O & M Manual for Boiler

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OPERATION & MAINTENANCE

MANUAL

FOR 1 X 41TPH

100% INDIAN COAL FIRED

ATMOSPHERIC FLUIDISED BED COMBUSTION BOILER

SUPPLIED TO

HARE KRISHNA METALLICS LIMITED

KOPAL, KARNAKATA

THERMAX PROJECT NO : PD 0161


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Operation & Maintenance Manual

4 Main Steam Piping.................................................................................................... 21

5 Boiler Blow Down System.......................................................................................... 215.1 Drain Lines...................................................................................................... 225.2 CBD Drain.......................................................................................................225.3 IBD Drain ........................................................................................................225.4 Other Drains....................................................................................................235.5 Blow down Tank ..............................................................................................23

6 Air and Gas System .................................................................................................. 246.1 System Description:......................................................................................... 246.2 FD Fan ...........................................................................................................246.3 Air Pre Heater ................................................................................................. 246.4 PA Fan............................................................................................................256.5 Air Ducts .........................................................................................................25

7 Flue Gas System ......................................................................................................277.1 System Description.......................................................................................... 277.2 Electrostatic Precipitator (ESP)......................................................................... 277.3 ID Fan.............................................................................................................27

8 Fuel Feeding & Firing System ....................................................................................28

8.1 Fuel Bunker.....................................................................................................288.2 Rotary Feeders................................................................................................288.3 Fuel Mix Nozzles .............................................................................................298.4 Combustor ..................................................................................................... 298.5 Bed Drain System............................................................................................ 308.6 Ash Drain........................................................................................................30

9 Chemical Dosing & Sampling System.........................................................................309.1 HP Dosing System...........................................................................................309.2 Description of Dosing System Skid HP).............................................................30

9 3 Sampling System 31


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11.1 Emergency Procedures ..................................................................................53

12 Operational Precautions for Safety ........................................................................... 55Section-D .............................................................................................................................59

1 Section Overview ...................................................................................................... 592 Recommended Maintenance Practice ........................................................................59

2.1 Preventive Maintenance...................................................................................593 Conditioned Based Maintenance................................................................................60

3.1 Daily Checks ................................................................................................... 603.2 Daily Maintenance ...........................................................................................623.3 Weekly Checks................................................................................................633.4 Monthly Checks...............................................................................................633.5 Checks Every Six Months.................................................................................643.6 Checks Every Year ..........................................................................................643.7 Annual Maintenance Check Sheet ....................................................................65

4 Boiler Annual Maintenance and Overhaul ...................................................................724.1 Planning Before Overhaul ................................................................................724.2 Shutdown and Cooling the Boiler ......................................................................724.3 Inspection after Cooling....................................................................................72

4.4 Drum Inspection ..............................................................................................724.5 Inspection of Screen, Primary & Secondary Superheater, Evaporator I/ II &Economiser................................................................................................ 73

4.6 Expansion Joints .............................................................................................734.7 Insulation and Cladding.................................................................................... 734.8 Other Equipment .............................................................................................734.9 Feed & Boiler Water Conditioning .....................................................................734.10 Fans .............................................................................................................754.11 Safety Valves, Start Up Vent Valves And Other Isolating Valves ........ ........ ........ 76

5 Boiler Preservation Procedure 77


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8.3 Weld Repair of Small Cracks in Tube ................................................................98

8.4 Plugging Tubes in Drums & Headers.................................................................988.5 Replacement of Tube Section......................................................................... 1008.6 Removing Tubes from Drums, Headers & Tube Plates ..................................... 1008.7 Attachedfigures 13 to 21 ............................................................................... 101

Section E............................................................................................................................ 110

Volume 2 Drawings.............................................................................................................. 111

List of Drawings .................................................................................................................. 112

Volume 3 E & I Specifications.............................................................................................. 113

Section 01 .......................................................................................................................... 114Section 02 .......................................................................................................................... 114Section 03 .......................................................................................................................... 114Section 04 .......................................................................................................................... 114Section 05 .......................................................................................................................... 114Section 06 .......................................................................................................................... 114Section 07 .......................................................................................................................... 114Section 08 .......................................................................................................................... 114Section 09 .......................................................................................................................... 114Section 10 .......................................................................................................................... 115

Volume 4 Vendor Manuals ................................................................................................... 116

Section 01 .......................................................................................................................... 117Fan TLT Engineering................................................................................................ 117

Section 02 .......................................................................................................................... 117H.P / LP. Dosing System - NM Enterprises..................................................................... 117

Section 03 .......................................................................................................................... 117Level Gauge Hi Tech Systems (Tyco) ........ ........ ........ ........ ........ ........ ....... ........ ........ . 117

Section 04 117


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Section 07 .......................................................................................................................... 120

Local Indicator Nishko...............................................................................................120Section 08 .......................................................................................................................... 121

Control Valves MIL.................................................................................................... 121Section 09 .......................................................................................................................... 121

Power Cylinder Keltron.............................................................................................. 121Section 10 .......................................................................................................................... 121

ACVFD Drives ABB.... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .. 121Index.................................................................................................................................. 123


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Volume 1 Boiler Description

Chapters Covered in this Part

Section ASection BSection CSection-DSection E


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Section A

Topics Covered in this Chapter

Design Specifications of Steam GeneratorDesign CodeMaterial Specifications Pressure PartsHeating Surface AreaFuel

Fuel Analysis (% By Wt.)Bed MaterialContinuous Blowdown Intermittent BlowdownFeed Water Recommended QualityBoiler Water Recommended QualityUtilitiesChemicals for DosingSite Condition

FansHP Dozing SystemRotary FeedersGauge GlassSafety ValvesTemperature ProfileFlue Gas Pressure ProfileProcess Flow Diagram


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Number and Type of Boiler

1 no. AFBC, Bi Drum, outdoor, water tube, natural circulation, balance draft, Under-bed firingsystem, Bottom Supported with RCC construction..

1 Design Specifications of Steam Generator

Parameters Unit Value

Boiler Rating [MCR] TPH 41

Steam Pressure at MainSteam Stop Valve Outletfrom minimum Load uptoMCR

Kg/cm2(g) 66

Steam Temperature at the

Main Steam Stop valve atMCR

Deg C 490+/- 5

Main Steam TemperatureControl range at the MainSteam Stop Valve Outlet.

% MCR 60 100

Feed Water Temperatureat Economiser Inlet / Spraywater temp

Deg C 130

Flue Gas Temperature at Deg C 160


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Description Details Size In Mm Material

Top Header 200 NB X SCH 160 SA 106 Gr BBottom Header 200 NB X SCH 160 SA 106 Gr B

Panel Tubes 63.5 O.D x 4.06 Thk SA 210 Gr A1RH Panel

Bend Tube 63.5 O.D x 4.06 Thk SA 210 Gr A1

Top Header 200 NB X SCH 160 SA 106 Gr B

Bottom Header 200 NB X SCH 160 SA 106 Gr B

Panel Tubes 63.5 O.D x 4.06 Thk SA 210 Gr A1

Front Panel

Opening Tubes 63.5 O.D x 4.06 Thk SA 210 Gr A1

Top Header 200 NB X SCH 160 SA 106 Gr B

Bottom Header 200 NB X SCH 160 SA 106 Gr B

Panel Tubes 63.5 O.D x 4.06 Thk SA 210 Gr A1LH Panel


Top Header 200 NB X SCH 160 SA 106 Gr BBottom Header 200 NB X SCH 160 SA 106 Gr B

Panel Tubes 63.5 O.D x 4.06 Thk SA 210 Gr A1Rear Panel


DC1-DC11 100 x Sch 80 SA 106 Gr B

Reducer 200 x 100Nb x Sch 80 SA 234 WPB

Pipe 168 3 O D x 10 97 Thk SA 106 Gr BDown comers


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4 Heating Surface Area

Zone Unit Value

Boiler Bank Zone Sq.Mtr 354.0

Water wall Zone Sq.Mtr 242.1

Super Heater Zone Sq.Mtr 688.0

Inbed coils Sq.Mtr 81.6

Economiser Sq.Mtr 566.0

Total Heating Surface Sq.Mtr 1931.7

5 Fuel

Fuel Type Fuel Name

Main Fuels Indian Coal

Start up Fuel Charcoal sprayed with Diesel fuel.

