🔍 Key Concepts

• Function of a jacking (turning) gear on a steam turbine shaft • Conditions when a turbine rotor must not remain stopped in one position (thermal distortion, shaft bowing) • Difference between slow turning / positioning vs. producing power or thrust

💭 Think About

• Think about whether jacking gear is used to make power, or only to slowly rotate and position the shaft. Which choices describe slow, controlled rotation versus driving the ship? • Consider when a stopped, hot turbine might be at risk of damage if it is not turned. Which option best fits that protective purpose? • Ask yourself: in which situation would the main propulsion be engaged normally, and in which situation would special low-speed turning gear be used instead?

✅ Before You Answer

• Identify which options describe normal propulsion operations (making ahead or astern thrust) and which describe a maintenance/protective operation. • Check which choice involves slow, intermittent rotation rather than continuous high-speed running. • Eliminate any option that suggests the jacking gear is used for extra power or maneuvering thrust rather than for protection or inspection.