7/31/2019 TSI 20.10.08
1/60
TURBOVISORY instruments
Anil Kapoor En r. O&M/C&I
7/31/2019 TSI 20.10.08
2/60
TURBOSUPERVISORYINSTRUMENTS
VIBRATION PICKUPS THERMAL EXPANSION PICKUPS
AXIAL SHIFT PICKUP ECCENTRICITY SPEED PICKUP BEARING TEMPERATURE
7/31/2019 TSI 20.10.08
3/60
NEED FOR TURBOVISORYINSTRUMENTS
Heavy mass rotating at high speed Small clearances between moving and
stationary blades Ensures turbine healthiness Gives idea of any problem in turbine
Helps in increasing turbine operatinglifetime by giving timely indications
7/31/2019 TSI 20.10.08
4/60
HPTIPT LPT
GENERATOR EXCITER
BRG.1 BRG.2 BRG.4BRG.3 BRG.5 BRG.6 BRG.7
TURBINE BEARINGSARRANGEMENT
7/31/2019 TSI 20.10.08
5/60
BEARING 1 (HPT FRONT)INSTRUMENTS
HALL PROBE FOR SPEEDMEASUREMENT
HPT ROTOR EXPANSION HP CASING EXPANSION THERMOCOUPLES FOR BEARING
TEMP.(4 NO.S) PEDESTAL VIBRATION PICKUP SHAFT VIBRATION PICKUP
7/31/2019 TSI 20.10.08
6/60
BEARING 2 (HPT REAR)INSTRUMENTS
AXIAL SHIFT PICKUP THERMOCOUPLES FOR BEARING
TEMP.(8 NO.S) PEDESTAL VIBRATION PICKUP SHAFT VIBRATION PICKUP
7/31/2019 TSI 20.10.08
7/60
BEARING 3 (IPT REAR)INSTRUMENTS
IP CASING EXPANSION IP ROTOR EXPANSION
ECCENTRICITY PICKUP THERMOCOUPLES FOR BEARING
TEMP.(2 NO.S)
PEDESTAL VIBRATION PICKUP SHAFT VIBRATION PICKUP
7/31/2019 TSI 20.10.08
8/60
BEARING 4 (LPT REAR)INSTRUMENTS
IP+LP SHAFT EXPANSION THERMOCOUPLES FOR BEARING
TEMP.(2 NO.S) PEDESTAL VIBRATION PICKUP SHAFT VIBRATION PICKUP
7/31/2019 TSI 20.10.08
9/60
7/31/2019 TSI 20.10.08
10/60
BEARING 6 (GENERATORREAR) INSTRUMENTS
THERMOCOUPLES FOR BEARINGTEMP.(2 NO.S)
PEDESTAL VIBRATION PICKUP
7/31/2019 TSI 20.10.08
11/60
BEARING 7 (EXCITER)INSTRUMENTS
THERMOCOUPLES FOR BEARINGTEMP.(2 NO.S)
PEDESTAL VIBRATION PICKUP SHAFT VIBRATION PICKUP
7/31/2019 TSI 20.10.08
12/60
VIBRATIONMEASUREMENTS
7/31/2019 TSI 20.10.08
13/60
VIBRATION CAUSES
Unbalance forces Internal damages
Misalignment Poor lubrication Eccentricity Thermal stresses
7/31/2019 TSI 20.10.08
14/60
VIBRATION TYPES
PEDESTAL VIBRATION SEISMIC MASS TYPE
VELOCITY TYPE ACCELERATION TYPE
ABSOLUTE SHAFT VIBRATION
PROXIMITY TYPE(NON CONTACT) EDDY CURRENT TYPE PICKUP
7/31/2019 TSI 20.10.08
15/60
4 steps in vibrationmeasurement
7/31/2019 TSI 20.10.08
16/60
SENSOR TYPES(SEISMIC MASS)
Velocity sensors Velocity of vibration is the speed at which
the part is moving at any instant during thevibration cycle Measured in mm/s
Rms value of velocity gives vibration Seismic mass type sensors Velocity gives the kinetic energy
7/31/2019 TSI 20.10.08
17/60
SENSOR TYPES(SEISMIC MASS)
Velocity sensors Works on PLUNGER COIL PRINCIPLE.
