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Preparation for discharge cargo oil in tanker vessel

Preparation of the Cargo Plan: The Chief Officer shall prepare a detailed cargo oil discharge plan before the arrival/ discharge port. The discharge plan shall be posted in the CCR at a conspicuous location, and distributed to all personnel directly involved in the discharge operation. During cargo operations a potential hazard exists: The discharge plan should be signed to confirm that personnel has read and fully understood the procedure. The Chief Officer shall also prepare a watch schedule and Person in-Charge list for oil transfer operations for the discharge operation. Before commencement of discharge operation, the Chief Officer shall conduct a "Pre transfer cargo safety meeting" with all the concerned crew and shall have a duty officer read aloud such discharge plan to all the attending officers and crew.
Unique details, port requirements, and special precautions or procedures should be discussed with all personnel involved in the discharge operation.

containerships operational matters
Oil Tanker Safety Guide

Before the commencement of the discharge, the cargo pump "emergency stop trips" must be tested. This test is to be conducted within 24 hours of expected cargo operations. In vessels fitted with an inert gas system, usually, only inert gas must be permitted to enter the space displaced by the discharged cargo (this is dependent on the shipment in question and port regulations). The pressure/vacuum valves must be set to allow air to enter the tank in the event of an inert gas plant failure to avoid damage to the tank structure while pumps are being stopped.

One Person must be delegated to keep watch within sight of the manifold area at times throughout discharge. If an incident at the manifold occurs, such as a burst pipe or failure of the manifold connection, the cargo pumps must be "tripped" first, and the Emergency Alarms sounded. The gangway watchman may perform this duty. If the Person delegated to watch the manifold area is a rating, he must be instructed in the course of action to be taken in the event of an emergency before commencing his watch. Tank hatches must not be opened, or ullage plugs left open during discharge.

Preparation for Cargo Equipment: Cargo oil transfer pumps and IGS should be well prepared for use prior to arrival at discharge port terminal.

Cargo Oil Transfer Check Lists

The Chief officer shall complete the following check lists prior to, during and upon completion of cargo oil transfer operations. The Chief Officer, after confirmation, shall affix his signature on the detailed checklist. The Master shall then sign on the completed "Tanker Discharging Checklist." If there is a multi-port discharge, the pre-arrival tests, as listed herein, can be completed before the arrival at the first port.
Display of Warning Notices and Signs should be taken into account

Hose Connection: The Chief Officer or deck duty officer must be in attendance during the connection of cargo oil transfer arms/hoses.

Cargo Oil Transfer Meetings with Terminal representative: The Master, Chief Engineer, and Chief Officer must attend and carry out a "pre-transfer cargo safety meeting" with the shore facility representative to ensure full agreement with the cargo oil discharge plan and to agree on the method of communication during emergencies. The "Ship/Shore Safety Check List" or relevant "Ship to Ship Transfer Check List" must be completed and signed for in agreement by both parties after successful completion of safety checks and confirmation and before starting of operations.

Ullage measurement and Cargo Quantity Calculation: Ullage and Temperature measurement, Water measurement, and Sampling are carried out by the terminal side or surveyors. Normally, one watch Officer shall attend the measurement and assist in calculating the cargo quantity. Ensure that all ullage ports (vapor locks) and other openings have been Closed after the measurement and before the start of operations.

Lining up Pipelines and Valves:

Prepare the lines between tanks and pumps after the completion of ullage measurement. Tanks not to be discharged are to be suitably marked and protected from accidental miss-operation. Carry out the separator's filling with the utmost caution and avoid" Liquid Hammer." Ensure through the passage of vapor to fill separator evenly. Before commencing, discharge the cargo tank line and pump room valves to be set as per the Plan for the start of discharge. Use the ship specific 'Valve Checklist" prudently. Valves not in use should be secured and lashed shut. Line / Valve settings are to be supervised and checked by the Watch-Officer and re-confirmed by the Chief Mate. The order for opening of manifold valve shall be under the chief officer's permission. On the opening of the manifold valves, the manifold pressure shall be monitored regularly. Operate major valves as per the terminal representative's order.

Preventing Accidental Spillages

Ships personnel must maintain a close watch throughout cargo operations to ensure that any cargo escapes do not go unnoticed. In this respect, it is essential that all valves are closed if not in use. Personnel operating inert gas plants must be aware that, with some inert gas generators, there is a risk of oil pollution via the cooling water discharge when the burner does not ignite in its start cycle. Where such uncertainty exists, it is better to start the generator before the vessel arrives at the berth. Cargo or bunker tanks that have been "topped-off" must be checked frequently during the remaining loading operations to avoid an overflow. If accidental spillage or leakage of cargo occurs during any operation, the relevant operation must be stopped immediately until the cause has been established and the defect corrected.

All Company vessels are supplied with an approved outfit of clean-up materials specified under the U.S. Oil Pollution Act of 1990 and MARPOL 73/78. MARPOL 73/78 is the International Convention for the Prevention of Pollution from Ships, 1973, modified by the Protocol of 1978. ("MARPOL" is short for marine pollution and 73/78 short for the years 1973 and 1978.) Annex I.

Clean up materials must be available at the bunker or cargo manifold, for the prompt removal of any spillage on deck. Portable salvage pumps must be deployed at the after the end of each side of the main deck. Chemicals used for clean up on deck must not be allowed to enter the water unless permission has been obtained from the harbour authorities. Should an oil spill accident occur, then the appropriate authorities, as detailed in the vessel's Oil Spill Response Plan (U.S. waters) or SOPEP (other liquids) must immediately be informed. The contact sheet required by the Plan must be completed before arrival in port.
deepwell cargo pump
Fig: deepwell cargo pump

Deepwell cargo pumps – Electrically- or hydraulically-driven cargo pumps used in tanker cargo pumping system. A deep well pump is submerged in the fluid pumping with its impeller placed in a well in the tank top, which means that it is only suitable for double-hulled tankers. The advantage is that tank stripping is easier. Each cargo tank has its pump unit.

An electric pump is connected via an intermediate shaft to an explosion-proof electric motor located on the main deck. Hydraulically driven pumps of this type are more popular on chemical tankers. In this option, electrically-driven hydraulic power packs need to be fitted. Besides, piping is needed to transmit the hydraulic fluid pressure from the power pack to the pump unit located at the tank.

Deepwell cargo pumps offer several improvements, including the elimination of the traditional pumproom, more significant pumping and stripping efficiency, more flexible cargo segregation, and corrosion-resistant stainless steel component construction.
Photo courtesy of Wärtsilä Corporation

Personnel arrangement at beginning of operations
: In principle, for the start-up of operations, all deck crew shall be in attendance and distributed as per the chief officer's instruction.

Onboard announcement: Have the crew know the beginning of operations to call their attention to smoking, fire, designated passage, and other matters.

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