the presentation regards a 2x150 MW steam turbine in Zambia. It teaches the methods of monitoring the turbine rotor trains including speed, vibrations and expansion. Check the presentation to learn more and the technology used.

1. TURBO SUPERVISORY
INSTRUMENTS
Presenter : Chona(C & I)

2. OVERVIEW
Turbine supervision is an essential part of the day-to-day running
of any power plant. There are many potential faults such as
cracked rotors and damaged shafts, which result from vibration
and expansion. When this expansion and vibration is apparent in
its early stages the problem can usually be resolved without any
of the disruption caused when a turbine has to be shut down. By
appropriate trending of the various measurement points and the
identification of excessive vibration or movement, scheduled
equipment stoppages or outages can often be utilised to
investigate and resolve the failure mechanism.
The turbine supervisory instrument (TSI) deals with the various
parameters of the turbine such as Rotating speed, Zero speed,
Over speed, Axial displacement, Eccentricity, Shaft vibration,
Bearing housing cover vibration, Differential expansion and
Thermo expansion of turbine casing.

3. TURBO SUPERVISORY INSTRUMENTS
 Vibration sensors
 Axial displacement
 HP Differential Sensors
 LP Differential Sensors
 Speed Sensor
 Eccentricity
 Bearing housing vibration

4. VIBRATION SENSORS
 What is Vibration?
Any motion which repeats after an interval of time.
 vibration monitoring is perhaps the primary method of
machine health monitoring on steam turbines. The type of
transducer used is seismic (i.e. vibration of turbine relative
to earth) and can either be a velocity transducer or an
accelerometer.

5. ACCELEROMETERS
 An accelerometer is a device that measures the vibration, or
acceleration of motion of a structure. The force caused by vibration or a
change in motion (acceleration) causes the mass to "squeeze" the
piezoelectric material which produces an electrical charge that is
proportional to the force exerted upon it. Since the charge is proportional
to the force, and the mass is a constant, then the charge is also
proportional to the acceleration.

6. VELOCITY SENSORS
 When a coil of wire is moved through a magnetic field, a voltage is
induced across the end wires of the coil. The induced voltage is caused
by the transferring of energy from the flux field of the magnet to the wire
coil. As the coil is forced through the magnetic field by vibratory motion,
a voltage signal representing the vibration is produced.

7. EDDY CURRENT PROXIMITY PROBE
The principle of operation, as the name implies, depends upon the eddy currents set up in the
surface of the target material - shaft, collar, etc. adjacent to the probe tip. The Eddy probe tip
is made of a dielectric material and the probe coil is encapsulated within the tip. The coil is
supplied with a constant RF current from a separate Eddy Probe Driver connected via a cable,
which sets up an electromagnetic field between the tip and the observed surface. Any
electrically conductive material within this electromagnetic field, i.e. the target material, will
have eddy currents induced in its surface. The energy absorbed from the electromagnetic field
to produce these eddy currents will vary the strength of the field and hence the energizing
current, in proportion to the probe target distance. Such changes are sensed in the driver
where they are converted to a varying voltage signal.

8.  Shaft Vibration
These are vibration measured for rotating machine/equipment.
Shaft displacement is monitored by non-contact displacement probes such
as eddy-current probes. These probes produce a voltage proportional to the
distance of the shaft surface relative to the tip of the probe. To ensure that
all the shaft vibration data is captured, probes mounted in the X and Y axis
are normally used.
Probe location
Turbine is configured with 5 bearing and to each bearing 2 radial vibrations
probes are installed on X and Y axis, total of 10 vibration probes are
installed.
 Sensor type :8mm proximity probe
 Transmitter :8mm proximity transducer
 Voltage gap :10V dc to 0.5 between sensor and turbine shaft teeth.

9. SHAFT VIBRATION SENSOR

10. Bearing Vibration
 Bearing vibration sensors constantly monitored the bearing vibration
and compare the values to the system set values.
 velocity seismoscope transducer is used for bearing housing casing or
structural vibration. velocity seismoscope sensor is a two wire system
which uses moving coil technology and provide a voltage output directly
proportional to the transducer vibration velocity.
 sensor :velocity seismscope sensor mounted on the bearing housing
(contact type vibration sensor)
 Normal value < 30 microns
 Alarm value <= 50 microns
 Shut down value >= 80 microns
Probe location
 To each bearing velocity seismoscope is installed, a total of 5 velocity
seismoscope are used.

