Main Turbine(MT3) Flashcards
What is the purpose of the Turbine Instrumentation and Protection System?
- Detect undesirable or dangerous operations conditions of the turbine generator
- Take appropriate actions
- Provide information to the operator about the detected conditions
What is the system designator for the Turbine Instrumentation and Protection System?
MT3
What components are housed within the Turbine Front Standard?
- Low Speed Switch off of the auxiliary rotor
- Main Oil Pump off of the auxiliary rotor
- Stub rotor(bolted to the main rotor)
- Mechanical Trip Lever
- Magnetic Speed Sensors
What is the design/purpose of the Low Speed Switch?
- Starts and engages the Turning Gear
- Auxiliary Shaft speed must be less than 1.5rpm
- Disabled(will not engage) above 100rpm
What is the design/purpose of the Main Oil Pump?
- Double suction, single stage centrifugal pump
- Driven off of the Stub Rotor
- Located in the Front Standard
What is the design/purpose of the Magnetic Speed Sensors?
- Mounted in the Front Standard
- Three used for EHC and Auxiliary Speed sensors
- A different sensor provides speed signal for turbine supervisory instruments
- Positioned around a toothed wheel, number of teeth is selected to give an electrical signal proportional to shaft speed
What is the design/purpose of the Shaft Grounding Device?
- Removes turbine shaft voltages and sends them to ground
- Prevents:
A. Lube oil breakdown
B. Pitting of bearing surfaces due to arcing - Located between the ‘C’ Low Pressure Turbine and the Generator on the exposed shaft
- Maid of a copper braid
What type of Instruments input into Turbine Supervisory Instrumentation and Controls?
- Thrust Bearing Wear Detector
- Thermocouples
- Eccentricity Detector
- Differential Expansion Detector
- Shell Expansion
- Vibration Detector
- Turbine Supervisory Instrumentation Panel
What is the design/purpose of the Thrust Bearing Wear Detector?
- Electronic proximity probes detect thrust bearing wear by sensing shaft movement
- Alarm generated at 20mils of movement(1/4 probes)
- Turbine trip generated at 42mils of movement(3/4 probes)
* the numbers are the same for both units*
What do the Turbine Thermocouples monitor?
1. Low Pressure Inlet Bowl A. Upper Hood B. Lower Hood C. Sense Inner Casing Temperature 2. Eighth Stage Extraction A. ‘D’ Extraction Steam B. 2 in the Upper Hood of each LP Turbine C. 2 in the Lower Hood of each LP Turbine 3. Bearing Oil and Metal Temperature
What is the design/purpose of the Eccentricity Detector?
- Measures shaft “straightness”
- Only accurate at low speeds
- Located in the Front Standard
What is the design/purpose of the Differential Expansion Detector?
- Indicates the difference in expansion between the rotor and the High Pressure Turbine Shell.
- Rotor expansion measured between the LP Turbine and the generator
- Proximity detectors mounted on both sides of a steel wheel which is part of the turbine rotor
Which component, rotor or shell, grows more rapidly during warmup and what is the concern?
- During warmup the rotor grows more rapidly than the casing
- If the rotor expands too fast when compared to the shell the moving parts could come in contact with the stationary parts
What is the design/purpose of the Shell Expansion Detector?
The Shell Expansion Detector measures high pressure turbine shell movement with respect to a stationary point on the foundation
What is the design/purpose of the Turbine Vibration Detectors?
- Two vibration assemblies per bearing
- Two vibration sensor in each assembly
- Shaft relative motion sensor - measures the amount of shaft movement relative to the bearing
- Bearing Cap Motion Sensor - measures the level of vibration of the baring cap