6 Fuel Analysis (% By Wt.)

6.1 Ultimate Analysis

Composition Unit Indian Coal Char

Hydrogen % Wt 2.30 0.42

Carbon % Wt 37.1 40.30


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7 Bed Material

Required Per start Up : 60 Metric Tonnes (Approx.)Lump Size : 0.8 mm to 2.36 mm (100 %)

Bluk Density : 10001100

Chemical Composition : AL2O3 % 35 to 45

SiO2 % 55 to 65

7.1 Bed Material Specifi

cations - Crushed RefractoryMaterial : Sieved natural sand/Crushed

refractory Bulk Density : 1200 1400 Kg/m3

Temperature : >1300 deg C

SIZE : 0.7 to 2 (for sand) Fusion

Shape : Sub Angular / Spherical.

Chemical Composition Percentage limits

SIO2 : 5060

AL2O3 : 37-40 , Min 30% required

FEO :


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Total Fe ppm


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Supply Temperature Deg C AmbientQuality SOFT & Chlorine free

Duty Sample Cooling.

12.3 Instrument Air


Pressure Kg/cm2

(g) 67Dew point Deg C -40

Temperature Deg C Ambient

12.4 Service Air


Pressure Kg/cm2(g) 7

Temperature Deg C Ambient

Quality Dry & Oil Free

Duty General purpose

13 Chemicals for Dosing

HP Dosing Tri sodium phosphate


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FD fan ID Fan PA Fan

Duty conditions Unit Test BlockConditions

Test BlockConditions

Test BlockConditions

Quantity Nos. 1 1 2

Nature of medium Clean Air Flue Gas Clean Air

Air /Gas density Kg/N M3 1.29 1.31 1.29

Volume Kg/hr 77486 86970 15300

Gas Temperature

at Fan Inlet Deg C 45 150 45

Absorbed Power /Rated Fan Power

KW 250 90 50

Differential statichead

mmWc 860 200 760

Fan Speed Rpm 1480 980 2920

Static Pressure mmWC 8437 1962 2920

Free/FixedBearing Housing

22220 EK/C3

SNH-520

22220 EK/C3

SNH-520

222216 EK/C3

SNH-516

222211 EK/C3

SNH-511

222176 EK/C3

LOE-217

222174 EK/C3

LOE-214

BearingLubrication Servogem; EP 2 Servogem; EP 2 Servogem; EP 2


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Char Unit Design 100% MCR 50% MCR Min

Speed RPM 3.14 2.62 1.31 0.65Through Loading % 95

Capicity Per Unit time perRevelation

Kg/hr/reve0.00234

18 Gauge Glass

18.1 Drum Level Gauge

Description Details

Make HI- TECH SYSTEMS AND SERVICES LTD.

Tag No. LG-600A & LG-600B

Type Bicolor Port type

Location Steam drum

Operating Pressure 72.7 kg/cm2 (g)

Design Pressure 78.8 kg/cm2 (g)

Hydrotest Pressure 315 BAR

C/C Distance 800 mm

Visibility Range 403 mm

Operating Temp. 289 Deg C (Saturated) Normal Operating


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Description

Application

Unit Drum LHS Drum RHS SH

Tag No B7 B8 S4

Model HC56

W-IBR-SPLHC56

W-IBR-SPLHCA58

W-IBR-SPL

Rated Capacity Kg/Hr 19027 19313 13892

Quantity 1 / BLR 1 / BLR 1 / BLR


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20 Temperature Profile

20.1 Gas Temperature

At the outlet of furnace : 875 Deg C.

At the outlet of bank tubes : 445 Deg C.

At the outlet of economiser : 250Deg C.

At the outlet of air-preheater : 160Deg C.At the outlet of ESP : 160Deg C.

20.2 Water Temperature

Condensate from process : 47 Deg C.

Process return : 100 Deg C.Make up water : 32 Deg C.

inlet of FW Pumps : 130 Deg C.

the inlet of economiser : 130 Deg C.

At the outlet of economiser : 216Deg C.


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1 Section Overview

This section gives a brief overview of the boilerand its associated systems. The description ofthe various systems that form part of the boilerpackage is also included. The aim of this sectionis to make the reader familiar with the boilerpackage components before introducing theoperation and maintenance sections..

Brief Overview

The boiler package supplied by Thermax Ltd,Pune, India and has been designed for 41 TPHsteam generation, 66 kg/cm2 (g) pressure, 490+/- 5 deg C Super Heated Steam output designedfor firing with 100% Indian Coal and secondaryfuel 70% Indian Coal + 30% Char. This boileris AFBC, Bi-Drum, outdoor, natural circulation,

Water tube, fl

uidised bed combustion, UnderbedFuel Feeding System, balance draft, BottomSupported with Steel construction & HopperBottom design.

Fuel Combustion will be in an Atmospheric BedCombustor (AFBC) fixed at the Boiler bottom.Fuel is stored in Bunker. Rotary feeders areconnected at the bottom of hoppers (below thebunker). The fuel is fed by these feeders to

GENERAL DESCRIPTION

The main parameters of the boiler are

Maximum Continuous

Rating

41TPH

Steam Pressure 66 kg/cm2

Steam Temperature 490+/- 5 Deg C

Fuel Fired Indian Coal and

Char

The boiler has been designed to confirm toIndianBoiler Regulations (IBR)

The boiler is divided into a combustion zonei.e. furnace and non-combustion zone i.e.economiser, air heater etc. The furnace sides,front and rear are of membrane panel constructionproviding a gas tight sealing. For all the fourwater wall bottom headers, water is fed throughsupply pipes from water drum. The sidewall, frontwall and rear wall panel tubes top headers areconnected to the steam drum through risers. Thefront wall panel tubes form the roof of the furnace.

Feed water is pumped by feed water pumpsfrom deaerator to economiser through feed watercontrol station. The feed water from economiseroutlet is then led to the steam drum. Steam is

t d i th f b ll t b


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Maintains the super heater temperature bycontrolled combustion.

Balanced draft conditions inside the furnacesuitable for combustion is being maintained byI.D fan.

Air pre-heater, ESP andfinally into the stack by IDfan.

The starting, stopping and safe shut down of boilerare done by manual intervention systematically

and sequentially through DCS control system fromcontrol room.

Details of equipments, their brief operationaland maintenance features are elaborated in thesubsequent sub-sections and chapters of thismanual.

2 Feed Water System

(Ref. P & I Diagram D12-1PD-6499P, R-2)

Feed water system consists of the following:

1. Feed water control station.

2.1 Feed Water Control Station

When the boiler is in service, feed water must

b ti l li d t i t i l

kept closed. This drain is to be opened only todrain the line when control valve has to be opened

for inspection/maintenance.Following instruments are provided at the inlet offeed water control station:

Flow nozzle FE-500 with flow transmitterFT-500 is provided for total feed waterflowmeasurement. Flow transmitter transmits thewaterflow signal to flow indicating controllerat control panel.

A 25 NB pipe tapping with W33 valve for theSH desuperheater.

Control valve is operated through the Flowindicating controller (FIC-600). Input signals aregiven to FIC-600 by Level indicating controller(LIC-600), steam flow transmitter (FT-604) andfeed water flow transmitter (FT-500). Ref. threeelement control for detail operation of drum levelcontroller.

From the control station feed water flows toeconomiser inlet header (bottom) through an100 NBnon return valve (W-24). ThermocoupleTG-501is located before the Eco. inlet header tomeasure the feed water temperature prior to Eco.Pressure gaugePG-501is provided with isolationvalves (W15& W16)to measure the FW pressure

t E i l t


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and a suitable control signal is generated which isused to drive the 100% control valve. The major

advantage of the loop is its ability to maintaindrum level during load swings, variations & throwconditions that are certain to occur during theoperating regime of any steam generator. Thoughthis loop is advantageous from an operation pointof view, it is recommended to use this loop atloads > 30%, as the single element control loop isoptimised for low load conditions with its controlvalve sizing & parameter tuning

2.2 Attemperation Control Station

A tapping25 NBfrom Feed Water line is provided,to supply spray water for Attemperator. This lineis provided with a manual isolation valve W-33&NRVW37. A temperature control valve TCV-604with isolation valves W-34is provided. A by-pass

manual valve W-35 is provided. This line connectsto Attemperator through a NRV W-36.

3 Boiler Pressure Part Description

This boiler is AFBC design, BI-Drum, outdoor,natural circulation, Water tube, fluidised bedcombustion, Underbed Fuel Feeding System,

f S S

Provision of this additional heating surface,increases the efficiency of the steam-generating

unit and saving in fuel consumption is achieved.Economiser is located in between boiler bankoutlet and Air Pre-heater.

