Carriage of Solid Bulk Cargoes other than Grain:
(1) Every ship loading solid bulk cargoes other than grain shall comply with the general requirements of the EC code and the particular requirement or precaution specified in appendix A, B and C of that code.
(2) Bulk cargoes shall be loaded and trimed reasonably level, as necessary, to the boundaries of the cargo space as to minimize the risk of shifting and to maintain adequate stability throughout the voyage.
(3) When bulk cargoes are carried in “Tween-docks” the hatchways of such “Tween-docks” shall be closed in those cases where the loading information indicates an unacceptable level of stress on the bottom structure if the hatchways are left open. The cargo shall be trimmed reasonably level and shall either extend from side to side or be secured by additional longitudinal divisions of sufficient strength. The safe load-carrying capacity of the “twin-docks” shall be observe to ensure that the dock-structure is not overloaded.
(4) Concentrates or other cargoes which may liquefy shall only be accepted for loading when the actual moisture content of the cargo is less than its transportable moisture limit;
Provided that such concentrates and other cargoes may be accepted for loading even when their moisture content exceeds the above limit, where the safety arrangements including adequate stability in case of an assumed shift of cargo and adequate structural integrity are to the satisfaction of the Nautical Advisor.
(5) Prior to loading a bulk cargo which is not a cargo classified in accordance with the provisions if sub-rule (1) of rule 10 but which has chemical properties that may create a potential hazard, special precautions fro its safe carriage shall be taken.
(6) Every ship carrying cargoes specified in Appendices A, B, and C of B.C. Code shall be issued with a certificate of compliances as specified in the Second Schedule. Such certificate shall be issued only after such ship complies with the requirements of these rules and the Code of safe Practice for Solid Bulk Cargoes (B.C. code).
(7) Such certificate of compliance referred to in Sub-rule.
(8) Shall be in force for a period to 5 years from date of issue or such short period as specified in the certificate.
Procedure for Calculating Maximum Allowable Weight that can be loaded in a bulk carrier for single & Adjacent Holds:
When bulk carriers are designed a maximum tonnage is assumed for each hold and the ship is then built with sufficient strength to carry the intended voyage. A ship’s loading plan should never propose the loading of a tonnage which exceeds the maximum permitted tonnage.
The distribution of cargo along the ship’s length has a direct influence on both the global bending & shearing of the hull girder and on the stresses in the localised hull structure.
The more commonly adopted cargo distribution are:-
A) Homogenous Hold Loading Condition:-
- Cargo is distributed homogenously in all holds.
- Loading of this type is adapted for all types of cargoes, but in particular for carriage of low density cargo.
- Heavy density cargo such as iron ore may also be carried in same fashion.
B) Alternate Hold Loading:-
- Cargo is distributed in Alternate Holds used for loading high density cargo and is commonly employed in large Bulk Carriers.
- Such type of cargo distribution helps to keep Gm of vessel small and reduce adverse rolling period of stiff ships.
- Weight carried in each hold is approximately twice of that maximum permissible load in a single hold in a homogenous load distribution.
- The structure of the ship is specially designed and reinforced to withstand stresses.
- Holds which remain empty are not reinforced.
- Ships which are not approved for alternate holding must never do this.
C) Block Hold Loading:-
- In Block loading the weight of cargo to be carried should cater to ship’s sailing draught and capability of the structure.
- The quantity of cargo which can be carried in blocks is much less than the sum of full cargo capacity of individual hold at the max. draught condition.
- Part loaded or Block loading conditions should only be adopted in either of the following Conditions:-
- Such loading distribution is described in ship’s loading manual specifying the holds designated for block loading.
- The ship’s structure in the way of cargo holds is transverse cross decks, double bottom structures & transverse w/t b/w in the way of cargo hold are adequately reinforced.
- The ship is provided with approved loading criteria that define the maximum cargo weight limits as function of mean draught for each hold & block of holds and ensure that sea-going SWSF and SWBF are within the permissible limits.
Calculations of Maximum Permissible Loads:-
- Whilst the classification societies normally allow a margin for error when stating the maximum permissible load for a hold the margin is usually very small and should never been relied upon.
- Planned hold loadings should never exceed the hold loading criteria given in the approved loading manual.
- The max. permissible tonnage for each hold is calculated on the assumption that the cargo will be trimmed reasonably level to the boundaries of the spaces and the double bottom cross deck structures are designed based upon trimmed cargo distributed symmetrically in hold space.
