Gas Turbine and Auxiliaries Alstom

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Berrouaguia 3 x GT13E2 GS 2003-216

For Information Only Part II Gas Turbine and Auxiliaries

6.1. Gas Turbine and Auxiliaries 6.1. Gas Turbine and Auxiliaries

1

6.1.1. Gas Turbine Block

2

6.1.2. Compressor Variable Inlet Guide Vanes

9

6.1.3. Combustor

11

6.1.4. Gas Fuel System

17

6.1.5. Fuel Oil System

19

6.1.6. Dual Fuel Capability

21

6.1.7. Ignition Fuel System

23

6.1.8. Water Injection System

25

6.1.9. Hydraulic/Pneumatic Control System

27

6.1.10. Lube and Power Oil System

31

6.1.11. Cooling and Sealing Air System

35

6.1.12. Compressor Blow-off System

38

6.1.13. Compressor Cleaning "Off-Line"

41

6.1.14. “On-Line” Wet Cleaning of the Compressor

43

6.1.15. Drainage of Compressor and Combustor

44

6.1.16. Air Intake System, Pulse Filter

46

6.1.17. Anti-Icing

49

6.1.18. Generator And Lube Oil Cooling System: Air Cooled

51

6.1.19. Exhaust System, Simple Cycle Power Plants With Vertical Silencer

53

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6.1.1. Gas Turbine Block

Figure 6.1-1 Gas turbine block during assembly (turbine casing not yet installed)

Figure 6.1-2

View of the gas turbine block with exhaust diffusor and foundation



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Figure 6.1-3


Cross-section lengthwise through the gas turbine block

Legend 1 2 3

Rotor Exhaust end journal bearing Compressor end journal bearing

9 10 11

turbine housing Annular combustor Compressor inlet


16 17 18

Turbine vane carrier Turbine vanes Exhaust housing


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Thrust bearing Turbine blades Turbine blades Compressor housing Compressor / combustor housing

12 13 14 15


Compressor inlet guide vanes (variable) Compressor vane carrier Compressor vanes Compressor diffusor

19 20 21 22

Blow-off valve Blow-off hood Turbine-end support Compressor-end support

Main Features ● ● ● ● ● ●

Compact design: The turbine, the compressor, and the combustor together with the burners are supplied as fully assembled units. Thermal and acoustic insulation of the thermal block A single shaft shared by the turbine and the compressor, made up of several forgings welded together Simple suspension in two journal bearings and one thrust bearing, none of which is located in the hot zone Cast outer casing of the turbine and the compressor is split at the level of the axis, providing full access to both parts of the machine. The following can be done without requiring opening of the turbine: ○ inspection, repair, and replacement of the bearings ○ inspection and replacement of individual burners ○ endoscope inspection of compressor blading ○ inspection of the first stage in the compressor and the last stage in the turbine ○ inspection of the inner combustor and the first turbine stage through manhole in the turbine casing

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An effective cooling system for all parts in the hot gas path (vanes, blades, vane carrier, shaft) ensures that temperatures will remain within permissible limits and makes elevated process temperatures possible Internal air-cooling of the first two rows of turbine vanes and the first three rows of turbine blades

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The turbine casing can be opened separately if required

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Simple and effective convection cooling of the rotor and the vane carrier using air from the discharge end of the compressor Single annular combustor design, at present the largest of its type Uniform temperature distribution before the turbine resulting from the annular combustor

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72 EV burners, arranged off-set in pairs

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The single annular combustor and the arrangement of the burners produce a very thorough mixing in the hot gas. This means: ○ a uniform temperature distribution in the hot gas ○ full combustion

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Short flames, resulting from the EV burners Further developed 2nd generation of the "lean premix" technology with which the best emission levels so far anywhere in the world have been attained Simple, compact burner design

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Good flame stability

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No flashback problems

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Combustor suitable for

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liquid fuels natural gas

Electronic flame monitoring

Description The gas turbine block consists of the turbine and the compressor. The annular combustor is installed between these units. The main parts are (Figure 6.1-3): ● The rotor (1), with the turbine blades (5) and the compressor blades (6), supported and guided in two journal bearings (2, 3) and one thrust bearing (4)

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The compressor casing and the turbine casing (7-9) which also surrounds the annular combustor (10) The variable compressor inlet guide vanes (12)

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The compressor inlet (11)

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The compressor vanes (14), installed in the compressor casing and the compressor vane carrier (13) The compressor diffuser (15)

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The turbine vane carrier (16) and turbine vanes (17)

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The exhaust casing (18)

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The blow-off system, with the blow-off valves of the first two stages (19) installed under the blowoff hood (20) (the valve for the third stage is mounted at the side and blows off into the exhaust duct) The supports on the turbine end (21) and the compressor end (22).

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Rotor and Blades

Figure 6.1-4

Rotor

The rotor, welded together from several forgings, holds the blades of the turbine (5 stages) and the compressor (21 stages). The turbine blades are fixed in position radially in "pine-tree" slots and are also secured axially. In the front stages, some of them - depending on the materials used - are coated (Refer also to the sub-section, "Vanes"). The compressor blades are mounted together with spacers in circumferential T-slots. The blades in the first five stages of the compressor are coated to protect them against corrosion and erosion. In the turbine zone, the shaft is covered with heat shield segments to protect it against the severe thermal stressing from the hot gas. Air taken from the discharge end of the compressor provides additional cooling for these segments. This air is also used to cool the first three rows of turbine



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blades (refer to the Chapter, Section "Cooling and Sealing Air Systems," for details). These actions make it possible to attain a higher process temperature, thereby increasing the power output and improving the efficiency of the unit.

Bearings The rotor turns in two journal bearings (2, 3) mounted in their own casings, one at the compressor inlet (11) and the other in the exhaust casing (18). The axial position of the entire rotor train (including the generator) is defined by a friction thrust bearing (4) that is also located in the compressor inlet. The support and slide surfaces are made of babbitt metal. All bearings are lubricated and cooled with pressurized oil supplied from a special system (refer to the Chapter Lube and Power Oil System). The temperatures of the bearing metals and the returning oil are monitored by built-in thermocouples. Maintenance can be carried out on all friction bearings without requiring the opening of the turbine or the compressor casings.

Gas Turbine and Compressor Casing The gas turbine casing comprises the actual turbine casing (9) and the exhaust casing (18) attached to it. The first of these is made of heat-resistant material that can withstand the thermal stresses that occur during operation. The turbine casing encloses the turbine and the combustor (10) located upstream from it. It is used for the suspension of the turbine vane carrier (16) and the combustor. The casing is surrounded by the compressed air from the compressor, which cools the parts lying inside the casing before it is sent to the burners. The ring-shaped exhaust casing is made of heat-resistant ferritic material and is designed so that it can withstand the thermal stressing. The exhaust-end rotor bearing casing is attached at the middle of the casing. The bearing forces are transmitted across support struts between the bearing casing and the exhaust casing. The compressor casing is made of three sections of high-quality cast material. The compressor inlet casing (11) provides the link between the air intake system and the compressor. It contains, at its middle, the bearing casing with the compressor-end journal bearing (3) and the thrust bearing (4). The attachment is the same as that on the exhaust end. In addition, the inlet casing accommodates the compressor inlet guide vanes (11), which are variable. The compressor inlet casing also provides the central support on the foundation. The actual compressor casing (7) is split vertically after the eighth stage in the compressor. The front section (Stages 1 to 8) is surrounded by two blow-off chambers. The blow-off valves (19) for these have been placed at the top under a hood (20). The third blow-off stage is located in the back section of the compressor casing (Stages 9 to 21). The outlet from this stage leads to the exhaust duct. Together with the turbine casing, the back section of the compressor casing forms the shell around the annular combustor. In addition, the burners and the ring-shaped fuel supply lines (not shown in Fig. 2-1) are fastened to the back section of the compressor casing. The internal parts built into both compressor casings form the vane carrier.



