O & M Manual

.

.

OPERATION & MAINTENANCE MANUAL FOR 2 X 20TPH WASTE HEAT RECOVERY BOILER ON COKE OVEN

SUPPLIED TO

THERMAX POWER A/C BHATIA ENERGY & STEELS LTD GUMMIDIPOONDI, TAMILNADU

THERMAX PROJECT NO.: PL 0501 – 02

THERMAX LIMITED BOILER & HEATER GROUP PUNE, INDIA PSK & SD

23.07.2010

PREPARED BY

AA

23.07.2010

CHECKED BY

USU

23.07.2010

APPROVED BY

0

REVISION DESC. / REMARK

Operation & Maintenance Manual

Contents Volume 1 — Boiler Description ....................................................................................................1 Section A................................................................................................................................2 1 Design SpeciÞcation of WHRB ....................................................................................2 2 Flue Gas Data ............................................................................................................2 3 Technical SpeciÞcation ................................................................................................3 3.1 Flue gas Velocity proÞle: (for design case) ..........................................................3 3.2 Flue gas Temperature proÞle:(For Design case)...................................................3 3.3 Water / Steam Temperature proÞle: (For Design case) ........................................3 3.4 Flue gas Pressure drop proÞle: (for design case) .................................................4 4 MOC And SpeciÞcation of Euqipments .........................................................................4 4.1 Steam Drum ......................................................................................................4 4.2 Superheater- II ..................................................................................................4 4.3 Superheater IA / IB / Support Coils .....................................................................5 4.4 Evaporator / Convection Bank Tubes ..................................................................6 4.5 Economiser .......................................................................................................6 4.6 Attemperator .....................................................................................................7 4.7 Insulation ..........................................................................................................7 4.8 Blow Down Tank ................................................................................................7 5 Utilities .......................................................................................................................7 5.1 Electrical power .................................................................................................7 5.2 Cooling Water....................................................................................................8 5.3 DM Water..........................................................................................................8 5.4 Instrument Air....................................................................................................8 5.5 Deaerator Steam ...............................................................................................8 5.6 Chemicals for Dosing .........................................................................................9 6 ID Fans ......................................................................................................................9 7 Deaerator ...................................................................................................................9 8 HP/ LP Dosing System ................................................................................................9 9 Boiler Feed Pump ..................................................................................................... 10 10 Soot Blower ............................................................................................................ 10 11 Gauge Glass ........................................................................................................... 11 12 Safety Valve............................................................................................................ 11 13 Safety Relief Valve .................................................................................................. 12 14 EMR Valve.............................................................................................................. 12 15 Gauge Glass........................................................................................................... 13 Section B.............................................................................................................................. 14 1 Section Overview ...................................................................................................... 14 2 Water And Steam System.......................................................................................... 16 2.1 Component Description.................................................................................... 16 3 Boiler Pressure Part Description................................................................................. 19 3.1 Economizer ..................................................................................................... 19 3.2 Steam Drum .................................................................................................... 20 3.3 Silencer .......................................................................................................... 22 3.4 Air Vent ........................................................................................................... 22 3.5 Evaporator ...................................................................................................... 22 3.6 Super Heater .................................................................................................. 23 3.7 Super Heater I ................................................................................................. 23 3.8 Attemperator ................................................................................................... 23 3.9 Super Heater II ................................................................................................ 23 3.10 Steam Temperature Control Loop ................................................................... 23 4 Main Steam Piping .................................................................................................... 24 5 Operational Control .................................................................................................. 24 5.1 Steam and Water System Technical Performance Data ...................................... 25

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Operation & Maintenance Manual

6

Boiler Blowdown System ........................................................................................... 25 6.1 Other Drains.................................................................................................... 26 6.2 Continuous Blow Down Control ........................................................................ 26 7 Chemical Dosing & Sampling System......................................................................... 27 7.1 HP Dosing System........................................................................................... 27 7.2 Mixing Tank ..................................................................................................... 27 7.3 Preparation of 5% Phosphate Solution in the tank.............................................. 27 7.4 Phosphate Dosing Pump.................................................................................. 27 7.5 Water And Steam Quality Control And Monitoring .............................................. 29 7.6 Maintaining Quality of Steam ............................................................................ 30 7.7 Operational Control.......................................................................................... 31 8 Flue Gas System ...................................................................................................... 31 8.1 System Description .......................................................................................... 31 8.2 Operational Control.......................................................................................... 32 9 Soot Blower System .................................................................................................. 32 9.1 Soot Blower..................................................................................................... 32 10 Boiler Protection & Interlock ..................................................................................... 35 10.1 Alarms And Interlocks .................................................................................... 35 10.2 Operational Control........................................................................................ 35 10.3 Automatic Control .......................................................................................... 35 Section C ............................................................................................................................. 38 1 Section Overview ...................................................................................................... 38 2 Operation Procedure ................................................................................................. 38 3 Pre-requisites to Be Attended Before Start up ............................................................. 38 3.1 Feed Water Supply .......................................................................................... 38 3.2 Valve Settings ................................................................................................. 38 3.3 Filling With Water............................................................................................. 39 3.4 Heating Up ...................................................................................................... 39 4 Boiler Start Up .......................................................................................................... 40 4.1 Cold Start Up Procedure .................................................................................. 40 4.2 Hot Startup Procedure .................................................................................... 42 5 Boiler Shutdown........................................................................................................ 42 5.1 Normal Shutdown Procedure............................................................................ 42 5.2 Emergency Shutdown Procedure...................................................................... 43 5.3 During Black - Out Procedure Condition ............................................................ 43 5.4 Operator Action Required During Boiler Cold Start up ........................................ 43 6 Paralleling WHRB To The Plant steam Mains .............................................................. 43 7 Cooling of Shutdown WHRB & Its Preservation ........................................................... 44 7.1 System Description .......................................................................................... 44 7.2 Natural Cooling................................................................................................ 44 7.3 Forced Cooling ................................................................................................ 44 8 Do’s and Dont’s......................................................................................................... 44 9 WHRB Log Sheet...................................................................................................... 46 10 Emergency Procedures ........................................................................................... 48 10.1 Low Water Level ............................................................................................ 48 10.2 High Water Level ........................................................................................... 48 10.3 Tube Failure .................................................................................................. 48 11 Alarms and Interlocks .............................................................................................. 49 12 Troubleshooting Chart ............................................................................................. 51 13 Water Quality Recommendations ............................................................................. 54 14 Safety In WHRB House ........................................................................................... 55 Section D ............................................................................................................................. 56 1 Section Overview ...................................................................................................... 56 2 Recommended Maintenance Practices....................................................................... 56 3 Preventive Maintenance ............................................................................................ 56

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Operation & Maintenance Manual

