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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 prior to 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 have read and fully understood the plan. The Chief Officer shall also prepare a watch schedule and Person in-Charge list for oil transfer operations for the discharge operation.

Prior to 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.
Special details, port requirements and special precautions or procedures should be discussed with all personnel involved in the discharge operation.

Before commencement of the discharge, the cargo pump emergency stop trips are to be tested. This test is to be conducted within 24 hours of expected cargo operations.

In vessels fitted with an inert gas system, normally only inert gas must be permitted to enter the space displaced by the discharged cargo (this is dependent on the cargo 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 whilst 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 he commences 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 related checklist. The Master, shall then sign on the completed “Tanker Discharging Checklist”.

Oil tanker at sea

If there is to be a multi-port discharge, the pre-arrival tests, as listed herein, can be completed before the arrival at the first port.
• “Crude Oil Washing Checklist” .
• “Ship / Shore Safety Checklist”
• “Double Hull Operation/COT (Cargo Oil Tank) Monitoring Record”
• “Ship to Ship Transfer Checklist” , as required.

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 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 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 prior to 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 to calculate the cargo quantity. Ensure that all ullage ports (vapor locks) and other openings have been Closed after the measurement and prior to 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 filling of the separator with utmost caution, taking care to avoid ”Liquid Hammer”. Ensure through passage of vapor so as to fill separator evenly.

Prior to commencing discharge the cargo tank line and pump room valves to be set as per the plan for 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 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 escape of cargo does 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 a risk exists it is better to start the generator before the vessel arrives at the berth.

Cargo or bunker tanks which have been “topped-off” must be checked frequently during the remaining loading operations to avoid an overflow. If an 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 as 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 as 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 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 take place then the appropriate authorities, as detailed in the vessel’s Oil Spill Response Plan (US waters), or SOPEP (other waters) must immediately be informed. The contact sheet required by the Plan must be completed prior to 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 deepwell pump is submerged in the fluid that it is pumping with its impeller placed in a well in the tanktop, which means that it is only suitable for double-hulled tankers. The advantage is that tank stripping is easier. Each cargo tank has its own 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. In addition, 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 a number of improvements, including the elimination of the traditional pumproom, greater 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 chief officer’s instruction.

Onboard announcement

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





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