Which of the following comes earliest in the start-up sequence of a steam turbine?

• A. Open the steam inlet valve slightly to start the turbine rolling.
• B. Close the casing drain valve and ensure the casing drain steam trap remains in service.
• C. Reset the overspeed trip.
• D. Manually test the overspeed trip.

Answer: (C)

Starting a steam turbine safely hinges on having protection devices ready to act. The overspeed trip is the key safeguard that must be in a normal, reset state before any attempting to start. If the trip remains tripped, the turbine will not start and will immediately trip as soon as speed is commanded to rise. Resetting the overspeed trip clears that protective condition and allows the start sequence to proceed, because the control system needs a ready protection mechanism to respond correctly during acceleration.

Once the overspeed protection is reset, the other steps follow in the standard sequence: you bring the turbine up gradually by opening the steam inlet valve, ensure condensate drains and traps are functioning to prevent accumulation of water or steam leakage, and any verification of the trip mechanism is performed as part of routine maintenance—separate from the normal start-up.