GT Auxillaries

8/6/2019 GT Auxillaries

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ABCDSohar APP2 x KA13E2-2 DP SFPV 2005-010

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6.1 Gas Turbine and Auxiliaries


6.1 Gas Turbine and Auxiliaries 16.1.1 Gas Turbine Block 26.1.2 Compressor Variable Inlet Guide Vanes 96.1.3 Combustor 116.1.4 Gas Fuel System 176.1.5 Gas Flow Metering 196.1.6 Fuel Oil System 206.1.7 Dual Fuel Capability 226.1.8 Ignition Fuel System 246.1.9 Not Used 256.1.10 Hydraulic/Pneumatic Control System 266.1.11 Lube and Power Oil System 306.1.12 Cooling and Sealing Air System 346.1.13 Compressor Blow-off System 376.1.14 Off-Line Wet Cleaning of the Compressor 396.1.15 On-Line Wet Cleaning of the Compressor 416.1.16 Drainage of Compressor and Combustor 426.1.17 Air Intake System 436.1.18 Evaporative Cooling System 456.1.19 Generator and Lube Oil Cooling System 476.1.20 Exhaust System, Combined Cycle Power Plant with Diverter Damper and BypassStack 49

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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 diffuser and foundation

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Figure 6.1-3 Cross-section lengthwise through the gas turbine block

Legend1 Rotor2 Exhaust end journal bearing3 Compressor end journal bearing

9 turbine housing10 Annular combustor11 Compressor inlet

16 Turbine vane carrier17 Turbine vanes18 Exhaust housing

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4 Thrust bearing5 Turbine blades6 Turbine blades

7 Compressor housing8 Compressor / combustor housing

12 Compressor inlet guide vanes (variable)13 Compressor vane carrier14 Compressor vanes

15 Compressor diffuser

19 Blow-off valve20 Blow-off hood21 Turbine-end support

22 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 weldedtogether

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 turbinecasing

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 processtemperatures possible

Internal air-cooling of the first two rows of turbine vanes and the first three rows of turbine blades

The turbine casing can be opened separately if required

Simple and effective convection cooling of the rotor and the vane carrier using air from thedischarge 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

72 EV burners, arranged off-set in pairs

The single annular combustor and the arrangement of the burners produce a very thoroughmixing in the hot gas. This means:

a uniform temperature distribution in the hot gas

full combustion

Short flames, resulting from the EV burners

Further developed 2nd generation of the "lean premix" technology with which the best emissionlevels so far anywhere in the world have been attained

Simple, compact burner design

Good flame stability

No flashback problems

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 installedbetween 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 intwo journal bearings (2, 3) and one thrust bearing (4)

The compressor casing and the turbine casing (7-9) which also surrounds the annular combustor(10)

The variable compressor inlet guide vanes (12) The compressor inlet (11)

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

The compressor diffuser (15)

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

The exhaust casing (18)

The blow-off system, with the blow-off valves of the first two stages (19) installed under the blow-off hood (20) (the valve for the third stage is mounted at the side and blows off into the exhaustduct)

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 thecompressor (21 stages). The turbine blades are fixed in position radially in "pine-tree" slots and arealso 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 spacersin 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 severethermal stressing from the hot gas. Air taken from the discharge end of the compressor providesadditional cooling for these segments. This air is also used to cool the first three rows of turbineblades (refer to the Chapter, Section "Cooling and Sealing Air Systems," for details). These actionsmake it possible to attain a higher process temperature, thereby increasing the power output andimproving the efficiency of the unit.

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Bearings

The rotor turns in two journal bearings (2, 3) mounted in their own casings, one at the compressorinlet (11) and the other in the exhaust casing (18). The axial position of the entire rotor train (includingthe 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 withpressurised oil supplied from a special system (refer to the ChapterLube and Power Oil System). Thetemperatures 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 orthe compressor casings.

Gas Turbine and Compressor Casing

The gas turbine casing comprises the actual turbine casing (9) and the exhaust casing (18) attachedto it. The first of these is made of heat-resistant material that can withstand the thermal stresses thatoccur during operation. The turbine casing encloses the turbine and the combustor (10) locatedupstream from it. It is used for the suspension of the turbine vane carrier (16) and the combustor. Thecasing is surrounded by the compressed air from the compressor, which cools the parts lying insidethe 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 itcan withstand the thermal stressing. The exhaust-end rotor bearing casing is attached at the middle ofthe casing. The bearing forces are transmitted across support struts between the bearing casing andthe 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 thethrust bearing (4). The attachment is the same as that on the exhaust end. In addition, the inlet casingaccommodates the compressor inlet guide vanes (11), which are variable. The compressor inletcasing also provides the central support on the foundation.