A continuous loop tube Economiser assembly isconstructed with rows of 38.1 O.D x 3.66 thicktubes, and two headers. Both the ends of the coilwere terminated to the top and bottom headers bywelding.

Feed water flows from the bottom header to thetop headers through these coils. Heated waterflows out from the top header to steam drumthrough the connecting pipe. The economiser isfully drainable by the drain valves W-26 locatedon the inlet header.

Economiser top header is provided with the

following attachments:

25 NB air vent with two valves (Tag No. W28which will be kept open during initial fillingto remove the air trapped between the coil.Closed after free flow of water from the vent.

Pressure indicatorPG-502with twin isolationvalve W 27.

Thermocouple (TE-502) is provided for panel


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drum. DWLGS are provided at both ends ofthe drum.

Two nos. Level transmitters are providedLT600A B Cwhich transmit the actual water levelto the remote indicators i.e. at control roomand provide drum level signal to the drum levelcontroller

Drum safety valvesB 7& B 8which protectsthe boiler and the personnel against theconsequences of abnormal pressure increase

because of sudden load decrease, mal-functioning offiring system, steam stop valveetc.

Level indicatorLI 600: this gauge is mountedat the firing floor, so as the firing floor attendantcan view the drum level.

H.P dosing connection: To dose phosphate in

to the steam drum to maintain the boiler waterquality.

Continuous blow down (CBD): To drain theboiler water during operation to maintain thewater concentration. Also the water sampleis taken from this blow down. It is connectedto the common IBD tank directly as well asthrough CBD tank.

B 6

ensure the uniform distribution of feed water in theentire length of the steam drum.

Pipe is made in two pieces for installation easeand provided with flanged joint.

Continuous blow down pipe (CBD) 1 no 25NBperforated pipe with 6-7 holes is installed in thedrum with holes at 6 O clock position. CBD pipeis provided to drain the boiler water to maintain theboiler water concentration at the specified limit.Pipe is made in two pieces for installation easeand provided with a drain hole to drain the waterduring shut down.

HP dosing pipe 1 no 25NB perforated pipe with6-4 holes is installed in the drum with holes at 12Oclock position. As the pipe is of perforated type

the chemical is uniformly distributed across thelength of the drum. Chemical dosing at steamdrum is, to maintain boiler water concentration asper the specified limit. Pipe is made in two piecesfor installation ease and provided with a drain holeto drain the water during shut down.

3 3 W t D


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sealed enclosure suitable for balanced draftoperation. Adequate number of access doors

(which normally remain tightly closed) have beenprovided in the furnace and in the second pass forinspection of observation of the bed/Flame andfor addition bed material during regular operation.

3.6 Inbed Evaporator

(Drg No. PD1-1PD-45751, R-1)

Figure 1 Inbed Evaporator

In-bed coils (50.8 OD x 6.35 THK Tubes) areprovided inside the furnace. Water mixture entersthe in bed evaporator bottom header throughdown comers from steam drum (D1 to D4) andthe steam water mixture exits through in bedevaporator top header and then through waterwall panel tubes to water wall top headers. BothR.H & L.H Inbed Evaporator bottom headersreceive water from the steam drum through supplypipes.

Inbed evaporator outer and Inner coils bottomloops are provided with round studs at an angle of120 deg to reduce direct impingement of particleson the bare tubes and to avoid erosion. Phoscast

90 XR Refractory has been applied over the

Superheated steam also eliminates the formationof condensate in steam piping which is harmful to

the turbine blades and pipelines.There are two stages of superheater in thisboiler. They are SH-1 & 2. From the steam drumdry saturated steam enters the SH-1 i.e. 1ststage inlet header (O.D 219.1 x 18.26) throughsaturated steam supply tubes. From the 1ststage inlet header, steam flows to 1st stage outletheader through 44.45 O.D x 4.06 Thk coils. SH-1

is installed vertically above the goose neck zonewith adequate supports. The SH headers aresupported through saddle supports.

1st stage outlet header is connected to SH-2i.e.2nd stage inlet header with Attemperator.From the 2nd stage inlet header, steam flows to2nd outlet header through 44.5 OD x 4.06 thickcoils.

150 NB Steam outlet line is taken from the 2ndstage outlet header of Superheater SH-2.

Following connection is attached to primary

S.H. Inlet header:

15NB sampling line with isolation valve S-17,which is used to take saturated steam sample.

A 25 NB air vent with twin isolation valves S-1


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System Description

P&IDiagram(D12-1PD-6499P, R 21)(SteamandWater system) show the various drains from theboiler, main steam lines, etc. A common drainsystem has been provided for both he boilers.

Large quantities of steam of high pressure /temperature water are not drained through opencanals for the following reasons:

a) Such draining will cause splashing of highvolumes of steam, which can be a nuisance bythe noise it creates, and also it affects the visibilityaround the draining area.

b) High temperatures of these drains can causescalding injuries to workmen who may come incontact with it.

c) The force and temperature of these drains willerode the linings of the drain canals.

d) Low-pressure steam, which can be recovered,if required, is wasted.

5.1 Drain Lines

A 50 NB Common drain line is provided which is

LH In-bed evaporator bottom header

RH In-bed evaporator bottom header

Economiser header drains

Eco I/L header

Drain header has following

A50 NB-thk drain line for draining FurnaceDrain Header to nearest trench.

An50 NBthk initial filling line withW -26andisolation valve W-26. The water is suppliedfrom DM water transfer pump.

Drain line is connected to IBD tank with anisolation valve W - 40

5.1.2 SH Drain Line

Following drains (All 25 NB) are connected to theSHdrain header ).

Main steam line drain before and after mainsteam stop valve.

Main steam line drain before main steam stopvalve has 25 NB drain line with isolation valve(S-8) this line is connected to the BD tank.


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SOURCE VALVE TAG NOS. TEMP. OF

DRAIN C

FREQUENCY OF

USAGE

S.H. & Main steamdrain

FOR M.S. LINE isolation valvesS-8

Varying from70 to 520

Draining of condensateduring start-up and after ashut down.

Furnace & Economiserdrains

For ECO drains isolation valvesare W-26, and for furnace W.Wisolation valves are W-39.

~70 - 150 During boiler start-up and

shutdown.

Drains indicated in the above Table are connected

to the common intermittent blow down (IBD) tankexcept CBD drain and various samples. CBD tankis connected to IBD tank while samples to thenearest drain trench.

5.4 Other Drains

Other drains of the boiler are open drains and areconnected to the nearest trench within the boiler

area. The drains are -

All level control station drain

All pressure control station drain

Steam drum level indicator.

Steam drum safety valve drains

Sample cooler sample let off drain

l d k

of the tank, such that the drain fluid is directed

circumferentially around the inner wall of the tank.Tangential flow of the drain fluid into the tankseparates steam from the water. Steam rises tothe top of the tank and water collects at its lowerportion. A vent is provided at the top of the tank.

Following connections are connected to thecommon BD tank.

A Level gauge glassLG-550with isolationvalvesD6 & D6 has been fitted on the tank toverify water level in the tank.

Tank is provided with a50 NBdrain pipe with avalve (Tag no. D-7) forflushing purpose.

Connections from CBD line, from IBD line, fromDrain line, and from MS Drain line.

An air vent to atmosphere.


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6 Air and Gas System

( P & I DIAGRAM D12-1PD-6500P, R- 2)

Air System

This chapter describes supply of primary andsecondary air to the boiler. The components thatform part of air system are

FD Fan

Air Pre-Heater (APH)

Air ducts

Combustion air to Windbox

Secondary Air OR Overfire air.

Secondary Air For Air Spray Nozzle

6.1 System Description:

6.2 FD Fan

Figure 2 FD Bearing

Each Boiler is provided with 1x 100 %. F.Dfans driven by electric motor to supply maincombustion air to the furnace and various otherequipment. FD fan is of centrifugal type, withradial, backward curved blades.

the required fan output pressure and flow. TheVFD receives input signal from furnace pressure

indicating controller (HZ 200).Fan Discharge Duct

1. To minimise the force due to possiblemovement of the discharge duct on the fan, aswell as to isolate fan vibrations being passed onto the duct, the fan is connected to the dischargeduct through bellows type expansion joint (1no)

Test pockets temp. gauge and pressure gauge isprovided on outlet duct. A Draft Gauge (DG 200)is provided with an isolation valve (A1)attheoutletduct.