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Compressor and Turbine Vanes In the compressor, the casing also serves as the vane carrier. The vanes are mounted in circumferential grooves and fixed in place with spacers. All compressor vanes are made of heatresistant chromium steels. The first five rows of vanes are coated to protect them against erosion and corrosion. The turbine vane carrier is, like the shaft in this zone, covered with heat shield segments to protect it against the effects of the very high temperatures resulting from the hot gas. In addition, the vane carrier has intensive counter-flow cooling using air taken from the end of the compressor. Following this use, the air then flows to the second row turbine vanes to cool them from the inside. The vanes of the first stage are supplied directly with air taken from the end of the compressor. Some of the vanes of the front stage in the turbine -depending on the materials used- are also coated to protect them against oxidation and corrosion.

Cooling and Sealing Air System Compressed air is withdrawn from the compressor and directed to the parts in the hot gas path in the turbine zone to cool those zones and to block the penetration of hot gas and oil vapor into zones where they are not permitted (refer also to Section, "Cooling and Sealing Air System").

Safety and Monitoring Equipment The bearing metal temperatures of the journal bearings and of the thrust bearing are monitored by built-in thermocouples. If a temperature exceeds the prescribed maximum value a load shedding (refer also to chapter, part "turbine protection") and an alarm are initiated. The bearing pedestals are equipped with measurement devices for bearing pedestal vibrations which initiate a trip in case of an exceeding of the prescribed values. The relative shaft vibrations are measured at every journal bearing and are indicated in the control room. The exhaust gas temperature is multiple measured in the exhaust gas diffuser. It is used together with the pressure at the compressor end to calculate the turbine inlet temperature. Values higher then prescribed cause a load shedding of the gas turboset. Electronic overspeed detectors monitor the rotational speed of the rotor and initiate a trip and alarm if the maximum speed is exceeded.



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6.1.2. Compressor Variable Inlet Guide Vanes

Figure 6.1-5

Compressor Variable Inlet Guide Vane Row

Legend 1 2 3 4

Compressor Variable inlet guide vane row Linear drive Measurement of vane angle

5 6 7 8

Measurement of linear drive setting Control valve for linear drive Measurement of control valve setting Pilot valve

9 A B

Filter Power oil supply Power oil return

Main Features ●

Increases overall efficiency of combined-cycle plants in the gas turboset's part-load range

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Automatic adjustment of the inlet guide vanes while the gas turbine is in operation via a control circuit (control parameters = optimum part-load efficiency of the combined-cycle unit and limit imposed by the maximum permissible temperature of the exhaust gas) Adjustment of the vanes in the guide vanes via an adjustment ring with a rotating suspension; the ring itself is driven by a hydraulic linear drive

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Optimum adjustment of emission levels of noxious components in the part-load range

Description of the System The guide vanes are actuated by adjustment ring and tie rod. This adjustment ring, which runs around the circumference of the compressor casing inlet, is also mounted to rotate. It is moved by the linear drive (3). The linear drive itself is supplied from the power oil system (A). The control valve (6) controls the position of the piston, which is monitored by the measurement of position (7). The inlet guide vane row is closed (at the mechanical stop) while the turboset is at standstill. When the gas turbine is started up, the inlet guide vane row is opened to the predefined starting position. As soon as the turbine inlet temperature for full load is attained, or as soon as the exhaust gas temperature reaches the maximally permissible level -- one or the other -- the inlet guide vane starts to open to its normal position. The control parameter is either the constancy of the turbine inlet temperature or the maximum turbine discharge temperature permissible. During operation at full load, the inlet guide vanes are in their normal position. During a normal shut-down or deloading of the gas turboset, the inlet guide vanes are directed in the direction contrary to the one followed during start-up or loading. The exact procedure depends on the situation in which the shut-down or the deloading was initiated.

Safety and Monitoring Equipment The angular setting of the inlet guide row vanes and the setting of the linear drive (3) are monitored. If the blade angle of the inlet guide vanes drops below a preset limit while in operation, an alarm is set off. If the vanes close even further, an emergency trip follows. The "Open" and "Closed" settings of the control valve (6) are likewise monitored. If the power oil pressure at the inlet to the control valve is too low (e.g., during a trip), the control valve is deenergised by a pressure measurement installed upstream from the valve, and shifts into a safe setting. This locks the inlet guide vanes in their position at that moment. The filter (9) upstream from the control valve (8) separates out coarse particles. The sieve is monitored by a measurement of differential pressure and an alarm is set off in the control room whenever the differential pressure exceeds the permissible limits.



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6.1.3. Combustor

Figure 6.1-6

Annular Combustor



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Figure 6.1-7


Cross-section lengthwise through the annular combustor

Legend 1 2 3 4 5

Front segment EV burner Heat shield Support structure High temperature jacketing

6 7 8 9

Combustor housing (secondary section) Combustor housing (primary section) Cover plate Combustor suspension (in the parting plane


10 A B

Vane of the first turbine stage Air from the discharge end of the compressor Hot gas


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Figure 6.1-8


Cross-section through annular combustor (burner layout)

Description The main parts of the combustor are: ● Front segment and the support structure ●

Heat shield segment and the support structure

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EV burners

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Transition piece to the turbine Flame monitors

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Igniter

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Annular casing

The combustor is placed in a ring within the turbine casing, between the compressor and the turbine (refer to Figure 6.1-8). It consists of a primary zone, in which the actual combustion takes place, and a secondary zone, which sends the hot gas on to the turbine with very slight losses (Figure 6.1-10). The primary zone is formed by the front segments (1) with the EV burners (2) inserted into them and the heat shield segments (3) attached above and below them. These parts are fixed in position by a support structure (4), which, in turn, provides the connection to the turbine casing. The secondary zone is formed of high-temperature resistant plates.



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A casing (6,7) completely encloses the combustor in order to direct cooling air withdrawn from the end of the compressor past the outside of the combustor in counter-flow cooling. In the primary zone, it also accommodates the EV burners. After the compressor air (A) flows through the compressor diffuser, it is deflected by turning vanes into the surrounding chamber of the turbine casing. In so doing, it not only provides counter-flow cooling for the combustor, but also cools the turbine vane carrier. The cover plate on the burner end of the combustor (8) has holes through which the air from the end of the compressor can reach the EV burners. Figure 6.1-8 shows how these burners are arranged in the combustor. Neighboring pairs are in each case slightly offset in their radius, producing effectively four rows of burners. The burners are mounted on the casing. They are supplied with fuel through ring-shaped lines attached on the outside. Later Sections explain how the systems involved function. The annular arrangement of the combustor makes possible a uniform and low-loss flow to the turbine because the hot gas path can be kept quite short. In addition, the thorough mixing results in an even temperature profile and a complete combustion. During part-load operation, only every 4th burner is switched off so that the advantageous temperature profile can be maintained even at low loads. Two electrically activated ignition torches supplied from a gas system of their own are installed for ignition of the burner flames. The flame then spreads from burner to burner without requiring further intervention as soon as those burners are supplied with fuel. The combustion process is monitored by three flame monitors, which are evaluated in 2 of 3-circuit. The surrounding turbine casing is split horizontally in order to provide easy access to the combustor for purposes of maintenance. For a fast access, a manhole is attached.