- The maximum tonnage which can be placed in a hold with safety may be considerably reduced when the ship is being block loaded, where the total max permissible load in the two adjacent holds should not exceed 1.25x maximum corresponding alternate hold load with D.B. Tanks empty.
- The loading criteria is specified in the loading manual defines the max permissible cargo on each hold & block hold loading to be a function of non-permissible draft at mid-length of the hold for each condition of loading.According to IMSBC code any cargo with a SF of 0.56 m3/t or less is defined as high density cargo & specifies structural strength arrangements for C/H, designed to carry such cargoes.
- Maximum cargo loaded (in tonnes) in a hold = 0.9 × L × B × D
- Where L = Length (in metres) of cargo hold
- B = Breadth (in metres) of cargo hold
- D = Summer load draught (in metres).
- If the cargo is untrimmed or partially trimmed, then:
- Maximum height of cargo pile = 1.1 × D × Stowage Factor (Where Stowage Factor is given in m3/t)
- Maximum cargo loaded (in tonnes) in a hold = 0.9 × L × B × D
- If the cargo is trimmed level, then 20% more cargo may be loaded (as calculated in [i] above) in the lower hold.
- The cargo officer should calculate the maximum permissible tonnage for each cargo hold. This is found in the ship’s stability book, but can be calculated by the formula:
- Max. Permissible Tonnage = Total Area of Tanktop (m2) × Allowed Load (i.e., Tanktop Strength in Tonnes per m2).
(Note: the above formula may only be used for homogeneous bulk cargoes and not cargoes such as steel coils.)
- The IACS estimates that an extra 10% of stresses on the vessels structure increase the SWSF & SWBM by 40% and 20% respectively. These small variations in loads can be easily caused by improper cargo handling & distribution during loading period.
Precautions before and during loading – Bulk carriers guideline:
Before loading commences the following precautions must be taken and must remain in force whilst the vessel is loading bulk cargoes:
- The Master must ensure that he has as much information as possible concerning the nominated cargoes. All appropriate publications are to be consulted in this respect. The Master must also ensure that he is fully aware of the dangers, precautions and peculiarities, any ventilation and instrumentation requirements associated with the cargoes to monitor temperatures, gas and oxygen levels, moisture content etc. Where there is any doubt, the master is to contact the relevant Management Office for advice.
- When declaring the amount of cargo the vessel can load, due attention must be paid to limitations and draft restrictions at the ports of discharge, bunkers to be taken and trim required for adequate manoeuvrability of the vessel during the voyage.
- A Pre-Loading Meeting with the Shore facility is to be held to discuss the Chief Officer’s Cargo/Ballast Load Plan, communications and any relevant Port Regulations applicable to the vessel.
- It is of the utmost importance that Loading Operations are carried out with careful regard to the ship’s stability, as well as bending moments and shear force limitations.
- The OOW is fully aware of the times of high and low water at the berth.
- The ship’s moorings are to be closely monitored and adjusted as necessary to ensure that they have the correct tension.
- The OOW must closely monitor the condition of the cargoes being loaded and report any defect immediately.
- Where appropriate a gas free certificate is to be issued by a marine chemist.
- Where slops have been retained on board these are to be isolated in the appropriate slop tank and inerted.
Maintaining standard loading condition:
All ships nominated for loading should hold the appropriate valid statutory certification including, if required, the document of compliance for ships carrying solid dangerous goods in bulk.
It is recommended that the period of validity of the ship’s certificates be sufficient to remain valid during loading, voyage and unloading times, plus a reserve to allow for delays in berthing, inclement weather or both.
The ship owner, manager or operator, when offering a ship for a particular cargo or service, should ensure that the ship:
- is maintained in a sound, seaworthy condition;
- has on board a competent crew;
- has on board at least one officer proficient in the languages used at both the loading and unloading ports, or has an officer available who is proficient in the English language; and
- is free of defects that may prejudice the ship’s safe navigation, loading or unloading.
It is essential that a ship selected to transport a solid bulk cargo be suitable for its intended purpose taking into account the terminals at which it will load or unload.
The charterer and shipper when accepting a ship for a particular cargo or service should ensure that the ship:
- is suitable for access to the planned loading or unloading facilities; and
- does not have cargo handling equipment which would inhibit the safety of the loading and unloading operations.
