单项选择题

An excessive amount of water is prevented from entering a vessel using a water lubricated stern tube bearing by the use of the （）.

A.propeller hub
B.lignum vitae
C.shaft packing
D.labyrinth seal

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Some vessels are equipped with a water lubricated stern...

单项选择题Some vessels are equipped with a water lubricated stern robeWhen at sea, operating under normal conditions, the water service valve from the ships saltwater system to the bearing should be （）.

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B.closed, and only slight leakage permitted across the shaft packing
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船舶辅助机械

An excessive amount of water is prevented from entering a vessel using a water lubricated stern tube bearing by the use of the （）.