] ] 235 > 550 5 18 15/12 50 2.0 2.0 > 50 Unit2
Test method DIN / ISO ASTM D 445 D 3427 D 974
Kinematic Viscosity at 40 C (ISO VG 46) Air release at 50 C
Neutralisation number Water content Foaming at 25 C
mm /s minutes mg KOH/g mg/kg ml sec sec minutes kg/m C C sec C
Code mg/kg mg KOH/g mg KOH/g Mm3
DIN 51 562-1 DIN 51 381 DIN 51 558-1 DIN 51 777-3
D 892 (Seq. 1) DIN 51 589-1 DIN 51 599 DIN 51 757 DIN/ISO 2592
DIN 51 794 DIN/ISO 14935 DIN/ISO 3016 ISO 4406 DIN 51 577-3 DIN 51
373 DIN 51 348 IEC 247 D 97 D 1401 D 1298 D 92
* The required system cleanliness is dependent upon the system
design. Suitable measures (e.g. filtration, separation) have to be
taken to achieve this cleanliness level.
Following fire Resistant Fluids are approved: Brand Supplier 1.
Reolube Turbofluid 46XC M/s. Chemtura, UK 2. Fyrquel EHC-N M/s.
Supresta, USA
Also refer to the following sections: [1] 5.3-0082 : Care of
control fluid
5.1-0140-04/2
Steam Turbine Description
HP Turbine Valve Arrangement
General ArrangementThe HP turbine has 2 main stop valves and 2
control valves located symmetrically to the right and left of the
casing. The valves are arranged in pairs with one main stop valve
and one control valve in a common body. The short length of the
admission section between the control valves and the casing results
in a very low steam volume in this section, which has a beneficial
effect on the shutdown characteristics of the turbinegenerator
unit.
Valve Actuation Steam flowThe main steam is admitted steam inlet
passing first the and then the control valves. valves the steam
passes casing(1). through the main main stop valves From the
control to the turbine Each main stop valve and control valve has a
dedicated hydraulic servomotor(3;5). The servomotors are mounted
above floor level so that they are accessible and can be easily
maintained.
BHEL Haridwar
5.1-0205-00
Steam Turbine Description
HP TurbineCasing
Barrel type CasingThe HP outer casing is designed as a
barreltype casing without axial joint. An axially split inner
casing (4) is arranged in the barrel-type casing(3) Because of its
symmetrical construction, the barrel - type casing retains its
cylindrical shape and remains leakproof during quick changes in
temperature (e.g. on start-up and shut down, on load changes and
under high pressures). The inner casing too is almost cylindrical
in shape as the joint flanges
are relieved by the high pressure acting from the outside and
can thus be kept small. For this reason, turbines with barrel type
casing are especially suitable for quick start-up and loading.
SealsThe pretensioned U-shaped seal ring(12), that is forced
against the axial sealing surfaces by the steam pressure and the I
shaped seal ring (16), that allows axial displacement of the inner
casing (4), seal the space between the inner casing (4) and the
barrel type outer casing (3) from the adjacent spaces.
Fig. 1 HP Turbine BHEL Haridwar 5.1-0210-01/1
Fig.2 Inlet Connection3 4 6 7 8 9 Outer casing Inner casing U
seal ring Cylindrical pin Breech nut Inlet pipe from main stop and
control valve
Connection to Main Stop and Control Valves The steam lines from
the main stop and control
valves are connected to the inlet connections of the outer
casing by Breech Nuts(8) (Fig.2) through buttress threading.
Sealing is achieved by U-seal rings(6) which is forced against the
outer sealing surface by inlet steam pressure. The annular space
around the sealing ring is connected to the condenser through a
steam leak-off line. Cylindrical pins(7) located at the joint
flange prevent rotation of the inlet pipe with respect to the outer
casing.
3 Outer casing 4 Inner casing 11 Fitted Key
3 Outer casing 4 Inner casing 10 Fitted Key Fig. 4 Centering and
supportsupport Fig. 4 Centering and of inner casing (Exhaust
side)
Fig. 3 Centering and support of Inner casing (Admission side)
5.1-0210-01/2
of
Inner casing (Exhaust side)
Attachment of Inner CasingThe inner casing (4) is attached in
the horizontal and vertical planes in the barrel-type casing(3) so
that it can freely expand radially in all directions and axially
from a fixed point when heating up while maintaining concentricity
relative to the turbine rotor. On the admission side, four
projections of the inner casing (4) and on the exhaust side three
projections fit into corresponding grooves in the barrel-type
casing (3). In the horizontal plane these projections rest on
fitted keys (10) and in the vertical plane they are guided by the
fitted keys (11) (Fig.3&4). Radial expansion is therefore not
restricted by this suspension. As shown in fig.6 the axial fixed
point of the inner casing is provided by a shoulder in the
barrel-type casing (3) against which a collar of the inner
casing(4) rests. The axial thrust to which the inner casing is
subjected is transmitted to and absorbed by the thrust ring (14)
via thrust pads(13). The thrust ring is held in position by support
ring (15).
3 4 16 17 18
Outer casing Inner casing I-seal ring Holding ring Hexagon head
screw
Outlet ConnectionsThe exhaust end of HPT has single outlet
connection from bottom. At the flange connection a U-seal ring (19)
is provided to prevent any leakage (Fig.1)
Fig. 5 I-Ring seal (Detail A from Fig. 1)
3 Outer casing 4 Inner casing 12 U- seal ring
13 Thrust pads 14 Thrust pads 15 Support ring
Fig. 6 Axial Retention ofInner casing and Centering in vertical
plane (Detail E from Fig.1)
5.1-0210-01/3
Steam Turbine DescriptionMoving and Stationary BladesThe HP
turbine with advance blading consists of 17drum stages. All stages
are reaction stages with 50% reaction. The stationary and moving
blades of all stages (Fig.1) are provided with inverted T-roots
which
HP Turbine Blading
1
A
2 3 B 4 The moving and stationary blades are inserted into
corresponding grooves in the shaft( 4) and inner casing (1) and are
caulked at bottom with caulking piece (5) .The insertion slot in
the shaft is closed by a locking blade which is fixed by taper pins
or grub screws. End blades are used at the joint plane in L/H &
U/H of inner casing along with predetermined interference. .
5
Gap sealingFig. 1 Drum Stages
1 Inner casing 2 Guide blade 3 Moving blade
4 Turbine shaft 5 Caulking piece
also determine the distance between the blades. The shrouds are
machined integral with the blades and forms a continuous shrouding
after insertion. st th From 1 . to 8 . stages are provided with 3DS
th th blades, 9 . to 13 . stages with TX blades and th 14 . to 17
th. stages with F blades.
Sealing strips(6) are caulked into the inner casing(1) and the
shaft (4) to reduce leakage losses at the blade tips. Cylindrically
machined surface on the blade shrouds are opposite the sealing
strips. The surfaces have stepped diameters in order to increase
the turbulence of the steam and thus the sealing effect. Should an
operational disturbance cause the sealing strips to come into
contact with opposite surfaces, they are rubbed away without any
considerable amount of heat being generated. They can easily be
renewed at a later date to provide the specified clearance.
BHEL Haridwar
5.1-0220-02
Steam turbine Description
HP TurbineShaft seals and Balance Piston
FunctionThe function of shaft seals is to seal the interior of
the casing from the atmosphere at the ends of the shaft on the
admission and exhaust sides.The HP Turbine has shaft seals in front
and rear. The front shaft seal is of labyrinth type, while the rear
shaft seal is of see through type. The difference in pressure
before and after the raised part of the shaft seal on the admission
side serves to counteract the axial thrust caused by steam
forces.The raised part is called Balance piston. The effective
seal
diameter is suited to the requirements for balancing the axial
thrust.
Gap SealsSealing between the rotating and stationary parts of
the turbine is achieved by means of seal strip(6) caulked into seal
rings (2,7,9) and into the rotor (3) (details D and E). The
pressure gradient across the seal is reduced by conversion of
pressure energy into velocity energy which is then dissipated as
turbulence as the steam passes through the numerous compartments
according to the labyrinth principles.
Fig. 1 Shaft Seal Admission side1 3 4 5 6 Inner casing 2 Seal
ring Turbine rotor Shaft seal cover Caulking wire Seal strip
Seal RingsThe seal rings (2), the number of which depends on the
pressure gradient to be sealed are divided into several segments as
shown in Section A-A, B-B and C-C and mounted in T -shaped annular
grooves in the inner casing (1 ) and shaft seal cover (4) such that
they are free to move radially. Each segment is held in position
against a shoulder by helical springs (11). This provides the
proper clearance for the seal gaps. Should rubbing occur, the
segment concerned can retreat. The heat developed by light rubbing
of the thin seal strip (6)
Fig. 2 Shaft seal Exhaust side BHEL Haridwar 5.1-0230-01/1
is so slight that it cannot cause deformation of the rotor (3).
When the turbine is started from the cold or warm state, the seal
rings naturally heat up faster than the casing. However, they can
expand freely In the radial direction against the centering force
of the helical spring (11). The shaft seals are axial-steam flow
noncontacting seals. In the region subjected to the low relative
expansion in the vicinity of the combined journal and thrust
bearing, the seal strips are caulked alternately into the shaft and
into spring-supported segmented sealrings in the casing, forming a
labyrinth to impede the outflow of steam (Detail D). In the region
subject to greater relative
expansion at the exhaust end, see through seals are used in
which the seal strips are located opposite each other, caulked into
the shaft and into seal rings centered in the outer casing (Detail
E). The outer seal rings can be removed for inspection and if
necessary, seal strips can be replaced during short turbine shut
down.
Steam SpacesSteam spaces are provided within the shaft seals.
From spaces Q and R leakage is drawn off to another part of the
turbine for further use. The steam seal header is connected to
space S. The slight amount of leakage steam which are still able to
pass the seal ring are conducted from the space T into the seal
steam condenser.