Ships nominated for bulk loading should be suitable for the intended cargo. Suitable ships should be:
- weather tight, and efficient in all respects for the normal perils of the sea and the intended voyage;
- provided with an approved stability and loading booklet written in a language understood by the ship’s officers concerned and using standard expressions and abbreviations. If the language is neither English, nor French, nor Spanish, a translation into one of these languages should be included;
- provided with hatch openings of sufficient size to enable the cargo to be loaded, stowed and unloaded satisfactorily; and
- provided with the hatch identification numbers used in the loading manual and loading or unloading plan. The location, size and colour of these numbers should be chosen so that they are clearly visible to the operator of the loading or unloading equipment.
Most Common Hazards of Bulk Cargoes on Board Ships are mentioned below:
- Cargo shift: Cargo shift has always remained as one of the greatest dangers on bulk carriers. This problem is greater for ships carrying grain cargoes. Grain settles by about 2% of its volume. Because of this settling, small void spaces exist on the top of grain surface. These void spaces permit the grain to shift. The free flowing characteristics of grain reduce the stability of any ship carrying it. Trimming is undertaken to reduce the danger of cargo shifting. Rolling can also cause shifting of cargo from one side to the other and reduce her positive stability resulting in the vessel to capsize.
- Cargo falling from height: Cargoes like iron ore, quartz and steel scraps are high density cargo. There is a possibility of cargo falling from height during cargo operations. Cargo may either fall from the conveyor belt of the shiploader or from the discharging grab on to the deck of the ship. People working on deck can get injured badly if hit by the sizeable lumps of the bulk cargo. It can be as bad as death. Cargo operation should always be monitored by responsible officers and care should be taken that no unwanted personnel are present on the working area of the deck. Persons who are involved in the cargo operation should wear protective clothing including hard hats, safety shoes and highly visible vests.
- Dust from working cargo: Dust is one of the most common hazards in bulk carriers. Many bulk cargoes are dusty by nature. Dust particles are small enough to be inhaled and if inhaled can have disastrous effects on health. Anyone working on the deck can be exposed to high levels of dust. Dust can cause sneezing and irritation of the eyes. Where possible it is always best to avoid exposure to cargo dust however if exposure cannot be avoided protective face masks should be worn. Those involved in cargo operation and need to be present on deck when a dusty cargo is being loaded or discharged and anyone sweeping cargo with a brush or with air should wear a suitable respirator. Filters should be renewed when soiled. Deck machinery should be properly protected as they can be adversely affected by dust.
- Cargo Liquefaction: Liquefaction is a phenomenon in which solid bulk cargoes are abruptly transformed from a solid dry state to an almost fluid state. Many common bulk cargoes such as iron ore fines, nickel ore and various mineral concentrates are examples of materials that may liquefy. Liquefaction occurs as a result of compaction of the cargo which results from engine vibrations, ship’s motion and rolling and wave impact that further causes cargo agitation. Liquefaction results in a flow state to develop. This permits the cargo to slide and shift in one direction thus creating free surface effect and reducing the GM thereby reducing stability. Shippers declaration should be thoroughly examined by the chief officer before loading any bulk cargo. He must make sure that the moisture content of the cargo to be loaded should not exceed the transportable moisture limit to avoid liquefaction during the voyage. Often shippers declaration turn out to be faulty. Spot checks can also be carried on board ships to check the moisture content.
- Structural damage: Heavy cargoes place high loads on the structure and structural failure is therefore probable. High density cargoes occupy a small area for a large weight that is they have a low stowage factor. It is therefore important that the tank top has sufficient strength to carry heavy cargoes like iron ore, nickel ore, bauxite etc . The load density of the tank top should never be exceeded. Tank top strength is provided in the ship’s stability booklet. Exceeding the maximum permissible cargo load in any of the holds of a ship will lead to over stressing of local structure. Overloading will induce greater stresses in the double bottom, transverse bulkheads, hatch coamings, hatch covers, main frames and associated brackets of individual cargo holds. Poor distribution of and/or inadequate trimming of certain cargoes can result in excessive bending and sheer forces.