Two permanent magnets rigidly fixed to thecasing with coils arranged as seismic mass. The Relative motion between the coil and
magnet generates voltage proportional to
vibration velocity. Operates within range of 10hz to 150 hz
7/31/2019 TSI 20.10.08
18/60
CONSTRUCTION
Coil
Magnet
Magnet
Aluminum case
DamperTerminals
spring
Output is proportional to velocity, hence the name Velocity sensor
Output=B*l*V B & l are constant
Seismic sensor
7/31/2019 TSI 20.10.08
19/60
SENSOR TYPES(SEISMIC MASS)
Accelerometer Piezoelectric accelerometer transducers Rate of change of vibration velocity at any instant
during vibration cycle Measured in mm/s 2 Acceleration gives the force Emf proportional to force
Internal amplifier for boosting signal Can measure Acceleration, velocity and
displacement
7/31/2019 TSI 20.10.08
20/60
ACCELEROMETER
7/31/2019 TSI 20.10.08
21/60
SHAFT VIBRATION
Proximity (Non contact) type Shaft vibration measures the radial motion of the
rotating shaft relative to the case.
This measurement gives the first indication of afault, such as unbalance, misalignment, crackedshaft, oil whirl or other dynamic instabilities
Total distance moved by the vibrating part in agiven direction
Measured in micrometers
7/31/2019 TSI 20.10.08
22/60
SENSOR TYPES
Proximity (Non contact) type Proximity probe senses the distance between the
probe tip and the observed surface. Proximeter generates a radio frequency signal,
which is radiated through the probe tip into theobserved surface. Eddy currents are generated
in the surface and loss of strength in the returnsignal is detected by the proximeter.
7/31/2019 TSI 20.10.08
23/60
OSCILLATOR
PROBE GAP
V O L T S
0 100
EXTENSION CABLEAND PROBE
OBSERVEDMATERIAL
PROXIMITOR
VOLTAGEDETECTOR
CONDUCTIVEMATERIAL
PROXIMITOR
Eddy Current
Radio FrequencySignal
PROXIMITY SENSOR
7/31/2019 TSI 20.10.08
24/60
NON CONTACT TYPE
PROXIMITY SENSOR
7/31/2019 TSI 20.10.08
25/60
Measuring Amplifier
45O 45O
ProximityPick-up
L RSHAFT
2 transducers spaced 90 deg to each other for a 2 dimensional view ofeach bearing The 315 and 45 points are used to avoid the half joints of the bearingsand to ensure that when bearings are removed the probes are removedalong with them.This moves the probes away from possible mechanical damage when theturbine is being worked on.
PROXIMITY SENSOR
7/31/2019 TSI 20.10.08
26/60
VIBRATIONSENSITIVITY DISPLACEMENT
VELOCITY
ACCELERATION
FREQUENCYCPM
60 600 6000 60000 600 000
10
1
0.3.1
.01
.001
WHEN TO USE DISPLACEMENT,VELOCITY & ACCELERATION
V
i b r a
t i o n a m p
l i t u d e
7/31/2019 TSI 20.10.08
27/60
SHAFT VIBRATION
For no variation in gap we get DC signalwhich indicates gap or average distancefrom transducer tip.
In case shaft is vibrating there will be bothAC & DC components and varying voltagewill give vibration signal
Sensitivity around 8V/mm
7/31/2019 TSI 20.10.08
28/60
VIBRATION ANALYSES
Each machine defect produces a uniqueset of vibration components that can beused for identification.
By identifying different frequencycomponents we can make out the defect inturbine.