5.1-0230-01/2
Steam Turbine DescriptionArrangementThe front bearing pedestal
is located at the turbineside end of the turbine generator unit.
Its function is to support the turbine casing and bear the turbine
rotor. It houses the following components and instruments. Journal
bearing [1] Hydraulic turning gear [2] Main oil pump with hydraulic
speed transducer [3] Electric speed transducer [4] Overspeed trip
[5] Shaft vibration pick-up Bearing pedestal vibration pick-up
Details of casing supports and casing guides are given in
description 5.1-0280.
HP Turbine Front Bearing PedestalConnection Foundation of
Bearing Pedestal and
The bearing pedestal (1) is aligned to the foundation by means
of hexagon head screws that are screwed into it at several points.
On completion of alignment, the space beneath the bearing pedestal
is filled with special non-shrinking grout. The bearing pedestal is
anchored to the foundation by means of anchor bolts (13). The
anchor bolt holes are filled with gravel, which gives a
considerable vibration damping effect. The defined position of the
bearing pedestal on the foundation is established by a projection
in the middle of the bearing pedestal base engaging in a recess in
the Foundation. On completion of alignment, the remaining space in
this recess is likewise filled with grout .
1 Bearing pedestal 2 Main oil pump 3 Hydraulic speed transducer
4 Electric speed transducer 5 Gear coupling 6 Over speed trip Fig.1
Axial Section through HP Turbine Front Bearing Pedestal
7 Hydraulic turning gear 7 Hydraulic turning gear 8 Bearing
pedestal vibration pick-up 8 Bearing pedestal vibration pick-up 9
Shaft vibration pick-up 9 Shaft vibration pick-up 10 10 Journal
bearing Journal bearing 11 11 HP turbine rotor HP turbine rotor 12
12 Foundation Foundation
BHEL Haridwar
5.1-0240-01/1
Fig. 2 Cross section of main oil pump
Fig. 3 Cross Section of Journal Bearing
10 Journal bearing Also refer to the following information 12
Foundation 13 Anchor bolts 14 Hex head screw
5.1-0240-01/2
[4] 5.1-0760 Electric Speed Transducer Also refer to the
following information [1] 5.1-0270 Journal Bearing [2] 5.1-0510
Hydraulic Turning Gear [3] 5.1-1020 Main Oil Pump with Hydraulic
Speed Transducer [1] 5.1-0270 Journal Bearing [4] 5.1-0760 Electric
Speed Transducer [2] 5.1-0510 Hydraulic Turning Gear [5] 5.1-0920
Overspeed trip with Hydraulic Speed Transducer [3] 5.1-1020
MainOilPump [5] 5.1-0920 Overspeed trip
Staem Turbine Description
HP Turbine Rear bearing Pedestal
Arrangement The bearing pedestal is located between the HP and
IP turbines. Its function is to support the turbine casing and bear
the HP and IP turbine rotors. The bearing pedestal houses the
following turbine components: Combined journal and thrust bearing
Shaft vibration pick-up Bearing pedestal vibration pick-up Thrust
bearing trip (electrical) Details of casing supports and casing
guides are given in descriptions 5.1-0280 and 5.1-0350.
Connection Foundation
of
Bearing
Pedestal
and
The bearing pedestal is aligned on the foundation by means of
hexagon head screws that are screwed into it. On completion of
alignment, the space beneath the bearing pedestal is filled-in with
special non-shrinking grout. The bearing pedestal is anchored to
the foundation by means of anchor bolts. The anchor bolt holes are
filled with gravel, which gives a considerable vibration damping
effect. The defined position of the bearing pedestal on the
foundation is established by a projection in the middle of the
bearing pedestal base engaging a recess in the foundation. On
completion of alignment, the remaining space in the recess is
likewise filled with grout.
1 2 3 4 5 6 7 8
HP turbine rotor Combined journal and thrust bearing Bearing
pedestal vibration pick-up Shaft vibration pick-up Thrust bearing
trip (electrical) Coupling bolts IP turbine rotor Foundation
8
Fig. 1 Axial Section through the HP Turbine Rear Bearing
pedestal
BHEL Haridwar
5.1-0250-02/1
2 Combined journal and thrust bearing 8 Foundation 9 Hex head
screw Fig. 2 Cross Section through Combined Journal and Thrust
Bearing
9
8
10 11 12 13 14 15
Straight pin Anchor bolt Plate Round nut Hex nut Guard cap
Fig. 3 Connection between Bearing Pedestal and foundation
5.1-0250-02/2
Steam turbine DescriptionFunctionThe function of the combined
journal and thrust bearing is to support the turbine rotor and to
take the residual axial thrust. The magnitude and direction of
axial thrust to be carried by the bearing depends on the load
conditions of the turbine. This bearing is located in the bearing
pedestal between HPT & IPT. The thrust bearing maintains
desired axial clearances for the combined turbine generator shaft
system.
Combined Bearing
Journal
and
Thrust
Construction and Mode of OperationThe combined journal and
thrust bearing consists of the upper and lower bearing shells (4,
12), thrust pads (6), cap (2), spherical blocks (14, 16) and keys
(10, 17). The upper and lower halves (4, 12) of the bearing shell
are bolted and doweled at the horizontal joint by means of 4 taper
pins and 4 stocket-head screws. Section A-A
The journal bearing is constructed as elliptical sleeve bearing.
The bearing liners are provided with a machined babbit face;
additional scraping is neither necessary nor allowable. In order to
prevent the bearing from exerting a bending moment on the shaft, it
is pivotmounted on spherical support (16). The spherical block (14)
with shims (13,15), is bolted to the lower bearing shell (12). A
transverse projection in the upper part of the cap (2) and the
fitted key (3) prevent the bearing shells from rising. The bearing
shells are located laterally by keys (10). The bearing is supported
axillay against the bearing pedestal (1,9) by means of keys (17,
18) (Section H-H). This fixing is of great importance for axial
clearance in the whole turbine. Located at each end of the bearing
shell, babbitted thrust pads (6) form two annular surfaces on which
the integralily machined shaft collars run. Section B-B
1 Bearing pedestal, upper 7 Bearing liner 2 Cap 3 Key 4 Bearing
shell upper 5 Cowling with all baffle 6 Thrust pad 8 Turbine shaft
9 Brg. pedestal lower 10 Key 11 Oil line
12 Bearing shell,lower 13 Shim 14 Spherical block 15 Shim 16
Spherical support 25 Key a Shaft jacking oil
BHEL Haridwar
5.1-0260-01/1
These collars and thrust pads permit equal loading of the thrust
bearing in either direction. As shown in section N-N, the thrust
pads are of the tilting type, secured in place by pins (23) and
flexible mounted on split spring element (21). Temperature
Measurement Metal temperature of the journal bearing and thrust
pads is monitored by the thermocouples (19,20) (Section E-E and
G-G).
19 Thermocouple 20 Thermocouple Oil Supply Lubricating oil is
admitted to the bearing shells from one side via oil line (11) from
where it flows to the oil spaces milled into the upper and lower
bearing shells at the horizontal joint.
Oil leaving the journal bearing flows to the two annular grooves
adjacent to the bearing surface and then to the thrust pads (6).
Through the two oil return cowlings (5), oil is discharged into the
drain area in the pedestal (9) JackingOil Passages are located at
the lowest point in the lower bearing shell through which high
pressure jacking oil is supplied under the journal at low speed of
the turbine rotor (on start up or shutdown). Thus dry friction is
prevented and the breakaway torque on start-up with turning gear is
reduced. High pressure oil a flows under the journals via the oil
line and via openings in the lower bearing shell (12). O-ring (24)
located between the bearing liner (7) and the lower bearing shell
(12) prevents any oil from penetrating between the two elements
(Detail C). Any leakage passing the seal will drain off to the
bearing pedestal through a groove in the lower bearing shell. This
arrangement ensures that no oil penetrates between the bearing
liner and the bearing shell.
4 Bearing shell upper element 6 Thrust pad 12 Bearing shell,
lower
21 Spring 22 Key 23 Dowel pin
5.1-0260-01/2
Steam Turbine DescriptionConstruction The function of the
journal bearing is to support the turbine rotor. Essentially the
journal bearing consists of the upper and lower shells (3,6),
bearing cap (1), spherical block (7), spherical support (14) and
the key (11) .The bearing shells are provided with a babbit face.
The babbit surface of the bearing is precision machined and
additional scraping is neither necessary nor permissible. Both
bearing shells are fixed by means of taper pins and bolted
together. In order to prevent the bearing from exerting a bending
moment on the rotor (5), it is pivotmounted in the spherical
support (14). For this purpose the spherical block (7) with shims
(12,13) is bolted to the bearing shell (6) . A projection in cap
(1) with shims (9) fits into a
Journal Bearing HP frontbearing shells. Keys (8) are fitted on
both sides of the projection. The bearing shells are fixed
laterally by key (11) which are bolted to each other. Each key is
held in position in the bearing pedestal (10) by two lateral
collars. The temperature of the bearing bodies is monitored by
thermocouples (19) as shown in section c-c. Oil Supply Lubricating
oil is admitted to the bearing shells from one side and flows to
oil spaces that are milled into the upper shell at the horizontal
joint and are open to the rotor. The rotor (5) picks up oil from
oil pocket machined into the babbitting .The oil emerges from the
bearing shell where it is collected in the oil return cowling (4)
and drained into the bearing pedestal(10).
corresponding groove in the bearing shell (3) and prevents
vertical movement of the
1 2 3 4 5
Cap 6 Lower baering shell Tab Washer 7 Spherical block Upper
bearing shell 8 Key Oil return Cowling 9 Shim Turbine Rotor 10
Bearing pedestal
11 12 13 14 15
Key Shim Shim Spherical support Shim
BHEL Haridwar
5.1-0270-01/1
Jacking oilAs shown in Detail B, a threaded nozzle( 17) is
arranged at the lowest point of the lower bearing shell (6) through
which high pressure lift oil is supplied to the space below the
journals when the rotor is turning at low speed (on startup and
shutdown).This high pressure oil floats the shaft to prevent dry
friction and overcome breakway torque during start-up on the
hydraulic turning gear. A seal (18) prevent high pressure oil from
penetrating the space between threaded nozzle and ring (16) and
thus from lifting the babbit. Any leakage oil can drain through
passages in the bearing shell below the ring.
