1. ACKNOWLEDGEMENT
WE HEREBY TAKE THIS OPPORTUNITY TO THANK NTPC LTD. TANDA FOR
GIVING US THIS OPPORTUNITYTO CONDUCTOURTRAINING IN NTPC LTD.,
TANDA. WE ARE GRATEFUL TO MR. SANJEEV GUPTA(DGM,C&I) FOR
ALLOWING US TO CONDUCT OUR TRAINING IN THE CONTROL &
INSTRUMENTATION DEPARTMENT.WE ARE HEARTLY INDEBTED TO
OURPROJECT GUIDE Mr. LALIT KUMAR SINGH (Dy.SUPT,C&I)FOR
PROVIDING US WITH DETAILED IN DEPTH KNOWLEDGE AND VERY USEFUL
INFORMATION ABOUT THE PROCESSES AND SYSTEMS USED IN THE
PLANT.HIS SUPPORT WAS INSTRUMENTAL IN OUR TRAINING BEING
FRUITFULL.WEARE ALSO VERY TANKFUL TO ALL THE OFFICERS AND STAFF
OF NTPC LTD., TANDA FOR EXTENDING A HELPING HAND WHENEVER WE
NEEDED IT.
WITH REGARDS
--------
(VOCATIONAL TRAINEE)

2. INTRODUCTION
NTPC is the largest power generation company in India, with
comprehensive in-house capabilities in building and operating power
projects. It is producing 28,644MW. Its family consists of 18 coal based
power plant producing (23209 MW) and 8 gas based power plant having a
capacity of (5435 mw). It is also setting up a hydro based power plants
having capacity of 2471MW. It is one of the largest Indian companies with
a market cap of more than US$50 BILLION and has total assets of around
US$ 20 BILLION. In this firm government has 89.5% stake and 10.5% with
public. NTPC is ranked 463rd
biggest company in the world,5th
biggest
Indian company and 2nd
largest Asian power generator. It produces
26350MW which is 20.18% of the total 130,539MW of all India
consumption. More than one-fourth of India’s generation with one-fifth
capacity. The next largest power utility owns 7.9% of market share in
terms of capacity and 8.12% of share in terms of units generated. NTPC’s
vision is to become world class integrated power major, powering India’s
growth, with increasing global presence. It also develops and provides
reliable power, related products and services at competitive prices,
integrating multiple energy sources with innovative and eco-friendly
technologies andcontributes to society. NTPC stations are regular
recipients of CEA’s meritorious performance awards. This firm is also well
concern about the environmental factors. It uses world’s largest ESP’s and
also gives emphasis on environmental monitoring along with efforts to
increase energy efficiency.
BRIEF HISTORY OF THE POWER PLANT(TANDA)

3. This prestigious power plant was inaugurated by late Prime Minister “Smt.
Indira Gandhi” at 30th
December 1981. It is located 22km away from the
distt. Of Akbarpur (Ambedkar Nagar) and 60km(Approx) fromFaizabad in
the state of Uttar Pradesh. The capacity of the Power Plant is 440MW
consisting of the four units each of 110MW capacity. This Power plant
originally was owned by U.P. State Electricity board but the level of
performance that is P.L.F.(Power load factor) deteriorated which was
taken over by NTPC at the date of 15th
January on the year 2000 and It’s
now successfully run by the co-operation work of engineers, workers,
helpers and the other people who indirectly help the growth of this power
plant and is now running an average of 85-90% (PLF). In the starting period
of acquisition the PLF was these units were supplied, erected and
commissioned by M/s BHEL. The Power house was located on the bank of
river Saryu and West of the existing Mehripur pumping station of the
Tanda canal system. Necessary land, water and transport facilities are
available.
Land facility:-
1 .Land for Power Station including storage yard, Marshalling yard,
Switching yard :-120hectares
2. Land for ash disposal 160hectares
3. Land for colony 100hectares
Water facility:-
1. Water for once thru cooling 726.5 cusecs
2. Water for cooling tower 45.0 cusecs
Transportation facility:- Power station is on Tanda-Faizabad also
connected to Akbarpur-Faizabad. Nearest railway station 13km far
(surapur). Akbarpur is situated on Lucknow–mughalsarai Railway track.

4. The distance of plant from Akbarpur is 30km. Tanda town is about 8km far
from plant.
Production & Transmission:-
The 4*110MW power electricity is produced at the station using four
different units. Each unit generates 110MW power. The arrangement of
each unit is same. Since it is a thermal power plant, coal is used as the
main source of energy. This coal is mainly supplied from the
Dhanbad(Bihar) and otherplaces.Generated electricity is supplied to
following station:-
1.>Sultanpur 13.>Gorakhpur
2.>sultanpur 24.>Basti
Since this power plant had been undertaken by NTPC in 2000 its
performance in terms of power factor load(PLF) is improved in a great
manner and can be observed from the given graph:
FAMILIARIZATION OF THE POWER PLANT

5. BASIC OPERATIONS OF A POWER PLANT
Coal to Electricity
Generating steam from coal
Conversion of thermal energy to mechanical energy
Generation and load dispatch of electric power.
Coal to Electricity
NTPC, Tanda is a thermal power station which produces electricity by using
a non-renewable source of energy i.e. coal. Coal is converted into
pulverised form to enhance easy burning. The heat generated is used to
convert water to steam which is further used to move the turbine to
produceelectricity. NTPC, Tanda is capable of producing a total of 440 MW
of electricity. The main area of concern in any power plant is to increase
the efficiency of producing electricity along with maintaining the previous
best known efficiency The thermal power plant uses a dual ( vapour +
liquid) phase cycle. It is a closed cycle to enable the working fluid to be
used again and again. The cycle used is “Ranking cycle” modified to include
super heating of steam, regenerative feed water heating and reheating of
steam. The figure shown below describes “Ranking cycle”. On large turbine
it becomes economical to increasethe efficiencyby using reheat, which is a
way of partially overcoming temperature limitations.

6. The above figure shows the ranking cycle graph which is used in a power
plant. The paths shown below the figure represents the complete the
whole steam and heat cycle as followed in different operation cycles of a
power plant.
BOILER: 4 no of radiant dry bottom natural circulation,vertical water tube
boiler with single reheat 380ton/hr of steam pressure 160kg per square
cm at 540 degree centigrade of temperature.
TURBINE AND TURBO GENERATOR: 4 no. of 110 MW each.
WATER TREATMENT PLANT:4x30 ton/hr capacity.
OUTER SUBSTATION:

7. a) Power Transformer: 4 no. of 125 MVA 11/220 kVA.
b) Reverse Transformer: 2 no. of 30/20/10 MVA 220/66/33 kVA.
RATED PARAMETERS:
Rated parameter related to output: 110 MW.
Economical Output: 95 MW.
Rated Speed: 3000 rpm.
Rated temp.of steam before steam valve: 540*C.
Max. temperature of steam before stop valve: 543*C.
Rated temperature of steam before IP casing: 540*C.
Max. temperature of steam before IP casing: 543*C.
Rated pressure of steam just before stop valve:130 atm.
Max. pressure of steam just before stop valve: 136 atm.
Normal pressure of steam before IP casing: 31 atm.
Max. pressure of steam just before stop valve: 37 atm.
Cooling water temperature: 32*C.
SYSTEM OF THE TURBINE:
2 Stop valve, one on either side of HP casing.
4 Control valves, 2 on either side of HP casing.
2 Stop valves, one on either side of IP casing.
2 Interceptor valves, one on either side of MP casing.

8. 2 Row circuit wheels, 8 moving wheel in HP cylinder.
8 Non regulated extraction and one reheat.
Weight of HP rotor (approx.): 5,500 kg.
Weight of IP rotor (approx.): 11,000 kg.
Weight of LP rotor (approx.):24,000 kg.
Direction of rotation:
Clockwise looking at the turbine from the pedestal 1.
Barring speed: 62 rpm.
DETAILS OF TANDA 110 MW
# TG is designed by M/S SKODA supplied and manufacturedby BHEL.
# TG are supported by 7 journalbearings & coupled by 3 rigidcouplings. Bearing
no. 2 is thrustcum journalbearing.
# HP TURBINE: Two concentric casing horizontally splittedup. Double Rowsingle
circuit wheel and 8 impulse stagewheels.
# IP TURBINE: Two concentric casing horizontally splittedup, 12 stage out of
which integratelly forged with shaft& 4shrunk fitted.
# LP TURBINE: 2X4 reaction stages when steam flow isdiabolie. All 8 wheels are
shrunk fitted.
# LP HEATERS: 1, 1A, 2, 2A are vertically mounted on LPcasing.
#EXTRACTION: 8 uncontrolled extraction, 3 fromLP turbine,4 fromIP turbine and
1 from HP outlet.
#BARRING GEAR: 62 rpm between LP and generator.

9. INTRODUCTION TO STEAM TURBINE
The steam turbine is the prime mover in which the pressureenergy of the
steam is transformed into the kinetic energy ofthe rotor and later it is
converted into electrical energy.
CLASSIFICATION OF STEAM TURBINE
1. According to the no. of pressure stages :
a) Single stage turbine,
b) Multistage turbine.
2. According to the direction of steam flow:
a) Axial turbine ,
b) Radial turbine.
3. According to the no. of cylinders :
a) Single cylinder turbine,
b) Double cylinder turbine,
c) Three cylinder turbine,
d) Four cylinder turbine.
4. According to the method of governing :
a) Throttle with turbine,
b) Turbine with nozzle governing.

