The Ultimate Guide to Cargo Operations for Tankers
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| Real Life Incident “Mellitah condensate is ab highly volatile cargo with peculiar properties. Its viscosity is very low. One of the tankers loaded Mellitah condensate from Libya. The vessel topped up 2 tanks, in the end, using 2 independent lines for P and P cargo tanks. As the loading stopped and the manifold draining commenced, the crossover valve, which was at least 3 meters above the level of cargo in tanks between the lines of P and P, was also opened. After some time it was noticed that the syphon effect between 117. l Marine Insight the tanks P and P had been created and it has transferred almost m of cargo from P to Pi iThis could have turned into ab horrendous mistake if it had been two different parcels or 2 different grades.” As the oxygen content reduces to 8% or less, reduce the inert gas pressure to 150 mm WG and close the gas freeing lid. When inerting for all tanks is completed, raise the line and inert gas pressure in the tank to mm WG. Shutdown the plant and close the main deck isolation valve. Confirm that all the gas freeing lids are also closed. After opening the deck main isolation valve, the inert gas generator must be started. The control of the generator is to betaken in cargo control room (CCR).” Cargo Operations for Tanker I 118. Purging is carried out to remove hydrocarbon vapors present in the tank for eliminating any risk of fire. It is also used to remove flammable mixture formed inside the tanks whenever oxygen is introduced into the tanks. This is usually done after tank cleaning operations. 119. l Marine Insight The cargo tanks maybe purged with inert gas to reduce the concentration of the hydrocarbon gas inside the tank atmosphere. Purge pipes, with proper flame screens, shall befitted, where provided. Procedure for purging is as follows • Follow the procedures as laid out in the operation and equipment manual • Ensure that all the cargo tank openings on deck are closed and secured • Open the gas freeing ports on the first set of tanks to be purged. For e.g. 1 Port and 1 Starboard • Open the inert gas inlet valve only for the same set, and the inlets to rest all tanks should be closed Download 6.36 Mb. Share with your friends:
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