A starting device for a gas turbine

• A. is also called "barring gear"
• B. must be an electric motor
• C. keeps rotating the turbine shaft until the turbine is up to full load
• D. is necessary for all gas turbines

Answer: (D)

Starting a gas turbine requires bringing the rotor up to speed so the compressor can draw air and combustion can be sustained. At rest, there’s effectively no initial torque to start turning the shaft, so an external starting device must provide the first rotation. This starter can be electric, pneumatic, or hydraulic depending on the design, and once the turbine reaches the speed where ignition can occur, fuel is fired and the turbine continues to accelerate on its own while the starter disengages. A barring gear is used mainly to rotate the rotor slowly during maintenance or lubrication checks, not to start the engine. Some units may use different starter types, but the essential idea is that some starting mechanism is required for all gas turbines.