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EV Burners

Figure 6.1-9

EV Burner

The EV Burner (Figure 6.1-9) is a premixing burner of a simple design based on our long years of experience in developing and operating low NOx premixing burners and on investigations conducted in our research center of the scientific principles involved in the behavior of strongly swirled flows. The EV burner consists of a hollow cone (3) split axially, with its halves displaced cross-wise from one another (refer to the Cross-Section in Figure 6.1-10). The combustion air flows into the combustion zone through the slots that result. The fuel gas flows through two gas channels (4), enters into the burner through a row of holes (1) at the outlet of the burner, and mixes there with the air. The burner geometry has been optimized so as to produce a strongly swirled flow with a back-flow zone freely stabilized within the combustion zone. Only in this zone are the flow velocities slow enough to make possible the ignition of the fuel/air mixture, which has, in the meanwhile, become fully homogeneous. The flow described and the lean mixture of the air and fuel produce low flame temperatures, and these result in the low emission levels attained. If oil operation is offered during fuel oil operation, the liquid fuel is sprayed in through an atomizer nozzle (2) integrated into the burner head. Additional water is mixed into the oil in order to meet prescribed emission levels.



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Figure 6.1-10 EV burner Legend 1 2 3

Opening for the gas outlet Liquid fuel for atomization nozzle (only for oil burning machines) Split cone

4 A B

Gas channel Gas Liquid fuel (only oil burning machines)


C D

Combustion air Mixed gas and air in operation on gas, air in operation on oil


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6.1.4. Gas Fuel System

Figure 6.1-11 Fuel gas system

Main Features ● ● ● ●

Both the main gas shut-off valve and the gas relief valve are equipped with both motor and manual drives. The trip valve and the gas-tight control valves are equipped with servomotors Control system as part of the control valve block is fully assembled, cabled, and tested in the workshop Separate valves for controlling the gas flow and for trip

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Valves equipped with metal seals System depressurized when the gas turboset is at standstill

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EV Burners supplied with gas via a system of ring and stub-line pipes outside the combustor

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Monitoring of all critical parts of the system by the fire and explosion protection system.

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Description of the System Principle of Operation The fuel gas flows into the fuel system through the gas supply unit and the fuel supply line. The main gas shut-off ball valve divides the gas supply system from the fuel system. For ignition, the main gas shut-off ball valve and the trip valve open and the gas relief valves closes. During ignition not all burners are in operation. The control valve defines the amount of fuel for ignition, and that fuel is lit by two ignition torches in the combustor. Because the mixing conditions within the premixing zone of the burners during a run-up of the turbine do not guarantee the certainty of proper ignition, the ignition process is supported by directing an additional flow of gas ("piloting") via one of the three lines into the tip of the EV Burners. Once ignition has been accomplished, the control valves continue to open at first, as called for in the starting program and then, after synchronization, according to the power output called for. Once stable combustion conditions have been attained, the supply of gas to the tips of the burners switches off. The remaining burners are set in operation at high part load and work in gliding FAR (Fuel to Air Ratio) mode up to approx. 70% load. Above this load level the turbine is run with all burners at the nominal FAR. During a shut-down of the gas turboset, the control valves close first, followed by the trip valve and finally the main gas shut-off valve. The gas relief valves open the connection to the outside air and deload the system to ambient pressure. In an emergency trip of the gas turboset, the control valves and the trip valve close immediately.

Safety and Monitoring Equipment Limit switches monitor the "Open" and "Closed" settings of the main fuel gas shut-off valve, the gas relief valves and, the valve for ignition with fuel gas, and the "Closed" setting of the control valves and the trip valve. An alarm is set off in the control room whenever the main gas shut-off valve fails to close completely. If there is not sufficient pressure present at a start-up of the gas turboset, the pressure measurement built in upstream from the main gas shut-off valve prevents further progress of the starting program. During operation, it sets off an alarm in the control room under these conditions. The pressure measurement built in downstream from the trip valve initiates an emergency trip if the pressure drops below the preset minimum level. Because the control valves are gas-tight, no exhaust fan is needed in the gas control block. The non-return valves before the burners prevent the entering of hot gas into the fuel gas system. The fire and explosion protection system monitors all endangered parts of the gas fuel system.



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6.1.5. Fuel Oil System

Figure 6.1-12 Fuel oil system (Fuel Oil Block is part of the Combined Fuel Oil / NOx Water Block)

Main Features ● ●

Trip valve, the three control valves and the drainage valve have hydraulic drives The three drainage valves are activated pneumatically

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The trip valve and the control, pilot, and blow-out valves have been incorporated into the control valve block The pump, filter, and meter are mounted on the fuel oil block. This block is supplied completely preassembled, including piping and cables, and tested The Combined Fuel Oil / NOx Water Block is located outdoors and suitable for any climate

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The EV burners are supplied with fuel oil group-by-group via three supply lines

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Monitoring of all critical parts of the system by the fire and explosion protection system.

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Description of the System Principle of Operation The fuel oil supply system supplies the fuel to the fuel forwarding system. The fuel flows through the main shut-off valve -which is equipped with both a motor and a manual drive - to reach the filter. The filter is of a twin design so that the half that is not in operation can be cleaned without having to stop operation of the gas turboset. The pressure limiting valve installed upstream from the filter protects the system against overpressure. The metering of through flow is built in downstream from the fuel oil pump. This is needed, among other things, for directing the water injection for reduction of NOx emissions. The fuel oil pump forwards the fuel to the EV Burners and produces the pressure required for atomization. If there is not sufficient pressure present at start-up, the gas turboset cannot be started; during operation, the turboset is automatically tripped. For ignition, the drainage valves close; the trip valve opens, and the fuel oil pump starts, so that fuel can flow to the control valves. To prevent an overheating of the fuel oil pump in operation, a certain minimum amount of fuel must flow through the pump to cool it. For that reason, during a start-up of the gas turboset, a volume flow is pumped back into the tank through the fuel return line (Valve is open to the return line) until nominal speed has been attained. Inside the combustor, the liquid fuel is ignited by the two ignition torches installed there. Then the control valves open further, at first as called for in the starting program and - after synchronization according to the power output required. At the same time, the valve in the fuel return closes. The EV Burners are supplied with fuel via three supply lines. The three control valves direct the flow that passes through each of these lines. During an emergency trip of the gas turboset, the control valves and the trip valve close immediately. The leakage from the valve sealing cases and from the filter flows through the leakage fuel return to the cyclone extractor and then into the tank. The leakage tank pump forwards the leakage fuel back into the main tank. After switch off a group of burners the parallel working NOx water system is operated for a few more seconds to flush the oil lances and thereby to prevent them from coking. The procedure is possible because oil and water are mixed inside the lance and enter the combustor through the same nozzle.

Safety and Monitoring Equipment ● ● ●

Limit switches monitor the "Open" and "Closed" setting of the leakage valves. Limit switches monitor the "Closed" setting of the trip valve. If the trip valve fails to close completely, an alarm is also set off in the control room. Limit switches monitor the "Closed" setting of the main shut-off valve. An alarm is set off in the control room if this valve fails to close fully.



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The pressure limiting valves and protect the system from over-pressure due to thermal expansion while at standstill.