Spectrum analysis, shaft centerline plots,orbit plots, waterfall plots are some of thetechniques used for analysis
7/31/2019 TSI 20.10.08
29/60
PEDESTALVIBRATIONPICKUP
SHAFTVIBRATIONPICKUP
7/31/2019 TSI 20.10.08
30/60
Thermal expansions
7/31/2019 TSI 20.10.08
31/60
THERMAL EXPANSIONMEASUREMENT
Differential expansion Overall casing expansion
Rotor expansion
7/31/2019 TSI 20.10.08
32/60
HPTIPT LPT
GENERATOR EXCITER
BRG.1 BRG.2 BRG.4BRG.3 BRG.5 BRG.6 BRG.7
ANCHOR POINT
HP ROTOR/CASINGEXPANSION
IP ROTOR /CASINGEXPANSION
IP+LP SHAFTEXPANSION
7/31/2019 TSI 20.10.08
33/60
DIFFERENTIAL/ROTOREXPANSION
Difference between the thermal growth of the rotorcompared to the thermal growth of the case.
Important during a turbine "cold" start-up. Since the pedestal are of fixed type, differential
expansion can not be measured directly. Hence casingexpansion & rotor expansion are measured separatelyand differential expansion between the two rotorexpansion is measured at HP front & IP rear brgs
Due to the mass of the case it will grow slower than the
rotor, so the operator must make sure the case hasexpanded enough to keep it from making contact with therotor.
If shaft expands more than casing it is positive expansionand if casing expands more than shaft than it is negativeexpansion
7/31/2019 TSI 20.10.08
34/60
THERMAL EXPANSION/AXIAL SHIFT PICKUP
PROXIMITY TYPE VARIABLE INDUCTANCE TYPE
7/31/2019 TSI 20.10.08
35/60
7/31/2019 TSI 20.10.08
36/60
ROTOR EXPANSIONPICKUP
7/31/2019 TSI 20.10.08
37/60
d2 d1
L1 L2
Turbine Casing
I
-
MeasuringAttachment
Power Supply Unit
Large Relative Expansion, Shaft with double cone
L1 L2 Sensor Coilsd 1 d 2 Air gap
IP+LP SHAFT EXPANSION
7/31/2019 TSI 20.10.08
38/60
IP+LP SHAFTEXPANSION PICKUP
7/31/2019 TSI 20.10.08
39/60
7/31/2019 TSI 20.10.08
40/60
CASING/OVERALLEXPANSION
Steam temperature varies greatly betweenstartup, operation, and shutdown.
Shell expansion is a measurement of how much
the turbine's case expands from its fixed pointoutward as it is heated. Continuous indication of shell thermal growth
allows the operator to manage the amount of
shell distortion as the load is increased ordecreased. LVDT Type pickup
7/31/2019 TSI 20.10.08
41/60
OUTPUT VOLTAGE = DIFFERENCE OF VOLTAGE BETWEEN 2SECONDARY COILS
7/31/2019 TSI 20.10.08
42/60
7/31/2019 TSI 20.10.08
43/60
RANGES
HP Rotor Expansion: 0-25mm IP Rotor expansion:0-21mm
HP Casing Expansion:0-30mm IP Casing Expansion: 0-20mm IP+LP Shaft Expansion; (-)15-48mm
7/31/2019 TSI 20.10.08
44/60
SPEED PICKUP HALL PROBE
ECCENTRICITY PROXIMITY PICKUP
BEARING TEMPERATURE THERMOCOUPLES
7/31/2019 TSI 20.10.08
45/60
ECCENTRICITY
Eccentricity is measured as the deviation ofmass centre from the geometrical centre of thebearing journal.
Eccentricity is the measurement of Rotor Bow atrotor slow roll which may be caused by any or acombination of reasons
Fixed mechanical bow
Temporary thermal bow Gravity bow
7/31/2019 TSI 20.10.08
46/60
Eccentricity is measured while the turbine is on slow roll(1 to 240 RPM below the speed at which the rotorbecomes dynamic and rises in the bearing on the oilwedge) and requires special circuitry to detect the peak-to-peak motion of the shaft.
