Self- unloading bulk carriers discharging preparations

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Self- unloading bulk carriers discharging preparations

Self-unloading vessels can reduce a cargos 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.

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:

Personal safety
Discharge Plan
Dipping sequence
Start up gate numbers
Tides and Critical low water period
Rotation of Discharge Personnel teams.
Discharge rates.
Store facility characteristics
Dust suppression
Communications testing

Prior to arrival discharge port

Points to be taken into consideration are:

Inspection of the entire SUL system.
Checking for water leaks, and accumulations in the tunnel.
Water accumulation affecting the vessels trim.
Use of the forward trash pumps.
Reference to the voyage instructions and port information, for planning the vessels position at the berth.
Rate of Discharge.
Discharge plan.
Discharge teams, pre-discharging meeting.
Distribution plans.
Inspection of the entire system for fallen objects.
System simulation.
Emergency stops.
Dust suppression methods and tools prepared for use.
Ensuring that the luffing piston is clean.
That the gantry battery is charged.
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:

Restrictions of the port.
Shore reception/take away facility.
Expected duration of discharge.
Time of low water.
Dipping for bodily rise.
The vessels expected draft and trim at the time of low water.
The limits of the bending moments.
Time to commence de-ballasting and the sequence.
Setting limits for the vessels trim.
Removal of the boom tie-downs
Conducting the draft survey.
Checking that there are no obstructions present.
Swinging out the boom, and checking that no persons or cars are under the boom sweep.
Using the heeling tanks not Double Bottom Tanks.
Increase of draft due to list.
Assigning a person for depths at berth.
Completion of the pre-discharge checklist.
Completion of the ship-shore checklist.
Checking and establishing communications.
Checking the Umbilical chord.
Clearance from Customs.
Critical period for grounding at low water.
Cracking the hatches open.
List lights on, and vessel upright.
Gradual commencement of discharge.
Slowly increasing rate, and keeping in touch with shore.
If open pile ask for pile height.
Ensuring discharge plan is being complied with.
Directing the gate operators for draining, and use of vibrators.
Hammering if required.
Port logs and time sheets.
Shovelling spills.

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.

Communications

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.

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