10. 5. According to steam condition at inlet to turbine:
a) Low PressureTurbine: Using steam at a pressurebelow 5atm.
b) Medium PressureTurbine: Using steam at a pressurebetween 5 atm. to
40 atm.
c) High PressureTurbine: Using steam above40 atm.
6. According to action of turbine:
a) Impulse turbine,
b) Reaction turbine.
PARTS OF STEAM TURBINE BLADE:
1.BLADE: Blades of turbine are classified in following manner:
# According to steam action:
a) Impulse turbine,
b) Reaction turbine.
In case of Impulse turbine blade, pressure drop doesnot take place in
moving blades.
While in case of Reaction blade, pressure drop takesplace in moving
blades.
#According to Position:
a) Fixed Blade
b) Moving Blade.
# According to construction:

11. a) Free standing blade: This type of blade is not coveredby anything and
freely stand on the shaft of turbine.
b) Shroud blade: This type of blade is covered by a plateof iron on the tip
of the blade.
c) Laeed wined blade: When the blade is tightened bythick wire, it is called
Laeed wined blade. It is alsocalled ribbon wined or Damping wined or
Laeingwined blade.
NOMENCLATURE OF BLADE
CONSRUCTION OF FIXED AND MOVING BLADE
CONSTRUCTION OF IMPULSE AND REACTION TURBINE
2. ROTORS: The three rotors of turbine are supported ononly five bearings,
the thrust cum journal bearing beingcommon to HP and MP rotates. It is
the rotating part ofturbine. It is also termed as Shaft. It has
followingclassification:
a) Flexible Shaft: The working speed of such type of rotor isbelow their
critical speed.
b) Rigid Shaft: The working speed of such type of rotor ismore than their
critical speed.
3. BEARING: Bearings are classified in following manner:
a) Friction Bearing: In such type of bearings there is a lineof contact
between contacting surfaces.

12. b) Antifriction Bearing: In such type of bearing there is apoint contact
between contacting surfaces.
In NTPC Tanda, journal bearing which is a type of frictionearing is used to
support parts. There are 7 journalbearings among which second one is
thrust cum journal bearing.
4. COUPLING :Rigid type of coupling is used in NTPC Tandato connect the
shaft of turbine.
5. BEARING PEDESTAL: Two bearing pedestals, front and rear. The front bearing
pedestal carries all the governingsystem components, MOP and front HP
bearings. Therear bearing pedestal carries the thrust bearing and itsprotection
equipments.
STAGE: Pair of moving and fixed wheel is called a stage.
No. of stages in each turbine:
HP: 8 stages
IP: 12 stages
LP: 2x4 stages
Regenerative cycle: There are 8 stages:
LPT: 3extraction
IPT: 4extraction
HPT: 1 extraction in outlet of HP.
Among which:
Ext. 1 to5: LP Heater
Ext. 6: Deaerator
Ext. 7: HP Heater 1

13. Ext. 8: HP Heater 2
6. BALANCING HOLE: Balancing hole is provided in bladefor the passage of
steam. In NTPC Tanda, it exits inHP&IP turbine.
AXIAL SHIFT: The value of axial shift is 0.3mm.
DIFFERENCE BETWEEN IMPULSE AND REACTION TURBINES.
PARTICULARS IMPULSE REACTION
TURBINE:
1. Pressure drop only in nozzle not in both bladesin moving blade
2. Area of blade channel constant varying
3. Blades profile aerofile
4. Admission of not all around all aroundsteam
5. Power not much power much power
6. Space require less space require more space
7. Efficiency low high
8. Blade not difficult to manufacture.
DIFFERENE IN NOZZLE AND THROTTLING GOVERNING:
S.N. ASPECT THROTTLE NOZZLE
CONTROL CONTROL
1. Throttling loses sever no throttling loses
2. Partial admission low highlosses

14. 3. Heat drop lesser higher
4. Use in both turbine in both turbine
5. Suitability small turbine medium and larger turbine
STEAM ADMISSION:
In caseof impulse turbine:-Steamadmission does not take place all around.
There is a 4arc steam admission in impulse turbine.
In case of reaction turbine:- admitted all around therotor.
STEAM EXPANSION IN TURBINE:
Steam coming out from superheater at 540degree C and 139kg per square
cm. Threecylinders of 2 set of main stop and governing valvearrangement
on either side of HP casing and each set consistof one stop valve and 2
governing valve assembling series.
The steam from the boiler is admitted the reheater where itheated at
original temp. The reheated steam is taken to IPcasing through combined
stop and interceptor valvearrangement at either of IP casing. The exhaust
from the IP
casing has taken directly the LP casing. The steam expandedin the LP
turbine to a very low blade pressure which ismaintained by the condenser
below atmospheric pressureabout 3% of makeup water is required to
condensate thelosses of cooling water due to evaporation in cooling
tower.
Finally steam exhausted by LP turbine iscondensed in the surface type
condenser type cooling waterfollowing through a large no. of tubes. The
HP, IP &LP turbine
coupled in series and mechanical power generated fromteam transmitted
to generator.

15. REGLUATION AND SAFTY EQUIPMENTS FOR TURBINEPREPARATION:
The scheme of regulation of turbine isregulated by four governing valves
(GV) on the inlet to the HPparts and by two interceptor valves (IV) on the
inlet to the LP
parts. The amount of opening at any instant of these valvesgiven by
preparation of secondary oil which is indirectlydependent upon the
primary oil preparation and directlyupon the spring fence in the
transformer and incidentaldependent upon the portion of limiter (LT)
during the standall oil scouting.
SPEED SENSING ELEMENT:
The speed sensing element islocated on the external of HP rotor maintain
the preparationin circuit of primary oil which is directly proportional to
thesquare of speed of 2850 to 3360 rpm correspond the primaryoil
preparation of 2.17 to 2.99kg at an oil temp of 50 degreeC under the same
condition. The speed of 3000 rpmcorresponds to a preparation of approx.
2.38atg.
TURNING GEAR:
It is located on the bearing pedestal between LPpart & the generator at
intended to rotate the rotor at 62rpmbefore the commencement of start
of apparatuses. Thisprevents over warming up of rotor.
PNEUMATIC CONTROL SYSTEM IN TURBINE:
The pneumatic control system provided to theturbine are liable on main
controlling of the valve ofextraction and gland sealing system all element
the finalhazard associated with hydraulic system for the pneumaticsystem.
Air is required at pressure 10atm &temp 80 *C.

16. AIR TANK:
It has capacity 2.5 cubic metric tank is clamped toground max pneumatic
permitted. Inside the tank pressure10atm &temp 80degree C. The air tank
provided with two airrelief valve at the top and a drain crook at the
bottom.
AIR VALVE:
Air valve each is provided for the two coldreheat flap. The fine extraction
valves monitor the admissionand release of compressor air inlet these
equipments. Eachair valve has an electromagnetic through which can
becontrolled automatically. All the air valve and theseassociated
equipment are located in instruments box.
EXTRACTION VALVE:
Pneumatic controls non-return valve. These areinsulated in the fine
extraction line. Each valve is designedaccording to the steam.
CRITICAL SPEED:
Maximum speed of rotor at which resonance orvibration starts at high
amplitude is called critical speed.
Ø Critical speed of generator: 2150rpm.
Ø Critical speed of IP turbine: 1570rpm.
Ø Critical speed of HP turbine: 3460rpm.
Ø Critical speed of LP turbine: 1500rpm.
LIMITING OPERATIONAL PARAMETERS:
The operation of turbojet at a particular load in range 80-110MW is
considered as stabilized operation provided thatparameters of steam do

17. not fluctuate and no seriousdeviation appear in the operation of set.
During such stableoperational period, change of load and other
operatingcondition must be to the minimum extent possible. It is to
benoted must be maintained at the rated valve only.
STEAM PRESSURE AND TEMPRATURE:
Ø PRESSURE:
During any twelve month operationalperiod, the average steam pressureis
not allowed toexceed the rated value. In maintaining this value, therated
steam pressure is not allowed to exceed 110%of the rated pressure.
However, the pressure increaseupto120% of rated pressure may be
permittedprovided the total amount of pressurefluctuationbetween 110%
to 120% and rated pressure does notexceed a total of 12 hrs during any
twelve monthoperational period.
Ø TEMPERATURE:
During any twelve month operationalperiod, at any turbine inlet point , the
averageadmitted steam temperature is not allowed to exceedrated
temperature .While maintaining this averagevalue ,the admitted steam
temperature is not allowedto exceed the rated temperature in excess of
8*C .However in exceptional cases, the temperature maymomentarily be
allowed to exceed the ratedtemperature by 14*C maximum, provided the
totalamount of the period of operation, between thelimits of 8*C and
14*C does not exceed 400 hrs in anyof 12 month operational period.
The turbine operation between the rangeof 14*C to 28*C in excess of the
rated steamtemperature is admissible provided the totaloperational
duration between these limits does notexceed 80 hrs/day any 12 months
operational period.
Steam is supplied to the HP and MP casinginlet ports through two parallel
supply lines; themaximum continuous difference in steamtemperature in

18. the individual steam line is allowed tobe 17*C ;however ,if the deviation
do not exceed theduration of 15 min the steam temperature differenceis
allowed to be 28*C maximum .
DESCRIPTION OF PARTS
STOP VALVE:
Stop Valve is used to stop or open the supplyof steam coming through
main stream tube, in HP Turbine.
CONTROL VALVE:
Control Valves are used to control thesupply of steam in HP Turbine after
passing the stop valve.It is 4 in number; two are on either side of HP
Turbine.
INTERCEPTOR VALVE:
Interceptor Valve is between HP.
Turbine and IP Turbine to regulate the supply of steam.
BEARING:
There are 7 bearings in TG set, out of which 6 arejournalbearing and one is
thrust cum journal bearing.
1,3,4,5,6,7: journal bearing; 2: thrust cum journal bearing.
There is sliding friction between the rotor and bearings.
Bearing 1, 3, 4, 5, 6, 7 resist only radial load while bearing 2resists both
radial and thrust load.

