While the COASTAL DRILLER is in transit at a draft of 10 feet 6 inches, a severe storm is predicted within 12 hours. VM are 541,257 ft-kips, FSML are 32,000 ft-kips and FSMT are 24,000 ft-kips. How much should the KGL be lowered to satisfy the maximum allowable KG criteria?
• Free Surface Effect (FSE) and how it causes a virtual rise of the center of gravity (KG) • How virtual GM/VM and free surface moments (FSM) are used to check a maximum allowable KG or KGL criterion • Relationship between FSM, vessel displacement (or weight), and the change in KG/KGL
• How do the given VM, FSML, and FSMT values relate to the present stability condition of the vessel versus the required condition? • What formula links a change in free surface (or added weight/ballast) to a change in KG or KGL, and how can you rearrange it to solve for how much KG must be lowered? • Look at the magnitude of VM and total FSM. What does that tell you about whether a large or small adjustment in KGL is likely needed?
• Be clear on whether the question is asking for a change in KGL (longitudinal KG) or KG (vertical) and how the exam/course notes define KGL for this unit or rig type. • Verify how to combine FSML and FSMT (e.g., sum as total FSM if appropriate for this problem) before using them in any formula. • Double‑check your units: make sure VM and FSM are both in ft‑kips and that displacement/weight is in kips, so the change in KG/KGL comes out in feet.
No comments yet
Be the first to share your thoughts!