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The measurement of differential pressure across the filter sets off an alarm in the control room is the difference in pressure exceeds the permissible limit (excessive fouling). The measurement of pressure before the fuel oil pump prevents a start-up of the gas turboset if there is not sufficient pressure present. The measurement of pressure after the fuel oil pump initiates an emergency trip if there is not sufficient pressure present. If the temperature drops below the minimum level acceptable (the viscosity of the fuel becomes too high), the measurement of temperature after the fuel oil pump sets off an alarm in the control room. If the fuel in the tank rises above the maximum level permissible, an alarm is set off. Then, if the fuel level continues to rise, the second measurement of level built in initiates an emergency trip of the gas turboset The fire and explosion protection system monitors all endangered parts of the liquid fuel system.

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6.1.6. Dual Fuel Capability Main Features ●

Increases the availability of the gas turboset

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Automatic switch-over from fuel gas to fuel oil without interruption in operation if the gas supply should fail Manual initiation of the switch-over from fuel oil to fuel gas

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Description Operation on Gas The section, "Fuel Gas System," includes the procedures for operation, supply, and control on gas.

Operation on Fuel Oil The section, "Fuel Oil System," includes the procedures for operation, supply, and control on distillate.

Emergency Switch-Over from Fuel Gas to Fuel Oil The fuel gas pressure in front of the main shut-off valve is monitored. The preset minimum level sets off an alarm, and a fully automatic fuel switchover is initiated at the same time. Should the gas turbine load before switch-over be between 35% and 70% load, the gas turbine is deloaded to 35% load. When this load is reached, the switchover procedure commences. This is accomplished by activating the fuel oil supply system and opening the main fuel oil shut-off valve. As soon as the prescribed pressure before the fuel oil pump has been attained, the fuel oil pump starts up and builds up oil pressure. Once this pressure has attained its prescribed level, the



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switch-over program proceeds. The oil trip valve and control valves open, enabling the fuel oil to flow to the EV Burners and support the combustion. Simultaneously with the opening of the control valve for fuel oil, the fuel gas supply is throttled down by the corresponding gas control valves. The process has been completed when only fuel oil is flowing into the combustor, when the supply of gas has been broken off completely, and when the fuel gas system has been depressurized. Should the gas turbine load prior to switchover have been in the range of 35% to 70% load, the fuel oil flow is increased until the load prior to initiation of switch-over is reached.

Switch-Over from Fuel Oil to Fuel Gas The procedure must be initiated manually. Thereafter, it also proceeds fully automatically, with all steps taking place in the reverse order, i.e., the gas system is activated and the oil supply is cut back once the gas supply responds. Note: This design is based on the assumption that gas is normally burned as the main fuel and the oil serves as a standby fuel. For that reason, a fully automatic switch-over from gas to oil is sufficient for normal operation.

Safety and Monitoring Equipment If the gas pressure downstream from the trip valve drops below the minimum level required during the switch-over process before operation on fuel oil has been enabled, the pressure measurement initiates an emergency trip of the gas turboset.



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6.1.7. Ignition Fuel System

Figure 6.1-13 Ignition fuel system Legend 1 2 3 4 5 6 7 8 9 10

EV burners Ignition torches Switch-over and reducing valve Shut-off and relief valve Shut-off valve Relief valve Shut-off valve Shut-off valve Ignition gas system (propane) Non-return valve

11 12 13 14 15 16 17 18 19

Orifice Non-return valve Orifice Combustion air supply Non-return valve Orifice Non-return valve Orifice Gas cylinder

20 21 22 23 24 25 A B

Gas cylinder Filter Gas orifice Gas exhaust fan Feed orifice for incoming air Ignition fuel module (part of the control valve block) External air not used


Standard system separate from the main fuel system Supplied from commercially available propane cylinders



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Automatic switch-over to the standby cylinder during normal operation

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Ignition fuel block completely prefabricated, with cables, and tested

Description of the System Ignition with Propane Gas Once ignition speed has been attained, the functional group "Combustor" switches on. The flow of ignition gas to the burner is enabled by the shut-off valves and the relief valve. The spark plugs built into the ignition torches are energized, start to glow, and light the ignition gas. The main fuel flows out of the EV burners into the combustor and is, in turn, ignited by the ignition flame. When ignition has taken place, the current to the spark plug is interrupted and the valves return to their "at rest" position. The arrangement of the valves selected is such that the ignition gas line is not pressurized in the "at rest" position. A main propane cylinder can be selected manually. The switch-over to the standby cylinder is done automatically. If one of the two propane cylinders is empty, the switch-over valve has to be used to switch over manually to the standby cylinder. The empty cylinder can then be taken out and replaced. The ignition fuel module accommodates the entire ignition fuel supply system. The fan provides forced ventilation of this module to draw off any gas leakage and thus keep the risk of fire and explosion as low as possible.

Safety and Monitoring Equipment Whenever pressure in the ignition gas line downstream from the filter drops below the preset minimum level, the pressure measurement sets off an alarm in the control room. The switch-over valve indicates the gas cylinder from which ignition gas is being drawn. Manometers display locally both the pressure in the cylinder that is in operation and the pressure in the ignition gas line.



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6.1.8. Water Injection System

Figure 6.1-14 Water Injection System (NOx-water block is part of the Combined Fuel Oil / NOx Water Block

Main Features ●

Reduction of NOx emission levels produced in the combustion process during operation of oil or dual fuel to within legally prescribed limits No negative impact on the combustion process

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Increased power output from the gas turboset due to the increased mass flow.

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Description of the System The water supply system supplies the injection system for NOx reduction with the required amount of water and generates the pressure necessary. NOx water injection pump circulates the water. The pump must have attained a preset minimum pressure level before the NOx reduction water is released for the combustion process. For this, the control valves are closed so that no water can flow to the EV-burners. A minimum flow valve installed downstream from the pump allows a certain amount of water to circulate for cooling purposes in order to prevent the pump from overheating.



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The water coming from the water supply system is directed to the EV-burners via the distributor pipes. The water is mixed with the fuel oil in the burner lance and is then sent to the combustion zone. The amount of water added, determined by the three control valves in the three supply lines, is directly proportional to the fuel flow. The water piping system design is like that of the fuel system. Three supply lines serve 1/6, 2/6, and 3/6 of the burners respectively. In the lower load range, two criteria are used to control the amount of water flow: ● The NOx regulations that pertain ●

The amount of smoke generated.

The stricter of the two criteria is decisive. In the upper load range, the flow of water is regulated so that the pertinent NOx regulations can be met. After switch off a group of burners the parallel working NOx water system is operated for a few more seconds to flush the oil lances and thereby to prevent them from coking. The procedure is possible because oil and water are mixed inside the lance and enter the combustor through the same nozzle.

Safety and Monitoring Equipment The positions of main shut-off valve, trip valve, and control valves are monitored. An alarm is set off whenever any of the following occurs: ●

Main shut-off valve, trip valve, or one of the control valves fails to close completely

● ●

The control valves are closed during operation on oil The trip valve fails to open completely

●

Water pressure downstream from the pump is insufficient.