Removal of Bearing ShellsNot only the upper shell(3) but also
the lower bearing shell(6) can be removed without the removal of
rotor (5). To enable this to be done the shaft is lifted slightly
by means of jacking device but within the clearance of the shaft
seals. The lower bearing shell can then be turned upwards to the
top position and removed.
16 Ring 17 Threaded nozzle 18 Sealing ring 19 Thermocouple
5.1-0270-01/2
Steam Turbine DescriptionSupports The turbine casing is
supported on the support horns such as to make allowance for the
thermal expansion. It is essential for the casing to retain
concentric alignment with the rotor, which is supported
independently.
HP Turbine Casing Supports and GuidesThe turbine casing (2) is
supported with its two front and two rear support horns on the horn
supports of the bearing pedestal (1,3) at the turbine centerline
level. This arrangement determines the height of the casing and
also allows thermal expansion to take place in the horizontal plane
by the support horns
1 2 3
Front bearing pedestal HP turbine Rear bearing pedestal
Fig.1 Connection between Turbine Casing and Bearing
Pedestals
BHEL Haridwar
5.1-0280-01/1
sliding on the sliding pieces (6) of the bearing pedestals (1
;3). To prevent lift-off of the turbine casing (2), holders (4)
hold down projections of the support horns which engage in mating
recesses in the bearing pedestal. When the turbine is being
erected, a clearance s is maintained between the thrust bar(5) and
the turbine casing support horn projection. Guides The central
location of the turbine casing at right angle
to the turbine centerline is provided by the guides shown in
section B-B and E-E. These guides allow the turbine casing to
expand freely.
Fixed Point The fixed point for the turbine casing (2) is
located at the horn support on HP-IP pedestal at the turbine
centerline level and is formed by the parrallel keys (16). Axial
expansion of the turbine casing (2) originates from this point.
1 Front bearing pedestal 2 HP turbine 4 Holder 5 thrust bar 6
sliding piece 7 Plate 8 parallel key 9 plate
10 11 12 13 14 15 16
Sliding piece Plate Parallel key Scale indicating casing
expansion Sliding piece Plate Parallel key
Fig. 2 Details of Casing Supports and guides
5.1-0280-01/2
Steam Turbine DescriptionDouble Shell Construction The casing of
the IP turbine is split horizontally and is of double shell
construction. A double-flow inner casing (3,4) is supported in the
outer casing (2,5) (Fig.1) Steam from the HP turbine after
reheating enters the inner casing from top and bottom through two
admission branches which are integral with the mid section of the
outer casing. This arrangement provides opposed double flow in the
two blade sections and compensates axial thrust. The centre flow
prevents the steam inlet temperature from affecting the support
horns and bearing sections.
IP Turbine CasingThe provision of an inner casing confines the
steam inlet conditions to the admission section of this casing.
While the joint flange of the outer casing is subjected only to the
lower pressure and temprature effective at the exhaust from the
inner casing. This means that the joint flange can be kept small
and material concentrations in the area of the flange reduced to a
minimum. In this way, difficulties arising from deformation of a
casing with flange joint due to non uniform temperature rise e.g.
on start-up and shut down, are avoided. The joint of the inner
casing is relieved by the pressure in the outer casing so that this
joint has to be sealed only against the resulting differential
pressure.
.
BHEL Haridwar
5.1-0310-01/1
Steam Inlet and Extraction Connection The angle ring (9) are
provided at the connection of admission and extraction branches
with the inner casing (3,4) (Detail D Fig. 2 & 3). One leg of
the angle ring (9) at such a connection bears against the back of
the collar of the threaded ring (7) in the outer casing while the
other fits into an annular groove in the inner casing. The threaded
ring (7) is fitted in such a way that the short leg of the angle
ring can slide freely between the collar of the threaded ring and
the outer casing. The steam pressure prevailing on the inside,
forces the angle ring against the face of the outer casing. . The
tolerances of the annular grooves in the inner casing are
dimensioned to allow the long legs of the angle ring (9) to slide
in the groove. The angle rings are flexibly expanded by the
pressure on the inside and their outer areas forced against the
annular grooves to provide the desired sealing effect
While providing a tight seal, this arrangement permits the inner
casing to move freely in all directions. Attachment of Inner Casing
Due to the different temperatures of the inner casing relative to
the outer casing, the inner casing is attached to the outer casing
in such a manner as to be free to expand axially from a fixed point
and radially in all directions, while maintaining the concentricity
of the inner casing relative to the shaft. The steam admission
connections and the extraction connections are designed to avoid
any restrictions due to thermal expansion. The inner casing is
attached to the outer casing in the horizontal and vertical
plane.
5.1-0310-01/2
In the horizontal plane, as shown in details E and F (Fig. 4
& 5) the four support horns of the top half inner casing (3)
rest on plates (13) which are supported by the joint surface of the
bottom half outer casing (5). The shoulder screws (12) are provided
with sufficient clearance to permit the inner casing to expand
freely in all directions in the horizontal plane. Thermal expansion
in the vertical direction originates from the point of support at
the joint. This ensures concentricity of the inner casing relative
to the rotor (1) in this plane. The support horns provided at the
bottom half inner casing (4), project into the recesses in bottom
half outer casing (5) with clearance on all sides. Located on top
of each support horn is a spacer disc (11) whose upper surface has
a clearance s to the flange face of the top half outer casing (2).
This clearance thus determines the lift of the inner casing. As
shown in details E, the inner casing is located axially by the
fitted keys (10) arranged on both sides of the support horns of the
bottom half inner casing (4). Thermal expansion in the axial
direction originates from these points. Radial expansion is not
prevented by these fitted keys, as they are free to slide in the
recesses of the bottom half outer casing. Shoulders on the bottom
half outer casing (5) project into corresponding recesses in the
bottom half inner
casing (4) and together with the fitted keys (14) provide a
centering system for the inner casing (3, 4) in the transverse
plane This arrangement allows axial and radial expansion of the
inner casing relative to the outer casing while the fitted keys
(14) maintain transverse alignment.
5.1-0310-01/3
Steam Turbine DescriptionMoving and Stationary Blades The IP
turbine with advance blading consists of 2x12 (double flow) drum
stages. All stages are reaction stages with 50% reaction. The
stationary and moving blades of all stages are provided with
inverted T -roots in moving blade and hook type roots in Guide
blade which also determine the distance between the blades. All
these blades are provided with integral shrouds, which after
installation form a continuous shroud. The moving and stationary
blades are inserted into appropriately shaped grooves in the rotor
(4) and in the inner casing (1) and are bottom caulked with
caulking material (5). The insertion slot in the rotor is closed by
a locking blade which is fixed by grub screws. End blades, which
lock with the horizontal joint are used at the horizontal joint of
the inner casing (1).
IP Turbine BladingGap SealIng Sealing strips (7) are caulked
into the inner casing (1) and the rotor (4) to reduce leakage
losses at the blade tips. Cylindrically machined surfaces on the
blade shrouds are opposite the sealing strips. These surfaces have
stepped diameters in order to increase the turbulence of the steam
and thus the sealing effect. In case of an operation disturbance,
causing the sealing strips to come into contact with opposite
surfaces, they are rubbed away without any considerable amount of
heat being generated. They can then easily be renewed at a later
date to provide the specified clearances.
1
1 Inner Casing 2 Guide Blade 3 Moving Blade 4 Turbine Shaft 5
Caulking piece 6 Sealing strip 7 Caulking wire
5
2
6
4
7 5
BHEL Haridwar
5.1-0320-02
Steam Turbine Description
IP Turbine Shaft Seals
Function The function of the shaft seals is to seal the interior
of the turbine casing against the atmosphere at the front (thrust
bearing end) and rear shaft penetrations of the IP turbine. The
shaft seals are axial-steam-flow noncontacting seals. In the region
subject to low relative expansion in the vicinity of the combined
journal and thrust bearing, the seal strips are caulked
alternatively into the shaft and into springsupported segmented
rings in the casing, forming a labyrinth to impede the outflow of
steam. In the region subject to greater relative expansion at the
exhaust end, see-through seals are used, in which the seal strips
are located opposite each other,
caulked into the shaft and into seal rings centered in the outer
casing. The outer seal rings can be removed for inspection and if
necessary seal strips can be replaced during a short turbine shut
down keeping module in place. Gap Sealing Sealing between the
rotating and stationary elements of the turbine is achieved by
means of seal strip (9) ,caulked into seal rings (3;5) and into the
rotor (4) (details A and C). The pressure gradient across the seal
is reduced by conversion of pressure energy into velocity energy
which is then dissipated as turbulence as the steam passes through
the numerous compartments according to the labyrinth principle.
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Seal Rings The seal rings (3), the number of which depends on
the pressure gradient to be sealed are divided into several
segments as shown in Section BB and mounted in grooves in the rings
such that they are free to move radially. Each segment is held in
position against a shoulder by helical springs (6) and by the steam
pressure above the seal rings (3). This provides the proper
clearance for the seal gaps. Should rubbing occur the segments
concerned can retreat. The heat developed by light rubbing of the
thin seal strips (9) is so slight that it cannot cause deformation
of the rotor (4).
When the turbine is started from the cold or warm state, the
seal rings naturally heat up faster than the mounting rings.
However. they can expand freely in the radial direction against the
centering force of the helical springs (6). Steam Spaces Steam
spaces are provided within the shaft seals. From space P leakage is
drawn off to the steam seal header. The slight amount of leakage
steam which are still able to pass the seal ring are conducted from
the space R into the seal steam condenser.
