The phrase ‘deck cargoes’ refers to items and/or commodities carried on the weather deck and/or hatch covers of a ship and thereon exposed to sun, wind, rain, snow, ice and sea, so that the packaging must be fully resistant to, or the commodities themselves not be denatured by such exposure.
Deck cargoes, because of their very location and the means by which they are secured, will be subjected to velocity and acceleration stresses greater, in most instances, than cargo stowed below decks.
The stowage, lashing and securing of cargoes, therefore, require special attention as to method and to detail if unnecessary risks are to be avoided.
Causes of losses
Losses of large vehicles, rail cars, cased machinery, steel pipes, structural steelwork, packaged timber, freight containers, hazardous chemicals, boats, launches, etc. due to:
- Severe adverse weather conditions.
- Lack of appreciation of the various forces involved.
- Ignorance of the relevant rules and guiding recommendations.
- Cost limitation pressures to the detriment of known safety requirements.
- Insufficient time and/or personnel to complete the necessary work before the vessel leaves port.
- Dunnage not utilised in an effective manner.
- Inadequate strength, balance and/or number of lashings.
- Wire attachment eyes and loops made up wrongly, including incorrect methods of using bulldog grips.
- Lack of strength continuity between the various securing components.
- Taking lashing materials around unprotected sharp edges.
- Incorrect/unbalanced stowage and inadequate weight distribution.
- The perversity of shore-based labour when required to do the job properly.
- Securing arrangements, both supplied and approved, not fully utilised on the voyage under consideration.
Deck cargo shall be so distributed and stowed
1) as to avoid excessive loading having regard to the strength of the deck and integral supporting structure of the ship;
2) as to ensure that the ship will retain adequate stability at all stages of the voyage having regard in particular to:
- the vertical distribution of the deck cargo;
- wind moments which may normally be expected on the voyage;
- losses of weight in the ship, including in particular those due to the consumption of fuel and stores; and
- possible increases the weight of the ship or deck cargo, including in particular those due to the absorption of water and to icing;
3) as not to impair the weathertight or watertight integrity of any part of the ship or its fittings or appliances, and as to ensure the proper protection of ventilators and air pipes;
4) that its height above the deck or any other part of the ship on which it stands will not interfere with the navigation or working of the ship;
5) that it will not interfere with or obstruct access to the ship’s steering arrangements, including emergency steering arrangements;
6) that it will not interfere with or obstruct safe and efficient access by the crew to or between their quarters and any machinery space or another part of the ship used in the working of the ship, and will not, in particular, obstruct any opening giving access to those positions or impede it’s being readily secured weathertight.”
If all deck cargo items could be structurally welded to the weather-deck using components of acceptable strength this would remove the necessity to consider coefficients of friction between the base of the cargo and the deck or dunnage on which it rests.
Spread the load
Point-loading and uneven distribution of cargo weight can, and frequently does, cause unnecessary damage to decks and hatch-covers. Unless the weather-deck has been specially strengthened, it is unlikely to have a maximum permissible weight-loading of more than 3 tonnes/m2. Similarly, unless hatch-covers have been specially strengthened, it is unlikely they will have a maximum permissible weight-loading of more than 1.8 tonnes/m2. The ship’s capacity plan and/or general
arrangement plan should always be consulted. If the information is not there, try the ship’s stability booklet. In the event that specific values are not available onboard the ship, allow no more than 2.5 tonnes/m2 for weather-deck areas; and no more than 0.75 tonnes/m2 for hatch-covers in small vessels; 1.30 tonnes/m2 in vessels over 100m in length. (The word tonnes used later in this article means tonnes force.)
The adverse effects of point-loading are not always fully appreciated. On the one hand, a 6-tonne machine with a flat-bed area of 3m2 will exert a down-load of 2 tonnes/m2.
Various types of deck cargoes:
- Timber deck cargoes
- Iron and steel pipes or girders
- Dangerous goods
- Heavy lifts and unusually shaped goods such as locomotives, yachts and small launches, large tanks or pressure vessels and other such machinery may also be shipped
Efficient means of securing of deck cargoes:
- Code of Safe Practices for Stowage and securing of Cargo (CSS)
- Code for safe practice for carriage of timber deck cargo
- Cargo Securing Manual (CSM)
- Regulations VI/5 and VII/6 of the 1974 SOLAS Convention require
- Cargo units and cargo transport units to be loaded, stowed and secured throughout the voyage in accordance with the (CSM) approved by the administration and drawn up to a standard, at least, equivalent to the guidelines developed by the (IMO).
- The guidelines have been expanded to take into account the provisions
- the CSS Code, the amendments to that Code,
- the Code of Safe Practice for Ships Carrying Timber Deck Cargoes
- CSM gives the guidelines regarding the type of lashing and the equipment to be used for lashing so that the deck cargoes can be lashed efficiently
Battening the cargo deck before loading deck cargo:
- All openings in the weather decks e.g. hatch covers, hatch accesses, etc. should be securely closed and battened down before deck cargo is stowed on top of them.
- Ventilators, air pipes and other working gear must be in good order and protected from damage.
Safe access to equipment and spaces:
- Safe and satisfactory access are to the crews quarter, pilot boarding area, machinery spaces, sounding pipes, emergency steering gear room, LSA/FFA equipment and all other area used for the necessary working of the ship must be provided at all times.
- It should be possible to close and secure openings to such places.
Unobstructed view from the navigating bridge:
- Unobstructed view from the navigation bridge is required.
- As per SOLAS, the maximum blind length in the forward direction from the stem is twice the ship’s length or 500mtrs whichever is less.
Maximum permissible load:
- Point-loading and uneven distribution of cargo weight can, and frequently does, cause unnecessary damage to decks and hatch-covers.
- Unless the weather-deck has been specially strengthened, it is unlikely to have a maximum permissible weight-loading of more than 3 tonnes/m2.
- Similarly, unless hatch-covers have been specially strengthened, it is unlikely they will have a maximum permissible weight-loading of more than 1.8 tonnes/m2.
- The ship’s capacity plan and/or general arrangement plan should always be consulted.
- If the information is not there, try the ship’s stability booklet.
- In the event that specific values are not available onboard the ship, allow no more than 2.5 tonnes/m2 for weather-deck areas; and no more than 0.75 tonnes/m2 for hatch covers in small vessels; 1.30 tonnes/m2 in vessels over 100m in length.
- The adverse effects of point-loading are not always fully appreciated. On the one hand, a 6-tonne machine with a flat-bed area of 3m2 will exert a down-load of 2 tonnes/m2.
- Dunnage should be used to avoid point loads and to spread the load.
Effect on stability due to absorption of water or ice accretion:
- For any ship operating in areas where ice accretion is likely to occur, adversely affecting a ship’s stability, icing allowances should be included in the analysis of conditions of loading.
- The master should verify the stability of his ship for the worst condition, having regard to the increased weight of deck cargo due to water absorption and .or ice accretion and to the variations in consumables.
- An allowance should be made in the arrival condition for the additional weight.