11. BEARING VIBRATION SENSORS
 Seismic sensor

12. AXIAL DISPLACEMENT
Shaft Axial Positioning
No-contact probes are also used to measure rotor axial displacement.
The installation comprises of two probes which guarantee redundancy.
It is to detect the abnormal axial thrust on the turbine generator rotor.
probe location
 To the second bearing 2 shaft axil positioning probes are located in
to the thrust collar.
 Sensor type :11mm proximity probe
 Transmitter :11mm proximitor transducer
 Voltage gap :10V dc to 0.5V

13. AXIAL DISPLACEMENT PROBES

14. SPEED SENSORS
Rotor over speed sensors monitors turbine rotor speed and will
shutdown turbine when maximum allowable speed(trip speed) is
reached.
•Normal value 2985 to 3015 rpm
•Alarm value 3090 rpm, all control valves will get close and re open
when speed drops below of it.
Electrical over speed protection:
From ETS >= 3275 rpm
From DEH >= 3300 rpm
 The eddy current probe as well as being used for shaft vibration
and differential expansion can also be used as a speed
monitoring transducer.

15. Zero speed switch
A zero speed facility is incorporated in a speed
monitoring system or by a separate system entirely. A
zero speed facility works by measuring the period
between two pulses. When the period exceeds the
selected zero speed time limit an alarm is initiated.
 For turning gear to come in to action, the zero speed
sensor should detect that the turbine rotor has come to
zero rpm.

16. Speed sensor installed in front pedestal
 Over Speed protection-1 (SE-1) - 8 mm Speed Probe:
10 V DC ± 0.5Voltage gap
 Over Speed Protection -2 (SE-2) - 8 mm Speed Probe
:10 V DC ± 0.5Voltage gap
 Over Speed Protection -3 (SE-3) - 8 mm Speed Probe :
10 V DC ± 0.5Voltage gap
 Zero Speed (SE-4) - 8 mm Speed Probe : 10 V DC ±
0.5Voltage gap
 Speed (SE-5) - 8 mm Speed Probe :10 V DC ±
0.5Voltage gap

17.  Speed sensors

18. ECCENTRICITY
Definition
 Eccentricity is measure of shaft bow at slow speed.
This choice is based on the HP turbine rotor being the
hottest part of the whole shaft and is more susceptible to
thermal deformation than any other part of the shaft.
Eccentricity is measured as the radial displacement of the
shaft surface closed to the eccentricity transducer when the
shaft is turned by 180 deg.
Reasons for eccentricity measurement
 To make sure that the turbine run up is not begun until
the rotor is straight enough.
 To detect excessive rotor deformation during turbine
operation at low speed

20. THERMAL EXPANSION
HP and LP Differential Expansions
Differential Expansion HP-DE and LP-DE are very
important measurement and this measurement is the
relative measurement of rotor`s axial thermal growth with
respect to the casing.
Perpendicular collars at each side of the rotor can be
measured by either a single Eddy probe transducer
mounted on either side of the collar measuring the
compensation of both sides.
HP-DE uses the single non- contact probe concept
measuring the total expansion/contraction of the rotor with
respect to turbine casing.
LP-DE uses two non contact probe concept to measure the
total expansion/contraction of the rotor with respect to
casing using the compensation of both probes.

21. Probe location
HP-DE is installed in the first bearing.Expanssion or
contraction is measure between rotor collar and casing
.LP-DE is installed in the third bearing, its output is
compensation of two sensors which are located on both
side of the rotor collar.
 HP-DE
 Sensor :25mm differential expansion probe(1)
 Transmitter : 25mm proximity transducer
 Voltage gap :5V dc between sensor and turbine
 LP-DE
 Sensor :25mm LP differential expansion probe(2)
 Transmitter :25mm proximitor transducer

23. BEARING AND THRUST PAD TEMPERATURE
Bearing and Thrust pad temperature is continuously monitored
the and compare the values to the system set values.
 BEARING TEMPERATURE:
 Alarm value 105 deg
 Shut down value 115 deg
 HI THRUST PAD TEMPERATURE:
 Alarm value 100 deg
 Shut down value 110 deg

24. TURBO SUPERVISORY INSTRUMENTS LOCATION

25. THANK YOU