5.1-0330-01/2
Steam Turbine Description
IP TurbineRearBearing Pedestal
Arrangement The bearing pedestal is located between the IP and
LP turbines. Its function is to support the turbine casing and bear
the weight of IP and LP rotors. The bearing pedestal houses the
following turbine components: Journal bearing Shaft vibration
pick-up Bearing pedestal vibration pick-up Hand barring arrangement
of Bearing Pedestal and
Connection Foundation
The bearing pedestal is aligned on the foundation by means of
hexagon head screws that are screwed into it at several points. On
completion of alignment the space beneath the bearing pedestal is
filled with special non shrinking grout. The bearing pedestal is
anchored to the foundation by means of anchor bolts. The anchor
bolt holes are filled with gravel which gives a considerable
vibration damping effect.
BHEL Haridwar
5.1-0340-02
Steam Turbine Description
IP Rear Journal Bearing
Construction The function of the journal bearing is to support
the turbine rotor. Essentially, the journal bearing consists of the
upper and lower shells (3, 6), bearing cap (1), torus piece (7),
cylindrical support (14) and the keys (10). The bearing shells are
provided with a babbit face which is precision machined. Additional
scraping is neither necessary nor permissible. Both bearing shells
are fixed by means of taper pins and bolted together. In order to
prevent the bearing from exerting a bending moment on the rotor
(5), it is pivotmounted in the cylindrical support (14). For this
purpose, the torus piece (7) with shims (12, 13) is bolted to the
bearing shell (6). A projection in cap (1) with key (9) fits into a
corresponding groove in the bearing shell (3) and prevents vertical
movement of the bearing shells. Centering of the bearing shells in
the vertical plane is achieved by means of keys (8).
The bearing shells are fixed laterally by spacers (10) which are
bolted to each other. Each spacer is held in position in the
bearing pedestal (11) by two laterall collars. The temperature of
the bearing bodies is monitored by thermocouples (15) as shown in
section C-C.
Oil Supply Lubricating oil is admitted to the bearing shells
from both sides, from where it flows to oil spaces milled into the
upper and lower shells at the horizontal joint that are open to the
rotor end. Oil from the oil space machined in the babbitting is
carried through the rotor (5) and emerges from the bearing shell
from where it is collected in the oil return cowling (4) and
drained into the bearing pedestal (11).
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Jacking Oil As shown in section B-B, two threaded nozzles (17)
are arranged at the lowest point of the lower bearing shell (6)
through which high pressure oil is supplied to the space below the
journal when the rotor is turning at low speed (on start-up and
shutdown). This high pressure oil floats the shaft to prevent dry
friction and overcome breakaway torque during startup, thus
reducing torque requirements of the hydraulic turning gear. A seal
(18) prevents high pressure oil from penetrating the space between
threaded nozzle and ring (16) and thus from lifting the babbit. Any
leakage oil can drain through passages in the bearing shell below
the ring. Removal of Bearing Shells Not only the upper shell (3)
but also the lower bearing shell (6) can be removed without the
removal of rotor (5). To enable this to be done, the shaft is
lifted slightly by means of jacking device but with in the
clearance of the shaft seals. The lower bearing shell can then be
turned upwards to the top position and removed.
5.1-0345-01/2
Steam Turbine DescriptionThe turbine casing is supported on the
support horns such as to make allowance for the thermal
expansion.
IP Turbine Casing Supports and GuidesIt is essential for the
casing to retain concentric alignment with the rotor which is
supported independently
1 HP Turbine rear bearing pedestal 2 IP turbine 3 IP turbine
rear bearing pedestal
Fig.1 Connection between turbine casing and bearing pedestal
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The turbine casing (2) is supported with its two front and two
rear support horns on the bearing pedestals(1,3) at the turbine
centerline level. This arrangement determines the height of the
casing and also allows thermal expansion to take place in the
horizontal plane by the support horns sliding on the sliding pieces
(6;16) of the bearing pedestals (1,3). To prevent lift off the
turbine casing (2), holders (4;15) hold down projections of the
support horns which engage in mating recesses in the bearing
pedestal. When the turbine is being erected, a clearance s is
established between the thrust bars (5;14) and the turbine casing
(2) support horn projection. Guides The central location of the
turbine casing at right angles to the turbine centerline is
provided by the guides shown in section B.B .These guides allow the
turbine casing to expand freely. Fixed Point The fixed point for
the turbine casing (2) is located at the front horn support at the
turbine centerline level and is formed by the parallel keys
((7;10). Axial expansion of turbine casing (2) originates from this
point
5.1-0350-01/2
Steam Turbine DescriptionConstruction The LP turbine casing
consists of a doubleflow unit and has a triple shell welded casing.
The outer casing consists of the front and rear walls, the two
lateral longitudinal support beams and the upper part. The front
and rear walls as well as the connection areas of the upper part
are reinforced by means of circular box beams. The outer casing is
supported by the ends of the longitudinal beams on the base plates
of the foundation.
LP Turbine Casing
Inlet Connections Steam admitted to the LP turbine from the IP
turbine flows into the inner casing (4,5) from both sides through
steam inlet nozzles before the LP blading Expansion bellows are
provided in the steam piping to prevent any undesirable deformation
of the casings due to thermal expansion of the steam piping.
1 2 3 4
Outer casing, upper half Diffuser, upper half Inner outer casing
upper half Inner- inner casing, upper half
5 6 7 8
Inner inner casing, lower half Inner outer casing lower half
Diffuser lower half Outer casing lower half
Fig. 1 LP Turbine (Longitudinal section) BHEL Haridwar
5.1-0410-00/1
Arrangement of Inner Casing in Outer Casing The LP casing has a
double-flow inner casing. This inner casing is a double shell
construction and consists of the outer part (3,6) and the inner
part (4,5). The inner shell is suspended in the outer shell to
allow thermal movement and carries the front guide blade rows. The
rear guide blade rows of the LP stage are bolted to the outer shell
of the inner casing. The complete inner casing is supported in the
LP outer casing (1,8) in a manner permitting free radial expansion
concentric with the shaft and axial expansion from a fixed point
(Fig.2). Support and Guiding of Outer Casing The outer casing rests
with the brackets at the end of the longitudinal beam on the base
plates fixed to the foundation crossbeam. The outer casing of the
LP turbine is axially fixed at the respective front brackets
(Fig.2). In the lower area of the circular beams which reinforce
the front and rear walls of the outer casing, the casing is guided
in the vertical centre plane (Fig.1, 3) which takes the radial and
axial expansion into account.
Two guide plates are welded vertically to the lower inner bend
of each of the beams. The guiding piece (12) which is rigidly
connected to the foundation crossbar, fits between these plates.
Fitted pieces(11) inserted between the square guiding piece(12) and
the plates maintain alignment of the casing in the centre plane and
permit expansion transverse to the axis of the machine. Support and
Guiding of Inner Casing in Outer Casing The complete assembled
inner casing rests in the horizontal plane with 4 brakets on the
sliding piece(15, 18) placed in the plates bolted to the
longitudinal support beam of the casing. The two brackets (detail C
Fig.5) on the turbine side are fixed in the axial direction by
fitted keys (16) as opposed to the brackets on the generator side
(detail D Fig.6) which are not fixed. Any thermal expansion in the
axial direction thus originates from here. The spacer bolts( 17)
prevent lifting of the inner casing. The clearance of these spacer
bolts in the holes of the brackets is dimensioned to permit the
inner casing to expand horizontally on sliding piece (15) of the
fixed support transverse to the axis of the machine, and on sliding
piece (18) of the nonfixed support transverse and parallel to the
machine axis. As thermal expansion in the vertical direction
originates at approximately the level of the horizontal.
5.1-0410-00/2
Fig.3 Guiding of the Outer Casing joint, the concentricity of
the inner casing with the shaft is ensured in this plane. As shown
in detail E (Fig.2,4) two casing guides are located at the lower
half (6) of the outer shell to prevent any transverse displacement
of the inner casing from the centerline of the turbine. Radial and
axial expansions is not prevented by fitted keys(14) in these
casing guides Suspension of the Inner Shell The inner shell (4,5)
is suspended in the outer shell (3,6) in the horizontal plane and
is guided axially in the vertical plane (Fig.7and 8). In the
horizontal plane, the upper half (4) of the inner shell is
supported by four brackets resting on the support plates (21,22)
located at L and M of the joint face of the lower half of the outer
shell (Fig.9 & 10). The brackets of the upper part (3) of the
outer shell which project over the cover plates (20) , prevent
lifting of the inner shell. The slight clearance between these
cover plates and the brackets permits free horizontal expansion of
the inner shell in all directions at the support points. Thermal
expansion in the vertical plane originates at the joint face. This
ensures concentricity of the inner shell with the shaft in this
plane. The brackets of the inner shell, lower half (5) project into
recesses of the outer shell, lower half (6) These brackets are
provided with clearance on all sides and
serve to align the inner shell, lower half (5) in the outer
shell, lower half (6) by the use of jacking bolts during erection.
On the IP turbine side, 2 fitted keys (19) are inserted between
each bracket and recess. As shown in detail L, these fitted keys
fix the inner shell in the axial direction and thermal expansion
thus originates from here
5.1-0410-00/3
3 Outer shell, upper half 4 Inner shell, upper half 5 Inner
shell, lower half 6 Outer shell, lower half Fig. 7 Inner Casing,
Longitudinal Section In the vertical plane 4 centering pins (26)
which are guided in bushings (25) are provided for the suspension
as shown in detail A Fig. 11. The lower ends of the centering pins
are fitted into keys (27) which slide in axial grooves in the inner
shell. This arrangement permits axial displacement of the inner
shell relative to the keys (27) and vertical displacement along the
axis of the centering pins(26) while displacement transverse to the
axis of the unit prevented by the keys. Thermal expansion
transverse to the axis of the unit originates from these keys so
that concentricity of the inner shell with the shaft is also
maintained in this plane. The bushings (25) have an eccentric bore
and by turning them during alignment of the inner casing, the inner
shell can be moved laterally. After the alignment has been
completed, the bushings are fixed in position by grub screws.
