If the MFP turning gear is not used before startup, what potential issue can arise?

Using the turning gear in a main feedwater pump (MFP) is vital for ensuring proper mechanical and thermal conditions of the turbine prior to startup. When the turning gear is not engaged, the rotor may experience uneven heating during startup because it may not be uniformly rotated. This uneven heating can lead to thermal expansion that is not consistent throughout the turbine components.

The result of this uneven thermal expansion can cause the turbine to "bow," or warp slightly, as different sections of the rotor expand at different rates. This bowing can result in misalignment and potentially lead to severe operational issues, damage to the bearings, or even catastrophic failure of the turbine if not addressed properly.

The importance of pre-start procedures, including the use of turning gear, cannot be overstated. It ensures that components are adequately lubricated and prevents mechanical stresses that can occur due to temperature differentials. Maintaining uniform conditions before initiating turbine operation is crucial for the longevity and safety of the equipment.