3.1 Preventive Maintenance Program for Valve ....................................................... 57 3.2 Preventive Maintenance Program for Spares..................................................... 57 4 Conditioned Based Maintenance................................................................................ 57 4.1 Daily Checks ................................................................................................... 57 4.2 Daily Maintenance ........................................................................................... 60 4.3 Monthly Checks ............................................................................................... 60 4.4 Checks Every Six Months................................................................................. 61 4.5 Checks Every Year .......................................................................................... 61 4.6 Annual Maintenance Check Sheet .................................................................... 62 5 Boiler Annual Maintenance and Overhaul ................................................................... 67 5.1 Planning Before Overhaul ................................................................................ 67 5.2 Shutdown and Cooling the Boiler ...................................................................... 67 5.3 Inspection after Cooling.................................................................................... 67 5.4 Drum Inspection .............................................................................................. 67 5.5 Inspection of Screen, Primary & Secondary Superheaters, Evaporators I/II & Economiser................................................................................................ 68 5.6 Expansion Joints ............................................................................................. 68 5.7 Insulation and Cladding.................................................................................... 68 5.8 Other Equipment ............................................................................................. 68 5.9 Feed & Boiler Water Conditioning ..................................................................... 68 6 Boiler Preservation Procedure.................................................................................... 71 6.1 DeÞnition of Water Quality ................................................................................ 71 6.2 Dry Storage Preservation ................................................................................. 71 6.3 Wet Storage Preservation ................................................................................ 72 6.4 Nitrogen Blanket .............................................................................................. 73 6.5 Hot Draining .................................................................................................... 73 6.6 Alkaline Water Dozed With Hyderzine ............................................................... 74 6.7 Preservation of Extra Surfaces of Pressure Parts of WHRB During Long shutdown ................................................................................................... 74 6.8 Boiler Lay Up Procedures................................................................................. 75 6.9 Preservation of Rotating Equipments ................................................................ 75 6.10 Preservation of Instruments ............................................................................ 75 6.11 Tube Thickness Survey .................................................................................. 75 7 Tube Failures............................................................................................................ 76 7.1 Tube Failure Investigation / Analysis Method ..................................................... 76 7.2 Tube Thickness Survey Data Collection – Format .............................................. 78 7.3 Failure Reporting Formats ................................................................................ 78 8 Welding Procedure SpeciÞcations .............................................................................. 80 8.1 Window Patch Welding .................................................................................... 80 9 General Principle Of Weld Repairs ............................................................................. 81 9.1 Furnace and Boiler Tubes ................................................................................ 81 9.2 Weld Repair Of Small Cracks in Tube ............................................................... 82 9.3 Plugging Tubes in Drums & Headers................................................................. 82 9.4 Replacement of Tube Section........................................................................... 84 9.5 Removing Tubes from Drums, Headers & Tube Plates ....................................... 84 9.6 Plugging of Tubes Drawings ............................................................................. 84 10 Water Chemistry ..................................................................................................... 93 10.1 Undissolved and Suspended Solid Materials ................................................... 93 10.2 Dissolved Salts and Minerals .......................................................................... 93 10.3 Dissolved Gases............................................................................................ 94 10.4 Other Materials .............................................................................................. 94 10.5 pH Value of the Water and its Importance ........................................................ 94 10.6 Effects of Impurities ....................................................................................... 94 Section E.............................................................................................................................. 97 1 Lubrication Schedule ................................................................................................. 97

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Operation & Maintenance Manual

Volume 2 — Drawings................................................................................................................ 98 List of Drawings .................................................................................................................... 99 Volume 3 — Drawings.............................................................................................................. 100 E & I SpeciÞcations ............................................................................................................. 101 Section 01 ................................................................................................................... 101 Section 02 ................................................................................................................... 101 Section 03 ................................................................................................................... 101 Section 04 ................................................................................................................... 101 Section 05 ................................................................................................................... 101 Section 06 ................................................................................................................... 101 Section 07 ................................................................................................................... 101 Section 08 ................................................................................................................... 101 Section 09 ................................................................................................................... 101 Section 10 ................................................................................................................... 101 Section 11.................................................................................................................... 101 Section 12 ................................................................................................................... 101 Section 13 ................................................................................................................... 102 Section 14 ................................................................................................................... 102 Section 15 ................................................................................................................... 102 Volume 4 — Vendor Manuals ................................................................................................... 103 Section 01 .......................................................................................................................... 104 Pressure Transmitter — Emerson.................................................................................. 104 Section 02 .......................................................................................................................... 104 Temperature Transmitter — Emerson ............................................................................ 104 Section 03 .......................................................................................................................... 104 Pressure Switch — Switzer Instruments......................................................................... 104 Section 04 .......................................................................................................................... 104 4.1 Pressure Gauge — Gauges Bourdon ....................................................................... 104 4.2 Temperature Gauge — Goa Instruments .................................................................. 104 Section 05 .......................................................................................................................... 104 Power Cylinder — Keltron ............................................................................................ 104 Section 06 .......................................................................................................................... 104 Loop Power Indicator — Switzer Instruments ................................................................. 104 Section 07 .......................................................................................................................... 104 I to P Converter — ABB ................................................................................................ 104 Section 08 .......................................................................................................................... 105 8.1 Flow Nozzle — Starmech Controls........................................................................... 105 8.2 Thermocouple — Thermal Instruments..................................................................... 105 Section 09 .......................................................................................................................... 105 Control Valves— MIL .................................................................................................... 105 Section 10 .......................................................................................................................... 105 Motorised Valve Actuator— Auma India Ltd.................................................................... 105 Volume 5 — Vendor Manuals ................................................................................................... 106 Section 01 .......................................................................................................................... 107 ID Fan - Flakt Woods.................................................................................................... 107 Section 02 .......................................................................................................................... 107 BFW Pump — KSB Pumps .......................................................................................... 107 Section 03 .......................................................................................................................... 107 LP / H.P Dosing System - Metapow Industries................................................................ 107 Section 04 .......................................................................................................................... 107 4.1 Long Retractable Soot Blower - R.R. Techno ............................................................ 107 4.2 Rotary Soot Blower - Sitson India Ltd. ...................................................................... 108 Section 05 .......................................................................................................................... 108 5.1 Motors— Siemens .................................................................................................. 108

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Operation & Maintenance Manual

5.2 ARC Valve — Schroedahl........................................................................................ 108 Volume 6 — Vendor Manuals ................................................................................................... 109 Section 01 .......................................................................................................................... 110 Safety Valve – Tyco Sanmar ......................................................................................... 110 Section 02 .......................................................................................................................... 110 Safety Relief Valves — Tyco Sanmar............................................................................. 110 Section 03 .......................................................................................................................... 110 Drum Level Gauge — Hitech......................................................................................... 110 Section 04 .......................................................................................................................... 110 Level Gauge (Tubular ) – Chemtrol ............................................................................... 110 Section 05 .......................................................................................................................... 110 Reßex Level Gauge — Chemtrols.................................................................................. 110 Section 06 .......................................................................................................................... 111 Process Valve — KSB ................................................................................................. 111 Section 07 .......................................................................................................................... 111 Process Valve — Xomox Sanmar .................................................................................. 111 Section 08 .......................................................................................................................... 111 Blow Down Valve — Levcon Instruments ....................................................................... 111 Section 09 .......................................................................................................................... 111 9.1 Spring Hanger Support — Techno Industries ............................................................ 111 9.2 Hanger Support – Pipe Support ............................................................................... 111 Section 10 .......................................................................................................................... 111 Damper - United Technomech Engineers Pvt. Ltd. ......................................................... 111 Index.................................................................................................................................. 113

