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Self- unloading bulk carriers discharging preparations

Self-unloading vessels can reduce a cargo’s overall delivered cost per tonne because they are fast, efficient and less capital and labour intensive than on-shore based systems. The rapid turnaround time associated with self-unloaders frees up congested berths, thus reducing port costs and demurrage.

Operating 24 hours a day at speeds up of up to 5,000 tonnes per hour, self-unloaders discharge faster than conventional dry-bulk carriers and do not require the expense of stevedores or cleanup crews.

Self unloader discharging
Fig: Self unloader discharging

Pre discharging meeting

A Pre-discharge meeting is to be held at sea prior to arrival at the discharge port. The vessels Officers and Crew who will be responsible for discharging in the cargo are to attend. The agenda for discussion is as follows:
Prior to arrival discharge port

Points to be taken into consideration are:
  1. Inspection of the entire SUL system.
  2. Checking for water leaks, and accumulations in the tunnel.
  3. Water accumulation affecting the vessels trim.
  4. Use of the forward trash pumps.
  5. Reference to the voyage instructions and port information, for planning the vessels position at the berth.
  6. Rate of Discharge.
  7. Discharge plan.
  8. Discharge teams, pre-discharging meeting.
  9. Distribution plans.
  10. Inspection of the entire system for fallen objects.
  11. System simulation.
  12. Emergency stops.
  13. Dust suppression methods and tools prepared for use.
  14. Ensuring that the luffing piston is clean.
  15. That the gantry battery is charged.
  16. That hydraulic oil heaters for luffing and slewing tanks are ‘on’, and check that gate operating and isolating valves are in closed position.

Discharge operations

The discharge of cargo is to be carefully planned with regard to the vessel stability and, the following points taken into consideration: Each component or piece of equipment in the conveyor system must be set as per makers instructions, and any relative information that may be contained in the users manual is to be noted.

Before starting, the system in its entirety is to be inspected for any materials or tools which might be caught between the pulleys and belt; it is essential that no structural obstruction exists that will cause damage to the belt. All safety switches and emergency stops are to be operational. The system is to be run for a short period while checking the possible obstruction or problem.

Load the conveyor gradually while observing the behaviour of the system. The system must not be overloaded, and ship staff must be aware of any limitations. Idlers and return rollers are to be checked for material build-up, and they must rotate freely, and the hoppers and chutes must be free of any blockage.

Before commencement of discharging and after completion of discharging the Chief Engineer and the Head Tunnelman are to carry out a thorough visual inspection of the entire SUL system. Inspections of the system must be made at regular intervals during discharging.


All means of communication, must be well maintained and tested before arrival at any port. Communication with the shore terminal must be tested, and be compatible and understood by all. If an Umbilical chord is used at the discharge berth, it must be tested before commencement of discharging, and its reliability ascertained thereafter.

All communication, by any means, within the vessel and with the shore terminal, are to be clear and precise. Orders given must be accurate and positive. All codes for signal lights and buzzer alarms must be known and understood to all.

The word ‘STOP’ means that an immediate response is to be made to stop the system. This means that something is wrong either onboard or ashore and could also mean that a person is at risk. All concerned must be alert and prepared for a stop or shutdown.

The reason for a request from the shore terminal to ‘stop’ must be ascertained and logged. If the system is stopped or shut-down for any reason ship or shore, and is estimated to remain shut down for a period of two hours or more, the relevant Management Office must be notified.

Draft checks and the sounding of depths

It is of the utmost importance to check the vessels drafts on arrival alongside, and at frequent intervals thereafter. Along with reading drafts on arrival alongside, the depths at the berth must be taken physically using a lead line.

At the discharge port the vessel will most probably berth on a rising tide, and it may be crucial to discharge a quantity of cargo to lighten the vessel before low water to prevent grounding. This is especially true when discharging to a shore facility with a limited take-away capacity, as, the shore facility restrictions or any breakdown may not permit the vessel to discharge. In these circumstances the Master must notify all and make arrangements to unberth and proceed to deeper water. At no time is the vessel to be allowed to ground. Sounding of depths will confirm the depth guaranteed in the voyage instructions.

River ports are subject to silting etc and the soundings may have not been taken since the last port survey. It is imperative that the vessel sounds depths on arrival and again at Low water and the Chief Officer maintains a log of the same.

The Master must set limits for the safe underkeel clearance and the maximum trim allowed at any stage. The after draft must be kept especially in check due to the vessels added vulnerability at the stern. The adverse effects of excessive trim on the SUL system and the boom must not be underestimated.

Ventilation and effects of sweat

The trading area, route and time of the year will determine the sweat formation. As these vessels are generally without forced draft ventilation, little can be done to control the ventilation in the holds. Sweat will dampen cargoes, and will have a hang-up effect on cargoes such as a gypsum.

Cargo condition

The P & I representative may be required to do an out-turn inspection at the discharge port, at the express instruction of the Owners.

If the Master suspects that the condition of the cargo has changed during the voyage for whatever reason, he must inform the relevant Management Office, with as much information as possible. The Company will advise and assist the Master based on his reports. If the cargo by its characteristics appears to be restricted in the ‘free-flow ability’, this may affect the discharge rate, or cause hang-ups at the discharge port. Such cargo problems must be reported immediately to the relevant Management Office, and all parties will subsequently be notified. Efforts are to be made to keep ready for use, systems such as ‘Cardox’, or additional vibrators to minimise any expected delay.

Hosing down of certain types of cargo to clear hang-ups or build up with fresh water, is only permissible by consent, and the written permission of the consignee of the cargo, and after notifying the Company and all parties.

Related articles

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  2. Care of cargo during loading- Trimming pours

  3. Checklist for confirming stabilty and hull stress prior loading

  4. Bulk carrier loading manual

  5. Cargo and ballast handling guide

  6. Responsibility of ship during cargo operation

  7. Shipboard hazards & bulk carriers safety guideline

  8. Asymmetric cargo and ballast distribution for bulk carriers

  9. Cargo handling guidance for deck officers

  10. Ventilation requirement for bulk cargo loaded

  11. Preventive measures against cargo which may liquefy

  12. How to plan cargo discharge in a safe manner ?

  13. Cargo damage survey guideline

Our detail pages illustrated many safety aspects of Bulk carrier

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Related information

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  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

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  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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