5.1-0410-00/4
Steam Turbine Description
Atmospheric Relief Diaphragm
Atmospheric relief diaphragms are provided in the upper half of
each LP exhaust end section to protect the turbine against
excessive pressure. In the event of failure of the low vacuum trips
the pressure in the LP turbine exhaust rises to an excessively high
level until the force acting on the rupturing disc (1) ruptures the
breakable diaphragm (2) thus providing a discharge path for the
steam. The diaphragm
consists of a thin rolled lead plate. To insure that the
remnants of the diaphragm and rupturing disc are not carried along
by the blow-off steam a cage with brackets (5) is provided. As long
as there is a vacuum in the condenser the atmospheric pressure
forces the breakable diaphragm and the rupturing disc against the
supporting flange (3).
BHEL Haridwar
5.1-0420-00
Steam Turbine Description
LP Turbine Blading, Drum Blading
Arrangement The drum blading stages 1 to 3 of the double flow LP
turbine are of reaction type with 50% reaction. They are Located in
the inner-Inner casing and form the initial stages of the LP
blading. The LP stages following these drum stages are described in
detail in next chapter. Guide and moving blades All guide and
moving blades of drum stages have integral shrouds, which after
installation form a continuous shrouding. The moving blades (7) of
the last drum stage are tapered and twisted. All stationary and
moving blades have T -roots which also determine the distance
between the blades. They are inserted into the matching grooves in
the turbine shaft (5) and inner casing (1) and are caulked in place
with caulking material (6). The insertion slot in the rotor is
closed by means of a locking blade which is secured in its position
by means of grub screws between shaft and lock blade .In casing,
blades at joint planes are fixed by means of grub screws. Inter
stage Sealing In order to reduce blade tip losses, tip to tip
sealings are provided in these stages. Thin sealing strips (9) are
caulked in inner casing (1) and turbine rotor (5). The sealing fins
are machined on the shrouds of moving and stationary blades
opposite to the sealing strips in inner casing or rotor (Detail A).
In the event of rubbing due to a fault , little heat will be
generated due to rubbing of thin sealing strips. These can be
renewed at a later date to provide the correct radial
clearances.
BHEL Haridwar
5.1-0430-01
Steam Turbine Description
LP Turbine Blading, Low Pressure Stages
Guide and Moving Blades The last three stages of the LP turbine
are also reaction stages. Each stage is made up of guide and moving
blades.
from steel sheets to form hollow blades. Suction slits are
provided in the blades of row (7). Through these slits water
particles on the surface of these last stage guide blades are drawn
away to the condenser. The moving blades (3) of first LP stage are
tapered,
The stationary blade rows (2, 5, 7) are made by welding inner
ring, blades and outer ring together to form Guide Blade Carriers
in two halves, that are bolted to inner outer casing (1). The
blades of rows 2 & 5 are of precision cast steels and the
blades of row 7 are made
twisted and have integral shrouds with T -root. The last two
stages of moving blades (6,8) have curved fir-tree roots (View-X)
which are inserted in axial grooves in the turbine shaft (4) and
secured by means of clamping pieces (11). Axial movement of the
blades
BHEL Haridwar
5.1-0440-01/1
is prevented by segments of locking plate segments (12) and the
end segments are spot welded at joint. The difference in
circumferential speed at the root and tip of the moving blades is
taken into consideration by the twisted design of the blades.
Inter stage sealing In order to reduce blade tip losses at the
stationary blade rows (2,5,7). sealing strips (9) are caulked into
turbine shaft. Opposite to this, sealing strips are also caulked on
the inner ring of stationary blade rows as shown in Detail A. This
arrangement permits favourable radial clearances to be attained. In
case of rubbing, the thin seal strips are worn away without
generating much heat. They can be easily replaced at a later date
to restore the required clearances.
5.1-0440-01/2
Steam Turbine DescriptionFunction The function of the axial
shaft seals situated between the bearing casings and the LP exhaust
casing is to seal the inner space of the LP exhaust casing against
atmospheric pressure at the passages through the shaft. Gap Sealing
The sealing effect between the moving and stationary parts of the
turbine is achieved by means of sealing strips (4) which are
caulked into the individual seal rings (2), The prevailing pressure
is reduced according to the labyrinth principle by conversion into
velocity with subsequent turbulence in many sections.
LP Turbine Shaft Seals
strips (4) due to this light pressure are so slight that it
cannot cause deformation of the rotor (5). When the turbine is
started from the cold or semi-warm state, the sealing rings
naturally heat up more quickly than the steam seal casings. They
can then expand radially without hindrance against the centering
force of the helical springs. Steam Spaces Steam spaces are
provided within the shaft seal. When the plant is started up and in
operation, sealing steam enters space Q to prevent air penetrating
the space, which is under a vacuum. The slight amount of steam that
passes the center seal ring is drawn off from space R into the seal
steam condenser.
Sealing Rings The sealing rings (2), the number of which depends
on the pressure existing in the turbine, are split into several
segments as shown in section A-A and arranged in Tshaped annullar
grooves in the steam seal casing (1) so that they can move
radially. Several helical sprir1gs (3) force each segment against a
shoulder and hold it in this position. This permits the correct
clearance in the sealing gaps. Should rubbing occur, the segments
concerned retreat. The frictional heat developed by the thin
BHEL Haridwar
5.1-0450-01
Steam Turbine Description
LP Turbine Rear Bearing Pedestal
Arrangement The bearing pedestal is situated between the LP
turbine and generator. Its function is to bear the weight of LP
rotor. The bearing pedestal following turbine components: contains
the
Bearing pedestal vibration pick-up Journal bearing Shaft
position measuring device Shaft vibration pick-up Connection
Foundation of Bearing Pedestal and
The bearing pedestal is aligned on the foundation by hexagonal
screws that are bolted into the bearing pedestal. To overcome
friction resistance, balls are arranged under the heads of these
hexagonal screws. After alignment the space under the bearing
pedestal is filled in with special nonshrink grout, resistant to
expansion and contraction. The bearing pedestal is also connected
to the foundation by means of anchor bolts.
BHEL Haridwar
5.1-0460-02
Steam Turbine DescriptionConstruction The function of the
journal bearing is to support the turbine rotor. Essentially, the
journal bearing consists of the upper and lower shells (3, 6),
bearing cap (1), torus piece (7), cylindrical support (14) and the
keys (10). The bearing shells are provided with a babbit face. The
bearing bore is precision machined and additional scraping is
neither necessary nor permissible. Both bearing shells are fixed by
means of taper pins and bolted together. In order to prevent the
bearing from exerting a bending moment on the rotor (5), it is
pivot-mounted in the cylindrical support (14). For this purpose,
the torus piece (7) with shims (12, 13) is firmly bolted to the
bearing shell (6). A projection in cap (1) with shims (9) fits into
a corresponding groove in the bearing shell (3) and prevents
vertical movement of the bearing shells.. Centering of the bearing
shells in the vertical plane is achieved by means of keys (8).
Journal Bearing
The bearing shells are fixed laterally by the keys (10) which
are bolted to each other. Each key is held in position in the
bearing pedestal (11) by two lateral collars. The temperature of
the bearing is monitored by thermocouples (15) as shown in section
C-C. Oil Supply Lubricating oil is admitted to the bearing shells
from both sides, from where it flows to oil spaces milled into the
upper and lower shells at the horizontal joint that are open to the
rotor end. Oil from the oil space machined in the babbitting is
carried through the rotor (5) and emerges from the bearing shell
from where it is collected in the oil return cowling (4) and
drained into the bearing pedestal (11). Lift Oil As shown in
section B-B threaded nozzles (17) are arranged at the lowest point
of the lower bearing
1 2 3 4
Cap Tab washer Upper bearing shell Oil return cowling
5 6 7 8
Rotor Lower bearing shell Torus piece Key
9 Shim 10 Key
13 Shim 14 Cylindrical support
11 Bearing Pedestal 12 Shim
BHEL Haridwar
5.1-0470-00/1
shell (6) through which high pressure oil is supplied during
start-up. This high pressure oil relieves the bearing to overcome
breakaway torque and prevent dry friction, thus reducing the torque
requirements of the hydraulic turning gear. The lift oil flows into
the above mentioned threaded nozzles (17) through passages in the
lower bearing shell (6). A seal (18) prevents high pressure oil
from penetrating the space between threaded nozzle and ring (16)
and thus from lifting the babbit. Any leakage oil can drain through
passages in the bearing shell below the ring. Removal of bearing
shells Not only the upper shell (3) but also the lower bearing
shell (6) can be removed without the removal of the shaft (5). To
enable this to be done, the shaft is lifted slightly by means of
the jacking device but within the clearance of the shaft seals. The
lower bearing shell can then be rotated to the top position and
removed.
15 16 17 18
Termocouple Ring Threaded nozzle Sealing ring
Also refer to tne following sections [1] 5.1-0510 Hydraulic
Turning Gear
5.1-0470-00/2
Steam Turbine DescriptionArrangement The hydraulic turning gear
is situated between the main oil pump and the journal bearing in
the HP turbine front bearing pedestal.
Hydraulic Turing Gear
Function The function of the hydraulic turning gear is to rotate
the shaft system at sufficient speed before start-up and after
shut-down in order to avoid irregular heating up or cooling down
and thus avoid any distortion of the turbine rotors. The air flow
set up by the blades along the inner wall of the casing during
turning operation provides good heat transfer conducive to
temperature equalization between upper and lower casing halves.
