The offshore supply vessel to which you are assigned is fitted with reversing reduction gears equipped with airflex pneumatic tire-type friction clutches. With the bridge in control of the main engines, you hear unusual screeching noises coming from the clutches, but only when transitioning from one direction to the other. Given the situation of changing direction from ahead to astern as an example, what is the most likely cause?
• Reversing reduction gears and how airflex pneumatic tire-type friction clutches transfer torque when changing direction • What happens to clutch engagement surfaces if they are asked to pick up load too quickly vs. after a brief unloading period • How the EOT (Engine Order Telegraph) handle sequence affects clutch slip, heat, and noise when shifting from ahead to astern
• Think about what the clutch is doing right at the moment of direction change: does it need a brief time unloaded, or can you go almost directly from ahead to astern without a pause? • In which situation is the clutch more likely to slip and screech: when it has too much time to equalize speed, or when it is forced to grab onto a still-rotating component? • Compare the sequences: ahead → neutral → astern and ahead → astern → neutral. Which timing (too long vs. too short in neutral/idle) would cause the greatest speed difference between clutch parts when they try to engage?
• Verify which choice describes a very short pause (or almost no pause) between powered ahead and powered astern on the clutch. • Identify which sequence keeps the shafts/components spinning faster when the opposite direction clutch is asked to engage. • Ask yourself: a tire-type friction clutch screech usually comes from slip due to high relative speed or load at engagement, not from resting too long in neutral. Which option matches that?
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