The actual compressor casing (7) is split vertically after the eighth stage in the compressor. The frontsection (Stages 1 to 8) is surrounded by two blow-off chambers. The blow-off valves (19) for thesehave been placed at the top under a hood (20). The third blow-off stage is located in the back sectionof 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 inFig. 2-1) are fastened to the back section of the compressor casing.

The internal parts built into both compressor casings form the vane carrier.

Compressor and Turbine Vanes

In the compressor, the casing also serves as the vane carrier. The vanes are mounted incircumferential grooves and fixed in place with spacers. All compressor vanes are made of heat-resistant chromium steels. The first five rows of vanes are coated to protect them against erosion andcorrosion.

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The turbine vane carrier is, like the shaft in this zone, covered with heat shield segments to protect itagainst 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. Followingthis use, the air then flows to the second row turbine vanes to cool them from the inside. The vanes ofthe 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 coatedto 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 theturbine zone to cool those zones and to block the penetration of hot gas and oil vapour into zoneswhere 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 bybuilt-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 whichinitiate a trip in case of an exceeding of the prescribed values. The relative shaft vibrations aremeasured 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 withthe pressure at the compressor end to calculate the turbine inlet temperature. Values higher thenprescribed cause a load shedding of the gas turboset.

Electronic overspeed detectors monitor the rotational speed of the rotor and initiate a trip and alarm ifthe 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

Legend1 Compressor2 Variable inlet guide vane row3 Linear drive4 Measurement of vane angle

5 Measurement of linear drive setting6 Control valve for linear drive7 Measurement of control valve setting8 Pilot valve

9 FilterA Power oil supplyB Power oil return

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

Automatic adjustment of the inlet guide vanes while the gas turbine is in operation via a controlcircuit (control parameters = optimum part-load efficiency of the combined-cycle unit and limitimposed 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; thering itself is driven by a hydraulic linear drive

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

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Description of the System

The guide vanes are actuated by adjustment ring and tie rod. This adjustment ring, which runs aroundthe circumference of the compressor casing inlet, is also mounted to rotate. It is moved by the lineardrive (3).

The linear drive itself is supplied from the power oil system (A). The control valve (6) controls theposition 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. Whenthe 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 gastemperature reaches the maximally permissible level -- one or the other -- the inlet guide vane startsto 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 de-loading of the gas turboset, the inlet guide vanes are directed in thedirection contrary to the one followed during start-up or loading. The exact procedure depends on thesituation in which the shut-down or the de-loading was initiated.


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 pre-set limit while in operation, an alarm isset off. If the vanes close even further, an emergency trip follows. The "Open" and "Closed" settingsof 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 valveis de-energised by a pressure measurement installed upstream from the valve, and shifts into a safesetting. This locks the inlet guide vanes in their position at that moment. The filter (9) upstream fromthe 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 controlroom 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

Legend1 Front segment2 EV burner3 Heat shield4 Support structure5 High temperature jacketing

6 Combustor housing (secondary section)7 Combustor housing (primary section)8 Cover plate9 Combustor suspension (in the parting

plane

10 Vane of the first turbine stageA Air from the discharge end of the

compressorB 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

EV burners

Transition piece to the turbine

Flame monitors Igniter

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 asecondary 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 andthe heat shield segments (3) attached above and below them. These parts are fixed in position by asupport 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 endof 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 vanesinto the surrounding chamber of the turbine casing. In so doing, it not only provides counter-flowcooling for the combustor, but also cools the turbine vane carrier. The cover plate on the burner endof the combustor (8) has holes through which the air from the end of the compressor can reach theEV burners.

Figure 6.1-8shows how these burners are arranged in the combustor. Neighbouring pairs are in eachcase slightly offset in their radius, producing effectively four rows of burners. The burners aremounted 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 turbinebecause the hot gas path can be kept quite short. In addition, the thorough mixing results in an eventemperature profile and a complete combustion.

During part-load operation, only every 4th burner is switched off so that the advantageous temperatureprofile can be maintained even at low loads.

Two electrically activated ignition torches supplied from a gas system of their own are installed forignition of the burner flames. The flame then spreads from burner to burner without requiring furtherintervention 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 combustorfor 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 ofexperience in developing and operating low NOx premixing burners and on investigations conductedin our research centre of the scientific principles involved in the behaviour of strongly swirled flows.

The EV burner consists of a hollow cone (3) split axially, with its halves displaced cross-wise from oneanother (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) atthe outlet of the burner, and mixes there with the air.

