5.44 MULTIPLE PORT OR DOCK DISCHARGES

The cargo may be designated for discharge at more than one dock or port. This intention will normally be indicated in the original loading orders, but may not be received until the ship is making its loaded passage. How the chief officer arranges the cargo to permit a multi-port discharge depends on the nature of the cargo.

5.44.1 Single grade cargo
When the cargo is a single grade, the chief officer need only calculate a discharge plan which offloads the designated quantity of cargo at the first port and leaves the tanker with acceptable trim, stress and transverse stability conditions for the passage to the second port.
The offloading programme for the first port should provide enough trim for stripping the discharged tanks to a consolidation or slop tank, however the trim should be limited to the maximum for which volume corrections are provided in the ship's calibration tables.
If the vessel is discharging heated cargo, all discharged tanks should be stripped. Adequate trim should be provided for good drainage. After discharge is complete, cargo may be gravitated or pumped from an aft tank to a forward tank to adjust the trim for the second part of the loaded passage.
With unheated cargo, the discharge may be completed without stripping tanks, maintaining the trim near even-keel and leaving sufficient cargo in the tanks discharged so that the cargo volumes can be accurately measured.

5.44.2 Multi-grade cargoes
When a tanker carrying a multi-grade cargo is ordered to conduct a two or three port discharge, the problem of planning the cargo loading arrangement (see section 2.20), is compounded by the need to achieve acceptable stability, trim and stress conditions during the passage(s) between discharge ports. This additional requirement may indicate the need of a different arrangement than would otherwise be used and may require some consultation with the shipper to modify the quantities and arrangement of the cargo parcels. The SBT tanks may be used, if hull stresses permit, to assist with the trimming of the ship after discharge at the first berth. Correct separation of cargo grades and protection of cargo quality remain the most important considerations.
When the ship has been loaded for a single port discharge and the orders are changed en route to offload at two or more terminals, the chief officer may discover that it is impossible to complete the first discharge with acceptable stability, stress, or trim for the voyage to the next port. In this case, he must develop a two step discharge plan which safely discharges the first parcel(s), then transfers cargo within the ship to achieve acceptable stress, trim and stability for the following passage.
The cargo transfer programme must be approved by the shipper and owners before it is carried out. After the first parcel is discharged, the ship must be gauged by an independent inspector to provide a record of cargo discharged and cargo on board after discharge. Cargo is then transferred within the ship as agreed and the independent inspector again gauges the ship to provide a report of cargo on board at departure. Ship's pipeline volumes must be properly accounted for in this report.

5.44.3 In-port movements
The hull bending and stress limitations are more stringent for a tanker at sea than for the ship in port. If the multiple dock discharge point delivery involves only a shift within a port, (as opposed to a voyage between ports), then only the harbour stress limitations apply. The ship need only have suitable trim and list for un-berthing and manoeuvring to the next terminal.