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Self- unloading bulk carriers discharging operations

Self unloader how it works
Fig: Self unloader how it works

Voyage orders, draft restrictions, various grades, dust suppression and rates

A copy of the Charter Party applicable to your vessel is to be handed to the Master as soon as possible, where the vessel is engaged/fixed recently. Where long term contracts of affreightment exist, copies may already be onboard. If these are not available, all the necessary information will be forwarded in the form of Voyage Instructions or Orders. These orders will describe the berths, guaranteed depth, arrival draft, shore loading facility and rates, shore take-away facility and rate, quantity of uplift of cargo, Charterers, shippers, consignees and agents etc.

If you require clarification or advice on any aspect of the concise voyage instructions or the Charter Party you are to contact the relevant Management Office.

The Master is responsible for ensuring that the vessel performs as described in the Charter Party at all times. The Company will advise the Owners of any inability to comply with the requirements of the Charter Party, and enter into discussions with the Charterers. Similarly, the Master is to ensure that any instruction or requests from the Charterers complies with the requirements of the vessel, Master and Crew as defined in the Charter Party, otherwise advice is to be obtained from the relevant Management Office.

Self unloader discharging stone cargo
Fig:Self unloader discharging stone cargo

The vessels draft with the density, and restriction of depth is also to be declared on arrival at the discharge port.

The rate of loading or discharging will be stated as a figure per working day, or the actual minimum rate, or to the ground in the case of the vessels rated capacity to discharge. If the Master determines that the vessel is in any way unable to achieve this rate, he must notify the relevant Management office immediately with the reasons.

The voyage instructions will contain concise information regarding, grades quantities, the sequential order of loading, segregation, the verification of sensitive, and optional quantity grades, the latter ideally being used for trimming.

The sequence of discharging of the various grades must be established and followed. The procedure at a change of grade is to be strictly adhered to. When submitting the loading plan to the shore terminal, agreement to the figures planned by the terminal must be ensured, and also that they have not changed any figures or grades which will require revision of the loading plan. The relevant Management Office must also be notified, and the loading plan prepared again to the satisfaction of the Master.

The bill of lading

The Bill of Lading sometimes used in the self unloading vessel trade may be of format agreed upon by the Owners, Shippers, and the Charterers. If the Master is in any doubt regarding any aspect of the Bill of Lading, he must contact the relevant Management Office before signing the same. Letters of Indemnity are not used in this trade, and the Master must contact the relevant Management Office if one is issued.

The Owners have expressed that their customers on the USA coastal trade are known, and the Master must not await the signed B/L and other instructions before releasing the cargo. This is a non-standard procedure, and if in doubt the Master is to contact the Company or Owners for clarification.


The reasons for the vessel listing during cargo operations may be as the result of:

The cause for the vessels list must be ascertained, and corrected immediately.

Increase in draft due to list

On arrival at the discharge port, care must be taken not to list the vessel, when swinging out the boom. The heeling tank (or Wing Tank) on the opposite side must be gradually filled in as the boom is being slewed out. Double bottom tanks, which will cause more of a bodily sinkage, than a list correcting effect and thus increasing the vessels draft, must never be used.

Segregation of various grades ( Discharging )

Prior to arrival at a discharge port the entire SUL system, and its associated structures, and in particular areas where vibration may bring down a previous cargo residue, must be thoroughly inspected and cleaned The system is initially to be run empty onto the main-deck , to ensure that it is clean.

The discharging plan/sequences must be accepted and approved by the receivers (terminal). The vessel is required to provide clear instructions to the Shore Terminal of any change of grade and to receive clear acknowledgement from the Shore Terminal to do so.

The Shore Terminal will require some time to prepare for the change of grade. The vessel must run the system empty for 15 mins between grades, and visually inspect that no previous grade is observed. The gates of all holds must be shut and isolated with no leakage. The hold gates for the next grade in sequence must be identified and marked. It is the responsibility of the Chief Officer and Duty Officer to ensure that the correct gates are being operated.

An independent surveyor may be employed at a change of grade, however, it remains the responsibility of the Master to ensure compliance. You are to wait for directions from ashore before starting the next grade. When cargo dividers are set on open pads, care must be taken to keep within the dividers to avoid mixing onshore.

If for any reason it is felt that a mixing of grades or contamination by other grade has occurred, the relevant Management Office must be informed immediately. The agents and P & I will then be put on notice.

The stages of SUL discharging:

  1. Understanding the voyage instructions and preparing the discharge plan.
  2. Inspection of the SUL system followed by trials.
  3. Completion of Discharge Preparation (Deck)
  4. Positioning the Boom, and compensating for list.
  5. Dipping sequence, starting with gates fore and aft.
  6. Main Discharge, as per discharge plan.
  7. Ballasting as per plan
  8. Regular inspection rounds of the SUL system.
  9. Draining and Cleaning Out.
  10. Clearing Hang-Ups as required
  11. Completion of Checklist handover each watch.
  12. Inspection of the SUL system to be in accordance with the planned maintenance system

Boom operation

Tie downs, locking pins and wire pendants with bottle-screws, are all to be used to secure the boom when stowed. The boom locking pins provided on the parking bolster, have sensors that complete an electrical circuit when the boom is locked in the stowed position. This is a safety arrangement so that the boom luffing pump motor will not start, until all the locking pins are removed. This is not entirely foolproof, and a visual check must be made by the Chief Officer, and the Electrical Engineer. There is no such safety system on the wire pendants, and care must be taken to ensure that they are free and clear.