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Operation & Maintenance Manual

vi

Operation & Maintenance Manual

Volume 1 — Boiler Description Chapters Covered in this Part ♦ ♦ ♦ ♦ ♦

Section Section Section Section Section

A B C D E

Volume 1 — Boiler Description

1

Operation & Maintenance Manual

Section A Topics Covered in this Chapter ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦

1

Design SpeciÞcation of WHRB Flue Gas Data Technical SpeciÞcation MOC And SpeciÞcation of Euqipments Utilities ID Fans Deaerator HP/ LP Dosing System Boiler Feed Pump Soot Blower Gauge Glass Safety Valve Safety Relief Valve EMR Valve Gauge Glass

Design Specification of WHRB

NUMBER & TYPE OF BOILER Two nos. 20-TPH, Water tube, Natural Circulation, Single-Drum Coke Oven WHR Boiler. Bottom Supported Pressure parts PARAMETERS

UNIT

VALUE

Boiler Rating [MCR]

TPH

20

Steam Pressure at Main Steam Stop Valve Outlet from minimum Load upto MCR

Kg/cm2

66

Steam Temperature at the Main Steam Stop valve at MCR

Deg C

485±5

Main Steam Temperature Control range at the Main Steam Stop Valve Outlet (@ 950 deg C Inlet Flue Gas Temp)

% MCR

60 – 100

Maximum allowable working pressure

Kg/cm2

75

Hydraulic Test Pressure

Kg/cm2

112.5

Design Pressure

Kg/cm2

75

Boiler Performance Testing Procedure

ASME PTC 4.4 Energy Balance

DESIGN CODE

ASME SECTION-1

2

Flue Gas Data

PARAMETERS

VALUE

Boiler Rating [MCR] Nm3/Hr ( Per Boiler)

52,935

Inlet Temperature °C

950

Section A

2

Operation & Maintenance Manual

PARAMETERS

VALUE

Outlet Temperature °C

180 ± 5

Flue Gas Composition (% V/V):CO2

4.45

H2 O

6.2

N2

75.79

O2

13.45

SO2

100 ppm

Dust Loading

100 m g/Nm3

3

Technical Specification

3.1 Flue gas Velocity profile: (for design case) Sr No.

Component

Velocity, m/s

1

Radiation cavity

8

2

Superheater

12 to 15

3

Evaporator

10 to 11

4

Economiser

8 to 9

3.2 Flue gas Temperature profile:(For Design case) Sr No.

Component

Deg C

1

Radiation chamber inlet / outlet

950 / 878

Pre Evaporator cum Support Tube

2

(Pass 1) inlet / outlet

878 / 849

3

Superheater II (Pass 1) inlet / outlet

849 / 723

4

Superheater 1A (Pass 1) inlet / outlet

723 / 669

5

Superheater 1B (Pass 1) inlet / outlet

669 / 590

6

Evaporator I (Pass 1) inlet / outlet

590 / 390

7

Evaporator II (Pass 2) inlet / outlet

390 / 336

8

Inlet of Economiser

336

9

Outlet of Economiser

180

3.3 Water / Steam Temperature profile: (For Design case) Sr

Component

Deg C

1

Radiation chamber inlet / outlet

285 / 285

2 3

Pre Evaporator cum Support Tube (Pass 1) inlet / outlet Superheater II (Pass 1) inlet / outlet

Section A

285 / 285 328 / 485

3

Operation & Maintenance Manual

Sr

Component

Deg C

4

Superheater 1A (Pass 1) inlet / outlet

368 / 428

5

Superheater 1B (Pass 1) inlet / outlet

285 / 368

6

Evaporator I (Pass 1) inlet / outlet

285 / 285

7

Evaporator II (Pass 2) inlet / outlet

285 / 285

8

Inlet of Economiser

120

9

Outlet of Economiser

258

3.4 Flue gas Pressure drop profile: (for design case) Sr No.

Component (at outlet)

Pressure mmWC

1

Radiation cavity +Bends+Screen

-5

2

Superheater

-30

3

Evaporator

-85

4

Economiser

-165

4

MOC And Specification of Euqipments

4.1 Steam Drum Sr No.

Description

Value

1

Design code

IBR 1950 with its latest amendments

2

Design pressure

75 kg/cm² g

3

Design temperature

291 °C

4

Hydrotest pressure

112.5 kg/cm² g

5

Length

4000 mm

6

Inner diameter

1375 mm

7

Thickness

50 mm

8

Material of construction

SA 516 Gr 70 / Equiv.

9

Quantity per boiler

1 no.

10

Corrosion allowance

As per IBR

11

Internals

Demister pad

12

Quantity of safety valves

2 nos.

13

Capacity of each safety valve

7500 kg/hr

14

Set pressure of Þrst safety valve

74.5 Kg/cm² g

15

Set pressure of second safety valve

75 kg/cm² g

4.2 Superheater- II Sr No.

Description

Value

1

Design code

IBR 1950 with its latest amendments

2

Design pressure

75 kg/cm² g

Section A

4

Operation & Maintenance Manual

Sr No. 3

Description

Value

Design temperature SH II

529 °C

Support Coils

319 °C

4

Design temperature of headers

490 °C

5

Hydrotest pressure

112.5 kg/cm² g

6

Type

Horizontal

7

Heat transfer area(Thermal)

86.18 m²

8

Type of tubes

Bare

9

Tube outer diameter

OD 38.1mm x 4.06 mm thk

10

Tube thickness

As per IBR

11

MOC of tubes

SA 213 T22 HFS

12

MOC of Support Coils

SA 210 Gr A1

13

Safety valve relieving capacity

5000 kg/hr

14

Safety valve set pressure

71 kg/cm²g

4.3 Superheater IA / IB / Support Coils Sr No.

Description

Value

1

Design code

IBR 1950 with its latest amendments

2

Design pressure

75 kg/cm² g

Design temperature of SH IA

467 °C

Design temperature of SH IB

407 °C

3

Design temperature of support coils

319 °C

4

Design temperature of headers SH IB Inlet Header

291 °C

SH IA Outlet Header

428 °C

SH II Inlet Header

428 °C

SH II Outlet Header

490 °C

5

Hydrotest pressure

112.5 kg/cm² g

6

Type

Horizontal

7

Heat transfer area(Thermal)

