Because there is a possibility of fuel oil being discharged overboard from a full fuel oil tank, it is decided to transfer 25 kips from tank 14 to tank 13. See COASTAL DRILLER Sample Load Form Number 1 (Rig Move). What would be the change in transverse free surface moments?
• Free surface effect and how slack tanks create transverse free surface moments • How transferring weight between tanks on the same level can change total free surface moment even if total weight stays the same • Using the rig’s Sample Load Form / tank table for transverse FSM values per tank and per loading condition
• When you move 25 kips from tank 14 to tank 13, what happens to the free surface in each tank: does one tank go from slack to full or from full to slack? • Does a full tank contribute free surface moment? How about a slack (partially filled) tank? Apply that to both tank 13 and 14 before and after transfer. • On the Sample Load Form, which column or row shows the transverse free surface moment for each tank at the given loading? How do you combine the before/after values to find the net change?
• Confirm from the load form whether tank 14 is initially slack or full, and what its FSM is before the transfer • Confirm from the load form whether tank 13 is initially slack or empty, and what its FSM becomes after adding 25 kips • Carefully compute: Change in total FSM = (FSM after) − (FSM before), watching signs and making sure you use the correct units (ft-kips)
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