Section
10 Air, overflow and sounding pipes
10.1 Materials
10.1.2 Air,
overflow and sounding pipes fitted above the weather deck are to be
of steel or equivalent material.
10.2 Nameplates
10.2.1 Nameplates
are to be affixed to the upper ends of all air and sounding pipes.
10.3 Air pipes
10.3.1 Air
pipes are to be fitted to all tanks, cofferdams, tunnels and other
compartments which are not fitted with alternative ventilation arrangements.
10.3.2 The
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, special
consideration will be given to the number and position of the air
pipes.
10.3.4 For
a normally inaccessible small void compartment such as an echo sounding
compartment, which is accessed from within a normally inaccessible
space such as a forepeak tank, alternative air pipe arrangements to
those required by Vol 2, Pt 7, Ch 2, 10.3 Air pipes 10.3.1 may
be considered. For such arrangements, a warning notice is to be located
in a prominent position specifying the precautions to be taken prior
to opening the manhole and entering the small void compartment. Ventilation
arrangements are to be submitted to LR for approval.
10.4 Termination of air pipes
10.4.1 Air
pipes to double bottom tanks, deep tanks extending to the shell plating,
or tanks which can be run up from the sea are to be led to above the
assumed damage waterline. Air pipes to fuel oil tanks, cofferdams
and all tanks which can be pumped up are to be led to the open. For
height of air pipes above deck, see
Vol 1, Pt 3, Ch 4, 7.2 Height of air pipes.
10.4.2 Air
pipes from storage tanks containing lubricating or hydraulic oil may
terminate in the machinery space, provided that the open ends are
so situated that issuing oil cannot come into contact with electrical
equipment or heated surfaces. Air pipes from heated lubricating oil
tanks are to be led to a safe position on open deck.
10.4.3 The
open ends of air pipes to fuel oil tanks are to be situated where
no danger will be incurred from issuing oil vapour when the tank is
being filled.
10.4.4 The
location and arrangement of air pipes for fuel oil service, settling
and lubricating oil tanks are to be such that in the event of a broken
vent pipe, this does not directly lead to the risk of ingress of sea-water
or rain water.
10.5 Gauze diaphragms
10.5.1 The
open ends of air pipes to fuel oil tanks are to be furnished with
a wire gauze diaphragm of incorrodible material which can be readily
removed for cleaning or renewal.
10.5.2 Where
wire gauze diaphragms are fitted at air pipe openings, the area of
the opening through the gauze is to be not less than the cross-sectional
area required for the pipe. See
Vol 2, Pt 7, Ch 2, 10.8 Overflow pipes.
10.6 Air pipe closing appliances
10.6.1 The closing appliances fitted to tank air pipes in accordance with Vol 1, Pt 3, Ch 4, 7 Air and sounding pipes are to be of an automatic
opening 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.
10.6.3 Wood
plugs and other devices which can be secured closed are not to be
fitted at the outlets.
10.6.5 Air
pipe automatic closing devices are to be constructed to allow inspection
of the closure and the inside of the casing as well as changing the
seals.
10.6.6 Efficient
ball or float seating arrangements are to be provided for the closures.
Bars, cages or other devices are to be provided to prevent the ball
or float from contacting the inner chamber in its normal state, and
made in such a way that the ball or float is not damaged when subjected
to liquid impact due to a tank being overfilled.
10.6.7 Air
pipe automatic closing devices are to be self-draining.
10.6.8 The
clear area through an air pipe closing device in the open position
is to be at least equal to the area of the inlet.
10.6.10 The
maximum allowable tolerances for wall thickness of floats are not
to exceed ±10 per cent of thickness.
10.6.11 The inner and the outer chambers of an automatic air pipe head are to be of
a minimum thickness of 6 mm. Where side covers are provided and their function is
integral to providing functions of the closing device as outlined in Vol 2, Pt 7, Ch 2, 10.6 Air pipe closing appliances 10.6.1, they shall
have a minimum wall thickness of 6 mm. If the air pipe head can meet the tightness test
in LR’s Type Approval Test Specification Number 2 without the side covers attached, then
the side covers are not considered to be integral to the closing device, in which case a
wall thickness less than 6 mm will be accepted.