43.09 m² + 71.187 m²

8

Type of tubes

Bare

9

Tube outer diameter

OD 38.1 mm x 4.06 mm thk

10

Tube thickness

As per IBR

11

MOC of SH IA tubes

SA 213 Gr T11 HFS

MOC of SH IB / support coils tubes

SA 210 T22 Gr A1 HFS

12

MOC of headers

SA 335 P11

13

Header outer diameter

OD 168.3 mm x 14.27 mm thk

Section A

5

Operation & Maintenance Manual

4.4 Evaporator / Convection Bank Tubes Sr No.

Description

Value

1

Design code

IBR 1950 with its latest amendments

2

Design pressure

75 kg/cm² g

3

Design temperature of coils

319°C

4

Design temperature of headers

316 °C

5

Hydrotest pressure

112.5 kg/cm² g

6

Type

Horizontal

Heat transfer area (thermal Area) A) Convection Panel (Pass 1)

190.05 m²

B) Pre Evaporator cum Support Tube

7.182 m²

C) Evaporator I (Pass 1)

258.54 m²

D) Evaporator II (Pass 2)

206.832 m²

8

Type of tubes

Bare

9

Tube outer diameter

OD 38.1 mm x 3.66 mm thk

10

Tube thickness

As per IBR

11

MOC of tubes

SA 210 GR A1

12

MOC of Water wall tubes

SA 210 GR A1 HFS

13

Tube OD of water wall tubes

OD 63.5 mm x 4.06 thk mm

14

Tube thickness of water wall tubes

As per IBR

15

MOC of headers

SA 106 Gr B

16

Header outer diameter

OD 219.1mm x 18.26 mm thk

17

Header thickness

As per IBR

7

4.5 Economiser Sr No.

Description

Value

1

Design code

IBR 1950 with its latest amendments

2

Design pressure

75 kg/cm² g

3

Design temperature of coils

269 °C

4

Design temperature of headers

258 °C

5

Hydrotest pressure

112.5 kg/cm² g

6

Type

Horizontal

7

Heat transfer area

827.33 m²

8

Type of tubes

Bare

9

Tube outer diameter

OD 38.1 mm x 3‘.66 mm thk

10

Tube thickness

As per IBR

11

MOC of tubes

SA 210 GR A1

12

MOC of headers

SA 106 Gr B

Section A

6

Operation & Maintenance Manual

Sr No.

Description

Value

13

Header outer diameter mm

OD 114.3 mm x 13.49 mm thk

14

Header thickness mm

As per IBR

4.6 Attemperator Description

Value

1

Type

Spray type Attemperator

2

Nos

One

3

Location

Between SH I & SH II

4

Water Flow at MCR (kg/h)

Later

5

MOC of headers

SA 335 P11

6

Header outer diameter mm

OD 219.1 mm x 12.7 mm thk x 5000mm long

7

Header thickness mm

As per IBR

8

Desidn Temperature

428 deg C

Sr No.

4.7 Insulation Description

Value

1

Type

Mineral wool mattress

2

Density

3

Cladding

Aluminum sheet of 24 SWG

4

Skin Temperature

30 Deg C above ambient temp.

Sr No.

100 Kg/M3 up to 400 Deg C 120 Kg/M3 above 400 Deg C

4.8 Blow Down Tank

5

Sr.

Description

Value

1

Design code

IBR 1950 with its latest amendments

2

Design pressure

3.5 kg/cm² g

3

Design Metal Temperature

150 °C

4

Hydrotest pressure

5.25 kg/cm² g

5

Shell Hight

1500 mm

6

Shell ID

960 mm

7

Shell thickness

10 mm

8

Type of ends

Dished

9

Material of construction

SA 516 Gr. 70

Utilities

5.1 Electrical power Parameters

Units

Value

For LT motors (UPTO AND INCLUDING 200 KW) Voltage

Section A

V

415 +/- 10%

7

Operation & Maintenance Manual

Parameters

Units

Value

Frequency

Hz

50 +/- 5%

Type

AC, 3 Phase, 4 wire

For Instrumentation (field switches, Level gauge illumination, solenoid valves etc.) Voltage

V

110

Frequency

Hz

50

Type

Single Phase, 2 wire

For Field Transmitters Voltage

V

24

Frequency

Hz

NA

Type

DC

5.2 Cooling Water Parameters

Unit

Value

Supply Pressure

Kg/cm2(g)

3–4 @ Battery Limit

Supply Temperature

Deg C

Ambient @ Battery Limit

Quality

Clear & colourless

Duty

BFP Pump cooling & Sample cooler

Quantity (for BFP pump)

Kg/Hr

1000 (Normal) , 1200 (Maximum)

Quantity (for Sample cooler)

Kg/Hr

600 (Normal) , 720 (Maximum)

Parameters

Unit

Value

Supply Pressure

KSC (g)

5 @ Battery Limit

Supply Temperature

Deg C

Ambient @ Battery Limit

Flow

Kg/Hr

1200 (Normal) , 15000 (Maximum)

Parameters

Unit

Value

Pressure

Kg/cm2(g)

5– 6

Dew point

Deg c

-40

Temperature

Deg c

Ambient

Quality

—

Oil & moisture free

Quantity

scfm

50 (continuous) & 25 (Intermittent)

5.3 DM Water

5.4 Instrument Air

5.5 Deaerator Steam Parameters

Unit

Value

Kg/cm2(g)

4.0 (Normal) , 9.0 (Maximum)

Temperature

Deg c

185

Quanlity

Kg/hr

5000 (Normal)

Pressure

Section A

8

Operation & Maintenance Manual

5.6 Chemicals for Dosing

6

7

HP Dosing

Tri sodium phosphate

LP Dosing

Hydrazine

ID Fans Sr No.

Description

Value

1

Type of fan

Centrifugal

2

Quantity

02 nos

2

Drive

Electric motor

3

Coupling

Resilient type coupling

4

Rated head

410 mmWC

5

Rated capacity

31.6 m3/sec

6

MOC of casing

IS 2062 Gr A (MS)

7

MOC of impeller

SAILMA 350

8

MOC of shaft

EN 8

9

Fan speed

980 rpm

10

Cooling water requirement

Not required.

11

Type of ßow control

By variable frequency control & Pneumatic operated multi louver damper.

12

Type of isolation

Not required

13

Type of Lubrication

Grease (Servo Gem; EP2)

Deaerator

Description

Valve

Deaeration capacity

48 m3/hr (Max)

Storage tank Capacity (Full)

27 m3

Storage tank capacity

16 m3

Operating pressure

1.76 bar(g)

Operating temperature

120° C (case 1) & 130 ° C (case 2)

Design pressure

3.0 Kg/cm2(g)

Design temperature

200 ° C

Design & Construction code

ASME SECT. VIII DIV Edition 2004, ADDENDA 2006 (WITH ‘U’ STAMPING)

8

HP/ LP Dosing System

Make : Metapow Industries Sr No.

