FREEBOARD ASSIGNMENT

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Nov 15, 2013 (3 years and 8 months ago)

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FREEBOARD
ASSIGNMENT


LOADLINES RULES

INTRODUCTION

All ships (with certain exceptions) are
required to be surveyed and marked with
permanent load line markings in accordance
with the International Convention on Load
Lines, 1966 as modified 1988. The principle
purpose of load line assignment is to ensure
that the ship always has sufficient reserve
buoyancy and intact stability when
proceeding to sea.

International Convention on Load
Lines

is an International Convention
on

Load Lines

(CLL), signed in London on
5 April 1966, amended by the 1988
Protocol and further revised in 2003. The
1988 Protocol was adopted in order to
harmonize the survey and certification
requirement of the 1966 Convention
with those contained in the

International
Convention for the Safety of Life at
Sea
(SOLAS) and MARPOL 73/78.


This Convention provides for the
terms of ship's surveys,
issuance
,
duration
, validity and acceptance of
International Load Line Certificates
,
as well as
relevant State control
measures
,
agreed exemptions and
exceptions.


Annexes to the Convention contain
various regulations for
determining
load lines
, including details of
marking
and verification of marks
,
conditions
of assignment of freeboard
,
freeboard
tables and corrections
,
special
provisions for ships intended for the
carriage of timber

and the
prescribed
form of International Load Line
Certificates.


also taken into account are the
potential hazards present in different
zones and different seasons

and
additional safety measures concerning
doors, hatchways etc.


The following ships are not required
to have load lines assigned:

* warships;

* new ships of less than 24 metres in
length;

* existing ships of less than 150 tons
gross;

* pleasure yachts not engaged in
trade, and;

* fishing vessels.

(Annex A


Article 5)

* Reserve buoyancy

* Water on deck

* Not overloaded (Hull markings)

* Maintain Conditions (Inspections)


Purpose of F/B assignment

Conditionof F/B assignment

* Stability

* Strength of Hull

* Water/ Weather tightness

* Protection of crew


*

Dimensions and form of the ship

* Means of freeing water on deck

* Means of closing/opening (doors/sills)

* Structural strength (hull, deckhouse,
hatches)

* Hull penetrations ( piping inlets &
discharges)

* Cargoes (oil, timber, GC)

* routes, weather and seas likely to be
found



Consideration for F/B assignment

The seasonal zones, areas and periods
that determine the appropriate load
line in a particular sea area at a given
time of year are set out in Annex II

The Tropical, Summer and Winter
freeboard zones are based upon the
following weather criteria:


Summer Zones


Regions where not
more than 10% of wind speeds exceed
force 8 Beaufort (34 knots).

Tropical Zones


Regions where not
more than 1% of wind speeds exceed
force 8 Beaufort (34 knots) and not
more than one tropical storm in a ten
-
year period occurs in an area of 5º

latitude/longitude square in any one
separate calendar month.


Winter Zones


Are all other regions

It is a criminal offence for the Master
and/or shipowner to allow a vessel
to be operated in a zone, when in the
upright condition, the relevant
amidships zone load line would be
below the still load waterline. Such
an action would immediately
invalidate all Classification Society
and Load Line

certification and will
lead to criminal prosecution
.

DEFINITIONS

Length (L)

This is taken as 96% of the total length
on a waterline at 85% of the least
moulded depth, or, as the length from
the fore side of the stem to the axis of
the rudder stock on that waterline, if
greater.

Perpendiculars (FP, AP)

is a line drawn perpendicularly to the
load line through the after side of the
rudder post or through the axis of the
rudder stock. T

Amidships

Amidships is at the middle of the length

(L).


Breadth (B)

Unless expressly provided otherwise, the
breadth (B) is the maximum breadth of
the ship, measured amidships to the
moulded line of the frame in a ship with a
metal shell and to the outer surface of
the hull in a ship with a shell of any other
material.