)*+,



6.1.9. Hydraulic/Pneumatic Control System

Figure 6.1-15 Hydraulic/pneumatic control system Legend 1 2

Turbine Compressor

19 20

Fuel oil control valve Fuel oil control valve


40 41

Lube oil tank Main lube oil pump 1


)*+, 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18


Generator Annular combustor Measurement of exhaust temperature Turbine inlet temperature (calculated) Measurement of active power Measurement of speed Ring-shaped fuel pipes Compressor blow off valves Variable inlet guide vane adjustment Fuel oil system Main shut off valve Pressure limiting valve Fuel oil pump Minimum flow valve Fuel oil trip valve Fuel oil control valve

21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39


Pilot valve Quick action relief valve Control valve drive, with EHC Control valve drive, with EHC Control valve drive, with EHC Fuel gas system Relief valve Quick action relief valve Filter Fuel gas trip valve Relief valve Gas pilot valve Gas control valve Gas control valve Pilot valve Pilot valve Control valve drive, with EHC Control valve drive, with EHC Control valve drive, with EHC

42 43 44 45 46 47 48 49 50 51 52 53 54 A B C

Main lube oil pump 2 Hydraulic rotor barring device ontrol valve Power oil pump Safety system oil pump Main section of the hydraulic protection system Hydraulic / pneumatic safety trip for the blow-off systems Manual trip NOx water injection control valve NOx water injection control valve NOx water injection control valve Control valve drive, with EHC Control valve drive, with EHC Control valve drive, with EHC Fuel oil supply system Fuel gas supply system NOx water injection system

Main Features ● ● ●

Control systems make it possible to operate the gas turboset properly and at the best possible efficiency The hydraulic protection system protects the gas turboset, should the control systems fail The control system forms the link between the turbine controls and the machine.

Description of the System The control and protection system includes: ● Hydraulic/pneumatic control and protection systems ● Hydraulic fuel control systems ●

The hydraulic system for regulating NOx water injection

●

Hydraulic/pneumatic controls for the compressor blow-off valves

●

Electronic speed monitors.

The electronic turbine controls calculate the signals required by the control and protection systems for operation of the gas turboset.

Open-Loop Control Systems The open-loop control systems make it possible to start the gas turboset automatically, run it up and load it, and shut it down on one's own. They allow comprehensive monitoring of these processes.

Closed-Loop Control Systems The closed-loop control systems ensure that the process, which is subject to fluctuating external factors (generator utilization, air temperature, etc.), will maintain the preset setpoints. Their main components are the control valves for fuel gas (32 to 34), for fuel oil (18 to 20), and for NOx water injection (49 to 51), including their drives with electrohydraulic converters (37 to 39, 23 to 25, and 52 to 54).



)*+,



Protection Systems The protection systems protect the gas turboset from serious damage should the control systems fail. The protection system is directed by a central set of valves (46) connected to the fittings involved via power oil lines (45). (The NOx water injection system (C) has not been shown completely: it is structured like the fuel oil system and has likewise been integrated into the protection system.) The control and protection systems have been designed so that a collapse of pressure in the hydraulic/pneumatic piping system causes an immediate return to a safe setting of important system components supplied from that piping system (e.g., opening of the blow-off valves). This is in every instance checked by means of limit switches. The electrical components of the control and protection systems are deenergized while the gas turbine is in normal operation (open-circuit operation). The only exceptions to this rule are the "fire protection valves" (which have not, however, been shown on the schematic).

Fuel Control Basically, there are two modes of gas turboset control: ● Frequency/power control ● Temperature control (based on the calculated temperature of the hot gas at the inlet to the turbine). The fuel control and protection system has been designed for fuel oil and fuel gas (dual fuel) operation Fuel Control for Fuel Oil Three separate fuel lines, each with its own control valve (18 to 20) supply the EV Burners with fuel oil. The signals received from the electronic turbine controls are transduced into an oil pressure suitable for the valve drives in the electrohydraulic converter connected to the drives. The hydraulic drives (23 to 25) are equipped with springs that close the valves automatically when there is a dropoff in power oil pressure (which causes a trip). This cuts off the fuel supply. The NOx water injection system operating parallel to this system functions in the same way. The electronic turbine controls take over control of the valves involved (49 to 51). Obtain further information from the Section Fuel Oil System and the Section Water Injection System. Fuel Control for Fuel Gas The control for the gas supply to the EV Burners functions analogously to that for liquid fuels, but the system has been designed to the special requirements in controlling fuel gas. Obtain a more exact description for the Section, Fuel Gas System. Fuel Control in Dual Fuel Operation Basically, oil or gas is burned in the combustor, with gas usually being the main fuel and oil the standby fuel. During dual fuel operation or an emergency switch-over from one type of fuel to the other, the turbine controls activate both control systems (Refer also to the Section Dual Fuel).



)*+,



Protection Systems The protection systems have several functions to perform: ●

Providing alarms

●

Initiating protective load shedding Initiating trip.

●

The protection systems include: ●

Electrical and electronic monitoring and protection: exhaust gas temperature after the turbine (5), including calculation of the turbine inlet temperature (6) ○ electronic speed monitoring ○ an electrohydraulic trip unit in 2-of-3 circuitry (46). ○

●

Mechanical/hydraulic monitoring and protection: ○ the power oil system for initiating trips (45) ○ quick-action relief valves for the control pressure and the valve for the NOx water injection system which has not been shown) ○ the manual trip (48).

Note: The description is made for a dual fuel machine. For a single fuel machine only the appropriate part is applicable.



)*+,



6.1.10. Lube and Power Oil System

Figure 6.1-16 Lube and power oil system Legend 1 2 3 4 5

Turbine Compressor Generator Turbine journal bearing Compressor journal bearing

25 25 26 27 28

Lube oil supply orifice Lube oil supply orifice Lube oil supply orifice Lube oil supply orifice Lube oil drain sight glass


49 50 51 52 53

Jacking oil pump Jacking oil system Non-return valve Non-return valve Non-return valve


)*+, 6 7 8 9 10 11 12 13 14 15 16 17 18 20 21 22 23 24


Turbine rotor thrust bearing Generator drive-end bearing section Generator non-drive end bearing section Generator auxiliary bearing Lube oil pump 2 Lube oil pump 1 Shut-off valve Shut-off valve Pressure accumulator Orifice Temperature control valve Lube oil cooler Twin lube oil filter Lube oil distribution system Lube oil supply orifice Lube oil supply orifice Lube oil supply orifice Lube oil supply orifice

29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48


Lube oil drain sight glass Lube oil drain sight glass Lube oil drain sight glass Lube oil drain sight glass Lube oil return Power oil pump for rotor barring device Manual pump for rotor barring device Non-return valve Pressure limiting valve Control valve for rotor barring device Power oil system for rotor barring device Hydraulic rotor barring device Rotor barring device lifting cylinder Air intake filter Ventilation orifice Flame arrester Dearation flap valve Oil vapor fan Temperature control valve Jacking oil pump

54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 A B C

Non-return valve Non-return valve Non-return valve Emergency cooling oil pump Return flow orifice Non-return valvc Power oil pump Shut-off valve Non-return valve Pressure limiting valve Strainer Power oil system Auxilaries block lube oil heater Tank Drain cock Auxiliary block Cooling water inlet Cooling water outlet Power oil system

Main Features ● ● ● ● ●

Same oil used for lube oil, power oil, jacking oil, the hydraulic-pneumatic control and protection systems, and the hydraulic rotor barring device Two AC oil pumps (10 and 11), each with a 100% capacity, with an automatic switch-over if the oil pressure is too low DC power supply for the emergency cooling oil pump (57), the power oil pump (32) for the hydraulic rotor barring device, and the jacking oil pumps (48 and 49) Twin lube oil filter (18), with capability for switch-over during operation Temperature control valve (16) to ensure a uniform lube oil temperature at the inlet to the filter

●

A separate power oil system for the hydraulic rotor barring device (40), with a DC pump (34) and a manual pump (35) for emergencies A power oil system for the fuel control valves with built-in electro-hydraulic converters

●

Solenoid safety valves for releasing pressure in case of emergency

●

A very compact system with short piping paths, attained by central location of tanks, pumps, coolers, filters, etc.

●

Description of the System The lube and power oil system consists mainly of the: ● Lube oil supply ●

Power oil supply

●

Power oil supply for the hydraulic rotor barring device.

