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April 22, 2023 PMI Revision 00 1

INTRODUCTION TO TURBOVISORY

INSTRUMENTS


Presentation outline•Turbovisory Parameters

•Measurement of Turbovisory parameter

•Introduction to Vibration Measurement

•Type of Vibration Sensors and their installation

•Differential Expansion /Axial Shift and their Installation

•Speed /Brg Metal temp/Valve Position Measurement


TURBOVISORY PARAMETERS

VIBRATIONS- SHAFT VIBRATION / ECCENTRICITY- BEARING VIBRATION

TURBINE EXPANSION- OVERALL EXPANSION- DIFFERENTIAL EXPANSION- AXIAL SHIFT

SPEED / OVERSPEED LOAD BEARING BABBIT METAL TEMPERATURES MS / HRH PRESSURE / TEMPERATURE TURBINE METAL TEMPERATURE VACUUM LUB OIL PRESSURE / TEMPERATURE HP / LP EXHAUST TEMPERATURE GLAND STEAM HEADER TEMPERATURE


CROSS SECTION OF TURBINE


ABS EXPANSION

REL EXPANSION

REL SHAFT VIBRATION

ABS BRG VIBRATION

ABS EXPANSION

AXIAL SHAFT POSITION

REL SHAFT VIBRATION

ABS BRG VIBRATION

REL EXPANSION

ECCENTRICITY

ABS BRG VIBRATION

RELATIVE EXPANSION

RELATIVE SHAFT VIBRATION

ABSOLUTE BRG VIBRATION




VIBRATION MEASURING INSTRUMENTATION

SHAFT VIBRATION / ECCENTRICITY- PROXIMITY PROBE

BEARING VIBRATION

- VELOCITY PICK UP


What are the different ways?• Overall• Time domain• Frequency domain• Envelope analysis• Cepstrum analysis• Wavelet analysis• Etc


Basic Theory Of VibrationSimple Spring Mass System

Upper Limit

Neutral Position

Lower Position

Dis

pla

cem

ent

Max Acceleration, Min Velocity

Max Acceleration, Min VelocityMax Velocity, Min Acceleration

IT FOLLOWS SINE CURVE


VIBRATION MONITORING

WHAT IS VIBRATION ?

WHAT CAUSES VIBRATION ?

HOW DO WE MEASURE VIBRATION ?

HOW DO WE ANALYSE VIBRATION ?


What Is Vibration?

It is the response of a system to an internal or external force which causes the system to oscillate.


2. Measurement direction - Horizontal, Vertical, Axial.


General rule of direction• We measure H direction for machines on the

foundation. • We measure V direction for machines on structures• We measure A direction when we suspect

misalignment• There are advantages, but there are exceptions to

this rule.



Modes of Amplitudes

• DISPLACEMENT

• VELOCITY

• ACCELERATION

• SPIKE ENERGY


Physical Significance Of Vibration Amplitude

Displacement : Strain Indicator

Velocity : Fatigue Indicator

Acceleration : Force Indicator


The significance • Displacement gives the strain energy• Velocity gives the kinetic energy• Acceleration gives the force• Spike energy/HFD/gE are special ways to measure

acceleration only.



UNITS OF MEASUREMENT

DISPLACEMENT - MICRONS

VELOCITY - MM / SEC.

ACCELERATION - MM / SEC2 , G



AMPLITUDE DESCRIPTORS

• RMS - Displacement Velocity

• PEAK - 1.414 RMS DisplacementVelocityAcceleration

• PEAK-TO-PEAK - 2 * PEAK Displacement


ISO 10816

1 Step


VIBRATION SENSITIVITY DISPLACEMENT

VELOCITY

ACCELERATION

FREQUENCYCPM

60 600 6000 60000 600 000

10

1

.1

.01

.001

WHEN TO USE DISPLACEMENT, VELOCITY & ACCELERATION


SIMPLE VIBRATION

Time(sec)

