BTG__DBR

Design Basis Report for BTG Mechanical Part

HPGC : 2 x 300 MW Deenbandhu Chhotu

Ram TPP, Yamunanagar

DOCUMENT NO.: 50-F248C-J01-01 Page 1

DOCUMENT CONTROL SHEET

PROJECT:DCR THERMAL POWER PROJECT

2 X 300 MW UNITS

CLIENT: RELIANCE ENERGY LIMITED/ SHANGHAI ELECTRIC (GROUP)

CORPORATION

DOCUMENT TITLE:DESIGN BASIS REPORT FOR BTG MECHANICAL PART

DOCUMENT NO.: 50-F248C-J01-01

REV. NO. : 1

ENDORSEMENTS

1 27/12/2

005

Revised as per

HPGC

comments

REV.

NO.

DATE DESCRIPTION PREP. BY

SIGN.(INITIAL)

REVW. BY

SIGN.(INITIAL)

APPD BY

SIGN.(INITIAL)

SOUTHWEST ELECTRIC POWER DESIGN INSTITUTE

18dongfengRoad,chengdu,China

Design Basis Report for Mechanical Part



DOCUMENT NO.: 50-F248C-J01-01 Page

2

CONTENTS

1 GENERAL.................................................................................................................................1 1.1 Major design principle.........................................................................1

1.2 Boiler…...............................................................................................2

1.2.1 Introduction......................................................................................2

1.2.2 Steam Drum , Furnace and Water-wall............................................3

1.2.3 Superheater, Reheater and Attemperator........................................8

1.2. 4 Economizer...................................................................................10

1.2. 5 Combustion equipment.................................................................11

1.2.6 Air Preheaters.................................................................................14

1.2.7 Boiler steel Structure, Platform and Stairs .....................................20

1.2.8 Casing, Refractory and Insulation..................................................21

1.2.9 Soot Blower System and Temperature Probe................................22

1.2.10 The Main Design Features of the boiler .......................................24

1.2. 11 Boiler unit anticipated performance ............................................26

1.2.12 Construction characteristics of boiler unit ....................................28

1.2.13 Piping system ..............................................................................30

1.3 Steam turbine with auxiliaries ...........................................................32

1.3.1 General ..........................................................................................32

1.3.2 Main component (per unit) ..............................................................33

1.3.3 Description for main components .................................................41

1.3.3.1 Combined HP/IP Turbine............................................................41

1.3.3.2 Double flow low pressure turbines ..............................................50

1.3.3.3 Gland Sealing System ................................................................59

1.3.3.4 Turbine Drain System .................................................................60

1.3.3.5 Exhaust Hood Spray System......................................................61

1.3.3.6 Bearings......................................................................................61

1.3.3.7 Rotor turning gear .................................................................62

1.3.3.8 Lubrication Oil System Introduction ......................................64

1.3.3.9 Lubrication Oil Supply System..................................................68





1.3.4 Turbine HBD..................................................................................90

1.4 Generator ..........................................................................................92

1.4.1 General ...........................................................................................92

1.4.2 Introduction of QFSN-300-2 generator ...........................................93

2 FUEL........................................................................................................109 2.1 Fuel characteristics.........................................................................110

2.1.1 Coal Analysis ................................................................................110

2.1.2 Fuel Oil ........................................................................................111

3 COMBUSTION SYSTEM AND SELECTION OF AUXILIARY EQUIPMENT............112 3.1 Boiler Fuel Consumption ................................................................113

3.2 Design principle of Flue gas and air system & pulverized coal system................113

3.3 System Description........................................................................113

3.3.1 Pulverized Coal System...............................................................113

3.3.2 Flue Gas and Air System..............................................................114

3.4 Calculation results .........................................................................118

3.4.1 Pulverized coal system .................................................................118

3.4.2 Flue gas and air system...............................................................119

3.5 Major Auxiliary Equipments Selection.............................................119

3.5.1 Pulverized coal system ................................................................120

3.5.2 Flue gas and air system...............................................................121

3.5.3 Boiler Igniting and Fire Stabilizing Oil System .............................129

4 THERMAL SYSTEM AND SELECTION OF AUXILIARY EQUIPMENT...130 4.1 Design principle of Thermal System ...............................................130

4.2 System Description.........................................................................130

4.2.1 Main steam, reheat steam and bypass system.............................130

4.2.2 Feed-water system ......................................................................135

4.2.3 Extraction steam system..............................................................139

4.2.4 Condensate water system ...........................................................139

4.2.5 Heater drains and vents system ..................................................140

4.2.6 Auxiliary steam system ................................................................141

4.2.7 Vacuum system ...........................................................................142





4.2.8 Condenser tube cleaning system.................................................143

4.2.9 Closed cycle DM water system.....................................................143

4.2.10 Boiler blowdown and drain system ............................................144

4.2.11 Steam turbine lube oil and Lube oil handling system.................145

4.2.12 Lubrication Oil System...............................................................145

4.3 Major Auxiliary Equipment Selection ..............................................149

4.3.1 Feed-water pump.........................................................................149

4.3.2 Heaters ........................................................................................154

4.3.3 Condensate extraction pump.......................................................167

4.3.4 Vacuum pump..............................................................................170

4.3.5 Condenser ....................................................................................172

4.4 Table of economic index..................................................................176

5 INSULATING MATERIAL.................................................................................176




DOCUMENT NO.: 50-F248C-J01-01 Page

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1 GENERAL

1.1 Major design principle

This project is designed to be the coal-fired power plant located in India, with

nominal generator output capacity of 2X300MW.

Main design basis codes and standards will be international codes &

standards, IBR or equivalent standards subject to owner’s approval as below

(refer to contract technical specification.)

1) American society of testing & materials;

2) ASME Test codes;

3) Technical code for designing fossil fuel power plant

4) Technical code for design of thermal power plant air & flue gas ducts/raw

coal & puliverizaed coal piping;

5) Code for design of thermal power plant steam/water piping.

6) Guaranteed availability of each unit is higher than 91%.

7) Unit start-up time from ignition to full load <7.5 Hr,<4 Hr, <1.5 Hr for Cold,

Warm and Hot start respectively.

8) Plant makeup water<3%.




DOCUMENT NO.: 50-F248-J01-01 Page

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9) The steam turbine, turbine generator and all equipments and auxiliaries are

suitable for continuous operation in the frequency range of 47.5Hz to 51.5Hz.

Also, for all equipments, noise level measured at a distance of 1 m from the

equipment will not exceed 85dBA except for places as mentioned in 1 to 3

below:

For HP & LP bypass valves and other intermittently operating control valves,

the noise level will be within 85 dBA

1) Safety valves and associated vent pipes for which it will not exceed 105

dBA;

2) Regulating drain valves for which it is limited to 90 dBA;

3) TG unit in which case it will not exceed 90 dBA;

1.2 Boiler

1.2.1 Introduction

The boiler is a natural circulation, subcritical pressure with single steam drum

and single reheat. It is semi outdoor arranged and has a single furnace of

reverse u-form (∏-type, Double pass) arrangement and full pendant steel

structure, dry bottom type water-cooled, balanced draft furnace and is

designed with tangential firing arrangement of burners. There are six

pulverizers with 24 coal nozzles in different elevations in the furnace zone of

the boiler. Light diesel oil will be used for start-up. The light diesel oil will be

designed for 10 % BMCR load and mechanical atomization. The steam

generator shall be designed for firing heavy fuel oil up to 30 % BMCR load.

The minimum load without oil support is 30 % BMCR with design coal and 40





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% BMCR with worst coal with two adjacent mill in service. The HFO will be

steam atomization.

Main superheater steam temperature will be controlled by two stage of spray

water attemperation and reheater steam temperature will be controlled by

tilting the burners and two stage spray water attemperation in case of

emergency condition.

All the designs will be in accordance with ASME “boiler and pressure vessel

code” and “National fire protection association code”

The design of steam generator pressure parts will meet or exceed all the

requirements of latest additions of IBR and specific approved of concerned in

the state Chief Inspector of Boiler. 1.2.2 Steam Drum , Furnace and Water-wall

Steam drum

Design pressure 19.81 Mpa(202kg/cm2g)

Number of supply one (1)

Inside diameter 1743 mm

Total Length 22000 mm

Material SA299

Water Separating System Turbo Separator, Corrugate Dryer





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And Drying Screen

Number of turbo separator 94 pcs

The drum will be of fusion welded construction fabricated form carbon steel

plate and equipped with two (2) 406.4mm diameter manholes. The inside

surface of the drum will be shop shot blasted leaving smooth, clean surface.

When the boiler is operated within the visible range of drum gauge glass,

standard steam quality and reliable water circulation is ensured.

Saturated steam is separated in drum from water/steam mixture of waterwall

and is led into superheater. Saturated water mixes with feeding water at the

bottom of drum from economizer outlet piping and continues to circulate.

Drum Internals

Necessary internals shall be provided for limiting the solid carryover in the

steam leaving the drum to that specified herein.

Drum Connections

The necessary welding end inlet and outlet connections and nozzles to

accommodate the required valves and accessories are provided for

connecting up piping for acid cleaning, nitrogen capping during boiler shut

down, hydrostatic test, chemical injection, continuous blowdown, sampling of

steam and water, emergency drain, safely valves and vent valves.

Drum Supports





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The necessary drum supports will be provided on both sides of the drum,

ample space provided for maintenance persons.

The design and manufacture of the drum conforms to ASME boiler and

pressure vessel code.

Water quality

Item Feed water Boiler water

PH @25 degC 9.2～9.4 9.2～9.4

Oxygen(O2) ppb < 7

Iron(Fe) ppb < 5

Copper(Cu) ppb < 1

Hydrazine(N2H4)ppb < 15 ppb

Silica(SiO2) ppb < 15 250

Cation Conductivity @25 degC 0.15 micro siemens / cm

Phosphate residual ,ppm 0.5 – 3 ppm

Salt, ppm < 20

Furnace and water wall

Type Water-cooled fusion welded wall, hopper bottom type

Furnace dimension:

Width 16100mm

Depth 14120 mm





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Height 53208 mm (lower water header to roof tube)

Volume 10426 m3

Net heat input per plan area 3.25 x 106 kcal/m2h

Furnace cooling factor – 147,200 kacl / hr – m2

Design press. ±660 mm H2O at 67% yield strength

Withstanding press ±1080 mmH2O

The membrane type construction for water wall is employed to ensure air

tightness of the furnace. The water distribution and heating of the water wall

tubes are uniform to ensure even steam production along the width of the

furnace and even water level along the full length of the drum. Sufficient

dynamic head is produced to prevent stagnation, reverse flow, unstable

hydrodynamic values etc. due to abnormal water circulation.

The boiler design ensure sufficient weight flow velocity in water wall tubes

under various loading to prevent departure from nucleate boiling (DNB). A part

of tubes with internal spirals are used (Rifle tubes).

When burning the coal specified in owner’s bid documents under all operating

conditions, the furnace design and burner arrangement ensure that no part of

water wall tube panels, superheaters and reheaters will be impinged by the

flame and no interference of flames between burners.

The boiler design shall ensure complete combustion and no detrimental

slagging in furnace and fouling in the superheater / reheater zone.





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The average flue gas temperature at the furnace exit under BMCR output of

the boiler is 1011℃ while the initial ash deformation temperature is equal to

1100 deg C. Flue gas temperature at the furnace exit is therefore lower than

initial ash deformation temperature by more than 60 deg C.

The design of the furnace employs balanced draft, and provides adequate

sustaining capability of explosion and implosion. The boiler has an expansion

center to permit free expansion of boiler parts. The thermal expansion of

water walls and main headers of other heating surfaces is indicated by three-

dimensional indicators.

The boiler roof employs gas-tight, all welded metallic construction, ensuring

the free expansion of various heating surfaces without cracking and leaking

under variable pressure operation.

The junctions of water wall and ash slag hopper employ qualified sealing

construction, ensuring the free expansion of water walls .in the sealing water

through effective washing equipment is provided to prevent ash accumulation

that affects expansion.

Doors and holes are installed to facilitate the operator’s inspection and the

access of maintenance personnel, and be able to withstand the thermal

radiation without deformation. During operation, these accesses are shut tight

and opening should be avoided. The clearance at the throat of ash hopper is

1400 mm. The hopper slope is 55 degrees, the water wall tubes near the

hopper and its supporting structure can withstand the impingement of large

clinker and sustain dead weight of an accumulation of clinkers up to the

lowest level of burners during abnormal conditions .





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The boiler employs suspended type construction. The steam/water pipes, flue

gas ducts and steel structure connected with the boiler proper ensure the free

thermal expansion of boiler water walls and the rear flue gas shaft.

1.2.3 Superheater, Reheater and Attemperator

Design criteria

Superheater and reheater tubes are made of seamless steel tubes, and

arranged in non-staggering pattern.

The superheater includes low temperature SH(1STstage SH),division

panel(2nd stage SH), SH platen ( 3rd stage ) and SH finish. The reheater

includes radiant RH(1st stage RH) , RH Platen ( 2nd stage) and high

temperature reheater finish (3rd stage RH).

Gas temperature and steam temperature unbalance along the width of the

furnace exit do not exceed the value, which causes metal temperature rise

exceeding allowable temperature.

The associated radiation with convection arrangement of superheaters and

reheaters produce good and flat load-steam temperature curves to relieve the

burden of temperature regulating devices .

In order to meet the requirements of steam temperature under various

working conditions during starting-up of steam turbine and to adapt the

variations of coal qualities, a two-stage water-spray attemperator is installed

before the inlet of division panel and inlet of final superheater. The spray

water system is designed for a spray quantity of 6% BMCR flow with all HP

heaters in service and maximum 10% BMCR flow with all HP heaters out of





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service while generating BMCR steam output.

The attemperator is installed in the steam pipe.

The average velocity of flue gas in superheater area will be： LTSH-9.6 m/s;

platen SH-7.1m/s; final SH-9.94m/s.

The reheater steam temperature will be normally controlled by tilting burners,

whereas the first water sprayer is arranged at the inlet of reheater for

emergency purposes and second water sprayer is arranged at between platen

and final reheater. The reheater spray water system is designed for 3% of

reheat steam flow. For quick cold/hot start up this unit also employs a bypass

starting up steam tapped off from the inlet of backpass lower wall header (S-

10、S-11、S-13,900898-E1-03) to HP heater emergency drain flash tank with

a capacity of 5%BMCR.

The control range of steam temperature is as follows.

Nominal steam temperature must be kept on 50-100%BMCR load for SH and

60-100%BMCR load for RH.

Heat resisting spacer tubes are employed for vertical suspended SH and RH

to guard against oscillation of tube panels.

Anti-abrasion plates made of stainless steel are provided on SH and RH tubes

within the effective range of soot blowers to protect the tubes from erosion.

The lower temperature superheater horizontal tubes are located in the boiler

rear shaft and is suspended from steam cooled water walls.





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Steam temperature deviation at the two ends of SH is lower than 5

Deg.C ,and RH is lower than 5 Deg.C.

1.2. 4 Economizer

Design criteria

Economizer tubes are made of seamless steel tube in non-staggering

arrangement. The net spacing between tubes of the economizer is 102mm,

the average flow velocity of flue gas in economizer at boiler BMCR load is

lower than 8m/s. The temperature difference of flue gas at left and right side

economizer is lower than 2 Deg.C.

Special attention for ash erosion protection will be paid for economizer design.

Anti-abrasion plates are installed on the upper rows of the economizer.

Baffle plates will be provided at adequate place to even out the gas velocity

distribution.

Protection plates will be provided on economizer within the effective range of

soot blowers to protect the tubes from erosion.

Tube nozzles and valves are provided for filling nitrogen and venting air.

Boiler water recirculation system with motorized stop valve provides for

protecting the economizer during starting up of the boiler.

A economizer recirculating piping is located between furnace downcomes

and economizer inlet header. Two motorized isolation valves are set on the

economizer re-circulation line. During boiler start-up, the motorized valve on





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the economizer recirculating piping must be opened to prevent water

evaporating in economizer, closing the motorized valve on the economizer

recirculating piping until certain continuous feed-water flow is established.

1.2. 5 Combustion equipment

Tilting tangential firing system

The tangential firing system is based on the concept of a single flame

envelope; both the fuel and air streams for each corner of the furnace are

aimed tangent to the circumference of a circle in the center of the furnace.

The resulting flame pattern forms a large swirl in the furnace.

Fuel and air nozzles tilt in unison to raise or lower the flame in the furnace to

control furnace heat absorption and heat absorption in the superheater and

reheater sections.

Wind box Assembles

Windbox assemblies are installed in each of the four corners . Each windbox

will be divided into several compartments numbered from the bottom to the

top housing pulverized coal burners, mechanical air atomized light oil burners,

steam atomized heavy fuel oil burners and strategically located auxiliary air

nozzles. The high energy arc (HEA) ignitors will be located in all elevations of

oil gun. They are of class 2 category as defined in NFPA code 85. The top

compartments are used to admit overfire air.

Air and fuel nozzle tilts





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The air and fuel streams are vertically adjustable by means of the movable

nozzle tips in each wind box compartment. The oil and auxiliary air

compartment nozzle tips can be tilted upward or downward through a total

angle of approximately 60degrees (30degrees up, 30degrees down). The coal

compartment nozzle tips can be tilted upward or downward through a total

angle of 40degree (20degrees up, 20degrees down) when operated in parallel

mode.

Offset concentric firing concept

The pulverized coal streams are opposite from auxiliary streams in offset

concentric firing. When fired in this manner, the pulverized coal streams

entering the furnace are introduced in a direction counter to the rotation of the

auxiliary streams. As the fuel and air are essentially in opposed stream the

mixing between them is highly turbulent substantially increasing the ability of

the coal to completely combust before exiting the furnace.

In addition there is a benefit by directing the auxiliary air toward the water

walls, the fuel-rich combustion zone is confined to the center of the furnace,

this maintains an oxidizing atmosphere along the water walls, thereby

minimizing slag formation and corrosion.

The other advantage is that the counter rotationally injected flue also result in

a reduction on the flue gas angular momentum in the upper furnace, hence

improving the furnace exit plan side-to-side gas flow imbalance.

Wide range coal nozzle design

The wide range coal nozzle assembly is the advance design for improving

ignition stability throughout a greater load range and can be made to achieve

a low load operation while maintaining a stable coal flame without the use of





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support fuels on tangential fired boiler. This unique design works by inducing

both turbulence and recirculation to the discharging coal/air mixture. As a

result, the coal particles ignite and provide stability local to the coal nozzle tip

discharge.

Each assembly consists of a coal nozzle tip similar in appearance to the

standard coal nozzle/nozzle tip design. The wide range coal nozzles contain

an internal horizontal splitter plate, which separates the coal/air mixture into

fuel-rich and lean streams.

This ensures that the proper air to fuel ratios required for combustion are

available over a greater range of pulverizer operation.

The wide range coal nozzle tips differ from the standard design by

incorporating an irregular “V-” shaped bluff body diffuser. The diffuser

produces a lower pressure zone, which induces turbulence and causes a high

recirculation pattern to form. The trailing edge of the bluff body is equipped

with a raised surface which shears the coal/air stream in the furnace

increasing the fuel eddy formation into a recircrulation zone .It is these

features which enhance the formation of the stable ignition point over a wide

range of unit load.

Low NOx Coal Burners

There are two methods for controlling NOx emission in this coal burners .one

of them, as described above, the overfire air (OFA) is the remaining auxiliary

air that is introduced to the furnace through OFA ports located at the top of

the windbox, another is the offset concentric firing system (CFS), both OFA

and CFS can be referred to as “staging” techniques. OFA is a type of “vertical

staging” for controlling emissions, while CFS can be thought of as a





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“horizontal staging ”technique-unique to tangential firing .The CFS and OFA

retard the conversion of fuel bound nitrogen at different times during the

combustion history of coal particle within the furnace, thereby the low NOx

coal burners can control NOx emissions not more than 260 gms per gigajoule.

Light Oil Burners and High Energy Arc (HEA)

The 4 numbers light oil burners located at the bottom elevation are the wide-

range mechanical atomizing type with air operated retractable mechanisms. ,

will be provided to maintain 10% percent BMCR load. The oil gun is a double-

barreled gun; the inner barrel supplies oil to the atomizer and the outer barrel

conveys the fuel oil away from the atomizer.

The minimum turndown ratio is 4:1 without changing the size of the burner tips.

The boiler load can be controlled automatically while maintaining good

combustion conditions.

When the atomizer is withdrawn completely from the burner, the fuel oil is to

be automatically shutoff. The safety shutoff valve is to be arranged so that it is

not possible to remove the atomizer.

Without first shutoff the fuel, a quick automatic closing valve, solenoid

operated, is to be provided in the oil supply line to each burner arranged to

shutoff the supply of oil to the unit on flame failure, draft failure, low oil

pressure or low drum water level, or any cause of master fuel trip.

The 4 numbers high engrgy arc(HEA )ignitors will ignite the light oil burners..

1.2.6 Air Preheaters

Ljungstorm trisector air preheater separates both primary and secondary air

flow from one another .The new type double sealing structure reduces direct





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radial and axial air leakage. In addition, the hot end radial sealing of air

preheater adopts leakage control system (LCS) which can automatically

approximate and control the radial sealing clearance, that permits effectively

to reduce the air leakage.

(1) General technical data

Number of supply Two (2)

Type Regenerative vertical

Shaft type

Size 2- 29-VI (65 deg) – 84(96) inch

Heat transfer surface

(Hot end) Carbon steel

(Intermediate sections) Corten (equivalent ASTM A588 or ASTM A606)

(Cold end) Low alloy Corten steel

The rate of air leakage on BMCR is less than 6% and after one year of

operation will be less than 7%.

Scope of supply per air preheater

*Driving mechanism including speed reducer and motor

*Auxiliary motor drive





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* Air motor drive

*Infrared detection system

*Two stationary water-washing devices

*Two additional stationary water-washing devices for fire fighting

*Modular rotor

*Corrosion-resistant steel for cold end protection

*Radial circumferential and axial seals including automatic leakage control

system

*Observation ports and light

*Bearing with oil circulation system

*Rotor stoppage alarm

*Six (6) access doors

Description of equipment for air preheater

(a) Heat transfer surface

The heat transfer surface supplied will consist of hot end element fabricated

from carbon steel, hot intermediate element fabricated from Corten

(equivalent ASTM A588 or ASTM A606), and cold end element fabricated





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from low alloy corrosion resistant steel. . The element will be in easy-to-handle

baskets and shipped from the point of manufacture in the rotor modules .The

element will be sprayed with a water-soluble rust inhibiting oil prior to

shipment. Module covers will be supplied for protection during storage. The

hot end and hot intermediate baskets will be arranged for removal through the

ductwork adjacent to the air preheater .The cold end baskets supplied will be

arranged for side removal through a door in the side of the air preheater

housing structure.

The rotor and the air heating elements of the air heater will be constructed to

allow a feature increase in the depth of the elements at the hot end is 300mm.

(b) Driving mechanism including speed reducer with main drive and auxiliary

drive the main drive consists of a drive motor, coupling, speed reducer and

pinion gear. This system drives the rotor through a pin rack mounted on the

periphery of the rotor.

The auxiliary drive insures the continued operation of the air preheater if

power to the main drive motor is interrupted. The auxiliary drive may also be

used to control the speed of the rotor during water washing of the heat

transfer surface and also for maintenance of the rotor seals and heat transfer

surface

(c) Bearings

The air preheater rotor is supported by a self-aligning thrust bearing assembly

capable of accepting horizontal loads. The air preheater rotor is guided at the

top of the rotor by a spherical roller bearing .All bearings are lubricated by an

oil bath .An oil circulation system for filtering and cooling the oil is supplied for

both the support and guide ends of the air preheater.





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(d) Two stationary water-washing devices

Each device consists of a straight pipe with spray nozzles spaced to distribute

wash water, evenly over the heat transfer surface. One pipe is located in the

gas inlet duct and one is in the gas outlet duct. These devices are integral with

the furnished air preheater and strainers. These devices are to be used for

normal washing of the air preheater.

(e) Two additional stationary water-washing devices

Two additional stationary water washing devices which can be used as part of

deluge system are included.

(f) Automatic leakage control system (LCS)

An automatically adjustable sealing surface is incorporated into the hot end

sealing system. This unit will include a movable sealing surface, a drive

system and a rotor position sensor for each sector plate and a control

package.

The automatically controlled system minimizes the direct air-to gas leakage at

the hot end of the air preheater during transient and full-load operation

conditions .The system keeps the sealing surface of the sector plate in close

proximity to the rotating sealing members.

(g) Rotor stoppage alarm

This device will be comprised of vanes, mounting brackets, and electrical

components.





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The alarm device, i. e. annunciator is to be provided.

(h) Infrared detection system

A three-head infrared detection system is included for each air preheater.

Modular rotor design

A modular rotor design will provide a maximum amount of shop assembly

which will minimize field welding .with a modular rotor, the structural welds

required on the rotor at erection are limited to the pin rack installation. The

heat transfer surface will be shipped in the modules ,reducing the time

required to assemble the rotor in the field.

(j) Observation ports and light

One glass-faced observation port and vapor proof light are included for

installation in the air inlet duct ,adjacent to the air preheater, the location of

these components is determined in the field to best suit viewing of the cold

end heat transfer surface. An additional glass-faced observation ports is

included for installation in the air outlet duct at a point best suited for viewing

the hot end heat transfer surface. These items are shipped unattached for the

installation in the field .

(k) Six (6) access doors

Six access doors for installation in air and gas ducts are included, three (3)

are located integral with the hot end connecting plate and three are shipped

loose for field installation in the cold end duck work.





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1.2.7 Boiler steel Structure, Platform and Stairs

Boiler steel structure mainly includes: supports to each vertical planes,

horizontal supports, supporting plane on boiler roof, each floor platform,

walkways, stairs and other needed supporting structures.

The vertical supporting plane consists of steel columns and bracing between

columns, arranged along the boiler depth and width direction respectively. Some rows are arranged respectively at the front, middle and rear parts along

the furnace depth direction. Some are arranged respectively at the both sides

along the boiler width direction.

The seismic effect, wind load and other horizontal loads will at last be

transferred to the boiler steel structure foundation through vertical support.

The horizontal support consists of beam and bar supports, the rigid plane

consist of seven tiers which are arranged respectively at altitude of the boiler.

They are important parts to transfer horizontal force to fix and control the

boiler expansion direction, guarantee the rigidity of the boiler steel structure

and maintain the steel structure stability.

The supporting and suspending plane on boiler roof consists of the roof steel

frame, supporting and suspending plane for pressure parts and roof

superheater tube supports. The supporting and suspending plane for pressure

parts is made up of double paneled bar beams. Boiler heating surface is

suspended under this plane. Roof steel frame consists of ceiling beam which

is main beam, secondary beam and plane supports forming a rigid plane.

Roof supports mainly consist of beam and bar supports, which is to maintain





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the stability of the main beam.

Steel structure of boiler house

Permanent enclosures will be supplied to give protection against the weather

for plant and personnel in areas where considered necessary e.g. drum,

burner, and galleries.

Platforms, walkways and stairs

All walkways and stairs will be constructed and provided and will be supported

entirely from frames and steelwork. Checkered plating of 5mm thickness will

provided in front of each burner.

