The COASTAL DRILLER is loaded as shown in the Sample Load Form #1 (Rig Move). What is the margin on the maximum allowable KG if winds increase to greater than 70 knots, and the TOC is changed to the recommended value?
• Maximum allowable KG and how it changes with wind speed criteria on a mobile offshore drilling unit (MODU) stability booklet or exam stability tables • How the Table of Operating Conditions (TOC) recommended value affects the limiting KG for that specific condition • How to compute margin: difference between actual KG (or adjusted TOC KG) and the maximum allowable KG for the specified wind
• Look at the stability data or load form for winds greater than 70 knots and identify the corresponding maximum allowable KG for that wind speed and operating condition. • Compare the current (or recommended) TOC KG with that maximum allowable KG and think about whether the vessel is right at the limit, significantly below it, or unrealistically far from it. • Ask yourself: does a margin of several dozen feet between actual KG and allowable KG sound realistic for a MODU, or should the margin be much smaller?
• Verify the correct column or table for wind speeds greater than 70 knots (not the 50-knot or transit condition). • Confirm you are using the recommended TOC value for KG (or vertical center of gravity) from the problem statement or load form, not an intermediate or initial value. • Carefully calculate margin = (maximum allowable KG) − (actual/recommended KG) and double-check your subtraction and units (feet).
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