Read more on general precautions for boom operation & safety

Discharging to the ground

Discharging to the ground means discharging as fast as possible to an open pad, or a designated area on the shore. These designated areas, spaces or pads may be areas of limited weight bearing ability and the maximum height of cargo above the ground must be ascertained. This area may also have limited space, and cargo will be spread using bulldozers, therefore care must be exercised to avoid an overflow into the water or river.

When discharging different grades to the ground, the piles of different grades must not touch to avoid commingling and possible claims. The Shore Personnel are to be requested to provide dividers, or a method of separation. For open pad discharging, the Chief Engineer is to set the rate to the best possible with regard to the restrictions or limitations if any, of the vessels SUL system. If no limitations exist, the open pad discharge provides an idea of how efficiently the vessels SUL system is running.

Discharging to the Shore hopper

Discharging to the Shore Hopper means discharging to a shore facility consisting of a hopper, and associated conveyor systems. This type of discharging is limited by the maximum rate that the shore facility can cope with. Many shore hoppers do not have baffle plates at their feeding end, and thus do not lay the cargo on the belt at a steady rate. The weight of the cargo in this kind of shore hopper will bear onto the conveyor belt directly and may cause an overload. It is important that the rate of discharge is gradually increased up to the maximum that the hopper can take-away.

An attentive radio watch must be maintained to listen for any shore requests to stop. The ‘umbilical chord’ may be activated by Shore facility personnel to stop the ships hold conveyors, however, the cargo which is still on the conveyor belts may run out before the system stops. This will further overload or plug the shore hopper, and cause further delay. It may have to be agreed to stop the ships system by tripping, and retain the cargo on the ships belt if the required rate of discharging has been low, and the load on the ships belts is well within safe limits.

Discharging to barges

Discharging to barges is carried out in ports where there is no space available on the ground, or where the cargo has to be taken away to remote places. This kind of discharging, or loading the barge, is carried out by a ‘Barge Loading Master’ who is an expert in loading barges.

The ships responsibility is mainly to maintain an agreed safe rate of discharging as required by the ‘Barge Loading Master’ and to position the Boom also as required by him. The ‘Ship/Loadmaster’ Checklists will have to be completed. It is often stated on the Checklist and acknowledged by the Barge Loading Master’s, that the vessel will not be held responsible for loading the barge and that the vessel is indemnified.

The Vessel’s Master must contact the relevant Management Office if any fault or claim is brought against the vessel, and he must not sign any such document of acceptance. The Vessel’s Master is to inspect, note and obtain acceptance by the barge of any damages that may be caused by the barge to the vessel. Adequate fendering must be provided in advance.

Ship to ship stransfer

Ship to Ship Transfer, is a lightering operation between two bulk carriers, one of which or both may be of the self unloading type. Transfer of cargo using the SUL-boom, is easier, when one of the vessels has an articulated Boom. Such an operation requires written orders from the Owners and the Charterers, who must also ensure that adequate fendering is made available, and the Master must ensure that this is carried out. It is a manoeuvre which requires planning and extreme caution.

Our detail pages illustrated many safety aspects of Bulk carrier

Home page |||Bulk carrier types ||| Handling of bulk coal |||Cargo planning ||| Carriage of grain |||Risk of iron ores |||Self unloading bulk carriers |||Care of cargo & vessel |||Cargoes that may liquefy |||Suitability of ships |||Terminal guideline |||Hold cleaning |||Cargo cranes |||Ballast handling procedure |||Bulk carrier safety |||Fire fighting systems |||Bulk carrier General arrangement

Related information

  1. Self unloader components

  2. Function of loop & bucket belt elevators

  3. Self unloaders various cargo handling gears

  4. Various type boom conveyor belts - How the belt sytem practically works ?

  5. Dealing with self unloaders stalled lift belt

  6. Conveyor belt construction & troubleshoot guide

  7. Conveyor belt installation guide

  8. Conveyor belt repair & maintenence guide

  9. Safe working practice onboard self unloading bulk carriers

  10. Preventing conveyor belt fire onboard self unloading bulk carriers

  11. Cargo work safety precautions

  12. Various bulk cargoes - free flow ability

  13. Various bulk cargoes & dealing with cargo hang ups

  14. Navigation in Ice & safety precautions

  15. Dust suppression procedure & environment protection

  16. Preparations for cargo planning, handling & stowage

  17. Maintaining safe stability onboard self-unloading bulk carriers

  18. Procedure for bulk cargo handling prior to and during loading

  19. Loading operations - voyage orders, draft restrictions, various grades and rates

  20. Loading sequence and other related considerations

  21. Self unloaders discharging operation

  22. Safety precautions for boom operation

  23. Directing gate operation, gate problems & crew duties

  24. Cargo holds/ tunnels cleaning, maintenance and check items

  25. Procedure for transporting coal on self- unloading bulk carriers

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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