Moulded depth

is the height above baseline of the
intersection of the underside of the
deck plate with the ship side.

When there are several decks, it is
necessary to specify to which one
refers the depth.

Depth for freeboard (D)

This is the
moulded

depth amidships, plus the
thickness of the freeboard deck stringer plate,
where fitted, plus T(L


S)/L if the exposed
freeboard deck is sheathed, where:

T is the mean thickness of the exposed sheathing
clear of deck openings, and S is the total length of
superstructures.

The depth for freeboard (D) in a ship having a
rounded gunwale with a radius

greater than 4%
of the breadth (B) or having topsides of unusual
form is the depth for freeboard of a ship having a

midship

section with vertical topsides and with
the same round of beam and area of topside
section equal to that provided by the actual
midship

section.

Block Coefficient (
Cb
)


Cb

= Volume of displacement at
draught 0.85D/ ((Length*
´

Breadth*
´

draught (at 85% of least
moulded

depth))

(* as previously defined)

(in no case shall the block coefficient
(
Cb
) be taken to be less than 0.68.)

Freeboard

The freeboard assigned is the distance
measured vertically downwards
amidships from the upper edge of the
deck line to the upper edge of the
related load line.

Freeboard Deck

This is normally the uppermost
continuous deck exposed to weather
and sea, which has permanent means
of closing all openings in the weather
part thereof, and below which all
openings in the sides of the ship are
fitted with permanent means of
watertight arrangement.

Deck line

The deck line is a horizontal line marked

amidships on each side of the ship.
Its upper

edge shall normally pass through the point

where the continuation outwards of the upper

surface of the freeboard deck intersects the

outer surface of the shell plating.

However, the deck line may be placed with

reference to another fixed point on the ship on
condition that the freeboard is correspondingly
corrected and that the reference point location
and the identification of the freeboard deck is
clearly indicated on the International Load Line
Certificate.

Load line mark and accompanying
load lines (Regulations 5 to 8)

The Load Line Mark consists of a ring 300
mm in outside diameter and 25 mm thick
which is intersected by a horizontal line
450 mm in length and 25 mm thick, the
upper edge of which passes through the
centre of the ring. The centre of the ring is
placed amidships and at a distance equal
to the assigned summer freeboard
measured vertically below the upper edge
of the deck line.

Conditions

of
assignment

of
freeboard


1. Information to the master.


Master to be supplied information for the
loading and ballasting of the ship avoiding
unacceptable stresses of the ship’s
structure.

Also, to be provided with ship’s stability
guidance for all condition of service.

2. Superstructure end bulkheads

3. Doors

4. Position of hatchways, doorways
and ventilators

5. Cargo and other hatchways

6. Hatchways closed by portable
covers and secured by tarpaulins ..

7. Hatchways closed by weathertight
covers of steel …

8. Machinery space openings

9. Miscellaneous openings in
freeboard and superstructure decks

10. Ventilators

11.
Air pipes

12. Cargo ports and other similar
openings

13. Scuppers, inlets and discharges

14.
Sidescuttles

15. Freeing ports

16. Protection of the crew

Types of ships

Type “A” ships



Tankers, tank barges, & similar designs,
only to carry liquid cargoes in bulk




High integrity of exposed deck, cargo
tanks with only small access openings
closed by watertight gasketed steel (or
equivalent) covers




Low permeability of loaded cargo tanks

Type "B" ships

Ships that are not
Type A

Type B ships are assigned bigger
freeboards (less favourable).

However, certain Type "B" ships may
qualify for reduced freeboards (more
favourable).

Type "B reductions
:

(B


60; B


100)

If L > 100 m, loaded, will be afloat after
flooding of any compartment/s, excluding
the machinery spaces

If L > 150 m, same, but including machinery
spaces

In such cases, freeboard. may be reduced up
to 60% of the difference between Type " A "
and Type “B” freeboards

Under certain conditions, the Freeboard may
be reduced up to 100% of the difference
between Type " A " and Type “B” freeboards

Freeboard tables.

