turbine specification

8/12/2019 Turbine Specification

1/19


2/19

Max. continuous rating : in MW

Turbine speed : 3000 rpm ( N = 120 * f / P )

Steam condition at stop valves : in Kg/cm2 @ C

Steam flow : in T/hr

No. of stages : ( velocity + HP + LP )

Weight & material of rotor : in T ( NiCrMo steel forging )

No. of governor valves : 2 ( size : in mm )

Barring gear speed : 2 rpm

Relay oil pressure : in Kg/cm2

Lubrication oil pressure : in Kg/cm2

HP section material : Moly. Van. Steel casting

LP section material : Boiler quality MS plate fabricated


3/19

SPEED ECCENTRICITY

DIFFERENTIAL EXPANSION (ROTOR)

OVERALL EXPANSION (CASING)

VIBRATION (4 Channels)

POSITION INDICATION (6 Channels)


4/19

EDDY CURRENT :

It is an electric current induced within the body of a conductor whenthat conductor is in a region where there is a change in magnetic flux.It has the property of opposing the source, that produces it.

EDDY PROBE :

Eddycurrent pickup makes use of this property. It has a coil embeddedin its tip which is energized by a constant RF current which sets up anelectro magnetic field between the tip and the observed surface ortarget which is made of an electrically conductive material. Eddycurrents are induced in the target surface which consume some energyfrom the electromagnetic field that produces it. Due to this, there is avariation in the energizing current proportional to the probe target

distance which is sensed by the driver circuit that converts thesechanges into varying voltage signal.


5/19

A toothed wheel with 30 teeth is attached to the turbine shaft at theexciter end.

An eddy current pickup is mounted at close proximity to the wheel andis excited by its driver circuit.

When the teeth get closer to the pickup, more eddy currents areinduced in it and hence, more loading effect on the coil and less voltagesignal output

When the pickup senses the slots, due to more distance between thetarget and the pickup coil, less loading effect and more voltage sensed

Hence, passage of a slot and a tooth represent a cycle (a high + a low)Since there are 30 of them, for one rotation of the wheel, 30 such pulses/ cycles are produced which are fed to a F/V circuit conditioned intovoltage and current outputs suitable for indicating and recording.


6/19

Speed = Pulse per second rps = P x 60 rpm

No. of teeth T

EXAMPLE :

Supposing the turbine rotates at 3000 rpm. For 1 min = 3000 revolutions

For 1 sec = 3000/60 = 50 revolutions (or) 3000 rpm = 50 rps

We know for 1 revolution, the speed sensor output is 30 pulses ( T = 30 )

For 50 revolutions, P = 50 x 30 = 1500 pulses

Therefore, speed = P x 60 rpm = 1500 x 60 rpm = 3000 rpm

T 30


7/19

EDDY PROBE

TOOTHED WHEEL

MATCHED CABLE

TURBINESHAFT

Rotor speed has a direct relationship with the

frequency of the output current generated from

the alternator.

We know,

f = PN

120

And that, freq. = 50 Hz and minimum possible No.

of poles = 2, which gives the speed at 50 Hz as,

N = 120f = 120 x 50 = 3000 rpm

P 2

Hence, speed can be calculated from the output

frequency; or, vice versa.


8/19

EDDYPICKUP

CONVERTER PULSESHAPER

F/VCONVERTER

O/PAMPLIFIER

V/ICONVERTER

REC

Current O/Pto Data Logger

SPEED MEASUREMENT CHANNEL SCHEMATIC

Range : 04000 rpm


9/19

Shaft eccentricity is the radial motion of theshaft with respect to the bearing or casing.In other words, itsthe out of turn excursionof the shaft around its axis.

A high frequency RF signal is generated bythe Oscillator/Demodulator, sent throughthe extension cable and radiated from theProbe tip. Eddy currents are generated inthe surface of the shaft. The driverdemodulates the signal and provides a

modulated DC Voltage where the DC portionis directly proportional to gap (distance)and the AC portion is directly proportionalto radial vibration (Eccentricity).

In this way, an Eddy Current Transducer canbe used for both Radial Vibration and

distance measurements such as ThrustPosition and Shaft Position.

