Carriage of timber on deck
Carriage of timber on deck offers an added advantage to the timber carrier ships. Timber carriers are constructed with special requirements in accordance with “Code of safe practices for ships carrying timber deck cargoes”.
This Code is designed to assist:
- shipowners, charterers, operating companies and ships' crew;
- port industries, shippers and pre-packaging organizations, which are involved in preparation, loading, and stowing of timber deck cargoes; and
- Administrations, manufacturers and designers of ships and equipment associated with the carriage of timber deck cargoes and those developing cargo securing manuals,
in the carriage of timber deck cargoes.
The purpose of the Code is to ensure that timber deck cargoes are loaded, stowed and secured properly to prevent, as far as practicable, damage or hazard to the ship and persons on board as well as loss of cargo overboard throughout the voyage.
The Code provides:
- practices for safe transportation;
- methodologies for safe stowage and securing;
- design principles for securing systems;
- guidance for developing procedures and instructions to be included in ships' cargo securing manuals on safe stowage and securing; and
- sample checklists for safe stowage and securing.
The provisions of this Code apply to all ships of 24 metres or more in length, carrying a timber deck cargo. This code is not yet effect but Cargo securing of timber deck cargoes should be in accordance with the requirements in the ship's Cargo Securing Manual (CSM)
These ships when loaded with timber on deck and when the timber on deck is secured in the required manner in accordance with the approved lashing plan for the vessel, are permitted to load cargo to increased drafts called the timber load lines. The Load line convention also mentions the requirements for use of timber load lines.
The variable factors with reference to above are the stability of ship and stowage and securing of the timber cargo in the required manner. Fulfilling these criteria, ships can enjoy deeper drafts.
Some Important Cargo Expressions
- Cant means 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, as defined in section “Rigidity of sawn wood packages”.
- 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, as defined in section “Rigidity of sawn wood packages”.
- Round wood means parts of trees that have not been sawn on more than one long side. The term includes, among others, 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 term includes, among others, 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 Timber Deck Cargo Code, including both round and sawn wood but excluding wood pulp and similar cargo.
Hazards Associated with carriage of Timber
- water absorption
- ice accretion
- free surfaces in slack tanks
- trapped water within stow (especially logs)
- Cargo shift due to improper lashings
- Reduced GM
The stowage and lashing requirements for timber deck cargoes are as follows
Prior loading timber cargo on weather deck, hatch covers and other openings to spaces below that area should be securely closed and battened down. The air pipes and ventilators shall be suitably protected from deck cargo. The deck shall be free from any accumulations of ice and snow. All deck lashing gear and upright shall be in sound condition ready for use. The access to crew quarters, pilot boarding access, machinery spaces, safety equipments, remote valves, sounding pipes and all other areas regularly used in the necessary working of the ship shall be kept free. Guard rails or life lines spaced not more than 330 mm apart vertically shall be provided on each side of the deck cargo to a height of at least 1 metre above the cargo.
The height of the timber deck cargo above the weather deck on a ship within a seasonal winter zone in winter should not exceed one third of the extreme breadth of the ship. The height of timber on deck shall not obstruct the navigation bridge visibility as per IMO visibility criteria. The cargo shall not project overhanging shoulders to head seas. And the deck load density of deck and hatch covers shall not be exceeded in any case.
The timber deck cargo should be stowed so as to extend over the entire available length of the well or wells between superstructures and as close as practicable to end bulkheads, and athwartships as close as possible to the ship's sides, after making due allowance for obstructions such as guardrails, bulwark stays, uprights, pilot boarding access, etc., provided any area of broken stowage thus created at the side of the ship does not exceed a mean of 4% of the breadth and to at least the standard height of a superstructure other than a raised quarterdeck. The cargo stow shall be compact.
Lashing used for timber deck cargo shall be adequate for the intended purpose and be shackled to eye plates efficiently attached to the deck stringer plate or other strengthened points as per the ship’s lashing plan. Lashings shall be so spaced that each log has atleast two lashing running on it.
All lashings and components used for securing are required to have a breaking strength of not less than 133 kN. These shall not show an elongation of more than 5% after stressing at 80% of their breaking strength. Also these shall not show any permanent deformation after having been subjected to a proof load of not less than 40% of their original breaking strength.
After tightening each lashing shall have a load of 27 kN in the horizontal part and 16 kN in the vertical part. Having secured initially the bottle screws in the lashing shall be left with atleast half threads for further tightening during voyage.
When required by the nature, height or character of the timber deck cargo, uprights where fitted, they should be made of steel or other suitable material of adequate strength, taking into account the breadth of the deck cargo. These are fixed to deck by angles, metal sockets or equally efficient means spaced at intervals not exceeding 3 m.
