PART 4 SECTION 6|19 Pumps and Piping Systems

fitted, the area of the overflow is to be at least 125%of the effective area of the filling line and the ventsneed not exceed the above minimum size.

Notwithstanding the above, the pump capacityand pressure head are to be considered in the sizingof vents, and overflows; when high capacity and/orhigh head pumps are used, calculations demonstratingthe adequacy of the vent and overflows are to besubmitted.

4/6.43.4 LocationVents for compartments required for subdivision(such as double bottom or wing spaces) are to be ledto above the freeboard or bulkhead deck. Inaddition, vents for ballast tanks, fuel oil tanks, andthose cofferdams adjacent to fuel oil tanks are to beled to the weather. Vents for other tanks mayterminate within the machinery space but are to belocated so as to preclude the possibility ofoverflowing on electrical equipment, engines orheated surfaces.

4/6.43.5 Vent OutletsAll vent and overflow pipes on the open deck are toterminate by way of return bends.

a Fuel Oil Tank Vents Vent outlets from fueloil tanks are to be fitted with corrosion-resistantflame screens having a clear area through the mesh ofnot less than the required area of the vent pipe.

b Weathertight Closure Satisfactory means,permanently attached, are to be provided for closingthe openings of the vent pipes. The means of closingvent pipes is to be weather tight. Closing devices areto be automatic if, while the craft is at its draughtcorresponding to summer loadline, or timber summerload line where assigned, the openings of the air pipessubmerge at angles up to 40 degrees or up to a lesserangle which may be accepted on the basis of stabilityrequirements. Automatic devices are also to be fittedon vents for craft designed for the carriage of deckcargoes which may prevent access to the vents.

4/6.45 Overflow Pipes

Overflow pipes discharging through the side of thecraft are to be located as far above the deepestloadline as practicable and are to be provided withnon-return valves located on the craft's side. Wherethe overflow does not extend above the freeboarddeck, there is to be provided in addition an efficientand accessible means for preventing water frompassing inboard. Such means may consist of a non-return valve located in an accessible position abovethe deepest loadline.

Where it is impracticable to locate the valve in anaccessible position, one non-return valve withpositive means for closing from an accessible positionabove the freeboard or bulkhead deck will be

acceptable, provided there are suitable arrangementsto insure the valve not being closed by unauthorizedpersons and provided a notice is posted in aconspicuous place at the operating station to theeffect that the valve is never to be closed except asmay be required in an emergency.

Overflow pipes from combustible and flammableliquid tanks are to be led to an overflow tank ofadequate capacity or to a storage tank having spacereserved for overflow purposes. An alarm device isto be provided to give warning when the liquidreaches a predetermined level in the overflow tank.The sight glasses are to be fitted only in verticalsections of overflow pipes.

When overflows from the tanks in more than onewatertight subdivision are connected to a commonheader below the freeboard or bulkhead deck, thearrangement is to be such as to prevent fore-and-aftflooding of one watertight bulkhead subdivision fromanother in the event of damage.

4/6.47 Sounding

4/6.47.1 GeneralAll tanks are to be fitted with a suitable means ofdetermining the level of the liquid therein. Suchmeans may be sounding pipes, gauge glasses, or otherapproved level indicating systems or devices.

Compartments, including cofferdams and pipetunnels, which are not readily accessible are to befitted with sounding pipes if the compartment isadjacent to the sea or has pipes carrying liquidspassing through it.

4/6.47.2 Sounding PipesSounding pipes are not to be less than 38 mm (1.5 in.)inside diameter. They are to be led as straight aspossible from the lowest part of the tank orcompartment to the bulkhead deck or to a positionwhich is always accessible. If sounding pipesterminate below the freeboard deck, they are to beprovided with means for closing in the followingmanner:

a Oil Tanks Quick-acting, self-closing gatevalves are required.

b Other Tanks A screw cap secured to the pipewith a chain or a gate valve is required.

Provision is to be made to prevent damaging thecraft's plating by the striking of the sounding rod. Ingeneral sounding pipes are not to pass through bilgewells, but if this is not practicable, the pipe is to be atleast extra-heavy in the bilge well. Sounding pipesfor combustible or flammable fluids are not toterminate in accommodation spaces.