While in ocean transit, the COASTAL DRILLER has a roll period of 9 seconds. What is the largest angle each side of vertical that does not exceed the design limits of the legs in good weather?
• Relationship between roll period and stiffness/GM (metacentric height) of the unit • How design limits for leg stresses are linked to maximum safe roll angle in good weather • Why a longer roll period generally means a different allowable roll angle than a very short, “stiff” roll
• Compare what a 9‑second roll period tells you about how quickly and violently the unit is rolling—would that normally allow a larger or smaller angle before leg stresses become critical? • Think about typical "good weather" operating limits for a MODU’s legs: are they usually just a few degrees, or can they be quite large before design limits are reached? • Look at the answer choices and ask yourself which value is most consistent with a moderate roll period and a conservative design limit for structural safety of the legs.
• Be sure you understand that roll period alone doesn’t give the angle; it’s used with design criteria/curves or tables provided for that specific unit (like COASTAL DRILLER). • Confirm that in good weather the unit would not be operating near extreme survival angles, so the limit should be conservative but realistic. • Before choosing, eliminate any angle that seems unrealistically small for normal good‑weather operations or too large to keep leg stresses within design limits.
No comments yet
Be the first to share your thoughts!