Description

Value

1

Major parts

Storage tank – 1 no, Stirrer – 1 no., Dosing pumps – 2 nos. Storage tank Details

Section A

9

Operation & Maintenance Manual

Sr No.

Description

Value

1

Size of storage tank

600 mm x 800 mm x 5 mm

2

Tank capacity

150 liters

3

MOC of tank

IS 2062 MSRL; Rubber lined 3mm

4

MOC of chemical basket

SS 304 Dosing pump Details

1

Pump make

VK Pumps / Equiv.

2

Pump capacity (HP/LP)

0– 6 LPH

3

Pump type

Reciprocating Plunger type

4

Operating Pressure (HP/LP)

76 kg/cm2 / 6.35 kg/cm2

5

Safety Relief Valve Set Pressure (HP/LP)

102 kg/cm2 / 8 kg/cm2

6

Type of Lubrication / Quantity

ISO VG 460 / 0.8 liters

7

Motor Details

Crompton Greaves Stirrer details

9

1

Type of operation

Motorised

2

Motor Details

0.5 HP / 1000 RPM (HP); 750 RPM (LP)

Boiler Feed Pump

DESCRIPTION

UNIT

VALUE

MAKE

KSB PUMPS LTD.

Type & Size

HAD 65/15

Quantity

NO

3 (2W/1 SB)

Fluid

FEED WATER

Pump Speed

RPM

2900

Capacity

m3/hr

26

Design Head

M

960

Fluid Temp

°C

130 Gear type Spacer Coupling

Coupling Type

(Make - Rathi)

Lubrication

OIL

SERVO SYSTEM / ENKLO- 46

Motor

kW/RPM

160 /2985 (Make – Siemens)

10 Soot Blower Description

Long Retractable soot blower

Rotary soot blower

1

Location

Super heater & Evaporator Zone

Economizer Zone

2

Steam temperature deg c :

Saturated

3

Steam pressure kg/cm2(g)

20

Sr No.

Section A

10

Operation & Maintenance Manual

Description

Long Retractable soot blower

4

Source of Steam

Saturated steam from Steam Drum

5

Drive

Motorised

Sr No.

Rotary soot blower

11 Gauge Glass Drum level Gauge Description

Details

Make

HI TECH SYSTEM & SERVICES LTD

Tag No.

11– LG – 143/ 11– LG – 144 & 12– LG – 143/ 12– LG – 144

Type

Bi Colour Duco Gauge

Location

Steam drum

Operating pressure.

69 kg/cm2 (g)

Hydrotest pressure

112.5 kg/cm2 (g)

C/c distance

750 mm

Visibility Range

314 mm 5 Ports

Operating temp.

285 °C Normal Operating

Blow Down Level Gauge Description

Details

Make

Chemtrol Samil

Tag No.

11– LG– 601

Type

Tubular Level Gauge Assly

Location

Blow Down Tank

Working pressure.

5 kg/cm2 (g)

C/c distance

500 mm

Visibility range

360 mm

Operating temp.

200 °C (Saturated) Normal Operating

12 Safety Valve DESCRIPTION APPLICATION

UNIT

DRUM #1

TYPE

-

SPRING LOADED

MAKE

SH

ANDERSON GREENWOOD CROSBY

TAG NO

-

SIZE ORIFICE

-

SETPRESSUR. OPERATING TEMP.

Section A

DRUM #2

11-PSV-001

11-PSV-002

11-PSV-003

Kg/cm2

74.5

75

71

DEG.C

285

285

485

11

Operation & Maintenance Manual

DESCRIPTION APPLICATION

UNIT

DRUM #1

DRUM #2

SH

RELIEVING CAPACITY

TPH

8000

8000

6000

QUANTITY

-

1

1

1

FLUID

-

Sat Steam

Sat Steam

Sup Steam

13 Safety Relief Valve DESCRIPTION / APPLICATION

UNIT

Details

TYPE

-

SPRING LOADED

MAKE

-

TYCO SANMAR LTD

SIZE ORIFICE

-

2.5 X JX 4.0

SET PRESSURE

Kg/Sq.cm

23

Model Relieving Capacity Rated / Requried

JOS–H–E—35-C-IBR-SPL Kg/hr

QUANTITY

10595/8000 1 / BLR

14 EMR Valve DESCRIPTION / APPLICATION

UNIT

Details

TYPE

-

SPRING LOADED

MAKE

-

TYCO SANMAR LTD

SIZE ORIFICE

-

2.5 X 4.0

SET PRESSURE

Kg/Sq.cm

100

Model Relieving Capacity Rated / Requried

Section A

HPV-ST-68W-IBR Kg/hr

20611/2750

12

Operation & Maintenance Manual

15 Gauge Glass Drum level Gauge Description

Details

Make

HI-TECH SYSTEMS & SERVICES LTD.

Tag No.

LI–34101 and LI-34102

Type

Bi-Colour duco Level Gauge Assly

Location

Steam drum

Operating pressure.

101.0 kg/cm2 (g)

Rating pressure

210 Bar

Hydrotest pressure

315 kg/cm2 (g)

C/c distance

750 mm

Visibility Range

314 mm 5 Ports

Operating temp.

311 °C (Saturated) Normal Operating

Blow Down Level Gauge Description

Details

Make

Levcon Instruments

Tag No.

LI —35001

Type

Tubular Level Gauge Assly

Location

Blow Down

Working pressure.

10 kg/cm2 (g)

C/c distance

1000+/-1

Visibility range

860 mm

Operating temp.

200 °C (Saturated) Normal Operating

Section A

13

Operation & Maintenance Manual

Section B Topics Covered in this Chapter ♦ Section Overview ♦ Water And Steam System ♦ Boiler Pressure Part Description ♦ Main Steam Piping ♦ Operational Control ♦ Boiler Blowdown System ♦ Chemical Dosing & Sampling System ♦ Flue Gas System ♦ Soot Blower System ♦ Boiler Protection & Interlock

1

Section Overview

This section gives a brief overview of the boiler and its associated systems. The description of the various systems that form part of the boiler package is also included. The aim of this section is to make the reader familiar with the boiler package components before introducing the operation and maintenance sections. Brief Overview The Operation and Maintenance manual of THERMAX LTD (B & H Group) in Subsequent volumes, provide useful information, guidelines and data required for the safe operation and maintenance of the two WHRB’s supplied to M/s Bhatia Energy & Steels Ltd AT Getanamalli Tehsil, Gummudipondi, Tamilnadu. Contents of each of the volumes have been listed else where in these manuals. It is expected that the Bhatia Energy & Steels Ltd Engineers and Operators will familiarize themselves with these data before operating the boilers. The WHRB is designed to extract maximum recoverable heat from the exhaust gas of the coke oven. For this purpose the exhaust gas ßow from the oven is arranged in a direction counter to the water/ steam circuit of WHRB. The exhaust gas from the coke oven enters the super-heaters. From the Super-heaters, the exhaust gases travel through the HP boiler evaporator and economiser modules before exhausted to the atmosphere by the stack. To achieve better controllability of Þnal steam temperature on varying loads, two stage super-heater is envisaged with an inter stage spray type attemperator. The steam drum placed above the evaporator serves as a balancing vessel for water and steam.