19. The rotor slides on bearing. Hence there is slidingfriction. The inner surface
of bearing is made of softermaterial called BAVIET. There is a little
clearance betweenthe rotor and inner surfaceof bearing where lubricating
oilfilm is formed. Lubricating phenomena of oil occurs throughwedging
action.
CONDENSER:
A steam condenser is a device or an appliancein which heat of steam is
absorbed by water and thus steamcondenses.
TYPES OF CONDENSER:
a) Jet Condenser,
b) Surface Condenser.
In NTPC Tanda, Dry Surface type condenser isused.
Surface Condenser:
SPECIFICATION OF SURFACE TYPE CONDENSER USED IN NTPC TANDA:
1. No. of condenser in each unit = 2
2. Condensers are supported on: 48 spring no. in each unit.
3. Type of condenser: Dry Surface type.
#Cooling water inlet is from bottom.
# Cooling water outlet is from top.
#Inlet and outlet cooling water connection are located atone side only.
#Other end of condenser has been left freely for expansion& contraction
reason.

20. 5.Cooling area of each condenser = 3380 sq.m
6.Quantity of cooling water required for two condenser =15400 cubic
meter at 33*C.
7. Steam flow to condenser = 267 ton/hr.
8. No. of passes = 2.
9. Condenser tube outer diameter = 22 mm.
Inner diameter =20 mm., Thickness = 1 mm.
10. Condenser tube material: cupronickel(90% Cu + 10% Ni)
11. Length of tube = 7.5 m
12. No. of tube = 13800.
GLAND STEAM CONDENSER:
Gland steam condenser is used tocondense the steam leaking through
turbines.
HOT WELL:
Hot well is used to store water formed throughcondensation of steam
coming from outlet of LP turbine intocondenser. It is below condenser.
CONDENSATE EXTRACT PUMP(CEP Pump):
Condensate extract pump(CEP) is used to extract water from hot well and
to supplymain mechanical ejector. It is in 3 of number out of whichany 2
are in running stage at any time.
BOOSTER PUMP:

21. Booster pump is used to pump the dripwater formed due to partial
condensation of steam in lowpressureheaters. The outlet of booster pump
is connected tothe outlet of 5th low pressure heater.
STEAM AIR EJECTOR:
To maintain vacuum in condenser airejector is used are of two types of air
ejector is used:
1. Mechanical Ejector
2. Vacuum Pump.
Here in NTPC Tanda Mechanical ejector is used .Itworks on venturimeter
principle. There are two type ofmechanical ejector:
a) Starting Mechanical Ejector
b) Main Mechanical Ejector
It is used to remove air from themixture .In case of ejector used for steam
plant where a highvacuum pressure is maintained in the condenser .It
isnecessary to use two mechanical air ejector in series toobtain maximum
vacuum .
Main mechanical ejector is also used forheating of water on account of
steam used in Mechanicalejector. There are 4 nozzles in two ejectors. This
also worksas heat exchangers.
DEAERATOR:
Itis used to separate out dissolved oxygen andair from water coming from
low pressure heater .Oxygen andair is separate out from water in order to
check corrosion ofpipes and other equipments.In deaerator, water is
sprinkled out fromnozzles; it is called atomization of water. The deaerator

22. issituated at a height in order to have a high pressure head forhaving a
good efficiency of boiler feed pump. BFP works assuction and discharge of
water. While suction process, theremay be caviation which can damage
the impellers of BFP. Toavoid caviation FST is situated at a reasonable
height.
FEED WATER STORAGE TANK (FST):
Feed water storage tankis used to store water for B.F.P. It is situated
belowdeaerator.Generally the whole set is termed Deaerator.
BOILER FEED PUMP:
Boiler feed pump is used to supply waterat a high pressure of requirement
to boiler. It is theequipment used having the maximum input of energy in
theplant. The pump used is centrifugal pump. Each of the unithas two
B.F.P.
MECHANICAL SEAL COOLER:
Mechanical seal cooler is usedfor cycling of feed water leaking through
boiler feed pump.Thus it stops more leakage of water.
ECONOMIZER:
An Economizer is a device in which thewaste heat of flue gases is utilised
for heating the feed waterin steam generating set.
LOW PRESSURE HEATER(LP Heater):
Low pressureheaters are used toheat water coming from main mechanical
ejector. They are 5in number.

23. HIGH PRESSURE HEATER:High pressure heater is used to heatwater
coming from BFP. From high pressure heater water isfed to economizer.
OIL PUMPS:-
MAIN OIL PUMPS(MOP)
This is centrifugal single stage double suction pumpmounted directly on
the HP rotor extrusion & is housed inthe pedestal bearing. In normal
operation of turbine, thecompletely quantity of oil required by turbo-set is
suppliedby main oil pump. MOP supplies oil the injector forlubrication and
for the governing & oil operated protection.
The lubrication oil is collected in oil cooler the 42 to 45*Cbefore entering
the bearing 3. Oil cooler are provided.
STARTING PUMP:
The rotor driven main oil pump can operate systemonly at about 2800rpm.
Hence to meet the required ofstarting and sloping the system.
EMERGENCY PUMP:
In discharging oil to the bearing when the lubricatingoil pressure drop to a
present valve. There are two EOP ondriven by 10kw AC motor & the 2nd
by 9.2kw DC motorlocated at ecometer with suction from the oil tank.
TYPE OF LUBRICATING OIL USED IN NTPC TANDA:-
Servo prime 46 supplied IOCL.
OIL REQUIREMENT:-

24. Ø Total required of oil for entire set: 23,400 lit.
Ø Out of which turbine required: 19,000 lit.
Ø Generator required: 4,400 lit.
Ø Make up oil for set: 38lit/day.
HEATERS:
There are 8 heaters provided from each 110kw, twohigh pressure & one
heaters act as a dearator of thecondenser. For shake of optimization
essentially equalfeed water temp rise cross LP Heater 1 to 5 dearator&HP
heater. 1 is aimed at the rise across the other. Forthe equal feed water
enthalpy rise for the heater isimpossible. In actual practice, turbine has
naturalextraction. Since extraction of steam can be removed atthese
points with little pressure. Cycle can be adjustedfor equal enthalpy rise.
GLAND STEAM SYSTEM(GSC):-
The turbine rotors needs the protection of casingat both ends so that they
must be coupled at the placewhere the rotor must be sealed against the
atmosphereso that the high pressure steam inside the take outwaste fully
or at the cold atmosphereair does not enterthe casing in HP & IP. Both the
ends have steam at apressure much higher the atmosphere in LP casing.
Thispressureis below the atmosphere. Hence glands areprovided at casing
end.

25. BASIC CYCLE OF A POWER PLANT
For proper functioning of a power plant ,its working operation has been
divided into following main operation cycles.
Steam cycle
Feed water cycle
Condensate water cycle
Primary air cycle .
Flue gas cycle
Secondary air cycle
EXPALAINATION OF POWER PLANT CYCLES
STEAM CYCLE:This cycle basically deals with the flow of steam at
different pressureand temperature to different turbines namely HP,IP and
LP turbines which is connected to the generator. It can be explained from
the figure shown below

26. Steam coming out fromsuper heater at 540degreeC and 139kg per square
cm. Threecylinders of 2 set of main stop and governing valvearrangement
on either side of HP casing and each set consistof one stop valve and 2
governing valve assembling series.The steam from the boiler is admitted
the reheater where it heated at original temp. The reheated steam is taken
to IPcasing through combined stop and interceptor valvearrangement at
either of IP casing. The exhaust from the IPcasing has taken directly the LP
casing. The steam expandedin the LP turbine to a very low blade pressure
which ismaintained by thecondenser below atmospheric pressureabout
3% of makeup water is required to condensate thelosses of cooling water
due to evaporation in cooling tower.Finally steam exhausted by LP turbine
iscondensed in the surface type condenser type cooling waterfollowing
through a large no. of tubes. The HP, IP &LP turbinecoupled in series and
mechanical power generated fromsteam transmitted to generator.

27. Feed water cycle :-this cycle deals with the flow of water to boiler
feed pump from feed storage tank ,which is later fed to the boiler drum
passing through high pressure heater and economizer
This system plays an important role in the supply of feed water to the
boiler at requisite pressure and steam/water ratio.this system starts from
boiler feed pump to feed regulating station via HP heaters.
Boiler feed pump : this pump is horizontal and barrel design driven by an
electric motor through a hydraulic coupling. all the bearings of the pump
and motor are forced lubricated by oil lubricating system.The feed pump
consists of pump barrel into which is mounted the inside starter, together
with rotor. water cooling and oil lubricating are provided with their
accessories. The brackets of the radial bearing of the sunction side and the
radial and thrust bearing of the discharged side are fixed to low pressure
cover.

28. High pressure heater: these are regenerative feed water heater operating
at high pressureand located by the side of turbine. It is connected in series
on feed water side and by such arrangement the feed water after feed
pump enters the hpheater.the steam supply to these heater from the
bleed point of the turbine through motor operated valves.
Condensate water cycle:It deals with the water flowing through
the condenser which plays an important role in increasing the efficiency of
the plant. It consists of a feedback path from main ejector to hot well.
The steam after condensing in the condenser known as condensate, is
extracted out of the condenser hot well by condensate pump and taken to
the de-aerator through ejectors, gland steam cooler and series of LP
heaters
Condensate pump : the function of these pumps is to pump out the
condensate to the deaerator taken to the de-aerator through ejectors,
gland steam cooler and series of LP heaters. This pump is rated generally
for 160 cubic metre/hour at a pressure of 13.2 kg/cm square.