Amplitude(mm)

Period T

f = 1 / T Frequency f(Hz)

Amplitude(mm)

Time Domain

Frequency Domain

A

A


REAL VIBRATION

Time(sec)

Amplitude(mm)

Frequency f(Hz)

Amplitude(mm)

Time Domain

Frequency Domain - Vibration Signature


Amplitude & Frequency

Amplitude:It is the magnitude of Vibration signal.Units: Micron, MM/Sec, M/Sec2

Frequency:How many times oscillation is occurring for a given time period?Units: CPS(Hz), CPM


VIBRATION MEASURING INSTRUMENTS

– Analyser : Measures all the three characteristics viz. Amplitude, Freq. and Phase

– Meter : Measures only Amplitude

Thus we can have METERS of various types

Displ. And Velocity- Normally uses velocity pickup

Displ., Velocity, Acceleration and Bearing Condition- Normally uses Accelerometer

The heart of the instrument is the sensor


Vibration Sensors

• Acceleration Sensor - Accelerometer • Velocity sensor – Velocity sensor or seismic s

ensor• Displacement sensor - Non Contact pickup

Accelerometer


Accelerometer

• Piezoelectricity• Emf proportional

to force• Emf proportional

to acceleration

(Mass constant)• Hence called

accelerometer

Accelerometer


Accelerometer cont…..• Uses piezoelectric crystal • Normally uses internal amplifier for boosting signal • It will have low temp application up to 150 degree C• For high temperature application amplifier is not given

inside• This causes low signal strength and we use gold plated

contacts and small cable lengths (output rated in pc per g). The amplification is done outside

• Normal accelerometer (amplifier inside) will have strong signal output and can sustain cable lengths of 300 meter

• Available in several design, can go from DC to 10k Hz freq (600,000 CPM)

• Can measure Acceleration, velocity and displacement• It is advised to involve suppliers or persons knowledgeable

in this area to choose accelerometers for on line monitoring applications


Velocity sensorOutput=B*l*V B & l are constant

Output is proportional to velocity, hence the name Velocity sensor

Coil

Magnet

Magnet

Aluminum case

Damper

Spring

Terminals


Velocity sensor cont….• This is self generating (764 mv per mm/sec)• Can sustain cable length of 1000 feet easily• For longer length intermediate amplification is needed• The temperature rating is higher up to 250 degree C

(no electronics inside)• Sensitive to 60,000 CPM• Can check velocity and displacement only


Non contact type


Non contact sensor Installationin a Turbine


ABSOLUTE BEARING VIBRATION

VELOCITY TRANSDUCERSEISMIC MASS TYPE Works on PLUNGER COIL PRINCIPLE.Two permanent magnets rigidly fixed to the casing wit

h coils arranged as seismic mass.The Relative motion between the coil and magnet

generates voltage proportional to vibration velocity.


ABSOLUTE SHAFT VIBRATION• RELATIVE SHAFT VIBRATION IS BASED ON EDDY

CURRENT PRINCIPLE.• PROXIMOTY PROBE SENSES THE DISTANCE BETWEEN

THE PROBE TIP AND THE OBSERVED SURFACE.• PROXIMETER GENERATES A FREQUENCY SIGNAL,

WHICH IS RADIATED THROUGH THE PROBE TIP INTO THE OBSERVED SURFACE. EDDY CURRENTS ARE GENERATED IN THE SURFACE AND LOSS OF STRENGTH IN THE RETURN SIGNAL IS DETECTED BY THE PROXIMETER.