Section B

It receives feed-water from the Economiser and maintains positive water supply to the evaporator modules. Drum receives the mixture of steam and water from the evaporator modules by the heat transfer. After separating water from the steam / water mixture at drum, the saturated steam is supplied to the super-heaters. Economisers installed behind the evaporator modules serve to preheat the feed-water fed to the steam drum recovering heat energy from the exhaust gas. General Capacity The main parameters of the boiler are Maximum Continuous Rating

20 TPH

Steam Pressure

66 kg/cm2

Steam Temperature

485+/- 5 Deg C

Generation capacity of the WHRB at the base load is 20 TPH at super-heater outlet pressure of 66 kg/cm2(g) and temperature of 485+/- 5 ° C. General description of WHRB instrumentation The latest generation of the Þeld instruments is used to facilitate monitoring and control of the process variables, generating alarms and trips. Differential pressure Transmitters for the measurement of process variables like Pressure, drum Level and Flow are used. Thermocouples with transmitters are used for the measurement of temperature. Control valves with position transmitter and proximity switches form a part of control system and act as the Þnal control element to control the process variables. Position transmitters allow the monitoring of the controlling element position. Closed control loops are conÞgured in DCS (by customer). Process switches and transmitters monitor the process variables and generate alarms and safe shutdown of WHRB.

Control Loops: Following closed loop controls are provided for the WHRB operation: • Drum level Control • Steam temperature Control • Furnace Pressure Control • Soot Blower Pressure Control • De-aerator Level and Pressure Control

14

Operation & Maintenance Manual

Control philosophy of these loops is described in the document submitted separately.

rest of boiler’s instrument and valves shall be as per the following nomenclature.

Referance Drawings:

Refer the P & I diagram for the tagging procedure.

• D12-0WH-09484 - P & ID for Waste Heat recovery Boiler – Refer latest revision.

Instrument Tagging Procedure. Tag numbers of Instruments, motorized valves, pneumatic control valves, safety valves, manual valves, & drives to be preÞxed with 10 for common items. 11 & 12 for WHRB 1 & 2 respectively

This O & M manual shall be for applicable for both the 02 boilers. The description in the manual of the instrument and valve tag no. is dealt with typically one boiler. However the tag no. for the

Section B

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Operation & Maintenance Manual

2

Water And Steam System

AIM The water and steam system covered in this chapter describes the components of the WHRB which transfer heat from the exhaust gas of the Coke oven to the feed water ßowing from the feed water main to convert it to HP steam of 66 Kg/cm²(g) at a temperature of 485 °C (±5°C). The components in the serial order of water ßow of path are, • Deaerator • Boiler Feed Water Station • Boiler Feed Control Station • Integral Economizers • Evaporators I & II • Superheater I • Attemperator • Superheater II The exhaust gas from the Oven ßows in a direction counter to the water / steam ßow path, with the hottest gas entering across Superheater II, followed by all the components mentioned above in reverse order. The exhaust gas, after transferring all its recoverable heat to the Superheaters, Evaporators & Economizers exhausted to the atmosphere through the Stack.

2.1 Component Description 2.1.1Deaerator PURPOSE OF DEAERATION Deaeration removes the corrosive gases such as dissolved oxygen and free carbon dioxide from the boiler feed water. This ensures protection of the feed water lines, steam lines, boiler tubes and other pressure parts of the boiler against corrosion and pitting, saves costly boiler re-tubing and expensive plant shutdowns. Further as the temperature of feed water is raised from ambient to Deaerator operating temperature of 120 0C or 130 0C [which corresponds to the operating pressure of 1.76 kg /cm2 (g)] and then fed to boilers through feed pumps, the overall boiler thermal efÞciency also increases. Heating the feed water with steam does deaeration. Vigorously scrubbing the water with this steam removes the last traces of non-condensable gases and brings down well below the recommended level in feed water. CONSTRUCTION FEATURE

Section B

The Deaerator supplied is of Thermal Mechanical Deaerator in which DM water/ makeup feed water is heated to its boiling temperature at the operating pressure by steam. At boiling point all the dissolved gases such as Oxygen, Carbon Dioxide, Etc. are liberated as solubility of gases decreases with increase in temperature. The mechanical scrubbing between water and heating steam ensures release of the dissolved gases. Deaerator is of spray and trays type, consists of a storage tank and a vapour tank. Water is sprayed from the top of the vapour tank by spray nozzles on set of multi level trays below it. Steam is fed from the supply pipe to the distribution headers inside the storage tank below the water level. Partial scrubbing of the steam and water takes place in the storage tank water and the rest is taking place in the vapour tank with the incoming water spray. Vapour tank is mounted upon the storage tank. Both the tanks are connected with steam connection Nozzle at the middle. This interconnection nozzle of 1000 OD is ßushed with inner wall of the vapour tank’s dished end and embedded inside the water level of storage tank to facilitate the feed water ßow from vapour tank to the storage tank. Interconnection accommodates concentrically the steam balancing connection assembly. This steam connection is projected inside the vapour tank and masked from the water ßow direction by a hood Þtted at the top, thus facilitates the steam ßow from storage tank to vapour tank. DM water enters to the vapour tank through the topside nozzle N18 to the distribution ring header. Five spray nozzles are Þxed on the ring header to spray the water into Þne particles covering the entire cross section of the tank so that easy and complete scrubbing with steam is possible. Perforated stainless steel trays at six levels are placed inside the vapour tank to provide enough delay time to scrub the feed water with the upcoming steam. Feed water from vapour tank ßows into the storage tank through the interconnection pipe. Condensate enters to the vapour tank through the topside nozzle N23 to the distribution ring header. Nozzles are Þxed on the ring header to spray the water into Þne particles covering the entire cross section of the tank so that easy and complete scrubbing with steam is possible. Heating Steam is supplied through the supply pipe (Nozzle N10) to the steam distribution headers kept inside the storage tank well below the water

