Section
2 Timber deck cargoes
2.1 Application
2.1.3 Attention is drawn to the International Load Line Convention, 1966, and its 1988
Protocol, with respect to requirements for ships assigned a timber loadline.
2.2 Symbols and definitions
2.2.1 The
term `timber deck cargo' means a cargo of timber carried on an uncovered
part of the freeboard or superstructure deck. The term does not include
wood pulp or similar cargo.
2.2.2 The
symbols used in this Section are defined as follows:
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C
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= |
mean
stowage rate, in m3/tonne, of the timber deck cargo, making
allowance for normal battens, etc.
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h
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= |
the
height, in metres, to which the timber deck cargo is to be stowed,
measured vertically from the deck or hatch cover as applicable. |
2.3 General
2.3.1 Attention is drawn to the requirements of the International Convention
for the Safety of Life at Sea, 1974, Chapter VI, as amended, the International
Load Line Convention, 1966, concerning timber deck cargoes, and its 1988
Protocol, and to National Regulations.
2.3.3 Each
cargo securing arrangement for timber deck cargoes detailed in the
ship’s Cargo Securing Manual is to be documented by a lashing
plan that shows the following:
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maximum cargo
weight for which the arrangement is designed;
-
maximum stowage
height;
-
required number and strength of blocking devices, lashings, uprights
and loose gear, as applicable;
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required pre-tension
in lashings;
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other cargo properties
of importance for the securing arrangement, such as friction, rigidity
of timber packages;
-
illustrations
of all securing items that might be used;
-
any restrictions
regarding maximum accelerations, weather criteria, restricted sea
areas and for non-winter conditions only;
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the walkway/life-line
arrangements; and
-
lashing and stowage arrangements, which are to be in accordance with
Pt 3, Ch 9, 2.6 Lashings and Pt 3, Ch 9, 2.7 Stowage .
2.3.4 All timber deck cargoes must be compactly stowed, lashed and secured.
Friction alone is not deemed sufficient and such methods are not endorsed by Clasifications
Register. Loop lashing is recommended where applicable as one of the safest practices
for securing timber deck cargoes.
2.3.5 Timber
freeboards cannot be used where wood pulp is being carried as the
deck cargo. Packaged timber (timber which has been prelashed) may
be carried on deck with the ship at its timber freeboards.
2.3.6 Type
`B−60' ships may have timber freeboards assigned based on ordinary
Type `B' freeboards.
2.3.7 Timber
freeboards are not appropriate for ships which are assigned freeboards
from a second deck. However, where the maximum geometric upper deck
draught is restricted, a restricted timber draught may be assigned.
2.3.8 It is
the Master’s responsibility to ensure loose gear (e.g. uprights,
wire lashings and life-lines) are supplied and fitted onboard in accordance
with the approved timber deck cargo loading and lashing plan when
the ship is carrying timber deck cargoes. However, it is not a requirement
that loose gear remains permanently on board a ship assigned timber
freeboards.
2.4 Arrangements
2.4.1 Double
bottom tanks within the midship half-length are to have adequate longitudinal
subdivision.
2.4.2 A forecastle
of at least standard height of a superstructure, defined by Regulation
33 of the International Load Line Convention, as amended, and of length
at least 0,07L is to be fitted. In addition, in ships
of less than 100 m in length, a poop of at least standard height,
or a raised quarterdeck with a deckhouse or strong steel hood of at
least the same total height, is to be fitted.
2.5 Uprights
2.5.2 Uprights
are to be used for all timber deck cargoes with the exception that,
where only packaged timber is to be carried, uprights may be omitted,
depending on racking strength and not including uprights or stoppers
(low uprights) situated either side of hatch covers.
2.5.3 Strong permanent bulwarks, or efficient rails of specially strong
construction, are to be fitted. They are acceptable as supports for uprights, provided
they have adequate strength, and substantial sockets are built for each upright.
2.5.4 Deck sockets, along with locking pin, are to be of adequate strength to hold
the uprights in place. They are to be efficiently connected to the hull structure to
transfer the loads. They are not to be less than 100 mm in depth with drainage provided.
A locking pin or wedge is to be provided to prevent the upright lifting out of the
socket.
2.6 Lashings
2.6.1 The timber deck cargo is to be secured along its length by appropriate
top-over lashings or loop lashings of adequate strength.
2.6.2 The spacing of lashings is to be such that lashings are positioned as close as
practicable to the ends of each continuous timber deck stow.