29. LP heater :- there are four lp heater in which 4 extraction are used.these
heaters are equipped with necessary safety valves in the steam space level
indicator.the condensate flows in the u tube in 4 passes and extraction
steam washes the outside tubes.
Deaerator: the inner corrosion can be prevented by removing dissolved
gases from the feed water.it can be achieved by embodying into the boiler
feed system a deaerating unit whose function is to remove the dissolved
gases.it works on two principles:: henry law and solubility law.
Solubility law : solubility of gases decreases with increase in pressure and
/or decrease in pressure.
Henry law : the mass of gas with definite mass of liquid will dissolve at the
given temperature and is directly proportional to the partial pressure of
the gas in contact to liquid.
 Primary air cycle :- In this cycle, air is used to carry pulverized coal
from mill to the burning zone of boiler.
 Flue gas cycle :- In this cycle, gas containing waste materials are
removed from the system using various techniques like
electrostatic precipitator , ID fans etc. The flue gas, before being
removed is used to heat the primary and secondary air.
 Secondary Air cycle:- In this cycle, fuel is mixed with air (known as
secondary air) for proper burning of coal.

30. BOILER
 A STEAM GENERATOR IS A COMPLEX INTEGRATION OF THE FOLLOWING
ACCESSORIES:
1. ECONOMISER 7. DIV PANEL
2.BOILER DRUM 8. PLATEN SH
3.DOWN COMERS 9. REHEATER
4.CCW PUMPS 10. BURNERS
5. BOTTOM RING HEADER 11. APHs
6.WATER WALLS

31. ECONOMISER
• Boiler Economiserare feed-water heaters in which the heat from waste
gases is recovered to raise the temperature of feed-water supplied to the
boiler.
• It preheats the feed water by utilizing the residual heat of the flue gas.
• It reduces the exhaust gas temperature and saves the fuel.
BOILER DRUM
• It is an enclosed Pressure Vessel
• Heat generated by Combustion of Fuel is transferred to water to become
steam
 Serves two main function.
 Separating heat from the mixture of water and steam.
 It consists of all equipments used for purification of the steam after being
separated from water.
BOILER DRUM LEVEL CONTROL
 Important for both plant protection and equipment safety.
 Maintain drum up to level at boiler start-up and maintain the level at
constant steam load.
 Decrease in this level will uncover boiler tubes and get overheated and
damaged.
 Increase in this level will make separation between steam and moisture
difficult within drum.
 Controlled circulation is required to maintain the difference in the density
between water and steam with increase in pressure.

32. DOWN COMERS
 It carries water from boiler drum to the ring header.
 They are installed from outside the furnace to keep density difference for
natural circulation of water & steam.
 Heating and Evaporating the feed water supplied to the boiler from the
economiser.
WATER WALLS
• These are membrane walls, no. of tubes are joined.
• Vertical tubes connected at the top and bottom of the Headers.
• Receives water from the boiler drum by down –comers.
ADVANTAGES
• Increase in efficiency
• Better load response simpler combustion control.
• Quicker starting and stopping
• Increased availability of boiler.
• Heat transfer is better
• Weight is saved in refractory and structure
• Erection is made easy and quick

33. DISTRIBUTED CONTROL SYSTEM
EXPLANATION
 It is a closed loop or feedback system.
 System is set to fixed value known as SET POINT.
 Deviation of the measured value from set value describes the controlling
action to be performed.
 Control value to be sensed by sensor and the deviation from SET Pt. is
measured and a Error signal is generated.

34. Types of controller used in a power plant
LOCAL
CONTROLLER
Outdated controllers
Individual controller for each
unit like turbine , boiler,
generators etc
Manual monitoring
DATA
ACQUISITION
SYSTEM
CONTROLLER
centralized data collection
centre. Manual monitoring
is done.
Outdated technology.
DISTRIBUTED
CONTROL
SYSTEM
Recent technology.topic to
discuss in detail.

35. DDCMIS – TECHNOLOGICAL BACKGROUND
PROGRESS OF INSTRUMENTATION USED TO IMPLEMENT AUTOMATIC
PROCESS CONTROL
• LOCAL PNEUMATIC CONTROLLERS
• MINIATURIZED AND CENTRALIZED PNEUMATIC CONTROLLERS AT
CONTROL PANELS AND CONSOLES
• SOLID-STATE CONTROLLERS
• COMPUTERISED CONTROLS (SUPERVISORY)
• DIRECT DIGITAL CONTROL(DDC)
• DISTRIBUTED MICROPROCESSOR BASED CONTROL
Disadvantages of earlier Systems
• Analog instrument panels required huge space, lot of wiring and are less
user friendly for monitoring of large number of parameters.
• Accuracy obtained with solid-state controls is not good and they tend to
drift with time.
• Supervisory controls are inflexible as changing of control configuration
requires change in routing of wires.
• Use of centralized control leads to complete failure during shutdowns.

36. BOP & CI SYSTEM
• CONSISTS OF OPEN LOOP CONTROL SYSTEM (OLCS) AND CLOSED LOOP
CONTROL SYSTEM (CLCS)
• OLCS - THE SEQUENCE CONTROL, INTERLOCK OF ALL THE PLANT SYSTEMS
WHICH ARE NOT COVERED IN THE SG-C&I AND TG-C&I. THIS INCLUDES
MAJORAUXILIARIES LIKE FD/ID/PA FANS, AIR-PREHEATER, BFP/CEP/CWP/
BCWP , DMCWP/CLCWP AND ELECTRICAL BREAKERS.
• CLCS - THE MODULATING CONTROL FOR VARIOUS IMPORTANT PLANT
PARAMETERS, LIKE FW FLOW (DRUM LEVEL), FURNACE DRAFT,
COMBUSTION CONTROL (FUEL FLOW AND AIR FLOW), PA HDR PRESSURE
CONTROL, DEAERATOR/HOTWELL/HEATER LEVEL CONTROLS ETC.

37. MAN-MACHINE INTERFACE AND PLANT INFORMATION SYSTEM
• 64-BIT SERVER/OWS WITH HIGH-SPEED AND LARGE MEMORY (256/512
MB RAM, 8 GB HDD FOR SERVER AND 128/256 MB RAM AND 4/6 GB HDD
FOR OWS) TO ENSURE FAST RESPONSE
• PROVISION OF LVS
• CONNECTION TO OTHER SYSTEM THROUGH STATIONWIDE WAN
• TRANSPARENCY NO 9 & 10
MMIPIS FUNCTIONALITIES
• VPC OPERATION
• OTHER OPERATOR INFORMATIONS THROUGH VARIOUS DISPLAYS
• ALARMS, LOGS, HISTORICAL AND LONG TERM STORAGE.
• PERFORMANCE AND OTHER CALCULATIONS
BRIEF INTRODUCTION OF MAXDNA
Bharat Heavy Electricals limited (BHEL), Electronics Division, has entered
into a Technical Collaboration Agreement (TCA) for the manufacture and
supply of new generation Distributed Control Systems 'MAX1000+PLUS' ,
for modern Power Plants & Industries, with MAX Control Systems (MCS)
Inc USA, part of METSO Automation.
The MAX1000+PLUS is now re-named as maxDNA. where-in DNA stands
for Dynamic Network of Applications. maxDNA is a network of applications
where diverse hardware and software solutions co-operate to allow the
plant to reach its greatest potential.
BHEL's Electronics Division has established itself in the area of Control &
Instrumentation for new power plants as well as renovation and
modernisation of existing power plants. A leader in the Indian Power
Sector market, it has already supplied and commissioned above200 sets of
DCS for thermal, combined cycle and hydro sets all over the country and

38. overseas.
MCS Inc., USA, former systems division of Leeds and Northrup, USA, is an
internationally reputed technology leader In both Power as well as
Industrial process control systems, with 70 years of rich experience in the
field.
Applications
maxDNA systems are used in many applications throughout the world
including electric power generation, co-generation, cement, glass,
ceramics, primary metals, chemicals and petroleum, water and waste-
water treatment and incineration plants.
BHEL offers a variety of solutions for Power Plants ranging from simple
control systems to complex unified automation for Power Plants of any
size. The synergy of BHEL's expertise in Power Plant Controls and cutting-
edge technology of maxDNA provides for unified DCS solution for entire
Power Plant comprising of Steam Generator, Steam Turbine Generator and
Balance of Plant C&I. The state-of-the art control system is also configured
for complete range of Hydro Turbine governing and auto sequence
controls, SCADA systems and for wide range of industrial process
applications.
The spectrum of applications in brief are as listed.
Power Plant Controls
o Steam Generator Controls
o Heat Recovery Steam Generator (HRSG) controls
o Steam Turbine controls
o IndustrialSteamTurbine Controls
o Balance of plant controls
o Data Acquisition and information management

39. o Hydro TurbineGoverning and Auto sequence controls
o Generator and Switchyard controls
o Electrical Systemcontrols
o Fossilpower utility plants
o Combined cycle power plants
o Captive power plants
o Simple cycle power plants
Industrial controls
ThemaxDNA allows easy integration of third party devices and
communication with external systems. The systemalso allows user
flexibility to operate a small stand-alonecontrol systemto a mega control
system with plant-wideautomation. Its open architecture permits the
integration of process control, management information systems, local
and wide area networks, PLC systems and SCADA systems
BHELs integrated Automation and Information Management System
maxDNA is a microprocessor based real time system. This system is
designed on modular basis, allows scalability and provides operator the
complete tool to increase the availability, efficiency and safe operating
state with respect to the Process component.
The maxDNA DCS product line provides regulatory control, sequential logic
control, operator interaction through CRTs (MAXSTATIONS) and
information management. The MAXSTATION can be configured as an

