The Ultimate Guide to Cargo Operations for Tankers

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“For driving the eductor through slop tank in a closed cycle, one of the slop tanks is required to hold cargo of about 350 - m. Cargo Operations for Tanker I 86.
Eductors arrangement in Oil Tankers

line. Thus, the eductor strips the group and discharges the cargo into slop tank. Cargo eductor can be lined up as one of the three groups reaches completion. As the eductor develops the vacuum in the line, a compound gauge for suction indicates the suction pressure. When the suction pressure becomes zero, it indicates no or very less cargo. If the suction pressure is slightly negative, it indicates that cargo is still there. Developing high negative pressure, i.e. more than 1 bar inside the line by keeping valves closed is not
87. l Marine Insight recommended as on some old ships it has resulted in buckling of lines. By the time group yellow is being educted, the engine room can be notified to prepare steam for the stripper pump for warming up and making it ready for use. Before starting the stripper pump for line stripping, the suction and discharge lineup for stripper pump should be confirmed. This is because as the pump is a positive displacement pump it can develop enormous pressure in the discharge line. The stripper pump with the help of controlled strokes from CCR, strips the main cargo line and discharges the cargo through a smaller line known as Stripping Line. All the bottom and top crossovers to be kept open to strip the pump casings, separators, drain As the eductor removes remaining cargo from the tanks, if the cargo heating is in progress, it should be shutdown as soon as the tank gets empty or the cargo level will fall below the heating coils inside the tank. The main steam valve should be throttled as the demand for steam reduces Cargo Operations for Tanker I 88.

lines of COPs, bottom lines, and sections of bottom crossovers. While carrying outline stripping, a gooseneck valve arrangement is provided in the crossover section. The purpose of this assembly is that as the cargo in the line flows to the pump, the air enters the gooseneck assembly and fills the vacuum created by the pump.
89. l Marine Insight Air coming in from gooseneck assembly is a good indication that the stripper pump is working satisfactorily. Finally, as the cargo lines are stripped, the pump can be stopped slowly and the steam to the system can be shut. Initial process in strippin fot independent line system is as follows
• The feed pumps for the hydraulic power packs are started from the control panel
• As the feed pumps stabilize, the engine room can be advised to start the generators for using power packs. (Power packs are electrically driven pumps which drive hydraulic fluid into the pumps for running) The last group or line to be stripped should preferably be the one in which manifold arm is connected. The lesser are the number of turns and bends in a line the better is the performance of the pump. Hence keeping the manifold line as the last one enables the pump to strip tanks directly ashore without circulating them through the manifold crossover Cargo Operations for Tanker I 90.

• Generally, all 4 power packs can be used to run 6 pumps at a time
• As the engine room confirms to use power packs, the start button for the power pack can be pressed on the panel above. As the power pack starts, the green LED flickers and then stabilizes
• Similar procedure to be followed for the remaining three power packs
• The tanks can now be lined up for commencing discharge
• After starting the power packs, the pressure is set for the hydraulic oil which is running in the system. The system pressure decides the maximum pressure to be supplied to drive the pumps
91. l Marine Insight
• System pressure is to be kept 15 - 20 bars higher than the required pressure for pumps. Thus, to increase pumps driving pressure, the system pressure should be raised first, and then the pumps driving pressure should be increased When changing over pumps, reduce the hydraulic pressure of all pumps to minimum or 120 bars, close the discharge valve of the pumps, and reduce their pressure to 0 bars. Slowly increase the pressure of the pumps which are to be started, keeping their discharge valves closed. As the discharge pressure of these pumps exceeds the manifold discharge pressure, open the discharge valves. As the valves are fully open, all the pumps which are running can again be increased to resume bulk discharge. DO NOT FORGET to increase system pressure before increasing the pumps pressure Cargo Operations for Tanker I 92.

As the power packs are now running, the deep well pumps can be started by moving the lever for the respective tanks which are planned for discharge initially. The pump assembly on deck is provided withal Marine Insight speed-torque controller valve, which can be used to control the pump pressure locally. This is also used to strip the cargo tanks from the deck. To transfer control locally on deck, set the system pressure to 120 bars and then reduce the pump pressure in CCR to 0 bars. Using the speed torque assembly, the pump can now be controlled locally to strip the tanks. After starting the power packs, the pressure is set for the hydraulic oil running in the system. The system pressure decides the maximum pressure to be supplied to drive the pumps. System pressure is to be kept 15 -20 bars higher than the required pressure for the pump Cargo Operations for Tanker I 94.

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