Steam Turbine Performance

Bhavik Kasundra · March 24, 2024

Engineering

Steam Turbine Performance

Performance Monitoring

  • Monitor Plant Heat balance and Individual Equipment Heat balance
  • Plant Thermodynamic Cycle
  • Parameters
    • Steam Inlet Pressure, Temperature, Flow
    • Feed water Flow, Temp
    • Cooling Water inlet and Outlet Temperature
    • Condenser Pressure
    • Generator Power & Power Factor

Condition Monitoring

  • Mechanical Parameters
    • Vibrations
      • Radial (2 Proximity Probes in Orthogonal config; Shutdown parameter
      • Axial (2 Proximity Probe within thrust bearing) Shutdown parameter
      • Speed\Phase angle : Key-phasor transducer (once per turn signal for determining vibration phase and shaft rotative speed)
      • Casing Vibrations: seismic transducers on radial bearing housings **
      • Shaft Eccentricity: measure residual shaft bow under gravity sag
      • Excessive Bearing to Shaft Clearance
      • Support structure looseness
    • Oil Quality
      • Contamination
      • Shaft Scoring
      • Babbitt Material Loss
    • Temperature Monitoring
      • Bearing Babbitt Temperature
      • Bearing Housing or Shell Temp
    • What Else parameters Reflect condition?

Why Monitoring apart from Machinery Protection

  • Planning Shutdown
  • Inventory Management
  • Transition to predictive maintenance from preventive maintenance

Condition Monitoring of Lube Oil

  • Pressure distribution on lube oil film of a journal bearing
  • Degradation Mechanisms
    • Oxidation: Presence of oxygen reacts with oil and form carboxylic acids. Temp is critical factor (rate doubles with rise in 10 `C)
    • Thermal Degradation: Breakdown of Oil molecules by heat forming insoluble compounds (soft contaminants).

Tests for carried out to assess the condition of oil (ASTM, IP, DIN)

  • Kinematic Viscosity,
  • Water,
  • Insoluble particulates (What is particulates)
  • Acid number ?, Neutralization number
  • Ferrography, Rust
  • Foam, Air release,
  • Cleanliness code

Alarm level for turbine

Vibration data (from 1→ n)

Limit = Mean + 4Standard Deviation*

Instruments

  • Motion (Vibration, Rotor Eccentricity)
    • Eddy Current or Proximity Probes
    • Velocity Transducers
    • Shaft riders
    • accelerometers
  • Position (Wear, Rotor position, Casing Expansion, Differential Expansion, CV Position)
    • Eddy Current
    • LVDT
    • Linear Rotory Potentiometers
  • Speed (and Acceleration, Over Speed detection
    • Active or Passive Eddy Current Probes
  • Process (Bearing White Metal or Babbitt Temp, Shell diff. temp, Lube oil)
    • Thermocouples or
    • RTD
    • Oil Pressure : Piezoelectric Strain gauge pressure transducers

Study

  • Pressure distribution and principle of journal bearing

Twitter, Facebook