40. operator station, engineer's station, historian (MAXSTORIAN), gateway, or
link server (MAXLINKS) to foreign systems. It provides for high-resolution
graphics utilising a powerful graphical user interface - MAXVUE. The
maxDNA also provides a comprehensive set of tools (MAXTOOLS) for the
development of system application, configuration and installation.
maxPAC Process I/O
maxPAC input and output modules connect thousands of process
variables, controllable and element devices throughout the plant to the
maxDNA Plant Automation System. maxPAC I/O modules are available in a
number of input and output configurations to match the electrical
characteristics of the sensors, transmitters and controllable devices.
Key Features
High density I/O.
· Isolated Input/ Outputmodules.
· Supports fullredundancy.
· Both local and remote installations.
· Lower power consumption.
· Self calibrated analog modules.
· Remove and insert modules while powered.
· Modules have colour coded faceplates for rapid identification.
· Rotary address switches for fastset-up.
· All the modules that require field power include a frontmounted fuse
disconnect
and a LED fusestatus indication.
· All discretemodules include front mounted LEDs for input / output state.
· (15+1) bit Resolution for Analog inputs.

41. OPERATING ENVIRONMENT
MaxPAC I/O and related hardwarecomply with the following standards.
· ESD - IEC801-2.
· Surge- IEEE-472-1974 (ANSI C37 90a) surgewithstand test.
· RFI-801-3 with thecabinet door closed.
· Vibration - Sinusoidal vibration specification per SAMA PMC31.1 using
control
roomlevel; 1 mm displacement 5-15Hz, 0.5G 15-150Hz.
· Storagetemperature - 26 to 70 Degree C.
· Operating temperature 0 to 60 DegreeC.
· Relative Humidity; 5 to 90%, non-condensing.
SALIENTFEATURES
- The DCS Data Highway speed is 10/100 Mbps.
- Communication Network is full Duplex type.
- Intelligent Switched FastEthernet for communication with redundancy.
- 32 Bit Intel Multifunction Controller for OLCS & CLCS with WINDOWS CE
Operating System.
Intel Pentium IV OWS with WINDOWS 2000 for MMI /DAS.
- Distributed Data base on RPUs.
- On line documentation system.
- Centralized Engineering Station for programming, configuration and
downloading.
- Dedicated links for other system.
- Integrated SOEwith 1 milisec resolution functions are envisaged.
- Multilevel security systemare envisaged for differentfunctions like
engineering, databasechanging etc.
- Optical isolation for I/O modules.
- Scan time for critical analog signals is 20 milisec& others 100 millisec
orabove.
- Execution time for control logics is selectable from20/100/500millisec.
as per requirement.

42. - Interchangeability of Engineering station and Operator Workstation,
wherever necessary.- History with 1 second sampling rates and long term
storage& retrieval.
- Point database (GlobalData) accessibleat any station across the
Network.
- Selective I/O redundancies depending on process criticality.
- Enhanced graphic capabilities.
- OPCcomplaint.- Status of modules available on OWS.- Controller logic is
available on OWS (on-line).
-Facility for simulation of control logic schemes with virtual processor.
HARDWARE ENVIRONMENT
maxDNA technology is used for monitoring and manage process control
environment through a maxSTATION . it is used for man machine
interface.maxSTATION can be set up as an operator’s workstation. it uses
maxVUE graphical interface software to provide a graphical view of the
process and comprises of both standard and custom display. Engineer’s
workstation is used for creating and maintaining configurations and
process controldocumentation using maxDPU tools and maxVUE graphical
configurator software. it is also used to create and maintain custom
graphic displays using the maxVUE graphics editor software.maxSTATION
collects and manages process and event history, reporting, and archiving
using the maxSTORIAN history and archiving software.

43. maxSTATION Hardware
According to the function to be performed by a particular workstation
determines its minimum hardware requirements. Such as for collecting
data one needs a larger hard diskthan operator’s workstation. So for its
proper functioning it must meet the minimum hardware requirements.
mxaDNA components
The maxDNA Distributed control system consists of one or more
maxDNARemote Processing Units (RPUs) cabinets which contains,
 maxDPU Distributed Processing Units (DPUs), the process controller, provides
control and data acquisition functions.
 Input/Output devices (I/Os) for monitoring and controlling the actual process.
 One or more maxSTATIONs configured as operator or engineer workstations.
This technology is used for man machine interface. It is essential to have a
network system between workstation and field for the interface.
Network Overview
maxDNA technology uses a client/server architecture. maxDPU acting as a
server collects information, stores it and ultimately transfers the
information to the appropriate maxSTATION clients .maxSTATIONs and
maxDPUs communicate with one another via maxNET. The maxNET
Network is a fully redundant 10/100 Mb per second Ethernet network
using industry standard UDP/IP protocol for communications between
Workstation clients and servers.

44. maxDNA POINT DATABASES:
it is composed of point databases. A point databases created in maxDPU Tools,
consists of hardwareresources and control points. One configuration is permitted
per DPU or DPU pair, which may serve a group of Remote Processing Unit
cabinets.In a power generating plant, for instance, one configuration could
represent a burner management strategy, another a boiler control strategy, and
so forth.
Systemresources consists of RPU’s H/W,DPU,I/O Modules, power supplies, etc.
Control points consists of
EXPLANATION OF BLOCKS
Atomic Block : Function Block that implements smallestpossible function in
maxDPU. All Atomic Blocks are programmed into maxDPU.
Standard Block: derived Function Block that is part of maxDNA product. All
Standard Blocks are programmed using Atomic Blocks and/or other
Standard Blocks. End users, operations or consultants cannot customize
standard Blocks.
custom
BLOCK
Standard
block
ATOMIC
BLOCK
FUNCTION BLOCK

45. Custom Block :derived Function Block that is made from Atomic Blocks,
Standard Blocks and/or other Custom Blocks. New Custom Blocks can be
built and existing CustomBlocks can be changed by anyoneusing maxDNA-
engineering tools.
Operators may view pts fromany configuration at any operator’s workstation
provided the operator’s work station and DPUare attached to the samemaxNET
network and haveread access to specified domains.
Tasks performed by the maxSTATION:
1.>Display real time data from any DPUon the maxNET network in a single
graphic display.
2.> Display trend or X-Y data fromany DPUon the maxNET Network in a single
display.
3.>Access all control loops on the maxNET Network.
4.>Display the currentalarm summary display; available alarm information
is typically restricted
to a specific domain.
Working in maxVUE
maxSTATION software requires the Microsoft Windows® operating
system. It run as a standard windows application and respond to the
mouse and keyboard like any other windows package.
Input Devices
The maxSTATION accepts a variety of input devices including:
 MOUSE
 TRACKBALL
 Touch screen
 Keyboard
Use of mouse is similar to that in case of a computer.

46. Using the keyboard
maxSTATION can use both a normal QWERTY keyboard and an operator’s
keyboard .Engineer’s keyboard is required in an engineer’s workstation. it
is used to enter text and perform other function with special keys.
Operator’s keyboard has dedicated keys used to perform specific tasks
such as acknowledging alarms or taking control action .
maxSTATION is the hardware platform through which one can view and
manage process control environment. It can be set up as an operator’s or
engineer’s workstation and the compatible software must be installed,
however security alerts are set , the protective key (dongle) and
passwords are different . Each of the standard configurations is shipped
with Processors and Power Distribution mounted and internally
interconnected.
Connecting stations and DPUs to the maxNET NETWORK
Workstations and maxDPUs communicate with one another over maxNET.a
redundantEthernet network. It is consists of two independent Ethernet networks
named as “A” and “B”. it is assumed that “A” is independent clone of “B”. This
network setup is consists of electrical and fiber optic cable fast Ethernet switches
and fiber optic converters. maxNET is an open system and does not rely on a
specific model of network hardware. In setting up this network, two types of
wires are used
metallic cable is used for interconnection inside the cabinets and for short
distance runs through areas that are not subject to electrical noise. Fiber optic
cable is used when it is necessary to span a large geographic area, to provide
electrical isolation between equipment groups or to reduce noise pickup in
electrically harsh environments. Both types of capable of carrying data at 10Mbps
or at 100 Mbps.

47. Network Layout Guidelines
During lay out of this network one should must be considered the following
factors like,Path from workstation to DPU. The number of switches must be kept
minimum. It is good practice to restrict the number to “3” between any
workstation and the maxDPU. Keeping the number of switches to a minimum not
only increases reliability but also make troubleshooting easier when a switch fails.
The maxNET “A” and “B” networks must be completely separate from each other
and from other network(the plant network). “A” and “B” cables must not be
connected to the same Ethernet switch. Cables of network A and network B
should not get mixed up. A’s cables must only be connected to network A
Ethernet card or switch, similar is the case with network “B” for this reason only
each of the connector has been labeled. The rear panel of each processor slot
must be similarly marked like “ A,B and P or LAN for a plant Ethernet connection).
Cables assembled in cabinets and desks at the factory contain a two line label.
The top line describes where the cable originates and the bottom line describes
where the cable terminates. This dual network structure of the maxNET
architecture provides high reliability through its redundancy. No single network
element can fail and prevent communications between any workstation and
maxDPU or DBM.
For more reliability network “A” and network “B” cables through physically
separate paths when installed at plant site. Accidently, if bunch of cables get
damaged it can be easily solved without interrupting the networks. Signal losses
can be reduced by establishing the metallic network connection or unshielded
twisted pair electrical cable.
CABLE MINIMAL REQUIREMENT
 Ethernet UTP 4 pair 24 AWG stranded wirefor any runs less than 20 ft.
 Ethernet UTP 4 pair 24 AWG solid wirefor any runs greater than 20 ft.
 Fiber optic cable:62.5/125ummultimodefiber with ST connectors.
Here we use plenum-rated insulation on the network cables for local fire
codes require it and for cabinet wires standard PVC insulation is accepted.