The burner geometry has been optimised so as to produce a strongly swirled flow with a back-flowzone freely stabilised within the combustion zone. Only in this zone the flow velocities are slowenough to allow the ignition of the fuel/air mixture, which has, in the meanwhile, become fullyhomogeneous. The described flow and the lean mixture of the air and fuel produce low flametemperatures, which result in the low emission levels attained.

If oil operation is offered during fuel oil operation, the liquid fuel is sprayed in through an atomisernozzle (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

Legend1 Opening for the gas outlet2 Liquid fuel for atomisation nozzle

(only for oil burning machines)3 Split cone

4 Gas channelA GasB Liquid fuel (only oil burning machines)

C Combustion airD 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 (fuel gas flowmeter and fuel gas filter not shown)

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 theworkshop

Separate valves for controlling the gas flow and for trip

Valves equipped with metal seals

System de-pressurised when the gas turboset is at standstill

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

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

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Principle of Operation

The fuel gas flows into the fuel system through the gas supply unit and the fuel supply line. The maingas shut-off ball valve divides the gas supply system from the fuel system. For ignition, the main gasshut-off ball valve and the trip valve open and the gas relief valves closes. During ignition not allburners are in operation. The control valve defines the amount of fuel for ignition, and that fuel is lit bytwo ignition torches in the combustor. Because the mixing conditions within the premixing zone of theburners during a run-up of the turbine do not guarantee the certainty of proper ignition, the ignitionprocess is supported by directing an additional flow of gas ("piloting") via one of the three lines intothe 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 synchronisation, according to the power output called for. Oncestable combustion conditions have been attained, the supply of gas to the tips of the burners switchesoff. The remaining burners are set in operation at high part load and work in gliding FAR (Fuel to AirRatio) mode up to approx. 70% load. Above this load level the turbine is run with all burners at thenominal FAR.

During a shut-down of the gas turboset, the control valves close first, followed by the trip valve andfinally the main gas shut-off valve. The gas relief valves open the connection to the outside air andde-load the system to ambient pressure.

In an emergency trip of the gas turboset, the control valves and the trip valve close immediately.


Limit switches monitor the "Open" and "Closed" settings of the main fuel gas shut-off valve, the gasrelief valves and, the valve for ignition with fuel gas, and the "Closed" setting of the control valves andthe 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 measurementbuilt 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 thepressure drops below the pre-set 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 Gas Flow Metering

Main Features Turbine flow meter with compensation for pressure and temperature

Conversion of measured data into electrical signals

Totalisation with the computer

Electrical signals for use with process computer and recorder

Transmittal of the signals computed locally to the control room

Connections for possible annunciation, recording, and processing instruments

Description

The turbine gas flow meter is installed upstream of the main gas shut-off valve. Flow meters, pressureand temperature transmitters are mounted directly on the metering tube. The pressure andtemperature values are converted into electrical signals and sent directly to a computer (flowcalculator) in a local cabinet. Together with the impulses (speed) from the gas metering wheel thecomputer calculates the gas flow and displays it in the local cabinet.

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6.1.6 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

The trip valve and the control, pilot, and blow-out valves have been incorporated into the controlvalve block

The pump, filter, and meter are mounted on the fuel oil block. This block is supplied completelypre-assembled, including piping and cables, and tested

The Combined Fuel Oil / NOx Water Block is located outdoors and suitable for any climate

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

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

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The fuel oil supply system supplies the fuel to the fuel forwarding system. The fuel flows through themain shut-off valve -which is equipped with both a motor and a manual drive - to reach the filter. Thefilter is of a twin design so that the half that is not in operation can be cleaned without having to stopoperation of the gas turboset.

The pressure limiting valve installed upstream from the filter protects the system againstoverpressure.

The metering of through flow is built in downstream from the fuel oil pump. This is needed, amongother 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 foratomisation. 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 fuelcan flow to the control valves.

To prevent an overheating of the fuel oil pump in operation, a certain minimum amount of fuel mustflow through the pump to cool it. For that reason, during a start-up of the gas turboset, a volume flowis pumped back into the tank through the fuel return line (Valve is open to the return line) until nominalspeed has been attained.

Inside the combustor, the liquid fuel is ignited by the two ignition torches installed there. Then thecontrol valves open further, at first as called for in the starting program and - after synchronisation -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 flowthat 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 tothe cyclone extractor and then into the tank. The leakage tank pump forwards the leakage fuel backinto the main tank.

After switch off a group of burners the parallel working NO x water system is operated for a few moreseconds to flush the oil lances and thereby to prevent them from coking. The procedure is possiblebecause 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 closecompletely, 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 thecontrol room if this valve fails to close fully.