For eccentricity measurements it is recommended thatthe transducer be mounted vertically .
Slow roll and heating can help reduce the eccentricity tothe point where the turbine can safely be brought up tospeed without damage from excessive vibration or rotorto stator contact.
ECCENTRICITY
7/31/2019 TSI 20.10.08
47/60
Eccentricity
Eccentricity is normally measured P/P (Peak to Peak)The actual excursion from shaft centerline caused bybow would be one half that measurement or the 0/P(Zero to Peak) measurement
ECCENTRICITY
7/31/2019 TSI 20.10.08
48/60
Special consideration for using eddy current probes
RUNOUT Error signal generated by mechanical, electrical or
metallurgical irregularities of the shaftMECHANICAL RUNOUT
A smooth (64 micro-inch) area approximately 3 times thediameter of the probe tip must be provided for a viewingarea.ELECTRICAL RUNOUT
Eddy Probes are sensitive to the permeability andresistivity of the target material and the field of thetransducer extends into the surface area of the shaft byapproximately 15 mils (0.015"), care must be taken toavoid non homogeneous viewing area materials such asChrome.
7/31/2019 TSI 20.10.08
49/60
System Cable Length
Eddy Probe Systems are a "tuned" length,and several system lengths are available.
System length is measured from the probetip to the Oscillator/Demodulator, and ismeasured electrically which can be slightlydifferent than the physical length.
7/31/2019 TSI 20.10.08
50/60
The RF Field emitted fromthe probe tip of thetransducer isapproximately a 45 conicalshape. Clearance must beprovided on all sides ofthe Probe tip to preventinterference of the RFField.
7/31/2019 TSI 20.10.08
51/60
To prevent Ground Loops from creatingsystem noise, system common, groundand instrument wire shield must beconnected to ground at one location only.
7/31/2019 TSI 20.10.08
52/60
GAP VOLTAGE
Gapping thetransducer to thecenter of the linear
range is adequate
7/31/2019 TSI 20.10.08
53/60
TURBINE SPEEDMEASUREMENT
7/31/2019 TSI 20.10.08
54/60
BASIC ARRANGEMENT OF HALLPROBES AT BEARING 1
SENSOR
WIRE
BRACKET
PERMANENT MAGNETS
N-POLES-POLE
DISK
7/31/2019 TSI 20.10.08
55/60
SPEEDMEASUREMENT
Allows the operator to increase speed quicklythrough shaft critical frequencies
Hold the speed stable during heat soakplateaus
For electric generators, to accurately match thesynchronous frequency before connecting the
generator to the power grid. Used for tripping turbine in case of overspeed(2/3 logic)
7/31/2019 TSI 20.10.08
56/60
Bearing temperature
Measure of the how hot a bearing isoperating.
May be due to overloading, mis- alignment,improper lubricant pressure and/or flow.
Thermocouples used to measuretemperature. Each thermocouple has 3elements
7/31/2019 TSI 20.10.08
57/60
7/31/2019 TSI 20.10.08
58/60
AXIAL SHIFT
Shifting of rotor due to unbalanced forces in the turbine Positive towards generator, negative towards front
pedestal. Very critical measurement as very small gap between
stationary and rotating blades Three probes mounted and used in 2/3 protection logic. Total range from (-)1.5mm to + 1.5mm Protection at (-)1.0mm & +1.0mm Proximity probes or relative inductance type probes can
be used for measurement
7/31/2019 TSI 20.10.08
59/60
PORTABLE VIBRATIONMEASUREMENT
Vibration measurement closeto machinery avoids errorintroduced due to cableproblems.
Used to check vibration ofmachinery located at remotelocation.
Easy to carry Evaluate machine condition
and bearing problemsassociated with pumps whosesignal is not available incontrol room
7/31/2019 TSI 20.10.08
60/60
PHASE MEASUREMENT
Phase measurement is required foraccurate balancing of any rotor.
It also provides an indication of shaftcracks, misalignment, mass loss (such asthrowing a blade), and other faults.
Top Related