Fan outlet is connected to air pre-heater (APH)through a ducting.

Aerofoil

An Airfoil to measure the airflow is provided (AFM200). The airflow is measured by the principleof pressure drop across the element beingproportional to the airflow passing across it. Flowtransmitter (FT-200) gives input to a controller(FIC-200), which also get inputs from combustioncontrol and ultimately it controls suction air bypower cylinder.

Please refer Vendor Manual for safe Operation


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APH-II. APH is provided with common hopper forAPH-II & APH-I. Due to change in direction and

sudden pressure drop in APH hopper, fly ash getscollected in the hopper. Hot air duct from Bed AshCooler is connected to APH hopper.

Ambient air from FD passes through APH toabsorbs sensible heat from flue gases. Amanually Operator damper is provided at the inletof APH. Access doors are provided in connectingducting for inspection of air heater tubes.

Hot primary air is then connected to WindboxCompartments below Combustor (Bedplate) frombottom & hot secondary air to SA duct to furnace.

Following are the attachments to APH inlet

duct:

Aerofoil AFM-200 for total air flowmeasurement.

Pressure Indicator ( Draft Gauge)DG-200with isolation valve A1 for remote indication inpanel.

Following are the attachments to APH outlet

duct:

Pressure Indicator ( Draft Gauge)PG-202withisolation valve A-3for remote indication in

A pneumatically operated inlet guide vane damperis provided at PA fan inlet, to maintain the

required pressure at the fan outlet. The actuatoris provided with limit switches for 0% positions,which are used as safety interlocks for fan startpermissive. Tight shut-off dampers are providedat the upstream & downstream of PA fan, toisolate fans in case of maintenance. A pressureIndicator ( Draft Gauge DG-300 with IsolationValve (A6) is provided at common outlet duct forindicating the Primary Air pressure to fuel feeding

system.

To minimise the forces due to possible movementof the discharge ducts on the fan, as well as toisolate fan vibrations being passed on to the duct,the fans are connected to the discharge ductthrough bellow type expansion joints.

6.5 Air Ducts

6.5.1 Combustion Air To Windbox

Hot air duct after APH terminates to 3compartments in the windbox through branchducts. The main duct is branched into 6ductsand connected to each compartment throughpneumatically operated dampers. Start up 1st,


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30 nozzles of 33.4 O.D x 2.87 thk pipe inclinedhorizontally. Ducting is provided with damper at

the inlet of Header to adjust the air pressure.A pressure pocket and test pocket is providedeach on LH and RH OFA headers.

6.5.3 Secondary Air Duct To Air spreadingnozzle

A Secondary air tapping is taken from APH fanoutlet duct. One main branch is taken from the

APH outlet duct, which is further divided into twosub-branches, One branch is connected to theHEADERS 1 & 2 on both sides and other branchis connected to the HEADERS 3 & 4. And one

another branch is connected to Air spreadingnozzle, which is used for Fuel spreading inside

the furnace. Manual dampers are provided atinlet of air spreading nozzle on both LHS & RHS.

Boiler RHS & LHS Air spreading nozzles arelocated at733-mm &1408-mm distance from C/Lof IB Evaporator bottom header. This spreadingnozzle consists of Holes & Openings.

Sufficient Ducting supports are provided atsuitable locations to strengthen the branch ducts.

Sufficient Expansion Bellows had been providedat suitable locations in air ducts to take care ofthermal expansion.


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7 Flue Gas System

Flue gas from the furnace passes through S.Hcoils, Convection bank tubes, Economiser coils,Air Pre-heater tubes and ESP to I.D Fans. Fromthe I.D fan gas is blown through chimney toatmosphere..

7.1 System Description

Combustion products of gases exits from thefurnace and passed to S.H zone. Furnace isprovided with the following attachments in thefluepath.

Furnace pressure transmitters, PT-100withisolation valvesFG- 1and Pressure IndicatorPIC100are provided to Measure FurnacePressure

Furnace pressure high and low alarm / trip(PAHH-100 & PAH-100, PALL-100 & PAL-100)are also generated from above transmitters.

A Temperature Elements 3 no (TE-102 A B C)at the top of the furnace.

Temperature Element (Tag no. TE-100) withtemperature indicatorTI-100at the topside forthe measurement of the fluegas temperature at

Temperature Indicators

Flue gas temperatureat Air-heater outlet

(TE-109)

Flue gas temperatureat ID fan inlet

(TI-110)

Pressure Indicators ( Draft Gauge)

Flue gas pressure atEconomiser inlet

(DG-106)

Flue gas pressure atEconomiser outlet

(DG-107)

Flue gas pressure atAir-heater outlet

(DG-108)

Flue gas pressure at IDfan inlet

(DG-109)

O2 Analyser

A probe connection to measure the O2 %by O2Analyser Tag no AP is provided in ID Fan Inletduct.

7.2 Electrostatic Precipitator (ESP)


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required furnace Draught. The VFD receivesinput signal from furnace pressure indicating

controller (PIC-100).Also two manual field operated dampers areprovided at fan inlet & outlet duct. PressureGauge DG-109are provided on individual ID faninlet duct for remote indication.

To minimise the force due to possible movementof the discharge duct on the fan, as well as toisolate fan vibrations being passed on to the duct,

the fans are connected to the duct through bellowstype expansion joints.

ID fan outlet ducts are connected to chimney.

8 Fuel Feeding & Firing System

(Refer Fuel Feeding System DRG no

F591PD-46483, R-0)

Aim

Fuel feeding system is of UNDERBED FEEDtype and the fuel is burnt in an ATMOSPHERICFLUIDISED BED COMBUSTOR. Fuel is fedthrough fuel feed ROTARY FEEDERS with thehelp of VFD driven motors into a hot fluid bed

Description Details

Fuel Size

Indian Coal: 100%< 6mm,

30% (max) < 1 mm.

Char: 100%< 3 mm

30% (max) < 1mm.

Iron particles < 0.5% bywt. Coal:

Non caking type.

Feeders Type andSize

Horizontal , Dia 208 mmx 625mm Long.

8.1 Fuel Bunker

From the fuel processing plant the fuel enters thefuel bunker of different capacities as mentionedabove, through belt conveyors.

Fuel is stored in separate bunker and fed throughfeeders to a chute above Rotary Feeders and thenfed to boiler through under bed feed system.

A manually operated isolating sliding gate isprovided at the bottom of bunker, before fuelenters chute above Rotary feeders. By isolating


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8.5 Bed Drain System

To maintain bed level and to drain out bed ash /shale / stones etc from the fluid bed Combustor,Manual ash drainpipe per compartment isprovided to the Combustor with slide gate, atsuitable locations..

8.6 Ash Drain

During the boiler operation ash is generated in the

Combustor. Fine ash goes along with the flue gas,which will be collected in the ESP, and the coarseparticles remain in the bed and gradually increasethe bed level.

Bed ash quantity depends upon the ash contentin the fuel, foreign materials like stones and shellsetc. Since bed height needs to be maintained fortrouble free operation, it is necessary to drain the

excess material to maintain the desired level.

9 Chemical Dosing & SamplingSystem

Chemical dosing system consists of chemicaldosing tank with two pumps with motorisedagitator interconnecting piping, valves and

One mixing water connection, one drain, oneover flow connection with isolation valves, one

motorised agitator for proper mixing of the solutionand a perforated screen at the inlet to avoidforeign material entry.

Two pumps with motors are mounted on the baseframe. One pump is operating while another isstand by.

Pump suction line is tapped of from the bottom ofthe tank. It is connected to the pump through an

isolation valve and a strainer. A direct connectionof the DM water is given in between strainerand isolation valve for flushing of the dischargepiping & strainer. Pumps are high precisionpositive displacement type, in which feedingvolume can be controlled. In the dischargeline a pulsation dampener is given to dampenintermittent discharge from the pump. After thatone NRV, a pressure gauge and isolation valveis provided. One relief valve to maintain thepressure in the system is given.

(Please refer Vendor Manual for relief valve set

pressure)

Discharge of the relief valve is connected backto the tank. Pressure gauge is provided witha Snubber and a Diaphragm, snubber helps to


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the chemically concentrated water is replaced withthe clear water; thus choking of piping can be

avoided.Please refer Vendor manuals for technical data

& safe Operation and Maintenance of dosing

system.

9.3 Sampling System

Sampling system consisting of sample cooler andthe cooling water sub-system for providing steams

& waters samples suitable for SWAS system.