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

The measurement of differential pressure across the filter sets off an alarm in the control room isthe 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 ifthere is not sufficient pressure present.

The measurement of pressure after the fuel oil pump initiates an emergency trip if there is notsufficient pressure present.

If the temperature drops below the minimum level acceptable (the viscosity of the fuel becomestoo high), the measurement of temperature after the fuel oil pump sets off an alarm in the controlroom. 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 emergencytrip of the gas turboset

The fire and explosion protection system monitors all endangered parts of the liquid fuel system.

6.1.7 Dual Fuel Capability

Main Features Increases the availability of the gas turboset

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

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 pre-set minimum level setsoff 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 de-loaded 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-offvalve. 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 flowto 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 processhas been completed when only fuel oil is flowing into the combustor, when the supply of gas has beenbroken off completely, and when the fuel gas system has been de-pressurised.

Should the gas turbine load prior to switchover have been in the range of 35% to 70% load, the fueloil 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 allsteps taking place in the reverse order, i.e., the gas system is activated and the oil supply is cut backonce the gas supply responds.

Note:

This design is based on the assumption that gas is normally burned as the main fuel and the oilserves as a standby fuel. For that reason, a fully automatic switch-over from gas to oil is sufficient fornormal operation.


If the gas pressure downstream from the trip valve drops below the minimum level required during theswitch-over process before operation on fuel oil has been enabled, the pressure measurementinitiates an emergency trip of the gas turboset.

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6.1.8 Ignition Fuel System

Figure 6.1-13 Ignition fuel system

Legend1 EV burners2 Ignition torches3 Switch-over and reducing valve4 Shut-off and relief valve5 Shut-off valve6 Relief valve7 Shut-off valve8 Shut-off valve9 Ignition gas system (propane)10 Non-return valve

11 Orifice12 Non-return valve13 Orifice14 Combustion air supply15 Non-return valve16 Orifice17 Non-return valve18 Orifice19 Gas cylinder

20 Gas cylinder21 Filter22 Gas orifice23 Gas exhaust fan24 Feed orifice for incoming air25 Ignition fuel module (part of the

control valve block)A External airB not used

Main Features Standard system separate from the main fuel system

Supplied from commercially available propane cylinders

Automatic switch-over to the standby cylinder during normal operation

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Ignition fuel block completely prefabricated, with cables, and tested

Increased startup reliability


Ignition with Propane Gas

Once ignition speed has been attained, the functional group "Combustor" switches on. The flow ofignition gas to the burner is enabled by the shut-off valves and the relief valve. The spark plugs builtinto the ignition torches are energised, start to glow, and light the ignition gas. The main fuel flows outof the EV burners into the combustor and is, in turn, ignited by the ignition flame. When ignition hastaken 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 pressurised in the "at

rest" position.

A main propane cylinder can be selected manually. The switch-over to the standby cylinder is doneautomatically. If one of the two propane cylinders is empty, the switch-over valve has to be used toswitch 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 providesforced ventilation of this module to draw off any gas leakage and thus keep the risk of fire andexplosion as low as possible.


Whenever pressure in the ignition gas line downstream from the filter drops below the pre-setminimum 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 inthe ignition gas line.

6.1.9 Not Used

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temperature6 Turbine inlet temperature

(calculated)

7 Measurement of active power8 Measurement of speed9 Ring-shaped fuel pipes10 Compressor blow off valves11 Variable inlet guide vane

adjustment12 Fuel oil system13 Main shut off valve14 Pressure limiting valve15 Fuel oil pump16 Minimum flow valve17 Fuel oil trip valve18 Fuel oil control valve

24 Control valve drive, with EHC25 Control valve drive, with EHC26 Fuel gas system

27 Relief valve28 Quick action relief valve29 Filter30 Fuel gas trip valve31 Relief valve32 Gas pilot valve33 Gas control valve34 Gas control valve35 Pilot valve36 Pilot valve37 Control valve drive, with EHC38 Control valve drive, with EHC39 Control valve drive, with EHC

44 Power oil pump45 Safety system oil pump46 Main section of the hydraulic

protection system47 Hydraulic / pneumatic safety trip forthe blow-off systems

48 Manual trip49 NOx water injection control valve50 NOx water injection control valve51 NOx water injection control valve52 Control valve drive, with EHC53 Control valve drive, with EHC54 Control valve drive, with EHCA Fuel oil supply systemB Fuel gas supply systemC 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.


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 foroperation 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 externalfactors (generator utilisation, air temperature, etc.), will maintain the pre-set setpoints. Their maincomponents are the control valves for fuel gas (32 to 34), for fuel oil (18 to 20), and for NO x waterinjection (49 to 51), including their drives with electro-hydraulic converters (37 to 39, 23 to 25, and 52to 54).