Two (2) sets of stairs and walkways are provided for the boiler on each

side .They are to extend from the ground level to the highest part of the

units .Walkways are also provided along the front and rear of the unit as

necessary.

1.2.8 Casing, Refractory and Insulation

The casing made of aluminum material is divided into kinds of ribbed panel

and flat sheet. The installer shall furnish all the necessary labors, tools,

scaffolding, ladders, and some odd scraps of material required to install the

casing. The installer shall field fabricate some element that do not determine

for dimension in the works. The casing drawings do not indicate every small

fabrication detail of the casing, it is up to the casing installer to take care of

the installation in these areas to the satisfaction.

Surface temperature higher than 60 ℃ will be insulated for the protection of





22

personnel. Thickness of the insulation will be determined by the material used

and that the surface temperature will not exceed 60 deg C at an ambient

temperature of 40℃

Aluminum sheets (stucco pattern embossed) will be employed to protect the

insulation layer; the thickness of aluminum sheets will be 1mm for the boiler,

and for equipment and ductwork. Piping lagging shall be 0.5 mm for

application up to 330 mm OD and 0.6 mm on other applications.

1.2.9 Soot Blower System and Temperature Probe

The boiler will be provided with a complete set of a programmable automatic

sequential steam operated sootblowing equipment for cleaning the furnace

waterwall, superheater, reheater, economizer and air heater while boiler is in

operation.

The sootblowing system will include the following .

Steam and drain piping system including valves, fitting, supports, steam

pressure reducing valve and thermal drain valve .

A microprocessor based programmable type controller with color CRT monitor

and operator keyboard.

Sootblower

Wall deslagger

Long retractable sootblower





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AH sootblower

Temperature probe

Retractable furnace temperature probe with approximate travel of 6 meters

complete with totally enclosed motor, limit switches, position transmitters and

position indicator, remote control switches, local push-button station.

Soot-blowing piping and air preheater soot-blowing piping. Manual stop valve

and motorized stop valve are set before pressure reducing valve and safety

valve.

The steam of sootblower system come from panel SH outlet header for boiler

soot blowing and from platen SH outlet header for AH soot blowing flowing

through pressure reducing valve, is divided into two branches to enter boiler

proper is set behind pressure reducing valve in order to protect whole soot-

blowing system from exceeding pressure. Pressure measuring point is set to

control the pressure behind pressure reducing valve.

To guarantee the proper dryness of soot-blowing media, there is a drain

system for two branches of boiler proper individually. Each drain system has a

motorized valve self-drain, and its horizontal piping shall at least be kept

gradient for drainage.

Air pre-heater soot-blowing steam consists of two branches, one is from

pressure reduce station for above 10% BMCR load, and the other is from

auxiliary steam for below 10% BMCR load.

A drain system with a pneumatic valve in piping is able to self-drain.

Horizontal piping shall at least be kept gradient drainage.





24

1.2.10 The Main Design Features of the boiler

Firing

Burners are arranged at the four corners of furnace for tangential firing, wide

range (WR) tilting burners are utilized, which feature for wide adaptability to

various coals , complete combustion, effective reduction of NOx formation.

The tilting nozzles are designed to regulate the furnace exit temperature,

which provides an auxiliary means to regulate the reheat steam temperature.

The coal preparation system employs a pressurized direct-fired circulating

system with HP mill with high primary air (PA) pressure and low secondary air

(SA) pressure. The coal pipes are installed with orifice to balance the flow of

air/coal mixture to ensure uniform coal –air flow at four corners.

* Water Circulation

This boiler is designed for natural circulation. The minimum circulation ratio is

2.6 under any operating condition. As the drum is designed with large volume,

the boiler can adapt to the load variations easily. The waterwall is constructed

with rifled tube on proper location to increase safety allowance control.

The boiler is equipped with furnace safeguard supervisory system (FSSS),

which provide functions including controlling the purges of the pulverized

system in /out of operation, detecting the fireball in furnace and the flame of

individual oil gun, offering the trip protection in emergent case of fuel failure.

Therefore, FSSS ensures the boiler unit operating safely and reliably.

The turbine – boiler coordinated control system (CCS) also control the





25

following items including firing, the exit temperature of pulverizers and the air

flow, the primary air flow, the deviation-limit of fuel and air flow, the secondary

air flow, the furnace draft, the feed water flow, the superheat steam

temperature and the reheat steam temperature. Consequently, CCS ensures

the turbine-boiler operating in a coordinated fashion and helps to improve the

operation.

In addition, the following systems are used; programmable sootblowing

control system, boiler water level/furnace flame CCTV monitoring system,

which improve the operation of the boiler unit.

Flue and Air System

The boiler is designed with a balance draft system by using FD and ID fans.

The air required for combustion in the boiler is supplied by FD fans to the air

preheater of trisector design. The pressurized primary air system acts as the

drying agent and primary air for the HP mill direct –fired system .The primary

air system is designed with a bypass, used to regulate the air/coal mixture

temperature. The secondary air from air preheater outlet is discharged to the

boiler windbox to provide secondary air for the burners

The flue gas from furnace outlet will pass through the panel-and platen-type

superheaters, high-temperature superheater, high-temperature reheater and

the deflection chamber (over the arch nose), low –temperature superheater,

economizer, air preheater. Then the flue gas will pass through the ESP before

being discharged to the stack by ID fan.

Piping system

The piping system mainly consists of the piping for drain, discharge blowdown,





26

vent, steam discharge and chemical dosing etc.

The piping system also includes a 5% BMCR drain system for bypass of

saturated steam from backpass lower wall header to HP heater emergency

drain flash tank, which can control the superheat steam temperature

effectively, quicken startup speed, and improve the operation flexibility.

The drum emergency drain system can prevent the drum from being fully filled

with water.

The safety valve discharge system with silencer can control the steam

discharging noise within acceptable level.

1.2. 11 Boiler unit anticipated performance

Boiler Max. Continuous Rating (BMCR)

The boiler can adapt to the design coal and worst coal. When fired with design

coal and under rated load ranges the steam temperature at the rated value

are :

For superheater steam between 50- 100% load range, the steam temperature

imbalance ±5℃

For reheat steam between 60-100% load range, the steam temperature

imbalance ±5℃

The boiler is designed to carry base load and can also be used for cycling

operation .





27

Boiler operation

*The boiler can accommodate for combined sliding –pressure (fixed-sliding –

fixed pressure) operation.

*The boiler can accommodate for various start-up/shutdown operation

patterns of the turbine. The boiler can be started up in cold, warm, hot and

extremely hot conditions.

*With normal startup, the time duration needed for the unit to carry full load

from the ignition are:

Cold startup <7.5 hr

Warm startup <4 hr

Hot startup <1.5 hr

Allowable boiler load change rate

Fixed pressure operation 5%/min

Siding pressure operation 3%/min

Air leakage rate of air preheater

Within the first year of boiler operation 6%

After the first year of boiler operation 7%





28

Low Nox combustion technology is being incorporated in the design of furnace

and coal burners.

NOx emission 260 gm /gigajoules

Service life

*The main pressure parts of the boiler are designed for a service life not less

than 30 years .

The boiler can stand for the following expected number of annual start-ups:

Cold startup: 20 times. (after 72 hours of unit shutdown.)

Warm startup: 40 times (after 36 hours of unit shutdown)

Hot startup: 180 times (after 8 hours of unit shutdown)

1.2.12 Construction characteristics of boiler unit

*The boiler is designed for semi-outdoor arrangement provided with rainproof

measures as light metal house cover over the furnace roof. *The boiler utilized

complete pendant steel structure, which provides space for all the

components to expand freely when heated.

*The boiler is designed with an expansion center, from which the components

will expand in order. This is conducive for stress analysis and seal design of

pressure parts and can help prevent pressure parts and seal parts from

tearing due to excess thermal stress, thus to improve boiler safety and





29

reliability.

*Using fully sealed internal casing

In order to prevent boiler unit from gas-and air-leakage, all the areas without

gas –tight membrane heating surfaces are fully sealed by internal casings,

absolutely reliable expansion joints and special sealing structure on the

furnace roof penetration, which provide the unit with great safety and

economy.

Design Basis:

1) Such parameters of pressure, temperature and flow etc. for main steam

and reheat steam will match those required for steam turbine.

2) Boiler nameplate, namely Max. Continuous Rating (BMCR) is higher than

steam flow at valves wide open (VWO) of steam turbine.

3) Boiler capacity and main parameters

Boiler type: SG1025/17.5-M898

Items Unit BMCR

Boiler Max. Continuous rating (BMCR) t/h 1025

Superheater outlet steam pressure MPa.(a) 17.6

Superheater outlet steam temperature ° C 541

Reheat steam flow t/h 822.7

Reheater inlet steam pressure Mpa(a) 3.84





30

Items Unit BMCR

Reheater outlet steam pressure Mpa(a) 3.66

Reheater inlet steam temperature ℃ 326

Reheater outlet steam temperature ℃ 541

Economizer inlet feed water temperature ℃ 280

1.2.13 Piping system

1.2.13.1 Drain, vent and chemical Injection piping

To ensure the safety and reliability for boiler operation, drain and vent point

are set at necessary position of pressure parts.

The position of chemical feed is located on downcomes.

The piping system also includes a 5% BMCR drain system for bypass of

saturated steam from lower header in the second pass to the HP emergency

drain flash tank, which can control the superheater steam temperature

effectively, quicken startup speed, and improve the operation flexibility.

The drum emergency drain system can prevent the drum from being fully filled

with water.

1.2.13.2 Blow-down piping With improvement of steam parameter, higher purity feed-water is required.

Boiler blow-down system is used for controlling boiler water concentration and





31

removing sediment. Under condition of high solid content and worse treated

feed-water, periodical blow-down is carried out be furnace lower water drum.

Under condition of good feeding water quality, it is generally recommended to

use continuous blow-down if water/steam quality requirement can be met, and

periodic blow-down isn’t needed.

1.2.13.3 Sampling piping Boiler is fitted with saturated steam and boiler water sampling points.

Saturated steam sampling is taken from steam relief tubes between drum and

roof SH inlet header. Six (6) points of saturated steam sampling are set along

the drum length direction.

Furnace water sampling is taken from continuous blow-down piping, one (1)

point is set, sampling piping is equipped with two (2) manual stop valves.

1.2.13.4 Safety valve and discharging piping for safety valve In order to ensure the boiler operation safety and to prevent pressure parts

from overpressure, boiler is equipped with ten (10) safety valves, of which

three (3) are on drum, two (2) are on SH outlet, two (2) are on RH inlet piping,

three (3) are on RH outlet piping. In addition, two (2) pneumatic control valves,.

Two （2）Pressure sensed pneumatic relief valves are arranged on SH outlet

piping. Total relief capacity of pneumatic control valves is more than 15% max.

main steam flow.

Each safety valve and pneumatic vent valve is fitted with discharging piping,

going upward from upper of drip pan at discharging bent of safety valve and

passing through roof housing. In order to reduce noise, each safety valve and

pneumatic pressure controlled valve is equipped with silencer.

The safety valve discharge system with silencer can control the steam





32

discharging noise within acceptable level.

1.3 Steam turbine with auxiliaries

1.3.1 General

The steam turbine will be of a tandem compound, single reheat, and axial flow

type with steam exhausting from one double flow low-pressure cylinder to

condenser.

The unit will be capable of producing rated output of 300mw when operating

with rated steam conditions and design ambient conditions.

Main specification

Type: Subcritical, Reheat, Tandem compound, Two cylinder, Double flow,

Condensing

Rated Power (TMCR Condition): 300MW

Rated Speed: 3000r/min

Direction of Rotation: Clockwise viewing from Governing End

Steam Inlet Pressure: 16.7MPa(a)

STEAM INLET TEMPERATURE 538℃

STEAM REHEAT TEMPERATURE538℃





33

REGENERATIVE 3H+1D+4L

CONDENSER PRESSURE: 10.05 KPa (a)

FREQUENCY RANGE FOR CONTINUIUS OPERATION: 47.5-51.5HZ

FINAL FEED WATER TEMPERATURE: 275.8℃

LAST STAGE BLADE SENGTH 905mm

ROTOR:

NUMBER 2

TYPE SOLID FORGED TYPE

COUPLING RIGID COUPLED WITH BOLT

CASING: 2 NUMBER , CAST TYPE

1.3.2 Main component (per unit)

One (1) complete combined HP-IP steam turbine.

One (1) complete double flow LP turbine with bottom exhaust.

One (1) set of cross-over piping

Control and protective valve systems including the following.





34

A) separate mounted steam chests with two(2) stop-throttle valves and six(6)

governing control valves, each including:

1) Servo-actuator

2) Electrical contacts at each end of each stop-throttle valve

3) Provision for testing while unit is in operation

4) Removable temporary fine mesh and permanent heavy mesh strainers for

each stop-throttle valve

B) Flexible inlet piping between the steam chests and HP turbine casing.

C) Two (2) reheat stop valves and two (2) interceptor valves, each including.

*Actuator

*Electrical contacts at each end of each valve mechanism

*Provision for testing while unit is in operation

*Removable temporary fine mesh &permanent heavy mesh strainers.

D) Piping between interceptor valves and intermediate pressure Turbine

Digital Electrohydraulic (DEH) control system

Emergency trip system including:





35

A) Mechanical hydraulic overspeed trip with oil test gauge for local manual

overspeed trip test.

B) Emergency trip system with local and remote testability including:

1) Trip control block

2) Low bearing oil test block

3) Low EH fluid pressure test block

4) Low condenser vacuum test block

5) Electrical overspeed sensing

6)Thrust bearing trip device

7) ETS controller cabinet

8) Operator/test panel

9) Remote operator/test panel

10) High pressure hydraulic fluid supply system which include:

A) Fluid reservoir

B) Fluid supply system components mounted at the reservoir and consisting

of:





36

1) AC motor driven variable displacement pumps

2) Suction strainers and pump discharge filters

3) Relief valve

4) Check valve

5) Heat exchangers

6) Appropriate gauges, pressure transmitters, pressure switches

thermometers, thermocouples, and flow meters.

C) Hydraulic high and low pressure accumulators

D) Suitable interlocks and alarms

E) All interconnecting piping between the fluid supply system and the

actuators, stainless steel tubing and manifolds will be used where applicable.

F) Fluid transfer pump

G) Fuller’s earth fluid conditioning unit

Complete lubricating oil system which include:

A) Main oil pump on turbine shaft

B) Oil reservoir of sufficient operating capacity

1) Float-type oil level indicator





37

2) High and low level alarm device

3) Top-mounted relief and access doors

4) AC motor driven bearing oil pump

5) DC motor driven Emergency oil pump

6) Oil Ejector

7) Motor-operated vapor extractors

8) Oil strainers located at each motor-driven pump and Oil Ejector suction

and at the oil return to the reservoir

9) AC motor driven seal oil backup pump

C) Twin full-size oil coolers with Interconnecting oil piping and a manual

three-way valve

D) Pressure switches with test valves for automatic starting of the bearing oil

pumps and emergency oil pump

E) Complete interconnecting oil piping to and from all bearings ,oil reservoir

and oil coolers .pressure oil piping in high temperature areas will be guarded

F) Oil demister and exhaust head

G) Bearing lift system for LP bearing





38

Gland sealing system ,consisting of the following :

A) Steam sealed glands

B) Pneumatically operated gland steam regulators

C) Manual shutoff and bypass valves for high pressure regulator

D) Manual shutoff and bypass valves for the spill-over regulator

E) Manual shutoff valve for the cold reheat regulator

F) Surface-type gland steam condenser

G) Low pressure desuperheater system

H) Steam seal piping from the regulators to the turbine and from the turbine

to the gland condenser.

I) Gland header relief valve

Turbine drain system including air-operated drain valves and piping from

Exhaust hood spray system including nozzles, piping, pressure switch and

pneumatic-operated control valve for the low-pressure turbine element

Motor-operated rotor turning gear

Protective devices, consisting of the following

A) Turbine exhaust casing relief diaphragms





39

B) Exhaust casing high temperature alarm thermocouple

C) Loss of vacuum

D) Loss of governing fluid pressure

E) Low lube oil pressure

Turbine supervisory instruments consisting of following:

A) Recording type

1) Turbine rotor eccentricity

2) Turbine rotor vibration

3) Turbine rotor position

4) Turbine casing expansion

5) Turbine casing and rotor differential expansion

6) Speed and governor valve position

7) Steam and metal temperatures for turbine operation

B) Vibration phase angle meter and selector switch

C) Instantaneous eccentricity run-out indicator





40

D) Supervisory indicating panel with lights for alarm signals

Thermocouples consisting of the following:

A) For measurement of turbine steam and metal temperatures for the

purpose of turbine operation

B) For thrust bearing

C) For journal bearings (metal)

D) For each main bearing oil drain

E) For the thrust bearing oil drain

F) For the oil inlet and outlet of the oil coolers

Thermometers, consisting of the following:

A) For each main bearing drain

B) For the thrust bearing drain

C) For the oil inlet and outlet of the oil coolers

Pressure gauges mounted on the equipment ,or loose for purchase is

mounting, for the following

A) Bearing header

B) Main oil pump suction





41

C) Main and backup bearing oil pump discharge

D) Emergency bearing oil pump discharge

Miscellaneous instruments, consisting of the following:

A) Electric transmitter for steam seal pressure

B) Electric transmitter for inlet steam pressure

C) Electric transmitter for reheat steam pressure

D) Pressure gauge for the gland exhauster vacuum

Set of lifting gear and special tools and wrenches

Leveling wedges ,seating and soleplates

1.3.3 Description for main components 1.3.3.1 Combined HP/IP Turbine

The combined HP-IP turbine design is based on the latest in design

technologies.

The major design features included are high efficiency reaction blade and

rugged inlet features with low maintenance valves.

The HP-IP turbine is housed in an enclosure which helps reduce the noise

level in the power plant. The enclosure has access doors to allow operating

personnel to enter the enclosure and inspect the HP-IP turbine during





42

operation. Large grated openings in the enclosure top provide ventilation. The

enclosure is constructed in several sections, which are mated together to from

the complete enclosure. During turbine maintenance periods, sections of the

enclosure can be removed as needed to provide crane access over the

turbines.

The HP-IP turbine has an outer cylinder made up of two sections joined at the

horizontal centerline. The outer cylinder provides structural support for the HP

and IP section internal stationary components.

The outer cylinder base provides support for the stationary turbine parts .,the

outer cylinder cover can be removed for access to internal parts. The

horizontal joint is a precision-machined surface area on both the cover and

base .the surfaces are bolted together without a gasket to form a metal-to –

metal steam-tight joint

DESIGN FEATURES/BENEFITS

Optimized HP&IP Blade path

The HP and IP blade paths are optimized for each application. This results in

the most efficient blade path for the available space that meets the

mechanical requirements. Many recent advances in blade path design have

been incorporated into this element. The efficiency enhancements

incorporated into the reaction path include:

Overall blade path thermodynamic optimization

Enhanced airfoil design

Improved aerodynamic analysis





43

Enhanced sealing

Integral shroud blade for IP

Reduced windage losses and secondary –flow losses

Operating flexibility

This turbine design incorporates into a single unit, the capability for a wide

range of operation strategies. The unit is capable of operating efficiently in

sequential, single, or hybrid valve mode of operation. The turbine is capable of

either two-shift, load follow or some combination of these operating strategies

Components description

The outer cylinder is suspended on two support paws at each end. The

support paws rest on pedestals that transfer the turbine weight to the building

foundation. Large studs through the support paws help keep the turbine from

lifting off the pedestals but allow longitudinal and transverse movement for

thermal expansion. The HP-IP turbine expands about 25mm from the cold to

the hot condition.

The turbine rotor extends through the outer cylinder housing at both ends of

the turbine and gland-sealing system prevents steam leakage into the turbine

room

The rotor is supported on bearings in the pedestal housing at the governor

end and in the bearing house of LP outer cylinder at the generator end

Blade path design





44

The HP and IP blade paths are optimized for each application using advanced

high efficiency reaction blade. This results in the most efficient blade path for

the available space that meets our mechanical requirements. The design

process uses new concepts to reduce pressure losses both externally and

internally to the turbine elements. The work split between the control stage

and the reaction blade path have been optimized to maximize overall HP

component efficiency.

HP Rotating Blades

The HP rotating blades will be of the grouped shrouded design. The excellent

mechanical performance of this design results directly from the smaller mass

and the related lower stress levels of the HP blades. The lighter mass, the

thinner shroud and the reduced tip velocity due to the shorter length relative to

the IP blades combine to virtually eliminate tenon creep in HP blade. This

design also assures obtaining the necessary damping effect of shroud contact

which is of a concern in the HP application of integral shroud T-root blades.

The HP blades use “T” blade root design because of its inherent lower steam

leakage characteristics. This is important in the HP blade path where

pressures are higher relative to the IP blade path.

IP Rotating blades

Each integral shroud IP rotating blade is machined from a single piece of

metal.

The elimination of separate shrouds significantly reduces vibratory stress,

high cycle fatigue and the stress concentrations that can be created by riveted

IP tenons. The centrifugal loads created by the massive shroud are now

distributed across the entire cross section of the blade.





45

The tips of IP blades in the first stage of the intermediate pressure turbine

must withstand both centrifugal forces and bending forces while operating in

high temperature reheated steam. Those forces which can create creep in the

blade material are not prevalent in HP blades because their shorter length

reduces blade tip velocity. The potential for creep in the integral shroud blades

is significantly less because the maximum steady stress at the intersection of

the shroud and airfoil is reduced by 67% compared to a riveted IP blade tenon.

The improved IP blade design also promotes contact between the shrouds of

adjacent blades ,alleviating vibratory deflection. At the same time, all blades

are designed so that the first mode frequency is above the sixth harmonic.

Full-scale laboratory testing conclusively demonstrated that the vibratory

stresses in the integral shroud IP blade design are 50% lower than those in an

IP riveted blade. The integral shroud IP blade design offers one other

significant advantage: the blades operate with maximum reliability. Because

there are no concealed surfaces, the blades can be thoroughly inspected with

greater ease.

Removable “contoured end wall” nozzle blocks

The nozzle blocks are made from a forged ring using Electro discharge

machining (EDM) to create the nozzle vanes with a contoured end wall .The

contoured end wall minimizes secondary flow (steam swirl), reducing the

secondary flow and turning the flow before it is accelerated greatly reduces

the potential for steam erosion in the nozzle blocks.

HP-IP Rotor

The HP-IP rotor is a CrMoV alloy forged rotor without center bore.The finite

element analysis indicates that rotor creep strength is much low ,so the life of





46

rotor is prolonged.

Rotor steeple design

The rugged rotor uses two proven designs to secure the rotating blades: the

“T” root design is used in the HP, and the multiple serration side entry root

design is used in the IP. Both designs have proven to be highly reliable for

their respective applications.

The riveted shroud “T” blade root that is being used in the HP permits more

efficient use of the available area for blade on the rotor, the grouped riveted

shroud design is the best combination for a “T” root has the added advantage

of providing better sealing under high pressure conditions, eliminating

efficiency losses that result from steam leaking through a side entry root.

Stationary blades

All stationary blades feature the twisted blade design. This design offers

substantial efficiency gains over the older designs because the proper foil

orientation is maintained over the entire height of the blade rather than only at

the mean diameter. The use of twisted stationary blades allows the use of

parallel sided rotating blades with minimum incidence .The twisted blades are

both stronger and more efficient than previous. By varying the gauging of the

stationary blade, the stage reactions are more uniform from the base to the tip.

Additionally the increased reaction at base in conjunction with the reduced

reaction at the blade tip reduces secondary blades

Twisted stationary blades are most frequently used in low-pressure turbine

because of the sizable difference between the base and tip velocities. When

fuel prices were low ,the use of twisted stationary blades in HP/IP turbines





47

was difficult to justify economically. Today high fuel prices and improved

manufacturing processes make the extensive use of twisted stationary blades

in the HP/IP section very cost effective

Rotor balance provisions

The rotor has provisions for balance holes at six locations. three locations are

for factory balance and three are for field balance of the rotor . At each field

balance location, there is a series of equally spaced holes for balance plugs

for rotor balancing . The factory balance locations are drilled only if needed to

remove metal to balance the rotor , Before shipping ,the rotor is balanced in

the factory at operating speed . Therefore, the rotor should need only

minimum touchup balance at initial installation

Rotor thrust balance

All pressure forces that could cause a turbine component to move in the axial

direction are called thrust forces. Thrust forces are produced by the pressure

drops as the steam moves through the blade path. These axial pressure drops

exert thrust forces on the rotating parts. Thrust forces on rotating parts

attempt to move the rotor in the direction of steam flow.

The HP-IP turbine is an asymmetrical, opposed-flow element. Steam passes

first over one set of blades ,then another in series . This causes thrust forces

in opposite directions in the HP and IP sections of the rotor.

The two opposing forces acting on the rotor cancel each other if the two are

equal .If one force is greater, the difference between the two is the resultant

thrust force on the rotor toward the lower opposing force. Several features are

included in the turbine design to help control and balance the opposing thrust

forces as closely as possible.





48

The following major features are provided to help balance the various

opposing thrust

Rotor thrust balance pistons (areas)

Pressure equalizing flow passages

Thrust bearing

The first two features allow use of a relatively small thrust bearing for the

turbine generator

Rotor thrust balance pistons

The two major sources of thrust forces on the rotor are the HP blade area and

the IP blade area .To balance the thrust forces on both sets of blade, the rotor

body is designed with certain opposing areas of known cross section exposed

to known pressures.

These areas provide a predictable force to resist or help balance the thrust in

the blade path. Such an area generally can be thought of as a balance

piston .The forces acting on it are similar to those in a piston engine.

The HP-IP rotor has three balance pistons that are integral parts of the rotor,

The diameter of each of the three balance pistons is sized so that most of the

axial thrust is balance out. Generally, the thrust is balanced when the

diameters of the balance pistons are nearly equal to the average diameters of

the corresponding blade groups.





49

The rotor balance pistons are subjected to the same pressure differentials as

the sections they balance. The HP and IP blade paths are independently

balanced by their own dummies (thrust pistons ) opposing the blade path .The

HP blade thrust is balanced out by the HP balance piston .The IP blade thrust

is balanced out by IP balance pistons . Buildup of excessive deposits in the

turbine could eventually affect this balance of opposing forces.

Pressure equalizing flow passages

To provide the correct balancing forces, balancing areas must be subjected to

the same pressure differentials as the sections they balance .Three pressure

equalizing passages allow this to occur in the turbine.

One pressure equalizing passage is actually the HP impulse chamber. Here,

the control –stage exit pressure becomes the inlet pressure for the HP blade

path and HP balance piston.

The second pressure equaling passage consists of two equilibrium pipes

these pipes connect the IP exhaust area at the generator end of the turbine

and the cavity between the HP exhaust dummy ring and the inner gland at the

governor end. The equilibrium pipes are routed outside the outer cylinder and

equalize the pressure on both ends of the rotor .

