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Preventing impurities during loading of bulk cargo & some useful terms for bulk carrier handling
Different types of bulk cargoes require a wide variety of care and attention. Individual cargo care information can be obtained from the shipper. Occasionally some bulk cargo have been reported contaminated by foreign objects such as coal mixed with metal scraps. If such objects are allowed to reach at conveyor belts while discharging, the entire cargo handling system can be seriously damaged, potentially putting the terminal out of operation for days, for which the vessel will be held liable.
Before beginning to to load dry bulk cargoes, ships staff must ensure that all hold fittings are in good condition and, if removable , are well secured. They need to be especially vigilant in guarding against foreign objects getting mixed in with cargo.
During loading it may not be possible to notice such contaminants, especially if the pour rate is high. The local P&I correspondent and/ or an independant surveyor should be asked to examine the cargo and to witness the loading and discharge should there be subsequent claims
Bulk carrier cargo operation related useful terms
The following definitions are extracted from the International Maritime Solid Bulk Cargoes (IMSBC) Code 2009:
Angle of Repose
The maximum slope angle of non-cohesive (ie, free- flowing) granular material. It is measured as the angle between a horizontal plane and the cone slope of the material.
Dry materials that readily shift due to sliding during transport.
- a. Non-cohesive bulk cargoes having an angle of repose less than or equal to 30° These cargoes, which flow freely like grain, shall be carried according to the provisions applicable to the stowage of grain cargoes
- b. Non-cohesive bulk cargoes having an angle of repose greater than 30° to 35° inclusive Loading is carried out using trimming equipment approved by the competent authority
- c. Non-cohesive bulk cargoes having an angle of repose greater than 35°
- Loading is carried out using trimming equipment approved by the competent authority.
Materials other than non-cohesive materials.
Cargoes That May Liquefy
Cargoes that contain a certain proportion of fine particles and a certain amount of moisture. They may liquefy if shipped with a moisture content in excess of their transportable moisture limit.
Materials obtained from a natural ore by a process of enrichment or beneficiation by physical or chemical separation and removal of unwanted constituents.
Flow Moisture Point
The percentage moisture content (wet mass basis) at which a flow state develops under the prescribed method of test in a representative sample of the material.
A state occurring when a mass of granular material is saturated with liquid to an extent that, under the influence of prevailing external forces such as vibration, impaction or ship's motion, it loses its internal shear strength and behaves as a liquid.
Materials that may react dangerously when mixed.
That portion of a representative sample consisting of water, ice or other liquid, expressed as a percentage of the total wet mass of that sample.
The movement of moisture contained in a cargo by settling and consolidation of the cargo due to vibration and ship's motion. Water is progressively displaced, which may result in some portions or all of the cargo developing a flow state.
The figure that expresses the number of cubic metres one tonne of cargo will occupy.
Transportable Moisture Limit (TML) of a Cargo Which May Liquefy
The maximum moisture content of the cargo which is considered safe for carriage in ships.
Any levelling of a cargo within a cargo space, either partial or total.
Cargo operation related guideline :
Our detail pages illustrated many safety aspects of Bulk carrier
- Cargo information required by ship master prior handling bulk cargo
Solid bulk cargoes are defined as any cargoes that are transported in a loose form without any packaging. The IMO defines these as: "any material, other than a liquid or gas, consisting of a combination of particles, granules or any other larger pieces of material, generally uniform in composition, which is loaded directly into the cargo spaces of a ship without any intermediate form of containment".
- Care of cargo during loading- Trimming pours
The loader chute, spout or grab should be kept as close to the tank top as possible and loading should be started at a low rate until the tank top in the loading area is covered with a layer of cargo. As the pile builds up on that area the cargo will roll down the pile and slowly spread over the rest of the tank top without any heavy impact.
- Checklist for confirming stabilty and hull stress prior loading
The conditions of stability, hull strength, draft and trim of bulk carriers at sea and on arrival / departure at / from port and during loading / unloading cargo, bunkering and water ballast exchange, should be worked out, ensuring safety of the vessel. Safety of the cargo vessel depends on proper GM, stress calculation and other factors as being within appropriate Limits.
- Cargo loading agreement between ship and terminal
Before loading commences there should be an agreement between the master and the terminal representative as to the rate of loading and order in which the cargo is to be distributed so as to achieve the final loading plan. In general, this agreement should be based on ship specific loading / unloading restrictions.
- Bulk carrier loading manual
It is a statutory requirement of the International Load Line Convention that, noting exemptions, "the Master of every new vessel be supplied with sufficient information, in an approved form, to enable him to arrange for the loading and ballasting of his ship in such a way as to avoid the creation of any unacceptable stresses in the ship's structure."
- Handling of deballasting (ship duties) during high loading rate
High cargo loading rates may create problems with the ballasting operation as the pumping capacity of the ship may be relatively low compared to the cargo loading rate. In such cases the cargo operation must be stopped to ensure synchronisation with the ballasting operation is maintained.When necessary, the loading rate must be adjusted to synchronise with the ship's pumping capacity.
- Cargo and ballast handling guide
It is recommended that high density cargo be stowed uniformly over the cargo space and trimming be applied to level the cargo, as far as practicable, to minimise the risk of damage to the hull structure and cargo shift in heavy weather.
- Responsibility of ship during cargo operation
It is imperative to carry out draft checks at regular intervals during the loading, and particularly when between about 75-90% of the cargo is loaded. The tonnage loaded should be compared with the terminal's weight figure, and adjustments to the final trimming figures determined and agreed accordingly.
- Shipboard hazards & bulk carriers safety guideline
Encountering hazards in bulk carriers - Possible sources
- Limitations on exceeding load lines
The safe operation of bulk carriers is dependant on not exceeding allowable stresses in the cycle of loading, discharging, ballasting and de-ballasting. Modern vessels now employ computer loading programmes to establish disposition of cargo, ballast fuel oil, fresh water and stores. Such software can be beneficial in producing the ships stability data, together with anticipated stress factors throughout the ships length
- Risk of deviation from the loading limitations
In most cases in which bulk carriers have been lost, heavy cargoes such as iron and other dense ores are a common factor. Ships are also vulnerable when carrying certain break-bulk cargoes such as steel products. This could include other ship types.
- Cargo handling guidance for deck officers
If a deviation from the loading/unloading plan is observed, the officer in charge should advise the cargo terminal immediately so that necessary corrective actions are implemented without delay. If considered necessary, cargo and ballasting operations must stop.
- Limitations of overloading of cargo holds & countermeasures
To enhance safety and flexibility, some bulk carriers are provided with local loading criteria which define the maximum allowable cargo weight in each cargo hold, and each pair of adjacent cargo holds (i.e. block hold loading condition), for various ship draught conditions. The local loading criteria is normally provided in tabular and diagrammatic form.
Practice of draft survey & measurement of bulk cargo loaded or discharged
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Operation of sea going bulk carriers involved numerous hazards . Careful planning and exercising due caution for all critical shipboard matters are important . This site is a quick reference to international shipping community with guidance and information on the loading and discharging of modern bulk carriers so as to remain within the limitations as specified by the classification society.
It is vital to reduce the likelihood of over-stressing the ship's structure and also complying with all essential safety measures for a safe passage at sea. Our detail pages contain various bulk carrier related topics that might be useful for people working on board and those who working ashore in the terminal. For any remarks please Contact us
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