Way back in 1980, when I saw a cargo ship carrying timber leaned over a wharf in Kolkata, it made just an exciting news to share. Today however, I understand what the Master must have gone through. Timber cargo gives you an additional element of risk. It is very important to understand the dangers involved and the guidance available in respect of loading of timber.
There are many cases of deck cargo getting washed off in bad weather. Deck cargo, in shipping seas has high possibility to shift. In past there have been many incidents where the complete load on hatch top has shifted transversely by considerable distance, causing list as well as danger of capsizing. The worst part of such incidents being inability to do anything much with such cargo, until ship reaches a port. Extra lashings in shifted posture being just a temporary and incomplete solution. Timber on deck definitely poses many challenges to mariners. To load, lash and to carry unsawn timber on deck is even more challenging.
Timber is carried on deck by specialized timber carriers. Sometimes, it may be loaded on bulk carriers and on multipurpose dry cargo ships. When the timber is carried on deck, the requirements of the IMO’s ‘Code of Safe Practice for Ships Carrying Timber Deck Cargoes’, (Timber Code)need to be complied with.
Chapter 1, of Timber Code, deals with Application Definitions, etc.
Part A is Operational Requirements. Chapter 2, 3 & 4 come under this part.
Chapter 2, is general recommendations on stowage and securing of timber deck cargoes. It includes: pre-loading operations; permitted loading; weights on decks and hatch covers; issues regarding stability and Load line; timber freeboard; finding visible distance; work safety and work environment aspects; stowage and securing; post-loading operations; voyage planning; and Cargo Securing Manual.
Chapter 3 is visibility and chapter 4, Physical properties of timber cargoes, contains: stowage factors; friction factors; plastic covers; package marking; water absorption; weight of ice; and rigidity of sawn wood packages.
Part B is Design of cargo securing arrangements, contains chapter 5 to 8. Chapter 5 is design principles. It deals with uprights; loose or packaged sawn wood; logs, poles, cants or similar cargoes; testing, marking, examination and certification; and lashing plans.
Chapter 6 includes: alternative design principles; general requirements; accelerations and forces acting on the cargo; physical properties of timber deck cargoes; safety factors; and design criteria for different securing arrangements. Chapter 7 is uprights and Chapter 8 is denotations used.
Annex A is Guidance in developing procedures and checklists. Annex B is Samples of stowage and securing arrangements. Annex C is Instruction to a Master on calculation of mass change of a timber deck cargo due to water absorption. The Code provides:
Existing cargo securing manuals approved under the previous Timber Deck Cargo Code (resolution A.715(17)) may remain valid.
Relevant cargo information should be provided by the shipper. The Master of the vessel should study the relevant cargo information and take the precautions. The stevedoring company should be made aware of specific requirements. All tanks are maintained in such a condition that free surface effects are minimized.
Before loading on the weather deck:
- hatch covers, etc should be securely closed and battened down;
- air pipes and ventilators should be effectively protected and check-valves, etc examined to ascertain their effectiveness;
- obstructions to cargo stowage should be removed;
- the condition of friction-enhancing arrangements should be checked;
- accumulations of ice should be removed;
- all deck lashings, uprights, etc., are kept readily available before loading; and
- all sounding pipes on the deck should be reviewed, access is kept available.
Let us get familiarized with some common forms of timber that is carried: ‘Cant’ is a log which is “slab-cut”, i.e. ripped lengthwise so that the resulting thick pieces have two opposing, parallel flat sides and, in some cases, a third side which is sawn flat.
‘Non-rigid cargo’ means sawn wood or lumber, cants, logs, poles, pulpwood and all other types of loose timber or timber in packaged forms not fulfilling specified strength requirement.
‘Rigid cargo package’ means sawn wood or lumber, cants, logs, poles, pulpwood and all other types of timber in packaged forms, fulfilling specified strength requirement.
‘Round wood’ means parts of trees that have not been sawn on more than one long side. The other forms included being; logs, poles and pulpwood in loose or packed form.
‘Sawn wood’ means parts of trees that have been sawn so that they have at least two parallel flat long sides. The other forms included being, lumber and cants in loose or packed form. Timber is used as a collective expression used for all types of wooden material covered by this Code, including both round and sawn wood but excluding wood pulp and similar cargo.
Technically related expressions:
‘Blocking device’ means a device providing physical measures to prevent sliding and/or tipping of cargoes and/or collapse of stow.‘Lashing plan’ means a sketch or drawing showing the required number and strength of securing items for the timber deck cargo to obtain safe stowage and securing of timber deck cargoes.
Safety of personnel during cargo operation is a matter of great concern. In case of timber there is a lot of learning from experience. In one particular incident, when hatches were opened two stevedores entered the hold, later found dead. It was established that the men had actually died from asphyxia due to an oxygen depleted atmosphere within the hold. The holds should be opened for as long as possible before commencing cargo operations. The cargo can be ventilated during the voyage as appropriate. These measures are especially important in humid climates where the exposure to risk will be greatly increased.