Sample Coolers

There are three sample coolers provided on theboiler for the Feed water sample, Drum watersample and Superheated Steam sample.

The sample coolers are simple shell and coiltype heat exchangers. In these sample coolers,

the sample is passed through the coils while thecooling media is passed around the coils on theshell side.

Individual sample coolers are provided withisolation valves on the cooling water inlet &cooling water return lines. The cooling water isprovided from the plant via the terminal point atpressure of 3.5 Kg/cm2 (g) & temp. 33 Deg C.

The supply & return line is provided with isolationvalves


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Section C

Topics Covered in this Chapter

Boiler Start UpOperational ControlBalance of Plant Start Up (Boiler)Part Load Operation By Bed SlumpingWarm / Hot Start UpBoiler ShutdownDos and DontsControlsTroubleshooting ChartWalkdown Checklist during OperationBoiler SafetyOperational Precautions for Safety

Section Overview

This section describes the start-up and shutdownprocedures of the boiler.

Note

The procedures explained in this section applyfor start up of a boiler already commissioned.Commissioning a new boiler call for severaladditional requirements, which are not explainedhere.

knowledge of all components their design,purpose, limitations and relationship with other

components is must for the operators.

1 Boiler Start Up

This chapter describes the boiler start up and shutdown procedures as applicable for the followingboiler conditions:

1. Start up of a cold boiler

2. Start up of a warm / Hot boiler3. Boiler shut down

NOTE

Procedures explained in this chapter applyfor start up of the boiler already commissioned.Commissioning a new boiler calls for severaladditional requirements.

It is assumed that operators are fully familiar withthe design and construction features described inthe earlier section.

It is assumed that Operators are trained inoperation of similar type of boilers and have beenlicensed to operate boilers by the State Boiler

Authority.


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1. Furnace, Super heater and convection bankarea are clear, all maintenance personnel

have been removed and no scaffolding orinspection devices have been left inside.

2. Furnace floor, water wall and convectiontubes are clean and there is no evidence ofany water drips, slag or any other deposits.

3. Steam drum is clean and manholes are closedproperly.

4. Confirm the evaporator and furnace wall drain

valves are in closed position.

5. Verify the in-bed super heater supports areintact and in its rest position

6. Verify that all access doors, inspection doorsof furnace and wind box are tightly closed.

7. Verify that all peepholes have been tightlyclosed and sealing/ cooling air connections

are intact and the air valves are open.8. Verify that the air duct, windbox, economiser,

air pre-heater, dust collecting equipmentsand flue gas ducts are clear and thatall maintenance personnel have beenwithdrawn. Ensure that the manhole doorsclosed properly.

9. Verify that the safety valves are not gagged.

5. Verify that the drains and vents of standpipesprovided for level transmitters, indicator &

gauges are closed.WATER DRUM

1. Close the IBD line isolation valve(D-3 ) andthe IBD valve (D-4).

ID, FD & PA FANS

1. Check that the fan inspection doors areclosed.

2. Ensure that the bearing lubrication is doneproperly.

3. Check that the coupling and guards areinstalled properly.

4. Check that the manual isolation dampers atinlet and out of the fan are kept closed.

5. Ensure that the control damper actuator is

properly fixed to the operating lever and airsupply is open to actuator and I/P Converter.

DEAERATOR

(DEAERATOR IS NOT IN THE SCOPE OFSUPPLY, YET FOLLOWING ARE THE CHECKSTO BE DONE PRIOR TO START UP OF THEBOILER)

O &


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4. Check that the manual isolation valves atpump suction, minimum re-circulation and

balancing lines are kept in open position andthe discharge valves are close position.

5. Check that the cooling water supply isavailable.

FEEDWATER AND SPRAY WATER LINE

1. Select the drum level and feed water flowcontrollers( LCV-120)in manual mode andclose the control valves (FCV-500B ) alsoclose the bypass motorized control valve 100%W-17. and 30% FCV500B

2. Open the isolation valves of 40 % controlvalve.

3. Select steam temperature controllerTIC 604in manual mode with 0% output

4. Close the manual isolation valves of the

spray water control valve (W34 & W34) forAttemperator, along with the bypass valve(W35).

SAMPLE SYSTEM

1. All the sample lines isolation valves to beclosed. Sample coolers can be taken intoservice once the boiler is pressurised.

ROTARY FEEDER

1. Verify the bearing lubrication is done properly.

2. Confirm the tightness of the drive chain.

3. Confirm the tightness of the feeder chain.

4. Open the slide and rod gate above the feederand admit the coal to the feeder.

5. Confirm the outlet chutes are clear with outany blockages.

UNDER BED FIRING SYSTEM1. Pa nozzle bolts tightness to be checked.

2. Pa line/duct leakage to be checked.

3. Pa line blockages to be checked.

4. Dampers proper operation to be checked.

5. Verify the open/close operation of thecompartment PA damper and keep the

damper in close position.6. Verify the individual pipe isolation vales are in

open position.

APH

1. Ensure the soundness of the tube rollingjoints.

2. Verify tube ends are clean without erosion.

O ti & M i t M l


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5. Pilot gas [LPG] up to terminal point isolationvalve.

6. LDO tank isfilled with sufficient quantity.7. LDO pump is ready for operation.

8. Ensure cooling water supply to the variousequipments.

9. Coal bunker isfi lled up with specified coal.

10. Lime stone bunker is fi lled with limestone.

11. Availability of initial filling and makeup bedmaterial.

12. Availability of chemical for feed and boilerwater treatment.

13. Availability of lubricants for normal operation.

14. Ash handling system is ready for normaloperation.

1.1.2 System Line UpPRELIMINARY REQUIREMENTS

1. Power supply: Ensure that the power supplyis switched ON and available for all thefeeders in MCC and for all panels.

2. Operating station -is ensured for readinessand emergency push buttons are released, ifactivated.

1. Start the feed water pump as per the start upprocedure. On confirming the pump start-up,

open the fi

lling line isolation valve gradually.Valve to be opened in such a way that the loadon the pump motor is with in the operatinglimit. Since there is no backpressure from theboiler side at this stage, pump outlet pressurealso to be maintained by manipulating thevalve opening.

2. Close the economiser air vent, on confirmingthe free flow of water from the vent outlet.

Continue the filling, till the water level insteam drum reaches to 50mm below thenormal operating limit. Stop the pump afterfilling and close the drain valves at furnacebottom headers, economiser bottom headerand water filling line isolation valves & openthe furnace drain header isolation valve.

While filling the water care should

be taken to maintain the metal

temperature above 21C to avoid

brittle fracture.

Hence, the water temperature must be

maintained to meet this requirement.



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accumulation of material at the drop point andrestrict the fluidisation of bed material at this

location.13. Bed material shall be filled up-to 275 to

300mm heights above the bubble cap top,which is to be verified physically.

14. Prior to confirm the bed height, it isrecommended to fluidise the compartmentsthoroughly to spread the material uniformly. Itmay require fluidising the compartments one

by one with higher windbox pressure so as todistribute the bed materials evenly across thecombustor.

15. On confirming the uniform distribution of bedmaterial, it is a must to study the minimumfluidisation windbox pressure. Record theminimum fluidisation windbox pressure andairflow for the start-up compartment as the

same is a guiding parameter during coalfiring.

16. After confirming the minimum fluidisationwindbox pressure, start-up compartment(only) bed height to be increased to 450mmabove the bubble cap by adding additionalbed material.

3. After completion of fluidisation check. Feeddry charcoal uniformly over entire (start up

compartment) bed, afterwards feed charcoalmixed with kerosene into the bed and spreadit evenly across the complete start up (overdry charcoal). Ignite the charcoal by throwinga burning cotton waste

4. After ensuring fire over the entire bed, startID, FD fans, increase the airflow gradually tobring the charcoal to red hot condition by thistop level bed material will start getting heated

up. After achieving the above conditionmixing of the bed should be carried (such thatall the burning charcoal get mixed up with thebed material) by using the damper markingsestablished during fluidisation check. After2- 3 minutes reduce the airflow to minimum(i.e.; minimum bubbling). All the burningcharcoal will disappear for a little while asthey get covered with the bed material. Withina short period, the whole surface againwill start glowing due to charcoal burning,carefully observe bed temperature raise andcorrespondingly increase the airflow to raisethe temperature more than 600 degrees.If required, add charcoal to the bed forraising the bed temperature. Once the bedtemperature of 600 Deg C is achieved, then



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bed material, which will result in more inbedarea immersion, the bed temperature can bebrought under control..

