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Planning and control of cargo loading and unloading operations for Bulk Carriers
Preparing vessel for cargo operations -Collecting cargo and Port Information:
The safe operation of bulk carriers is dependant on not exceeding allowable stresses in the cycle of loading, discharging, ballasting and de-ballasting. To prepare the vessel for cargo stowage and a safe planning, the loading and unloading sequences and other operational matters should be informed well in advance.
The shore terminal should provide the ship with the following information :
i) Prior to loading bulk cargo , the shipper should declare characteristics & density of the cargo, stowage factor, angle of repose, amounts and special properties.
ii) Cargo availability and any special requirements for the sequencing of cargo operations.
iii) Characteristics of the loading or unloading equipment including number of loaders and unloaders to be used, their ranges of movement, and the terminal's nominal and maximum loading and unloading rates, where applicable.
iv) Minimum depth of water alongside the berth and in the fairway channels.
v) Water density at the berth.
vi) Air draught restrictions at the berth.
vii) Maximum sailing draught and minimum draught for safe manoeuvring permitted by the port authority.
viii) The amount of cargo remaining on the conveyor belt which will be loaded onboard the ship after a cargo stoppage signal has been given by the ship.
ix) Terminal requirements/procedures for shifting ship.
x) Local port restrictions, for example, bunkering and deballasting requirements etc.
Cargo trimming is a mandatory requirement for some cargoes, especially where there is a risk of the cargo shifting or where liquefaction could take place. It is recommended the cargo in all holds be trimmed in an attempt to minimise the risk of cargo shift.
The ship's Master should be aware of the harmful effects of corrosive and high temperature cargoes and any special cargo transportation requirements. Ship Masters, deck officers, charterers and stevedores should be familiar with the relevant IMO Codes (for example, the IMO Code of Safe Practice for Solid Bulk Cargoes, the IMO Code of Practice for the Safe Loading and Unloading of Dry Bulk Carriers and the SOLAS Convention).
Devising a Cargo Stowage Plan and Loading/Unloading Plan
Exceeding the permissible limits specified in the ship's approved loading manual will lead to over-stressing of the ship's structure and may result in catastrophic failure of the hull structure. The amount and type of cargo to be transported and the intended voyage will dictate the proposed departure cargo and/or ballast stowage plan. The officer in charge should always refer to the loading manual to ascertain an appropriate cargo load distribution, satisfying the imposed limits on structural loading.
There are two stages in the development of a safe plan for cargo loading or unloading:
a) Step 1: Given the intended voyage, the amount of cargo and/or water ballast to be carried and imposed structural and operational limits, devise a safe departure condition, known as the stowage plan.
b) Step 2: Given the arrival condition of the ship and knowing the departure condition (stowage plan) to be attained, devise a safe loading or unloading plan that satisfies the imposed structural and operational limits.
In the event that the cargo needs to be distributed differently from that described in the ship's loading manual, stress and displacement calculations are always to be carried out to ascertain, for any part of the intended voyage, that:
a) The still water shear forces and bending moments along the ship's length are within the permissible Seagoing limits.
b) If applicable, the weight of cargo in each hold, and, when block loading is adopted, the weights of cargo in two successive holds are within the allowable Seagoing limits for the draught of the ship. These weights include the amount of water ballast carried in the hopper and double bottom tanks in way of the hold(s).
c) The load limit on the tanktop and other relevant limits, if applicable, on local loading are not exceeded.
The consumption of ship's bunkers during the voyage should be taken into account when carrying out these stress and displacement calculations.
Whilst deriving a plan for cargo operations, the officer in charge must consider the ballasting operation to ensure:
a) Correct synchronisation with the cargo operation.
b) That the deballasting/ballasting rate is specially considered against the loading rate and the imposed structural and operational limits.
c) That ballasting and deballasting of each pair of symmetrical port and starboard tanks is carried out simultaneously.
During the planning stage of cargo operations, stress and displacement calculations should be carried out at incremental steps commensurate with the number of pours and loading sequence of the proposed operation to ensure that:
1) The SWSF and SWBM along the ship's length are within the permissible Harbour limits.
2) If applicable, the weight of cargo in each hold, and, when block loading is adopted, the weights of cargo in two adjacent holds are within the allowable Harbour limits for the draught of the ship. These weights include the amount of water ballast carried in the hopper and double bottom tanks in way of the hold(s).
3) The load limit on the tanktop and other relevant limits, if applicable, on local loading are not exceeded.
4) At the final departure condition, the SWSF and SWBM along the ship's length are within the permissible Seagoing stress limits.
During the derivation of the cargo stowage, and the loading or unloading plan, it is recommended that the hull stress levels be kept below the permissible limits by the greatest possible margin. A cargo loading/unloading plan should be laid out in such a way that for each step of the cargo operation there is a clear indication of:-
i) The quantity of cargo and the corresponding hold number(s) to be loaded/unloaded.
ii) The amount of water ballast and the corresponding tank/hold number(s) to be discharged/loaded.
iii) The ship's draughts and trim at the completion of each step in the cargo operation.
iv) The calculated value of the still water shear forces and bending moments at the completion of each step in the cargo operation.
v) Estimated time for completion of each step in the cargo operation.
vi) Assumed rate(s) of loading and unloading equipment.
vii) Assumed ballasting rate(s)
The loading/unloading plan should indicate any allowances for cargo stoppage (which may be necessary to allow the ship to deballast when the loading rate is high), shifting ship, bunkering, draught checks and cargo trimming.
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.
All bulk carrier officers should have clear guidance and instructions available onboard their ship. There should be guidance on:
- preparation of holds
- carriage requirements of bulk cargo
- safety aspects of bulk cargo carriage etc (liquefaction, heating, hazardous gases, oxygen depletion, entry into enclosed spaces)
Fig: On a bulk carrier helicopter landing area
Bulk carrier voyage agreement - Function of bill of lading
Signing a bill of lading & relevant guideline
Our detail pages illustrated many safety aspects of Bulk carrier
- Cargo information required by ship master prior handling bulk cargo
- Care of cargo during loading- Trimming pours
- Cargo calculation recommended guideline
- Practice of draft survey & measurement of bulk cargo loaded or discharged
- Checklist for confirming stabilty and hull stress prior loading
- Bulk carrier loading manual
- Handling of deballasting (ship duties) during high loading rate
- Shipboard hazards & bulk carriers safety guideline
- Limitations on exceeding load lines
- Risk of deviation from the loading limitations
- Cargo handling guidance for deck officers
- Limitations of overloading of cargo holds & countermeasures
- How to plan cargo discharge in a safe manner ?
- Cargo damage survey guideline
- Cargo loading agreement between ship and terminal
- Cargo and ballast handling guide
- Responsibility of ship during cargo operation
- Inadequate cargo weight measurement during loading- How to avoid overload or shortfall of cargo ?
- Additional cargo documents required for bulk cargo loading
- Bulk carrier acceptability of loading regulation
- Shearing forces & bending moments limitations in bulk carriers
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Risk of Heavy cargoes & Monitoring the Ship's Loading limits
How to avoid risk of vessel being overloaded
Local loading criteria defining maximum allowable cargo weight in each cargo hold
Structural standards & strengthening of bulk carriers
Preparing vessel for cargo operations -Collecting cargo and Port Information
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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