Turbine Supervisory Instrumentation

Question 1

What is eccentricity measuring?

When will this parameter be measured?

Answer 1

Shaft bowing

< 600 rpm

Question 2

What probes are on every Generator journal bearing?

Answer 2

Proximity probe (2)(x and y)
Dual probe (1)(proximity and velocity)

Question 3

What happens at resonance frequency (critical speed) on a turbine?

Answer 3

Resonance is the objects natural frequency, when excited (spun at that frequency) vibration is amplified

Question 4

Describe different turbine supervisory instrumentation?

Answer 4

Vibration - shaking (dual)
Eccentricity - shaft bow (prox at end of shaft)
Differential expansion - rotor vs. casing (prox at angle)
Casing expansion - casing (lvdt)
Turbine Speed - (3 pickups)
Zero speed - (oil d/p)
Rotor position - thrust brng (prox)

Question 5

What does turbine supervisory channel do @ 600 rpm?

Answer 5

• starts / stops LOP
• removes eccentricity alarm
• activates vibration alarm

Question 6

What two indications can differential expansion tell you?

What do those indications mean?

Answer 6

Rotor short and Rotor long

short - casing is expanding faster than rotor

long - rotor is expanding faster than casing (slow down heat up)

Question 7

What are typical vibration levels of significance?

Answer 7

4 mils - alert
7 mils - danger
14 mils - PK directs tripping turbine / rx