- Oxygen depletion: Sea transportation of bulk cargoes of an organic nature such as wood, paper pulp and agricultural products may result in rapid and severe oxygen depletion and formation of carbon dioxide. Thus apparently harmless cargoes may create potentially life threatening conditions. The cargo holds and communicating spaces in bulk carriers are examples of confined spaces where such toxic atmospheres may develop. Several fatal accidents can occur when people enter unventilated spaces. The IMSBC code lists the following cargoes as potentially oxygen depleting: coal, direct reduced iron, sponge iron, sulphide concentrates, ammonium nitrate based fertilisers, linted cotton seed. Various gaseous products are formed including carbon monoxide, carbon dioxide, hydrogen sulphide and hydro carbons. Entry of personnel into enclosed spaces should be permitted only when adequate ventilation and testing of the atmosphere is done with appropriate instruments. Emergency entry may be undertaken with SCBA. Some cargoes also use up oxygen within the cargo space. The main examples are rusting of steel swarf cargoes. Some grain cargoes may also deplete the oxygen content in the cargo space.
- Corrosion: Some cargoes like coal and sulphur can cause severe damage due to corrosion. Cargoes of sulphur in bulk are normally subjected to exposed storage and are thus subjected to inclement weather thereby resulting in the increase of moisture content of the cargo. Wet sulphur is potentially highly corrosive. When sulphur is loaded, any retained free water filters to the bottom of the holds during the voyage, from where it is pumped out via the bilges. Some water remains on the tank top and reacts with sulphur. This leads to the release of sulphuric acid resulting in the corrosion of the ship’s holds. Pond coal which is reclaimed after having been abandoned and dumped in fresh water ponds usually have high moisture content and sulphur content. This type of coal may be liable to react with water and produce acids which may corrode parts of the ship.
- Contamination: Preparation of cargo holds for the next intended carriage is a critical element of bulk carrier operations. A lack of proper preparation can lead to claims related to cargo quality such as contamination, water ingress or cargo loss. Residues and dust of previous cargo can contaminate the presently loaded bulk cargo and can cause cargo stains that are not acceptable. Cement when contaminated by residues of previous cargo reduces its binding capacity. Unrefined sugar if stored near or above dry, refined sugar can damage it by the draining syrup. Water ingress may result from leaking hatch covers, back flow through bilge systems, leaking manhole lids and inadequate monitoring. Cargoes like salt can absorb moisture and dissolve into a liquid. Sugar can ferment in the presence of moisture. The bilges should be pumped out regularly during the voyage.
- Fire: Bulk cargoes are deemed to present a great deal of fire hazards. Many bulk cargoes have a tendency to heat due to the oxidation process taking place during the voyage. Common cargoes like coal, sulphur, cotton, fishmeal are liable to spontaneous heating. Coal also emits methane which is a flammable gas. When mixed with air it can form an explosive mixture. Dust created by certain cargoes may constitute an explosion hazard. Sulphur dust can readily ignite causing an explosion. Friction between cotton bales can cause spontaneous combustion and produce heat. Fire precautions should be strictly observed on bulk carriers.
The ship as carrier is obliged to care for the cargo in an expert manner to ensure it is discharged in the same state in which it was loaded. The IMSBC code should be consulted for the safe stowage and shipment of solid bulk cargoes. Suitable precautions and good seamanship should be adopted to minimise and overcome the hazards of bulk cargoes.
Note: This is not an exhaustive list of hazards of bulk cargo, but enumerates the most common ones.
Common Structural Rules for Bulk Carriers (CSR):-
- It is a comprehensive and consistent rule set which will set the standard for oil tankers and bulk carriers.
- The new rules set consists of two main parts:-
- General Hull requirements applicable to tanks & bulk carriers such as wave loads hull girder strength buckling & fatigue requirements.
- Ship-type specific requirements only applicable to bulk carriers or oil tankers.
- These rules comply with SOLAS II-I Reg. 3.10 “Global Based Ship Construction Standards for bulk carriers & oil tankers” (CBS).
Application Applies to:-
- Tankers for oil & oil product with length 150m or above.
- Bulk carriers with length of 90m or above.
- Excluded by the CSR are – Ore Carriers open hatch bulk carriers w/o hopper and TST, OBO’s, self unloaders and some other specialized bulk carriers.
Key Features of the CSR BC, effective as on 1st July 2015:-
- Extended verification scope including FE analysis of all cargo holds.
- More transparent & consistent requirements including technical background.
- Improved load model/ formulations based on direct wave load analysis.
- Enhanced fatigue standard including detail design standard.
- Hull girder buckling also including lateral pressure and combination with shear stress.
- Hull girder ultimate limit state assessment, including damage condition.
- Compliance with IMO Global Based Maintenance & Standards (GBS).
