Turbine Construction, Components, and Auxiliary Systems
Core concepts
Know the major assemblies: casing, rotor, diaphragms or nozzle rings, stationary and rotating blades, seals, bearings, and the thrust balance arrangement. Understand how thermal expansion is accommodated - sliding keys, catenary supports, and axial clearance at the thrust bearing. Candidates must recognize gland steam sealing, the surface condenser and its air removal (vacuum pump or ejector), feedwater heating, and the extraction system. For gas turbines, know the compressor, combustor, transition piece, and turbine section, plus cooling-air paths for hot-gas-path parts.
Traps
Questions often test whether a component is stationary or rotating, or which system supplies sealing steam at which load. A frequent trap: the turning gear is for preventing rotor bow during cooldown, not for starting the unit. Another is confusing the thrust bearing (axial position) with the journal bearing (radial support). Remember that the condenser is both a heat sink and a vacuum boundary; air in-leakage raises back pressure and reduces output.
Worked rule of thumb
For seal steam, a simple rule: gland steam pressure should sit slightly above atmospheric but below the lowest casing pressure at the seal, so air is excluded and steam does not escape. If a question gives seal pressure above casing pressure at the high-pressure end, expect leakage outward; below atmospheric at the low-pressure end, expect air ingress.
Exam focus
Be able to trace a system: from boiler or combustor through the turbine to condenser and back, naming each auxiliary and its failure consequence. Know that loss of bearing oil, loss of vacuum, or loss of cooling water each forces a different protective response.