TURBINE SUPERVISORY INSTRUMENS (TSI) SYSTEM

Purpose

Monitoring of Critical Turbine Parameters

› Turbines needs very close monitoring and supervision of certain Critical Turbine Operating Parameters
during various stages of operation like start-up, loading, load changes and coasting down.

› TSI system provides continuous on-line measurement and monitoring of critical Turbine Parameters.

› TSI acts as an aid to interpret the condition or health of Turbine for safe and proper operation of steam
turbine.

› Alarms can be set to alert Operators for conditions that may compromise the operation of Turbine.

› The critical nature of Turbine Operation, justifies the cost of purchase and installation of continuous
monitoring systems.

› If monitoring levels indicate an abnormal operating condition, Operating person can take a rational
decision and shutdown the Turbine to prevent possible disastrous damage to Turbine.

continued……
TSI for Condition Monitoring of Turbine

The Modern Turbo Supervisory Instrumentation System provides continuous online Monitoring and information on Physical
Condition of Turbine, such as:

› Misalignment

› Unbalance by a multitude of causes

› Thrust bearing failure

› bowed bent rotor

› Radial rubs

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TSI for Critical Turbine Parameters

Turbo Supervisory Instrumentation System continuously provides real time measured values of below listed critical
Turbine Parameters :

› Casing Expansion

› Eccentricity

› Axial Shift/Rotor Position

› Differential Expansion

› Turbine Speed

› Bearing Temperature

› Turbine Bearing Vibrations

› Shaft Relative Vibrations

› Valve Position
› Key Phasor

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TSI Arrangement

TSI Arrangement
HP: High Pressure Cylinder DEHI: Differential Expansion
HP&IP Total 8 Speed Sensors:
IP: Inter-space pressure Cylinder DELP: Diff. Expansion LP (1)SE-1 : To Measure Speed for TSI
LP: Low pressure Cylinder HEL: Heat Expansion – HP left (2) SE-2-4: To Measure Overspeed
E: Excitation Machine HER: Heat Expansion – HP (3) SE-5-7: To Measure speed for DEH
Right (4) SE-8: For Intellegent tachometer in turbine
KY: Key Phasor BV: Bearing Vibration
SE: Speed SV: Shaft Vibration
SP: Shaft Position
ECC: Eccentricity 5
Turbine Casing Expansion

› The expansion or growth of the turbine's casing is the measurement of how much the turbine's casing expands
or grows as it is heated.

› The HP/IP ST shell is anchored or keyed to the foundation at the Front Std & is free to expand axially on sliding
shell arms at the Front standard.

› The LP turbine casing is anchored near the middle of LP casing and is free to expand axially on either directions
from the anchor point.

› The Casing Expansion measurement is utilized by operators to monitor the proper thermal growth of the
turbine's casing during startup, operation, and shutdown.

› If the ability of the shell to expand becomes impaired, internal clearances could become compromised resulting
in damage to the unit.

› Large turbine cases grow or expand thermally, in some case up to several inches

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Turbine Casing Expansion

HPT Expansion IPT Expansion LPT Expansion

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Casing Expansion Measurement

Casing Expansion is measured by:

› Linear Variable Differential Transformer (LVDT)

• A linear variable differential transformer (LVDT), which is mounted at the front standard. As the shell expands & contracts,
the rod of the LVDT moves inside the device.

• This movement causes a change in the LVDT signal which is conditioned electrically and output as a DC voltage to the
turbine controller.

• Shell expansion is used for indication only & has no alarm or trip function.

• This parameter is monitored primarily during startup to ensure that the steam turbine casing & rotor grow thermally at
nearly the same rate.

› Dial Gauge

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Casing Expansion

Case Expansion
Monitor

LVDT
Transmitter

LVDT (Linear Variable

Differential Transformer)
Casing Expansion

Case
Dual case exp.
Monitor
Sensor

LVDT

Drive Unit
Eccentricity

› It is defined as a deviation of the mass centre from the geometrical centre of the bearing journal.

› Every machine, when built is left with certain amount of inherent eccentricity.

› This can be due to deficiency in machining.

› Sag due to its weight and

› The clearances at the bearings.