- Increased design grab weight for Paramax & Capasize V/L’s (Applicable only for Bulk Carriers).
Consequence of CSR for BC & OT:-
- The side shell plating both in mid ship area and in way of E/R & A.P.T. may need reinforcement or increase in thickness.
- The grab notation requirements have been modified. The minimum mass of unladen grab has been increased to 35tons for Capesize vessels and 30ton for Panamax B.C. Larger grab weight will give thicker inner bottom plating with length equal to or greater than 200m.
- Finite element yielding assessment has limited impact, but FE backling assessment leads to scantling impact for some members such as:
- Hopper Structure
- Inner Hull upper part
- Longitudinal Bulkhead upper part.
- Horizontal stringers in the double hull.
- Double bottom floors
- The increase scope for FE analysis has a significant scantling impact in the way of foremost & aftermost C/H and also primary members connected to collision bulkhead, F.P.T & structures attached to engine room bulkhead inside E/R.
- It is further seen that hatch cover design and / or scantlings in way of outside midship region may need to be improved. The larger opening of the hatch for Handymax size vessel will lead to higher torsional stresses on hull girder. So special attention is paid through CSR to the stressed & fatigue developing in the hull girder structure of the vessel.
Loading / Unloading plan as per Code of Practice for Safe Loading and Unloading of Bulk Carrier:
- The BLU Code has been developed by IMO to minimize losses of bulk carriers.
- The purpose of the Code is to assist persons responsible for the Safe Loading or Unloading of bulk carriers to carry out their functions and to promote the safety of bulk carriers.
- The Code primarily covers the safety of ships loading and unloading solid bulk cargoes, excluding grain, and reflects current issues, best practices and legislative requirements.
- Broader safety and pollution issues such as those covered by the SOLAS, MARPOL and Load Line Conventions are not specifically included in the Code.
- The recommendations in this Code provide guidance to shipowners, masters, shippers, Operators of bulk carriers, charterers and terminal operators for the safe handling, loading, and unloading of solid bulk cargoes.
- The loading or unloading plan should be prepared in a form such as that shown in appendix 2 of the BLU Code.
- Worked examples of this form are also shown in appendix 2. A different form may be used provided it contains the essential information to meet the requirements of this Code.
- The minimum information for this purpose is that enclosed in the heavy line box on the sample form.
- The loading or unloading plan should only be changed when a revised plan has been prepared, accepted and signed by both parties. Loading plans should be kept by the ship and terminal for a period of six months.
- A copy of the agreed loading or unloading plan and any subsequent amendments to it should be lodged with the appropriate authority of the port State.
Recommended Contents of Port and Terminal information books:-
It is recommended that information books prepared by terminal operators, port authorities or both should contain the following information relating to their site specific requirements:
1) Port Information Books:
- Location of the port and the terminal.
- Details of port administration.
- Radio communication procedures and frequencies.
- Arrival information requirements.
- Port health, immigration, quarantine and customs regulations and procedures
- Relevant charts and nautical publications
- Pilotage requirements
- Towage and tug assistance.
- Berthing and anchorage facilities.
- Port emergency procedures.
- Significant weather features.
- Availability of fresh water, provisions, bunkers and lubricants.
- The maximum size of ship the port can accept.
- Maximum permissible draught and minimum depth of water in navigation channels
- Water density at the port.
- Maximum permissible air draught.
- Requirements for ship’s draught and trim for navigation in the waterways.
- Tidal and current information, as it affects ship movements.
- Restrictions or conditions on the discharge of ballast water
- Statutory requirements regarding loading and cargo declaration
- Information on waste reception facilities in the port.
2) Terminal Information Books:
- Details of terminal contact personnel.
- Technical data on the berths and loading or unloading equipment
- Depth of water at the berth
- Water density at the berth
- The minimum and maximum size of ship which the terminal’s facilities are designed to accept, including the minimum clearance between deck obstructions.
- Mooring arrangements and attendance of mooring lines
- Loading or unloading rates and equipment clearances
- Loading or unloading procedures and communications
- Cargo weight determinations by weight-meter and draught survey
- Conditions for acceptance of combination carriers
- Access to and from ships and berths or jetties
- Terminal emergency procedures
- Damage and indemnity arrangements
- Landing location of accommodation ladder
- Information on waste reception facilities at the terminal
3) Extreme cold weather information:
Ports and terminals situated in regions subject to extreme cold weather should advise masters where to obtain information on operation of ships under such conditions.