Power Plant Machinery Flashcards
7 cards from real CPM practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Power Plant Machinery flashcards as text
A boiler feed pump shows a sudden rise in noise and a drop in discharge pressure while suction pressure is low. What is the most likely cause?
Answer: Cavitation
Low suction pressure below NPSH required causes vapor bubbles that collapse noisily and reduce head.
What is the main purpose of the balancing drum or balance disc on a multistage boiler feed pump?
Answer: Offset axial hydraulic thrust
Balance devices counter the axial thrust produced by the pressure difference across the impellers.
On a steam turbine, which device trips the unit if shaft speed exceeds about 110% of rated speed?
Answer: Overspeed trip
The overspeed trip closes the stop valves when speed reaches its setpoint, typically around 110%.
Why is a steam turbine placed on turning gear after shutdown?
Answer: To prevent rotor bowing during cooldown
Slow rotation lets the rotor cool evenly and prevents thermal sag or bowing.
In a surface condenser, what does a gradual rise in backpressure with normal cooling water flow most often indicate?
Answer: Air in-leakage or tube fouling
Non-condensable gases and fouled tubes reduce heat transfer, raising condenser pressure.
Which device removes non-condensable gases from a power plant condenser?
Answer: Steam jet air ejector
Steam jet air ejectors or vacuum pumps draw air and non-condensables out to maintain vacuum.
What is the primary function of a deaerator in a steam cycle?
Answer: Remove dissolved oxygen and gases from feedwater
Deaerators heat feedwater to strip dissolved oxygen and CO2 that cause corrosion.