Protection Systems

The protection systems protect the gas turboset from serious damage should the control systems fail.

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The protection system is directed by a central set of valves (46) connected to the fittings involved viapower 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 thehydraulic/pneumatic piping system causes an immediate return to a safe setting of important systemcomponents supplied from that piping system (e.g., opening of the blow-off valves). This is in everyinstance checked by means of limit switches. The electrical components of the control and protectionsystems are de-energised while the gas turbine is in normal operation (open-circuit operation). Theonly exceptions to this rule are the "fire protection valves" (which have not, however, been shown onthe 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 theturbine).

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 fueloil. The signals received from the electronic turbine controls are transduced into an oil pressure

suitable for the valve drives in the electro-hydraulic converter connected to the drives. The hydraulicdrives (23 to 25) are equipped with springs that close the valves automatically when there is a drop-off in power oil pressure (which causes a trip). This cuts off the fuel supply. The NO x water injectionsystem operating parallel to this system functions in the same way. The electronic turbine controlstake over control of the valves involved (49 to 51). Obtain further information from the Section Fuel OilSystem 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 thesystem has been designed to the special requirements in controlling fuel gas. Obtain a more exactdescription 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 thestandby fuel. During dual fuel operation or an emergency switch-over from one type of fuel to theother, 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

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Initiating trip.

The protection systems include:

Electrical and electronic monitoring and protection:

exhaust gas temperature after the turbine (5), including calculation of the turbine inlettemperature (6)

electronic speed monitoring

an electro-hydraulic 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 injectionsystem 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 appropriatepart is applicable.

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6.1.11 Lube and Power Oil System

Figure 6.1-15 Lube and power oil system

Legend1 Turbine2 Compressor3 Generator4 Turbine journal bearing5 Compressor journal bearing6 Turbine rotor thrust bearing

7 Generator drive-end bearingsection

25 Lube oil supply orifice25 Lube oil supply orifice26 Lube oil supply orifice27 Lube oil supply orifice28 Lube oil drain sight glass29 Lube oil drain sight glass

30 Lube oil drain sight glass31 Lube oil drain sight glass

49 Jacking oil pump50 Jacking oil system51 Non-return valve52 Non-return valve53 Non-return valve54 Non-return valve

55 Non-return valve56 Non-return valve

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8 Generator non-drive end bearingsection

9 Generator auxiliary bearing

10 Main lube oil pump 211 Main lube oil pump 112 Shut-off valve13 Shut-off valve14 Pressure accumulator15 Orifice16 Temperature control valve17 Lube oil cooler18 Twin lube oil filter20 Lube oil distribution system21 Lube oil supply orifice22 Lube oil supply orifice23 Lube oil supply orifice24 Lube oil supply orifice

32 Lube oil drain sight glass33 Lube oil return34 Power oil pump for rotor barring device

35 Manual pump for rotor barring device36 Non-return valve37 Pressure limiting valve38 Control valve for rotor barring device39 Power oil system for rotor barring device40 Hydraulic rotor barring device41 Rotor barring device lifting cylinder42 Air intake filter43 Ventilation orifice44 Flame arrestor45 Deaeration flap valve46 Oil vapour fan47 Temperature control valve48 Jacking oil pump

57 Emergency lube oil pump58 Return flow orifice59 Non-return valve

60 Power oil pump61 Shut-off valve62 Non-return valve63 Pressure limiting valve64 Strainer65 Power oil system66 Auxiliaries block lube oil heater67 Tank68 Drain cock69 Auxiliaries blockA Cooling water inletB Cooling water outletC 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 main AC lube 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 lube oil pump (57), the power oil pump (32) for the hydraulicrotor 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 amanual 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.


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

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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. Duringprolonged periods at standstill, the built-in heater (66) maintains the lube oil at the minimumtemperature required for operation. During operation, one of the two main lube oil pumps (10) or (11)supplies the gas turboset with the lube oil required. Should the pump that is in operation fail, anautomatic switch-over to the other pump takes place. The pressure accumulator (14) takes over thesupplying 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 thetemperature -- either all through lube oil cooler (17), or some through the cooler and some through thebypass, or all through the by-pass. This keeps the lube oil temperature within the pre-set range. Thecooling system is described in more detail in the section "Generator and Lube Oil Cooling" in thisChapter.

After the lube oil flows through the twin filter (18) -- which can be switched from one half to the otherwhile the turboset is in operation -- it reaches the lube oil distribution system (20). From there, it flowsthrough the various supply orifices to reach the bearings and the other users.

