Startup, Shutdown, and Normal Operation Procedures
Core concepts
Startup is a controlled thermal ramp. Candidates must understand pre-start checks, lube oil and seal oil establishment, turning-gear operation, gland seal supply, condenser vacuum raising, and the difference between hot, warm, and cold starts. Know the purpose of slow rolling, soak periods, and controlled acceleration through critical speeds. Understand that thermal stress, not speed alone, limits loading rate: casing and rotor surface-to-center temperature difference drives stress. During normal operation, monitor bearing temperatures, vibration, axial displacement, differential expansion, and steam or gas temperatures.
Traps
Questions often ask why a unit is held at a soak temperature - the answer is to equalize metal temperature, not to warm the steam. Another trap is the critical speed: passing through it quickly is correct; dwelling is dangerous. For shutdown, distinguish normal controlled cooldown from a trip, and remember that turning gear engages after the rotor stops to prevent bowing. Do not confuse the order of operations: vacuum is established before steam admission, and broken by after steam is off.
Worked rule of thumb
A common guidance is to limit rotor-to-casing differential expansion and keep heating or cooling rates within the manufacturer's curve, often a few degrees per minute. If a question offers a fast ramp that exceeds the differential expansion alarm, the correct answer is to hold load and let temperatures equalize rather than accelerate further.
Exam focus
Be ready to order a startup sequence and to identify which parameter would stop or hold a load increase.