Outer cylinder

The outer cylinder of the HP-IP turbine is constructed in two parts (cover and

base). The base of the outer cylinder supports the entire HP-IP turbine

cylinder and it is larger than the cover .The outer cylinder is not only a

structural support and housing but also a pressure vessel subjected to steam

pressures and thermal loads





50

Steam turbine cylinders have widely varying zone temperatures, so metal

temperature gradients between zones also vary widely. The outer cylinder is

covered with insulation to help reduce heat loss and to help minimize radial

temperature gradients.

The HP-IP outer cylinder provides structural support for the HP&IP blades

rings, HP-IP and HP exhaust glands

The HP-IP turbine has inner and outer glands at both the governor end

generator end of the outer cylinder .The glands confine the steam in the

turbine and prevent steam leakage to the atmosphere and air leakage into

turbine.

Thermocouples

Turbine temperatures are measured by thermocouples. The thermocouples

are installed in special protecting tubes that penetrate the cylinder wall and

welded to the cylinder .The HP-IP cylinder is manufactured with thermocouple

wells installed at standard locations on the turbine, based on the history of

turbine temperature monitoring needs .

1.3.3.2 Double flow low pressure turbines

The LP turbine element is of a double-flow design .The primary design

features of this design include lashing blades ,integral shroud blades ,and a

mono block rotor forging ,this turbine element is capable of frequency

operation up to 50Hz+1.5,-2.5Hz,continuous high load operation up to

backpressures of 5.5”HgA and cyclic operation up to 10000 start –up/stop

cycles





51

Design features and benefits

Fully integral monoblock rotor body

Benefits :

*No disk-to –shaft inter faces

*No shrunk –on coupling

*Cyclic duty capability

*Complete system torsional and dynamic stability analysis and compatibility

High efficiency integral shrouded blades: benefits:

·Improved efficiency

·Cyclic duty capability of over 10000 cycles

·Reduced maintenance through elimination of rivets and tenons

·Increased inspection intervals

Lower blade excitation high efficiency blading of last three stages: benefits :

·Improved efficiency

·Cyclic duty capability of over10000 cycles

·Reduced maintenance through elimination of rivets and shroud





52

·Capability of operation at up to 5.5in Hg backpressure.

·Enhanced corrosion resistance

Main components description

Rotor and steeple designs

The rugged fossil LP turbine rotor has low operating stresses and has integral

couplings .This design allows for rugged one – piece blade in combination

with low stress steeple designs

This rotor strength provides greater resistance to stress corrosion cracking

one-piece rugged blade reduces the vibratory load transfer to rotor steeples

and also help eliminate steeple high cycle fatigue.

Side entry blade roots are used for attaching all of the rotating blade. This

design maximizes the contact area between the blade root and rotor steeple

and minimizes stresses in both the rotor steeple and blade root serration .The

large blades have curved roots whereas, the small blades have straight roots .

The side entry steeple is located above the bulk lf the rotor body, thereby,

steeple thermal transient stresses are reduced rotor stress concentrations at

the steeples have been significantly reduced through an effective steeple

contour developed through finite element analysis.

LP Rotor Forging Manufacture

LP rotor forgings are made of 3.5%NiCrMoV alloy steel having high impact





53

strength.

Inlet flow guide

The inlet flow guide is a cylindrical component located at the center of the

turbine and consists of 180 segments. This construction allows easy assembly

and minimizes thermal stresses .The inlet flow guide improves the turbine

efficiency by reducing inlet pressure drop and leakage losses across the first

row of stationary blades. Steam leakage is minimized by zero-leakage spring-

back seals at the governor and generator ends.

Exhaust flow guides

Each LP turbine has exhaust flow guides, one at the governor end of the inner

cylinder and one at the generator end, each exhaust flow guide is constructed

in two halves .The halves form a complete ring when installed to the inner

cylinder structure .The flow guide is designed to utilize the velocity leaving the

last row blade to experience a pressure recovery .this will allow the steam to

expand to a pressured bellow the condenser pressure and the blade to

generate additional work .

LP outer cylinder

The LP turbine rotor is housed in an outer cylinder, which functions as an

airtight containment vessel. The carbon steel outer cylinder structure provides

support for the LP turbine inner components and transfers the loading to the

foundation .The outer cylinder’s main function is to convey the exhaust flow, at

nearly ideal vacuum conditions from the last row blade to the condenser as

efficiently as possible .It is designed to withstand normal and emergency

structural loads without undergoing deflections great enough to disturb the





54

running clearances. The outer cylinder is composed of two parts-the outer

cylinder cover and the outer cylinder base .Because of the large size of the LP

turbine, the outer cylinder cover and base are each made in sections to

meet ,transportation limitations .The segments are joined at vertical and

horizontal joints to made a steam-tight unit .

The outer cylinder base includes a support foot structure on all sides .The

support foot rests on seating plates, which are grouted on the foundation. The

bottom of support foot which rests on the seating plates, is the turbine

baseline, the top of the support foot structure is the turbine horizontal

joint .The base structure below the support foot acts as the exhaust opening

for the LP turbine .The fabricated-steel structure has a minimum of internal

support braces, to help limit disturbance in the flow path and allow smoother

flow through the structure.

Two pads on each side of the outer cylinder base structure support the inner

cylinder and related stationary turbine parts

The fabricated-steel outer cylinder cover can be removed for access to

internal turbine parts for maintenance. Each outer cover also has four

manholes, two on each side, to allow access for internal inspection without

removing the cover.

The turbine is protected from overpressure by two breakable diaphragms in

the end sections of the outer cylinder cover. These diaphragms are designed

to rupture if the pressure in the outer cylinder reaches 0.34 to 0.55bar (5to

8psig).

LP Inner Cylinder.





55

The inner cylinder provides the support structure along the blade path for the

inlet flow guide, stationary blades and exhaust flow guides .The inner cylinder

consist of cover and base sections bolted together at the horizontal joint.

The fabricated LP inner cylinder is designed using the experience and

information gained from continual application of the latest technology and

design techniques which specifically address the issues of cycling, moisture

and hard particle erosion and reliability.

Three-dimensional finite element analysis is used as an integral part of the

design process, an example of which is shown below.

Three-dimensional finite element analysis has allowed design engineers, by

using more accurate calculation of stresses, to quantify the deflections that

the inner cylinder experience during various transient events. This allows for

structural streamlining of the inner cylinder design which eliminates the

negative aspects of differential thermal expansion .It also allows more

accurate prediction of thermal gradients and their effect on cylinder

stresses .The overall benefits of this design process include improved LP

reliability, maintainability. and efficiency .The LP inner cylinder is fabricated

out of carbon steel plate

The inner cylinder is structurally optimized to eliminate the potential for

cylinder distortion, and joint and bolt distress caused by thermal expansion

and contraction .The fabricated design improves the fatigue life of the inner

cylinder because of the appropriately sized cylinder walls .The fabricated

design also provides the correct amount of flexibility to better accommodate

thermal transients

Rotor glands





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The rotor glands at the governor and generator end of LP turbine are alike.

They are bolted to the outer cylinder to seal the rotor openings .The glands

are part of the gland steam sealing system, which maintains the correct

sealing steam flow to the glands and helps keep air out of, and main steam in,

the turbine. Each rotor gland consists of a gland base, gland cover, four seal

ring retainers, four seal rings and the support keys ,screws ,and dowels

needed to assemble the major parts .

Rotor balance provisions

The rotor has balance provisions in the form of three drilled and tapped

balance planes and two separate drill balances .The drilled and tapped planes

are located at the ends and center of the rotor. Each end of the rotor has a

drill plane. Shop balance is completed using the three drill and tapped balance

planes .A minimum number of balance plugs is always used for each plane .

Excess balance corrections are made by drilling .The drill and tap planes are

designed with sufficient balance capability to permit the normal shop balance

while reserving additional field balance capability .Access holes in the outer

cylinder allow balance plugs to be installed in the field in the two ends of the

rotor ,when required .A record of all balance plugs installed or removed from

the rotor must be kept throughout the service life of each rotor .

Stationary blade

Stationary blade upstream of the L-1stage are of the welded diaphragm type

configuration. The L-0 and L-1 stationary rows are a segmental type

construction.





57

Diaphragm blade is inherently easier to install and maintain than the existing

riveted shrouded blade .The existing stationary design uses individual

stationary blades fitted one by one into the blade ring grooves. These blades

are then shrouded and riveted and caulked into place .In contrast, a half ring

diaphragm assembly is simply slid into the blade ring and locked. Should

maintenance be necessary, the diaphragm assembly can be easily removed

and serviced.

Blade path sealing

In the Rugged design ,leakage loss is reduced considerably .STC has used

two blade path sealing features to improve long-term efficiency .

Honey comb seals

Honeycomb seals are installed over all freestanding blades, (except over the

last stage which utilizes and exhaust flow guide) .STC has a broad experience

base with this design .The individual honeycomb cells collect moisture which

is removed by annular grooves in the backing rings. This type of seal

enhances the moisture removal capability in the blade path.

Springback seals

Springback seals are be used in the stages upstream. They reduce the

potential for hard seal rubs, therefore, seal clearances are maintained and

long term efficiency is enhanced .

Crossover pipe adapter

The crossover pipe adapter extends from the steam inlet opening of inner





58

cylinder to the crossover pipe. The cross over pipe adapter is bolted directly to

the steam inlet flange of inner cylinder

Erosion resistant design features

Operating experience has proven that moisture droplet and hard particle

erosion of LP turbine blades adversely affects thermal performance and unit

availability due to increased maintenance requirements. While it is recognized

that moisture and hard particle induced erosion cannot always be entirely

avoided, STC fully understands this phenomena and has incorporated design

features in the blade path to minimize its effects .Thus ,in an effort to increase

unit availability and sustain unit thermal performance ,STC has enhanced the

erosion resistance of the LP turbine by including the following erosion

resistant features :

1) Addition of Moisture Collectors Throughout The Blade Path.

This feature reduces the amount of moisture available for impingement on

rotating and stationary components

2) Protection of L-0 R Blades (last stage blades in LP cylinder) With Stellite

Shields, use of stellite shields on a blade in leading edge has proven to be the

most off frequency operation.

The primary operating consideration of an LP turbine under load at either

greater or less than normal system frequency is the protection of the long

tuned blade so that harmonic resonance do not occur .In the design

verification process, great care is taken to properly tune the tapered and

twisted blades that constitute the last several LP stages.The result of our

improved manufacturing techniques ,combined with our more rugged tuned





59

blades is a greater off frequency capability.

1.3.3.3 Gland Sealing System

The function of the rotor gland sealing steam system is to prevent the leakage

of air into or steam out of the turbine cylinders along the rotor and valve stems.

The system consists of the following major components:

Gland condenser

Safety valves

Desuperheaters

Steam strainers

Interconnecting piping

The regulating valves supplied for this system consist of HP gland steam

supply, Cold reheat steam supply and spillover to condenser. During lower

loads, sealing steam is controlled by the Cold Reheat gland steam-regulating

valve. Finally, at higher turbine loads, pressure in the gland steam system is

controlled by the Spillover regulating valve.

The gland condenser is a surface type heat exchanger of shell and tube

construction .It prevents the escape of sealing steam to atmosphere from the

HP, IP and LP turbines by condensing the steam that leaks off from the zone

between the air seal and outermost steam seal of each steam gland of the

turbine .The condenser also helps to seal the main steam valve stems by





60

maintaining a slight vacuum at the valve stems. Condensate is circulated

through the tubes to condense the gland and valve stem leak off steam. After

almost all the steam is condensed, air, noncondensible vapors and any

uncondensed water vapor are removed by an air exhauster mounted on the

gland condenser .

A desuperheater is used to lower the temperature of the steam required for

sealing the LP turbine glands. The desuperheater consists of a reduced

diameter pipe section into which a spray nozzle has been inserted .The flow of

cooling water is controlled at the spray nozzle by a diaphragm control valve

responsive to an air signal from a temperature controller which senses the

temperature at one of the LP glands.

Two safety valves are required in the gland sealing system to prevent the

occurrence of excessive pressure .The safety valve is a direct pressure

actuated relieving valve characterized by pop action.

Steam strainers are mounted in each of the gland steam supply pipes for the

HP, IP and LP turbines .the strainers are positioned to filter the steam

supplied to the turbine glands.

1.3.3.4 Turbine Drain System

The function of the drain system is to prevent ingress of water into the turbine

and the safe removal of water from steam turbine .The system consist of air-

operated drain valves and drain piping .The drain valves for the turbine are

mounted directly in the drain piping of the following drains :

Main Steam inlet Drains

HP-IP Cylinder Drains





61

Reheat steam inlet drains

All these drains are opened or closed by air-operated drain valves that are

automatically or manually controlled by the operator .On loss of supply air

resulting from shutdown, trip, or loss of electrical signal to the solenoid valve

in the supply line, the drain valves are arranged to open to protect the turbine.

1.3.3.5 Exhaust Hood Spray System

High exhaust temperature of LP turbine must be avoided to minimize chances

of contact between stationary and rotating parts from thermal distortion or

excessive differential expansion. Such contact above turning gear speed can

cause serious damage resulting in forced or extended outages. The exhaust

hood spray system is turned on automatically as the rotor speed reached

2600 rpm. The spray turns off automatically at approximately 10-15% rated

load. The exhaust hood spray system consist of an exhausted hood spray

control station that supplies condensate to nozzles mounted two exhaust flow

guide assemblies for the LP turbine.

1.3.3.6 Bearings

The HP-IP turbine bearings are of the four-tilt-pad design, the LP turbine

bearings are of the sleeve design. These bearings are inherently stable and

are not susceptible to oil whip. All bearings area self-aligning type designed to

withstand loads transmitted in both normal and unusual opening condition.

Thrust bearing will be flexible pad type (Kingsbury). The thrust bearing is

installed in an adjustable housing which allows the axial position the rotor

adjusted during maintenance outages.





62

1.3.3.7 Rotor turning gear The rotor turning gear is used to rotate the rotor at a low speed while the

turbine is shut down, so as to reduce a minimum the distortion of the rotor due

to uneven cooling of the turbine parts. In general, it is recommended that the

turning gear be used continuously during shut down periods. Its use will vary,

depending upon the size and type of turbine and the local operating conditions.

In general, it is recommended that the turning gear be used continuously

during shut down periods. If the shutdown period is to be of long duration ,the

turning gear should be operated for a sufficient period to prevent distortion

before the rotor is brought to rest.

In every case, the turning gear should be operated for a short time before

starting the turbine with steam. The best procedure for any particular unit can

be determined only by actual operating experience and the shaft deflection

shown by the truth indicators.

The turning gear motor mounted on the housing is so connected through

gears and pinions to the pinion that it is capable of turning the rotor at a speed

of approximately 3 rpm.

Its principle parts are the motor, the train of gears and pinions to reduce the

speed and the engaging lever with the necessary linkage for engaging and

disengaging the pinion with the coupling spacer ring. Turning Gear can be

engaged and disengaged automatically and manually.

To Engage the Automatic Turning Gear

1） When the Turbine is Being Shut Down

Turn the control switch to the automatic turning gear position to initiate the

automatic sequence. The control switch is normally left in this position





63

thereafter.

With the control switch in the " Auto" position and when the speed of the rotor

decreases to approximately 200 rpm, the automatic sequence circuit will be

activated, thereby supplying sufficient lubricating oil to the turning gear. When

the rotor comes to rest the pressure switches shown in the " Zero Speed

Indicator" leaflet will close. The air supply valves will be energized and engage

air will be supplied to the engaging mechanism.

With the engage air on, the air cylinder will move the turning gear lever un-

til tooth contact is made between the pinion and the coupling spacer. At this

point the operating lever will stop moving, however, the air cylinder will

continue to move and compress the spring of the elastic link. This will operate

the switch, starting the turning gear motor. If the pinion is not fully engaged it

will slip one tooth and become engaged.

Following engagement, the rotor will turn at turning gear speed, which will

cause the zero speed indicator pressure switches to open and shut off the

engage air. The unit is now ready for extended turning gear operation.

To Disengage the Automatic Turning Gear

2） When the Turbine is Being Started Up

As the speed of the rotor increases above the speed of the turning gear, the

pinion will be disengaged automatically.

As the operating lever is moving toward the disengaged position, the switch

will close and disengage air will be supplied to insure total disengagement.

When the operating lever reaches the total disengaged position, a limit switch





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will shut off both the turning gear motor and the disengage air. After a speed

rise of approximately 200 rpm,the automatic sequence will be deactivated, to

isolate the turning gear from operation and shut off the turning gear lubricating

oil. All turning gear operations will then be complete.

The "Control Circuit" is capable of being transferred from " Automatic" to "

Manual" during any phase of the operation.

1.3.3.8 Lubrication Oil System Introduction

The Lubrication Oil System furnished for this unit provides two backup

sources of seal oil for the hydrogen seal oil system; provides a medium for

operation of the mechanical overspeed trip device; and provides oil to

lubricate the turbine and generator bearings, the thrust bearing, and the

turning gear. The system consists of several major components listed below.

1.3.3.8.1 Lubrication Oil Reservoir

The lubrication oil reservoir is a large carbon steel tank in which the lubrication

oil is stored. The reservoir is usually located below the centerline of the

turbine-generator unit. From the reservoir, the oil pumps furnish the required

amounts of oil to satisfy the various oil requirements ,and since the lubrication

system is a closed system, all oils returned to the reservoir. Mounted on the

top of the reservoir are the auxiliary motor driven pumps, vapor extraction

system, terminal box, heaters, level alarms, etc. Inside the reservoir, the

piping connects the discharges of the various pumps to the appropriate oil

header supply piping. Check valves prevent backflows from the system. An oil

ejector mounted below the oil level in the main oil pump discharge piping,

utilizes high pressure oil to pick up oil from the reservoir when the unit is

operating at or near rated speed. Strainers on the oil ejector intake, the

bearing oil pump suction, and in the return piping help to keep contaminants





65

out of the system. The reservoir is provided with access openings in the top

and with a drain in the bottom.

1.3.3.8.2 Main Oil Pump

The main oil pump is a volute type, centrifugal pump mounted on the turbine

rotor in the governor pedestal. It has a large capacity and a stable discharge

head. It has a large capacity and a stable discharge head. At or near rated

turbine speed, the main oil pump supplies all the oil requirements of the

lubrication system, and in addition, provides two sources of back up for the

hydrogen seal oil system of the generator. The main oil pump is not self-

priming and must constantly be supplied with oil under pressure. During

starting and shutdown periods, this is done by the auxiliary oil pumps. At or

near rated speed, priming oil is supplied by the oil ejector as described in the

leaflet covering of the lubrication oil supply system. The main oil pump

discharge is piped back into the reservoir where it is connected to the oil

ejector, inlet and to the HP Seal Oil Backup Header from which the

Mechanical overspend and Manual Trip Header is orificed.

1.3.3.8.3 Auxiliary Oil Pumps

The bearing oil pump is an AC motor driven, vertical pump mounted on top of

the reservoir. It is used during start-up and shut-down procedures and also

serves as a backup to the main oil pump during contingency conditions. It is

capable of supplying all the LP seal oil backup and bearing oil requirements.

During normal operation at rated speed, the bearing oil pump is off and the

main oil pump supplies all of the oil requirements. The bearing oil pump is

controlled by a pressure switch that senses the bearing oil pressure. If the

bearing oil pressure decreases to 0.77-0. 84bar(g) such as occurs during a

shutdown or contingency condition the bearing oil pump will turn on and bring

the pressure back up to requirements. However the pump will not

automatically shut off on rising pressure and must be turned off manually from





66

the control. During start-up procedures the bearing oil pump is put into service

before the unit goes on turning gear and is not taken out of service until the

main 0il pump is capable of satisfying all of the oil requirements

(approximately 90% of rated speed).

The emergency oil pump is identical in construction and operation to the

bearing oil pump except that it is operated by a DC motor powered by station

batteries, and the controlling pressure switch' s set point is below the set point

of the pressure switch which controls the bearing oil pump. During start-up

procedures the emergency oil pump is put into service after the bearing oil

pump establishes sufficient bearing oil pressure. The emergency oil pump' s

control switch is then set on "Automatic," and the pump will turn on if the

bearing oil pressure decreases to 0.70-0.77bar(g). Thus, the emergency oil

pump serves as a backup to the bearing oil pump and is the final backup to

the bearing oil system. The station batteries are sized to provide sufficient

power to operate the pump during a normal coast down, and it is imperative

that the batteries are kept sufficiently charged to maintain this capability.

CAUTION: An insufficient charge on the batteries may not allow the

emergency oil pump to operate properly thereby resulting in an insufficient

supply of lubricating oil to the bearings. This will result in serious damage to

the bearings, journals, and associated components.

The seal oil backup pump is an AC motor driven, horizontal pump mounted on

top of the reservoir. It provides oil to the HP Seal Oil Backup Header and is,

used anytime the main oil pump cannot satisfy the HP seal oil requirements,

including the requirements of the Mechanical Overspeed and Manual Trip

Header. During normal operation at rated speed ,the seal oil backup pump :is

off, and the main oil pump supplies all of the oil requirements. The seal oil

backup pump is controlled by the same pressure switch that controls the





67

bearing oil pump by monitoring the bearing oil pressure. If the bearing oil

pressure decreases to 0. 70- 0. 77bar (g) such as occurs during a shut-down

or contingency condition, the seal oil backup pump automatically starts and

brings the HP Seal Oil Backup Header up to the required pressure. The pump

will not stop on rising pressure, however, and must be turned off manually

from the control room. During start-up procedures the seal oil backup pump is

put into service before the unit is started and should not be taken out of

service until the main oil pump is capable of satisfying all of the oil

requirements (approximately 90% of rated speed). A relief valve in the

discharge piping prevents overpressures.

1.3.3.8.4 Jacking Oil System

The bearing jacking oil system, which is used during a turbine start-up or

shutdown, prevents turbine damage and ensures a smooth transition to

turning gear operation.

1.3.3.8.5 Oil Coolers

The temperature of the lubrication oil is regulated by the oil coolers. Two oil

coolers are normally provided. Under normal operating conditions, one is in

use and the other is on a standby status ;although in some special conditions,

both coolers may be in service simultaneously. The coolers are connected to

the discharge sides of both the bearing oil pump and the oil ejector; thus the

bearing oil, no matter what the source, passes through the coolers before

flowing to the bearings. The oil is circulated within the oil cooler shell around

the tube bundles while the cooling water passes through the tubes. The oil

flow to the coolers is controlled by a manually operated three-way valve which

directs the flow to either cooler and permits switching coolers without

interrupting the flow of oil to the bearings. The oil inlets to the coolers are

connected through a crossover pipe and an interchange valve which permits

the inactive cooler to be filled with oil and ready for immediate operation. The





68

flow of water to the coolers is adjustable by means of a manually operated

valve in the water supply liner hence the temperature of the oil leaving the

coolers is also adjustable. The valve is normally adjusted to provide an oil

temperature of 60℃. 43℃-49℃ measured at the oil cooler discharge.

1.3.3.8.6 Emergency Trip Functions

Lubrication oil is used as the control medium for the interface-diaphragm valve.

Mounted on the governor pedestal the interface-diaphragm valve provides an

interface between the mechanical overspeed and manual trip portion of the

lubrication oil system and the autostop emergency trip portion of the control

system. Lubrication oil from the Mechanical overspeed and Manual Trip

Header supplied to the diaphragm valve acts to overcome a spring ~rce to

hold the valve closed and thereby block a bath to drain of the fluid in the

Autostop emergency Trip Header. Any decay in the mechanical Overspeed

and Manual Trip Header Pressure, such as could be caused by either a

manual trip or an overspeed trip, allows the spring to open the interface-

diaphragm valve releasing the emergency trip fluid to drain and tripping the

turbine.

The condition of the lubrication oil system's bearing oil supply is monitored by

the emergency trip system. Four pressure switches (63/LBO) monitor the

condition of the Bearing oil Header. If the header pressure decreases to the

set point contact closures from the pressure switches cause the autostop trip

(20/AST) solenoid valves to open and trip the turbine.

1.3.3.9 Lubrication Oil Supply System

1.3.3.9.1 General Function And Arrangement

The function of the lubrication oil supply system is to provide lubrication to the

turbine and generator main bearings, to provide lubrication to the thrust





69

bearing and turning gear, to provide oil for sealing the hydrogen seal oil

system and to provide a medium for the operation of the mechanical

overspeed trip mechanism.

The lubrication system consists of a turbine shaft driven main oil pump, oil

coolers, a vapor extraction system, an oil reservoir which includes an oil

ejector, motor driven oil pumps ,strainers ,heaters ,filters, etc. , various trip

and control devices and the interconnecting piping.

NOTE: he settings, pressures, and alarm points included in this leaflet are

approximate values.

1.3.3.9.2 Lubrication Oil Supply System

1.3.3.9.2.1 Oil

The oil used in the lubrication system must be a refined mineral oil of the

highest quality and uniformity and must contain additives to inhibit corrosion

and oxidation. Also, it must not contain any substances that will interfere with

the lubricating properties or will be detrimental to the oil or to the metals with

which it comes in contact.

It must be recognized that the oil characteristics require special considerations

to maintain the integrity of the oil and thereby the integrity of the lubrication

system components and the lubricated turbine components. Some of the

essential considerations are oil cleanliness, the physical and chemical

characteristics, proper storage and handling, and the proper method of adding

oil. A comprehensive program should be developed to assure that the oil and

the system are properly maintained and all harmful contaminants are avoided.

This is essential to maximizing the life of these components and assuring

trouble free operation. Harmful contaminants can result in damage to the





70

bearings ,seals ,and other vital components.

The oil should not be circulated in the system if its temperature is below 10℃

at the oil reservoir. Also, if the temperature of the bearing oil Supply cannot be

regulated to produce a bearing oil temperature of less than 82.2℃ at the

discharge of the hottest bearing, the unit should be tripped until the oil

temperature can be reduced and maintained in the proper temperature range.

1.3.3.9.2.2 Supply System Equipment

The lubrication oil supply system consists essentially of the following items：

1) One oil reservoir of 25 m3 capacity constructed of carbon steel and usually

located below the elevation of the axial centerline of the turbine-generator unit.

Two access openings on the top of the reservoir are fitted with gaskets and

manhole covers. Safety bars traverse the covers and are secured to mounting

blocks welded to the reservoir shell. The bottom of the reservoir contains a

flanged drain hole which is plugged during shipment but which may be

connected to the Purchaser' spiping system at his discretion.

2) One turbine shaft driven main oil pump is volute type ,centrifugal pump

mounted horizontally on the turbine extension shaft in the governor pedestal.

The impeller is not self-priming and must be supplied with oil under pressure

during start-up and shutdown periods. The suction piping extends down

through the top of the reservoir and is connected to the oil ejector discharge.

The main oil pump discharge is piped back into the reservoir where it is

connected to the oil ejector inlet and to the HP Seal Oil Backup Header. When

operating at normal speed, the main oil pump supplies all of the oil

requirements of the turbine generator, including the Bearing Oil Header, the

Mechanical Overspeed and Manual Trip Header,the HP and LP Seal Oil





71

Backup Headers, and the boiler feed pump control oil and lubrication oil

system headers on units with combined lubrication system.

