Definitions
Timber means sawn wood or lumber, cants, logs, poles, pulpwood and all other types of timber in loose packaged forms but not including wood pulp or similar cargo.
Cant means a log that is cut in slabs, so that two opposite or sometimes three sides are flat and the other(s) curved.
Timber Deck cargo means a cargo of timber carried on an uncovered part of the freeboard or superstructure deck. It does not include wood pulp or similar cargo.
Timber load line means a special load line assigned to ship which comply with certain regulations of the International Convention of Load Lines regarding construction of the ship and stowage and securing of cargo.
Weather deck means the uppermost continuous deck exposed to weather and sea.
Fall protection system means a system having an adequate anchorage point, a safety harness, to be worn and a fall arrest device which locks when any force is applied to the system. (Fall protection is defined as a planned system used to protect a worker from death or potential injury in the event they would lose their balance while performing a task at height.)
Application and Stability Information
The code applies to all ships of 24 m or more in length when carrying timber deck cargoes.
Stability of the ship at all times should be positive as per the criteria taking into account increased weight of timber due to absorption of water and ice accretion, variations in consumption of fuel and freshwater, free surface effect of liquids in tanks, and weight of water trapped in broken spaces within the timber deck cargo especially logs.
Stability Information to Masters
Comprehensive stability information is to be provided to the master and should include stability characteristics for the varying conditions of service i.e. loaded, ballast arrival and departure conditions.
Tables or diagrams to assess the stability and initial metacentric height at various drafts to ensure ships comply with stability criteria.
Rolling period tables and corrections to be applied for free surface effect.
Changes in the deck cargo when the permeability is significantly different from 25%.
Maximum permissible amount of deck cargo.
Information on the use of anti-rolling devices if these are fitted on the ship.
The Master should stop all loading operations if a list develops due to unknown reasons and should proceed out to sea in upright condition.
The initial GM should be adequate but a large GM will result in rapid and violent motion in heavy seas causing high stresses on the lashings.
Recommended that GM should not be more than 3% of breadth.
Compliance with stability criteria does not ensure immunity from capsizing or absolve the master of his responsibilities.
He should therefore exercise prudence and good seamanship and proceed at a safe speed and course with regard to the season of the year, weather forecasts and area of navigation.
A number of influences such as beam wind on ships, icing of topsides, water trapped on deck, rolling characteristics, following seas, etc. adversely affect the stability of the ship.
Stability Criteria as per IS Code 2008
For ships loaded with timber deck cargoes and provided that the cargo extends longitudinally between superstructures where there is no limiting superstructure at the after end, the timber deck cargo shall extend at least to the after end of the aftermost hatchway, transversely for the full beam of ship, after due allowance for a rounded gunwale not exceeding 4% of the breadth of the ship and/or securing the supporting uprights and which remains securely fixed at large angles of heel.
The area under the righting lever curve (GZ curve) shall not be less than 0.08 meter-radians up to ϕ = 40° or the angle of flooding if this angle is less than 40°.
The maximum value of the righting lever (GZ) shall be at least 0.25 m.
At all times during a voyage, the metacentric height GM(0) shall not be less than 0.1 m, taking into account the absorption of water by the deck cargo and/or ice accretion on the exposed surfaces.
When determining the ability of the ship to withstand the combined effects of beam wind and rolling according to wind heeling criterion of IS code 2008, the 16° limiting angle of heel under action of steady wind shall be complied with, but the additional criterion of 80% of the angle of deck edge immersion may be ignored.
Stowage of Timber Cargoes
The principle of safe carriage of timber deck cargo is to make the stow as solid and compact as possible so as to prevent slack which would cause the lashings to loosen, produce a binding effect within the stow, and reduce to minimum the permeability of the stow.
Lashings of Timber Deck Cargoes
Lashings prevent deck cargo from shifting by increasing the friction and counteracting forces acting on the stow.
Lashings must be of sufficient strength as recommended in the code and maintained at the necessary tension.
Shifting of Timber Deck Cargoes
Shifting of timber deck cargoes is due to insufficient strength of the lashings, slackening of the lashings due to compaction of the cargo or unsuitable devices used for tightening the lashings.
Movement of the cargo across the deck or hatch covers due to less friction especially in ice or snow.
Failure of the uprights due to less strength or excessive forces.
Heavy rolling or pitching of the ship and impact of heavy seas.
PART A – OPERATIONAL REQUIREMENTS
Refer to Chapter 2, 3 and 4 of 2011 TDC code.
Preparation Before Loading of Timber Deck Cargoes
Hatch covers and other openings to spaces which are not used for the normal working of the ship must be securely closed and battened down.
Air pipes, sounding pipes and ventilators should be protected and valves and means of closing checked that they are effective against entry of water.