Emergency Lube Oil System

A failure of the AC power system or of both main lube oil pumps (10) and (11) causes pressure in thelube oil system to collapse. If either of these should happen, there is a DC emergency lube oil pumpavailable to supply all users with lube oil during the close-down (trip) of the turbine, thereby preventingdamage 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 inoperation during start-up and rotor barring operation. These press the lube oil into special oil pocketsin the bearings of the gas turbine and generator blocks. This raises the turbine and the generatorrotors so that they float on a film of oil, reducing wear on the bearings and the torque required forstart-up.

Normally, the jacking oil system is supplied from the lube oil distribution system (20). In case of an ACpower failure, it is supplied by the emergency lube oil pump (57).

The jacking oil and emergency lube 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 oilto the AC power oil pump (60), which pumps oil into the power oil system, which, in turn, supplies oilto 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 hydraulicrotor barring device (40).

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The DC pump unit (34) pumps the oil to the control valve (38) of the power oil system for the hydraulicrotor 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.


An alarm is set off in the control room if:

The oil temperature in the lube and power oil tank drops below the pre-set minimum level

The oil in the lube oil tank drops below the pre-set minimum level

Differential pressure across the twin filter (18) exceeds the permissible level. If the oil pressurethen 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 pre-set 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 levelpermitted.

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

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6.1.12 Cooling and Sealing Air System

Figure 6.1-16 Cooling and sealing air system

Legend1 Turbine2 Compressor3 Journal bearing

4 Journal bearing5 Thrust bearing6 Combustor

7 Orifice8 Orifice9 Filter

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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 remainwithin permissible limits even at elevated gas turbine inlet temperatures

The cooling air withdrawn from the compressor is returned to the process (except for sealing airfor the blow-off valves and for any water and steam injection valves provided).


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 isdirected through the labyrinth seal at the inlet to the compressor. It prevents unfiltered air from thecompressor 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 isdirected to the turbine shaft bearing section (13) on the exhaust end. It cools the face of the shaft, atthe 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 downstreamfrom 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 asfar as the second stage in the vane carrier. The first row vanes in the turbine are supplied directly withair 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 ofthe 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 intothe ring-shaped chamber in the shaft enclosure between the outlet from the compressor and the inletto the turbine. From that point, the air is supplied to several sections:

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On its path from the ring-shaped chamber to the face at the turbine end of the rotor, the rotorcooling 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 theheat 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 therotor and is directed across the shaft seal on the shaft drum, without being re-cooled, as sealingair 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, airtaken from the third compressor blow-off chamber is directed across a filter (10) and a condensatetrap (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 andthe heat shields of the fourth and fifth stages. It cools these components and then comes out to mixwith the hot gas.

Cooling System for the Combustor

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


Measurement of the cooling air temperature, with display and alarms in the control room: turbine,

exhaust end, on the face of the rotor.

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6.1.13 Compressor Blow-off System

Control valve block

Toexhaustsystem

Silencer

Blow-off valve

Controlair cooler

Condensomate

Filter

Control air forblow-off valves

Pressurereducingvalve

Safetyrelay

Figure 6.1-17 Compressor blow-off system

Main Features 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 thecompressor.

The blow-off valve for stage 3 is located under the outer housing of the compressor andconnected 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 cartcompressor.

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Function

During start up of the gas turboset, the blow-off system prevents rotating stall and surge by producingnormal flow ratios in the compressor.

Excess air is blown off at four locations. This reduces the power required to drive the compressor.


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 theycan 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 turbinehas reached 90 % of its nominal speed. Control valves are moved in that way that the safety relayswill open passage for control air which in turn will close the blow-off valves. Stage 3 closing will followat 95 % of its nominal speed.

The control air withdrawn from the compressor is cooled in a cooler and cleaned in filters, switch overduring operation can be accomplished. The pressure is reduced in valves.

Operation

Blow-off valves are closed.

Shut-Down

After de-loading to idling the control valves move. Oil pressure is dropping and the safety relayschange position due to their spring force. Control air will escape and as a result blow-off valves willopen by spring force.

Trip

A trip will force the power oil system to collapse immediately. The safety relays change position toallow control air to escape. The blow-off valves will open by spring force.

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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 signalled by a general alarm in the control room.

6.1.14 Off-Line Wet Cleaning of theCompressor

Figure 6.1-18 Off-Line Wet Cleaning Equipment

Legend1 Compressor2 Intake casing3 Distributor pipe

4 Intake manifold5 Nozzles

A Intake airB Cleaning fluid

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

Piping permanently mounted from the stationary wash skid to the gas turboset

Complete wash skid, 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 pre-set limit.