Operation During turning gear operation, the shaft system is
rotated by a blade wheel which is driven by oil supplied by the
auxiliary oil pump. This oil passes via a check valve into the
nozzle box (1) and from there into the nozzles (2) which direct the
oil jet in front of the blading. Return Oil Flow After passing the
blading, the oil drains into the bearing pedestal and flows with
the bearing oil into the return flow line. Manual Turning Gear A
manual turning gear is provided in addition to the hydraulic
turning gear to enable the combined shaft system to be rotated
manually. Lifting of Shaft To overcome the initial break-away
torque on start-up and to prevent dry friction, the bearings are
relieved during turning gear operation by lifting oil supplied from
below i.e. the shafts are lifted slightly.
BHEL Haridwar
5.1-0510-01
Steam Turbine Description
Mechanical Barring Gear
Function The turbine generator is equipped with a mechanical
barring gear, which enables the combined shaft system to be rotated
manually in the event of a failure of the normal hydraulic turning
gear. It is located at IP - LP pedestal
Operation Take the following steps to make the barring gear
ready for operation: Remove cover (2) unlatches at (7) and attach a
bar to lever (1). Barring of lever (1) will rotate the combined
turbine generator shaft system. After barring has been completed,
return lever (1) and pawl (6) to the position shown in figure and
secure lever (1) by means of latch (7) Replace cover (2). The
barring gear may only be operated after the shaft system has been
lifted with high-pressure lift oil. If it is hard to start turning
by means of the mechanical barring gear, this may be due to
incorrect adjustment of the jacking oil system or due to a rubbing
shaft. Before steam is admitted to the turbine. corrective action
must be taken
Construction The barring gear consists of a gear machined on the
rim of the turning gear wheel (10) and pawl (6). This pawl engages
the ring gear and turns the shaft system when operated by means of
a bar attached to laver (1). The pawl (6) is shown disengaged and
the lever (1) resting against a stop. The lever (1) is held in
position by latch (7).
BHEL Haridwar
5.1-0520-01
Steam Turbine DescriptionFunction When the turbine is started up
or shut down, the hydraulic jacking device is used to maintain the
oil film between rotor and bearings. The high-pressure oil is
forced under the individual bearing, thus raising the rotor. The
necessary torque from the hydraulic turning device or from the
manual turning device is reduced in this way. The highpressure oil
also provides motive force to hydraulic turning gear motor
installed in front bearing pedestal. Speed Limit Values In order to
avoid damage to the bearings, the jacking oil pump must be switched
on below a certain speed. The exact speeds for switching on and off
can be seen in the Technical data 2-0103. Jacking Oil Pump The
jacking oil pumps, one number AC (13) and one number DC(14) are
jack-screw immersion pumps situated on the tank (10) supply the
high pressure oil for the lifting device. The oil is drawn off
directly by one of the two pumps. The pressure oil piping of the
jacking oil pump that is not in operation is closed by the check
valve (12). In order
Hydraulic Jacking Device
to protect the jacking oil system from damage due to improper
switching ON of the jacking oil pump when the check valve (12) is
closed, a spring-loaded safety valve (11) is situated in the piping
between the jacking oil pump (13) and the check valve (12). The
necessary pressure in the system is kept constant by means of the
pressure-limiting valve (8). The pressure-limiting valve can be
relieved by the bypass valve (9). The superfluous flow from the
pump is conducted into the main oil tank. The necessary jacking oil
pressures are set for each bearing by the fine control valves (7)
in the oil pipes. Check valve (6) in the jacking oil pipes prevent
oil from flowing out of the bearings into the header during turbine
operation when the jacking oil system is naturally switched off.
Valve Arrangement The fine control valve (7) of the turbine
bearings, the check valves (6) and the pressure gauges are arranged
in boxes, which are connected laterally to the bearing
pedestals.
1 HP turblne 2 IP turblne 3 LP turblne 4 Generator 5 Exciter
6 Check Valve 7 Fine control valve 8 Pressure Limiting Device 9
Bypass Valve 10 Main Oil Tank
11 12 13 14 15
AC Motor driven lifting oil pump 16 Valve DC Motor driven
lifting oil pump c Drain Spring loaded safety valve Check valve
Duplex filter 5.1-0530-63-1
BHEL Haridwar
5.1-0530-63-02
Steam Turbine DescriptionThe turbine control system description
for 500 MW steam turbine comprises the following: General
Description Start-up Procedure Speed Control Electrical Speed
Measuring Protective Devices Overspeed Trip Test Testing of Stop
Valves Bypass Control System (General) Electro-hydraulic Bypass
Control (Electrical System) Electro-hydraulic Bypass Control
(Hydraulic System) Extraction Check Valve Swing Check Valve in CRH
line Testing of Swing Check Valves in the Cold Reheat Line
Automatic Turbine Tester, General Automatic Turbine Tester,
Protective Devices Automatic Turbine Tester, Stop Valves HP
Actuator Electro-hydraulic Gland Steam Pressure Control Control
System Diagram List of Parts Lubrication Chart Lubrication Chart,
Index Turbine generator unit MAA50HA001 MAB50HA001and MAC10HA001
comprises three-cylinder reheat condensing turbine with condenser
MAG10BC001 and a directdriven three-phase a.c. generator. The
turbine has a hydraulic speed governor MAX46BY001 and an electric
turbine controller. The hydraulic speed governor adjusts control
valves MAA10+20AA002 and MAB10+20AA002 by way of hydraulic
amplifier MAX45BY011 whilst the electric turbine controller acts on
these control valves by way of electro-hydraulic converter
MAX45BY001. Hydraulic amplifier MAX45BY011 and electro-hydraulic
converter MAX45BY001 are switched in parallel to form a minimum
gate. The system not exercising control is in its maximum
position.
General Description
The special operating conditions existing in reheat condensing
turbines necessitate additional control elements. On start-up of
the high-pressure boiler it is necessary to start up the turbine
straight away with a considerable steam rate and, due to the high
temperature in the reheater to admit steam to the reheater
immediately. As long as the HP section of the turbine is unable to
accommodate all the steam supplied by the boiler, the rejected
steam is routed directly to the reheater via HP bypass valve. The
steam from the reheater which cannot be accommodated by the IP
section with its control valves MAB10+20AA002 and reheat stop
valves MAB10+20AA001 is routed into condenser MAG10BC001 by way of
LP bypass stop & control valves MAN11+12AA001 and
MAN11+12AA002. The IP turbine must be fitted with its own control
valves to prevent steam remaining in the reheater from entering the
turbine via the IP and LP section and causing further acceleration
of the turbine after the main steam control valves have been closed
in the event of load rejection or trip. In addition, the steam
pressure in the main steam line would increase after sudden closure
of the main steam control valves, thus causing the HP by pass valve
to open, with the result that even more steam would flow into the
IP section of the turbine. It is the function of main oil pump
MAV21 AP001, driven directly by the turbine shaft, to supply oil
for bearing lubrication, for the oil circuit for the overspeed trip
test, and for the primary oil circuit, pressure in which is
generated by hydraulic speed transmitter MAX44AP001.Two
Electrically driven auxiliary oil pumps are provided for auxiliary
oil supply. The LP control fluid circuit (8 bar) and the HP
actuators of the main steam control valves, reheat control valves,
LP bypass stop & control valves (32bar) are supplied by two
full-load control fluid pumps installed in the control fluid tank.
The turbine is equipped with an electrohydraulic seal steam control
system, an electro-hydraulic bypass control system, an
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5.1-0600-01/1
automatic turbine tester for the protective devices, main and
reheat Stop & Control Valves and an automatic functional group
control.
5.1-0600-01/2
Steam Turbine DescriptionMode of Operation The turbine is
started up and brought up to speed with the assistance of the
control valves MAA10+20AA002 and MAB10+20 AA002. If the hydraulic
controller is to govern start-up, the reference speed setter
MAX46BY001 must be set to minimum speed during this process. In
this case the speed reference from the electric controller is at
maximum. If conversely, start-up is to be governed by the electric
controller, reference speed setter MAX46 BY001 is set to maximum
and the speed reference from the electric controller to minimum.
The combined stop and control valves are closed because the trip
fluid circuit is not yet pressurized. Turning hand-wheel KA01
clockwise or operating motor MAX47BY001M of start-up and load
limiting device MAX47BY001 in the close direction releases spring
KA06 in auxiliary follow up piston KA08 via the linkage, thereby
preventing a buildup of auxiliary secondary fluid pressure. The
hydraulic amplifier MAX45BY011 with follow-up pistons KA01 and KA02
is now in the control valves closed position so that a buildup of
secondary fluid pressure is prevented when main trip valves
MAX51AA005 and MAX51M006 are latched in. Further turning of
hand-wheel KA01 moves pilot valve KA02 of start-up and load
limiting device MAX47BY001 further downwards, admitting control
fluid first into the start-up fluid circuit and then into the
auxiliary start up fluid circuit. The start-up fluid flows to the
space above the pilot valve of test valves MAX47AA011+012 and
MAX47AA021+ 022, forcing them down against the action of the
springs. The auxiliary start-up fluid raises the pilot valves of
main trip valves MAX51AA005 and MAX51AA006, thereby moving them
into their normal operating position and permitting trip fluid to
flow to test valves MAX47AA011+012 and MAX47AA021+022 of the main
stop valves and reheat stop valves. At the same time, overspeed
trip release devices MAY10AA001 and 002 are latched in if they have
been tripped. The function of non return valve MAX42AA011 is to
interrupt
Start-up Procedure
transiently the fluid supply to solenoid valve MAX48AA202 from
the connection downstream of filters MAX42BT001 and MAX42BT 002
during latching in of main trip Valves MAX51AA005 and MAX51AA006 by
means of start-up and load limiting device MAX47BY001, because the
pressure drops in this line considerably for a short time as a
result of the high flow of fluid required to fill the drained trip
fluid system during this latching in-period. The pressure upstream
of solenoid valve MAX48AA202 is maintained via orifice MAX42BP022
during this period. This ensures that the solenoid valve remains in
the position shown. The auxiliary start-up fluid circuit at the
start-up and load-limiting device MAX47BY001 is fed from the system
down stream of filter MAX42BT003 (fluid supply during testing),
since the pressure in the system is subject to no significant
change during start-up. It is not possible to supply the hydraulic
fluid connection of solenoid valve MAX48AA202 from this system, as
this would have an in admissible effect on the trip fluid system
while the latching operation with the solenoid valves MAX48AA201
and MAX48AA202 during testing is taking place. After latching in,
the trip fluid circuit is closed. The trip fluid now flows to the
space above servomotor piston KA01 of stop valves MAA10+20AA001 and
MAB10+20 AA001 forcing it down against piston discs KA002.
