] ] 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

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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.

BHEL Haridwar

5.1-0330-01/1

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.

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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.

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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

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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.

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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

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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.

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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

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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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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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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.

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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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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.

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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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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.

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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