EDDY PROBE


10/19

EDDYPROBE CONVERTER

INPUTAMP. DC AMP.

AC AMP.FW RECT

LPF

INV. AMP

O/P AMP.

V/ICONVERTER

CURRENTO/P

N 300 RPM

ECCENTRICITY CHANNEL SCHEMATIC

E > 100 m

REC

Range : 0500 m p-p


11/19

Differential Expansion is the measureof relative axial expansion betweenturbine shaft and the casing whichoccurs due to the presence of different

temperature gradients and due therotor, cylinder, blades etc., being madeof different materials.

Differential Expansion is consideredpositive when the shaft moves (i.e., theshaft expands more than the casing)

towards the alternator and negativewhen it moves towards the turbine.

The movement of the shaft is sensed bythe eddy current probes by means ofthe probe-collar distance variation. asthe distance between one arrangement

decreases, it increases with the other.

Collars

Eddy Probe (A)

MatchedCable

B


12/19

Range : - 4 mm to + 8 mm

When DE occurs, the converter output of one probe say, B is less (distance, less);while the output of other (A) is more as the distance between the probe and thetarget is more. Output of these converters are given to respective inputamplifiers whose outputs are fed to a summing amplifier. The output amplifierfurther conditions the output to the required level to be fed to the indicator,recorder and the data logger.

A

B

A

B

A

B

A + B

Probe Converter Input Amp. Summing Amp. Output Amp.

D.E -2.4 mm / +3.4 mm

REC

DIFF. EXPANSION CHANNEL SCHEMATIC


13/19

Vibration refers to mechanical

oscillations about an equilibrium point.Vibration is occasionally desirable.

For example the motion of a tuning fork, thereed in a woodwind instrument orharmonica, or the cone of a loudspeaker isdesirable vibration, necessary for thecorrect functioning of the various devices.

More often, vibration is undesirable,wasting energy and creating unwantedsound--noise. For example, the motions ofengines, electric motors, or any mechanicaldevice in operation are usually unwantedvibrations. Such vibrations can be caused byimbalances in the rotating parts, unevenfriction, the meshing of gear teeth, parts

that are dragging together, etc.


14/19

SPRING

MOVINGCOIL

CASE

STATIONARYMAGNET

CONNECTORVibration measurement is done all thebearings of the turbo alternator set exceptthe last bearing (No.5) at the exciter end.

The detector is a velocity type transducerwith a moving coil in a permanentmagnetic field. When the bearing pedestalvibrates, the seismic mass will moverelative to the housing, thereby moving the

measuring coil in and out of the magneticfield. This induces an emf in the coil whichis proportional to velocity of the vibration.

The induced emf is integrated, amplifiedand rectified to give peak to peak vibration

displacement to be indicated and recorded.


15/19

VIBRATION

PICKUP

AC AMP, Integrator PEAKDETECTOR O/P AMP.

V/ICONVERTER

REC

VIB 75 m

CURRENT O/P TODATA LOGGER

VIBRATION CHANNEL SCHEMATIC

Range : ( 0250 m pk-pk )


16/19

0 10 20 30 40 mm O.E 10 mm

REC

Range : 040 mm

ACTUATOR FROM TURBINE CASINGAT FRONT PEDESTAL SIDE

Overall expansion is the expansion of turbinecasing as measured at the front pedestalwhich expands along with the casing withrespect to the foundation. Itsmeasured witha linear potentiometer sensor.


17/19

Speeder gear and load limiting gearpositions are sensed by rotarypotentiometers. The rotary motion

being transmitted through gearmechanism to the wiper of the pot.

CIES (Combined Isolation Emergency Stopvalves) and Governor valve positions aresensed by linear potentiometers. The linear

motion of their shaft transmitted bysuitable actuator mechanisms.


18/19

Overall expansion and linear position indication (of valves) are thesedays sensed by LVDTs, instead of potentiometers

Vibrations are also sensed by piezoelectric accelerometer sensors( Q = F * d ; F = m * a. Hence, Q = m * a * d)

Speed sensors in a majority voting system (2 out of 3, for redundancyand to avoid spurious actuations) initiating over speed trip, instead ofmechanical trip rings

These are the few improvements that have come up since the initialdays.


19/19

turbine specification

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