6. The High and Low set points for the bedtemperature should be set at 900 and 650Deg C. respectively. During start-up, theLow temperature set point can be set belowambient temperature and after start-up, re-setagain at 650 Deg C.

7. During start up it is advisable to go with the

specified fuel and after complete stabilisationof the boiler with recommended bed height,combination fuels can be started. Ultimatecare to be taken to avoid higher bedtemperature than recommended,

2 The following are the predicted normaloperating parameters for the start up.

Bed temperature (Deg C) : 800-850

Fluidizing air pressure (mmwc) : 550-575

1. Close the drum vent valve when the pressurereaches to 2 kg/cm2(g). Do not close the startup vent and drain valve on the S.H steam outlet header.

2. Crack open the CBD valve to avoid blockageof CBD pipe holes and sample cooler coil.

pressure is too negative all the fine fuelparticles will eitherfire close to S.H. zone orfly as un-burnt. Firing at free board is to beavoided for the protection of S.H. coils fromover- heating..

1. Increase the boiler pressure as per the coldstart up curve, to have a control on thepressure raise, rate offiring is to be varied asper the requirement.

2. At times feeder may have to be stopped, but

ensure that feeding is not discontinued for along time so that the bed temperature will bemaintained.

3. Once the boiler reaches close to the operatingpressure make preparation for charging themain steam and other distribution lines viz.opening the drain valves.

4. First open the main steam valve by-pass

valve to warm up the Main steam line also toequalise the pressure at the in/out let of theMain steam stop Valve (MSSV).

5. When ever the steam line is warm andcondensate (if any) is removed, open themain steam stop valve slowly. Fast openingmay cause sudden increase in drum leveland water carry over to S.H coils.


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During low bed level operation some of the inbedtubes surface will be exposed from the active bed,thus reducing the steam generation.

NOTE:

1. Bed level should not be less than 350mmduring boiler operation.

2. During low bed level operation, the bedtemperature may be high and possibility ofhigh bed temperature fluctuation even forsmall upset in process changes, which is to

be taken care suitably.3. While increasing the boiler load it is suggested

to increase the bed level to the required levelof around 450-500mm.

During low bed level operation if the boiler tripsnecessaryquick care to be taken to re start the unitas there is a high possibilities of faster bed coolingand furnace blackout situation may happen.

2.2 Bed Level Control

1. During boiler operation, portion of ashgenerated will be accumulated in the bedand should be drained at regular intervalsto maintain required bed level & bed bulkdensity (1250Kg/m3) for effective fluidisation

for high bed ash accumulation. Apart fromsizing, ash content in the fuel also reflects theash accumulation levels in the bed.

6. Along with fuel stones/shales also enters thefurnace which accumulates in the furnacebottom, and increase the bed bulk densityand warrants increase in wind box pressure tomaintain required airflow to the compartment.During higher bed bulk density situations, beddraining to be done frequently to remove theaccumulated stones/shells to maintain the

bed bulk density to the desired limit maximumof 1250Kg/m3 to avoid de-fluidisation andclinker formation. Also fresh bed material tobe added to maintain the required bed heightduring bed draining.

7. Restrict shales/slates and stones enteringwith coal before fed to the crusher/bunker.

Adequate arrangement to be made for picking

up these foreign particles in the conveyingsystem suitably. This is to avoid packingof bed and air-lancing, which shall lead togreater erosion of bed coils.

2.2.1 How low bed level affectsperformance?

1. Coil exposure and leads to low loads


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Bulk Density

Shape

Fusion Temperature

Ensure bed material bulk density is alwaysbetween 1000 - 1100 kg/m3. .

Whenever the boiler is to be shutdown, it isrecommended to stabilise the boiler operationwith coal firing prior to slump the bed

3 Balance of Plant Start Up (Boiler)

ASH HANDLING:

Fly ash handling system shall be started one hourprior to coal firing.

ESP

Rapping mechanism should be started one hourprior to start the firing.

Hopper and insulation heater should be switchedon 4hrs prior to charge the ESP.

4hrs. after attaining the required flue gastemperature at ESP inlet, the ESP shall becharged. However in case of disturbance innormal operation of the boiler, it is advised to

Cross check with the level indication availableat control room through the level transmitter .Stop the water supply to the deaerator whennormal water level has reached.

5. In the mean time charge the steam up tothe pressure control valve to warm up theline and keep the steam readily available forcharging into deaerator. Once, water levelhas attained NWL, then slowly admit thesteam into deaerator through the peggingsteam line. It will take minutes or one or two

hours to heat the water with pegging steam.Whenever the water temperature reaches 60to 70 0C, deaerator is ready for charging thesteam through main supply line.

6. Try to maintain a low water level beforeadmitting the steam through the main supplyline. Level may be maintained well abovethe very low level and below the centreline

of the tank. Due to direct scrubbing of steamwith warm or cold water there may be littlehammering or vibration in the storage tank.By keeping the low Water level the quantity ofthe water in the storage tank will be less andless steam will be required initially to heat it.Thus vibration or hammering can be reducedwhile pressurising the deaerator. Keepinglow water level will have to be done manually



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flow will lead to condensing of steam and willresult into reduction in deaerator pressure,even to vacuum pressure.

10. As the deaerator pressure increases thewater temperature will start increasing. If thewater outflow from deaerator is faster, thenthe temperature rise will be faster.

11. Once the level and pressure are reached theset values the controllers can be put into auto.Temperature will reach automatically to theoperating value.

12. Flash steam if any from the boiler system cannow be admitted into deaerator.

13. The vent valve on the vapour tank can bethrottled to optimise the venting steam flow.

14. In the event of taking the deaerator into line,if abnormal hammering or vacuum situation iscreated, stop admitting the steam and repeat

the whole charging process once again.

3.2 Air Pre Heater

1. When the boiler backend flue gastemperature increase above 160C, APHto be taken in line. Opening of APH inlet &bypass damper to be adjusted in such a wayto maintain the gas outlet of APH at 1640C.

may require to slump one or more beds dependupon the situation.

4.1 Bed Slumping Procedures

While slumping the bed, following proceduresmaybe followed-

1. Reduce coal feeding gradually and stop thefeeder of the compartment to be slumped.

2. Observe the dropping trend of bed

temperature, whenever the temperaturedrops steadily stop the airflow to thecompartment by closing the compartmentdamper.

3. Maintain airflow through the PA lines to clearthe lines.

4. Due to slumping of the bed, FD outletpressure may increase, which is to be

controlled to maintain the required airflow and wind box pressure for the activecompartments.

5. Adjust / increase the fuel flow to the activecompartments to meet the steam demand.Maintain the bed temperature and shouldnot increase more than 950C, or less than750C during boiler operation depending on



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1. While converting the slumped bed in toactive bed the following procedures may befollowed:

2. Open gradually the slumped bed wind boxdamper for few minutes to fluidise the beds,by observing the furnace pressure.

3. Observe the bed temperature, and whilemixing the bed temperature will rise in theslumped bed and the bed temp will drop inthe adjacent active bed, fuel flow needs to be

increased to the active bed, to maintain thebed temperatures within safe limits, above750 deg.c.

4. Meanwhile allow air to the coal feed P.A. linesand clear the vertical line of the coal feed lineand keep ready the fuel feed system to injectcoal to the compartment.

5. Open / close the wind box damper of slumped

bed and increase the bed temperature morethan 600 deg. C. and allow steady airflow tothe bed.

6. At this point fuel flow to the new bed tobe initiated, which will increase the bedtemperature in the new bed.

7. Coal flow / air flow to be adjusted to get therequired bed temperature / steam flow and

4. Start the ID Fan, FD Fan and PA Fan as perfan start-up procedure.

5. Load the ID fan to maintain furnace pressure,load the FD and PA fans with pressureof 600 and 1300 mmWC at the fan outletrespectively.

6. Open the PA compartment dampers and clearthe PA lines of the start-up compartment.

7. Once PA lines are cleared in the start upcompartment, start the fuel feeder without

delay otherwise bed may cool down rapidly.

8. Open the windbox damper such that the bedis just bubbling, ensure that fluidisation isuniform and satisfactory.

9. Gradually increase the fuel and airflow,observing the rise in bed temperature.

10. Adjust the airflow and fuel flow to stabilise the

start up bed temperature.11. Proceed with compartment transfer

procedures mentioned earlier according tosteam demand.

