The Ultimate Guide to Cargo Operations for Tankers
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| Real Life Incident “A vessel loaded Condensate as cargo from Mellitah, Libya. As the ship sailed out and reached Suez Canal the next day, the deck crew noticed cargo leaking from manifolds and drop valves. The line was highly pressurized up to 10 bars. Immediately the tank valves were opened and the pressure built up in the line was released into cargo tanks. Mellitah Condensate is ab highly volatile cargo. As the lines were drained after loading, the remaining cargo in lines expanded due to heat and thus pressurized the line.” While loading from an independent line system, each line leads to a particular set of tanks. However, all these lines are connected to each other on the deck with the help of crossover valves. Thus, using the crossovers on deck one line can be used to load all tanks. The operational procedure for loading in this kind of system is quite similar to the closed-loop system with the only difference that the former uses deck crossovers and the later uses bottom crossovers. 45. l Marine Insight On completion of loading, during sailing all the cargo line crossovers, drop valves and manifold crossovers must be kept open to accommodate any excess pressure built up in the line due to change in temperature Cargo Operations for Tanker I 46. Duties of Deck Watch Officer and Crew • During the ongoing loading operation, the essential responsibility of deck watch is to keep an eye on oil leaks in the piping connections and near the tanks where oil is being loaded (onboard and overboard. More care to betaken during initial stages of operation and when the topping up is being performed • During loading operations, watch oil loading pressure all the time, and monitor parts where oil is likely to leak. Excessive vibrations on piping systems must be attended immediately • Cargo leakage, however small, shall be paid attention to at an early stage of operations. Leakages from the piping system, joints, and valves should be monitored • Duty watch person must ensure the oil is being filled only in selected tanks by checking soundings of other unused tanks 47. l Marine Insight Checking Leakages in Cargo Pipes Cargo Operations for Tanker I 48. changed-over • The chief officer will decide when the crew assigned the cargo watch may dismiss normally done once the full loading rate is reached and all cargo confirmation reports are received from different stations • Ballasting or de-ballasting operation to be carried out as needed. Before carrying out the operation, berth (Loading) Masters permission must betaken by the chief officer or master • De-ballasting is usually done just before the cargo tank level reaches near topping operation. • Single buoy mooring position monitoring shall be carried out throughout the operation • Do continuous monitoring of the oil level of the loading tanks until the shore flow rate settles down • The cargo manifold back pressure to be monitored frequently and more emphasis to be given when the valves or tanks are being 49. l Marine Insight Cargo Operations for Tanker I 50. Checking Ullage of Cargo Tank • Chief officer must ensure enough personnel are available on deck during the topping off operation • A portable hydraulic pump must be readily available on deck complete with extra oil and hoses, in case of a failure in the valve operating system During Completion of Operation • Topping off is done once the cargo loading is about to finish. The topping off method must be mentioned on the cargo loading plan by the chief officer stating the maximum permitted topping off rate • The duty deck officer should keep a check on the quantity and rate of cargo loading, and calculate the timing for informing the shore terminal in advance for topping off operation • Before commencement of topping off operation, the duty watch on deck must check all the gauges and level indicators to confirm the accuracy of the CCR tank gauges 51. l Marine Insight Cargo Operations for Tanker I 52. Installing Portable FRAMO pump shore terminal are to be drained properly. The draining process should be carried out in the presence of a responsible ship officer who will operate the drain valves, keeping the chief officer informed about the operation • Post completion of cargo loading operation, the Mast riser, and other available venting systems must be closed After Completion of the Loading operation • Once the terminal confirms the completion of cargo operation, the duty officer should make sure the manifold gate valves are closed • Cargo lines can become over pressurized and thus care should betaken to ensure that they do not become over pressurized due to high ambient temperatures • Post completion of cargo loading operation, the Mast riser and other available venting systems must be closed • The tank pressure must constantly be monitored to ensure no over-pressurization is in the system • The articulated arm and hoses coming from the 53. l Marine Insight Cargo Operations for Tanker I 54. Draining of Articulated Arms Records and paperwork during cargo loading Following items shall be recorded in Tanker Cargo Log Book on an hourly basis or as specified in the SMS of the ship • The terminal loading rate to be compared with actual ship loading rate • The crew must record the comparisons of loaded cargo figures, i.e. the total cargo currently onboard the ship and total cargo figure loaded on the vessel stated by the shore • Any difference in the records must be investigated and the discrepancy to be reported to the chief officer • Record of Manifold Pressure / Temperature at • Once the draining operation is finished, all tanks and vent valves to be shut • The connection to be isolated and depressurised from the internal cargo tank IG pressure • The remaining cargo in the ship's pipelines to be dropped in the tank by gravity • The duty officer must note down the temperature and ullage in each tank to calculate the total loaded cargo quantity • On completion of gauging and sampling, all ullage ports and other tank openings needs to be shut • The Inert Gas System recorder shall be switched onto record and monitor the cargo tanks pressure 55. l Marine Insight Cargo Operations for Tanker I 56. It is mentioned in the Voyage Orders that the vessel should maintain a pressure of 100 Psi at the manifold or complete the discharge operations within 24 hours. These instructions are critical with regards to the pumping capacity of the vessel. Also, the discharging plan has to be prepared accordingly to ensure compliance and to avoid extravagant claims arising due to delay. The above-mentioned plans imply that bulk discharge, stripping or crude oil washing, educting of cargo tanks, and line stripping are to be planned effectively and chronologically in such an order that there is no time lag between these operations. Unloading can be carried out using the cargo oil pumps (located in the pump room) in a closed loop system and an regular intervals (hourly) • Recordkeeping of draft and trim • Record of tank pressure • Recording of levels in tanks not being discharged • Stress and Stability of the vessel 57. l Marine Insight Download 6.36 Mb. Share with your friends:
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