2.6.3 In order to achieve a more secure stowage of logs when stowed on deck, hog
wires are to be utilised. Such hog wires shall be installed in the following manner so
as to obtain as even a tension as possible throughout, thus producing an inboard pull on
the respective uprights:
- At approximately three quarters of the height of the stow, the hog wire should be
rove through a pad eye attached to the uprights at this level so as to run
transversely, connecting the respective port and starboard uprights. The hog
lashing wire should not be too tight when laid, so that it becomes taut, when
overstowed with other logs.
- A second hog wire may be applied in a similar manner, if the height of the hatch
cover is less than 2 m. Such second hog wire should be installed approximately 1 m
above the hatch covers.
2.6.4 Where only packaged timber is to be carried, and uprights are omitted,
see
Pt 3, Ch 9, 2.5 Uprights 2.5.2, lashings are to be spaced not more than 1,5 m apart.
2.6.5 Eye plates used for lashing are to be of substantial construction and adequate strength.
They are to be effectively connected to the hull structure, and placed at intervals
appropriate for the lashing arrangement. The distance from a superstructure or deckhouse
end bulkhead to the first eye plate and lashing is to be not more than 2 m.
2.6.6 Open hooks, which may loosen if the lashing becomes slack, are not to be
used in securing arrangements for timber deck cargoes, and web lashing is not to be used
in combination with chain or wire lashing.
2.6.7 Slip hooks or other appropriate methods may be used for quick and safe
adjustment of lashings. Pelican hooks, when used, are to be moused.
2.6.8 Corner protectors are to be used to prevent lashings from cutting into the cargo and to
protect lashings from damage at sharp corners.
2.6.9 Lashings and fittings must have adequate strength for the proposed timber loading and
must not:
- Have a breaking strength of less than 133 kN;
- Elongate more than 5 per cent at 80 per cent of the breaking strength
and;
- Show any permanent deformation at less than 40 percent of the breaking
strength.
2.6.10 Every lashing is to be provided with a tightening device or system, situated so that it
can be safely and efficiently operated when required. The magnitude of the components of
the resolved load produced by the tightening device or system is not to be less than:
- 27 kN in the horizontal direction; and
- 16 kN in the vertical direction.
2.6.11 Once the lashings are secured, the tightening device or system is to have
not less than half the tightening capacity available for further use.
2.6.12 If wire rope clips are used to make a joint in a wire lashing, the following conditions
are to be observed to avoid a significant reduction in strength:
- at least three rope clips are to be utilised to make a wire joint, where the
total number and size of the rope clips utilised are to be in proportion to the
diameter of the wire rope used. The rope clips are to be spaced not less than 150
mm apart;
- the saddle portion of the clip is to be applied to the live load segment;
and
- rope clips are to be initially tightened so that they visibly compress the wire
rope and are subsequently to be re-tightened after the lashing has been
stressed.
2.6.13 Bulldog grips are only suitable for a standard wire rope of right-hand lay having six
strands. Such grips are not to be used for wire rope of left-hand lay or different
construction.
2.6.14 Where loose or packaged sawn wood is carried, Pt 3, Ch 9, 2.6 Lashings 2.6.15 to 2.6.18, and in case of logs, poles, cants or similar
cargo, Pt 3, Ch 9, 2.6 Lashings 2.6.19 to Pt 3, Ch 9, 2.6 Lashings 2.6.20, are to be complied with.
2.6.15 Subject to Pt 3, Ch 9, 2.6 Lashings 2.6.16, the maximum spacing of the lashings referred to above
should be determined by the maximum height of the timber deck cargo in the vicinity of
the lashings:
- for a height of 2,5 m and below, the maximum spacing is to be not
more than 3 m;
- for heights of above 2,5 m, the spacing is to be not more than 1,5
m;
- on the foremost and aft-most sections of the deck cargo, the
distance between the lashings in accordance with (a) and (b) are to be
halved.
2.6.16 As far as practicable, long and sturdy packages should be stowed in the outer rows of
the stow, and the packages stowed at the upper outboard edge should be secured by at
least two lashings each.
2.6.17 When the outboard packages of the timber deck cargo are in lengths of less than 3.6 m,
the spacing of the lashings should be reduced as necessary, or other suitable provisions
made to suit the length of timber.
2.6.18 Rounded angle pieces of suitable material and design are to be used along the upper
outboard edge of the stow to bear the stress and permit free reeving of the
lashings.
2.6.19 Round wood deck cargo should be supported by uprights and secured throughout its length
by independent top-over or loop lashings spaced not more than 1,5 m apart.
2.7 Stowage
2.7.2 Timber
deck cargoes are to extend over at least the entire available length,
which is the total length of the well or wells between superstructures.
Where there is no limiting superstructure at the after end, the timber
is to extend at least to the after end of the aftermost hatchway.