On loose or packaged sawn timber, the spacing between lashings shall be 3m for a stow height of 4 m and below and 1.5m for a stow height of above 4m. The packages stowed at the upper outboard edge of the stow should be secured by at least two lashings each. Rounded angle pieces of suitable material and design should be used along the upper outboard edge of the stow to bear the stress and permit free reeving of the lashings.
On the timber deck cargo stowed over the hatches and higher, additionally a system of athwartship lashings (hog lashings) joining each port and starboard pair of uprights near the top of the stow shall be provided. Hog lashings are normally used over the second and third tiers and may be set "hand tight" between stanchions. A lashing system to tighten the stow is provided whereby a dual continuous wire rope (wiggle wire) is passed from side to side over the cargo and held continuously through a series of snatch blocks or other suitable device, held in place by foot wires. Wiggle wires are fitted in the manner of a shoelace to tighten the stow. Wire rope lashings are used in addition to chain lashings. Chain lashings which are passed over the top of the stow and secured to substantial pad eyes or other securing points at the outboard extremities of the cargo.
All lashing and components used for the securing of the timber deck cargo should be tested, marked and certified according to national regulations and the respective certificates shall be maintained on board. A further visual examination of lashings and components should be made at intervals not exceeding 12 months.
Preparations before loading of timber deck cargoes
1) The following information as applicable for each parcel of cargo should be provided by the shipper and collected by the master or his representative:
- total amount of cargo intended as deck cargo;
- typical dimensions of the cargo;
- number of bundles;
- density of the cargo;
- stowage factor of the cargo;
- racking strength for packaged cargo;
- type of cover of packages and whether non-slip type; and
- relevant coefficients of friction including covers of sawn wooden packages if applicable
2) Confirmation on when the deck cargo will be ready for loading should be received.
3) A pre-loading plan according to the ship's Trim and Stability Book should be done and the following should be calculated and checked:
- stowage height;
- weight per m2;
- required amount of water ballast; and
- displacement, draught, trim and stability at departure and arrival
4) The stability should be within required limits during the entire voyage.
5) When undertaking stability calculations, variation in displacement, centre of gravity and free surface moments due to the following factors should be considered:
- absorption of water in timber carried as timber deck cargo;
- ice accretion, if applicable;
- variations in consumables; and
- ballast water exchange operations, in accordance with approved procedures
6) Proper Instructions for ballast water exchange operations, if applicable for the intended voyage, should be available in the Ballast Water Management Plan.
7) A lashing plan according to the ship's Cargo Securing Manual (CSM) should be prepared and the following calculated:
- weight and height of stows per hatch;
- number of sections in longitudinal direction per hatch;
- required number of pieces of lashing equipment; and
- required number of uprights, if applicable
8) The certificates for the lashing equipment should be available in the ship's Cargo Securing Manual.
9) When the initial stability calculations and lashing plan have been satisfactorily completed, the maximum cargo intake should be confirmed.
10) Pre-load, loading and pre-lashing plans should be distributed to all involved parties (i.e. supercargo, stevedores, agent, etc.).
11) Weather report for loading period and forecasted weather for the sea voyage should be checked.
12) It should be confirmed that the stevedoring company is aware of the ship's specific requirements regarding stowage and securing of timber deck cargoes.
13) All ballast tanks required for the voyage and included in the stability calculations should be filled before the commencement of loading on deck and it should be ensured that free surfaces are eliminated in all tanks intended to be completely full or empty.
14) Hatch covers and other openings to spaces below deck should be closed, secured and battened down.
15) Air pipes, ventilators, etc., should be protected and examined to ascertain their effectiveness against entry of water.
16) Objects which might obstruct cargo stowage on deck should be removed and secured safely in places appropriate for storage.
17) Accumulation of ice and snow on areas to be loaded and on packaged timber should be removed.
18) All sounding pipes on the deck should be reviewed and necessary precautions should be taken that safe access to these remains.
19) Cargo securing equipment should be examined in preparation for use in securing of timber deck cargoes and any defective equipment found should be removed from service, tagged for repair and replaced.
20) It should be confirmed that uprights utilized are in compliance with the requirements in the ship's Cargo Securing Manual
21) A firm and level stowage surface should be prepared. Dunnage, where used,
22) should be of rough lumber and placed in the direction which will spread the load across the ship's hatches or main deck structure and assist in draining.
23) Extra lashing points, if required, should be approved by the Administration.
24) It should be ensured that dunnage is readily available and in good condition.
25) Friction enhancing arrangements, where fitted, should be checked for their condition.
26) Cranes with wires, brakes, micro switches and signals (if they are to be used) should be controlled.
27) It should be verified that illumination on deck is working and ready for use.
Ship to shore communication
28) Radio channels to be used during cargo operations should be assigned and tested.
29) It should be confirmed that crane drivers and loading stevedores/crew understand signals to be used during cargo operations.
