While the COASTAL DRILLER is in a normal transit, the roll period is 9 seconds. What is the limiting angle of roll which does not exceed the design limits of the legs?
• Roll period and stability relationship for mobile offshore drilling units (MODUs) like COASTAL DRILLER • Manufacturer or design operating limits for leg stresses vs. roll angle • How longer vs. shorter roll periods generally relate to allowable roll angles in design guidance tables
• How would a 9‑second roll period compare to a very quick, snappy roll in terms of leg stresses and comfort? Would that suggest a very small or somewhat moderate limiting roll angle? • If you imagine the design engineers establishing a safe operating envelope, would they likely allow a large, medium, or very small roll angle before reaching leg design limits during normal transit? • Look at the answer choices: which angle best matches a conservative but still practical limit for leg stresses on a jack‑up in transit with a 9‑second roll period?
• Verify what typical limiting roll angles for jack‑up leg design are in transit conditions for the exam references you are using (often provided in tables or curves). • Check whether the exam materials link specific roll periods (e.g., 7 s, 9 s, 11 s) to particular limiting roll angles. • Confirm that the option you choose reflects a conservative design limit, not what might feel comfortable to people onboard.
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