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The wash program is selected and the compressor cleaning progresses in several phases. Thecleaning fluid, mixed in the wash skid 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, thecompressor is flushed in several stages with water and blown dry subsequently. The wash and rinsewater is removed through manually operated water drain cocks. The gas turboset can be put backinto operation immediately once the wash program has been completed.

Figure 6.1-19 Wash Skid

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6.1.15 On-Line Wet Cleaning of the

Compressor

5

A

2

1

B

4

3

5

Figure 6.1-20 On-Line Wet Cleaning Equipment

Legend1 Compressor2 Intake casing

3 Distributor pipe

4 Intake manifold5 Nozzles

A Intake airB 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


In "on-line" cleaning, the compressor is cleaned while in operation. This is accomplished by sprayinga 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 mixturepenetrates into the hot turbine, there would otherwise be a risk of high temperature corrosion fromions 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 appropriateamounts of cleaning fluid cannot be sprayed into the compressor during operation. For that reasonthe combination of "off-line" and "on-line" cleaning is most effective of all. The "off-line" cleaning alsoreaches areas that are not affected by a cleaning while in operation. The "on-line" cleaning extendsthe interval before the next "off-line" cleaning is necessary.

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6.1.16 Drainage of Compressor and

Combustor

Figure 6.1-21 Drainage system of compressor and combustor

Main Features Carries off wash water from the air intake system, the compressor, annular combustor and the

equalising section.

Carries off liquid fuel from the annular combustor after a starting failure occurred.


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 areopened manually. A collector equipped with two level indicators is located in the drain line of theturbine. The purpose of this collector is to monitor the flow in the mentioned drain line. The valve inthis 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 turbinehousing 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

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water is collected in a drain pit formed by the foundation. From here it may be pumped through an oilseparator 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 thecontrol valve block are directly connected into the waste water system.


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

6.1.17 Air Intake System

SM049

1

2

3

4

10

8

7 9

5

SM052

2 3

1

1

1

3

4

Figure 6.1-22 Air Intake System with Pulse Filter

Legend1 Compressor2 Intake Manifold3 Intake Elbow4 Silencer5 Connection cone

6 Compressed air for Filter Elementcleaning

7 Filter Housing8 Filter Elements9 Intake Air10 Expansion joint

1 Cleaned intake air2 Cleaning air3 Intake air4 Dust filtered out

Main Features 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

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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 briefcompressed 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 airare 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 throughintake 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 pre-setlevel or at fixed time intervals (at the choice of the customer).

SM052

2 3

1

1

1

3

4

Figure 6.1-23 Pulse Filter, Principle of Operation

Legend1 Cleaned intake air2 Cleaning air

3 Intake Air4 Dust filtered out

The filter elements are cleaned in groups by jets of compressed air in counter-direction to the mainflow. These pulses free the dirt that accumulates on the filter cartridges.

The frequency and length of the pulses can be adjusted as required.

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The oil free compressed air used for cleaning is either taken from a central compressed air system orgenerated in an additional compressor (optional equipment).

The cleaning of the filter cartridges does not affect air intake because there is only a group of fewcartridges 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.

When the differential pressure over the filter elements exceeds the pre-set limit protective measuresare taken to protect the filter house.

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 pre-setlimit, when the differential pressure exceeds the pre-set maximum value, the gas turbine istripped.

The pulse air pressure is monitored. An alarm is initiated if the pressure drops below the pre-setlevel

6.1.18 Evaporative Cooling System

SM268

Figure 6.1-24: Schematic function of evaporative cooler unit

Legend1 Intake Air2 Filter3 Evaporative Cooler

4 Droplet separator5 Silencer6 Compressor

7 Turbine8 Combustor

Main Features Evaporative cooling media, cellulose or glassfibre

Water sump tank with level control and centrifugal pump (flour level mounted)

Water circulating system including stainless steel piping, valves and water tank

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Water distribution manifold

Biocide treatment equipment

Blow down control

Automatic operation and remote start-up and shutdown

Antifreeze protection

The System

The basic idea is the introduction of water into the air entering the gas turbine compressor and coolingthis air by enthalpy reduction through the requested evaporation energy of the water. This cooled airresults in a higher compressor intake mass flow due to a higher air density which finally results in ahigher power output and efficiency of the gas turbine.

The energy of the air is reduced proportionately to the amount of evaporation that takes place. Thetype of evaporative cooler media used is a direct contact, irrigated media utilising crossfluted celluloseor glassfibre blocs which are impregnated with insoluble anti-rot salts and rigidifying saturants.