48. UTP cables comes in two varieties straight-through cable is used to connect
different types of devices (workstation to a switch or a switch to a maxDPU).
Crossover cable is used to connect similar devices(switch to switch). Some
devices haveboth the ports crossover and straight-through cable may be used
them. Cross over ports are typically labeled with an “X”. A single port on a
device may be used as either a straight-through or a crossover. Fiber optic
converters have a switch labeled MDI/MDI-X. When a peripheral device is
connected to the media converter we have to move the MDI/MDI-X switch on
the converter to the MDI position. Ethernet switches are used to interconnect
all nodes of the maxNET network. The switches used in a maxNET system must
meet some minimum functional requirements. However these switches must
meet certain requirements which are listed below:
HADWARE DUPLEX SPEED
maxSTATION Full duplex 10Mbps or 100Mbps
maxDPU4F Full duplex 10Mbps or 100Mbps
MaxDPU4E Full duplex 10Mbps
DBM Half duplex 10Mbps
Ethernet Switch Minimal Requirements
Must contain a minimum of two full-duplex 100 BaseTX ports for connections to
other switches.
120V ac 60Hz/240V ac 50Hz power
19 inch rack mounting
Must allow the user to manually configure the speed and duplex settings for each
port.
Ethernet Switch Desired Features
Support remote management (SNMP) to allow user to check and configure
switch settings and to read and reset port statics,it greatly helps in system
maintenance procedures.

49. This is maxDNA
maxDNA is the seamless combination of proven Plant Automation System hardware and a
Dynamic Network of Applications specifically designed to meet the needs of
electric power plants.
maxDNA is supported by a full range of life cycle services designed to increasethe
economic value of your plant. What makes the difference is that maxDNA was
created by application developers knowledgeable in all aspects of the operation
of power plants.

50. Electric Power Generation
Metso Automation offers turnkey solutions for all types and sizes of power plants.
For large fossilfired plants Metso Automation exclusively uses the D-E-B
coordinated controlphilosophy, an approach that assures theunified operation of
the boiler, its inputs, fuel, air and feedwater, with the turbine-generator output.
The D-E-B systemis a proven controlstrategy that is designed to meet the
number one objectiveof the power plant – match generation to demand, under
all conditions. Now in its fourth generation, D-E-Bhas been proven on over 900
large fossilfired power plants around the world – and it is only available from
Metso Automation.
Metso Automation is the leader in supplying systems and applications for eco-
efficient power plants. Metso engineers designed and supplied the systems for
world’s largestbiofuelled power plant. An advanced information management
systemwas supplied to accurately monitor and reportthe plant’s various
products (electricity, process steamand districtheating) to ensureproper
invoicing. Due to the boiler’s large size (550MWt) and widerange of fuels,
accurate monitoring of fuel consumption and efficiency would be next to
impossiblewithout the advanced applications designed by Metso Automation.
Over 4500 peopleare stationed in 37 countries around the world to providelong-
term supportfor all Metso Automation installations.
maxDNA configurationtools
Summary
Connects to DPU4Eand DPU4F – realor virtual
100% self-documenting – no off-line storageof database or diagrams
Create & edit logic diagrams

51. Rapid configuration speeds installation
Extensive on-line tools to aid debugging
Display & print logic diagrams
What-you-see-is-what-is-installed
for long-term ease of maintenance
maxDNA Configuration Tools are comprised of maxTOOLS and maxVUE Graphical
Configurator. Itis the set of softwareelements which are used to configure, edit
and maintain the Distributed Processing Units (DPU4Fs and DPU4Es) in a system.
maxDNA Configuration Tools can run in any maxSTATION. maxDNA Configuration
Tools are used to configure the modulating control strategies, the binary logic
control strategies, the DPU database, sequence of events reporting, alarm types
and setpoints, loop execution times, I/O card, bus, termination interface, and
maxNET interface in a DPU.
maxTOOLS
A configuration often starts with bulk data entry. maxTOOLS takes advantageof
relational databasemethodology to supportrapid and efficient entry and
manipulation of data. A flexible import of data supports initiation of maxDNA
databases fromcustomer databases, speeding time of entry as well as reducing
the potential for errors.
maxVUE Graphical Configuration
maxVUE GraphicalConfiguration takes over after bulk data entry to provide
object interconnection, and eventual on-line debug of the process. Both the
modulating and the binary or logic control loops are configured in a graphical
formatusing standard maxDNA algorithms and function blocks. A partial list of
the currentlibrary is listed in the table on the following page.
The initial step is the selection of the DPUdatabase fromthe overallproject
database. The DPUdatabase is then connected to the process I/O bus and the

52. individual I/O cards that convertthe field signals that are read by the DPU
software. The assignmentof I/O cards and channels per card is done at this time.
Sequence-of-events digital inputs points are identified to enable the DPUto read
the millisecond timestamps associated with all changes of state for these selected
points.
Each control loop is configured by selecting an algorithm and connecting the
inputs fromone algorithm to the outputs of other algorithms to achieve the
desired controlstrategy. Since maxVUE GraphicalConfigurator is object oriented,
a configured loop can be reused as the starting point in configuring similar loops
such as multiple coal mill temperature loops. Algorithms can be grouped into
customfunction blocks which can be configured as a single block with only the
block inputs and outputs shown.
Partial List of Algorithm Function Blocks
Absolute value
Add / subtract
Multiply
Divide
Mod
Exponential
Power
Squareroot
Totalizer
Calculate
Signal select
Leadlag
Analog input buffer
Analog output buffer
Digital input buffer
Digital output buffer
Pulse input / output
buffer
Auto manual
Limiter
PID
Feed forward
Participation member
Participation master
Controller combining
PAT out
Control select
Control add (bias)
Control multiplier
(ratio)
Control divider 1
Control divider 2
Function generator
Quality force
Not
And

53. Quad PAT buffer
Thermocouple in buffer
RTD input buffer
Device logic
Sequence master
Sequence step
Firstout
Timer on
Timer off
Timer pulse
Trigger edge any
Trigger edge fall
Trigger edge rise
Serial link bit pack
Serial link bit unpack
Alarm reporter
Alarm clock
Output driver buffer
Or
Exclusive or
Greater than
Less than
Equal
Not equal
Flip flop reset dominant
Flip flop set dominant
Flip flop no dominant
Analog tag
Digital tag
Steam properties
Flow compensation
Level compensation
User object
Group
Counter
Timer
As part of the configuration process, the execution class is also selected fromthe
three available time classes that are typically set at 40, 100, and 500 milliseconds.
maxDNA Configuration Tools allow the user to view the structuredetails and
connections at various levels to provideboth a “functional” representation of the
strategy (see figure1) and a highly detailed “schematic” representation showing
all available data (see figure 2).

54. Figure1 - Functional Representation of a Strategy
Pan and zoom capabilities are provided to facilitate focus on the portion of the
loop being investigated or configured. Drag and drop cursor controlis utilized as
well as line connection between algorithms as selected by the engineer. maxDNA
Configuration Tools also provides automatic cross referencing of algorithms and
signals plus direct access via a single keystroketo these cross referenced items.
Each and every control loop, signal, and algorithm can be annotated to enhance
understanding of the control strategy, uniqueI/O configurations, or existing plant
peculiarities. This information can be displayed on the CRT and / or printed on the
drawings. Diagnostic checks areintegrated into maxDNA Configuration Tools to
prevent errors such as connecting a logic signalto a modulating input or having an
inoperable configuration.
maxDNA Configuration Tools also allow the import and export of point databases
on either a systemor DPUbasis. During the engineering phase, the I/O database
is typically distributed to individual DPUs for security reasons. The database assigned to a
given DPU can then be accessed and connected to the control and data acquisition
strategies being developed for that DPU. In the plant the individual DPU
databases can likewise be converted to other formats such as Access™for use by
plant or headquarters personnel.
Once configured and enabled in the DPU, the loop configuration can be accessed
fromany systemmaxSTATIONand displayed on the CRT. This display provides all
process information in real time updated on the screen every second. Values are
displayed in engineering units or percentages as configured for that particular
variable. Logic signals are color coded for true or false.