Ice, snow and water should be removed from the deck and hatch tops.
Lashing equipment may have to be examined before loading and it is preferable to have these rigged in position before loading on that area.
Precautions During Loading
Constant supervision by ship’s personnel is necessary to achieve a solid stow at all stages of loading.
The ship must be kept upright at all times to prevent unnecessary stress on the uprights and a shift of cargo or unsymmetrical loading.
ANNEX A provides guidance in developing procedures and checklists for preparations before loading of timber deck cargoes, safety during loading and securing, securing of timber deck cargoes, actions to be taken during the voyage, and safety during discharge.
Precautions During Loading
The cargo must be kept free of accumulations of ice and snow.
Safe and satisfactory means of access to crew quarters, pilot boarding area, machinery spaces and all other areas used for the necessary working of the ship must be provided at all times.
It must be possible to properly close and secure openings to the above areas.
Safety equipment, devices for remote operation of valves, emergency steering gear and sounding pipes must be left accessible.
After completion of loading and before sailing a thorough inspection of the ship must be made and soundings checked to verify that no damage causing an ingress of water has occurred.
Height of Deck Cargo
The height of the timber deck cargo must be restricted to ensure adequate visibility from the navigation bridge, maintain a safe margin of stability at all stages of the voyage, and ensure the forward part of the cargo is slopped so as not to present a resistant wall to head seas.
The load density of the deck and hatches is not exceeded taking into account the possibility of ice accretion or moisture absorption by the cargo.
On a ship in a seasonal winter zone in winter, the height does not exceed one third the extreme breadth.
The height should be to at least the standard height of a superstructure other than a raised quarter deck.
Extent of Timber Deck Cargo
The timber deck cargo should be stowed so as to extend the full available length between superstructures or wells and as close as possible to the end bulkheads.
To the aftermost end of the aftermost hatchway where there is no limiting superstructure at the after end.
Athwartships as close as possible to the shipside, after making allowances for obstructions such as guard rails, bulwark stays, uprights, pilot boarding access, etc., provided the broken stowage thus created does not exceed a mean of 4% of the breadth.
Securing and Lashing of Timber Deck Cargo
Every lashing should be shackled to adequate eye plates which are efficiently attached to the deck stringer plate or other strengthened points.
They should pass over the timber deck cargo in such a way as to be as far as practicable in contact with the cargo throughout its height.
All lashings and components used for securing should have a breaking strength of not less than 133 kN, show no permanent deformation after being subjected to a proof load of 40% of the breaking strength, and show an elongation of not more than 5% at 80% of their breaking strength.
Tightening devices must be placed where they can be safely and efficiently operated when required and be capable of producing a load of not less than 27 kN in the horizontal part of the lashing and 16 kN in the vertical part.
After initial tightening at least half the thread length of screw or half the tightening capacity should be available for future use.
Every lashing should be provided with a device which will permit the length of the lashing to be adjusted.
The end lashings of each continuous length of stow should be positioned as close as practicable at the end of the stow.
Where wire rope clips are used, not less than four should be used and correctly positioned, tightened and re-tightened after stressing.
Greasing of clips, grips, shackles and turnbuckles increases holding capacity and prevents corrosion.
Uprights
Uprights designed in accordance with chapter 7 of the code should be used when required.
They should be made of material of adequate strength, spaced not exceeding 3 m, and fixed to the deck or hatch cover by efficient means.
Securing of Loose or Packaged Sawn Timber
Uprights should be used for loose sawn wood.
The timber deck cargo should be secured throughout its length by independent lashings.
Maximum spacing of lashings depends on cargo height.
Long and sturdy packages should be stowed in the outer rows.
Securing of Logs, Poles, Cants or Similar Cargo
Round wood deck cargo should be supported by uprights and secured throughout its length by independent lashings spaced not more than 1.5 m apart.
Additional athwartship lashings should be used where required.
Testing, Examination and Certification of Lashing Gear
All lashing wires, chains and components should be tested, marked and certified.
Certificates must be kept on board.
Visual examinations should be carried out every 12 months and before loading.
Guidelines for the Underdeck Stowage of Logs
Pre-stow plans must be developed.
Bilge strainers should be clean.
Logs should be stowed compactly and voids filled with dunnage.
Soundings must be checked after loading.
The Rolling Period Test
The Master must be supplied with information to determine GM using the rolling period test.
GM is obtained from GM = (fB / T)².
Tests should be carried out in calm waters with all conditions controlled.
Timber Load Lines
Timber load lines allow vessels to load to a deeper draught when timber deck cargo is correctly stowed.
If stowage does not comply with regulations, the vessel is not permitted to load to the timber line.
Reduction in freeboard is permitted due to buoyancy contribution of timber deck cargo.