Water enters the sump tank to a water supply located on the outer side of the tank and the water levelis controlled by a float switch.

Water is supplied to the distribution manifold by a pump located outside the cooler. The distributionmanifold is located directly above the evaporative cooler media.

The distribution manifold evenly wets the media by spraying water through small holes, spaced alongits length, onto a deflector shield. Only a small percentage of the water pumped to the media is

evaporated, the remainder is filtering through the media and back to the water tank. The pumpcontinually recirculates water to the media. Water amount to the evaporative cooler media isregulated by a gate valve and can be monitored by a flow meter.

In order to prevent scale formation, a percentage of water must be discharged to the drain. This wateris referred to as blowdown or bleed-off. The exact amount will depend on conductivity of the water,and the rate of evaporation.

The design system ensures a uniform airflow to prevent water carry-over with air velocity leaving themedia between 2.5 to 3.5 m/s. However, a water droplet eliminator is included downstream to ensureno water re-entrainment into the airstream.

Safety and Monitoring EquipmentThe water amount in the tank is controlled by a level indicator. If the water level falls below a certainlimit, the water supply valve will open automatically to allow fresh water supply. On the other hand,the water supply valve will be automatically closed if the water level exceeds the upper limit.

The water blow down is controlled by a conductivity probe, which will open the drain valve if theconductivity exceeds certain limits.

The water supply pump is supervised by a pressure switch and will be stopped if unusual pressurevariations occur.

In order to avoid freezing in the system during cold weather conditions, the evaporative cooler system

will be drained automatically, in case the ambient temperature falls below 5 C.

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A failure of evaporative cooler during operation will also be indicated at the GT control room via acommon alarm signal.

Sensors: Temperature probe upstream and downstream of the cooler and conductivity measurement.

6.1.19 Generator and Lube Oil CoolingSystem

21

15

A

28

31 32

2629

30

27

33

36 37

38 39

40

34 35

51 2 3 4

146 7 8 9 10

16

12 13

1718

19 20

optional

2322

24 25

11

Figure 6.1-25 Generator And Lube Oil Cooling System, Air Cooled

Legend1 to 4 Generator cooler5 Generator6 to 13 Shut-off flap valves14 Generator cooling water system15 Recooler (cooling capacity: 100%)16 Throttle flap valve

17 Shut-off ball valve

21 Temperature control valve22 Throttle and shut-off flap valve23 Throttle and shut-off flap valve (optional)24 Non-return valve25 Non-return valve (optional)26 Temperature control valve

27 Circulating pump

31 Shut-off flap valve32 Shut-off flap valve (optional)33 Pressure limiting valve34 Shut-off ball valves35 Pressure accumulator36 to 39 : Shut-off ball valves

40 Hand pump

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18 Shut-off flap valve19 Lube oil cooler20 Throttle and shut-off flap valve

28 Circulating pump (optional)29 Lube oil system30 Lube oil system

A Water supply

Main Features Direct air re-cooling of the generator and lube oil cooling water

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

A pressurised closed-circuit system with water or a mixture of water and glycol for cooling thegenerator and the lube oil

Regulation of the cooling water temperature by a temperature control valve (minimumtemperature 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 closedcooling 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 byclosing 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 theflap 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 controlvalve (21). To maintain the cooling water temperature within a pre-defined range, the control valvedirects the flow, through water/air cooler (15) and/or its bypass. The AC fans cool the finned tubes ofthe recooler with ambient air.

The filling unit with the hand pump (40) is used to fill or drain the intermediate circuit if there is nocentral water supply system.

Safety And Monitoring EquipmentThe 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 pre-set limit

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6.1.20 Exhaust System, Combined Cycle

Power Plant with Diverter Damper and BypassStack

Figure 6.1-26 Exhaust System, Standard, Combined Cycle Power Plant

Legend1 Diffuser2 Not used3 Not used4 Expansion joint5 Diverter casing

6 Not used7 Duct supports8 Expansion joint9 Support10 Stack

11 Transition12 Platform (optional equipment)13 Silencer14 Not used15 Blade

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

Internally insulated stack and ducts

Gas-tight connection between the exhaust diffuser and the exhaust duct

Expansion joints to allow for free expansion

Acoustic and thermal insulation of mineral wool over entire height of stack

Diverter damper

Multi-layer corrosion protection paint

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Silencers built into the vertical part of the stack

The System

Gas turboset with a bypass stack and diverter damper.

Downstream from the gas turbine, the exhaust flows through the exhaust diffuser into the divertercasing. Depending on the position of the diverter damper it is directed to the stack or through the heatrecovery steam generator (HRSG).

Documents

GT Auxillaries