10.6.12 Casings
of air pipe closing devices are to be of approved metallic materials,
adequately protected against corrosion.
10.6.13 For
galvanised steel air pipe heads, the zinc coating is to be applied
by the hot method and the thickness is to be 70 to 100 microns.
10.6.14 For
areas of the head susceptible to erosion (e.g. those parts directly
subjected to ballast water impact when the tank is being pressed up,
such as the inner chamber area above the air pipe plus an overlap
of 10° or more either side), an additional harder coating should
be applied. This is to be an aluminium-bearing epoxy, or other equivalent
coating, applied over the zinc.
10.6.15 Closures and seats made of non-metallic materials are to be compatible with
the media intended to be carried in the tank and with sea-water, and suitable for
operating at ambient temperatures between –25°C and 85°C.
10.6.16 The
requirements do not apply to arrangements for refuelling underway.
10.7 Size of air pipes
10.7.1 For
every tank which can be filled by the ship’s pumps, replenishment
at sea or from shore facilities, the total cross-sectional area of
the air pipes and the design of the air pipe closing devices are to
be such that when the tank is overflowing at the maximum pumping capacity
or maximum delivery filling rate available for the tank, it will not
be subjected to a pressure greater than that for which it is designed.
10.7.2 In
all cases, whether a tank is filled by ship’s pumps or other
means, the total cross-sectional area of the air pipes is to be not
less than 25 per cent greater than the effective area of the respective
filling pipe.
10.7.3 Where
tanks are fitted with cross flooding connections, the air pipes are
to be of adequate area for these connections.
10.7.4 Air
pipes are to be not less than 50 mm bore.
10.8 Overflow pipes
10.8.1 For
all tanks which can be filled by the ship’s pumps or by shore
pumps, overflow pipes are to be fitted where:
-
The total cross-sectional
area of the air pipe is less than that required by Vol 2, Pt 7, Ch 2, 10.7 Size of air pipes.
-
The pressure
head corresponding to the height of the air pipe is greater than that
for which the tank is designed.
10.8.2 In
the case of fuel oil and lubricating oil tanks, 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, or when
the contents reach a predetermined level in the tanks.
10.8.3 Overflow
pipes are to be self draining under normal conditions of trim.
10.8.4 Where
overflow sight glasses are provided, they are to be in a vertically
dropping line and designed such that the oil does not impinge on the
glass. The glass is to be of heat resisting quality, adequately protected
from mechanical damage and well lit.
10.9 Air and overflow systems
10.9.1 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, tanks
situated in other watertight compartments of the ship 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 close to the assumed damage waterline.
10.9.2 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
the combined air pipes or the overflow main.
10.9.3 Where
overflow from tanks which are used for the alternative carriage of
oil and water ballast are connected to an overflow system, arrangements
are to be made to prevent water ballast overflowing into tanks containing
oil.
10.9.4 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.
10.10 Sounding arrangements
10.10.1 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.
10.10.2 Bilges
of compartments which are not at all times readily accessible are
to be provided with sounding pipes.
10.10.3 Where fitted, sounding pipes are to be as straight as practicable, and if
curved to suit the structure of the ship, the curvature must be sufficiently easy to
permit the ready passage of the sounding rod or chain.
10.10.4 Sounding devices of approved type may be used in lieu of sounding pipes for sounding
tanks subject to the following conditions:
- Gauge glasses of any type are not to be used on oil fuel tanks
or tanks integral to the ship's structure.
- Sounding devices used on oil fuel tanks or tanks integral to the
ship’s structure are not to require penetrations below the top of the tank.
- These devices are to be tested, after fitting on board, to the
satisfaction of the Surveyors.
10.10.5 Where gauge glasses are used for indicating the level of liquid in tanks
containing lubricating oil, hydraulic oil or other flammable liquid, the glasses are to
be of the flat type of heat-resisting quality, adequately protected from mechanical
damage, and fitted with self-closing valves at the lower ends and at the top ends if
these are connected to the tanks below the maximum liquid level. The arrangement may
incorporate a single point of operation for the valves.
10.10.6 If
means of sounding, other than a sounding pipe, are fitted in any ship
for indicating the level of liquid in tanks containing fuel oil, lubricating
oil or other flammable liquid, failure of such means or over filling
of the tank should not result in the release of tank contents.