SHAFT & BEARING VIBRATION PICK UP


BEARING / SHAFT VIBRATION PICK UP MOUNTED ON BEARING NO. 4 PEDESTAL


RECOMMENDED LOCATIONS OF VIBRATION MEASUREMENTS FOR PEDESTAL BEARINGS


RECOMMENDED LOCATIONS OF VIBRATION MEASUREMENTS FOR HOUSING TYPE

BEARINGS (


Measuring

Amplifier

45O 45O

Proximity Pick-up

L RSHAFT

RECOMMENDED LOCATIONS OF SHAFT VIBRATION MEASUREMENTS


Measuring

Amplifier

Proximity Pick-up

L RSHAFT

RECOMMENDED LOCATIONS OF SHAFT VIBRATION MEASUREMENTS


ECCENTRICITY

• DEVIATION OF MASS CENTER FROM THE GEOMETRICAL CENTRE OF THE BEARING JOURNAL.

• PROPORTIONAL TO MAX ROTOR DEFLECTION OCCURING AT THE MIDDLE OF SHAFT

• MEASURED BY VARIATIONS OF AN A.C. CURRENT IN A COIL DUE TO VARIATION IN PROXIMITY OF TARGET MATERIAL

INDUCTIVE TRANSDUCER

PROXIMITY(EDDY CURRENT) TRANSDUCER


INDUCTIVE TRANSDUCER• TWO MAGNETICALLY RELUCTANCE TYPE

TRANSDUCERS IN BRIDGE CONFIGURATION, EXCITED BY 10V AC (1953 HZ)

• BRIDGE OUTPUT IS MODULATED BY A PERCENTAGE PROPORTIONAL TO AMOUNT OF ECCENTRICITY WITH A MODULATING FREQUENCY PROPORTIONAL TO ROTOR SPEED

• DEMODULATOR, FILTER,AMPLIFIER & AMPLITUDE DETECTOR


PROXIMITY TRANSDUCER• SENSES THE DISTANCE BETWEEN THE PROBE TIP

AND OBSRVED SURFACE• PROXIMETER GENERATES RF SIGNAL, RADIATED

THROUGH PROBE TIP INTO OBSERVED SURFACE.• EDDY CURRENTS ARE GENERATED IN THE SURFACE

AND THE LOSS OF STRENGTH IN THE RETURN SIGNAL IS DETECTED.

• LOSS OF POWER PROPORTIONAL TO GAP BETWEEN PROXIMETER & CONDUCTIVE BODY.


EXPANSION MEASURING INSTRUMENTS

OVERALL EXPANSION- POSITION TRANSMITTER

DIFFERENTIAL EXPANSION MEASUREMENT- PROXIMITY PROBE

AXIAL SHIFT MEASUREMENT- PROXIMITY PROBE


DIFFERENTIAL EXPANSION

• THE DIFFERENCE OF AXIAL EXPANSION BETWEEN THE ROTOR AND THE CASING

• POSITIVE IF SHAFT EXPANDS MORE THAN CASING,NEGATIVE IF CASING EXPANDS MORE THAN SHAFT

• CASING EXPANSION & ROTOR EXPANSION MEASURED SEPARATELY AND DIFF EXPANSION IS CALCULATED

• ROTOR EXPANSION MEASURED AT HP FRONT & IP REAR, LP REAR .

• MEASURING COLLAR IS IN THE FORM OF DOUBLE CONE.


DIFFERENTIAL EXPANSION (FOR SMALL EXPANSION) & AXIAL SHIFT PICK UP


IP DIFFERENTIAL EXPANSION PICK UP MOUNTED ON BEARING NO. 3 PEDESTAL


LP DIFFERENTIAL EXPANSION PICK UP MOUNTED ON BEARING NO. 4 PEDESTAL


CASING EXPANSION• MEASUREMENT CARRIED OUT AT HP CASING FRONT & IP

CASING ON THE REAR SIDE.• DISPLACEMENT SENSOR MOUNTED ON THE PEDESTAL C

OVER AND CONNECTED TO THE CASING VIA A ROPE. THE OTHER END OF THE ROPE IS CONNECTED TO A ROTABLE MEASURING DEVICE.

• ROTABLE MEASURING DEVICE ROTATES ECCENTRIC TO THE TWO SENSOR COILS WHICH CREATE DIFFERENT AIR GAPS BETWEEN THE MEASURING DEVICE AND THE COILS .