Lube Oil Supply The lube oil supply: ● Supplies lube oil to the gas turboset bearings ● ●

Cools the exhaust-end bearing Supplies the jacking oil system



)*+,



●

Supplies the hydraulic-pneumatic control and protection systems

●

Supplies the hydraulic rotor barring device.

Supplying of Lube Oil to the Bearings The lube oil is stored in a tank (67) that also forms the base plate for the auxiliaries block. During prolonged periods at standstill, the built-in heater (66) maintains the lube oil at the minimum temperature required for operation. During operation, one of the two lube oil pumps (10) or (11) supplies the gas turboset with the lube oil required. Should the pump that is in operation fail, an automatic switch-over to the other pump takes place. The pressure accumulator (14) takes over the supplying of oil while the replacement pump is running up. The lube oil is forwarded to the temperature control valve (16), from which it flows -- depending on the temperature -- either all through lube oil cooler (17), or some through the cooler and some through the bypass, or all through the by-pass. This keeps the lube oil temperature within the preset range. The cooling system is described in more detail in the section "Generator and Lube Oil Cooling" in this Chapter. After the lube oil flows through the twin filter (18) -- which can be switched from one half to the other while the turboset is in operation -- it reaches the lube oil distribution system (20). From there, it flows through the various supply orifices to reach the bearings and the other users. Emergency Cooling Oil System A failure of the AC power system or of both lube oil pumps (10) and (11) causes pressure in the lube oil system to collapse. If either of these should happen, there is a DC auxiliary oil pump available to supply all users with lube oil during the close-down (trip) of the turbine, thereby preventing damage due to a lack of lube oil. Jacking Oil System (50) The DC jacking oil pumps (48) and (49) mounted on the base plate of the auxiliaries block are in operation during start-up and rotor barring operation. These press the lube oil into special oil pockets in the bearings of the gas turbine and generator blocks. This raises the turbine and the generator rotors so that they float on a film of oil, reducing wear on the bearings and the torque required for start-up. Normally, the jacking oil system is supplied from the lube oil distribution system (20). In case of an AC power failure, it is supplied by the emergency cooling oil pump (57). The jacking oil and emergency cooling oil pumps start up automatically if both lube oil pumps should fail. Power Oil System (65) It supplies oil to the power oil distribution system (C). The lube oil distribution system (20) supplies oil to the AC power oil pump (60), which pumps oil into the power oil system, which , in turn, supplies oil to the hydraulic control and protection equipment.



)*+,



Power Oil Forwarding (39) for the Hydraulic Rotor Barring Device This subsystem supplies the oil required for rotor barring to the lifting cylinder (41) of the hydraulic rotor barring device (40). The DC pump unit (34) pumps the oil to the control valve (38) of the power oil system for the hydraulic rotor barring device. The valve (37) maintains a constant pressure in the system. The manual power oil pump (35) can be used to carry out rotor barring in case of a DC power failure.

Safety and Monitoring Equipment An alarm is set off in the control room if: ● The oil temperature in the lube and power oil tank drops below the preset minimum level ●

The oil in the lube oil tank drops below the preset minimum level

● ●

Differential pressure across the twin filter (18) exceeds the permissible level. If the oil pressure then continues to rise, the appropriate bypass valve opens The lube oil temperature after the twin filter is too high or too low

●

The oil pressure in the lube oil distribution system (20) drops below the preset minimum level

●

If one of the three solenoid safety valves is activated.

An emergency trip of the gas turboset is initiated if: ● The lube oil pressure drops below the present minimum level ●

The bearing metal temperatures rise above the acceptable levels

●

The power oil pressure in the hydraulic control and safety system drops below the minimum level permitted.

Pressure limiting valves protect the lube and power oil system from overpressure.



)*+,



6.1.11. Cooling and Sealing Air System

Figure 6.1-17 Cooling and sealing air system Legend 1

Turbine

4

Journal bearing


7

Orifice


)*+, 2 3

Compressor Journal bearing


5 6


Thrust bearing Combustor

8 9

Orifice Filter

Main Features ●

Cooling and sealing air is withdrawn from the compressor

●

Short piping paths and the use of only a few fittings produce a compact, reliable system

●

With this effective cooling system, material temperatures in hot gas path components remain within permissible limits even at elevated gas turbine inlet temperatures The cooling air withdrawn from the compressor is returned to the process (except for sealing air for the blow-off valves and for any water and steam injection valves provided).

●

Description of the System The main subsystems of the cooling and sealing air system are: ●

The sealing air system for the compressor The cooling and sealing air system for the exhaust end of the turbine

●

The cooling air system for the turbine vane carrier

●

The cooling and sealing air system for the turbine rotor

●

The cooling system for the combustor.

●

Sealing Air System for the Compressor (Inlet End) (C) The sealing air is withdrawn behind the fourth stage of the compressor (2) (first blow-off point), and is directed through the labyrinth seal at the inlet to the compressor. It prevents unfiltered air from the compressor bearing section from penetrating into the compressor.

Cooling and Sealing Air System for the Exhaust End of the Turbine (A) The cooling air is withdrawn behind the fourth stage of the compressor (2) (first blow-off point), and is directed to the turbine shaft bearing section (13) on the exhaust end. It cools the face of the shaft, at the same time blocking out a back-flow of exhausts into the rotor cooling air system.

Cooling Air System for the Turbine Vane Carrier and the Turbine Vanes (B) The air for cooling the vane carrier and the first two rows of turbine vanes is withdrawn downstream from the compressor and directed to the turbine vane carrier. It cools the vane carrier in a flow counter to that of the hot gas (15), starting from the low pressure section (back stages) and going as far as the second stage in the vane carrier. The first row vanes in the turbine are supplied directly with air from the discharge end of the compressor via a separate supply line (16). During operation the vane carrier is continually surrounded by an air flow from the discharge end of the compressor.



)*+,



Cooling and Sealing Air System for the Turbine Rotor (B and D) A large portion of the cooling air is branched off downstream from the compressor and directed into the ring-shaped chamber in the shaft enclosure between the outlet from the compressor and the inlet to the turbine. From that point, the air is supplied to several sections: ● On its path from the ring-shaped chamber to the face at the turbine end of the rotor, the rotor cooling air flows through a swirl cascade that generates the tangential speed component required to produce a relatively axial approach flow to the rotor. ● The cooling air flows into the holes in the face of the rotor at the turbine inlet. From this point, some of it is directed into the blades in the first three stages (18), while the remainder cools the heat shield segments on the surface of the rotor and enters into the hot gas flow as leakage (17) between the segments. ● A small portion of the air from the discharge end of the compressor is withdrawn at the face of the rotor and is directed across the shaft seal on the shaft drum, without being recooled, as sealing air for the face on the turbine end (13). The rotor is also cooled in the area of the fourth and fifth stages of the turbine. For this purpose, air taken from the third compressor blow-off chamber is directed across a filter (10) and a condensate trap (9) into the exhaust end bearing casing. From there, it passes through a hole bored in the shaft to enter the pocket within the shaft (14). The cooling air flows through ducts to reach the blade roots and the heat shields of the fourth and fifth stages. It cools these components and then comes out to mix with the hot gas.

Cooling System for the Combustor The section, "Gas Turbine Block," describes how the cooling system for the combustor operates.

Safety and Monitoring Equipment Measurement of the cooling air temperature, with display and alarms in the control room: turbine, exhaust end, on the face of the rotor.