55. Four levels of quality coding (good, bad, doubtful, and substitute) are provided for
each process signaland are propagated through out the controlstrategy. In
addition to normallogic overrides, individual algorithms can be configured to
execute desired strategies upon detection of undesired quality codes associated
with the input signals to that algorithm.
Figure2 - Detailed Representation of a Strategy
Hierarchical Structure
maxDNA Configuration Tools supporta hierarchical organization of control
objects. This arrangementallows for:
 Cut and paste of a branch of the hierarchy to replicate the configuration for
a piece of equipment
 Aggregate alarming – automatically created alarmstatistics such as the
number of high severity unacknowledged alarms in a branch of the control
hierarchy to animate graphics displays
 Group Alarm Acknowledge– single keystroketo acknowledgealarms in a
branch of the hierarchy
 IncrementalReload – incremental changes with NO effect on other
branches
 Inherited Characteristics – such as execution order and rate can be set for
each branch

56. Virtual and Real DPU
DPUs can be emulated in any maxSTATIONto facilitate debugging and
testing. Multiple engineers can work with different portions of the project
in parallel without impacting each other’s work. The output of each
engineer can then be combined and tested using the capabilities of the
virtual DPU.
Composite objects
maxDNA Configuration Tools supportthe creation of customcontrol
objects. A customcontrol object can be a loose collection of control blocks
in a group, or can be a fully tested template. Some features of composite
object management include:
 Controlled exposureof key parameters – the engineer can expose at the
composite block level attributes of blocks used to make up the object
 Controlled security of exposed parameters – the engineer can specify the
security level necessary to manipulate individual parameters
 User designated names for parameters – In01 of an AND gate can become
Oil PressureOk
 Locking – objects can be locked to prevent tampering
 Copy and paste – composite objects can be cut and pasted to speed
configuration
Documentation
Complete documentation of the DPU configuration is contained in the
DPU. This information can be accessed via the maxNET highway and
viewed live or uploaded to any engineer’s maxSTATIONon the system. In

57. the maxSTATION, theconfiguration can be captured as a Windows
Metafile Graphic in a “ .wmf” formatwhich can be viewed by Autocad or
Microsoftword. Fromthe maxSTATIONtheconfiguration can be copied to
a CD, printed via the systemprinter, or accessed by the corporate
engineering office. A differences programallows the comparison of DPU
configurations at severallevels to insure complete integrity of the
program. All discrepancies are tabulated for review and action.
On-Line DPU Interface
In an on-line system, the DPUprogramcan be modified at the following
incremental levels – individual variable, individual loop, branches of the
control hierarchy, or the entire DPU. This allows incremental changes
enhancing the integrity of the entire modification process by notrequiring
complete DPUdownloads for only small changes. The existing
configuration is uploaded to the engineer’s maxSTATION. Fromherethe
configuration is modified as necessary and then downloaded to the DPU.
In mostsystemarchitectures, the DPUs used for control are redundant.
One of the DPUs is kept as active, controlling the process, while the other
is set to the inactive mode.
The revised strategy is downloaded to the inactive DPU. Once
downloaded, the inactive DPUis activated and control is transferred to it.
By utilizing the freeze and unfreeze instructions, each individual output
whether modulating or binary can be compared with the state or value of
the field device and unfrozen if compatible or investigated if
uncompatible. In all cases the DPUwith the original or old strategy is now
the backup and can take over controlif there are any problems with the
new strategy. If the new configuration is working correctly, it can now be
transferred to the backup and the systemnow has a revised strategy
executing in a redundant configuration. Refer to figure3 for the
communication paths recommended to update a redundant DPU
configuration.

58. maxDNA Steam Turbine Control & Protection System
Summary
The maxDNA distributed steam turbine controlsystemis divided into two
partitions – one for controland the other for protection. Controlfunctions
include automatic startup and speed control, synchronization, load
control, frequency control and valvetesting. Protection functions include
monitoring critical turbine parameters, overspeed runbacks and tripping,
load rejection anticipation and trips for low hydraulic oil pressure, lubeoil
pressure, and vacuumpressure. Although separatepartitions, the system
is integrated into the maxDNA distributed power plant automation system.
Ituses the samecomponents and shares the same operator interface and
communication network. Itutilizes industry standard hardwareand

59. software.
Key Features
Separate, redundantcontroland protection functions – improvesplant
reliability and availability
Automatic speed control – faster, safer startups
Automatic load control – linearizescontrolvalve response and provides
smooth, faster load changes
Redundant 2-out-of-3 speed measurementand trip modules – protects
turbine from a single pointof failure
Programmed to operate turbine on designated valvepoints – improves unit
efficiency when in variable pressure mode
Plant constraintcoordinator – load changesat fastest allowablerate
Rotor stress calculations keep acceleration less than limits – increased
availability and longer life
Background& Introduction
Because the steamturbine is fundamental to the purposeof the power
plant its control systemmustbe extremely reliable, therefore redundant,
and highly responsive, to the extent that protective action is taken in
severalmilliseconds.
Turbine control systems haveevolved over the last forty years from
electro-mechanical systems, to analog electrohydraulic (EHC), to
proprietary based digital systems, to microprocessor based systems. The
subsequentadvancements havemirrored advancements in computer
technology - faster, more powerful, less expensive, less proprietary, more
flexible, etc.
Today, turbine control is an integral part of the plant automation system,
whosecomponents sharethe samecharacteristics, software, look and
feel. The turbine control is no longer a stand-alonesystem.
The advantages of a single integrated plant automation systeminclude:

60. Common operator interface
Integrated operations reporting
Reduced overall capital cost
Fewer types of spareparts
Simplified maintenance
Single interface to Automatic Dispatch System(ADS)
Common Coordinated Boiler-Turbine Control Operation
Flexibility – ease of expansion
Common tool set for configuration
Why modernize?
Many power plants are now over 20 years old, but never the less, they still
have great value to economically generate power. Modernizing these
plants has become a better alternative to building new generating
capacity, especially in a deregulated market. There are many plants still
successfully operating with the originally installed turbine control systems.
These aging control systems havebecome obsolete and are difficult to
operate and maintain.
Today’s electric power market requires increased availability, reliability
and efficiency. Modernizing the turbine controls can be one way to
achieve these goals. A modern distributed turbine controlsystemhas
many features that can provideimmediate results. Unfortunately it is still
sometimes difficult to quantify and justify the cost related to modernizing
an entire controlsystem. However, the modular nature of today’s modern
distributed controlsystems makes it possible to upgradein stages and
accrue advantages as features are added.
Common problems attributable to older turbine controls are:
Forced outages resulting in unplanned power purchases at much higher unit
cost
High costof preventive maintenance, usually from3rd party sources familiar
with older equipment
Difficulty getting spareparts
Additional mechanical stress during startup and overspeed conditions

61. Slow load changes and poor load following capability
No redundancy and/or subjectto single point of failure
Poor interface with DCS
Poor diagnostics
Modern integrated plant automation and information management
systems havegained wide acceptance for virtually every part of the power
plant. They are fault tolerant and provide high availability. The distributed
nature of these systems permits partitioning the turbine control, thus
providing a level of independence and security, while providing all the
advantages of an integrated system.
maxDNA Turbine Control
The systemhas two partitions, one for controland one for protection.
Redundant sets of Distributed Processing Units (DPU) are provided for
each partition.
Also, each partition has its own set of redundantAC/DC power supplies.
The redundant DPUs arein constantcommunication, thus providing the
backup unit with an up-to-date database. In the event of a fatal error in
the primary DPU, transfer to the backup DPUwill be automatic and
bumpless.
In addition, communication with the operator interface and other DPUs in
the systemis through a redundant high-speed network. All turbine data
and controlperformanceis available to all processing units in the plant
automation systemincluding reportgenerators, operator workstations,
historians and plant information management systems. Supervisory
systems, such as rotor stress calculations, automatic startup programs and
performancecalculations can also easily access the control systemover
the communication network. Note that the DPUs can operate without the
ability to communicate with operator workstations. This means the turbine
will be protected even if total plant communication should be lost.
Each partition has dedicated I/O modules to performspecific tasks. Each
control valvehas its own interface (valvepositioner) module. The valve
positioner has dual output channels and dual position feedback channels.

62. Itreceives demand signals over a high speed bus fromthe DPUand
executes its positioning routine every 5 ms. On-board diagnostics
periodically test and report on its health. A fatal error will resultin full
closureof the controlvalve in question.
The protection partition monitors the turbine for “overspeed” conditions.
Two speed measurement and tripping modules are used. Note that the
tripping function is executed in the I/O modules, not the DPU. This assures
overspeed detection and tripping will be executed as fastas possible. Each
module interrogates the same three speed signals. If two out of three are
greater than the trip point a contact closureis provided. Highestreliability
is assured becauseeither module can initiate a trip. This protects the
turbine froma single point of failure. Interrogation and execution of the
trip function takes less then 5 ms.
» Open Figure 1: maxDNA Turbine Control Systemto a new window
Note that the firstoverspeed condition causes all high-pressuresteam
control valves to be closed by opening the hydraulic fluid dump valves. The
reheat intercept valves are pulsed closed until the speed is broughtback
within acceptable range. At that point the main steam controlvalves are
opened and control is returned to normal. A second higher level overspeed
condition will causeall steam controlvalves to closeand the turbine to be
tripped.
In addition, the protection partition is also responsiblefor the following
other functions, which execute in the DPU:
Hydraulic oil pressurelow
Lube oil pressurelow
Vacuumpressurelow
Throttle pressurelow
HP cylinder temperature high

63. Load RejectionAnticipation
If electrical load is suddenly lost(main breaker open), the turbine power
and the braking torque of the generator are greatly mismatched. This will
causethe turbine to immediately accelerate. The protection partition
DPUs will close the controlvalves rapidly and reduce the load reference
setting to “houseload,” which will initiate the closing of the intercept
valves to minimize overspeed. The turbine will accelerate to a maximum
speed below the trip point. The reheater steam is then released at
approximately 102% of rated speed and single valve (full arc admission)
will be engaged.
The maxDNA systemincludes means to …
Accelerate the turbine to operating speed while providing variable rates of
acceleration
Transfer fromsingle valvecontrol to multivalve control (full arc to partial arc)
Control electrical load
Participate in load and frequency control
Test control valves while maintaining load

64. Overridethe normal valveposition signal to prevent the valve fromexceeding
a limit
In addition, the control systemis designed with ...
Individualvalvecontrol autonomy
Redundant controllers
High speed processing
Coordinated controlsystem(CCS) capability
SpeedControl
The maxDNA systemaccelerates the turbine from turning gear to
synchronous speed including transfer fromsinglevalve controlto
multivalve control. An automatic time vs speed programis provided to
assurea safeand faststartup. In addition, a rotor stress calculation
programmay be employed to ensurethe turbine will startup in the
minimum time with minimum stress. The operator has the ability to adjust
the speed reference and acceleration through any workstation.
Depending upon the turbine design, the unit is synchronized in singlevalve
(full arc admission) controlor sequential valvecontrol (partial arc
admission). The speed is trimmed by the systemuntil speed and phase
angle are matched with the line. (Means to close the circuit breaker are
the responsibility of the plant owner.) Note that the median of three speed
signals are used in the system.
Valve Management
The maxDNA systemprovides individualcontrol of all the steam admission
valves (main throttle or stop valves, controlor governor valves and the
intercept valves). Each valve has a different purposedepending upon the
mode of control. Sequential control of these valves during startup,
automatic load controland shutdown areperformed automatically by the
system. Switching controlmodes is automatic and bumpless.