30) A plan should be worked out to halt loading or unloading operations due to any unforeseen circumstances that may jeopardize safety of ship and/or anyone on board.
31) All loading operations should be planned to immediately cease if a list develops for which there is no satisfactory explanation.
32) In the event that the vessel takes up an unexplained list, then no further work should be undertaken until all ship's tanks are sounded and assessment made of the ship's stability condition.
33) If deemed necessary, samples of the timber cargo should be weighed during loading and their actual weight should be compared to the weight stated by the shipper, in order to correctly assess the ship's stability.
34) Draught checks should be regularly carried out during the course of loading and the ship's displacement should be calculated to ensure the ship's stability and draft in the final condition is within prescribed limits.
35) Permitted loading weights on deck and hatches should not be exceeded.
Actions to be taken during the voyage
1) During voyage planning, all foreseeable risks which could lead to either excessive accelerations causing cargo to shift or sloshing sea causing water absorption and ice aggregation, should be taken under consideration.
2) Before the ship proceeds to sea, the following should be verified:
- The ship is upright;
- The ship has an adequate metacentric height;
- The ship meets the required stability criteria; and
- The cargo is properly secured.
3) Soundings of tanks should be regularly carried out throughout the voyage.
4) The rolling period of the ship should be regularly checked in order to establish that the metacentric height is still within the acceptable range.
5) In cases where severe weather and sea conditions are unavoidable, the Master should be conscious of the need to reduce speed and/or alter course at an early stage in order to minimize the forces imposed on the cargo, structure and lashings.
6) If deviation from the intended voyage plan is considered during the voyage, a new plan should be made.
Cargo safety inspections during sea voyages
7) Cargo safety inspections, in accordance with the items below, should be frequently conducted throughout the voyage.
8) Prior to any inspections being commenced on deck, the Master should take appropriate actions to reduce the motions of the ship during such operations.
9) Close attention should be given to any movement of the cargo which could compromise the safety of the ship.
10) When safety permits fixed and portable lashing equipment should be visually examined for any abnormal wear and tear or other damages.
11) Since vibrations and working of the ship will cause the cargo to settle and compact, lashing equipment should be retightened to produce the necessary pre-tension, as needed.
12) Uprights should be checked for any damage or deformation.
13) Supports for upright should be undamaged.
14) Corner protections should still be in place.
15) All examinations and adjustments to cargo securing equipment during the voyage should be entered in the ship's logbook.
List during voyage
1) If a list occurs that cannot be attributed to normal use of consumables the matter should be immediately investigated. This should consider that the cause may be due to one or more of the following:
- cargo shift;
- water ingresses; and
- an angle of loll (inadequate GM).
2) Even if no major shift of the deck cargo is apparent, it should be examined whether the deck cargo has shifted slightly or if there has been a shift of cargo below deck. However, prior to entering any closed hold that contains timber the atmosphere should be checked to make sure that the hold atmosphere has not been oxygen depleted by the timber.
3) It should be considered whether the weather conditions are such that sending the crew to release or tighten the lashings on a moving or shifted cargo present a greater hazard than retaining an overhanging load.
4) The possibility of water ingress should be determined by sounding throughout the vessel. In the event that unexplained water is detected, all available pumps, as appropriate, should be used to bring the situation under control.
5) An approximation of the current metacentric height should be determined by timing the rolling period.
6) If the list is corrected by ballasting and deballasting operations, the order in which tanks are filled and emptied should be decided with consideration to the following factors:
- when the draft of the vessel increases, water ingress may occur through openings and ventilation pipes;
- if ballast has been shifted to counteract a cargo shift or water ingress, a far greater list may rapidly develop to the opposite side;
- if the list is due to the ship lolling, and if empty divided double bottom space is available, the tank on the lower side should be ballasted first in order to immediately provide additional metacentric height – after which the tank on the high side should also be ballasted; and
- free surface moments should be kept at a minimum by operating only one tank at a time.
7) As a final resort when all other options have been exhausted if the list is to be corrected by jettisoning deck cargo, the following aspects should be noted:
- jettisoning is unlikely to improve the situation entirely as the whole stack would probably not fall at once;
- severe damage may be sustained by the propeller if it is still turning when the timber is jettisoned;
- it will be inherently dangerous to anyone involved in the actual jettison procedure; and
- the position of the jettisoning procedure and estimated navigational hazard must be immediately reported to coastal authorities.
8) If the whole or partial timber deck load is either jettisoned or accidentally lost overboard, the information on a direct danger to navigation should be communicated by the master by all means at his disposal to the following parties:
- ships in the vicinity; and
- competent authorities at the first point on the coast with which he can communicate directly.
Such information is to include the following:
- the kind of danger;
- the position of the danger when last observed; and
- the time and date (coordinated universal time) when the danger was last observed.