Eccentricity

› This is proportional to the maximum rotor deflection occurring at the middle of shaft.

› The rotor deflection shifts the centre of gravity of the rotor.

› This deflection creates an imbalance in the rotating mass of Turbine.

› Imbalance generates excessive vibrations when the machine is running at normal speeds.

› Thus eccentricity measurements provide information on the onset of vibration even when the machine is at barring gear speed
or low speeds.
Eccentricity

› A rotor which has been sitting idle during overhaul or has been inadvertently stopped during coast-down for an extended
period will develop a bow or bend.

› This condition must be corrected by turning gear operation.

› Sometimes the rotor condition necessitates auxiliary heating prior to high speed operation

› Auxiliary heating prevents internal clearance rubbing.

› Thus Eccentricity helps operator to make decision on start-up of Turbine.

› Eccentricity measurement is important during Turbine slow roll.

Eccentricity

Tecc MSecc

Tspan BSpan

Assuming uniform stiffness and weight, the rotor mid span eccentricity may be expressed by the calculation using the following formula:

(T ecc x ½B span) /T span = M Secc

Where
T ecc = Transducer measured eccentricity
B span = Bearing Span
Tspan = Transducer span from bearing
M Secc = Midspan eccentricity
Eccentricity Measurement

› Eccentricity is electrically measured by the change of a.c. in a coil due to the variation in the proximity of the target material. There
are two methods to measure eccentricity.

• Inductive transducer operating at excitation frequencies : 50HZ to 20KHZ

• Proximity (Eddy current) transducer operating at excitation frequencies 500KHZ to MHZ.

› The transducers of both types are mounted to measure the varying air gap of a collar specially machined on the rotor.

› The variation in the gap as the collar rotates, provides the data of the peak to peak excursion of the rotor.
 Eccentricity Measurement

Probe(s) are mounted outside the pressure case as far as possible from the bearing (Node Point) because
practically it is impossible to mount Probe mid span on the rotor where the eccentricity measurement would be the
highest.

Eccentricity Collar
Eccentricity Measurement

Monitor

Mounting bracket Driver

Sensor

Machine case

Shaft
Axial Shift/Rotor Position

› The axial thrust is the result of the impact of the steam on either sides of the blades in each stage.

› Though attempts have been made to balance and nullify the thrust by reversing the direction of steam flow in H.P.
and I.P. cylinders and providing double flow L.P. cylinder, there exists, however, a net thrust in the direction of
generator called working thrust.

› In order to take the thrust, thrust bearing is provided at the front end of the H.P. cylinder where steam enters.
Axial Shift/Rotor Position

› The axial thrust, causes the thrust collar to move either towards the working pads or towards the surge pads
depending on the direction of axial thrust.

› The thrust bearing is the anchor point of the rotor in axial direction.

› The axial thrust may increase on either directions on the following conditions:

• More / less resistance developed in the steam flow path on account of salt deposits/erosion, wearing off, etc.
• Thrust bearing failure.
• Oil flow failure/inadequate flow to thrust bearing.
Axial Shift/Rotor Position

› The measurement system indicates the position of the thrust collar with respect to the working pads.

› The indication determines the extent of wear of thrust pads.

› It is imperative to continuously monitor the position of thrust collar as axial shift beyond permissible limits could
lead to mechanical interference and severe rubbing.
Axial Shift/Rotor Position

Thrust Pad
Axial Shift/Rotor Position Measurement

› Eddy current pick ups mounted facing the collar axially, measure the gap and give the axial position of the rotor.

› The range of measurement is from (-1.5) to (1.5) mm of axial shift.

› The ‘0’ reference position of the rotor is that position when the collar touches the working pads.

› The positive axial shift as per convention is the movement of the collar i.e. the rotor in the direction of the
generator and the negative axial shaft occurs when the collar moves towards front pedestal direction.

› Usually the working value under normal condition will be from 0 to -0.5 mm which is called Free Floating Zone.