AXIAL SHIFT OF ROTOR

• MEASUREMENT YIELDS INFORMATION ON THE POSITION OF THE SHAFT IN THE THRUST BEARING AND ON WEAR OF THE BEARING.

• AXIAL SHIFT BEYOND PERMISSIBLE LIMIT WOULD LEAD MECHANICAL INTERFERENCE & SURFACE RUBBING.

• MEASURED BY EDDY CURRENT PRINCIPLE.• MASUREMENT RANGE IS -1.5 TO 1.5 MM

April 22, 2023 PMI Revision 00 53OVERALL EXPANSION PICK UP


OVERALL EXPANSION MOUNTED ON BEARING NO. 1 PEDESTAL

April 22, 2023 PMI Revision 00 55AXIAL SHIFT MEASUREMENT AT IP COLLAR


DIFFERENTIAL EXPANSION (FOR LARGE EXPANSION) PICK UP


SPEED, LOAD MEASURING INSTRUMENTS

SPEED / OVERSPEED- KEY PHASOR- HALL PROBE

LOAD MEASUREMENT- CURRENT TRANSFORMERS- POTENTIAL TRANSFORMERS


SPEED SENSOR

• Mechanical governor :Radius of flywheel changes due to change in speed (effect of centrifugal forces)

• Hydraulic Governor: Hydarulic pressure developed by the primary oil pump changes due to change in speed

• Electrical governor: Three no hall probe supply voltage pulse each time permanent magnet pass them.


SPEED MEASUREMENT• CONSISTS OF SLOTTED DISC(FITTED AT THE TURBINE

SHAFT) WITH 60 RADIAL SLOTS AND MAGNETIC PROBE(HALL PROBE) MOUNTED FACING THE SLOTS.

• 4 NO OF HALL PROBES, 3 USED, 1 SPARE• PULSE CONVERTER WITH 3 ISOLATED OUTPUTS (2

ARE USED)• 2 CHANNEL MEASUREMENTS


SPEED MEASUREMENT INSTRUEMENT MOUNTED IN HP FRONT BEARING PEDESTAL

4 : HYDRAULIC SPEED TRANSDUCER5 : ELECTRIC SPEED TRANSDUCER


HALL PROBE

April 22, 2023 PMI Revision 00 62HALL PROBE IN BEARING NO. 1 PEDESTAL

April 22, 2023 PMI Revision 00 63OVERSPEED TRIP BOLTS IN BEARING NO. 1 PEDESTAL


PRESSURE, TEMPERATURE, FLOW MEASURING

INSTRUMENTSPRESSURE MEASUREMENT- PRESSURE TRANSMITTER

VACUUM MEASUREMENT- KENETOMETER- MERCURY MANOMETER

TEMPERATURE MEASUREMENT- TEMPERATURE TRANSMITTER, THERMOCOUPLE, RTD

FLOW MEASUREMENT- FLOW NOZZLES, ORIFICES


THERMOCOUPLE IN JOURNAL BEARING


THERMOCOUPLE

BABBIT METAL TEMPERATURE MEASUREMENT IN COMBINED JOURNAL & THRUST BEARING


THRUST PAD ARRANGEMENT AND THERMOCOUPLE LOCATION IN COMBINED THRUST AND JOURNAL BEARING

THERMOCOUPLE


VALVE POSITION

• NON CONTACT DISPLACEMENT MEASURING EQUIPMENT

• CONSISTS OF A SENSOR WITH TWO PRIMARY & SECONDARY COILS AND A SHORTING RING.

• THE SHORTING RING IS ATTACHED TO THE VALVE STEM AND MOVES OVER THE MAGNETIC CORE.

• MOVEMENT OF SHORTING RING CAUSES GENERATION OF POSITION DEPENDENT OUTPUT VOLTAGE IN THE SECONDARY COILS.


THANK YOU

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