3) One AC motor driven seal oil backup pump(SOB) mounted on top of the

reservoir. The SOB is a horizontally mounted, double helical gear, rotary type

pump designed for continuous duty. It is securely bolted to the top of the

reservoir and is connected to the AC motor with a rigid coupling. The suction

side of the pump is connected to piping that extends down through the top of

the reservoir to a point below the oil level to insure continuous positive suction.

The discharge side of the pump is connected to piping that also extends down

into the reservoir where it is connected to the HP Seal Oil Backup Header

piping. This is part of the main oil pump discharge (oil ejector inlet side) piping.

One check valve prevents backflow into the pump from the system, and

another prevents the pump discharge from flowing through the oil ejector. An

adjustable relief valve in the discharge piping inside the reservoir above the oil

level limits the discharge pressure to 8.08-8.78 bar (g). This relief valve is

accessible by removing an access cover in the top plate. The SOB pump is

used on start-up and shutdown when the main oil pump' s discharge pressure

is low and cannot supply all of the oil requirements. The SOB is controlled by

a pressure switch, 63/BOP, and by a three-position ( ON, OFF,AUTOMATIC)

switch mounted in the control room.

4) One AC motor driven bearing oil pump (BOP) mounted on top of the

reservoir. The BOP is a vertically mounted, centrifugal type pump designed for

continuous duty. The pump is completely submerged in the oil and is driven

by a vertical motor through a flexible coupling. A thrust bearing on the motor

support absorbs any hydraulic thrust and supports the weight of the rotor.

Provisions integral to the motor support isolate the motor from rising oil vapors

and prevent foreign matter from leaking into the reservoir. The BOP draws oil

through a strainer at the bottom of the pump and discharges it through piping





72

to the main oil pump suction, through the oil coolers to the Bearing Oil Header,

and to the LP Seal Oil Backup Header. The BOP is used on start-up and

shutdown when the main oil pump' s discharge pressure is low. The BOP is

controlled by a pressure switch 63/BOP,and by a three position (ON, OFF,

AUTOMATIC) switch mounted in the control room. A swing check valve

prevents back flow from the system.

5) One DC motor driven emergency oil pump (EOP) mounted on top of the

reservoir. The EOP is a vertically mounted, centrifugal type pump designed for

continuous duty. It is of identical construction to the BOP described above and

serves as a backup to the BOP. The EOP is used in emergency conditions

such as when AC power is lost or whenever the bearing oil pressure cannot

be maintained no matter what the reason. It is powered by the stationr s

battery system and is controlled by a pressure switch63/EOP,and by a three-

position (ON, OFF, AUTOMATIC ) switch mounted in the control room. See

the operation and pressure switch description sections of this leaflet. A swing

check valve prevents backflow from the system.

6) One oil ejector mounted in the piping below the oil level. The oil ejector

consists, essentially, of a nozzle, pickup chamber, throat, and a diffuser. The

nozzle inlet is connected to the main oil pump discharge which provides

motive oil. The oil passes through the nozzle, is directed through the pickup

chamber into the ejector throat, and finally passes into the diffuser. As the oil

passes through the nozzle ,its velocity increases. When this high velocity oil

passes through the pickup chamber, it creates a low pressure zone in the

pickup chamber and causes the oil from the reservoir to be drawn into the

pickup chamber and be carried with the high velocity oil into the ejector throat

area. The quantity of oil picked up from the reservoir is approximately equal

to the quantity provided to the nozzle inlet by the main oil pump. After passing

through the ejector throat area, the oil enters the diffuser where the oil velocity





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is converted to pressure. The oil is then piped through the oil coolers to the

Bearing Oil Header, to the main oil pump suction, and to the LP Seal Oil

Backup Header. A swing check valve, mounted after the diffuser, prevents

backflow from the system. A cheek plate mounted above the pickup chamber

inlets from the reservoir, prevents a backflow into the reservoir when the

bearing oil pump is running. A removable perforated, steel plate(mesh)

strainer mounted on the ejector' s suction side, prevents foreign matter from

entering the ejector.

7) One motor driven vapor extraction system mounted on top of the reservoir.

The vapor extraction system consists of a demister, an adjustable "blast gate"

butterfly valve, an AC motor driven turbo-blower, a check valve mounted in

the Purchaser’ s piping on the discharge side ,and the interconnecting piping

between the reservoir and the blower. The turbine blower is a single stage gas

blower designed for continuous operation. It is securely bolted to the top of the

reservoir and the motor is mounted on the side of the blower. The manually

adjusted butterfly valve is mounted on the suction side of the blower and

regulates the flow through the blower. The demister is mounted in the suction

side piping, and it extracts entrained liquid from the vapors flowing through it.

The extracted liquid is piped to drain. The suction piping extends through the

top of the reservoir to the area above the oil level where vapors accumulate.

The blower discharge piping is connected to the Purchaser' s piping which is

usually vented to the atmosphere. When operating, the blower creates a

slightly negative pressure in the suction side piping and the interconnected

parts of the oil reservoir and oil drain piping. This draws the oil vapors up

through the demister where any oil droplets are removed. After passing

through the demister, the vapors are discharged through the blower.

8) One 150 mesh strainer mounted in the oil return trough inside the reservoir.

The strainer is cylindrical and is made with perforated metal plate overlaid by





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metal screen. It fits down into an opening cut into the bottom of the trough.

The return oil in the trough is gravity fed into the top of the strainer,and it

passes through the bottom and sides of the strainer into the reservoir. The

strainer is fitted with a handle on top and can be removed through one of the

top access openings without disturbing the adjacent components. If removed

for any purpose ,the strainer should be thoroughly cleaned before returning it

to the reservoir. The strainer may be replaced while the unit is in service

however ,the unit should not be operated any longer than absolutely

necessary without the strainer in place and properly sealed with the gasket.

To minimize the period of time that the strainer is out, a clean, spare strainer

and gasket should be readily available.

9) Two oil coolers mounted in the vicinity of the reservoir. The oil supplied to

the Bearing Oil Header, no matter which pump provides the oil,is passed

through a cooler to regulate its temperature. The oil is circulated within the oil

cooler shell around the tube bundles while the cooling water passes through

the tubes. Only one oil cooler is normally in service at any time with the other

one on inactive status. The oil flow to the coolers is controlled by a manually

operated three-way valve which directs the flow to either cooler and permits

switching coolers without interrupting the flow of oil to the bearings. The oil

inlets to the coolers are connected through a crossover pipe and an

interchange valve which permits the inactive cooler to be filled with oil and

ready for immediate operation. Each oil cooler shell is vented back to the

reservoir through piping which enters the reservoir through the top and

extends to the area above the normal oil level. A vented sight flow gauge in

each line enables the operator to determine if oil is flowing through the cooler.

Note that with the inter change valve open ,both sight flows are full of oil.

10) Two immersion type heaters, mounted on the side of the reservoir, heat

the oil as required to maintain a sufficient temperature. The heaters are





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controlled by a three position (ON ,OFF,AUTO) switch which is usually located

near the reservoir. In the ON position, the heaters are energized continuously.

Normally, however, the switch is in the AUTO position and the heaters

operate automatically as controlled by a thermostat (23/ORR) which is

mounted in the side of the reservoir opposite of the oil cooler connections. For

safety, the heaters are normally interlocked with the oil level switches to

interrupt power to the heaters before the heater elements are uncovered. The

thermostat is adjustable by means of an externally mounted knob, and it

should be set to regulate the oil temperature in the normal operating range of

26.7℃- 37.8℃.

CAUTION：Whenever the oil level is below the normal operating level or

before draining any oil from the reservoir, ensure that the power to the heaters

is shut off. Energized heater elements that are not covered with oil will ignite

the oil vapors in the reservoir.

11) other controllers and pressure switches

1.3.3.10 Turbine Control System Summary

1.3.3.10.1 Introduction

The turbine control system adopts Digital Electro-Hydraulic (DEH) control

system. The DEH control system can suffice high reliable requirement for

turbine generator unit’s control. The DEH control system consists of five major

components that are listed below:

The controller of data collection and data processing

Operator interface (include CRT, operator keyboard, mouse and printer)





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Steam valve servo-actuators (include throttle valve actuator, governor

valve actuator, reheat stop valve actuator, interceptor valve actuator)

DEH oil supply system

Emergency trip system

The following information is offered as a general description of and an

introduction to the DEH system apparatus.

1.3.3.10.2 DEH controller

The electronic controller cabinets contain all circuits and memory for the

system, such as logic, reference, signal input cards, amplifiers, automatic and

manual controllers, redundant power supply and terminal strips etc. It

performs basic computation on reference and turbine feedback signals and

generates an output signal to the steam valve actuators. The controller

includes workstation, control processor unit, I/O card etc. The control

processor unit adopts redundancy configure. The control processor unit are

programmed so that each performs a specific function of the turbine control

process (include Over-speed Protection/Operator Auto Controller).

1.3.3. 10.3 DEH function

DEH control system controls turbine start, rolling procedure, synchronize

interface and load through CRT in operation.

The DEH control device has the following function:





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Speed Control

The logic of turbine speed control will perform the entire loop control from the

turning gear to synchronize or over-speed trip test. It is of a wide speed

control function (0-3500r/min, control precision is±1r/mn)

Over-speed Protection Function

DEH have over-speed protection control function, when the turbine speed

reaches 103% rated speed, over-speed protection controller (OPC) will close

all of the governor valve and interceptor valve rapidly to protect turbine speed,

avoiding turbine over-speed. After a few seconds, the governor valve will

automatically reopen. When the turbine speed is above the trip speed (110%

of rated speed), DEH control system will send trip signal, and close all steam

valve rapidly.

Over-speed Trip Test

Over-speed trip test must be performed in DEH control mode, over-speed trip

test have two-test mode mainly, and they are mechanical over-speed trip test

and electric over-speed test.

Synchronize the Unit

When the turbine speed reaches 3000r/min, operator access automatically

synchronize control from custom graphic, the turbine that accept

increase/decrease signal from synchronizing device control the turbine speed,

and perform synchronizing.

Load Control





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After the turbine speed is at rated speed, synchronize interface, load, operator

will control load according to pre-given target load and acceleration rate.

The function of Initial Load

When the generator breaker is closed, an initial load of approximately 5% is

automatically taken by DEH.

Remote control mode

In remote control mode, DEH will accept 4~20mA signals from CCS, and

control turbine load, to achieve harmonious control between boiler and turbine.

The function of Valve Management

During the turbine start up, the turbine runs in single valve control mode. Six-

governor valve and two reheat governor valve all open at the same time. In

this way, the rotor and cylinder will gain symmetrical quantity of heat, avoiding

heat expansion. After the turbine carry certain load, the sequence valve

control mode will be selected, according to the quantity of load, six-governor

valves open in sequence, thus the control mode reduce valve’s throttle loss,

raise efficiency. Meantime opening valve gain less shock from steam flow, the

longevity of valves gains to rise. When valve control mode transfer, the

influence of load is less.

The function of Valve Test

A function of the turbine valve test is to be performed and can be made while

the unit is carrying load. The purpose of this test is to ensure proper, safety





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operation, to supervise valve flexible. When the turbine is run, the turbine

steam valve can test for certain period.

The function of Throttle Pressure Limiter

A function of the throttle pressure limiter is to be performed. Operator sets the

throttle pressure limiter value. When the throttle pressure is less than the

throttle pressure’s setpoint, the governor valve will close to maintain the

throttle pressure.

1.3.3. 10.4 Operator interface

The operator’s interface, which is usually located in the control room, is the

unit’s control center. The interface consists of a CRT, operator keyboard and

printer. Through the use of the keyboard various, pre-designed graphic pages

can be accessed. Each of these pages provides the operator with access to

different areas of turbine operation. For example, there is a page to change

the status of feedback loops, to select speed or load target.

Operator settings made at the keyboard are used by the electronic controller

to position the steam valves by comparing the turbine speed, first stage steam

pressure, and megawatts signals to the target settings selected by the

operator.

The printer, which is usually located in the control room, operator can watch

alarm and turbine message.

1.3.3. 10.5 Steam Valve servo-actuators





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Each of steam valve servo-actuators controls each of steam valve. The

opening of hydraulic cylinder of actuator is moved by EH fluid pressure and its

closing be by springing force. The signal side entrance hydraulic cylinder

connects with a control block on which shutoff valves unload valves and check

valves are mounted. In addition to different assemblies, two fundamental type

actuators are consisted.

General, reheat stop valve actuator belongs to open-close type, which control

the steam valve. The high-pressure fluid entrances the bottom chamber of

hydraulic cylinder, the high-pressure fluid of the chamber can be controller by

rapidly unload valve, which is controlled by the pilot valve. When the turbine

control system is reset, the pilot valve control the unload valve to close. The

high-pressure fluid of the chamber will build up gradually to open the reheat

stop valve actuator,

The governor valve actuator control the steam valve at any intermediate

position and control the steam flow in proportional to meet the requirement.

The actuator is equipped with EH transformer and linear variable differential

transformer (LVDT). The high-pressure fluid supply to EH transformer by a 3

micron cartridge. The EH transformer accept servo amplifier’s valve signal

and control the actuator position. The LVDT output an analogy signal

proportional as a feedback signal, and form a closed loop.

Isolating valve can maintain the part of executive (including hydraulic cylinder)

online. The check valve can prevent the high-pressure fluid flow to return by

the drain fluid an emergency trip system.

1.3.3.10.5.1 Throttle valve actuator





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The actuator operates the throttle valve. It is mounted on the side of each

throttle valve spring house and its piston rod is connected to the throttle valve

operating lever. This lever is so fulcrumed that upward movement opens the

valve. The actuator is single acting and provides the force for opening the

valve and closing springs provide the force to close the valve.

The principal components of the actuator are hydraulic cylinder, block, servo

valve, relief valve, LVDT, shutoff valve, check valves and filter. The block

provides a means for mounting and connecting all the components together

and is also a terminal for all electrical and hydraulic connections.

The flow of high pressure fluid through an isolation valve and a 3 micron metal

mesh filter to the actuator is controlled by a servo valve. The position control

and LVDT position feedback signals are summed at the servo amplifier

resulting in a position error signal. The servo amplifer positions the servo

valve in response to this error signal to accurately position the actuator and

steam valve. The servo valve admits high pressure fluid to the hydraulic

cylinder to open the steam valve and release operating fluid from the hydraulic

cylinder to allow the steam valve to close. The servo valve is mechanically

biased to assure fail safe operation for loss of electrical signal.

A pilot operated relief valve is used as a dump valve. The pilot is actuated by

the emergency trip header to provide quick closing independent of the

electrical system. When the dump valve is activated it release all operating

fluid to drain. The drain is also connected to the upper end of the hydraulic

cylinder and accommodates the released fluid so that the drain line is not

overloaded. Heavy springs on the valve assembly provide the force for quick

closing.

1.3.3. 10.5.2 Governor valve actuator





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The actuator operates the steam chest control valves. It is mounted on the

side of each steam chest and its piston rod is connected through a pair of

links to the control valve operating lever. This lever is so fulcrumed that

upward movement opens and provides the force for opening the valve and

closing springs provide the force to close the valve.

The principal components of the actuator are hydraulic cylinder, block, servo

valve, relief valve, LVDT, shutoff valve, check valves and filter. The block



The flow of high pressure fluid through an isolation valve and a 3 micron metal

mesh filter to the actuator is controlled by a servo valve. The position control

and LVDT position feedback signals are summed at the servo amplifier

resulting in a position error signal. The servo amplifer positions the servo

valve in response to this error signal to accurately position the actuator and

steam valve. The servo valve admits high pressure fluid to the hydraulic

cylinder to open the steam valve and release operating fluid from the hydraulic

cylinder to allow the steam valve to close. The servo valve is mechanically

biased to assure fail safe operation for loss of electrical signal.

A pilot operated relief valve is used as a dump valve. The pilot is actuated by

the auxiliary governor trip to provide quick closing independent of the

electrical system. When the dump valve is activated it release all operating

fluid to drain. The drain is also connected to the upper end of the hydraulic

cylinder and accommodates the released fluid so that the drain line is not

overloaded. Heavy springs on the valve assembly provide the force for quick

closing.





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1.3.3. 10.5.3 Reheat stop valve actuator

The actuator is provided to operate the reheat stop valve. It is mounted on

each stop valve spring house and its piston rod is connected directly to the

stop valve piston rod. Therefore, upward movement of the operating piston

opens the valve and downward movement closes the valve. This valve

operates in a full open or full closed position. The actuator is single acting and

provides the force for opening the valve and closing springs provide the force

to close the valve.

The principal components of the actuator are hydraulic cylinder, block,

solenoid valve, relief valve, shutoff valve and check valves. The block



The flow of high pressure fluid through an isolation valve to the actuator is

controlled by an orifice. The high pressure fluid is admitted through an orifice

to the hydraulic cylinder to open the steam valve, and the dump valve

releases the operating fluid from the hydraulic cylinder to allow the steam

valve to close.

A pilot-operated relief valve is used as a dump valve. The pilot is actuated by

the emergency trip header to provide quick closing independent of electrical

system. When the dump valve is activated it release all high pressure

operating fluid to drain. The drain is also connected to the upper end of the

hydraulic cylinder and accommodates the released fluid so that the drain line

is not overloaded. Heavy springs on the valve assembly provide the force for

quick closing.

1.3.3.10.5.4 Interceptor valve actuator





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The interceptor valve servoactuator positions the interceptor valve. It is a

single acting, pull type actuator, utilizing high pressure fluid to rapidly and

precisely position the interceptor valve in response to signals from the

electronic controller. The servo actuator is mounted on the interceptor valve

spring housing, and its piston rod is connected to the interceptor valve stem

with a coupling. Upward movement of the piston rod opens the interceptor

valve, and downward movement closes it. Heavy closing springs hold the

interceptor valve in the closed position, and the servo actuator overcomes the

spring force to position the interceptor valve in any open position.

The principal components of the servo actuator are the hydraulic cylinder,

block, servo valve, dump valve, test solenoid valve, LVDT and a manifold

block that includes a shutoff valve and check valves. The actuator block

provides a means for mounting and hydraulically connecting all the

components together and is also a terminal for all electrical and hydraulic

connections.

High pressure fluid is admitted to the servo valve through a filter. Within the

servo valve, the fluid enters a chamber containing a shifting spool whose

movement uncovers ports that direct the fluid flow to or from the chamber

beneath the operating piston of the hydraulic cylinder. As the fluid pressure

increases beneath the piston, it overcomes the force of the interceptor valve’s

closing springs and opens the valve.

The filtered high pressure fluid is also supplied through the de-energized test

solenoid valve to the upper chamber of the dump valve. This fluid seats the

dump valve which, in the closed position, blocks a path to drain of the fluid

beneath the hydraulic cylinder’s operating piston.





85

The servo valve is electrically controlled and responds to signals from the

electronic controller which supplies a positioning signal that is based upon the

desired valve position. The servo valve spool shifts accordingly to direct either

more or less fluid to the hydraulic cylinder in order to move the interceptor

valve to the required position. The LVDT provides a feedback signal of the

actual interceptor valve position to the controller. The controller then

continually adjusts the positioning signal to the servo valve in order to reduce

the error between the desired valve position and actual valve position(which is

from the LVDT feedback signal).

When the desired valve position is reached the servo valve spool shifts to a

position where it directs only a slight amount of high pressure fluid to the

hydraulic cylinder. This slight flow compensates for leakage past the dump

valve and the hydraulic cylinder’s operating piston. With the spool in this

position, the servo valve also function as an orifice, effectively damping any

servoactuator movement resulting from pressure fluctuations in the high

pressure fluid supply.

The servo actuator closes the interceptor valve if either the servo valve

completely stops, the flow of fluid to the hydraulic cylinder, or the isolation

valve closes. In either case, system leakage from around the operating piston

and past the seated dump valve causes the fluid pressure beneath the

operating piston to decay sufficiently to allow the springs to close the

interceptor valve. The servo actuator will also close the interceptor valve if the

dump valve unseats. The dump valve unseats if either the test solenoid valve

is energized during testing, the high pressure fluid supply pressure is too low,

or the emergency trip fluid header pressure is lost.

1.3.3.10.6 EH fluid supply portion





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The control system ‘s overall function is to position the turbine steam inlet

valves in order to regulate the flow of steam through the turbine. The control

system is separated into two parts: the EH fluid supply portion and the control

portion which are interconnected with stainless steel tubing and fittings.

The control portion of this system positions the steam inlet valves in response

to electrical commands from the solid state electronic controller. It positions

the valves by means of servo actuators which use high pressure EH fluid as a

motive force. Provisions are also included for automatically closing the valves

in emergency conditions. The control portion consists of the various servo

actuators which are mounted on the steam inlet valves, an emergency trip

control block and solenoid operated valves, an EH fluid test block assembly, a

fluid operated air pilot valve, an interface diaphragm valve, and the electronic

controller.

The EH fluid supply portion provides the fluid and pressure requirements of

the control portion while maintaining the integrity of the fluid. It consists of a

fluid filter, high pressure accumulators, low pressure accumulators, various

pressure control valves and fluid pumps and motors.

To ensure reliability of supplying oil, the supply oil system include stainless

steel reservoir, piston pumps, control book, filters and heat exchangers. The

system is arranged so that one pump and one set of various control

component function while duplicate set serves as a standby system.

Motive fluid for the EH control system is provided by a fluid supply system

consisting of an EH fluid supply said, high-pressure accumulators, fluid

conditioning system, and interconnecting turbine. Supply header pressure is

maintained at a constant 14Mpa by duple variable displacement pressure

compensated pumps in conjunction with high-pressure accumulators located

near the steam valve actuators. The variable displacement pump





87

compensated maintains constant header pressure for normal steady state and

transient fluid flow demands that can’t be supplied by the pump. A relief valve,

set at 16.7Mpa , prevents system over-pressurization.

A separate lubrication oil system supplies lubricant to the turbine and

generator bearings and provides a medium to hydraulically operate the

mechanical overspeed trip mechanism and manual trip lever. It is interlocked

with the control system through the interface diaphragm valve.

1.3.3. 10.7 Emergency Trip System

The emergency trip system monitors certain turbine parameters and close all

turbine steam inlet valves when the operating limits of these parameters are

exceeded. The parameters monitored are the following:

Turbine overspeed

Thrust bearing wear

Low bearing oil pressure

Low condenser vacuum

Low EH fluid pressure

A remote trip which accepts all additional ex ternal trips is also provided.

The system utilizes a two-channel concept which permits on-line testing with

continuous protection afforded during the test sequence.

The system consists of an emergency trip control block with trip solenoid

valves and status pressure switches, three test trip blocks with pressure

switches and test solenoid valves, rotor position pickups, speed pickups, a

cabinet containing electrical and electronic hardware and a test panel.





88

The sensing devices at the turbine transmit electrical signals to the trip cabinet

where logic determines when to trip the auto stop emergency trip header.

EMERGENCY TRIP CONTROL BLOCK

The auto stop emergency trip header, pressure is established when the auto

stop trip solenoid vlaves (20/AST) are energized closed. The valves are

arranged in two channels for testing purposes. The odd numbered pair

correspond to channe 1 and the even numbered pair correspond to channel 2.

This convention is carried throughout the emergency trip system in

designating all devices ,e.g. channel 1 devices are odd numbered, and

channel 2 devices are even numbered. Both valves in a channel will open to

trip that channel. It can be seen that both channels must trip before the auto

stop trip header pressure collapses to close the turbine steam inlet valves.

On-line testing can be ac complished by "tripping" one channel at a time.

The 20/AST solenoid valves are externally piloted two-stage valves. EH Fluid

pressure is applied to the pilot piston to close the main valve. The pilot

pressure of each channel is monitored by a 63/AST pressure switch. The

pressure switch is used to determine the tripped or latched status and as

an interlock to prevent testing one channel when the other channel is being

tested.

TEST BLOCKS

The schematic of test blocks for bearing oil pressure、EH fluid pressure and

condenser vacuum are following: each test block assembly consists of a steel

test block, two prssure gauges, two shut off valves, two solenoid valves and

three needle valves. Each assembly is arranged into two channels. The





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assemblies, mounted on the governor pedestal, are connected to pressure

switches mounted in a nearby terminal box. (The assemblies are orificed off

from the system supply on one side and connected the drain or vent on the

other side). An orifice is provided in each channel so that the measured

parameter is not affected during testing. An isolation valve on the supply side

allows the test block assembly to be serviced without contamicating the rest of

the system.

If the medium (pressure or vacuum)reaches a trip level, then the pressure

switches would function and cause the auto-stop emergency trip header to

trip. When testing, the medium is reduced to the trip level in that channel

either locally through the hand test valves or remotely from the trip test panel

via the test solenoid valves.

THRUST BEARING TRIP DEVICE

Position pickups, which are part of the turbine supervisory instrument package,

monitor movement of a dIsc mounted on the rotor near the thrust bearing

collar. Any axial movement of this collar will also be reflected in movement of

the disc. Excessive movement of the disc is an indication of thrust bearing

wear. Should excessive movement occur. relay contacts from the supervisory

in strument modules colse to effect a turbine trip.

The thrust bearing trip function can be tested by a test device on which the

pickups are mounted. A trip condition is simulated by moving the pickups

toward or away from the disc or the rotor.

ELECTRICAL OVERSPEED TRIP





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The electrical overspeed channel consists of three magnetic pickups mounted

at the turning gear and a speed cage mounted in the trip system cabinet. The

output frequency of the pick up is proportional to the shaft speed. This

frequency is converted to an analogue signal which is compared with the trip

set point voitage. As long as the shaft is less than the trip set point, the output

of comparator is a positive voltage. If the voltage corresponding to shaft

speed exceeds the trip set point, the comparator output voltage goes negative

which turns on transistor QI picking up relay OST. Contacts from this relay

cause both auto stop channels to trip.

MECHANICAL OVERSPEED TRIP

A mechanical overspeed trip device is provided. Both mechanical and

electrical speed trips are set at the same trip speed. The mechanical

overspeed trip mechanism consists of a spring loaded trip weight mounted in

a transverse hole in the rotor ex tension shaft. Under normal operating

conditions, the trip weight is held in the inner position by the compression of

the spring. When the turbine speed reaches the trip set point, the increased

centrifugal force overcomes the compression force of the spring which throws

the trip weight outward striking a trigger. As the trigger moves , it unseats a

cup vlave which drains the mechanical overspeed and manual trip header. As

the header pressure collapses, the interface deaphragm valve unseats,

tripping the auto stop emergency trip header. The mechanical overspeed and

manual trip header can be tripped manually via a trip handle mounted on the

governor pedestal.

1.3.4 Turbine HBD

Type：N300－16.7/538/538





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1) VWO (valve wide open) condition

Items Unit VWO

Maximum output MW 315.136

Steam pressure at the inlet of MSV MPa.a 16.7

Steam temperature at the inlet of MSV ℃ 538

Reheat steam temperature at combined valves ℃ 538

Steam flow for main steam t/h 987.523

Steam flow for hot reheat steam t/h 794.676

Back pressure of condenser kPa(a) 10.05

Final feed water temperature ℃ 279.5 2) Heat Rate Guarantee Condition

Items Unit Heat Rate Guarantee

Rate output MW 300.083

Steam pressure at the inlet of MSV MPa.(a) 16.7





Back pressure of condenser kPa(a) 10.05

Final feed water temperature ℃ 275.8

3) All HP Heater out of service Condition





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Items Unit All HP Heater out

of service

Rate output MW 300.215

Steam pressure at the inlet of MSV MPa.(a) 16.7





Back pressure of condenser KPa(a) 10.05

Final feed water temperature ℃ 175.1

An ac motor operated rotor turning gear for automatic and local-remote &

manual operation shall be provided. A zero speed sensing device shall be

provided for control of automatic operation. The turbine generator unit shall be

designed to withstand the stresses due to an over-speed of 20 percent above

normal synchronous speed, without reducing the life of the machine.