)*+,



6.1.12. Compressor Blow-off System Silencer Blow-off valve

To exhaust system

Control air cooler

Control air for blow-off valves

Condensomate Filter

Pressure reducing valve

Safety relay

Control valve block Figure 6.1-18 Compressor blow-off system


Three blow-off points with a total of four valves (two in stage 1, one in stages 2, and one in stage 3). The blow-off valves for stages 1 and 2 are mounted directly on the outer housing of the compressor. The blow-off valve for stage 3 is located under the outer housing of the compressor and connected to the exhaust duct via a blow-off air duct. Sound from the top-mounted valves is damped by the blow-off hood and silencer. Control air supplied by the gas turbine compressor and in shutdown mode by the wash cart compressor.



)*+,



Description of the System Function During start up of the gas turboset, the blow-off system prevents rotating stall and surge by producing normal flow ratios in the compressor. Excess air is blown off at four locations. This reduces the power required to drive the compressor.

Principle of Operation There are five basic operating conditions: ● Standstill ●

Start-up

●

Operation

●

Shut-down

●

Trip

Standstill Blow-off valves are in open position. For functional checks, or for compressor washing purposes they can be operated by connecting a wash cart compressor. Start-Up Blow-off remain open when the gas turbine is started up. The valves close, as soon as the gas turbine has reached 90 % of its nominal speed. Control valves are moved in that way that the safety relays will open passage for control air which in turn will close the blow-off valves. Stage 3 closing will follow at 95 % of its nominal speed. The control air withdrawn from the compressor is cooled in a cooler and cleaned in filters, switch over during operation can be accomplished. The pressure is reduced in valves. Operation Blow-off valves are closed. Shut-Down After deloading to idling the control valves move. Oil pressure is dropping and the safety relays change position do to their spring force. Control air will escape and as a result blow-off valves will open by spring force. Trip A trip will force the power oil system to collapse immediately. The safety relays change position to allow control air to escape. The blow-off valves will open by spring force.



)*+,



Safety and Monitoring Equipment ●

Limit switches monitor the "open" and "closed" positions of each blow-off valve individually.

●

The gas turboset cannot be started unless the valves are opened.

●

A malfunction of the blow-off valves is signaled by a general alarm in the control room.



)*+,



6.1.13. Compressor Cleaning "Off-Line" A

5

1

3

2

5

B 4

Figure 6.1-19 “Off-Line” Wet Cleaning Equipment Legend 1 2 3

Compressor Intake casing Distributor pipe

4 5

Intake manifold Nozzles


A B

Intake air Cleaning fluid


)*+,



Figure 6.1-20 Typical Wash Cart Legend 1 2 3 4

Electrical switchbox Manometer Not used Water hose

5 6 7 8

Water hose connection Grounding cable Electrical cable Not used

9 10 11

Water tank Water pump Water pipe

Main Features ●

Improved efficiency and power output resulting from periodic washing of the compressor.

●

Simple plug-in couplings to connect the hoses and cables to the mobile wash cart are built into the intake manifold of the gas turbine. ○

complete mobile wash cart, equipped with tank for cleaning fluid, pump, hoses and cables.

The System The gas turbine is shut down and cooled off at least to a preset limit. The wash cart is brought close to the gas turbine. Before selecting the wash program, the cleaning fluid hose, and the cable of the wash cart are connected to the gas turbine. The wash program is selected and the compressor cleaning progresses in several phases. The cleaning fluid, mixed in the wash cart tank, is sprayed into the compressor through nozzles radially installed around the rotor axis. After the cleaning fluid has been allowed to soak into the deposits for a prescribed time, the compressor is flushed in several stages with water and blown dry subsequently. The wash and rinse water is removed through manually operated water drain cocks. The gas turboset can be put back into operation immediately once the wash program has been completed.



)*+,



6.1.14. “On-Line” Wet Cleaning of the Compressor A

5

B 1

3

2

5 4

SM042

Figure 6.1-21 “On-Line” Wet Cleaning Equipment Legend 1 2 3

Compressor Intake casing Distributor pipe

4 5

Intake manifold Nozzles

A B

Intake air Cleaning fluid

Main Features ●

Improved efficiency and power output resulting from periodic washing of the compressor.

●

Spray nozzles installed in the intake section of the compressor

Description of the System In "on-line" cleaning, the compressor is cleaned while in operation. This is accomplished by spraying a mixture of cleaning fluid and water into the compressor intake air through wash nozzles. In a second phase, the compressor is rinsed with water. For this cleaning, use only fully demineralised water! Because some of the cleaning mixture penetrates into the hot turbine, there would otherwise be a risk of high temperature corrosion from ions of alkaline salts (mainly of sodium and potassium) contained in the water. This type of compressor cleaning is effective only for the first stages because the appropriate amounts of cleaning fluid cannot be sprayed into the compressor during operation. For that reason the combination of "off-line" and "on-line" cleaning is most effective of all. The "off-line" cleaning also reaches areas that are not affected by a cleaning while in operation. The "on-line" cleaning extends the interval before the next "off-line" cleaning is necessary. December 2003N:\Shared_Data\tendering\Offer\B\Berrouaghia\Technical 14H47\6_1gt - Closed - 04-12-2003 - 11H28.doc Page 43


)*+,



6.1.15. Drainage of Compressor and Combustor

Figure 6.1-22 Drainage system of compressor and combustor


Carries off wash water from the air intake system, the compressor, annular combustor and the equalizing section. Carries off liquid fuel from the annular combustor after a starting failure occured.

Description of the System The water and fuel draining system for turbine and compressor carries wash water from the air intake, compressor, turbine housings during the washing procedure. To accomplish this, the drain cooks are opened manually. A collector equipped with two level indicators is located in the drain line of the turbine. The purpose of this collector is to monitor the flow in the mentioned drain line. The valve in this drain line is opened electrically. The system is also used after a failed start of the gas turbine set to return liquid fuel from the turbine housing to the liquid fuel system via collector, drain pit into the waste water system: The water from the combustion chamber and water collected in the exhaust system upstream of the expansion joint may be contaminated with fuel oil if a start of the gas turbines fails. Therefore the December 2003N:\Shared_Data\tendering\Offer\B\Berrouaghia\Technical 14H47\6_1gt - Closed - 04-12-2003 - 11H28.doc Page 44


)*+,



water is collected in a drain pit formed by the foundation. From here it may be pumped through an oil separator either to the waste water system or to a waste oil barrel. The water drain in the exhaust system downstream of the expansion joint and the NOx-water from the control valve block are directly connected into the waste water system.

Safety and Monitoring Equipment The level in the drain pit and the collector is monitored. If the level is too high, an alarm is set off, and a start-up of the gas turboset is blocked under these conditions.