16

Operation & Maintenance Manual

level. Two steam distribution headers connected to the supply pipe are lied at the bottom and along the length of the storage tank. These headers are perforated pipes to distribute the steam along the entire length of the storage tank water space. Steam rises from the bottom of Storage Tank, heating the water and rises through the interconnection pipe into the Vapor Tank. Perforated Trays inside the Vapor tank increase the residence time of water and Heating Steam. Oxygen, Carbon dioxide and other dissolved gases are vented out along with Vent Steam through the nozzle N13. The dissolved Oxygen level in the feed water by mechanical deaeration can be brought to 0.02 to 0.03 ppm. If required the residual dissolved Oxygen can be further scavenged by the reaction with chemicals such as sodium sulphite (catalyzed or un-catalyzed) or Hydrazine. By chemical scavenging the dissolved Oxygen level can be brought down to as low as 0.007 ppm. Chemical may be dosed in the storage section of the deaerator through a header. Nozzle N4 is provided for this and can be utilised. The dosing of the particular chemicals is done in predetermined quantity and concentration. A sample cooler provided in the feed water outlet piping is used to collect the sample for analysis of water. Storage tank is supported by saddle supports. One of the saddles is Þxed and the other is sliding one to take care of thermal expansion. PTFE sheets are provided under the sliding saddle for free movement of saddle. Platforms and ladders are provided for tanks and condenser for O & M feasibility. THE ACCESSORIES AND THE MOUNTINGS Deaerator Level Control The desired normal water level (NWL), which is maintained through a level control valve [10-LCV 102] of DM water line & condensate return line. Level in the storage tank is monitored remotely by the level transmitter [10-LT 102 A & B ]. Two nozzles (N11 A/B) at this elevation are provided for LT connection at distance of 301 mm above and 1392 mm below the NWL. A Feed back control loop with the electronic controller [10-LIC 102] is provided for automatic level control. Process variable signal for the level controller is transmitted by the [10-LT 102 A & B ]. Set point of the level controller is to be kept at ’0’ mmWC, which corresponds, to NWL.

Section B

Apart from this remote level indication direct level gauge glass [10-LG 103 & 104] are provided to cover the height between very low level and upto over ßow level. These level gauge are mounted on a water column connected to the Nozzles N10 A/B Over Flow Shut Off Valve [10-XV 109] shut off valve is provided to drain the excess water from deaerator if level increases beyond recommended value. Connection N6 is assigned for that. Pressure Control The deaerator operating pressure of 1.76 kg/cm2(g) is maintained by the pressure control loop, which contains the pressure control valves [10-PCV 105] in the steam line, a pressure transmitter [10-PT 105] mounted on the storage tank nozzle N12 and an electronic pressure indicating controller [10-PIC 105] in the control room. Set point for the pressure controller shall be kept at 1.76 kg/cm2 (g). Pressure Relief Valve (10-PSV 005) A Nozzle N17 is provided at the top of vapour tank to mount a relief valve. Relief valve would relieve the steam at the design set pressure of 3 bar(g), when there is excessive pressure build-up inside the vessels (system) incase of sudden reduction of water out ßow/ intake to deaerator or malfunctioning of pressure control loop. Temperature Gauge A temperature gauge [10-TE 107] is Þxed on to the storage tank nozzle (N14). Vacuum Breaker A Vacuum Breaker assembly consists of Non Return Valves directed towards vapor Tank from atmosphere mounted on the Nozzle N18. This is to prevent Deaerator from operating at vacuum or negative Pressure. Vacuum condition inside the Deaerator would mean that the Deaerator is not being supplied with enough Steam with respect to the water ßow leading to condensation of heating Steam. In case the Deaerator happens to go under vacuum, atmospheric air will rush through these Non Return Valves breaking the vacuum. Air vent Air vent is provided (nozzle N2) on topside of the vapour tank. Air vent is provided with an oriÞce and a globe Valve in parallel with it. Through the Air vent, Steam and dissolved gases are vent out

17

Operation & Maintenance Manual

to the atmosphere. The Valve shall be throttled to minimize the outßow of Steam. N20 is also one connection provided for air vent without oriÞce. Other Connections Feed water outlet nozzle N3 is provided. Water outlet piping going to the boiler feed water pumps suction header. A drain nozzle (N4) for draining the storage tank. Pegging steam connection (Nozzle N22): A perforated pipe connected to the nozzle is laid along the length of the storage tank below the water level. Admitting steam in a small quantity through pegging line and heating the water to a temperature upto 80 Deg C before admitting the main steam in large quantity will reduce the possible hammering.

Feed water pump’s associated system Suction piping Common suction header for both the pumps is connected from the deaerator outlet piping, providing necessary suction to the pump. Individual pump is provided with isolation valves [LFW-VG-117 / 118 / 119] and a suction Þlter. Filter prevents foreign particle entry into the pump. Pressure gauge installed at the pump inlet to indicate the available suction head while the pump is running. Differential pressure transmitters helps to monitor the condition of strainer. If the dP of suction strainer increases beyond the recommended value, then the feed pumps gets signal for trip Balancing piping

Steam connection N5 is provided for admitting the LP steam for heating the deaerator after initial warm up.

Pump is provided with a balancing line, which is connected to suction line of pump.

Nozzle N16(A to F) are provided for recirculation line from the boiler feed water pumps.

The minimum circulation piping is provided with individual pump. This ensures that during the operation of the pump there will always be a minimum ßow across the pump even when there is no discharge into the boiler.

A Manhole is provided each for storage and vapour tank. A sample cooler is provided in the water outlet of deaerator for the analysis of the water sample. Sample cooler is a coil & shell heat exchanger, sample water is passing through the coil and cooling water through the shell. Needle valves are provided at the inlet and outlet respectively to regulate the sample ßow. Condensate return line is provided at connection N21 Balancing leak off line from feed pumps are provided at connections N19 (A to F) . REFERENCE DRAWINGS P & I Diagram for Deaerator,FWP & dosing - D12 -1WH-59879 Rev 3 P & I Diagram for WHRB - D12 -0WH-09484 Rev 4 Assly of Deaerator - W21-1WH-63955 Rev0 2.1.2Boiler Feed Water Pumps Deaerated water from the deaerator is delivered to the boiler by means of boiler feed pumps. There are three motor driven feed water pumps available. One pump is a standby pump. The Feed water pumps are of Multistage Centrifugal type. The Vendor’s manual is to be referred for more details on operation and maintenance.

Section B

Minimum circulation piping

An auto re-circulation valve is provided on individual pump discharge line for the above purpose Throttle valve – for controlling the ßow through the circulation line. Non-return valve – to prevent the back ßow. Discharge Piping Discharge of each pump is connected to the common discharge header, which supplies feed water to the boiler. A pressure gauge [10-PG 124 / 125 / 126] & transmitter [10-PT136 / 137 / 138] are installed on the discharge header for observing the discharge pressure. Auto re-circulation valve (ARC) installed at the pump discharge maintains the minimum ßow required through the pump, when the ßow to boiler is low. This minimum circulation ßow is taken through a line connected back to the deaerator storage tank with a NRV [LFW-VC-131/134/137] and a globe valve [LFW-VC 130/133/136]. Cooling Water Piping Feed Pump Gland cooling arrangement is provided for stufÞng boxes + lift off devices at DE and NDE side. The cooling water is fed through plant cooling water system. Refer the pump vendor drawing for details.