12. Take feed water control and furnace draft onauto mode.

13. Charge theESP if the flue gas temperature is



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of 600 and 1300 mmWC at the fan outletrespectively.

6. If the bed level is too high drain the bed andbring down the bed height to the requiredlevel.

7. Start the start up oil burner as per burner lightup procedures.

8. Repeat the cold start-up proceduresmentioned earlier and stabilise the boiler withcoal firing.

6 Boiler Shutdown

Boiler shut down can be of two types:

1. Planned Shutdown, where the operator getsadvance notice and adequate time to shutdown the boiler in an orderly manner.

2. Boiler Trip on interlock protection oremergency shutdown by the Operator.

If the shut down is only for few hours, it is notrecommended to cool the bed material.

If the shut down is for few days, it is recommendedto cool the bed material.

6 1 Planned Shut Down

11. Verify the IBD valve is closed.

12. Allow the boiler to cool naturally

13. Whenever the steam drum pressure drops to2-kg/cm2 (g), open the steam drum vent andthe start-up vent.

14. If the unit is to be shut for a short period,no personnel should be admitted to the

boiler. If the operating personnel needto enter the unit, the boiler, economiser,air heater hoppers, and the ash collection

equipment hoppers (ESP) must be emptiedof any solids and the enclosure temperaturecooled below 50

15. All solids must be removed completely fromthe boiler and the boiler temperature must bebelow 50 deg C before personal are allowedto enter for maintenance or inspection.

a) Use airflow to fluidise the bed.

b) Start the bed draining system

16. After the bed materialflow from the bed drainhas stopped, a layer of dead bed material willremain in the bed.

17. The bed material temperature must be lessthan 50 dec Cor less before any attempt



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1. Close main steam stop valve immediately

2. Continue to feed the water flow, if the water

level requires to be maintained

3. Check that fuel feeders are stopped.

6.2.2 Boiler Shutdown during sudden TubeFailure

1. In case of a sudden tube rupture followedby a severe loss of drum water level, it isadvised immediately to stop the burners /

fuel feeders, and also isolate the steam &feedwater system. This is to avoid unduethermal stresses on pressure parts. The

drum vent & start up vent have to be openedwhenever the pressure falls to 2kg/cm2 (g).Extent of the damage is to be ascertainedafter cooling the boiler completely.

2. In case of a tube failure and if the water levelcould be maintained though the fire is notlost, it is recommended to stop the boilerimmediately to avoid major damage to thepressure parts.

3. The impingement of steam & water from aleaking tube on adjacent tubes can cause

additional failure of tubes. In such cases,the normal planned shutdown procedure isimmediately implemented.



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7 Dos and Donts

DOS

1. Maintain all instruments and interlocksin goodworking condition.

2. Maintain the instrument air free from moistureand oily matters and the pressure asrecommended.

3. .All dampers must be in smooth operatingcondition.

4. Maintain fuel as per the recommendation 1. .

5. Use the bed material as per the specification.

6. Maintain bed chemistry as per the designlimits.

7. Maintain feed and boiler water as per thedesign limits.

8. Use proper lubricants as per the manufacturerrecommendation.

9. Clean all Ash hoppers, feed water andtransfer pump suction strainers, Oil gunregularly.

10. Operate the boiler within the recommendedoperating limits and Maintain proper operationlog sheets regularly.

15. Boiler surroundings and equipment must beproperly illuminated.

16. Cleared the bed material immediately to makeroom for emergency.

17. Use genuine spares.

DONTS

1. Dont by pass any instruments and safetyinterlocks.

2. Dont run the Boiler with furnace in

pressurized condition.3. Dont throttle the feed water pump balancing

leak off valve while the pump is in operation.

4. Dont operate the furnace wall header drainvalves while the Boiler is in operation.

5. Dont leave the furnace door open while theboiler is in operation.

6. Do not open the furnace manhole without thepermission from control room.

7. Do not reuse the drained bed material.

8. Do not operate the boiler with clinker.

9. Dont leave the Instrument Control Panelunattended.

10 Dont allow unauthorized persons to operate



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8 Controls

FURNACE PRESSURE CONTROL:

1. Operate Furnace pressure in auto modewith (2 to -5) mmWC as set point. Canbe switched over to auto mode afterthe stabilisation of coal firing in start-upcompartment. During bed activation andslumping control may be taken into manualmode as the air and gas flow may varydrastically during these operation.

DRUM LEVEL

1. During start-up level can be maintainedin auto mode with single element control,

till the boiler is connected to steady load.Whenever the steam flow is increased morethan 30% MCR control can be switched over

to three-element control mode.

O2 CONTROL:

1. Whenever the boiler load increase above60% and the operation is stable, O2 controlcan be taken into service. However closeobservation may be required as any upsetcondition like heavy bed, moist fuel and

fluctuating steam demand, it will be difficult tomaintain the O2 as per the predicted values.

Please refer Volume-3 , Section-6 for detailed

Control Schematic drawings and write-up.



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9 Troubleshooting Chart

This section to be used for solving problems

arising during operation.

1. Indication: Unable to maintain boiler waterconcentration

Check the probable source TubeLeak or Hideout

Probable Cause: Check Slightleakage from pitting or cracking oftube or tube seat leak.

The repair method and preventivemeasures involves the following Remove boiler from service at firstconvenient time. Hydrostatic testto be done to locate leak. Repairby welding or splicing as indicatedand as approved by insurance orState Inspection. Determine causeof failure and correct it. Operationat normal loads should put chemicalback in solution.

2. Indication: Sound of steam blowing in furnace

Repair method and preventivemeasure Remove boiler fromthe line immediately. Inspect ordetermine whether tube splicingor wholesale tube replacement isnecessary.

4. Indication: High conductivity.

Check the probable source Solidscarry over in the steam or high CO2or NH3 in boiler water.

Probable Cause: High boiler waterconcentrations, excessive waterlevel fluctuation drum baffle leakageor deposits on scrubbers.

Repair method and preventive

measure Check for baffl

e leaks insteam drum when out of service, orboiler water contamination. Check ofdegasified steam sample will indicateif CO2 or NH3 is high.

5. Indication: High gas temperature.

Check the probable source High


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Repair method and preventivemeasure When accessible andwith insurance or State approval,the cracks can be ground out andwelded, otherwise splice in sectionor replace tube. Locate & eliminatesource of expansion difficulty byinspection or hot to cold expansionmeasurements. Using tube spacerscan stop vibration.

13. Indication: External metal loss. Highlypolished area

Check the probable source Erosion

Probable Cause: Mechanicalabrasion from soot blower action.

Repair method and preventivemeasure Where accessible andwith insurance or State approvalpad weld or splice in a tube section.Eliminate channeling of steamfrom soot blowers or use tubeshields. Using tube spacers can stopvibration.

14. Indication: External metal loss. Oxidised firescale area.

Check the probable source Overheating

Probable Cause: Prolonged orrepeated overheating.

Repair method and preventivemeasure Extent of metal loss willdetermine extent of tube or tubesection replacement. Inspectionor a thermocouple installation willdetermine cause of overheating.Using tube spacers can stopvibration.


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11 Boiler Safety

11.1 Emergency Procedures

Low Water Level

Causes

1. Feedwater control system failure.

2. BFP failure

3. Tube leak

Action

Compare control room indication with gaugeglass level. If the water level fallsout of sight dueto momentary failure of water supply system, dueto negligence of the operator, due to momentaryfluctuations that might occur with extraordinarychanges in load, appropriate action should betaken at once to trip the fuel. Any decision tocontinue to operate, even if only for a short timeat a reduced rating would have to be made bysomeone in authority who is thoroughly familiarwith the circumstances that led to the emergencyand positively certain that the water level can berestored immediately without damaging the boiler.

In the absence of such a decision

1. Stop the fuel feeders and Fans immediately.

1. Feedwater control malfunction

2. Operator error

3. Instrument air supply failure4. Foaming

Action

1. Take the drum level control loop into manualmode

2. Reduce the water level immediately byoperating the intermittent blow down to

maintain the drum level3. Reduce the steam discharge rate, if

necessary

4. Start the stand by compressor if required

Furnace Puffing & Back Firing

Causes

1. Uncontrolled feeding of fuel into the furnace

2. Sudden increase in FD fan air

3. Tube rupture

4. Foaming

Action

1. Take airflow control system into manual modeand maintain the furnace pressure



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3. Evacuate or clean the furnace to the possibleextend

Conditions for Boiler Restart after FurnaceExplosion

After a case of furnace/ boiler explosion, therestart of the boiler has to be carried out onlyafter a thorough and detailed investigation& understanding of the cause of explosion.Following necessary actions have to becompleted to prevent the repeat incidence ofexplosion and before restart of the boiler.