1.4 Generator

1.4.1 General

The generator is a two-pole, cylindrical rotor type synchronous machine,

directly coupled with steam turbine.

Generator type: QFSN-300-2

Rated output 353MVA/300 MW

Rated voltage 20 kV





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Rated current 10189 A

Power factor 0.85 (Lagging)

Speed 3000 r/min

Frequency 50 Hz

No. of phase 3

Cooling method

Stator winding Direct Water cooled

Rotor winding Direct Hydrogen cooled

Exciter method Brushless excitation system

1.4.2 Introduction of QFSN-300-2 generator

a. INTRODUCTION The generator supplied was designed and manufactured under the licence of

Westinghouse Electrical Corp.(WEC) in accordance with ANSI C50.10, ANSI

C50.13, IEC34-1 and IEC34-3. It is an updated hydrogen and water inner -

cooled generator, joint - developed by Shanghai Electrical Machinery

Manufacturing Works (SEMMW) (now STGC) and Westinghouse Electric

Corp. (WEC) in 1985.

b. GENERATOR VENTILATION AND COOLING SYSTEM

The ventilation system provides uniform cooling of the entire generator frame using hydrogen as the cooling medium. This time-proven system, supplied on





94

large steam turbine-driven generators for decades, permits a generator to be designed for optimum physical size and electrical capacity.

Hydrogen gas circulates in a closed circuit inside the generator by two single-stage axial blowers, mounted on both ends of the rotor. The blowers are located immediately ahead of the coolers so that the gas temp. rise due to the blower losses will not be added to the total temperature rises of the electrical components. All generator components, rotor winding, stator core, end region flux shield structures and lead box, except the stator winding, are hydrogen cooled. The hydrogen is cooled by the hydrogen-to-water coolers located vertically at both ends of the generator. Cold gas from the coolers flows in two symmetrical paths, with the exception that there is gas flow in the lead box on the exciter end.

The stator core and rotor winding are cooled by separate but parallel flow circuits. The air gap serves as a plenum to return the gas back to the axial blower.

For the rotor, the cold gas is admitted at each end of the rotor through the annular space under the rotor winding retaining rings. The most part of the flow enters the main rotor body sub-slots machined underneath each rotor winding slot. From these sub-slots the gas flows into the radial vent ducts on rotor winding and discharges into the air gap through holes in the rotor wedges. A fraction of gas flow is diverted to cool the rotor end turn, This flow is divided into two paths, the straight and the arc path. For the straight path, it flows axially towards the main rotor body and discharges through radial ducts into the air gap. The arc portion of the end turns are cooled by hydrogen flowing circumferentially towards the pole centerline and discharging into the air gap through scooped passages at the end of the rotor body.

The stator core is radially ventilated. The cooling gas is forced to the space between the core and the generator frame by the axial blowers on both ends. From this space it flows radially inwards through radial vents and towards the air gap.

The stator coils , parallel rings, main leads and terminal bushings are cooled directly with de - ionized water. Cooling water flows from main inlet pipe into the inlet water manifold, then enters the teflon hose of each coil bar at exciter end, passes through the whole length of the hollow conductors in coils and





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the teflon hoses at the other ends, then exits to the water outlet manifold at the turbine end where it picks up the drain water from the phase leads and terminal bushings and returns to the water tank. Hot water is cooled by water coolers before pumped back to the stator winding.

c. FRAME

The generator is of an integral frame construction, reducing erection expenses and giving protection to the internal components during transportation and erection. It may be splitted into 3 sections for shipment in order to reduce the max. weight and dimensions for transportation in conformity with those specified by customers, and is then site - assembled to be an integral piece, having a good gas-tight frame and maximum protection to the internal components.

The generator frame is a heavily ribbed cylinder which supports the stator core and windings, bearing brackets, and rotor assembly. The frame and the enclosing bearing brackets are fabricated from steel plates .

The generator frame is designed to be “explosion-safe”. This means that the frame will contain and withstand an internal explosion of the most explosive mixture of hydrogen and air at the most probable conditions of occurrence, i.e., at atmospheric pressures during gas changing operations, without damage to life or property external to the machine. Some internal damage may occur with such an explosion.

Four hydrogen coolers each of which has two sections, are mounted vertically at each corner of the generator frame.

The generator frame is supported by frame feet along its length on foundation seating plates. Foundation bolts resist short-circuit torques applied to the frame. Shims between frame feet and seating plates are provided for generator alignment with respect to the steam turbine generator shaft system. A number of jack screws are also provided in the generator frame feet for vertical alignment. Axial anchors for the frame feet and also for the seating plates allow for thermal expansion of the generator in both axial directions from the centerline of the generator. Transverse anchors engage the bearing





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brackets on each end of the generator to maintain the generator lateral position while allowing the axial expansion.

d. STATOR CORE DESIGN

The stator core is composed of high permeability, low loss silicon steel laminations coated on both side with an effective class F varnish. The laminations are aligned and held together by dovetail key bars at the outside diameter which also serve as tension members to clamp the core axially by means of cast austenitic steel end plates. The end plates are sufficiently rigid to apply pressure evenly over the core cross section when loaded by the key bars at the outside diameter. The end plates are non - magnetic and with sufficient yield strength. The key bars are attached to the spring beams. The core is thus attached to the frame via the spring beams which reduce the amplitude of the double frequency core vibratory force transmitted to the generator frame and foundation. The mounting is such that very little of the core vibratory force is transmitted to the housing, but the core is rigidly restrained against load and short circuit torques. The stator core is tested for integrity during the manufacturing operation using a "loop testing" procedure. This procedure which simulates actual operation consists of circulating rated magnetic flux through the core laminations and inspecting the core for local hot spots by using a thermal vision camera capable of detecting small temperature differences. Any local hot spots, which are indications of deterioration in progress, are to be repaired. The lack of core problems in SEMMW (now STGC) generators is attributed to attention to core design and testing for core integrity as described above.

At the bore diameter equally spaced slots run the entire length of the stator core. These slots extend into the core for assembly of the stator coils.

A copper end-shield with a laminated magnetic shield protects the end plate and the core tooth area from end region flux.

e STATOR WINDING DESIGN

e.1 Water cooled stator coils

The stator winding consists of water inner-cooled, single turn, half coils wound in open slots and secured in place by glass-epoxy wedges. Each





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stator coil is made up of two half coils shaped on a former and joined together after assembly in the slots. The stator coils of this generator are composed of insulated solid copper strands and insulated hollow copper conductors. Each strand and hollow conductor are wrapped with an electrical grade continuous filament type epoxy resin glass fiber to form a smooth continuous uniform insulation at all points. The strands together with hollow conductors undergo 540°Robel transposition in the slot portion of the coil.. This glass covering is then treated to give a smooth surface finish which is tough and flexible and will withstand abrasion from each other in the coil of the stator winding during operation.

Effective cooling of the stator coils is achieved by the cold deionized water. The water flows from the inlet manifold at the exciter end of generator into the coil ends thru teflon insulating hoses, then discharges from the stator coil at other end, where it is collected by teflon insulating hoses on a discharge manifold. The parallel rings and lead terminals are composed of insulated hollow copper conductors for direct water cooling. All six terminals of the three phase winding are brought out at the exciter end of the lead box beneath the floor level through gas tight porcelain bushings.

Resistance temperature detectors are provided to measure the temperature of the stator coils and their hot water discharge and to detect any abnormal conditions. Leads from the temperature detectors are connected to terminal boards.

e.2 Stator Coil Insulation

Epoxy-Mica insulation is used to provide the ground wall insulation on the stator coil. To give good dielectric and mechanical strength, the ground insulation is continuously wound with several layers of epoxy resin mica-paper tape then cured at high pressure and temperature in the former. Epoxy-Mica insulation is a tough, yet thermally flexible dielectric barrier with excellent electrical and physical properties. The excellent dielectrical properties of the resin, coupled with good insulation consolidation, results in Epoxy-Mica with lower dielectric loss tan( , increased dielectric strength, and remarkable improvement of voltage endurance. Its consistently low dielectric loss is less affected by temperature and voltage variation than other types of insulation. Epoxy-Mica insulation has great thermal endurance and long life.





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The character of the resin provides solid, yet elastic physical bonds between mica papers. The resilient nature of the resinbond permits elastic cyclic displacement of adjacent mica papers and provides restoring force within the insulation ground-wall. This makes Epoxy-Mica insulation ideally suitable for cyclic duty operation. The insulation is also inert to ordinary chemicals, oils, and solvents and has an unusually high moisture resistance. It was developed in the late 1960's, and first placed in service in 1966. Continued improvements have made Epoxy-Mica insulation a superior insulation for high-voltage coils, satisfying the requirement of class F insulation.

Effective corona suppression is provided by the use of a low-resistance, conducting varnish on the coil slot section to contain the dielectric stress within the solid insulation and a combine process of a low resistance conducting varnish and a high-resistance, semi-conducting varnish in the end-turns to grade voltage stress along the coil surface.

Quality Assurance checks are performed on each coil and the complete winding to verify insulation integrity. Each coil is given a high-potential test well in excess of final winding high-potential test values before being wound into the machine. Each set of coils includes extras which are chosen at random from the set for testing to destruction, thus giving further verification of insulation integrity. Additional high-potential tests are performed both during and after completion of the stator winding.

e.3 Stator Winding Bracing

Of equal importance with the insulation system is the method of slot-fill and bracing used to protect the stator coils from the vibratory stresses experienced during steady-state operation and from the transient disturbances which can be experienced during abnormal operating conditions. The ANSI and IEC Standards set the requirements for steady-state operation and define the abnormal operating conditions which must be met.

Each coil is secured in the slot by a glass-epoxy wedge assembled in wedge grooves in the slot. Epoxy impregnated conforming materials are placed under the bottom coil and between the bottom and the top coils to suit the coil in slot. The tightness is maintained by the prestressed driving strip ( PSDS or





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ripple spring )-- a wave glass fiber epoxy strip-- directly below the slot wedge, maintaining radial pressure on coils and slot wedges.

Flat glass-epoxy filler strips are assembled above the coils in the slots to distribute the load of the PSDS.

Flat filler strips are also utilized on one side of the coil to provide a tight fit in the slot. These supporting members virtually eliminate potentially damaging coil vibration caused by the electromagnetic forces that are present. The entire stator is thermally cured under pressure to consolidate slot contents and reduce vibratory stresses due to coil motion. The consolidation of ground wall and filler materials and the use of ripple spring between coils and wedges gives unsurpassed slot compactness for long service life.

The radial winding clamp composed of high-strength glass epoxy clamping plates and non-magnetic bolts together with support rings and bracing brackets provides radial, structural consolidation of the end winding. The radial clamps provide clamping forces well in excess of the vibratory forces between the top and bottom coils. This reduces vibration of the individual coils relative to the strain blocks used between top and bottom coils, as well as to the diamond spacer assemblies used between adjacent coils. This reduced radial vibration will prevent relative motion and wear between the coils and the strain blocks. Clamping plates and non-magnetic bolts secure the coils to the bracing brackets.

De-coupled end winding support bracing consist of bracing brackets, teflon slip layers and spring structure through which the bracing brackets attach to the core end plates so as to de-couple the end windings from the core and to improve the end winding to radial brace attachment. The brace provides for dynamic isolation between the coils and core to permit detuning of the end winding natural frequency well below 100 Hz, the exciting frequency.

There are Fluoroelastomer rubber layers with good physical and dielectric properties placed between the insulating clamp plates and coils for protecting coil from wear of insulation, as well as for damping coil vibration.

This end-winding bracing system has effectively controled the forces which result from both steady and short circuit conditions and also allows axial motion for thermal expansion. as proved by long operation practice.





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This bracing design is found in the fact that, by isolating the stiffness of the core from the end winding support, the end winding dynamics can be favorably changed.

e.4 MAIN LEADS

Stator parallel rings, phase leads and main lead bushings are directly cooled by the water. The main lead bushings are assembled in a gas-tight main lead box located underneath the frame at the exciter end. Bushings can be replaced without removing the generator rotor. The six main lead bushings extend from the lead box, three of which are used for the main leads connecting to the main transformer and three of which are used to form the neutral tie. Each bushing can be provided with up to four bushing mounted current transformers. Current transformers are suitable for metering, relaying, or voltage regulator service. The current transformers have a secondary current level of five amperes.

f. GENERATOR ROTOR

The cylindrical type rotor forging is made from chromium, nickel, molybdenum, vanadium alloy steel and is poured with the vacuum degassing process. Forging materials are ultrasonically tested for compliance with rigid quality assurance specifications. A bore hole is provided to remove centerline indications. The bore hole may then be used in later years for examination of forging integrity. Two pole rotors have their pole faces slotted so as to equalize flexibility and to reduce double-frequency vibration.

Rotor winding components are subjected to stresses both from rotation and from thermal expansion and contraction. It is essential that these stresses be accounted for and limited in the rotor design. During startups, shutdowns, and load changes the rotor winding will move relative to the rotor structural parts. Built-in clearances and slip layers allow for this motion while reducing the frictional forces which could cause distress or shaft vibration. Hard-drawn, creep resistant, silver-bearing copper and glass-laminate turn-to-turn insulation reduces the chance of permanent winding deformation or shorted rotor turns. The winding is held firmly against rotational forces by nonmagnetic retaining rings and high-strength rotor slot wedges. In the rotor end turn area, customarily fitted glass epoxy blocking and spacers maintain





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alignment of the winding components. The end winding curved sections potentially high stress areas are arranged with brazed connections located well away from the curves. Axial expansion is controlled by allowing for expansion to occur and by including teflon slip layers in the rotor slots and under the retaining ring, to limit the friction that opposes axial motion.

The field winding is manufactured from high-strength alloy copper. This silver-bearing alloy copper contains the necessary metallurgical creep-resistant properties to minimize distortion during operation. The individual turns of the rotor winding are made up of two conductors. On the end turns each consisting of two copper channel sections, which form a gas passage for the hydrogen. For turns inside slots, there are two parallel rows of slim vent ducts evenly distributed along the winding slots to form radial vent holes over the sub-slots. The field winding insulation is provided with extra creepage distance on the top turns. The windings are placed in rectangular slots which are lined with one piece, molded insulating slot cells. The slot cells are teflon lined on the inner surface to permit the rotor copper to move axially due to thermal expansion and contraction. The insulation between turns consists of glass laminate bonded to the copper. The glass laminate exhibits excellent wear characteristics and has a high coefficient of friction, which reduces relative slippage between coil turns that causes wear and copper dusting. Instead, the entire coil slot structure acts as a unit rather than individual turns. After the rotor is pressed and cured, fitted, high-strength slot wedges are driven into the top of the slots.

The rotor end turns are supported radially against rotational forces by 18Mn18Cr nonmagnetic retaining rings shrunk onto the rotor body. This alloy is highly resistant to corrosion and stress corrosion cracking in the presence of moisture and other corrodents. These retaining rings are nonmagnetic steel forgings. These floating-type retaining rings, with teflon surfaced insulating liners, prevent distortion of the rotor copper and abrasion of the rotor coil insulation. The rings are shrunk and keyed onto machined sections at the ends of the rotor body with a firm fit at overspeed and rated temperature. The heavy shrink fit provides a low-resistance electrical path for induced rotor surface currents, thereby reducing heating due to rotor surface currents. A circumferential locking ring is provided to prevent axial movement of the retaining ring. This method of support permits the shaft to flex without causing





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fretting at the joint or overstressing the rotor winding and is used to eliminate the effect of shaft deflection on the rotor end winding assembly.

An amortisseur winding is provided which uses copper damper bars in each rotor slot connected at the ends by beryllium copper wedges to the retaining rings. This design meets the requirements of the industry standards for negative-phase-sequence current capability.

This machine has two single stage blowers, mounted on the rotor shaft at both ends. The outside diameter of the blower blades is smaller than that of the retaining ring. The blower hub outside diameter is designed to be small enough to allow removal of the retaining ring over it, if necessary, for winding inspection. After unshrunk from the retaining ring, the end plate can be slided over the spacer ring and attached to the blower hub during repairing.

The completed rotor is dynamically balanced. It is carefully baked and seasoned at running speed to promote lasting stability of the rotor winding components. Standard equality control tests are made on every rotor before and after over-speed tests to verify that no shorted rotor turns have developed. It is performed by means of a continuous impedance test as the rotor speed is increased from rest up to rated speed and back to rest. The rotor is then carefully inspected and a final high-potential test is performed.

g. BEARING, GLAND SEAL AND BEARING BRACKETS

The bearings, supported in rugged fabricated bearing brackets, are insulated and may be removed without removing the hydrogen seals from the machine. Bearing and gland seal insulation is provided at the following places on both ends of the generator to prevent shaft currents from flowing through the bearings: between the bearing pad and the bearing seat; between the gland seals and the brackets; between the bearing oil seals and the brackets; and at the stop dowel and bearing key. In addition, the pieces on the exciter end are "double insulated" with terminals for checking the insulation resistance of the bearing and gland seal insulation during operation. Only the exciter end bearing is "double insulated". Since the combination of insulation and the shaft grounding brushes, which are located on the turning gear pedestal, is considered satisfactory for preventing bearing currents in the turbine end bearing of the generator. The ring type gland seals are also housed in the bearing brackets to maintain a gas-tight shaft seal. The shaft seals are of





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double oil flow construction with separate air and hydrogen side oil supplies to reduce hydrogen consumption. Vibration detector probes are provided at each bearing. The bearings are forced lubricated and visual oil flow gauges are supplied in the bearing bracket oil piping.

h. LUBRICATING SUPPLY SYSTEM

The generator shares a common lubrication system with the turbine. Fewer subsystems means less complexity and reduced installation costs.

i. SEAL OIL SYSTEM

The function of the seal oil system is to lubricate the seals and prevent hydrogen escaping from the genetator, without introducing air and moisture into the generator. The same oil is used in the turbine and generator bearing lubrication oil system and the gland seal oil system. Under normal operating conditions the seal oil is completely separated from the lubrication oil. Independent seal oil systems for air-side and gas-side oil eliminate the need for an oil vacuum treating unit and reduce hydrogen consumption by preventing the air-side oil which contains moisture from contacting the hydrogen gas in the generator. Part of the reliability of the system is the back-ups provided. Emergency seal oil back-up pumps, interconnected with the lubrication oil system, automatically provide continuous operation of the seal oil supply in the event that the main air side oil fails.

j. HYDROGEN GAS SYSTEM

Hydrogen pressure is maintained at the design pressure by a pressure regulator located in the hydrogen system. Continuous circulation of the hydrogen is maintained by the shaft-mounted axial blowers. The hydrogen gas system is designed for the following functions:

To provide means of safely putting hydrogen in and taking hydrogen out of the generator, using carbon dioxide as a scavenging medium.

To maintain the gas pressure in the generator at the desired level.

To continuously monitor the condition of the machine with regard to gas pressure, temperature, and purity, and to provide alarm signals in the event of abnormal conditions in the gas system. The pressence of liquid in the machine is also indicated by an alarm.





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To dry the gas and remove any water vapor which might get into the machine from the seal oil system or other sources.

To provide control to secure the system in the event of an abnormal condition.

— GAS DRYER

A gas dryer is connected across the generator fan so that gas is circulated thru the dryer whenever the machine is running.

— LIQUID DETECTORS

Float operated switches in small housings are provided under the generator frame and under the main lead box to indicate the presence of any liquid in the generator which might be due to leakage or condensation from the cooler. Openings are provided in each frame ring at the bottom of the frame so that any liquid collected will drain to these water detectors. Each detector is provided with a vent return line to the generator frame so that the drain line from the generator frame will not become air bound. Isolating valves are provided in both the vent and drain lines so that the switches can be inspected at anytime,and a drain valve is provided for the removal of any accumulated liquid.

— HYDROGEN PURITY MONITORING EQUIPMENT

The purity of the gas in the generator is determined by the use of the purity blower, the hydrogen purity electronic differential pressure transmitter, the hydrogen pressure electronic transmitter,and the hydrogen gas instrumentation package.

An induction motor, loaded very lightly so as to run at practically constant speed, drives the purity blower and circulates the gas drawn from the generator housing. Thus,the pressure developed by the purity blower varies directly with the density of the sampled gas.The hydrogen purity differential pressure transmitter measures the pressure developed by the purity blower. Gas density is dependent upon the ambient pressure and temperature as well as the purity.





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The hydrogen monitoring system combines the purity blower differential pressure and the machine gas pressure signals to provide a compensated density signal,which is a true reading of machine gas purity.

The purity indicator scale is divided into three sections. Near the center of the scale is a point marked "100% Air" . This point provides a means of calibrating the indicator without removing the gas from the generator. The upper end of the dial consists of a scale showing the percentage of carbon dioxide present in a mixture of carbon dioxide and air. This portion of the scale is used during scavenging operation when carbon dioxide is being introduced into the generator.The lower end of the dial consists of a scale indicating the percentage of hydrogen present in a mixture of hydrogen and air. It is this portion of the scale which is used during normal opration of the machine to determine the purity of the hydrogen in the generator housing.

The hydrogen purity signal, an electrical output signal, may be carried to a remotely located receiver provided with a dial similar to the purity indicator on the generator auxiliaries control enclosure.

Two switch assemblies are provided with the hydrogen monitoring system which are set to produce a "hydrogen purity high or low" alarm when the purity signal falls below exceeds predetermined limits.

— GENERATOR FAN DIFFERENTIAL PRESSURE MONITORING EQUIPMENT

An electronic differential pressure transmitter is connected directly to the generator housing and senses the pressure developed by the fan mounted on the generator rotor. The hydrogen monitoring system transmits the generator fan differential pressure signal to an indicator in the generator auxiliaries control enclosure.

This pressure can be used as a check on the purity indicator or can be used to indicate the hydrogen purity if the purity indicator is taken out of service while the generator is running.

— HYDROGEN PRESSURE MONITORING EQUIPMENT





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The electronic hydrogen pressure transmitter is connected directly to generator housing an senses the pressure within the generator. The transmitted pressure signal is used by the hydrogen monitoring system, not only to compensate the density for purity as mentioned above, but also to supply the electrical signals for the following:

( The hydrogen pressure indicator in the generator auxiliaries control enclosure.

B. A remotely located indicator with dial simialr to the previous indicator and

( High and low,pressure alarm switches located in the generator auxiliaries control enclosure.

( The high and low pressure alarm switches provide an indication when the gas pressure in the machine exceeds or goes below predetermined limits.

— HYDROGEN TEMPERATURE ALARM

A hydrogen cold gas thermostat is located in the generator to provide a source of alarm in case the temperature of the hydrogen in the generator becomes excessive.

— SUPPLY PRESSURE SWITCH AND GAUGES

All generators are equipped with a hydrogen pressure control,which has a supply pressure switch and two pressure gauges. The top gauge indicated the machine gas pressure and also the setting of the regulator on the hydrogen pressure control. The bottom gauge gives an indication of the amount of pressure available from the hydrogen supply system.

A pressure switch is located on the supply side of the hydrogen pressure control manifold and gives and alarm when the supply pressure is low. A drop in pressure at this point would mean that the available pressure from the hydrogen supply was to low, or that the regulators in the hydrogen supply are set at too low a pressure.

k. STATOR COIL WATER SYSTEM

The stator coil water system is a closed loop system having the following features:





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Circulation of high purity water thru the stator coil hollow conductors for removal of heat due to the stator coil losses.

Dissipation of heat from the high purity water. Filtering of water to remove foreign material. Demineralization of the water to control its electrical conductivity. Instrumentation and alarms to continuously monitor and advise conditions

of conductivity, flow, pressure, and temperature of water. All piping and components are made of corrosion resistant materials.

Cold water is piped thru the generator shell into a circumferential manifold in the exciter end of the generator. The cold water inlet piping is e quipped with a temperature detector for temperature monitoring and a thermostat for alarm purposes. An inline strainer is installed for startup to prevent admission of dirt into the hollow stator conductors.

Inside the generator, water flows from the inlet manifold into the coil ends thru teflon insulating tubes. Water discharging from the stator coil at the other end, is collected by teflon hoses and a discharge manifold, and then returns to the water tank.

The two inlet and discharge manifolds are interconnected at the high point with a vent line which also serves as an anti-siphoning line. This vent is continued to the water tank. The two manifolds are connected to a differential pressure gauge to indicate pressure drop across the stator coils. They are also connected to differential pressure switches for alarms for abnormal pressure drops across the stator coils. The inlet end of the water manifold is also connected to an inlet water pressure gauge and to the low pressure side of a differential pressure switch. The high pressure side of this switch is connected to the generator (gas pressure). When the generator gas pressure drops to 0.35 bar above the inlet water pressure, an alarm is actuated. l. AUXILIARY ALARMS

An alarm signal system is associated with the seal oil, stator coil water and hydrogen gas systems to indicate abnormal operating conditions. A Generator Auxiliary Control Enclosure has been supplied to indicate these alarms. A recent improvement has been made to supply the alarm signals dependent upon whether or not DEH is supplied and on the level of DEH supplied standard option. The traditionally supplied Generator Auxiliary Control Enclosure with local panel/announciator with limited contacts for





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Customer's use in addition to contact and analog signals going to DEH. DEH makes all calculations and displays on CRT under appropriate conditions.

m. HYDROGEN COOLERS Each hydrogen cooler consists of a number of finned tubes arranged within a suitable open frame structure, thus providing a layer heat transfer surface for cooling the hydrogen gas circulating within the generator. Technically a hydrogen cooler is classified as 1-2 cross flow heat exchanger. That is the hydrogen gas makes a single pass through the cooler on finned side of tubing and the cooling water makes two passes on the tubes. Generally hydrogen coolers are divided into 2 "sections", each section being an independent heat exchanger. The sections are arranged in tandem such that the hydrogen gas makes a single pass through all the tandem sections, whereas the cooling water flows in parallel in each section and makes two passes in each.

There are generally two arrangements of hydrogen coolers used in generators: one is with coolers vertically mounted; and the other is with cooler horizontally mounted. This design uses the vertical arrangement. In the vertical arrangement. there are four hydrogen coolers, mounted in the frame of the generator at four corners. Each cooler consists of two separate, tandem sections, making a total of eight sections, each of which can be isolated by valving. Each cooler is attached to the generator frame at one end only to permit expansion and contraction within the generator. The inlet water chamber, which extends beyond the generator frame, is bolted to the generator frame. A thin steel diaphragm is secured to the cooler and to the generator frame at the opposite end of the cooler. This diaphragm allows relative thermal expansion between the generator frame and the hydrogen cooler without allowing hydrogen gas to escape. The water makes two passes through each section in a counter flow manner by means of a reversing chamber at one end. The heat is transferred from the gas to the cooling water flowing through the finned tubes of the cooler. Temporary operation at reduced load is permitted with one or two of the eight cooler sections out of service. The permitted load to see the generator instruction book in detail.

n. BRUSHLESS EXCITATION SYSTEM





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Westinghouse in USA began to develop the brushless excitation system in the sixties. Since then more than 400 units have been produced. The proposed BLE excitation system was Westinghouse technology which is fully transferred to STGC.

