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INTERNATIONAl MARITIME ORGANIZATION
4 AlBERT EMBANKMENT
lONDON SE1 7SR
Telephone:
Fax:
Telex:
0171-735 7611
0171-587 3210
235B8 IMOLDN G
(M)
MSC/Circ.811
8 July 1997
" ys
IMO
Ref. Tl/3.02
IDENTIFICATION OF FLOAT-FREE ARRANGEMENTS FOR LIFERAFTS
1
The Maritime Safety Committee, at its sixty-eighth session (28 May to 6 June 1997), noted that
there were three systems used in float-free arrangements, i.e. the external weak link system, the internal
weak link system and the non-weak link system (see examples at annex). Because of this, compliance
of any ofthe three systems with SOLAS regulation III/38.6.1 (section 4.1.6 of the LSA Code) could not
be easily verified and this might cause difficulties, particularly to port State control officers.
The Committee, therefore, recommended that inflatable liferafts using internal or weak link
2
systems should be marked on the outside of the container with appropriate wording or pictograms
indicating the system used for the float-free arrangement.
3
Member Governments. are invited to bring the above recommendation and the annex thereto to
the attention of shipowners, shipping companies, liferaft manufacturers, liferaft servicing stations and all
othem involved in the manufacture, installation and servicing of inflatable liferafts, as well as port State
control officers.
***
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MSC/Circ. 811
ANNEX
THREE SYSTEMS USED IN FLOAT-FREE ARRANGEMENTS
The following three systems are offered as an example of those used in float-free arrangements
(see also figures 1 to 5 below).
1
Internal weak links system
1.1
Automatic •·elease mechanism
When the ship sinks, the hydrostatic release unit actuates at a depth of 2 to 4 m and disconnects the
lashing wire from the cradle, and the container floats to the surface of the water.
At this time, the operating line fastened to the cradle is pulled and inflation of liferaft is started. And, at
the same time, supplementary painters come loose from the cradle because the end of the painter is
attached to the cradle with a fine thread and detached easily by being pulled. Finally, a safety belt (same
concepts as weak link but has a breaking strength of70 to 100 kgf) breaks, so the liferaft is released from
the sinking ship and floats to the surface.
1.2
Manual drop mechanism
The end ofthe supplementary painter is detached from the painter indication plate and tied to the cradle
by hand. And the hydrostatic release unit is released manually. The container drops from the cradle
rolling and pulls the operating line so the liferaft reaches the surface of the water while inflating. At this
time, the liferaft is tied to the ship by the painter and the supplementary painter.
2
Non-weak link system
2.1
Automatic release mechanism
When the ship sinks, the hydrostatic release unit actuates at a depth of 2 to 4 m and disconnects the
lashing wire and painter from the cradle, and the container floats to the surface of the water. At this time,
the operating line fastened to the cradle is pulled and inflation of liferaft is started. The raft is released
from the sinking ship and floats to the surface. With this mechanism, the painter and operating line are
separate, so there is no need to provide a weak link.
2.2
Manual drop mechanism
When the release handle (located on the cradle) is pulled, one end of the lashing wire is disconnected
while the other end of the wire is connected to the hydrostatic release unit, the container drops from the
cradle rolling and pulls the operating line so the liferaft reaches the surface of the water while inflating.
At this time the liferaft is tied to the ship by the painter.
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MSC/Circ. 811
ANNEX
Page2
3
Extemal weak link system
3.1
Automatic release mechanism
When the ship sinks, the hydrostatic release unit actuates at a depth of 2 to 4 m and disconnects the
lashing wire from the cradle, and the container floats to the surface of the water. At this time, the
operating line tied to the painter is pulled and inflation of the liferaft is started. Next, a weak link fastened
to the cradle breaks, so the liferaft is released from the sinking ship and floats to the surface.
3.2
Manual drop mechanism
When the release handle (located on the cradle) is pulled, the lashing wire is disconnected while the other
end ofthe wire is connected to the hydrostatic release unit. The container drops from the cradle rolling
and pulls the operating line so the liferaft reaches the surface of the water while inflating. At this time,
the liferaft is tied to the ship by the painter.
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MSC/Circ.Sll
ANNEX
Page 3
[FIGURE 1]
·1. •
F 1 o a t ­ ·t r c ·c
arrangements
INTERNAL WEAK LINK SYSTEM
f o r
SUPPLEHrNT~Rt
fcratt
CR~DL&
J:"Al:H'l'ER
li:"Al:HTER
CYLlltDER VALVE­
OPElt\TIJ«i LIME
'PAl:HT.2R
IHDl:CAIOH'
PLAT£
NON WEAK LINK SYSTEM
.J.IOOK FOR PAlHT£R
lllDKCSTAfiC
REW.SI! mllr
><;::;?>=.lf:::::!:;'AliHCll SHAFT
r'AIHT&R
EXTERNAL WEAK LINK SYSTEM
CRADL&
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l
MSC/Circ.Sll
ANNEX
Page4
(F!GURE2]
2 ..
S t r u c tore
o f
s towage
c r ad I e
INTERNAL WEAK LINK SYSTEM
FRP container""
'1\im buckle
Supplementary painter
· ()pe.nti.ng line
Supplementary
"""''"
1'\..
Painter lndic.ation
plate lii:Sh.ln~ cord
Pointer lndlcatioo
d•te
Detail cl C
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~ton
~taU
·
ol
A~on
MSC/Circ. 811
ANNEX
Page 5
[flGURE3]
NON WEAK LINK SYSTEM
Containec lashing
wi~lb.inr ~
Lashing wire
Side defense
llrdrostatlc releue unit
~~~e
Painter
Rele=! h411dle
Salety pin
Detail of £1
Tum
Painter
1ri\1\--­
Hrdroslalit
release unll
Detail of A
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MSC/Circ. 811
ANNEX
Page6
[FIGURE4]
EXTERNAL WEAK LINK SYSTEM(fiBER ROPE TYPE)
Painter
Container lashina­
-Mre fWnr ~ .. llrdrostallc
·release Unil
CMSK-lJOB)
(FIGURES]
EXTERNAL WEAK UNK SYSTEM (STEEL WIRE TYPE)
Contaitlc:r I&Shlnll
win: fu.inr bU .
FRP oonui n~:r
reat 1iRk
Painter
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