A risk assessment of each type of timber cargo should be undertaken to identify hazards and ensure control measures. Health related safety can occur as in the following situations:
- wet timber can cause slippery exterior;
- timber loaded in cold areas may have film of ice, increasing the chances of slips;
- logs may contain poisonous insects, creatures;
- timber loaded in holds may emit Carbon Dioxide, causing an Oxygen deficient atmosphere; and
- treated timber may also produce toxic fumes.
Thus, use of studded shoes and suitable protective gear must be worn whenever needed. Most timber deck cargoes are pre-slung. Whenever slinging the outermost cargo, it must be ensured that there is no possibility of personnel falling over the side due slings. Many ways and techniques are used to prevent falling of personnel working on decks of timber ships.
Timber must be appropriately loaded on main deck to avail the application of timber loadlines and timber alternate intact stability criteria. A cargo that is loaded, can self block or be restricted by other cargo as much as practicable. Timber ships are fitted with additional guards to protect structures such as air/sounding pipes. The duty officers should immediately make a note of any damage that is caused. An undiscovered damage may lead to ingress of water later.
The basic principle for the safe carriage of timber deck cargo is to make the stow, as solid, compact and stable as practicable. The purpose is to prevent movement in the stow, which could cause the lashings to slacken and produce a binding effect within the stow and also reduce the permeability of the stow to a minimum. Openings in the deck, exposed to weather over which cargo is stowed, should be securely closed and battened down. The ventilators and air pipes should be effectively protected. Deck cargo should be stowed so that access is provided to and from designated escape routes and spaces essential to operation of the vessel, such as machinery spaces and crew’s quarters, as well as to safety equipment, fire-fighting equipment and sounding pipes. It should not interfere in any way with the navigation and necessary work of the ship.
Care should be taken to avoid the creation of voids or open spaces when loading cargo. Voids, where created, should be filled with loose timber or blocked by vertical H-frames with required strength to avoid cargo shifting. Timber deck cargo which substantially overhangs (one-third of the package length) hatch coamings or other structures in the longitudinal direction, should be supported at the outer end by other cargo stowed on deck or railing or equivalent structure of sufficient strength to support it.
One or more of the following principal methods may be used to secure timber deck cargoes, by themselves or in combination with each other:
- different types of lashing arrangements;
- bottom blocking of the base tier in combination with lashing;
- blocking over the full height of the cargo by, uprights / complemented by lashing;
- frictional securing, considering research, weather and voyage criteria; and
- other practical securing enhancement, (considering weather and voyage), such as:
I. non slip paints on hatch covers;
II. liberal use of dunnage in the stow to shore and bridge gaps;
III. double lashing in exposed areas; and
IV. consideration given to the use of locking tiers.
Securing arrangements used should be designed in accordance with Cargo Securing Manual.
Three types of lashing equipment (should be determined by factors as ship type, size and area of operation, etc)
1 chain lashings;
2 wire lashings; and
3 fabricated web lashings.
Caution in respect of using lashing equipment
- Open hooks, which may loosen if the lashing becomes slack, should not be used in securing arrangements for timber deck cargoes. Web lashing should not be used in combination with chain or wire lashing.
- The safety factors described in Annex 13 to the Lashing Code should be considered.
- All lashing equipment should be visually examined according to the manual.
- The necessary pre-tension in the lashings used should be maintained throughout the voyage. Lashings must be carefully examined at regular intervals during the voyage and tightened as necessary.
- Slip hooks or other appropriate methods may be used for quick and safe adjustment of lashings. Pelican hooks, when used, should be moused.
- Corner protectors should be used to prevent lashings (fabricated web lashings), from cutting into the cargo and to protect lashings from sharp corners.
- Every lashing should be provided with a tightening device so that it can safely and efficiently operated when required.
Cargo Securing Manual
Timber deck cargoes should be loaded, stowed and secured, throughout the voyage, in accordance with the Cargo Securing Manual, which should be based on the guidelines in the Code and drawn up to a standard at least equivalent to the guidelines developed by the Organization and approved by the Administration.
Each cargo securing arrangement for timber deck cargoes should be documented in the ship’s Cargo Securing Manual. The following parameters should be taken into account at the design stage of cargo securing systems:
- duration of the voyage;
- geographical area of the voyage;
- sea conditions which may be expected;
- dimensions, design and characteristics of the ship;
- expected static and dynamic forces during the voyage;
- type and packaging of cargo units;
- intended stowage pattern of the cargo units; and
- mass and dimensions of the cargo units.
In the Cargo Securing Manual, each stowage and securing arrangements should additionally be documented by a Lashing Plan showing at least the following:
- maximum cargo weight for which the arrangement is designed;
- maximum stowage height;
- required number and strength of blocking devices and lashings as applicable;
- required pretension in lashings;
- other cargo properties of importance for the securing arrangement such as friction, rigidity of timber packages, etc.;
- illustrations of all securing items that might be used; and
- any restriction regarding maximum accelerations, weather criteria, for non-winter conditions only, restricted sea areas, etc.
One or more generic lashing plans complying with the recommendations of the Code should be provided and maintained on board a ship carrying timber deck cargo. Lashing plans should be incorporated in the Cargo Securing Manual and the most relevant lashing plan should be consulted when stowing and securing timber deck cargoes.
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