› Beyond free floating zone on either direction, the collar will start rubbing the respective pads.
Axial Shift/Rotor Position Measurement

Oscillator-
Demodulator Thrust
(Driver) Monitor
Extension cable

Rotor

Sensor
Axial Shift/Rotor Position Measurement

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 Differential Expansion

› Differential Expansion on a turbine is the relative measurement of the rotor's axial thermal growth with respect to the casing.

› Rotor Expansion on a turbine is the absolute measurement of the rotor's axial thermal growth with respect to the turbine's foundation.

› A typical large steam turbine unit will have a thick case, on the order of 12“.

› Due to the mass of this casing, it will expand and contract at a slower rate than the relatively rotor.

› During turbine startup, extra care must be used to ensure that the casing has been properly heated and expanded sufficiently to
prevent contact between the rotor and the casing.
Differential Expansion

› A standard convention is followed that if the shaft expands more than the casing it is said to be a positive expansion.

› If the shaft contracts or casing expands more than the shaft it is said to be negative expansion.

A high positive expansion occurs:

› During start up conditions

› After extended period of no load/low load running followed by sudden loading.

› When the exhaust temperature is too high

› Restraint of casing sliding/expansion

A high negative expansion occurs:

› During cooling down/shut down

› After extended period of full load running followed by no load/low load running

› When exhaust hood temperature is too low.

Rotor Expansion
Measurement of Differential Expansion

Mounting Bracket
A) Disc Type

Sensor
Disc on shaft

Mounting Bracket

B) Ramp Type

Sensors
Ramp arrangement
Measurement of Differential Expansion

Driver Ramp target

Differential type
Expansion
Monitor

Rotor

Sensor

Rotor
Ramp target
type

Complementary input type Rotor

Measurement of Differential Expansion

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Valve Position

The Main Steam Control (Throttle) Valve admits superheated steam to prime mover turbine. Load condition dictates the
opening or closing of Main Steam Control Valve

› Valve position indication is actually a measurement of degree of control valve opening or closing.

› This measurement is usually made with a Linear Variable Differential Transformer (LVDT).

› LVDTs are electromagnetic devices that have three coils of wire wound on a hollow tube and a metal rod moving
inside the hollow tube.
Valve Position

Actuator

LVDT
Transmitter
LVDT Valve Position
Monitor
Main
Steam

Valve

Rotor
Turbine Speed and Acceleration

› This is the speed at which the Turbine is rotating and it is indicated in RPM (revolutions per minute). All the two pole
generating machines rotate at 3000 RPM.

› Turbine speed is measured by observing a multi-toothed gear wheel located inside the front pedestal.

› Acceleration is usually monitored during startup to prevent excessive torque on the rotors, prior to line synchronization.

› Once the generator has been synchronized and is being controlled by load dispatchers the acceleration rate is not
monitored.

› Acceleration rate measurements use a speed input to derive its output.

Shaft rotational speed

Oscillator-
Extension cable Demodulator Speed Monitor
(Driver) (Tachometer)

Sensor

Rotor
Speed Measurement

Monitor

Mounting bracket

Gear Wheel

Sensor
Housing
Bearing Temperature and its Measurement

Bearing temperature is a measure of the how hot a bearing is operating.

› It may be due to overloading.

› Misalignment of rotating parts.

› Improper lubricant pressure and / or flow.

Nearly all turbine generator bearings are installed with bearing temperature sensors. These sensors are:

› Thermocouples or

› Resistance Temperature Detector (RTD).

 Shaft Vibration

› Vibration is the back and forth motion of the machine or machine parts under the influences of oscillatory
forces caused by dynamically unbalanced masses in the rotating system.

› Vibrations originate from the rotating mass centre and are transmitted radially and axially to the supports. i.e.
bearing pedestals called radial and axial vibration.

› Initial level of vibrations depend upon the net unbalance left in the machine during the manufacturing and
erection stages

› his initial vibration level increases in due course of operation of the machine on account of:

• Fast out of balance changes like fracture etc.

• Slow out of balance changes like corrosion, erosion, deposits bends, etc.

• Self excited rotor vibrations like steam pulsation etc.

• Mechanical looseness in pedestal faults in coupling, bearing etc.

Shaft Vibration

› Excessive vibrations may lead to mechanical failure of the turbine components and calls for extremely
reliable monitoring system.

