Section
11 Air, overflow and sounding pipes
11.1 Air pipes
11.1.1 Air
pipes are to be fitted to all tanks, cofferdams, tunnels and other
compartments which are not fitted with alternative ventilation arrangements.
11.1.2 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, special consideration
will be given to the number and position of the air pipes.
11.1.4 Air
pipes to fuel oil tanks serving emergency generators may not be led
through Category ‘A’ machinery spaces.
11.1.5 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 11.1.1 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.
11.2 Termination of air pipes
11.2.1 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
watertight deck. Air pipes to fuel oil tanks, cofferdams and all tanks
which can be pumped up are to be led to the open.
11.2.2 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.
11.2.3 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.
11.2.4 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 rainwater.
11.3 Gauze diaphragms
11.3.1 The
open ends of air pipes to fuel oil tanks are to be fitted with a wire
gauze diaphragm of non-corrodible material which can be readily removed
for cleaning or renewal.
11.3.2 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
Pt 15, Ch 2, 11.6 Size of air pipes.
11.4 Air pipe closing appliances
11.4.1 The closing appliances fitted to tank air pipes, in accordance with Pt 3, Ch 4, 12 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.
11.4.3 Wood
plugs and other devices which can be secured closed are not to be
fitted at the outlets.
11.4.5 Air
pipe automatic closing devices shall be constructed to allow inspection
of the closure and the inside of the casing, as well as changing
the seals.
11.4.6 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.
11.4.7 Air
pipe automatic closing devices are to be self-draining.
11.4.8 The
clear area through an air pipe closing device in the open position
shall be at least equal to the area of the inlet.
11.4.10 The
maximum allowable tolerances for wall thickness of floats should
not exceed ±10 per cent of thickness.
11.4.11 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 inPt 15, Ch 2, 11.4 Air pipe closing appliances 11.4.1,
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.
11.4.12 Casings
of air pipe closing devices are to be of approved metallic materials
adequately protected against corrosion.
11.4.13 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.
11.4.14 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, for example 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.
11.4.15 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.
11.5 Nameplates
11.5.1 Nameplates
are to be affixed to the upper ends of all air and sounding pipes.
11.6 Size of air pipes
11.6.1 For
every tank which can be filled by on-board pumps, the total cross-sectional
area of the air pipes and the air pipe closing devices is to be such
that when the tank is overflowing at the maximum pumping capacity
available for the tank, it will not be subjected to a pressure greater
than that for which it is designed.
11.6.2 In all
cases, whether a tank is filled by on-board pumps or other means,
the total cross-sectional area of the pipes is to be not less than
25 per cent greater than the effective area of the respective filling
pipe.
11.6.3 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.
11.7 Overflow pipes
11.7.1 For
all tanks which can be pumped up, overflow pipes are to be fitted
where:
-
The total cross-sectional area of the air
pipes is less than that required by Pt 15, Ch 2, 11.6 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.
11.7.2 In the
case of fuel oil tanks, lubricating oil tanks and other 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 is to be provided to indicate
when overflowing is occurring.
11.7.3 Overflow
pipes are to be self draining under normal conditions of trim.
11.7.4 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 be adequately
protected from mechanical damage. Overflow sight glasses are not permitted
in fuel oil systems for craft required to comply with the HSC Code.
11.8 Combined air and overflow systems
11.8.1 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 in the maximum
assumed damage condition.
11.8.2 Where tanks vent via a common tank, such as an overflow tank, extending to
the shell plating, flooding of this tank as a result of damage to the shell plating is
not to render the entire venting system inoperable.
11.8.3 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.
11.9 Sounding arrangements
11.9.1 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.
11.9.2 Sounding
devices of an approved type (i.e. level gauge or remote reading level
device) may be used in lieu of sounding pipes.
11.9.3 Bilges
of compartments which are not at all times readily accessible are
to be provided with sounding pipes.
11.9.4 Where
fitted, sounding pipes are to be as straight as practicable, and if
curved to suit the structure of the craft, the curvature is to be
sufficiently easy to permit the ready passage of the sounding rod
or chain.
11.9.5 Striking
plates of adequate thickness and size are to be fitted under open
ended sounding pipes.
11.9.6 Where
slotted sounding pipes having closed ends are employed, the closing
plugs are to be of substantial construction.
11.9.7 Sounding
pipes are to be not less than 32 mm bore.
11.9.8 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 Pt 15, Ch 2, 11.9 Sounding arrangements 11.9.1 may
be considered. For such arrangements, a warning notice is to be located
in a prominent position specifying precautions to be taken prior 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.
11.10 Termination of sounding pipes
11.10.1 Except
as permitted by Pt 15, Ch 2, 11.11 Short sounding pipes, sounding
pipes are to be led to positions above the bulkhead deck which are
at all times accessible and, in the case of fuel oil tanks, cargo
oil tanks and lubricating oil tanks, the sounding pipes are to be
led to safe positions on the open deck.
11.11 Short sounding pipes
11.11.1 In
machinery spaces, where it is not practicable to extend sounding pipes,
as mentioned in Pt 15, Ch 2, 11.10 Termination of sounding pipes, short
sounding pipes extending to readily accessible positions above the
platform may be fitted.
11.11.3 Short
sounding pipes may be fitted to tanks used for the storage, distribution
and utilisation of lubricating oil in machinery spaces. These sounding
pipes are to be fitted with cocks having parallel plugs with permanently
attached handles, located such that, on being released, they automatically
close the cocks.
11.12 Elbow sounding pipes
11.12.1 In
passenger craft, elbow sounding pipes are not permitted.
11.12.2 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
subdivision and damage stability requirements that may apply.
11.12.3 The
elbows are to be of heavy construction and adequately supported.
11.13 Sounding arrangements for fuel oil, lubricating oil and other
flammable liquids
11.13.1 Safe
and efficient means of ascertaining the amount of oil in any storage
tank are to be provided.
11.13.2 For
fuel oil, lubricating oil and other flammable liquids, closed sounding
devices are preferred. Design details of such devices are to be submitted
and they are to be tested after fitting on board, to the satisfaction
of the Surveyors.
11.13.3 If
closed sounding devices are fitted, failure of the device or over
filling of the tank is not to result in the release of tank contents.
In passenger craft and yachts that are 500 gt or more, such means
are not to require penetration below the top of the tank.
11.13.4 Where
sounding pipes are used they are not to terminate in any space where
risk of ignition or spillage from the sounding pipe might arise. In
particular they are not to terminate in public spaces or crew accommodation.
Additionally for fuel oil tanks they are not to terminate in machinery
spaces. Terminations are to be provided with a suitable means of closure
and provision to prevent spillage during refuelling/refilling operations.
11.13.5 Where
gauge glasses are used they 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.
11.13.6 In
yachts and service craft which are not required to comply with the
HSC Code, short sounding pipes extending to well-lighted, readily
accessible positions above the platform may be fitted in machinery
spaces and tunnels. Sounding pipes are to be fitted with cocks having
parallel plugs with permanently attached handles located such that,
on being released, they automatically close the cocks.
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