Find out the root cause for the explosion andrectify the same.

1. Inspect the furnace for any signs of bulging ordamage to the tubes.

2. Inspect the furnace refractory for damages

3. Inspect the air andflue ducts for any signs of

damage4. Inspect the expansion bellows in the air and

flue ducts for damages

5. Inspect the economizer casing for damages

6. Assess the damage if any and rectify thesame.

7. Carry out the hydro test of the boiler. In the

event of a failure of the hydro test, identify thetubes that have failed and proceed to rectifythe same as explained in the maintenancesection.



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12 Operational Precautions forSafety

Introduction

The handling and burning of any fuel is potentiallyhazardous. Some fuels ignite more readily thanothers. Safe handling and operation demandsknowledge of the characteristics of the fuel andcareful observance of necessary precautions.

1. Operating the boiler with low feed watertemperature along with high excess air willresult in exceeding metal temperature. Thereshould be no hesitation to bring down theload on the boiler if this temperature cannotbe brought under control by other means.

2. In the case of tube failure which can beidentified by hearing the noise in the boilergallery and cross checked by differencein steam and water flow, gas and steam

temperature, the boiler should be shut-downat the earliest by regular procedure formaintenance work. Otherwise large numberof tubes may fail due to steam erosion andimpingement.

3. Entry of wet steam into superheater andfirst row or after desuperheaters will resultin removal of oxide film due to thermal

prevented by keeping a watch on economiseroutlet water temperature.

9. Carryover of salts in steam occur either due tomechanical or vapour carry over from steamdrum. Efficient drum internals can only reducemechanical carry over. Silica is always carriedover in vaporous form. Continuous monitoringof sodium and silica in steam is desirable.

10. Before operating a boiler, ensure completeknowledge of water chemistry.

11. Whenever boiler is started after a shutdown ofmore than 3 days, check all safety interlocksbefore boiler start up for proper functioning.

12. Superheater drain valve should be operatedas per recommendations.

13. The steam drum should normally be filled uptothe point when water is showing in the bottompart of the gauge glass. This is to allow for the

swell on heating and to reduce any blowingdown resulting from this cause to a minimum.

14. Firing should be maintained having regard tothe instructions for protection of superheater,which will limit the maximum gas temperaturein the superheater zone.

15. Once the boiler is boxed up, the water levelin the steam drum must be raised to the very



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22. Have a lighted torch or spark producingdevice in operation before introducing anyfuel into furnace.

23. Maintain a positive airflow through theburners into the furnace and up the stack.

24. Maintain adequate oil pressure andtemperature for atomisation & also adequatesteam or air pressure in case of steam or airatomisers.

25. Ensure operation staff alerts to all abnormal

conditions. To observe the above rules,automatic control instruction may include :-

a. Purge interlocks e.g. requiring a specifiedminimum airflow for a specific time periodsufficient to purge the setting before thefuel trip valve can be opened.

b. Flame Detector: Each burner shouldhave its own flame detector connected to

an alarm and interlocked to shut-off thefuel to the burner, it serves upon flamefailure.

c. Closed position switches for burnershut-off valves, requiring that all shut-offvalves be closed to permit opening thefuel trip valve.

d Shut-off of fuel on failure of draft fan (s)

over in vaporous form. Continuous monitoringof sodium and silica in steam is desirable.

29. Before operating a boiler, ensure completeknowledge of water chemistry.

30. The threaded portion of the burner tipshould be covered with a non-hardeninghigh temperature lubricating compound.This facilitates easier subsequent removal.(Please refer burner manual)

31. Lapped burner tips must be kept in a plastic

container to prevent damage for atomisingsteam with internally mixing type steamatomisers.

32. Whenever boiler is started after a shutdown ofmore than 3 days, check all safety interlocksbefore boiler start up for proper functioning.

Proper Handling of Access Door

1. Never open an access door while the unit isoperating.

2. Any access door can have large amountof material built up behind it even after thebed has been drained. This material will fallout when the door is opened. Bed materialcan stay hot for many days even after boilershutdown.



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Handling of Secondary Air Ports

1. The hand-operated dampers in the secondary

air nozzles will be very hot.2. While handling the dampers / ports protective

gloves should be worn and enough attentionto be given.

Handling of Solid Piles

1. Always be cautious of piles of bed material.

2. The surface of piled material may be cool in

the surface while just below the surface stillmay be very hot.

3. Bed material in a pile can stay hot for severaldays.

Handling of Furnace Ports andObservation Doors

1. Ports and observation doors are open to the

positive pressure in the furnace.2. Never stand directly in front of the ports.

3. Do not leave the poking rod in the furnace forlong. It will heat up quickly making the rod hotto handle and hazardous when it is removedfrom port.

4. Never look directly into the port or standdirectly in front of the open port If there

2. Always use a full-face mask with tinted glass.

3. Do not stand directly in front of open ports or

doors especially when they are opened.4. Use sealing air when opening the doors /

observation ports.

5. Use ear protection devices, whenever it isnecessary.

6. Wear protective gloves when working aroundthe boiler.

7. Do not use open-ended pipes for rottingobservation doors or ports.

8. Never enter drums, ducts etc. until all thesteam and water valves including the drainand blow down values have been closed tocheck and tagged.

9. Do not enter a confined space until it has beencooled below 30 C and property ventilated.

10. Completely drain the solids from the bed,hoppers etc. while entering.

11. Always use low voltage extension cords andlight bulbs with properly connected ground.

12. Never open or enter the rotating equipmentuntil it has come to a complete stop and circuitbroken i.e. open



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4. Disconnect and isolate the nitrogen purge if itwas used during the outage.

5. Open the steam drum vents and the vents.


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maintenance schedules is to make them conditionbased. In condition based maintenance, theequipment and components of the plant are

inspected daily, weekly monthly etc., as pera suggested schedule by the local operatorsand deteriorating conditions if any observed arereported. Suggested inspection program is givenin this section. Based on operator reports of suchinspection, maintenance works are planned forthe next available planned shut down. Mandatoryinspections prescribed by the vendors are alsotaken care of, irrespective of the equipmentcondition.

2.1.1Preventive Maintenance Program forValve

A preventive maintenance program for valvesonce in two years can be done with one or moreof the following works:

Dismantle the bonnet, clean the trim and valveseat, lapping them if necessary.

Cleaning the valve stem and re-lubrication ofthe operating threads

Renewing the bonnet joint, and assembling thetrim on the valve seat

Renewing the gland packing

Renewing the valve flange joint if necessary

In condition based maintenance, the equipmentand components of the plant are inspecteddaily, weekly, monthly etc. as per suggested

schedule by the local operators and thedeteriorating conditions if any observed arereported. Suggested inspection program is givenin this chapter. Based on operator reports of suchinspection, maintenance works are planned forthe next available planned shutdown. Mandatoryinspections prescribed by the vendors are alsotaken care of, irrespective of the equipmentcondition.

3 Conditioned Based Maintenance

The schedule of daily, weekly and monthlyinspections given in the following pages do notrequire a boiler shutdown and in fact can onlybe done when the boiler is in service. Threeand six monthly inspections are done utilizing anavailable planned shutdown approximately in thespecified time period.

Objective of these inspections is to ensure that:

1. The components are in trouble free condition.

2. To carry out any minor repairs or adjustmentswhich can be done with the boiler in service.



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EQUIPMENT CHECK WORK TO BE DONE

Local level gauges on steam

drum

Check illumination is proper.

Leaking valve glands.

leaking ports

Blurred level

Replace fused bulbs.

Isolate level gauge and tightenleaking glands.

Replace leaking ports.

Steam wash mica as suggestedby vendor (not to be donetoo frequently)

Comparison of levelsindicated by local level gaugewith that of remote levelindicators in the control room

Compare the levels after verifyingthere are no leaks from valves,glands etc. of the level gauge andindicators. Report discrepancies.

If there are serious discrepanciescalibration of the remote levelindicators has to be plannedimmediately.

Traces of water, oil spots onboilerfloor, buck stay beams,boiler cladding etc.

Such spots are indicat

Documents

O & M Manual for Boiler