› Bearing pedestals are the points where normally the vibration measurements are made.

› Vibrations are usually measured as the amplitude of the maximum exercise of the vibrating point in
microns. It is either given as the single amplitude (peak) or double amplitude (peak to peak).

› The other way of measuring vibrations is by measuring the velocity of the motion of the vibrating point.
This measurement is being considered very useful. It is measured in mm/sec (R.M.S).

› Sometimes a third mode i.e. the acceleration of the motion of the point adopted. The acceleration
measures the amount of vibrating “Force”.
Shaft Vibration

Eddy Current Probe

Bearing

Bearing housing

Soft Metal (Babbit) Oil Wedge (load zone)

Shaft Vibration

45 Deg

Mounting arrangement

Sensors

Shaft

Radial Shaft Vibration in X&Y direction

Shaft Vibration

Oscillator-
Demodulator Vibration
(Driver) Monitor
Extension cable
Vertical
center

45° 45° Sensor

Sensor
Rotor
Casing Vibration

Velocity sensor/ Monitor

accelerometer

Mounting pad

Junction box
Bearing housing

Shaft
Key Phasor/Phase Marker

› Phase or phase angle, is a measure of the relationship of how one vibration signal relates to another vibration
signal and is commonly used to calculate the placement of a balance weight.

› This parameter is not usually displayed continuously but is monitored periodically.

› Installation involves locating or installing a once-per-turn event such as a key or notch that the Eddy Probe will
view.

› It’s a reference pulse used for analysis & Diagnosis purpose

Key Phasor/Phase Marker
Key Phasor/Phase Marker
Turbovisory Parameters
Sensors for TSI system

Primary Sensors installed inside the turbine casing are the heart and soul of any Turbo Supervisory Instrumentation System. The

primary sensors are:

› Proximity or Eddy Current Probe

› Linear Variable Differential Transformers (LVDT)

› Velocity Probe

› Accelerometer Sensor

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Proximity or Eddy Current Probe

One very common type of proximity probe is known commercially as a "Proximiter“ or Eddy Current probe

› The Proximity Probe, also called "Displacement Transducer", is a permanently mounted unit, and requires a signal-
conditioning amplifier to generate an output voltage proportional to the distance between the transducer end and the
shaft.

› It operates on a magnetic principle, and is thus sensitive to magnetic anomalies in the shaft. Care should be taken
that the shaft is not magnetized to assure the output signal is not contaminated.
Proximity Probe

› An Eddy Probe system consists of a matched component system: a pickup, an extension cable, and a signal
sensor.

› The signal sensor generates a high frequency oscillating RF signal that is sent through the extension cable to the
pickup tip.

› The pickup tip, having a wound coil of fine wire, radiates a electromagnetic field.

› As the radiated field is bisected by the rotor surface, eddy currents are created on the rotor surface.
Proximity Probe

› As the rotor surface moves closer to the pickup tip, a greater amount of eddy currents are created inversely
proportional to the gap between the surface and the pickup tip.

› The signal sensor contains a demodulator which measures the increase in eddy currents, and generates an
equivalent DC voltage proportional to the gap.

› The voltage method of gapping the Probe is recommended over mechanical gapping.
 Proximity Sensors

Driver

Sensor Coil

Conditioner
Bridge Demodulator.
Amplifier
.
Circuit
` Output
Oscillator
. Linerizer
.
Magnetic
Flux
Eddy
Current
Target(Metal) Voltage ∝
Displacement
Proximity Probe Field Installation

Driver
Sensor
Extension cable

Driver

Junction box
Proximity Probe

› Whenever the expected range exceeds a single transducer range a complimentary system is required.

› A complimentary system utilizes two (2) Eddy Probe transducers viewing the opposing faces of the collar or ramp.

› The complimentary system extends the operating full range of the system.

› This system operates such that as the collar or ramp moves out of the operating range of one transducer it moves into the
operating range of the second transducer.