For Type A and Type B ships
(Entering with Length)

Length of ships (meters)

Freeboard (mm)

100

1271

101

1293

102

1315

103

1337

Corrections to the
tabular Freeboards


Length: If 24 < L < 100 m, for type B ships,
freeboard may be increased.

Block coefficient: If Cb

> 0.68, the freeboard
must be increased (less favourable)

Depth: If D > L/15, more draught, freeboard
increased



If D < L/15, freeboard may be
reduced (subject to conditions).

Superstructure:
Superstructure can
provide additional righting energy during

extreme rolls where deck edge is
immersed. Freeboard may be reduced if the
superstructure meets certain requirements.

Trunks:
Deckhouses which are < 92% of
beam are trunks, not superstructures”

A trunk is


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Sheer: The deck sheer provides more
buoyancy at bow & stem (i.e., pitching

response), reduces deck wetness; Ships
with a particular sheer profiles may have
its freeboard reduced or increased


Bow Height:

Ships must have a
minimum bow height (to ensure reserve
buoyancy at bow). Ships with smaller bow
height have its freeboard increased, but
no freeboard reduction is given for
excessive bow height.

Minimum freeboards


Minimum
Freeboards

Obtained by:

SUMMER (S)

Tables (reg 28) modified by
the corrections (regs 29


39)

TROPICAL (T)

Summer freeboard less
Summer Draught / 48

WINTER (W)

Summer freeboard plus
Summer Draught / 48

WINTER N.A.
(WNA)

Only for ships of L


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Winter freeboard plus 50 mm.

Preparation For A Load
Line Survey


Ensure particulars in the conditions
of assignment of L/L have been
incorporated into the
Planned
Maintenance schedule.

The detailed preparations should
commence
three months
before the
expected date of survey.

1. Check that all access openings
at ends of enclosed structures are
in good condition. All dogs, clamps
and hinges should be free and well
greased. All gaskets and water
tight seals should be crack free.
Ensure that the doors open from
both sides.


2. Check all cargo hatches and access
to holds for water tightness
especially battening devices such as
cleats and wedges.


3. Inspect all
machinery space
openings

on exposed decks.

4. Check that any
manholes and flush
scuttles
are capable of being made
water
-
tight.

5. Check that all
ventilator openings
are provided with efficient weather
-
tight closing appliances and repair any
defects.


6. All
airpipes

must be provided with
permanently attached satisfactory
means for closing openings.

7. Inspect any
cargo ports below the
freeboard deck

and ensure that all
of them are watertight.

8. Ensure that the
non return valves
on board discharge
are operating in
a satisfactory manner.


9.
Side scuttles below the freeboard
deck
or to spaces within enclosed
superstructures must have efficient
internal watertight deadlights. Inspect
the deadlight ‘rubbers’.

10. Check that all
freeing ports
are in a
satisfactory condition e.g. shutters are
not jammed, hinges are free and that
pins are of non corroding material.

11. All
guard rails
and bulwarks
should be in satisfactory condition,
e.g. all fractured rails should be re
-
welded.

12. If the
life lines
are required to be
fitted in certain areas, rig the lines
and overhaul as necessary.


13. De
-
rust and paint the
deck line,
load line mark, load lines and the
draught marks.

In brief ensure that the hull is
water
-
tight below the freeboard
deck and watertight above the
freeboard deck.


14. On the day of the survey have
the certificate and record ready for
the surveyor’s inspection.

15. The master should have
sufficient stability information to
show that the vessel can be loaded
and ballasted correctly. ( If having
approved loading computer
program, print out test pages to
submit to surveyor)

16. Have all the necessary
key
to
areas which surveyor may want to
inspect e.g. store rooms

17. Sufficient men should be
available for work such as opening
cargo hatches, and ladders and
stages should be ready for the
surveyors to view the load line
marks.