Operation of the start-up and loadlimiting device is continued
until their lower limit position is reached. When hand-wheel KA01
is turned back or motor MAX47BY001M of start-up and load limiting
device MAX47BY001 is operated in the open direction, the control
fluid is allowed to drain first from the auxiliary startup fluid
circuit and then from the start-up fluid circuit. The pilot valve
of test valves MAX47AA011+012 and MAX47 AA021+022 are forced
upwards by the springs, whereupon the trip fluid above servomotor
piston KA01 slowly drains off. The pressure difference thus created
lifts both pistons together into their upper limit position, thus
causing main stop valves MAA10+20 AA001 and reheat stop valves
MAB10+20 AA001 to
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5.1-0610-01/1
open. Main trip valves MAX51AA005 and MAX51AA006 are now held in
their operating position by the fluid pressure beneath the
differential piston. Once the main & reheat stop valves are
open, further turning of hand-wheel KA01 or operation of motor
MAX47BY001M of the start -up and load limiting device in the open
direction will after passing through a certain dead range, cause
lever KA03 and sleeve KA04 to move further downwards, as a result
of which the auxiliary secondary fluid pressure begins to increase
and acts via hydraulic amplifier MAX45 BY011 and follow up pistons
KA01 and KA02 to gradually open control valves MAA10+20AA002 and
MAB10+20AA002. This brings the turbine up to about 85 to 90% rated
speed. Speed controller MAX46BY001 now cuts in to maintain turbine
speed. Start-up and load limiting device MAX47BY001 is then brought
into the fully open position. A pressure gauge MAX44CP501 and
electric speed transducer MYA001CS011-013 are used to measure
speed. Reference speed setter MAX46BY001 is used for further speed
run-up for connecting the turbine-generator unit in parallel and
for bringing it on load. Turning hand-wheel KA01 of the reference
speed setter or operation of motor MAX46BY001M increase the tension
of speed setting spring KA02 to increase speed. Since in
interconnected operation speed is determined by grid conditions,
actuation of the reference speed
setter has the effect of changing turbine output. Load
Limitation Start-up and load limiting device MAX47BY001 engages
mechanically in controller bellow KA09 of hydraulic speed
governor/controller MAX46BY001 so that it can serve simultaneously
as a load-limiting device. This means that opening of the control
valves MAA10+20AA002 and MAB10+20 AA002 is limited to an adjustable
setting. This setting is made manually or from the control room via
motor MAX47BY001M. Electro-hydraulic Turbine Controller If the
turbine is to be started up with the electro-hydraulic turbine
controller, the reference signal from the electric speed controller
must first be set to minimum so that this takes over running up the
turbine generator unit from turning speed. Start-up and load
limiting device MAX47BY001 is brought into its open position once
the stop valves have been opened. Slowly raising the speed
reference from the electric controller cuts in the electric speed
control system, and the turbine-generator unit is brought up to
rated speed and synchronized. Further loading is governed by the
electric power controller by increasing the load reference within
the admissible rate of load change.
5.1-0610-01/2
Steam Turbine Description
Speed Control
Speed control may be exercised either hydraulically or
electro-hydraulically. Hydraulic Control Main oil pump MAV21AP001
supplies the bearing and primary oil circuits with control oil
whilst hydraulic speed transmitter MAX44AP001 acts as a pulse
generator for the control circuit, providing a primary oil pressure
proportional to the speed. This oil pressure can also be read
directly from speed indicator pressure gauge MAX44CP501. This
primary oil pressure acts on diaphragm KA09 of hydraulic speed
governor MAX46BY001 against the force of speed setting spring KA02
which is tensioned by reference speed setter MAX46BY001.The travel
of diaphragm KA09, which can be limited by starting and load limit
device MAX47BY001, is transmitted by linkage KA03 to sleeves KA04
of auxiliary follow-up pistons KA08, the pistons KA05 of which are
held against the medium pressure by spring KA06. Medium drains off
according to the amount of port overlap between piston and sleeve
and a medium pressure corresponding to the tension of spring KA06
is built up. This auxiliary secondary medium pressure acts as a
pulse signal via pilot valve KA07 of hydraulic amplifier MAX45
BY011. Piston KA08 of this hydraulic amplifier assumes a position
corresponding to the auxiliary secondary medium pressure and
operates the sleeves of follow-up piston KA01and KA02 via a linkage
system. A feedback system stabilizes the position of pilot valve
KA07 and piston KA08 of hydraulic amplifier MAX45BY011. As already
described for auxiliary follow-up piston KA08, a secondary medium
pressure corresponding to the position of the sleeves and to the
related spring tension builds up in the follow up pistons of
hydraulic amplifier MAX45BY011. Any change in the position of
linkage KA03 results in a proportional change of the
secondary medium pressures in the follow-up pistons of the
hydraulic amplifier. The secondary medium circuits and the
auxiliary secondary medium circuits are supplied from the trip
medium circuit by way of orifices. The varying secondary medium
pressure in the follow-up pistons of the hydraulic amplifier in
turn effects changes in the positions of their associated control
valves or other control devices. Electro-hydraulic Control The
speed of the turbine is measured digitally. For this purpose
electrical speed transducers MYA01CS011 to 013 are mounted on the
high-pressure end of the turbine shaft. The electro-hydraulic
converter constitutes the link between the electrical and hydraulic
parts of the governing system. The electrohydraulic converter
consists of the speed control converter MAX45BY001 and a plunger
coil system CG001T. The signal from the electro-hydraulic
controller actuates the control sleeve via the plunger coil system.
The control sleeve determines the position of pilot valve KA07 in
the manner of a follow-up piston. The further mode of action is the
same as that of the hydraulic speed governor. Two differential
transmitters CG001A and CG001K are located at piston KA08 of
electro-hydraulic converter MAX45 BY001 as feedback transmitters to
the electro-hydraulic controller. This stabilizes the control
process. Change-over from Hydraulic to Electrohydraulic Control As
already mentioned, Change-over from one control system to the other
is possible even during operation as the two controllers are
connected in parallel downstream of the associated follow up piston
batteries, which form a minimum value gate. This means that
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5.1-0620-01/1
it is always the controller with the lower set point, which
leads. If the turbine is operated with the hydraulic governor, the
speed set point of the electrohydraulic controller is set at
maximum speed which prevents the electro-hydraulic control system
from coming into action. To bring in the electro-hydraulic control
system, the speed set point of the electrohydraulic controller must
be reduced slowly until the secondary medium pressures drop
slightly. When this occurs, the electrohydraulic controller has
taken over. Then the reference speed setter of hydraulic governor
speed MAX46BY001 is set to maximum speed. The electro-hydraulic
controller is then fully effective and can operate over the entire
load range. The hydraulic speed governor also acts as a speed
limiter in the event of failure of the electro-hydraulic
controller. In this case, operation of the turbine may immediately
be continued by means of the hydraulic speed governor. Change-over
from Electro-hydraulic to Hydraulic Control Change-over is
performed in the reverse sequence. First reduce the set point at
reference speed setter MAX46BY001 until the secondary medium
pressures drop slightly. This indicates that the hydraulic speed
governor has taken over. Then set the set point of the
electro-hydraulic controller to maximum. The hydraulic speed
governor is then completely effective and can operate over the
entire load range. Adjusting Device for Valves An adjusting device,
which makes it possible to change the setting response of the HP
and IP control valves, is provided for limiting the HP exhaust
steam temperature. In normal operation, control medium is admitted
to the space below the pistons of
regulating cylinders MAX45BY001 KA10 and MAX45BY011 KA10 by way
of energizing solenoid valve MAX42AA051, whereby the pistons move
into their upper end positions against the force of the spring and,
via a linkage, tension the springs of follow-up pistons KA02 of the
control valves in such a way that this produces the desired setting
response of the IP control valves in relation to the HP control
valves. If the condition Turbine load less than set minimum load
and the ratio of HP exhaust steam pressure to main steam pressure
greater than a set value is fulfilled, e.g. after a load rejection,
solenoid valve MAX42AA051 is de-energised, thereby cutting off the
flow of control medium to the regulating cylinders and allowing the
control medium under the pistons to drain off. The pistons are
moved into their lower end position by the restoring springs and
the springs of follow-up pistons KA02 are adjusted so that the IP
control valves do not begin to open until the HP control valves
have opened to a greater extent, with the result that the HP
exhaust steam temperature is lowered. For operation of the plant
without the HP and LP bypass stations, a manual adjusting mechanism
KA11 is also provided for adjusting the relationship between the
valves such that the reheat valves open before the main steam
valves. Under these operating conditions, solenoid valve MAX42AA051
is energised and an interlock is provided to prevent
de-energisation. This adjustment may only be performed manually and
must always be performed on both follow-up piston batteries
MAX45BY001 and MAX45BY011, to ensure that changeover from hydraulic
to electro-hydraulic control and vice versa is possible at all
times. This manual adjustment must always be reversed before the HP
or LP bypass station is brought into operation.
5.1-0620-01/2
Steam Turbine Description
Control System Electrical Speed Measuring
The electrical speed signals originate from the electrical speed
transducers which consist of four ferromagnetic type speed probes,
MAY01CS011 to 014 (one as spare) and a toothed wheel with 60 teeth
made around its circumference located on the main oil pump shaft.
The teeth of the wheel act upon the four stationary speed probes.
