not impinge on the glass. The glass is to be of heat resisting quality and adequately protected from mechanical damage.

5.7.1 Where a combined air or overflow system is fitted, the arrangement is to be such that in the event of any one of the tanks being bilged, the other tanks cannot be flooded from the sea through combined air pipes or the overflow main. For this purpose, it will normally be necessary to lead the overflow pipe to a point above the waterline.

5.7.2 Where a common overflow main is provided, the main is to be sized to allow any two tanks connected to that main to overflow simultaneously.

5.8.1 Provision is to be made for sounding all tanks and the bilges of those compartments which are not at all times readily accessible. The soundings are to be taken as near the suction pipes as practicable.

5.8.2 An approved level gauge or remote reading level device may be accepted in lieu of a sounding pipe.

5.8.3 Sounding pipes are to be not less than 32 mm internal diameter.

5.9.1 Except as permitted by Pt 4, Ch 5, 5.10 Short sounding pipes, sounding pipes are to be led to positions which are at all times accessible above the weather deck and, in the case of tanks containing flammable liquids, the sounding pipes are to be led to safe positions in the open.

5.10.1 In machinery spaces, where it is not practicable to extend sounding pipes as mentioned in Pt 4, Ch 5, 5.9 Termination of sounding pipes short sounding pipes extending to readily accessible positions above the platform may be fitted.

5.10.2 Short sounding pipes to oil tanks are to be fitted with cocks having parallel plugs with permanently attached handles, so loaded that, on being released, they automatically close the cocks.