› As Eddy Probe systems operate on the proximity theory of operation, they are not effected by oil or other non- conductive material
that may come between the target area and the transducer.
Proximity Probe

Calibration of Eddy Current Probe

All Eddy Probe systems (Probe, Cable and Oscillator Demodulator) should be calibrated prior to being installed. This can be done by using
a Static Calibrator, 24 VDC Power Supply and a Digital Volt Meter.

› The Eddy Probe is installed in the calibration jig with the target set against the Eddy Probe tip.

› Target attached is then moved away from the Eddy Probe in regular increments.

› The voltage reading is recorded and graphed at each increment.

› Eddy probe will produce a voltage change of 1.0 VDC ±0.05 VDC for each incremental gap change while the target is within the linear
range.
Linear Variable Differential Transformer (LVDT)

› LVDTs are electromagnetic devices that have three coils of wire wound on a hollow tube and a metal rod moving inside
the hollow tube.

› The center coil of wire is excited by a supply voltage which induces a voltage in the other coils as the rod or plunger
travels throughout its range.

› When the plunger is centered in its range the induced voltage of the two secondary coils is equal in magnitude, but
opposite polarity.

› As the plunger moves to either side of the center position the voltage of one of the secondary coils increases while the
other secondary coil experiences a decreased voltage.
Linear Variable Differential Transformer (LVDT)
Velocity Probe

› Velocity Transducers basically comprise of a Seismic mass which as a

result of the vibration, allows a magnet to move relative to a coil in which
is generated an e.m.f. Either the magnet or the coil may be fixed to the
vibrating body.

› A typical detector consists of permanent magnet rigidly fixed to the casing

with coils arranged as seismic mass.

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Accelerometer Sensor

› An accelerometer is an electromechanical device used to measure acceleration forces. Such forces may be static,
like the continuous force of gravity or, as is the case with many mobile devices, dynamic to sense movement or
vibrations. Acceleration is the measurement of the change in velocity, or speed divided by time.

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Piezoelectric Acceleration Transducer

Mass Weight

Electrode

Piezoelectric Device e

Electrode

Casing
Stud Bolt

Vibrating Object Vibration

Output Voltage ∝Force ∝ Acceleration Vibration

Accelerometer Sensor
Typical TSI Monitoring System
Typical TSI Monitoring System

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Typical TSI Monitoring System

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Features of TSI System

› Dual channels and built-in processor for each module

› Interface with host computer and system
› Communication at two modes via standard RS485 interface
› Prevent dangerous operating condition
› Extend the service life of system
› Minimize spare part consumption
› Improve maintenance plan
› Modular concept provides most compact system configuration
› One 19” rack accommodating 14 cards/28 channels
› Data read and configuration via RS232 serial port
› Communication via RS485 interface
Features of TSI System
Features of TSI System MMS6000

Speed Monitor And Overspeed Control Module

› Three monitors to perform speed measurement and over speed control.

Differential Expansion and Shaft Displacement Monitor Module

› Two modules used for shaft displacement and differential expansion measurement

Shaft Vibration Monitor Module

› The two channels of each module respectively monitor the vibration values in X-direction and Y-direction for each point.
Features of TSI System MMS6000

Eccentricity Monitor Module

› The eccentricity monitor module uses eddy current sensor.

Bearing Vibration Monitor Module

› The vibrations at eight points are monitored for entire turbine generating unit. Each module monitors two points

Absolutely Expansion Monitor

› Two monitors are used as thermal expansion measurement in the device (left and right HP).
Features of TSI System MMS6000

Communication Unit
› Communication unit modules continuously access monitoring system modules connected with RS485 bus to
perform real time data acquisition and convert characteristic value, alarm and module status data into standard
MODBUS and TCP/IP protocol and it can be exported through the TCP/IP interface.

› The data can be accessed and displayed by DCS and DEH system.
Features of TSI System MMS6000

Intelligent Transient Speedometer

› The speedometer with special sensor is used to measure rotating machine speed. Its speed measurement range of
0 to 5000r/min can meet the requirements of speed measurement for turbine operating normally.

› The maximum dynamic speed of turbine may be locked and stored to obtain accurate runaway value. When
conducting over speed test, you can select rapid display function to capture turbine speed more frequently.
 Thank
You
May 02, 2019 Common English Mistakes 70