When turbine rotates, square wave signals are generated in the
probes. The frequency of these voltages is proportional to the
rotational speed of the turbine. The output of these speed probes
are fed to the input modules which provide digital output signals.
The three values for the rotational speed obtained by this process
are continuously monitored for failures. If one of the speed probes
fail, the control circuit continues to operate without
interruption, using two
remaining speed probes. The output is then fed to the speed
measuring unit, electrohydraulic controller and speed target unit.
The speed-measuring unit incorporates two speed ranges. The lower
range covers 0360 rpm and the upper range 0-3600 rpm. The
changeover from one range to the other is completely automatic. A
speed indicator mounted on the hydraulic control equipment rack
provides local speed-readings. Indicating lights located near the
speed indicator show which range is engaged. From the
speed-measuring unit, speed signals are also provided to the
turbine stress evaluator/controller, automatic turbine tester and
recorders. Output signals are available for purchasers remote speed
indicators and functional group automatic (FGA).
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5.1-0621-02
Steam Turbine DescriptionOverspeed Trip Two overspeed trips
MAY10 AA001 and 002 are provided to trip/shut down the turbine in
the event of overspeed. Each trip device consists of an eccentric
bolt/striker fitted in the emergency governor shaft with its center
of gravity displaced from the axis of rotation and held In position
against centrifugal force by a spring up to an adjustable preset
speed of 10 to 12 % above the normal turbine operating speed. At
the preset overspeed, centrifugal force overcomes the spring force
and the eccentric bolt/striker flies outwards into its extended
position. In doing so it strikes the pawl which releases the piston
of the overspeed trip release device KA01. Through combined spring
force and fluid pressure, the piston opens the auxiliary trip fluid
circuit to the main trip valves MAX51 AA005 and MAX51AA006.
Thrust-Bearing Trip Thrust bearing trips MAD12CY011/012/013 are
tripped electrically in the event of excessive axial displacement
of the turbine shaft. Pressure Switch Installed in the trip fluid
circuit are two pressure switches MAX51CP011 and MAX51CP012 which
bridge the longtime delayed relays of the reverse-power protection
system in such a way that the generator is shut down by response of
the short-time delayed relays as soon as it begins to motor. The
annunciation Turbine trip initiated is transmitted simultaneously
to the control room. Remote Solenoid Trip Remote solenoid trip is
activated via solenoid valves MAX52 AA001 and MAX52 AA002. The
remote solenoid trip may be initiated manually from the control
room by push button, by the electrical low-vacuum trip or the
thrust bearing trip or other protective devices.
Protective Devices
Low-Vacuum Trip for Turbine Protection An increase of pressure
in the condenser causes the valve of low-vacuum trip MAG01 AA011 to
move downwards from its upper position under the force of the
pre-tensioned spring. This action depressurizes the space below the
right-hand valve. The right-hand valve is moved into its lower
position by a spring and thus opens the auxiliary trip fluid
circuit. Opening the auxiliary trip fluid circuit depressurizes the
fluid below the differential pistons of main trip valves MAX51AA005
and MAX51AA006 and the differential pistons are activated by a
spring. This closes the control fluid inlet to the trip fluid
circuit and at the same time opens the main trip fluid circuit to
drain, causing the trip fluid pressure to drop and all stop and
control valves of the turbine to close. Limit switch MAG01CG011B
signals to the control room that the low-vacuum trip is not in its
normal operational position. Limit switch MAG01 CG011C indicates in
the control room that turbine trip has been initiated by the
lowvacuum trip. To make it possible to latch-in the trip devices
and thus to build up trip fluid pressure for adjusting and testing
the control loop or similar purposes when the turbine is shut down
and no vacuum exists, the lowvacuum trip has an auxiliary piston
which is loaded with primary oil pressure above the adjustable
compression spring. When the turbine is shut down there is no
primary oil pressure and so the auxiliary piston is unable to
tension the adjustable compression spring arranged above the
diaphragm system. The spring below the diaphragm system lifts the
valve, closing the auxiliary trip fluid circuit so that the trip
devices can be latched in. As soon as the turbine is started up and
brought up to speed, primary oil enters the space above the
auxiliary piston, forcing in into its lower end position at a
turbine speed far below rated speed. Thus the low-vacuum trip is
reset for initiation of turbine trip before the turbine has reached
rated speed.
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Solenoid Valves for Load Shedding Relay Solenoid valves MAX45
AA001 and MAX46 AA011 are provided to prevent the turbine from
reaching trip-out speed in the event of a sudden load rejection.
These solenoid valves are actuated by the load shedding relay if
the rate of load drop relative to time exceeds a predetermined
value. Solenoid valve MAX45AA001 opens the IP secondary fluid
circuit directly. Solenoid valve MAX46 AA011 opens the auxiliary
secondary fluid circuit. Pilot valve KA07 of hydraulic converter
MAX45BY011 moves upward and allows the control fluid to flow to the
area below piston KA08 of the converter. Piston KA08 moves to its
upper end position, thereby depressurizing all secondary fluid
circuits. Since the reheat IP secondary fluid circuit opens
directly, the IP control valves (which control the major portion of
the power output) close without any appreciable delay. A small
delay is involved in closing all other control valves by
depressurizing the auxiliary secondary fluid circuit, but his
action is still performed before an increase in turbine speed
causes the speed controller to respond. At the same time, the
extraction check valves, which are dependent on secondary fluid via
extraction valve relay MAX51AA011, close. After an adjustable
interval, the solenoid valves are reclosed, permitting secondary
fluid pressures corresponding to the reduced load to build up
again. Turbine Trip Gear The trip fluid is taken from the control
fluid
via main trip valve MAX51AA005 and MAX51AA006 and flows both to
the secondary fluid circuits and to the stop valves MAA10+20AA001
and MAB10+20AA001. The main trip valves serve to rapidly reduce the
fluid pressure in the trip fluid circuit. If the pressure below the
differential piston of main trip valves MAX51 AA005 and MAX51AA006
drops below a preset adjustable value, the piston in each valve is
forced downwards by the spring, opening the drain passage for the
trip fluid and closing the control fluid inlet. If the pressure in
the trip fluid circuit drops below a predetermined value, spring
loading separates the upper and lower pistons of main stop valves
MAA10+20 AA001 and reheat stop valves MAB10+20 AA001, and all the
stop valves close very rapidly. At the same time, the control
valves and extraction check valves also close, as the secondary
fluid circuits are fed from the trip fluid circuit. Thus on trip
initiation, all turbine stop and control valves close. Manual local
Trip Method of Initiating Turbine Trip Manual local initiation of
turbine trip is performed by way of local trip valve MAX52 AA005.
The valve must be pressed downwards manually, thus opening the
drain passage for the auxiliary trip fluid. The two limit switches
MAX52CG005C and MAX52 CG005E indicate in the control room that trip
has been initiated locally by hand.
5.1-0630-01/2
Steam Turbine Description
Overspeed Trip Test
Testing with Turbine under Load Condition Overspeed trips MAY10
AA001 and 002 can be tested using test device MAX62AA001 with the
turbine running under load or noload conditions. To operate the
test device, pilot valve KA03 is first pushed downwards and held in
this position. This isolates the auxiliary trip medium circuit from
the overspeed trips and prevents the main trip being initiated by
the overspeed trips. Subsequent operation of hand-wheel KA01 moves
the center pilot valve downwards. This action blocks the drain and
allows the control oil to flow through the center bore of the pump
shaft into overspeed trips. The control oil pressure thus builds up
and moves the eccentric bolts/strikers outwards against the spring
force, releasing the pawls of the overspeed trip releasing device,
as a results of which the pilot valve moves rapidly inwards. The
pressure in the auxiliary rip medium circuit, up to the over speed
trip test device, then collapses. Operation is followed by
observing the reading at pressure gauge MAX52CP501. The trip
pressure is read off at pressure gauge MAX62CP501. If during
operation at rated speed, this pressure should deviate from the
baseline value as recorded in the test report, a defect in the
overspeed trip may be assumed. If the trip pressure is too high,
the bolt may be made to move freely by rapidly operating the pilot
valve by means of hand-wheel KA01 several times in succession. If
this measure does not have the desired result, the turbine must be
shut down and the emergency governor to be inspected. As soon as
the auxiliary trip medium pressure drops to 0 at pressure gauge
MAX52CP501, the center pilot valve must be returned to its original
position using hand-wheel KA01. The pressure in the test line
should then return to 0, as can be read off at pressure gauge
MAX62CP501. The bolts/strikers of the overspeed trips should return
to their original position.
When this happened, pilot valve KA02 must be pushed downwards to
admit control medium into the auxiliary start-up medium circuit to
the differential pilot valve of the overspeed trip device. The
pilot valve moves towards the right and latches the overspeed trip
device in again. The buildup of pressure in the auxiliary startup
medium circuit between the overseed trip test device and the
overspeed trip release device can be followed at pressure gauge
MAX48CP501. When pilot valve KA02 is then released, the auxiliary
start-up medium pressure returns to 0 pressure. The auxiliary trip
medium pressure must then remain at its full value (readable at
pressure gauge MAX52CP501). If this is the case, pilot valve KA03
may be released. The test is completed. If, when valve KA02 is
released, the auxiliary trip medium pressure collapses, pilot valve
KA02 must be pushed downwards again and must be held in this
position a little longer. It is essential that the auxiliary trip
medium pressure must remain steady before valve KA03 is released.
Testing with Turbine under No-Load Condition Overspeed trips
MAY10AA001 and 002 must be tested at regular intervals by running
the unloaded turbine up to trip speed. This is done by operating
lever KA07 of hydraulic speed governor MAX46BY001, which presses
linkage KA03 downwards, thus increasing the secondary medium
pressures. This causes the control valves to open and the turbine
starts to overspeed. The actual speed at which trip occurs can be
read off at pressure gauge MAX44CP501. Limit switches
MAY10CG001&002C of overspeed trip release device MAY10 AA001
and 002 indicate in