The features of brushless excitation system:

♦ The electric power source of excitation comes from the directly driven AC exciter and permanent magnet pilot exciter to avoid system interference.

♦ Slip ring and brushes are no longer used. Thus pollution caused by carbon dust is eliminated, noise level lowered, and maintenance becomes easier.

♦ The modular structure of rectifier, fuse and etc, is easy for maintenance.

♦ Enough back up capacities are available for critical components such as the rotating diodes, firing circuit, power amplifying circuit and stable voltage source to ensure the safe operation.

♦ With better protection devices (such as over excitation, low excitation and low frequency protection) the generator can be operated at the maximum output.

♦ Internal connection: Rotating elements are solidly connected together. No outer connection is needed between the generator field and the exciter, the only outer connection being those between the stator of the AC exciter, the stator of the pilot exciter and the control circuit.

♦ With the performance of high initial response, the excitation system can reach 95% of the difference between ceiling voltage and rated excitation voltage within 0.1 second. Thus the stability of generator and power system can be raised.

♦ The field current of generator can be indirectly measured.

♦ De-excitation is realized by field inversion of the AC exciter and then open of its field connection to PMG.

2 FUEL





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2.1 Fuel characteristics

The fuel and its characteristic data is listed below.

2.1.1 Coal Analysis

PARAMETER Performance CoalWorst Coal

(for ESP & MILL)

★Proximate Analysis

Moisture(AR) 15.0% 15.0%

Ash(AR) 34.0% 46.0%

Fixed Carbon(AR) 21.0% 19.73%

Volatile matter(AR) 30% 19.27%

★Ultimate Analysis

Carbon(AR) 41.22% 31.88%

Hydrogen(AR) 2.81% 2.13%

Sulphur(AR) 0.35% 0.28%

Nitrogen(AR) 0.71% 0.59%

Oxygen (AR)(by difference) 5.90% 4.12%

Moisture(AR) 15.0% 15.0%

Gross calorific value(AR) 4000 Kcal/Kg 3150 Kcal/kg

★Grindability Index 50 50

★Typical ash analysis

Silica 58.95% 59%





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PARAMETER Performance CoalWorst Coal

(for ESP & MILL)

Alumina 28.5% 28%

Iron oxide 5.5% 6%

Titania 1.8% 2%

Phosphoric anhydride 0.7% 0.6%

Lime 1.5% 1.2%

Magnesia 1.3% 1.5%

Sulphuric anhydride 0.5% 0.6%

Alkalies (by difference) 1.25% 1.1%

Total 100% 100%

★ Ash fusion range

Initial deformation temperature 1100 deg .c 1100 deg .c

Hemispherical temperature 1300 deg .c 1250 deg .c

Fusion temperature 1400 deg .c 1400 deg .c

·AR = As Received

2.1.2 Fuel Oil

2.1.2.1 LIGHT DIESEL OIL ANALYSIS

Meets Indian Standard IS 1460-197

Analysis by Weight (percent)

-Sulfur 1.8





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-Ash 0.02

-Relative Density @ 15℃ 0.86-0.90

Pour Point (℃ max.) 12(W)/18(S)

Kinematic Viscosity (centistokes at 38℃) 2.5/15.7

Water (Volume percent) 0.10

Gross Calorific Value (kcal/kg, avg) 10,600

Flash Point (℃ min) 66

2.1.2..2 HEAVY FUEL OIL ANALYSIS

No. Heavy Furnace Oil IS-1593-71 Grade HV

Low Sulphur Heavy Stock (LSHS)

1. Total sulphur content 4.5% max 1.0% max

2. Gross calorific value (Kcal/kg) Of the order of 11,000 Of the order of 11,000

3. Flash point (min) 66℃ 93℃

4. Water content by volume (max) 1.0% 1.0%

5. Sediment by weight (max) 0.25% 0.25%

6. Asphaltene content by weight (max.) 2.5% 2.5%

7. Kinematic viscosity in centistokes at 50℃ (max) 370 500

8. Ash content by weight (max) 0.1% 0.1%

9. Acidity (inorganic) Nil Nil

10. Pour point (max) 24oC 57oC

3 COMBUSTION SYSTEM AND SELECTION OF AUXILIARY EQUIPMENT





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3.1 Boiler Fuel Consumption

The fuel consumption is about 180.2t/h (performance coal) and 230.7t/h

(worst coal) per unit at boiler maximum operation condition (BMCR). At TMCR

condition it is 166.0 t/h for performance coal and 213.2t/h for worst coal per

unit.

3.2 Design principle of Flue gas and air system & pulverized coal system Considering the high volatile matter and easy burning character of the raw

coal, medium speed mill (MSM) (positive pressure)& direct-firing pulverizing

system with cold primary air fan will be adopted based on our heat calculation

of coal pulverizing system.

3.3 System Description

3.3.1 Pulverized Coal System

Direct firing, pressurized cold primary air, pulverized coal system with MSM

will be adopted in this project. Six (6) sets of HP1003 type MSMs, electric

gravimetric coal feeders (EGCF) and raw coal bunkers will be matched with

each boiler. The output of four (4) MSMs will meet the requirement of boiler

capacity at BMCR with performance coal, and has suitable margin, the output

of five MSMs will meet the requirement of boiler capacity at BMCR with worst

coal, and has suitable margin.

Raw coal from raw coal bunker via EGCF will be pulverized and dried in the

MSM, then be separated in the MSM separator. There are four (4) pulverized

coal pipes on each separator connected to four corners of boiler burners in

the same layer. Six (6) sets of MSMs correspond to six (6) layer burners of





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each boiler. Diameter adjustable device will be placed at pulverized coal

pipes, so that the resistance of each pipe is the same.

Each MSM will be equipped with one EGCF. Inlet and outlet motor operated

coal gates with good seal of the feeder can endure the exploding pressure of

0.35MPa, and have the function of self-clean. At the outlet of the bunker there

is rod gate, and the bunker emptying chute will be equipped between the two

gates. The EGCFs have alarms of coal flow break and block, coal flow

monitor etc, so that operator can handle emergency and ensures safe

operation.

Six (6) bunkers will be set for each boiler. The capacity of series of bunkers

per each unit will be normal sufficient to provided 16 hours requirement at

boiler maximum continuous rate with worst coal firing.

System design scope will include raw coal pipe and pulverized coal pipe.

3.3.2 Flue Gas and Air System

Direct firing, pressurized cold primary air system with MSM shall be adopted

in the project. The boiler manufactured by Shanghai Boiler Works Co. Ltd

(SBWL) in China shall be of natural circulation, drum type, double pass, water

tube, direct pulverized coal tangential fired, dry bottom, single reheat, balance

draft, and each boiler will be equipped with two (2) axial flow forced draft fans

(FDF) with adjustable moving-blade, three (3) centrifugal induced draft fans

(IDF) with hydraulic coupling, two (2) centrifugal primary air fans (PAF) and

two (2) sealing air fans. During operation, pressurized air shall be forced into

furnace. Fuel gas from the furnace shall be induced to atmosphere.

Lube oil system (with 2x100% capacity pumps, filters, and associated piping/

accessories) is provided wherever forced lubrication is envisaged for each of





115

the above fans.

Online vibration monitoring system and bearing metal temperature

measurement system shall be provided for all fans and their drive motors

3.3.2.1 Primary air system

Main function of the system is to feed pulverized coal and primary hot air

heated by air preheater to MSMs. Primary hot air will be acted as dry medium,

and cold primary air to MSMs (boosted by sealing air fan) and EGCFs will be

acted as seal medium. The inlet vanes of centrifugal primary air fan can adjust

air flow and pressure automatically.

Primary air will be heated in air preheater, and be sent to MSMs via common

manifold. Primary air damper will be placed at air preheater outlet. When air

preheater failure happen, the damper will be closed.

Pressurized cold air from PAFs will be regarded as regulating temperature for

MSMs and sealing air for belt feeders. The former will be mixed with hot

primary air. Mixed air can meet the temperature requirement of coal dried in

the MSM and pulverized coal at the MSM outlet.

When one MSM failure happens and shuts down, the corresponding

pneumatic damper on primary hot air duct shall be closed immediately. To

avoid primary hot air enter into the duct of primary cold air, motorized damper

on the cold duct will be also closed immediately. Mixed air flow measurer will

be installed on the mixed duct.

The air velocity in air ducts will be 10-12m/s for cold air and 15-25m/s for hot

air.





116

3.3.2.2 Secondary air system

The system shall provide air for furnace combustion. Cold air from FDFs shall

be forced into trisector regenerative air preheater through the steam coil air

heater which is located in the bypass duct, and hot air shall be sent into

secondary air box and be distributed to furnace for combustion.

Two (2) FDFs will be equipped for each boiler. Cold air liaison duct, which

connect two ducts between FDFs downstream and steam coil air heater

upstream will be set, and hot air liaison duct arranged at air preheater outlet.

Secondary hot air box is special design, when one FDF out of operation, hot

air flow to the boiler four corners will be almost equal, so that stable

combusting and reasonable temperature field in the furnace can be ensured,

and will reduce temperature deviation at two sides of boiler.

Damper and air flow measurer shall be placed at hot air duct of air preheater

outlet, when air preheater is out of operation, the damper shall be closed

automatically.

Two trisector regenerative air preheater will be equipped which primary and

secondary air will be heated in it. Also, water washing system and fire

protection system and soot blowing system will be equipped for GAH.

Forced lubrication oil system (with 2x100% capacity pumps, filters, and

associated piping/ accessories) is provided for air preheater.

The air velocity in air ducts will be 10-12m/s for cold air and 15-25 m/s for hot

air.





117

3.3.2.3 Sealing air system

2x100% centrifugal sealing air fans will be equipped in the system, one in

operation and another standby. Sealing air from cold primary air manifold will

be sent into MSMs via seal fan boost. At sealing air fans inlet, air filters and

motorized dampers will be arranged, when one fan is in operation, another’s

inlet damper is closed. If pressure difference of the filter inlet & outlet reaches

to setting value, the filter will clean itself via pressure difference.

3.3.2.4 Flue gas system

The system consists of two ESP and three centrifugal induced draft fans (IDF)

with hydraulic coupling.

Flue gas from economizer will enter into two (2) air preheater, one isolating

damper will set at the inlet of each air preheater. When emergency happens

to one air preheater, the respective damper will be closed. During air

preheater start up or shut down, the damper will be opened or closed.

Flue gas from air preheater enters into ESP with double path, seven electric-

fileds. Each boiler will be equipped with two ESPs. Isolating Guillotine type

gates will be placed at ESP inlet & outlet. Flue gas via ESP, ID Fan & chimney

will be vented into atmosphere.

Isolating dampers will be placed at ID Fan inlet & outlet. When ID Fan failure

happens, it will be overhauled after the dampers closed. During ID Fans

starting up or shutting down, the damper will be opened or closed.

Three (3) ID fans are 2 in operation and 1 standby.





118

The fuel gas velocity in gas ducts will be 10-15m/s.

The range of flue gas velocity in flue path in convective heat transfer areas

within the boiler is maximum 10m/s and maximum 9m/s through the air

preheater.

3.4 Calculation results

The results are based on performance coal for one boiler at MCR and it can

adapt the characteristic data range of the coal.

3.4.1 Pulverized coal system

NO. Item Symbol UnitValue

(For one unit)

1 Boiler coal consumption (BMCR) Bg t/h 180.2

2 Hard grove grindability index HGI / 50

3 Maximum Size of raw coal at inlet of mill dmax mm <32

4 Fineness of coal powder mesh 200 % 70

5 Medium speed mill quantity（operate/install） / set 4/6

6 Medium speed mill operating output BF1 t/h 45.05

7 Medium speed mill max output BSJ t/h 60

8 Medium speed mill rated inlet air flow Qv t/h 96.9

9 Primary air temperature at outlet of GAH tkr °C 300

10 Air temperature at inlet of medium speed mill t1 °C 241





119

NO. Item Symbol UnitValue

(For one unit)

11 Ratio of air and coal mass at inlet of medium speed mill / kg/kg 2.15

12 Temperature at outlet of medium speed mill tm °C 77

13 Mill reject rate % 1.025

14 Effective volume of each raw coal bunker m3 945

15 Duration for boiler burning at BMCR condition with worst coal– bunker storage h 16.2

3.4.2 Flue gas and air system

NO. Item (one unit) Symbol Unit Value

(For one unit)

1 Theoretical air volume for combustion V° Nm3/kg 4.2243

2 Volume of combustion result at the outlet of furnace V

°y Nm3/kg 5.7535

3 Air temperature at inlet of GAH(PA/SA) t 'kg °C 35/30

4 Air temperature at outlet of GAH（PA/SA） tⅠky/tⅡky °C 300/310

5 Flue gas temperature at outlet of GAH ( corrected) tpy °C 136

6 Flue gas volume at outlet of GAH Vy m3/s 475.3

7 Flue gas excess air coefficient at outlet of GAH Apy / 1.344

3.5 Major Auxiliary Equipments Selection





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3.5.1 Pulverized coal system

Six (6) medium speed mills and six (6) coal feeders will be furnished for each

boiler. These will be of sufficient capacity to attain the MCR of the steam

generator when boiler firing any specified coal with any one (or two) mill out of

service. In other words, when firing the performance coal, four (4) mills will be

in operation and two (2) will be standby, and when firing the worst coal, five (5)

mills will be in operation and one (1) will be standby, together with its

associated feeders. Because of the positive pressure in the mill and coal

feeder, two (2) sealing air fan are furnished to supply the sealing air to avoid

the powder leaking.

The maximum capacity of mill shall be 60 TPH corresponding to 50 HGI, 70%

through 200 mesh and moisture content 15 %.

NO. Item Unit Value

(design coal)

1 Type of MSM HP1003

2 Grindability Index HGI 50

3 Moisture(AR) 15%

4 Powder fineness mesh 200 70%

5 Maximum capacity of mill(HGI=50, 70% through 200 mesh)

t/h 60

6 Minimum capacity of mill t/h 15

7 Mill loading % 76

8 Max. air flow rate t/h 107.2

9 Max. resistance kPa 4.0





121

NO. Item Unit Value

(design coal)

10 Inlet temperature of mill ℃ 241

11 Outlet temperature of mill ℃ 77

12 Inlet air/ inlet coal Kg/Kg 2.15

13 Rotary speed r/min 33.01

14 Shaft power of mill (BMCR) KW 366

15 Rated power of motor KW 560

16 Voltage KV 6.6

17 Gravimetric coal feeder t/h 60

18 Coal feed distance (from feeder inlet to feeder outlet) mm 2200

3.5.2 Flue gas and air system

Each boiler will be furnished with two (2) sets of primary air fan，two (2) sets

of forced draft fan and three (3) sets of induced draft fan. These fans will be

designed for outdoor installation. Under normal operation, all of PA Fans and

FD Fans will be in operation, while two (2) of three (3) ID Fans will be in

operation.

The fans sizing are based on the flow and total pressure at BMCR conditions

with a specific margin as below:

PAF, FDF& IDF SIZING DATA SHEET

Design coal worst coal

Sl. No. Segment/ Location sizing

capacity (TB)

two fans operation with 100% BMCR

one fan operation with 60% BMCR



unit

A PA fan sizing





122



capacity (TB)





unit

calculation

1 Air pressure drops

1.1 PA Fan inlet duct (include the silencer) 248.1 432.5 270.5 517.7 Pa

1.2

Duct & dampers from PA Fan outlet to RAPH inlet 457.6 794 679.9 1316 Pa

1.3

Duct & Dampers from SCAPH to RAPH ( if SCAPH envisaged) NA NA NA NA

1.4 Thru RAPH air side 800 1047 800 1570 Pa

1.5

Duct & Dampers from RAPH outlet to pulverizer 1178.6 1882.8 1638.3 2671.5 Pa

1.6 Thru pulverizer 3500 3280 3600 3180 Pa

1.7

Duct & Dampers from pulverizer outlet to coal burner 4422 4089.6 4553 3948.9 Pa

1.8

Between inlet & throat of air flow measuring device 0 0 0 0 Pa

1.9

Unrecoverable loss across air flow measuring device 0 0 0 0 Pa

1.10 Burner 500 500 500 500 Pa

1.11 furnace negative pressure 40 40 40 40 Pa

1.12 Total loss through system 11067 11986 12003 13665 Pa

2 Air flow calculation 2.1 Coal firing 180.2 117.7 230.7 150.7 t/h 2.2 No of mill in operation 4 3 5 4

2.3

coal flow per mill (inlet/outlet), considering 1.025% mill reject

45.52/45.05

39.75/39.33

46.63/46.14

38.18/37.78 t/h

2.4 HGI 50 50 50 50





123



capacity (TB)





unit

2.5 moisture in coal 15 15 15 15 %

2.6 finess through 200 mesh 70 80 70 80 %

2.7 design mill outlet temperature 77 77 77 77 ℃

2.8 ambient temperature 47 47 47 47 ℃

2.9 cold air density 1.06 1.06 1.06 1.06 kg/m3

2.10 air temperature at outlet of APH 300 259 301 262 ℃

2.11 air coal ratio at mill inlet for transportation of coal (per kg coal)

2.15 2.47 2.12 2.53 kg/kg

2.12 air flow at inlet of each mill 26.92 26.94 27.16 26.56 kg/s

2.13 total air flow to mills 387648 290952 488880 382464 kg/h2.14 mill inlet temperature 241 223 250 220 ℃

2.15 Tempering air for each pulverizer 5.48 3.5 4.61 4.18 kg/s

2.16 total tempering air to mills 78912 37800 82980 60192 kg/h

2.17 air flow at the outlet of APH 308671 253208 405859 322249 kg/h

2.18 APH leakage 76680 36360 82440 36720 kg/h

2.19 air flow at the inlet of APH 385351 289568 488299 358969 kg/h

2.20 feeder sealing total air flow 3084 2313 3855 3084 kg/h

2.21 mills sealing total air flow 30456 15228 30456 20304 kg/h

2.22 total air flow at outlet of PA fan 497803 344909 605590 442549 kg/h

2.23 No of operation fan 2 1 2 1

2.24 PA Fan outlet flow for each fan 65.2 90.4 79.3 116

m3/s

3 PA fan sizing

3.1 PA Fan flow 99.2 m3/s

3.2 flow margin 25 based on worst coal 100%BMCR condition %





124



capacity (TB)





unit

3.3 PA fan pressure sizing 16804 Pa 3.4 pressure margin 40 based on worst coal 100%BMCR condition % 3.5 fan efficiency 85 % 3.6 fan shaft power 1974.2 KW 3.7 motor rating 2500 KW 3.8 fan speed 1480 rpm 3.9 Power supply 50 Hz

B FD fan sizing calculation

1 Air pressure drops (after corrected)

1.1 FD Fan inlet duct (include the silencer) 326.55 341.5 317.03 321.2 Pa

1.2 Duct & Dampers from FD Fan outlet to RAPH 453.3 576.07 408 459.8 Pa

1.3 Thru RAPH air side 800 1071 800 748 Pa

1.4

Duct & Dampers from RAPH to furnace windbox 764.6 539.24 539.2 300.65 Pa

1.6

Between inlet & throat of air flow measuring device 0 0 0 0 Pa

1.7

Unrecoverable loss across air flow measuring deivce 0 0 0 0 Pa

1.8 burner pressure drop (second air) 1100 1000 1100 1000 Pa


1.10 Total loss through system 3404.4 3487.9 3124.2 2789.6 Pa

2 Air flow calculation 2.1 Coal firing 180.2 117.7 230.7 150.7 t/h





125



capacity (TB)





unit


2.3 cold air density 1.06 1.06 1.06 1.06 kg/m3

2.4 theoretic air flow (per kg coal) 4.2243 4.2243 3.2707 3.2707

nm3/kg

2.5 excess air at outlet of furnace (by volume) 1.25 1.26 1.25 1.25

2.6 total air flow at mill outlet 111.6 83.8 140.7 110.2 kg/s

2.7

total combusion air flow at the inlet of furnace (considering 20% excess air at furnace inlet) 323.3 211.6 320.1 208 kg/s

2.8 air temperature at outlet of APH 310 273 314 279 ℃

2.9 air flow at the outlet of APH 211.6 127.8 179.4 97.8 kg/s

2.10 APH leakage 5.4 3.3 4.5 3.2 kg/s

2.11 air flow at the inlet of APH 217 131.1 183.9 101 kg/s


2.13 FD Fan outlet flow for each fan 102.3 123.7 86.7 95.2

m3/s

3 FD fan sizing

3.1 FD Fan flow 122.8 m3/s

3.2 flow margin 20 based on design coal 100%BMCR condition ％

3.3 FD fan pressure sizing 4426 Pa 3.4 pressure margin 30 based on design coal 100%BMCR condition % 3.5 fan efficiency 81.28 % 3.6 fan shaft power 678 KW 3.7 motor rating 800 KW 3.8 fan speed 1470 rpm





126



capacity (TB)





unit

3.9 Power supply 50 Hz

C ID fan sizing calculation

1 Flue Gas pressure & Pressure Drops

1.1 Furnace Pressure (Suction)

1.2 Drop across Superheater

1.3 Drop across Reheater

1.4 Drop across economizer

1.5 Drop across RAPH ( Gas side)

Total: Max. 2400

Total: max. 3570

Total: Max. 2400

Total: max. 3582

Pa

1.6 Drop across ESP 245 245 245 245 Pa

1.7 Drop thru Ducts & Dampers from

1.7.1 RAPH outlet to ESP Inlet 226.4 129.7 232.2 131.1 Pa

1.7.2 ESP Outlet to ID fan inlet 357.5 436.9 345.5 431.6 Pa

1.7.3

ID Fan outlet to stack outlet (include stack effect of chimney) 336.4 93 314 60 Pa


1.9 Total drop through system 3605.4 4514.5 3576.7 4489.6 Pa

2 Flue gas flow calculation

2.1 theoretic flue gas flow (per kg coal) 4.6804 4.6804 3.6605 3.6605

nm3/kg

2.2 Flue gas at RAPH Inlet 666 408.1 666 405.6 m3/s

2.3 Flue gas at RAPH Outlet 475.3 297.9 478.9 299

m3/s

2.4 total No of fans 3 3 3 3





127



capacity (TB)





unit


2.6 flue gas temperature at the outlet of APH (corrected) 136 128 140 133 ℃

2.7 EA at the outlet of APH 1.35 1.328 1.35 1.317

2.8 gas flow at the outlet of APH 475.3 297.9 478.9 299

m3/s

2.9 EA at the inlet of ESP 1.38 1.338 1.38 1.327

2.10 gas flow at the inlet of ESP 482.9 299.6 486.4 300.6

m3/s

2.11 EA at the outlet of ESP 1.39 1.348 1.39 1.337

2.12 gas flow at the oltlet of ESP 485.5 301 488.9 302

m3/s

2.13 EA at the inlet of ID fan 1.42 1.348 1.42 1.337

2.14 gas flow at the inlet of ID fan 493.1 301 496.4 302

m3/s

2.15 gas temperature at the inlet of ID fan 131.6 126.8 135.4 131.7

2.16 gas density 0.8422 0.8469 0.8319 0.8341 kg/m3


2.18 ID Fan inlet flue Gas flow per fan 247 301 248 302

m3/s

3 ID fan sizing

3.1 ID Fan flow 303.2 m3/s

3.2 flow margin (considering 10 deg.C temperature margin) 20 based on design coal 100%BMCR condition %

3.3 ID fan pressure sizing 4787 Pa 3.4 pressure margin 30 based on design coal 100%BMCR condition % 3.5 fan efficiency 87.9 89.3 87.4 89.3 87.4 % 3.6 fan shaft power 1747.8 1051.7 1653.6 1047.9 1649.6 KW 3.7 motor rating 2240 KW 3.8 fan speed 950 rpm





128



capacity (TB)





unit

3.10 Power supply 50 Hz

D Excess Air

1.1 At burners 20 19 20 18 %

1.2 At Econimizer Outlet 25 26 25 25 %

1.3 At RAPH Outlet 35 32.8 35 31.7 %

1.4 At ID Fan inlet 42 34.2 42 33.7 %

For PA fans, FD fans and ID fans, the bearing of rotor will be ball bearing,

and this technology is from TLT, Germany. The bearing for the fans will be

imported from SKF or FAG. The blade of PA fans is flat plate blade, which is

suitable for low flux and high pressure media. Materials adopted for fans as

below:

component FD fans PA fans ID fans

Fan housing and inlet box Q235-A Q235-A Q235-A

Shaft 42CrMo 35CrMo 35CrMo

Impeller hub 15MnV - -

Impeller blade HF-1(TLT standard) - -

Two (2) electrostatic precipitators (double-pass, seven electric field) is

equipped for each boiler, The ESP remove particulate from the boiler flue gas

to achieve a guaranteed outlet emission of less than 70 mg/Nm3 with (n-1)





129

fields in each stream of ESP in operation when fired with design coal and flue

gas flow rates from 25 to 110 percent of maximum continuous rating (MCR),

and less than 100 mg/Nm3 when fired with worst coal and flue gas flow rates

from 25 to 110 percent of MCR with one field out of service. The collection

efficiency of ESP with (n-1) field of each stream in service is not less than

99.94% when firing worst coal. Air in leakage through ESP of the total gas

flow is less than 1%.

No Electrostatic precipitator Unit Value

(design coal)

Value

(worst coal)

1 Double-pass, 7 electric fields

2 Flue gas flow (including 10% marginand 10℃ margin)

m3/h/set 979669 986524

3 flue gas temperature(including 10 ℃margin) ℃ 144 148

4 Inlet dust concentration g/Nm3 45.8 79.4

5 Outlet dust concentration mg/Nm3 20 23.8

6 Specific collecting area (Based on 400 mm spacing)

m2/m3/sec

220.7 (294.3, with 300 spacing)

7 Max Pressure drop across ESP at the guarantee (operating) point flow

mmwc 25 25

8 Efficiency of ESP

A With (n-1) field in service % 99.94 99.94

B With n field in service % 99.96 99.97

3.5.3 Boiler Igniting and Fire Stabilizing Oil System

The oil of the boiler igniting is diesel oil and fire stabilizing is HFO/LSHS, and





130

the boiler ignition mode is high-energy ignition.

The system will be furnished with two 200m3 HFO/LSHS daily oil tank, one

50m3 LDO daily tank for both units, Two motor-driven HFO oil transfer pumps

per unit (one operation and another standby), two motor-driven LDO oil

transfer pumps per unit and other associated equipments per unit. They are

located in the daily oil tank area.

HFO/LSHS screw type pump: Q=30t/h (2x100%)

Motor-driven LDO feed pump (centrifugal type): Q=10t/h (2x100%).

4 THERMAL SYSTEM AND SELECTION OF AUXILIARY EQUIPMENT

4.1 Design principle of Thermal System

The thermal system will ensure the security, economy and flexibility of the unit.