65. During startup, when controlling speed, the throttle valve(typically a
bypass valvebuilt into one of the stop valves) controls steamflow. Under
these conditions the control/governor valves arewide open, thus allowing
steam admission to the entire nozzleblock. Depending upon the turbine
design, transfer to sequential control (controlvalves / governor valves)
takes place before or after synchronization.
At the transfer point the governor valves areclosed in sequence and the
throttle/stop bypass valvecontinues to controlsteam flow. When the
throttle bypass valvereaches its full open limit, controlis transferred to
the control(governor) valves thatthen open in sequence to increase speed
or load. All throttle/stop valves are opened to their limit at a controlled
rate.
When reducing load the reversetransfer occurs automatically at a preset
load point. On a rapid loss of load the transfer will take place after the
reheater has been unloaded.
Load Control
Load control, commonly called Automatic Generation Control (AGC), is
used after synchronization takes place and abovea preset low load limit.
The systemallows the operator to set the load reference in MW and the
rate of change or loading rate in MW per minute. The maxDNA systemwill
automatically control the governor valves to increase load in a linear
fashion which duplicates the load demand curveas established by the
operator or the Automatic Dispatch System(ADS).
Note that the maxDNA systememploys the Unit Constraint Coordinator,
which permits the operator to set the loading rate at a level higher than
most other systems.
Metso Automation employs a unique approach to AGC that uses turbine
firststage pressure(P1), grossgeneration (MW) and systemfrequency () in
a cascadecontrol loop. This controlloop has been proven over many years
to provide optimum performance, with or withouta coordinated control
system(CCS). Itis the same controlused in the D-E-B/400 CCS that has

66. been employed on over 900 fossilfired generating units worldwide. It
makes maximum use of boiler stored energy and linearizes the governor
valves. Figure3 shows typicalresponseto a load ramp in AGCmode. Note
that the AGC and valvemanagement algorithms are executed in the DPU
every 10 ms.
Figure3 - MW responsein AGCmode
Note figure4, which is a unit master display, provided for the operator to
set the load reference, loading rate and limits.

67. Figure4 - Unit Master Display
Frequency Correction
There are two elements to frequency control, sometimes called regulation
- the “natural” element provided by the turbine control (governor) and the
planned element provided by the Energy Management System(EMS). The
maxDNA turbine controlprovides for natural frequency correction
capability. Regulating capability is necessary for area wide frequency
control as well as systemwide control. Without frequency correction the
network would not be stable.
Regulation is the change in steady state speed expressed in percent of
rated speed when power output of the turbine is gradually reduced from
rated power to zero power output. It can also be stated as the percent
speed (frequency) changethat results froma full opening or closing of the
governor valves. Thus the greater the value of percent regulation, the less
will be the sensitivity.
% Regulation=[(S1-S2)/S2] X 100
S1 = Speedat zeroload
S2 = Speedat ratedload
Percent regulation is adjustableup to 10% with a nominal setting of 7%.
Frequency correction is used even when the unit is in coordinated control
mode.

68. Throttle PressureControl
There are circumstances when it is necessary to control pressurewith the
governor valves. This is normally referred to as turbine follow mode. In this
mode the valves respond to the throttle pressureerror by closing the
valves to increase pressureand vice versa.
Turbine follow mode is normally used when in an emergency condition
and it is important to immediately balance the boiler with the turbine. AGC
is suspended under these conditions. However, if Turbine Base mode is
available with the boiler control this can be initiated after boiler turbine
stability has been restored.
Turbine follow mode is automatically initiated when the throttle pressure
drops below a dangerously low limit. This is done to protect the turbine
fromwater induction.
Remote AutoPermits
Installations that havea foreign boiler control systemcan operate in
coordinated mode i.e. control the turbine in parallel with the boiler. The
maxDNA systemwill accept a demand signal via serialcommunication or
hard wired. A digital signal called “Remote Auto” is sent to the boiler
control as a permit for coordinated control.

70. The maxDNA turbine control systempositions the steam admission valves
by sending demand signals to servomotors(servos) mounted on or near
the hydraulic valveactuators. Hydraulic fluid is controlled to the spring-
loaded pistons by the servos. A maxPAC I/O module, called a “valve
positioner”, provides an analog output to the servo. Since mostservos
have two coils, dual outputs are provided.
The “valve-positioner” also has means to receive two valve position
feedback signals from LVDTs mounted on the valve. The positioning
algorithm uses the greater of the two signals. Since the LVDTs are
nonlinear and vary with temperature, means are provided to calibrate the
LVDTon a periodic basis.
A proportional-plus-integral(PI) positioning algorithmis executed every 5
ms. The position demand for each controlvalve is computed in the
Distributed Processing Unit (DPU) and updated over the I/O bus.

71. The “valve positioner” also has the capability to receive a speed signal,
which is transmitted to the DPUfor usein AGCmode.
The “valve positioner” has been designed with it’s own DINrail mounted
termination facility, which includes signalconditioning and a resistor
network for matching the coil to the proper output. A prefabricated cable
connects the module to the termination board.
Advantages of the maxPAC Valve Positioner:
Dual isolated outputs – operatesvalve even if one servo coil fails
Dual isolated position feedback channels (Uses the higher of the two signals) –
continued operation even if one LVDThas failed
Speed feedback signal for frequency control – AGC does notdepend upon
speed signals from protection partition
Detects if servo coil has failed (open or shorted) – providesonline alarm
withoutrequirementto take valve out of service
Detects stuck valve – alarm to operatorspermitsimmediate attention before a
total failure
Configurableoutput failure modes (resetor fail in place) – allows for keeping
valve in last position on fatalerror if desired.
On-line valvetesting and calibration of LVDT – can calibrate valve control
withouttaking controlout of service
High speed (<5 ms) processing speed – executes PI algorithm at maximum rate
Serial port for loading control algorithms and calibrating feedback signals –
Can be loaded and tested withoutthe engineering workstation
High resolution outputs (16 bits) – provides for accurate positioning controlof
valves and steam flow – results in accurate AGC.
Unit Constraint
Coordinator
One of the most significantchallenges to operators today is to provide
maximum responseto requests for a load change and not overstress aging
plant equipment. Caremust be taken to not put undo stress on
superheater headers, turbine rotors, reheatheaders, boiler drums, as well
as pumps, fans and valves.

72. During a load change the Plant Constraint Coordinator monitors critical
turbine and boiler parameters and will automatically reducethe unit-
loading rate if it is determined that excessivestress is likely to occur. When
the transientcondition clears and stress rates arereduced, the loading
rate is automatically returned to the original operator-adjusted setting
(See Unit Master station in Figure 4). The stress determination is
calculated in real time and is available for review by plant operators.
The Constraint Coordinator also monitors, in real time, the availability of
plant auxiliaries, such as fans, pumps, coalpulverizers, etc. it automatically
adjusts the maximum and minimum limits for load changes based upon
this availability.
Benefits of ConstraintCoordinator
Improveunitramping rate consistentwith instantaneous load changing
capabilities
Enable unit responseto ADS requirements
Operate with stress limits for extended life
Avoid purchased power costdue to slow load response
Extend life of auxiliaries and avoid unplanned outages
Hydraulic Equipment
Most turbines installed more then 25 years ago will havemechanical
hydraulic (MEH) or analog hydraulic (AEH) control systems. Hydraulic
supply systems arerelatively low, in somecases around 300 psig. In
addition, the valves arenot controlled on an individual basis, but by a set
of cams or a “gang bar” that opens and closes the governor valves in
sequence. Automatic operation of the valves is through a DC governor
motor that is used to set a counterbalancing force to hydraulic oil pressure
that drives the valve positioner. Also, in some cases the hydraulic fluid and
the lubricating oil are one in the same, which causes contamination with
metal particles.
Some of the problems:

73. Responsetimes are slow because of signaldelays
Use of mechanical levers and pinions responsiblefor errors and inaccuracies
over time
Governor motor, oil pump and controlunit all subjectto inaccuracies and non-
repeatability
High maintenance costs since there are many moving parts
Lack of spareparts for mostolder machines
Servicing is very difficult because of poor location
To providethe best overall performanceand availability it is
recommended that the hydraulic equipment be replaced, if not in the first
phaseof the modernization, but in subsequentphases. Equipment to be
installed is as follows:
Individualhigh pressurehydraulic actuators with high pressureoil supply
system
Servo positioners for each valve
Redundant LVDTposition feedback devices
Dump valves and accumulators..