)*+,



6.1.16. Air Intake System, Pulse Filter 6 8

Dp measurement

11

12

4 13

3 4

9

7

10

2

1

1

SM050

SM049

Figure 6.1-23 Air Intake System with Pulse Filter (left: Elements in Horizontal Position; right: Elements in Vertical Position) Legend 1 2 3 4 5

Compressor Intake Manifold Intake Elbow Silencer Connection cone

6

Compressed air for Filter Element cleaning Filter Housing Filter Elements Intake Air Expansion joint

7 8 9 10

4

11 12 13

Pulse Filter Compressor for pulse air Bypass door

7 8

6 5

X

3

2

1

9

9

SM051

Figure 6.1-24 Air Intake System with Pulse Filter (Elements in Vertical Position)



)*+,




Filter specially developed for arid ambient conditions with severe dust loading, but also suitable for low dust concentrations and arctic conditions Single-stage filter system with high dust-removal efficiency Modular filter with the filter elements in a horizontal or vertical arrangement (see figures above). The modules are erected at an elevated level above the generator block. Large surface area and low passage velocity resulting from fold over of the filter medium Automatically controlled cleaning of filter elements during operation by means of a brief compressed air jet in a reverse direction opposite the main flow

The System The air drawn in flows from the outside to inside through the filter elements. Contaminants in the air are entrapped by the folded high-efficiency filter media forming a dust cake. Once cleaned, the air flows through the clean air ducts to the silencer, after which it passes through intake elbow and intake manifold to the compressor. The degree of fouling of the filter cartridges is monitored by measurement of the differential pressure. The filter elements are cleaned automatically either after the differential pressure attains the preset level or at fixed time intervals (at the choice of the customer). 2

3 1

4

1

1 3

SM052

Figure 6.1-25 Pulse Filter, Principle of Operation Legend 1 2

Cleaned intake air Cleaning air

3 4

Intake Air Dust filtered out



)*+,



The filter elements are cleaned in groups by jets of compressed air in counterdirection to the main flow. These pulses free the dirt that accumulates on the filter cartridges. The frequency and length of the pulses can be adjusted as required. The oil free compressed air used for cleaning is either taken from a central compressed air system or generated in an additional compressor (optional equipment). The cleaning of the filter cartridges does not affect air intake because there is only a group of few cartridges being blown out at any given time. For effective cleaning of the filter elements, a pulse air pressure from 6 to 8 bars is required. The system is equipped with bypass doors valves which are installed downstream from the filter and upstream from the silencer. When the differential pressure exceeds the preset limit the bypass doors valves are opened by the force of the differential pressure. When the differential pressure drops below the pre-set limit, the force of the built-in counter-weights or springs respectively close the flap valves. The gaskets installed in the valve seats assure a tight closure of the valve.

Safety and Monitoring Equipment ● ● ● ●

Measurement of differential pressure between the ambient air and the filter housing monitors the degree of fouling in the filter elements and indicates it locally. An alarm is initiated locally and in the control room if the differential pressure exceeds a preset limit, when the differential pressure exceeds the preset maximum value, the gas turbine is tripped. The pulse air pressure is monitored. An alarm is initiated if the pressure drops below the preset level Bypass doors are provided in the filter housing downstream from the filter to protect the filter and the filter housing from an excessive differential pressure (e.g., due to blockage of the filter because of dust or snowfall).



)*+,



6.1.17. Anti-Icing 3 2

4 1 5 M

7

6

SM046

Figure 6.1-26 Hot Air Anti-icing System Legend 1 2 3

Air heater Intake System Silencer

4 5

Compressor Orifice

6 7

On/Off Valve Anti-Icing System

Main Features ● ● ●

Prevents ice formation in the air intake system and on the compressor blading during critical ambient conditions, thereby increasing availability of the gas turbine Designed to warm the air during critical ambient conditions by mixing in hot air taken downstream from the compressor Manually started system so that the operator will take note of the changes in the process

The System The anti-icing system is set into operation manually. To avoid possible damage to the compressor blades, it is recommended that the system is started as soon as the alarm “Risk of Icing” is activated. The hot air withdrawn downstream from the compressor flows through the shut-off valve, the orifice and the silencer. It then passes through the distributor pipes and the blow-off slots, which are provided across the entire intake cross section. Then the hot air mixes with the intake air and warms it up.



)*+,



Safety and Monitoring Equipment ●

The temperature and the relative humidity of ambient air are measured.

●

The alarm “Risk of icing” is initiated in the control room, whenever the ambient air temperature is below +7 C, and at the same time the relative humidity is above 70% A limit switch monitors the “Closed” position of the control valve in the anti-icing system and displays it in the control room. The position of the control valve is monitored and indicated.

●



)*+,



6.1.18. Generator and Lube Oil Cooling System: Air Cooled 1

6

2

7

8

3

9

10

5

4

11

12

13

14 15

16

17

18 19

20

21 optional 22

23

24 29

25

27

26

28 31

32

30 33

34

36

38

35

40

37

39

A

Figure 6.1-27 Generator and Lube Oil Cooling System, Air Cooled Legend 1 to 4 Generator cooler 5 Generator 6 to 13 Shut-off flap valves 14 Generator cooling water system 15 Recooler (cooling capacity: 100%) 16 Throttle flap valve 17 Shut-off ball valve 18 Shut-off flap valve 19 Lube oil cooler 20 Throttle and shut-off flap valve

21 22 23 24 25 26 27 28 29 30

Temperature control valve Throttle and shut-off flap valve Throttle and shut-off flap valve (optional) Non-return valve Non-return valve (optional) Temperature control valve Circulating pump Circulating pump (optional) Lube oil system Lube oil system


31 Shut-off flap valve 32 Shut-off flap valve (optional) 33 Pressure limiting valve 34 Shut-off ball valves 35 Pressure accumulator 36 to 39 : Shut-off ball valves 40 Hand pump A

Water supply


)*+,



Main Features ●

Direct air recooling of the generator and lube oil cooling water

●

Water/air recoolers installed outside the gas turbine building or enclosure

●

●

A pressurized closed-circuit system with water or a mixture of water and glycol for cooling the generator and the lube oil Regulation of the cooling water temperature by a temperature control valve (minimum temperature limitation) Plate-type lube oil coolers integrated into the lube oil system

●

Regulation of lube oil temperature in the lube oil circuit

●

Modular design

●

The System Circulating pump (27) forwards cooling water (or a mixture of water and glycol) through the closed cooling circuit at a slight overpressure to the generator coolers (1) to (4), and the lube oil cooler (19). The generator coolers (1 to 4) as well as the lube oil cooler (19) can be separated from the system by closing the corresponding flap valves (6 to 13), (18), (20). The cooling water flow to the generator and the lube oil cooler is adjusted by flap valves (16), (20), (22) and (23). Additionally, the cooling water flow through each cooler can be adjusted by fixing the flap valves (6 to 13) and (18) in a throttling position. After passing the lube oil and generator coolers, the cooling water flows to the temperature control valve (21). To maintain the cooling water temperature within a pre-defined range, the control valve directs the flow, through water/air cooler (15) and/or its bypass. The AC fans cool the finned tubes of the recooler with ambient air. The filling unit with the hand pump (40) is used to fill or drain the intermediate circuit if there is no central water supply system.

Safety and Monitoring Equipment The pressure accumulator (35) compensates the changes in volume of the cooling water. The pressure limiting valve (33) protects the system against overpressure. An alarm is initiated if: ●

The pressure in cooling water system drops below a preset limit



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6.1.19. Exhaust System, Simple Cycle Power Plants With Vertical Silencer

Figure 6.1-28 Exhaust System with Vertical Silencer Legend 1 2 3 4 5

Diffuser Not used Not used Expansion joint Elbow

6 7 8 9 10

Turning vanes Duct supports Not used Not used Stack

11 12 13 14

Transition Platform (optional equipment) Silencer Acoustic turning wall

Main Features ●

Stack height adjusted to fit overall layout of the gas turbine power plant

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Internally insulated stack and ducts Gas-tight connection between the exhaust diffusor and the exhaust duct

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Expansion joints to allow for free expansion

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Acoustic and thermal insulation of mineral wool or ceramic fiber over entire height of stack

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Multi-layer corrosion protection paint



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Silencers built into the vertical part of the stack

The System Gas turboset with a simple cycle stack. Downstream from the gas turbine, the exhaust flows through the exhaust diffusor and the base of the stack, where the flow is turned by guide vanes and directed to the silencer. After passing through the exhaust duct, it flows out into the open air.



Gas Turbine and Auxiliaries Alstom

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