All of the systems are unit system except auxiliary steam system.

4.2 System Description 4.2.1 Main steam, reheat steam and bypass system

The pipe sizing shall be as per ASME B31.1 and velocities shall be limited to

the values mentioned in specification.

In addition to above, pressure drop in main steam line shall not be more than

90% of the allowable pressure differential between superheater outlet header

and HP turbine inlet valves at BMCR. Similarly, combined pressure drop in

cold and hot reheat piping will not exceed 90% of the pressure differential





131

between HP turbine exhaust and IP turbine inlet valves minus the reheater

drop. The pressure drop in the complete reheat line from HPT exhaust to IPT

inlet shall not be more than 10% of the pressure at HPT exhaust.

4.2.1.1 Main steam system

Main steam system will convey superheated steam from the superheater

outlet to the HP main steam stop valve. Main steam is unit system. Main

steam flow through single pipe from outlet of boiler superheater header, and

then divided into two branches and connects to left and right main HP steam

stop valve separately.

1) A Motor operated Main steam isolation valve with motor operated integral

bypass valve is set on main steam pipe near boiler outlet for boiler hydraulic

test as well as for normal operation.

2) One branch leads to gland steam system as HP steam source when normal

gland steam pressure is too low and one branch leads to turbine casing steam

heating header as heating steam source before turbine startup, another

branch leads to auxiliary steam header when the cold reheat pipe pressure is

inadequate or not available..

3) To prevent water from entering turbine, drain system is set to discharge

condensate water of main steam pipe during warm-up and shut-down. Drain

points are set at the lowest points on main steam pipe. A pneumatic drain

valve and a hand-operated valve are set on drain pipe of each drain point.

Drain water is led to drain flash tank. All drains including drain pot shall be

checked with respect to ASME TDP guideline for turbine water damage

protection.





132

4) Two spring safety valves, one solenoid PCV and two motorized venting

valves are set on main steam pipe near superheater outlet.

4.2.1.2 Reheat steam system

Reheat steam system will convey cold-reheat steam from HP casing exhaust

spout to inlet of boiler reheater and convey hot-reheat steam from outlet of

reheater to IP main steam stop valve. Reheat steam is unit system.

One cold reheat steam pipe is connected from turbine HP casing exhaust pipe

and divided into two pipes in front of boiler, then connect to two inlets of boiler

reheater header separately.

Two hot reheat steam pipes are connected at two end of outlet header of

boiler reheater and join one pipe at front of boiler, and divided into two pipes

again in front of turbine, then connect with left and right IP steam stop valve.

1) To prevent steam from flowing back into turbine, one pneumatic check

valves is provided on cold-reheat pipes;

2) Desuperheaters are set on the pipe of reheater inlet, to adjust steam

temperature of reheater outlet under emergency condition. Desuperheating

water come from intermediate stage extraction of BFP.

3) Hydraulic test valve is set on each cold-reheat steam pipe near reheater

inlet to prevent pressurized water entering cold-reheat pipe during hydraulic

test of boiler.

4) To prevent water entering turbine, one drain pot is set on the pipe near HP

casing exhaust spout. A pneumatic valve is set on drain pipe to automatically

control drain water into condenser in time.





133

5) Two spring safety valves are set on each cold-reheat pipe near reheater

inlet.

6) A hydraulic test valve is set on each hot-reheat pipe near reheater outlet to

make sure that the pressurized water is stopped during boiler reheater

hydraulic test and can’t enter into the hot reheat pipes.

7) One pipe connecting the outlet of HP bypass valve and the inlet of LP

bypass valve is set to form the heat circuit by pressure difference which is

able to warm the outlet of HP bypass valve and pipe, the inlet of LP bypass

valve and pipe.

8) Spring safety valves are set on hot-reheat pipe near reheater outlet, its set

pressure is lower than the spring safety valve on cold-reheat steam pipe near

reheater inlet, so the former will open before the later when over pressure

happens to ensure enough steam through reheater and avoid over heating of

reheater.

9) Drain points are set on hot-reheat steam pipe branches after tee to remove

condensate water during startup and shut-down. Drain water enters into

condenser. A pneumatic valve and a hand-operated valve are set on each

drain pipe.

4.2.1.3 Bypass steam system

The capacity of HP bypass system is 60% BMCR. High-pressure (HP) bypass

stations shall be preferably DRE type CCI make HP & LP bypass valves shall

be of angle type and combined throttle cum spray valve. This system can

convey main steam bypass HP-casing to cold-reheat piping and convey hot-





134

reheat steam bypass IP&LP-casing to condenser when unit startup, shutdown

and other various operating modes. TG set is capable of operating on house

load during sudden total export load throw-off and in the event of turbine trip

and generator breaker open HP-LP bypass system will open automatically.

The leakage class of valves shall be minimum class V. For Spray valve Trim

exit velocity of liquid shall not exceed 30m/s.

1) Desuperheating water of HP bypass is from feed water system, one control

valve and one stop valve are set on desuperheating water pipe.

2) LP-bypass system is connected with HP-bypass system in series to

achieve the function of whole bypass system.

3) One drain pot is set at the lowest point downstream of LP-bypass valve. A

pneumatic valve is set on each drain pipe.

4) Desuperheating water of LP-bypass is from condensate water system.

Table 4.2.1

Item Name Diameter Material Maximum velocity as

allowable in table 5.10-1 (m/min)

1 Main steam pipe ID368.3×41.275 A335P91 5300

ID273.05x30 A335P91 3700

2 Hot reheated steam pipe ID635X31 A335P22 5600

ID508×24.8 A335P22 5600

3 Cold reheated steam pipe φ812.8×22.225 A106B 5600

φ558.8×16 A106B 5600





135

4.2.2 Feed-water system

HP feedwater system is unit system. The function of this system is to pump

deaerated feed-water from deaerator water tank to inlet header of boiler

economizer. Feed water is heated to the given temperature in HP-heaters by

turbine extraction steam to improve heat efficiency of the units. There are

three 50% capability motorized variable speed feedwater pump in this system,

during normal operation, two pumps work and one pump is standby.

The main boiler feed pump and booster boiler feed pump shall be manufac-

tured of following or superior materials

a) Casing barrel: Forged carbon steel ASTM A266 C1 I or 1-1/4 chromium

STM A217 WC6

b) Discharge head: Forged carbon steel ASTM A266 Cl I or carbon steel plate

ASTM A515 Gr.55

c) Casing: SS ASTM A743 Gr.A-6NM or CA-15 (booster boiler feed pump)

d) Pressure retaining bolting:

i) External: Alloy steel ASTM A193 Gr.B5,B7, or B7M

ii) Internal: SS ASTM A193 Gr.B8

e) Pressure retaining nuts:

i) External: Alloy steel ASTM A194 Gr.1,2, 2H or 7





136

ii) Internal: SS ASTM A194 Gr.8

f) Shaf: SS ASTM A276 Type 410 Condition T.

g) Impeller: SS ASTM A743 Gr.CA-6NM or CA-15

h) Wearing rings, throttle bushings, shaft sleeves:

i) Stationary: SS ASTM A582 Type 416 Condition H parts

ii) Rotating: SS ASTM A582 Type 416. parts

High-pressure sealing joint surfaces on the forged steel barrel and head, and

areas subject to high water velocity, shall be lined with an overlay of AWS

A5.9, filler metal Type ER309, stainless steel deposited by welding.

The full flow regulating valve is located in the major pipe of feed water control

station, which shall be used in conjunction with the variable speed drive to

provide adequate flow control. A full flow bypass line with adjustable orifice

and motorized inching will be provided also.

30% BMCR bypass control valve is provided for low load operation and

startup.

There are three HP heaters. HP heaters are horizontal type. Bypass piping

will be provided to divert feedwater flow around any of the high-pressure

heater for heater isolation of the respective each unit. All bypass and isolation

valves will be motor operated.

Feedwater system can be divided into three parts: LP feedwater, IP feedwater,





137

and HP feedwater pipes.

1) LP feedwater pipes

Pipes between the outlets of feedwater tank and the inlets of booster pumps

are called “LP feedwater pipes”. There are motorized valve and strainer on

each pipe. When startup, the strainer can separate the welding slag,

impurities etc., which were accumulated in feedwater tank, and LP feedwater

pipes during erection and maintenance to protect feedwater booster pumps.

2) IP feedwater pipes

Pipes between the outlets of booster pumps and the inlets of feedwater

pumps are called “IP feedwater pipes”. Each pipe has a flow metering nozzle

to measure the feedwater flow at the inlet of feedwater pump in order to

control opening and closing of minimum flow unit at the outlet of feedwater

pump. There are also filters in these pipes in order to protect feedwater

pumps.

3) HP feedwater pipes

Pipes between the outlets of feedwater pumps and inlet header of boiler

economizer are called “HP feedwater pipes”, which pass through HP heaters.

There are one check valve and one motorized gate valve at the outlet of each

feedwater pump. In order to prevent cavitation of booster pump, one

recirculation pipe is extracted from the feedwater pipe and connected to the

deaerator which has one minimum flow unit including a pneumatic control

valve, two manual valves and one check valve. Signal of the minimum flow

unit comes from the flow metering nozzle at the outlet of booster pipe. Each





138

feedwater pump has a recirculation pipe which is connected to deaerator.

The interstage extractions from each feedwater pump are collected together

and flow to the reheater attemperator as emergency desuperheating water to

adjust steam temperature of reheater. Superheater and Reheater spray at

100% TMCR condition shall be Max. 6% of main steam flow & Max. 3% of

reheat flow within the specified range of coal and entire operating range

One pipe is branched from outlet manifold of feedwater pumps and connected

to boiler superheater primary and secondary spray attemperator. Another pipe

is branched for HP bypass control valve. The former adjust superheating

steam temperature and the latter adjust main steam temperature to cold

reheat steam system.

The feedwater control station is located between outlet of HP heaters and inlet

header of boiler economizer.

The full flow regulating valve is located in the major pipe of feed water control

station, and a full flow bypass line with adjustable orifice and motorized

inching will be provided also. One check valve is located at inlet pipe of

economizer.

The capacity of bypass is 30% rated feedwater flow which adjusts feedwater

flow when unit startup and low load operation.

One pipe is branched from the economizer inlet heater to drum as the

economizer recirculating water pipe.

Table 4.2.2





139

Item Name Diameter Material Range of velocity(m/s)

1 HP feed water common pipe φ355.6×30 WB36 2-6

2 HP feed water branch pipe φ244.5x20 WB36 2-6

4.2.3 Extraction steam system

The system extracts steam from steam turbine to specified heating device and

increases the temperature of condensate water and feed-water so as to raise

thermal efficiency of the power plant.

There are 8 stages non-adjustable extraction of the steam turbine. Extraction

No.8&7&6 supply steam to three (3) HP heaters, extraction No.5 supplies

steam to deaerator. Extraction No.4&3&2&1 supply steam to four (4) LP

heaters. LP heaters No.2 and No.1 are combined heaters which are located at

neck of condenser.

Power assisted check valve and motor-driven isolation valve are set in each

extraction pipe except No2&1 extraction pipes. To prevent condensate water

entering into steam turbine to harm it during startup, shutdown & low load,

drain water pipe is set at the low point of each extraction pipe, near the valves.

4.2.4 Condensate water system

The system conveys condensate water from hot well of condenser to

deaerator through polishing unit, gland steam condenser and four LP heaters

to ensure safe operation and enhance circulation heat efficiency. Beside these,

the system also provides desuperheating water, make-up cooling water and

other miscellaneous water requirements.

The system is unit system. There are three (3) 50% capability vertical





140

Condensate extraction pumps and one condensate polishing unit in the

system.

Main control valve, auxiliary control valve and their bypass valve are set on

condensate water pipe before No.1 LP heater to ensure water level control of

deaerator under all kinds of condition.

Recirculation pipe at the gland steam condenser outlet pipe is set for the

minimum flow when Condensate extraction pump is startup or the unit runs at

the low load. One water discharge pipe branches from No.4 LP header outlet

pipe is set to discharge unqualified water during startup.

Return water pipe to condenser make-up water tank (surge tank) from the

outlet of polishing plant is set for collecting water when the condenser hot well

water level is high.

There are branches at the low pressure desuperheating water pipe such as

desuperheating water pipe to fuel oil sweeping steam desuperheater turbine

gland steam desuperheater, LP-bypass desuperheater, third-stage pressure

and temperature reducer, LP casing spray, HP emergency drain flash tank;

and also the make-up water pipe of closed circuit cooling water expansion

tank.

Pipe is set to generator stator cooling water tank and vacuum pump from

condensate water.

4.2.5 Heater drains and vents system

The functions of the system is recovering condensed water from heating

steam of each HP heater and overflow & drain water of the deaerator,

recovering condensed water of LP heater and gland steam condenser,

removing non-condensable gas in HP heaters, LP heaters and deaerator. The





141

normal cascade HP heater drain pipes from No.8, No.7 and No.6 HP heater to

deaerator, LP heater drain pipes from No.4,No.3,No.2 and No.1 LP heater to

condenser. Emergency drain pipe from each HP heater to HP emergency

drain flash tank, and LP heaters to condenser. Non-condensable gas pipes

from each HP heaters to deaerator and from each LP heaters to condenser

and from deaerator vent to atmosphere. Over flow pipe will maintain normal

water level of feed-water tank and discharge pipe can empty water in case of

maintenance. Control valve is designed in each drain pipe to control water

level.

Normal drain water from HP heaters cascade to deaerator. Emergency drain

pipes are set for each heater and respectively led to HP emergency drain

flash tank in order to ensure smooth drain and keep normal level in case that

high water level in HP heaters appears or HP heater is out of service.

Normal drain water from LP heaters cascade to condenser; Pipes for

emergency drain water of each LP heater can ensure smooth drain to

condenser when water level in LP heater is high or at low load or its

downstream LP heater(s) is (are) out of service.

Control valve is designed in each drain pipe of HP&LP heaters to control

water level.

Multi-stage water sealing device is set in the drain piping of gland steam

condenser to ensure smooth drain to main condenser in all operating

conditions.

4.2.6 Auxiliary steam system

Auxiliary steam system provide steam to deaerator when start-up, low-load

and trip, provide steam to boiler bottom heating, provide steam to turbine





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gland steam system when start-up and standby, provide steam to soot-blower

when air preheater start-up, and provide steam to steam air heater and fuel oil

system.

Auxiliary steam is taken from cold reheat pipe at normal operation. During unit

startup, shutdown and when cold reheat pipe pressure is inadequate, the

steam is taken from main steam pipe. When the unit 1 start up, start-up steam

will be provided. There is a interconnection of auxiliary steam headers

between the two units, so the auxiliary steam can be provided when one unit

is startup and another is in service. Steam header has continuous drain pipes,

it can drain condensed water of header to condenser.

One auxiliary steam header is provided for each unit. The pressure of auxiliary

steam header is about 1.20MPa and temperature is about 320 0C in normal

operation. Two safety valves are set on the header with different pressure

setting.

The source of auxiliary steam come from cold reheat steam pipe at normal

condition and main steam pipe when unit startup, shutdown or cold reheat

pipe pressure is inadequate. However if steam is required for pre

commissioning/ commissioning of first unit, auxiliary steam source shall be

arranged.

4.2.7 Vacuum system

The function of this system is extracting the non-condensable gas from

condenser and maintain rated vacuum in condenser during normal operating

condition. The vacuum will be break to protect turbine during emergency. Two

vacuum pumps are set in this system. Before unit startup, two pumps will

operate in parallel to establish vacuum as fast as possible (25 minutes).





143

Under normal operation, one pump is in operation and another is standby.

Mixture of steam and air is extracted from condenser. Uncondensed gas

exhaust to atmosphere.

There is one vacuum breaker pipe at neck of condenser. During the unit load

rejection, air admission valve will be opening to break vacuum in condenser

and decrease rotating speed of turbine, then shorten time of turning by inertia

to protect turbine. This will be used only in emergency case.

4.2.8 Condenser tube cleaning system

Debris filters and condenser on load tube cleaning system are provided before

each circulating water inlet to condenser. The complete condenser tube

cleaning system shall be provided for each pass of condenser (Total two sets

per unit) each set comprising of one rubber ball recirculating pump, one ball

screen and one ball collector and other accessories including common PLC

for two sets.

4.2.9 Closed cycle DM water system

Closed cooling water shall be used to turbine auxiliary equipments and boiler

auxiliary equipments such as generator hydrogen cooler, turbine lube oil

cooler, generator stator water cooler, BFP motor cooler, the bearing of

equipments, etc

The closed cooling water for auxiliary equipments is demineralized water

Chemical department will guarantee the water quality. The demineralized

water is pumped by the closed cooling water pumps and is sent to the heat

exchanger in which the demineralized water is cooled by the Aux. cooling





144

water. Demineralized water will be sent to the equipments and return to the

inlet of the cooling water pumps. An expansion water tank with volume 10m3

is set to meet the needs of volume change of cooling water caused by water

temperature. The water tank will be arranged at a high place to gives the

closed cooling water pump sufficient NPSH. Make-up water of the system is

from outlet of condensate water pump in normal condition and from

condensate make-up water system in emergency condition. The make-up

water is led to expansion water tank with control valve for water tank level set

in the pipe.

4.2.10 Boiler blowdown and drain system

1) Continuous blowdown system

Drum will continuously blowdown some unqualified boiler water to continuous

blowdown tank to separate steam and water, steam flow into deaerator and

water is discharged to intermittent blowdown flash tank. When continuous

blowdown flash tank is failure during operation, blowdown water will flow

through bypass to intermittent blowdown flash tank directly. If quality of boiler

water is getting worse, this bypass can also be used to increase continuous

blowdown water flow.

2) Boiler intermittent blowdown system

According to quality of boiler water, the water accumulated in bottom headers

of boiler with some deposits will be discharged intermittently. This water will

be discharged to intermittent blowdown flash tank directly. After steam water

separate in tank, steam is exhausted to atmosphere. The water in intermittent

blowdown flash tank then discharge to a concrete pit underground and mixed

with cooling water there, then discharged out.





145

3) Drainage and discharge system

Drainage and discharge pipes of each header would collect together to

drainage manifold in boiler house during startup and shutdown, and then

water is discharged to boiler intermittent blowdown flash tank.

4.2.11 Steam turbine lube oil and Lube oil handling system

Steam turbine lube oil system will supply lube oil to the bearing of steam

turbine and generator, with main oil tank, oil pumps, oil coolers etc.

4.2.12 Lubrication Oil System

The function of the lubrication system is to :

Provide oil to lubricate the turbine and generator journal bearings .

Provide oil to lubricate the thrust bearing

Provide oil to lubricate the turning gear .

Provide oil pressure for the generator hydrogen seal oil system .

Provide oil pressure for the governor system

The lubrication oil system is a closed system using oil stored in a reservoir

which is pumped to various points of use .the lubrication system uses both

shaft-driven and motor-driven pumps .A shaft-driven pump in the turbine

governor pedestal ,together with oil ejector in the reservoir ,pumps the oil

when the turbine is operating at or near rated speed .Motor-driven pumps are

used when the main oil pump and oil ejector cannot supply sufficient oil

pressure. The system uses two shell-and-tube oil coolers to regulate the

temperature of the lubricating oil system for the turbine generator unit consists





146

of the following major components:

Lubrication oil reservoir :

Turbine shaft driven main oil pump oil ejector

Auxiliary motor driven oil pumps

Vapor extractors

oil coolers

Oil piping

Protective devices

Bearing lift oil system

The lubrication oil reservoir is a steel tank in which the lubrication oil is stored.

Mounted on the reservoir are the auxiliary motor driven pumps, vapour

extraction system, level sensors, pressure transducers, and pressure

gages .the oil ejector uses high-pressure oil from the main oil pump discharge

to pick up oil from the reservoir when the unit is operating at or near rated

speed .Strainers on the oil ejector intake ,auxiliary oil pump suctions ,and oil

return drain help to prevent particle contaminants from circulating through the

system. The Reservoir is provided with man way access openings on the top

of the shell and a drain connection on the bottom.

The main oil pump is a volute-type centrifugal pump mounted horizontally on

the turbine extension shaft in the governor pedestal area. At or near rated

turbine speed, the main oil pump supplies all of the oil requirements of the





147

lubrication system. Provide oil pressure for the governor system and provides

two source of backup for the generator hydrogen seal oil system.

The oil ejector is mounted inside the oil reservoir. The inlet is supplied with

high-pressure oil from the discharge of the main oil pump when the turbine

generator is at or near rated speed. One outlet, the oil is directed through the

oil coolers to the turbine generator bearings. The other outlet supplies the inlet

side of the mail oil pump with oil.

The bearing oil pump (BOP) is an AC motor-driven centrifugal pump, vertically

mounted on the top of plate of the oil reservoir which is used at startup and

shutdown. During startup, the BOP is placed in service before the unit is put

on turning gear operation. It stays in service until the main oil pump can

satisfy the system oil requirements.

The emergency oil pump (EOP) is a DC motor-driven centrifugal pump which

is identical to the BOP except for the motor. The EOP serves as a backup to

the BOP in case of AC power failure.

The seal oil backup pump (SOB) is an AC motor-driven gear pump,

horizontally mounted on the top of the oil reservoir which is used during

startup and shutdown of the turbine generator when main oil pump discharge

pressure is too low to meet the oil pressure for the governor system and the

generator seal system high-pressure oil backup requirements.

Two vapor extractors are supplied for the reservoir, one vapor extractor is

normally operating and the other vapor extractor is on standby. The main

function is to remove oil vapors and maintain a slight vacuum at the turbine

pedestal, bearing housings, oil reservoir, and oil guard piping system.





148

The lubrication oil system includes two full-size oil coolers to maintain an

acceptable temperature range of oil to the bearings while the system is in

operation. The coolers are identical in construction. One cooler is used during

normal operation and the other cooler is kept on standby. A three-way transfer

valve between the two coolers director oil flow from reservoir to the selected

cooler.

Design basis of oil system

The Main oil tank capacity shall provide a minimum of 8 minutes retention

time. There shall be a minimum of 0.023 m2 of free oil surface for each lpm of

normal oil flow.

Turbine unit oil purification system shall be of centrifuge type. The hourly

conditioning capacity shall be equivalent to 20 percent of the combined

capacity of the main oil tank at operating level plus the oil in the lubricator

system that flows back into the main oil tank during a shutdown of the turbine

each hour. The equipment shall be designed to meet all lube oil purity

requirements established by the turbine generator manufacturer and ASME

Standard 118. The oil conditioning equipment shall be designed to provide for

removal of particulate matter greater than 10 microns absolute and all free

water in accordance with ASME.

In addition to unit oil purification ( centrifuge type) , a common turbine oil

purification system for both unit comprising of Dirty oil tank, Clean oil tank,

Purification system, 2x100% capacity pumpsets shall be provided.

Lube oil handling system will handle the unqualified lube oil before unit startup

or under normal operation. The lube oil volume of steam turbine is 32m3, so a

48m3 dirty oil tank and a 48m3 clean oil tank is set in this system, with oil





149

purifier and lube oil transfer pump.

A permanently mounted lubricating oil flushing pump shall be provided. This

pump shall be integral with to the lubricating oil reservoir. All accessories

including motor, piping, valves shall be included along with duplex filters

having online cleaning facility.

4.3 Major Auxiliary Equipment Selection 4.3.1 Feed-water pump

Each unit will be furnished with three 50% capacity motor-driven variable

speed feed-water pump with hydraulic coupling. Two pumps are working at

normal operation and one pump is standby. Three booster pumps are set for

each feed-water pump.

The capacity of the pumps is regulated by throttling pump discharge across a

feedwater regulator. The pumps are capable of operating satisfactorily at

deliveries ranging from minimum recirculation flow to the maximum specified.

The pumps furnished for each installation is operate satisfactorily both in two

pump parallel operation and single pump operation and when bringing in or

taking a pump out of service with one or two other pumps in service.

During startup and low load operation, when the variable speed drive cannot

provide the required feedwater flow control, a low load regulating valve is

used. The low load regulating valve is bypassed, and the full flow regulating

valve is used in conjunction with the variable speed drive to provide adequate

flow control.

Boiler feed pumps design is based on 105% of BMCR flow and the pressure

is corresponding to 103% of highest safety valve set pressure plus other





150

losses of the system. Pump is designed for complete frequency range of 47.5

to 51.5 Hz during normal operation. Pump and motor are provided with online

vibration monitoring system and bearing metal temperature measurement.

BFP SIZING DATA SHEET

No Name Symbol Unit Calculation & Remark BMCR TMCR

(3%MU)

Technical evaluation sheet

A BFP inlet suction flow

1 Maximun steam flow G1 t/h

HBD from Shanghai steam turbine works

1025 935.696

2 BFP galnd seal discharge and injection flow difference

G2 t/h 2 2

3 Interstage flow for RH spray G3 t/h

Data from Shanghai boiler works Co.ltd

42 42

4 Total suction flow of BFPs G4 t/h G4=G1*110%+

G2+G3 1171.5 1073.2656

5 Feedwater specific volume υ m3/kg

According to HBD 0.00110 0.00110

6 Feedwater density ρ kg/m3 ρ =1/υ 909.09 909.09 7 Capacity of each BFP G t/h G=G4/2 585.75 536.6328 Q m3/h Q=G*υ *1000 644.33 590.30 BFP suction flow m3/h 650.00 590.00

8 Interstage flow of BFP Q1 m3/h

Q1=G3*υ*1000/2 23.10 23.10

m3/h 30.00 30.00

9 BFP booster pump suction flow Q2 m3/h

650 590

*** According to technical evaluation sheet，BFP outlet flow shall be 105％BMCR flow.

BFP outlet flow G‘ t/h G=1.05x1025/2 538 Q’ m3/h Q=G'*υ *1000 592 BFP suction flow Q m3/h Q=Q'+Q1 615 m3/h 620

B BFP head 1 Pipe and equipments pressure drop





151


(3%MU)


a Pipe pressure drop from deaerator tank outlet to economizer inlet

△ PPIPE Mpa △ PLP＋△ PIP+△PHP

1.327 1.327

Mpa Considering 20％ margin 1.592 1.592

Coefficient for pressure drop calculation

Gate valve 8.4 8.4 Control valve 50 50 Suction strainer 2.5 2.5 Flow nozzle 9.33 9.33 b Equipment pressure drop

HP heaters △PEQUIP

Mpa 0.1*3 (3 HP heaters) 0.3 0.3

Total pressure drop from deaerator tank outlet to ecoonmizer inlet

△ P1 Mpa △ PPIPE+△PEQUIP

1.892 1.892

2

Water differential pressure between economizer inlet and deaerator tank normal water level

△ P2 Mpa (34.6-16.4)/100 0.182 0.182

3 Economizer inlet feedwater pressure at MCR condition

△ P3 Mpa According to data sheet from boiler works

19.27 18.83

4 Rated working pressure of deaerator(neagative) △ P4 Mpa

From HBD -0.8346 -0.7703

Total head of BFP △ P Mpa

△ P=△ P1+△P2+△ P3+△ P4 20.510 20.134

*** According to technical evaluation sheet，BFP discharge head shall be 103％ of highest safety valve set value plus other losses.