2.7.3 The
timber deck cargo is to extend athwartships as close as possible to
the ship’s side, due allowance being made for obstructions,
provided any gap thus created at the side of the ship does not exceed
a mean of four per cent of the breadth.
2.7.4 The
timber is to be stowed as solidly as possible to at least the standard
height of a superstructure other than a raised quarter deck. It is
not to interfere in any way with the safe navigation and necessary
work of the ship.
2.7.5 On a
ship within a seasonal winter zone in winter, the height of the deck
cargo above the deck exposed to weather must not exceed one third
of the extreme breadth of the ship.
2.7.6 Cargo
which overhangs hatch coamings or other structures in the longitudinal
direction by more than a third of their individual or packed length
is to be supported at the outer end by other cargo stowed on deck
or by structure of adequate strength.
2.8 Safety arrangements
2.8.1 If there
is no convenient passage on or below the deck of the ship, a walkway
is to be provided over the timber deck cargo. This walkway is either
to be:
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At, or near, the
centreline of the ship, consisting of two sets of guard wires, spaced
1 m apart, each with more than three courses of wire. The opening
below the lowest course is not to exceed 230 mm; the remaining courses
are to be spaced not more than 380 mm apart to a height of at least
1 m above the timber deck cargo. The guard wires are to be secured
to stanchions. The stanchions are to be not more than 3 m apart, and
these are to be secured to the timber cargo by spikes, or other equivalent
means.
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Alternatively,
where uprights are used, guard wires, spaced vertically not more than
330 mm apart, are to be secured to the uprights along the length of
the timber deck cargo on both port and starboard sides to a height
of not less than 1 m above the cargo. A wire life-line is also to
be fitted at the centreline of the ship, adequately supported by stanchions
spaced not more than 10 m apart.
A safe walking surface,
not less than 600 mm in width, is to be fitted over the cargo and
effectively secured to the top of it in line with the walkway or adjacent
to the life-line. All lines are to be taut using tightening devices.
2.8.2 Safe
access is to be provided to the top of the timber deck cargo by means
of properly constructed ladders, steps or ramps fitted with guard
lines or handrails.
2.8.3 All
openings in the weather deck are to be capable of being properly closed
and secured tight. Ventilators, air pipes and other fittings enclosing
openings are to be efficiently protected against damage.
2.8.4 Access
hatches, vents, air pipes, fire hydrants, hoses, valve operating positions,
sounding pipes and other essential equipment are to be clearly marked
and left accessible.
2.9 Longitudinal strength
2.9.1 The
proposed timber deck loading conditions are to be taken into account
in the longitudinal strength calculations see
Pt 3, Ch 4 Longitudinal Strength, and details are to be included
in the ship's Loading Manual.
2.10 Deck loading and scantlings
2.10.1 Adequate deck strength is to be ensured, when the proposed timber deck cargoes will
impose a mean cargo loading in excess of 8,5 kN/m2 on the weather deck.
2.10.2 In
general, the stowage rate, C, of timber deck cargoes
is to be taken as:
-
for round timber
and logs:
-
for packaged
sawn timber:
These values are based on the total volume occupied by the cargo,
including normal battens, etc. measured from bulwark to bulwark, and
deck, or hatch cover, to top of cargo.
2.10.3 Where
it is proposed to store timber more densely than that corresponding
to the above values, the appropriate value of C is to
be used.
2.10.4 The
load height, h, of the cargo at any position is to be
determined from the overall heights of cargo stowage as supplied by
the Shipbuilder. Where the height of cargo varies, a mean effective
load height is to be adopted. Attention is drawn to the limitation
on height of cargo contained in the Load Lines Conventions where these
apply.
2.10.5 A
scantling correction factor, K, is to be determined from  , and the hull scantlings are to be increased as follows:
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Deck longitudinals. The section modulus is to be multiplied by the factor 0,5
(1 + K).
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Deck beams. The
load head contained in the expression for section modulus is to be
multiplied by K, and the section modulus determined using
the increased value.
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Deck girders
and transverses. The section modulus is to be multiplied by
the factor K.
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Pillars
and deck supporting structure. The design load is to be multiplied
by the factor K, and scantlings determined using the
increased value.
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Side structure. The arrangement and scantlings of side structure are to be
considered, and increased scantlings of framing may be required.
2.11 Scantlings of hatch covers
2.11.1 The
scantlings of primary supporting members and secondary stiffeners
are to comply with Pt 3, Ch 11, 2.3 Load model 2.3.4 for
distributed cargo load p
L using p
C = h/C.
2.12 Direct calculations
2.12.1 As
an alternative to the above, the scantlings of the deck and side structure,
and of hatch covers, may be assessed using direct calculations based
on the proposed loading of the ship.
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