Expanding steam into the wet region where moisture exceeds 14% causes severe liquid droplet impingement on the last-stage (L-0) rotating blades. Droplets condensed in stationary nozzle cascades strike rotating blades moving at 400 to 500 m/s tip speeds. The resulting water-hammer shockwaves (>1,000 MPa localized impact pressure) gouge and notch blade leading edges, causing catastrophic high-cycle fatigue blade fractures that throw fragments through the condenser shell. Always maintain throttle superheat or incorporate reheat stages.

Operating throttle-governed turbines below 40% to 50% rated capacity causes immense isenthalpic throttling pressure drops across the governor control valves. Steam expands into the first stage at severely degraded pressure and temperature without producing work. As illustrated by the Willans line, no-load steam consumption ($dot{m}_0$) remains constant, causing specific steam consumption (SSC) and Net Heat Rate to double. For cycling operations, specify sliding-pressure boilers or nozzle-governed control valves.

Sub-atmospheric condensing exhaust hoods rely on continuous gland steam sealing (1.05 to 1.15 bar a) and vacuum steam ejectors to evacuate non-condensable ambient air leaks. If gland steam regulation fails or turbine casing gaskets degrade, air leaks into the vacuum space. Non-condensable air blankets the outer tube surfaces of the condenser, slashing heat transfer coefficients by 80%. Condenser backpressure spikes from 0.06 bar to 0.20 bar a, cutting turbine power output by 10% to 15% and triggering high-exhaust-temperature trips.

Starting a cold turbine or failing to warm up and drain inlet steam piping traps condensate slugs that enter the steam chest. Liquid water droplets striking white-hot rotor discs at 3,000 to 3,600 RPM cause severe localized thermal quenching. The asymmetrical contraction bows the rotor shaft elastically, destroying labyrinth shaft seals, wiping babbitt journal bearings, and inducing destructive vibration tripouts. Automatic drain pots with steam trap level interlocks must be installed on all main steam lines.

At ultra-low condenser pressures (e.g. cold winter cooling water delivering 0.03 bar a), steam specific volume balloons past 35 m³/kg. If the exhaust annulus area ($A_{ann}$) of the last stage is too small, the steam reaches sonic velocity (Mach 1.0). Once sonic choking occurs, lowering condenser pressure further produces zero additional power output, creating intense shockwave buffeting, high-frequency blade vibration, and excessive leaving loss energy dissipation.