152


(3%MU)


Discharge pressure P MPa

1.03*20.4+1.892+0.182+0.392 23.48

Head △ P MPa 23.48-0.8346 22.64

C BFP sizing result Head H MPa 20.510 20.134 22.64 Suction flow Q m3/h 650.00 590.00 620.00 Note: all these data shall be submitted to manufacturer for the selection of BFP.

Below data is furnished by BFP vendor. 1 Pump

a Booster pump Style FA1D56A

Flow m3/h 650 590 620 Head m 102.15 104.58 103.41 Efficiency % 81.91 80.31 81.2 NPSHr m 3.79 3.55 3.66 Speed r/min 1490 Shaft power kW 197.32 187.89 192.2 b feed pump Style FK6D32M Inlet flow m3/h 650 590 620 Outlet flow m3/h 620 560 590 Head m 2239.3 2182.9 2481.66

Efficiency % 82.02 82.48 82.7

NPSHr m 34.81 30.03 33.1

Speed r/min 5357 5167 5491

Discharge pressure MPa(g) 21.51 21.06 23.64

Shaft power kW 4215.86 3718.92 4416.9

Interstage pressure MPa(g) 11.51 11.29 12.59

Interstage flow m3/h 30 30 30

2 Motor

Rated power Kw 5600

Rated voltage Kv 6.6

Speed r/min 1490





153


(3%MU)


Frequency Hz 50

The pump shall be designed to operate satisfactorily under the following

conditions:-

a) During rapid load pickup, when the feedwater at the motor driven boiler

feed pump inlet changes from the minimum to the maximum operating

feedwater temperature within 8 minutes.

b) During rapid load rejection, when the feedwater at the motor driven boiler

feed pump inlet changes from the maximum to the minimum operating

feedwater temperature within 15 seconds.

c) During hot restart after a unit trip.

d) During cold startup of the pump.

The suction specific speed of both the booster and main boiler feed pumps

shall be limited to the more restrictive of the following :

a) 12,000 based on NPSH required at 3 percent reduction in first stage head

while operating at the pump best efficiency point with maximum diameter

impeller and at the design speed.

b) 9,000 based on NPSH required at 0 percent reduction in first stage head

while operating at the pump best efficiency point with maximum diameter

impeller and at the design speed.





154

1x100% Forced Lube oil system is provided for Boiler feed pump.

Online vibration monitoring system and bearing metal temperature

measurement system.shall be provided for BFPs, booster pumps and their

motors

4.3.2 Heaters

The extraction system of each unit will be set with three HP heaters, four LP

heaters, one deaerator, and one gland steam condenser.

All of the heaters are horizontal type and are designed in accordance with HEI

standard. Shell wall thickness shall be determined in accordance with the

ASME code utilizing the allowable stress value for the shell material at the

design pressure and temperature. They are arranged indoors. Two LP heaters

are arranged at the neck of condenser.

The deaerator water tank has enough volume to ensure the boiler working at

the maximum operation condition for about 10 minutes. The deaerator storage

tank is also sized in conjunction with the deaerator outlet piping and height to

provide a storage volume which allow adequate transient NPSH for the boiler

feed due to a sudden full load rejection and prevent flashing at the pump

suction.

Deaerator shall remove dissolved oxygen from the condensate in excess of

0.005 cc per liter at any load from 5 percent to and including rated capacity.

HP heaters:

Closed feedwater heaters are used in a regenerative steam cycle to improve

the thermodynamic gain. This is accomplished by extracting system at various





155

points from the turbine and condensing kit using boiler feedwater. The

resultant heating of the feed water aids in avoiding thermal shock to the boiler

and reduces the fuel consumption required to convert the feedwater to steam.

Since the work lost by extracting the steam is derived from sensible heat, i.e.

no change of phase, the much greater latent heat recovered in the feedwater

heater by changing phase from steam to water result in a net energy gain.

Without a feedwater heater, the latent heat is wasted or thrown out in the

main condenser or cooling tower. Therefore, feedwater heaters also help to

reduce thermal pollution.

The high pressure heater is essentially an all-welded assembly. A special

stainless steel insert is assembled in the inlet end of every heater-transfer U

tube. Each high pressure heater has indicating, regulating and alarming

devices of level. When accident has taken place, automatic regulating of drain

level can fast bypass high pressure heater. Heater shell is provided with relief

valves to protect the shell in case of tube failure. On tube side, relief valve is

provided to prevent excessive pressure. Each high pressure heater contains

three zones, (i.e. desuperheating zone, condensing zone and subcooling

zone).

The welded seams are radiographed to insure the quality of the joint.

Stainless steel impingement plates have been installed in these heaters of

steam and other drains inlets to avoid direct impingement of steam and drains

upon the tubes to prevent tube erosion.

HP HEATER Nos. 8 DATA SHEET Parameter SL.

No DESCRIPTION

Tube side Shell side Unit

1 Sort Class 3rd pressure Class 2nd pressure





156

Parameter SL.

No DESCRIPTION


vessel vessel

2 Type JG-1370

3 Heating area 1370 m2

4 Design pressure 27.87 7.58 MPa(a)

5 Design temperature 295 420/295 oC

6 Max. operating

pressure

27.87 7.58 MPa(a)

7 Operating pressure 21.5 6.2145 MPa(a)

8 Operating

temperature

279.5 393.4/277.9 oC

9 Max. pressure drop 0.06 0.06 MPa

10 Flow 1056 85.89 T/h

11 Medium Water Steam & Water

12 Weld coefficient 1 1

13 Corrosion allowable 1

14 Estimated weight

Net weight 64956 Kg

Operating weight 70861 Kg

Flooded weight 82717 Kg

Manhole weight 120 Kg

15 Estimated Volume

Volume of water in sub-cooler zone at

normal water level

1.40 m3

Volume of water in shell at normal water

level outside sub-cooler zone

0.86 m3

Volume of steam in shell operating 12.1 m3

Volume of tube side 3.78 m3

HP HEATER Nos. 7 DATA SHEET





157

Parameter SL.

No DESCRIPTION


1 Sort Class 3rd pressure

vessel

Class 2nd pressure

vessel

2 Type JG-1575




6 Max. operating

pressure

27.87 4.81 MPa(a)


8 Operating

temperature

245 324/245 oC


10 Flow 1056 85.65 T/h




14 Estimated weight

Net weight 62121 Kg




15 Estimated Volume


normal water level

2.23 m3



1.27 m3







158

HP HEATER Nos. 6 DATA SHEET Parameter

SL.No DESCRIPTION Tube side Shell side

Unit

1 Sort Class 3rd pressure

vessel

Class 2nd pressure

vessel

2 Type JG-1230




6 Max. operating

pressure

27.87 2.07 MPa(a)


8 Operating

temperature

203.4 435.3/203.4 oC


10 Flow 1056 40.16 T/h




14 Estimated weight

Net weight 48739 Kg




15 Estimated Volume


normal water level

2.55 m3



1.32 m3







159

The high-pressure feedwater heaters shall be manufactured of following

materials or superior materials:-

a) Channel and channel: Carbon steel ASTM A515 Gr 70, cover carbon steel

ASTM A516 Gr 70, or forged steel ASTM A350 Gr LF2.

b) Shel: Carbon steel ASTM A515 Gr.70 or carbon steel ASTM A516 Gr70.

c) Shell skirt: Carbon steel ASTM A515 Gr 70, carbon steel ASTM A516 Gr 70,

or alloy steel ASTM A387 Gr 6, 11, or 12--Class 1.

d) Tubes: Stainless steel ASTM A688Type 304N

e) Tubesheet: Carbon steel ASTM A516 Gr. 70 or forged steel ASTM A350 Gr

LF2.

Feed pump hydraulic coupling shall be rated up to lower operating range of

20% of the maximum output speed.

LP Heaters:

The low pressure heater system adopts single string arrangement, which

consists of four low pressure feedwater heaters. The low-pressure feedwater

heaters shall increase the temperature of the condensate in stages by the use

of extraction steam. The low pressure heaters contain two zones(condensing

zone and subcooling zone). Heat transfer tubes are stainless steel U-tubes.

Heater shell is provided with relief valves to protect the shell in case of tube

failure. On tube side, relief valve is provided to prevent excessive pressure.

Each channel of low pressure heaters consists of a cylindrical shell and an





160

ellipsoidal head. LP heaters 1 & 2 are located in the neck of the condenser.

The maximum tube side flow shall be the condensate flow at turbine valves

wide open and a design margin of no less than 10 percent.

LP HEATERS Nos. 1 & 2 DATA SHEET Parameter

SL.

No DESCRIPTION Tube

side

Shell

side

Tube

side

Shell

side

Unit

1 Heater No. #1 #2

2 Type JD-840-5-2 JD-740-5-3

3 Heating area 840 740 m2

4 Design pressure 3.92 0.206 3.92 0.206 MPa(a)

5 Design temperature 130 130 130 130 oC

6 Max. operating

pressure

3.92 0.206 3.92 0.206 MPa(a)

7 Operating pressure 1.724 0.024 1.724 0.0752 MPa(a)

8 Operating

temperature

61.3 64.1 89.1 91.9 oC

9 Max. pressure drop across heater

0.04 <0.03 0.04 <0.02 MPa

10 Flow 791.56 18.22 791.56 35.94 T/h

11 Medium Water

Steam &

Water Water

Steam &

Water

12 Weld coefficient 1 0.85 1 0.85

13 Corrosion allowance 1

14 Estimated weight Heaters #1 & #2 combined

Net weight 36320 Kg



15 Estimated Volume





161

Parameter SL.

No DESCRIPTION Tube

side

Shell

side

Tube

side

Shell

side

Unit

Volume of water in sub-cooler zone

at normal water level

1.92 m3

Volume of water in shell at normal

water level outside sub-cooler zone

3.86 m3



LP HEATER No. 3 DATA SHEET Parameter SL.

No DESCRIPTION


1 Sort 2nd Class pressure

vessel

1st Class pressure

vessel

2 Type JD-530-3-2




6 Max. operating

pressure

3.92 0.48 MPa(a)


8 Operating

temperature

106.6 145.8/109.4 oC

9 Max. pressure drop across heater

0.06 0.015 MPa

10 Flow 791.56 23.63 T/h


12 Weld coefficient 1 0.85






162

Parameter SL.

No DESCRIPTION


14 Estimated weight

Net weight 11850 Kg




15 Estimated Volume


normal water level

0.37 m3



0.77 m3



LP HEATER No. 4 DATA SHEET Parameter SL.

No DESCRIPTION


1 Sort 2nd Class pressure

vessel

1st Class pressure

vessel

2 Type JD-580-8-4




6 Max. operating

pressure

3.92 0.686 MPa(a)


8 Operating

temperature

134.6 232/137.6 oC






163

Parameter SL.

No DESCRIPTION


across heater

10 Flow 791.56 38.52 T/h


12 Weld coefficient 1 0.85


14 Estimated weight

Net weight 12820 Kg




15 Estimated Volume


normal water level

0.65 m3



0.84 m3



10% Design margin shall be kept.

The low-pressure feedwater heaters shall be manufactured of following

materials or superior materials:-

a) Channel and: Carbon steel ASTM A515 Gr. 70, channel cover or forged

steel ASTM A350 Gr LF2.

b) Shell: Carbon steel ASTM A515 Gr. 70





164

c) Shell skirt: Carbon steel ASTM A515 Gr. 70 or alloy steel ASTM A387 Gr 6,

11, or 12 Class 1.

d) Tubes: Stainless steel ASTM A688 Type 304

e) Tubesheet: Carbon steel ASTM A516 Gr 70 or forged steel ASTM A350 Gr

LF2.

Deaerator:

The horizontal deaerator &storage tank is one of the main auxiliary equipment

in feedwater regenerative system for steam generating units. The primary use

of deaerator & storage tank is to remove noncondensable gases such as

oxygen, carbon dioxide, etc. The boiler water is to reduce oxygen content

below 0.005 cc/l. In addition, with extraction on the low pressure side of the

turbine and other resideual steam and drain, the deaerator shall heat the

boiler feedwater to saturated temperature under operating pressure of

deaerator so as to raise the thermal efficiency of the unit. The storage tank

can store a definite amount of saturated water at deaerator pressure and

conform to the standard of oxygen content to meet the needs of the boiler and

guarantee its safe operation.

Feature

1. Deaerator employs a two-stage system of heating and deaerating

feedwater.

1.1 Stage one

The prime element in our vent condenser zone is the self-adjusting spray

valve that allows incoming water, which is to be deaerated, to discharge as a





165

thin-walled, hollow cone spray. Because steam flows countercurrent, intimate

water to steam contact occurs with consequent latent heat transfer. As the

falling water reaches the spray stack, most of the dissolved oxygen and free

carbon dioxide have been removed at this point. Since nearly all of the steam

has been condensed, the non-condensable gases and the small amount of

“transport” steam exits through the vent piping.

1.2 Stage two

The partially deaerated water enters the tray stack at saturation temperature.

The heated water flow down over the trays, zigzagging through counterflow

steam. This arrangement provides additional retention time to allow oxygen

strip by the purest steam. The two-stage tray deaeration technique is the most

reliable method for meeting critical performance over a complete load range.

2. The deaerator is provided with constant speed spray valves and every

spray valve has great flow changes, which makes deaerator suitable to the

changing-load operation of turbine unit and insures the operation following the

sliding condition that vary with change of the turbine load to reduce the throttle

loss of the system and raise the thermal efficiency of the system.

3. The horizontal deaerator seats on the storage tank, thus the room

occupied by the equipment is minimal.

4. The amount of steam is large and the operation is convenient, thus

guaranteeing stable operation on the tank.

Modern internal vacuum ring construction is adopted, thus removing the

welding stress at vacuum ring.





166

Necessary free board shall be ensured.

DEAERATOR AND TANK DATA SHEET Parameter

SL.No DESCRIPTION Deaerator Deaerator tank

Unit

1 Sort Class 1st pressure

vessel

Class 1st pressure

vessel

2 Type GC-1056 GS-210

3 Design pressure 1.02/full vacuum 1.02/full vacuum MPa(a)

4 Design temperature 350 350 oC

5 Max. working

pressure

0.8346 0.8346 MPa(a)

6 Working

temperature

337 337 oC

7 Effective Volume 210 m3

8 Total volume 263 m3

9 Rated capacity 1056 t/h


11 Corrosion allowable 3.2 1.6 mm

12 Medium Steam & Water Steam & Water

13 Nozzle pressure

drop

0.014 MPa

14 Max. capacity 1109 t/h

15 Set pressure of

safety valve

0.88 0.88 MPa(a)

16 Others TOTAL DISCHARGE CAPACITY OF

SAFTY VALVES ON DEAERATOR AND

TANK IS 105821Kg/h

The deaerator shall be manufactured of following materials or superior

materials:-





167

i) Shell & Deaerating: Carbon steel ASTM A516 Gr 70.

section

ii) Storage section: Carbon steel ASTM A516 Gr 70.

iii) Shell supports: Carbon steel ASTM A36.

iv) Trays & Nozzles: Stainless steel ASTM A176 Type 430 or Stainless steel

ASTM A167 Type 304.

v) Tray supports: Stainless steel AS TM A176 Type 430 or Stainless steel

ASTM A167 Type 304.

vi) Baffles and liners: Stainless steel ASTM A167 Type 304.

vii) Vent & distribution: Stainless steel ASTM A312 Type 304.piping

viii) Spray valves : Stainless steel ASTM A276 Type 316.

4.3.3 Condensate extraction pump

Three 50% capacity constant speed motor driven Condensate extraction

pumps are set for each unit, two operate and one standby. The Condensate

extraction pump is “can” type with single suction impeller and with derivational

stage.

Each Condensate extraction pump shall be sized to supply 120 percent of the

flow requirements at VWO operation with 3% makeup for each unit.





168

The design of pump shafts shall be such that no critical speed shall occur at

less than 50 percent above the operating speed range.

The material for impeller and derivation stage is CA-6NM, which has good

ability to avoid cavitation during operation.

The Condensate extraction pump & motor shall be provided with online

vibration measurement system and bearing metal temperature measurement

system.

CEP SIZING DATA SHEET

No Name Symbol Unit Calculation & Remark VWO TMCR

(3%MU)


A Capacity of CEP

1 Condensate steam flow at VWO

G1 t/h

HBD from Shanghai steam turbine works 616.08 589.457

2 Normal drain to condenser G2 t/h " " 117.048 109.304

3 Normal makeup water to condenser G3 t/h " " 29.625 28.07

4 Other flow to condenser G4 t/h " " 2.828 2.683

5 Maximum condensate flow

G' t/h G'=G1+G2+G3+G4 765.581 729.514

6 Capacity of each CEP G t/h G=1.1*G'/2 421.07 401.23

7 Condensate water specific volume

υ m3/Kg According to HBD 0.00101 0.00101

8 CEP flow Q' m3/h Q=G*υ *1000 425.28 405.25 Q m3/h 450 410 505





169


(3%MU)


***

According to technical specification G t/h 1.2×VWO flow 459.35

Q m3/h 464

B CEP head

1

Pipe pressure drop from condenser hotwell outlet to deaerator inlet

△ P1 Mpa Calculation result 0.907 0.69

Mpa Considering 20％ margin 1.09 0.83

Coefficient for pressure drop calculation

Deaerator level control valve

66.600 66.600

Deaerator inlet flow nozzle

7.660 7.660

Suction strainer 2.500 2.500

2 Equipments pressure drop

Mpa Including CPU, GSC, 4 LP heaters & spring nozzle 0.789 0.789

LP heaters Mpa each 0.100 0.100 GSC Mpa 0.025 0.025 CPU Mpa 0.350 0.350

Spring nozzle of deaerator inlet

Mpa 0.014 0.014

3

Water differential pressure between deaerator inlet and condenser hotwell lowest water level

△ P2 Mpa 20.96-(-0.662) 0.2162 0.2162

4 Deaerator max. working pressure △ P3 Mpa 0.8346*1.15 0.960 0.960

5 Condenser highest vacuum △ P4 Mpa 735x133.3/1000-

10.05 0.088 0.088

6 CEP discharge head △ P Mpa

△ P=△ P1+△ P2+

△ P3+△ P4 3.14 2.88 2.80





170


(3%MU)


C CEP sizing result 1 Discharge pressure H Mpa 3.14 2.88 2.82 Flow Q m3/h 465.00 410 505

Note: above calculation result are based on China criteria and have been submitted to manufacturer for the selection of CEP.

Below data is furnished by CEP vendor

1 Pump

Condition Unit

Design condition

Max. continuou

s operation


Style NLT300-400X7

inlet emperature ℃ 46 46 46

inlet pressure kPa 10.05 10.05 10.05

flow m3/h 410 465 505

head M 335 322.5 312.8

effiency ％ 77 80 81

NPSHr of pump first stage impeller

M

3.1 3.3 3.4

speed r/min 1480

Pump minimum flow

m3/h

125

Discharge pressure MPa(g) 3.26 3.14 3.04

Shaft power kW 481 505.4 526

2 Motor Rated power Kw 630

Rated voltage Kv 6.6

Guaranteed effiency %

92

Synchronous speed r/min

1500

Frequency Hz 50

To counter the surging effect on hotwell 100 m3 size surge tank is provided.

4.3.4 Vacuum pump





171

2X100% capacity vacuum pumps will be furnished in the system. Two pumps

will be in operation for establish vacuum in condenser fast to shorten the start-

up time before the unit starting. During normal operation, one operates for

maintain the vacuum in condenser and another standby.

The vacuum pumps are of liquid ring type, and are sized in accordance with HEI

standards. Each vacuum pump designed capacity is of 25.0 SCFM (52Kg/h)

approximately of dry air plus associated water vapor to saturate at 1 inch (25.4

m/sec.) Hg atm. Besides, the pump capacity is also such that at starting, with

both pumps working in parallel, it is possible to create within 25 minutes sufficient

vacuum in the condenser suitable for raising the steam turbine to its full speed.

The design capacity of each pump shall be selected to meet the above

requirements with a margin of 10%.

The pumps shall not cavitate under all operating conditions including part

loads and design point, at max. CW temperature of 36 Deg.C.

The heat exchanger tubes shall be of SS-304 (welded). The shell of heat

exchangers and the tube plates shall be of mild steel corresponding to ASTM

A-285 Grade C. Material of construction of other components are as below or

superior:-

i) Casing: Nickel cast iron

ii) Shaft: Carbon steel EN-8

iii) Impeller :Nodular iron/stainless steel

iv) Shaft sleeves : Nodular iron/stainless steel





172

4.3.5 Condenser

4.3.5.1 Structural Characteristic

The condenser is designed in the form single shell, divided water boxes Two

pass and installed in transversal arrangement. The condenser mainly consists

of neck, shell, waterbox, exhaust expansion joint and so on.

Four fixed base supports are arranged at the four angles at bottom of the

condenser. Each fixed base support with three slot holes is connected to the

foundation with M36 anchor bolt in order to satisfy the requirements of

condenser expansion. Four sliding base supports are arranged at middle at

the bottom of the condenser, so that the complete condenser can steadily

upon the eight base supports. The condenser is connected to turbine exhaust

hood with expansion joint.

4.3.5.2 Neck

Condenser neck is made of welded carbon steel plates and steel plate is

applied for inside supporting and ribbed plates for reinforcement. T-type beam

steel are applied inside each sideplate of neck to increase transversal rigidity

of sideplates so that the complete neck could be rigid enough. Extraction lines

go through neck. Stainless steel lagging is adopted to cover the outside of

extraction lines in order to avoid erosion. All extraction lines are equipped with

stainless steel waveform expansion joints to absorb thermal expansion in the

lines.

In order to protect abnormal higher temperature caused by turbine bypass

inlet steam. Water screen spray protection device is equipped inside neck.





173

4.3.5.3 Shell

Shell made of full welded structure is the main part of condenser and

possesses reliable tightness.

Two tube bundles are set up in shell. Triangular conventional layout is

adopted for the arrangement of tube bundle. All tubes are seam welded. Air

extracting line in cooling area are evenly distributed at cooling water entrance.

Support plates are distributed between front and back tube sheets to support

cooling tubes. So that tubes could contact support plates closely to improve

the vibration property of tubes and avoid resonance. Tube sheets are welded

to two ends of shell and thinner steel plate is applied for flexible transition to

compensate thermal expansion difference between cooling the and shell.

Proper access manhole and other connections are provided on the shell.

An access manhole is provided on the tube bundle. Access openings or

manhole is provided on the interior of the condenser to provided access to the

tube support plates.

In some place where steam of water enters the condenser shell provided

suitable approved baffle to prevent impingement on the tube and shell, and

proper distribution of condensate and steam.

Hot well is designed below tube bundles with enough space so that

subcooling could be minimized in the process for reheating transfer and raise

deaerating effect as well. The hotwell has enough space for the requirements

of condensate level change.

A flash box is for absorbing drain. In this way, draining water can be





174

temperature-reduced and pressure breakdown and then drained into

condenser so that tube bundle could be protected from erosion of steam and

water higher temperature and pressure.

4.3.5.4 Waterboxes

Waterboxes are designed in the form of semicircle and cone-type. Thus

resulting in good rigidity of the hole waterbox body, lightweight and favorable

flowing property of cooling water. The water box is provided cathodic

protection equipment. Inside of this condenser safety ladder is assembled to

the inside wall of waterbox and both vacuum extracted outlet and air vent

displaced at the top of waterbox. Manhole is equipped outlet the lower part of

waterbox for maintenance personnel easy access.

Sufficient tube extract space shall be kept in the front of tubesheets for taking

out of tubes if tubes are required to be taken out.

4.3.5.5 Exhaust expansion joint

Stainless steel waveform expansion joint is arranged at the exhaust expansion

joint to absorb thermal expansion from turbine low pressure exhaust cylinder

and condenser at vertical centerline direction of flow pressure exhaust cylinder.

The surface condenser is a double pass design with divided water boxes

which will facilitate operation of one half of the condenser while the other half

is under maintenance. The bottom of the condenser serves as a hot well for

condensate storage.

Design Basis:





175

The thermal design of surface condenser is based on HEI standard

considering 33°C cooling water temperature for a temp rise of 10°C

corresponding to heat load for VWO, 3% makeup and 10.05MPa(a)back

pressure. The condenser has the capability in thermal design to operate at

36°C maximum cooling water temperature.

The condenser hot well minimum storage capacity at the normal water level

shall be 5 minutes of condensate storage when operating at the turbine valves

wide open. The oxygen content of the condensate leaving the hot well shall

not exceed 0.015 cc per liter at all conditions

CONDENSER DATA SHEET

Sl.No Description Parameter Unit

1 Type N-18300

2 Model Single pressure divided two passes surface

3 Condenser effective surface area 18300m2

4 Condenser back pressure 10.05 KPa(a)

5 Condenser design pressure

Shell side 0.1/Full vacuum MPa(g)

Waterbox side 0.4 MPa(g)

Waterbox side test pressure 0.6 MPa(g)

6 Condenser design temperature





176

Sl.No Description Parameter Unit

Shell side Less than 121 oC

Waterbox side Less than 60 oC

7 Inlet temperature of cooling water 33 °C

8 Max. inlet temperature of cooling water

36 °C

9 Design flow of cooling water 34020 m3/h

10 Cleanliness factor 0.85

11 Water velocity in condenser tubes 2.087 m/s

12 Tube thickness 0.7 mm SS 304 seam welded in both condensing and air

cooling sections

13 Tube plugging margin 5%

14 Tube sheet material TP304+SA516Gr70

4.4 Table of economic index

Heat consumption rate of turbine 8024.5 KJ/kW.h

(1916.6 Kcal/kw.h)

Guarantee efficiency of boiler (high heating value) 87.1%

Note ： The above results are based on TMCR (Heat Rate Guarantee)

condition. Turbine cycle heat rate is 1916.6 Kcal/kW.h based on with 0%

makeup, 33 Deg CCW inlet temp & 10.05 kPa(a) back pressure of condenser.

5 INSULATING MATERIAL





177

According to different temperature and pressure, different layout of

equipments and pipes in the BTG, the insulation material is considering as

follows (Code for designing insulation and painting of fossil and fuel power

plant DL/T 5072-1997) taking care of the following design data:

a) Design ambient temperature: 40℃

b) Maximum cladding temperature: 60 ℃

c) Wind speed: 0.5m/s for inside and 0.25m/s for outside the plant

buildings0.5 m/sec for inside and 0.25 m/sec for outside the plant area

1) Temperature over 350 degree’s equipments and pipes will adopt silicate or

aluminium silicate material.

Silicate: conductivity factor λ＝0.031+0.00015tm W/m·℃

Density 80Kg/m3

aluminium silicate: conductivity factor λ=0.035+0.00018tm W/m·℃

Density 150kg/m3

2) Temperature under 350 degree’s equipments and pipes will adopt rock

wool or glass wool material.

rock wool: conductivity factor λ＝0.032+0.00018 tm W/m·℃

Density 150kg/m3





178

glass wool: conductivity factor λ＝0.029+0.00011tm+7.65x10-10tm3 W/m·℃

Density 48kg/m3

3) Valves will adopt insulating sleeve and abnormities will adopt slurry of

silicate.

4) Aluminum material will adopt for protecting layer.

Date post:	11-Nov-2014
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