🔍 Key Concepts

• How a steam turbine rotor behaves when steam is secured while the ship is still moving through the water • The effect of astern steam on turbine and shaft rotation when the vessel has headway • Why a Prony brake and stern tube packing are not normal in‑service methods for stopping a main turbine rotor at sea

💭 Think About

• If the ship is still moving ahead through the water, what tends to happen to the turbine rotor and shaft when you simply secure all steam? • What condition inside the turbine does admitting astern steam create, and how does that influence the direction and speed of rotor rotation? • Which of the options is actually a performance/measurement or sealing adjustment, rather than an operational maneuver to control rotor speed underway?

✅ Before You Answer

• Identify which choice is a normal operating procedure used by engineering watchstanders at sea, not in a test stand or in port • Eliminate any option that would mainly affect shaft sealing or bearing load, rather than directly and safely control rotor rotation • Consider turbine manufacturer and engineering practice: which method prevents the rotor from windmilling when the ship still has headway?