10.10.7 For
a normally inaccessible small void compartment, such as an echo sounding
compartment, which is accessed from within a normally inaccessible
space such as a forepeak tank, alternative sounding arrangements to
those required by Vol 2, Pt 7, Ch 2, 10.10 Sounding arrangements 10.10.1 may
be considered. For such arrangements, a warning notice is to be located
in a prominent position specifying precautions to be taken prior to
opening the manhole of the small void compartment. Means are to be
provided to indicate flooding of the compartment without opening,
such as fitting indicator plugs to the manhole. Sounding arrangements
are to be submitted to LR for approval.
10.11 Termination of sounding pipes
10.11.1 Sounding
pipes are to be led to positions above the assumed damage waterline
which are at all times accessible and, in the case of fuel oil tanks,
refuelling oil tanks, lubricating oil tanks and tanks containing other
flammable oils, the sounding pipes are to be led to safe positions
on the open deck.
10.12 Short sounding pipes
10.12.1 In
machinery spaces and tunnels, in circumstances where it is not practicable
to extend the sounding pipes as mentioned in Vol 2, Pt 7, Ch 2, 10.11 Termination of sounding pipes, short sounding pipes extending
to well lighted readily accessible positions above the platform may
be fitted to double bottom tanks. Where such pipes serve tanks containing
fuel oil or other flammable liquid, an additional sounding device
of approved type is to be fitted. An additional sounding device is
not required for lubricating oil tanks. Any proposal to terminate
in the machinery space, sounding pipes to tanks, other than double
bottom tanks, will be the subject of special consideration.
10.12.2 Short
sounding pipes to fuel oil and lubricating oil tanks, and other flammable
oil tanks (flash point not less than 60°C) are to be fitted with
cocks having parallel plugs with permanently attached handles, so
loaded that, on being released, they automatically close the cocks.
In addition, a small diameter self-closing test cock is to be fitted
below the cock mentioned above in order to ensure that the sounding
pipe is not under a pressure of oil before opening up the sounding
cock. Provision is to be made to ensure that discharge of oil through
this test cock does not present an ignition hazard. An additional
small diameter self-closing test cock is not required for lubricating
oil tanks.
10.12.3 As
a further precaution against fire, such sounding pipes are to be located
in positions as far removed as possible from any heated surface or
electrical equipment and, where necessary, effective shielding is
to be provided in way of such surfaces and/or equipment.
10.12.5 Where
a double bottom is not required to be fitted, short sounding pipes
to tanks other than oil tanks are to be fitted with shut-off cocks
or with screw caps attached to the pipes by chains.
10.13 Elbow sounding pipes
10.13.1 Elbow
sounding pipes are not to be used for deep tanks unless the elbows
and pipes are situated within closed cofferdams or within tanks containing
similar liquids. They may, however, be fitted to other tanks and may
be used for sounding bilges, provided that it is not practicable to
lead them direct to the tanks or compartments, and subject to any
sub-division and damage stability requirements that may apply, see
Vol 2, Pt 7, Ch 2, 1.3 Prevention of progressive flooding in damage condition 1.3.1.
10.13.2 The
elbows are to be of heavy construction and adequately supported.
10.14 Striking plates
10.14.1 Striking
plates of adequate thickness and size are to be fitted under open
ended sounding pipes.
10.14.2 Where
slotted sounding pipes having closed ends are employed, the closing
plugs are to be of substantial construction.
10.15 Size of sounding pipes
10.15.1 Sounding
pipes are to be not less than 32 mm bore.
10.15.2 All
sounding pipes, whether for compartments or tanks, which pass through
refrigerated spaces or the insulation thereof, in which the temperatures
contemplated are 0°C or below, are to be not less than 65 mm bore.
10.16
CROSS-REFERENCES
10.16.1 For ‘Ice Class’ requirements, see
Vol 3, Pt 1, Ch 1 Ice Navigation - First-Year Ice Conditions.
For control engineering equipment, see
Vol 2, Pt 9, Ch 7 Control, Alerts and Safety Systems.
For requirements
relating to scuppers and sanitary discharges, see
Vol 1, Pt 3, Ch 4 Closing Arrangements and Outfit.
|