18

Operation & Maintenance Manual

Note Vendor manual for pumps to be referred for more operation and maintenance details. 2.1.3Feed Control Station WHRB, when it is in service, must be kept continuously supplied with feed water to maintain near normal level in the drum. Feed water is obtained at battery limit (at the inlet of feed water control station) from the feed water pump at a pressure of 70.5 Kg/cm² and a temperature of 120ºC. There is one feed control station, which is in service when the WHRB is operational. • 100% Flow control FCV-137 The 100% ßow control valve FCV-137 is capable of feeding the WHRB when the steam ßow from WHRB is from initial stage. HFW-VL-124 is by pass for 100% FCV. The following are installed in the common inlet line from the Plant feed main to the feed regulation station • Pressure indicator 11-PG-136 to indicate feed water pressure • Tap off for Attemporater spray water with manually operated Isolating valve [DSW-VG-101] • Flow nozzle 11-FE-137 with impulse connections to ßow transmitter 11-FT-137 • A temperature Element 11-TE-138 for indicating temperature of inlet feed water to the DCS indication.

The valve 11-FCV-137 is positioned by the ßow indicating controller 11-FIC-137. 11-FIC-137 is a three element controller, which takes into account not only the drum level, but also the steam ßow from WHRB and the current feed water ßow, to correctly position the feed regulating valve FCV-137. The drum level signal, compensated for drum pressure, is received in controller11-LIC-142. A linearised steam ßow signal, compensated for steam pressure and temperature is also received in 11-FIC-137. The drum level which is a measured variable signal, is computed with the anticipatory signal of steam ßow in 11-FI-137 and a resultant error signal is fed to feed indicating controller 11-FIC-137. 11-FIC-137 compares the level error signal with the feed ßow signal it receives from ßow transmitters 11-FI-157 & 11-FI-137 and computes a control current signal based on its set point (usually normal level). The valve position is transmitted to the DCS. On the DCS, current drum level, steam ßow, feed ßow & the feed control valve position can be monitored. The three element control adopted for the 100% ßow control valves FCV-137 takes into account the drum level, steam ßow and feed water ßow for positioning the control valve as well as it takes only drum level for its operation at low load.

3

Boiler Pressure Part Description

This boiler is a Single-drum, natural circulation, top supported, and membrane wall construction. Various pressure parts are grouped as follows: 1. Economiser

• Pressure indicator 11-PG-139 to indicate feed water pressure at economiser header inlet

2. Steam drum

The ßow transmitters provide feed ßow signal to the feed Indicating controller 11-FIC-137 (which will be described later).

4. Air Vent

2.1.4100% Feed Controller 11-FCV-137 Manually operated valve HFW-VG-121 is the inlet isolating valve. HFW-VG-127 is the outlet isolating valve which normally remains open. Drain valves at upstream and downstream of 11-FCV 137 are used for draining only when the line is isolated for inspection/maintenance of valve 11-FCV 137. Valve 11-FCV-137 is a full load feed regulating valve for maintaining drum water level and is pneumatically operated by a spring opposed diaphragm actuator. The valve opens full on loss of control air and has no manual over ride.

Section B

3. Silencer 5. Evaporator 6. Super heater 7. Attemperator 8. Steam Temperature Control

3.1 Economizer The Economizer located on the last stages of the exhaust gas path of the WHRB. Feed water from the feed regulating station, enters the Bottom header of the ECO ßows up wards. Economizer is provided with air vent and drains. ECO is hung from the top by two guide supports

19

Operation & Maintenance Manual

and anchor support with provision for downward thermal expansion. The drain valves are used for draining the ECO tubes when the WHRB is not in service, if required for maintenance. Feed water, after picking up heat from the Economizer, enters the Drum through t Economizer outlet pipe. Temperature Indication / Recording Instruments 11-TE-138 / 141 are meant for indicating feed water temperatures before and after Economizer respectively. There are pressure gauges 11-PG-139 / 140 at inlet and outlet header of economiser to monitor the feed water pressure.

3.2 Steam Drum The Steam Drum is a long (4000mm approx.) all welded cylindrical vessel made of SA-516 Grade 70 material. The steam drum is supported by the main down comers and the down comers are placed on the WHRB structure over beams. The sliding arrangement permits a limited shift due to thermal expansion. The drum is insulated by lightly resin bonded mineral wool mats. Two manholes, at either end of the drum, provide access to the drum. The drum is closed tight at either end cover plates bolted against the manhole rim by two holding bars. A gasket is Þtted between the cover plate and the mating machined surfaces in the dished ends. The cover plates swing inside, for convenience during opening.

(c)Conditioning of Boiler Water Due to continuous evaporation of boiler water in the drum, minor impurities present in the feed water, concentrate to high impermissible levels in the boiler water. Rise in hardness of water (conductivity), content of chlorides, silica etc., have to be kept to a minimum to prevent scale formation or deposits, in the evaporator tubes and drum. Sample of Boiler water is collected from the continuous blow down line through a sample cooler. If the analysis indicate high conductivity, (chlorides, silica) etc., small pre-determined amount of water is continuously drained from the steam drum through the continuous Blow down valve CBD-104 with a needle valve for controlling the ßow to reduce their concentration to permissible levels in the steam drum. Tri-Sodium phosphate is dosed into steam in the boiler drum to maintain a phosphate concentration and a pH. The Phosphate has the capacity to convert hardness producing insoluble calcium/ magnesium salts to soluble sodium salts, which are drained through the blow down. A typical reaction can be as follows. 3 CaSO4 + 2 Na3 PO4 →Ca3 (PO4)2↓ + 3Na2 SO4. The dozed phosphate also provides desired alkalinity to the boiler water. An alkaline pH minimizes the possibilities of corrosion.

Steam Drum is Þtted with several components to perform important functions, which are listed below:

The following facilities have been provided in the steam Drum for the above operations:

(a) Steam Drum receives feed water from the Economizer outlet through feed pipes and distributes the feed water along the length of the drum by a perforated pipe 80NB to maintain a near constant level (Normal water level) for continuous supply to the evaporator. (to be described further later) through down comer pipes. While ßowing through the evaporator panels, by absorbing heat from the coke oven exhaust gas, the hot water gets converted to water / steam mixture and ßows back to the Drum through riser tubes.

During WHRB startup situations arise resulting in high drum water levels. As high drum water levels are not permissible provision has been made for quickly draining some water from the boiler drum under this condition. The EBD line, drawn from the entire length of the drum consists of a manually operated inlet isolating valve EBD-VG-101, a manual operated parallel slide emergency blow down valve EBD-102, The EBD line drains to the blow down tank. The isolating valves are normally kept closed and are opened only when emergency blow down has to be done. Ensure that the EBD should be close to Blow Down tank so that the operator can easily operate the valve during emergency.

(b) Steam drum receives the water – steam mixture from the evaporator panels through the riser tubes, the water – steam mixture ßows tangentially through the Diemeister pad installed in the steam drum. In this tangential ßow, water, which is heavier, is separated from steam and trickle down to mix with the water in the steam drum. Saturated dry steam collects at the top of the drum and distributed to the Superheater I.

Section B

(d) Emergency Blow Down (EBD)

(e) Level Gauges, Level Indicators, Level Transmitters As maintaining normal water level in the steam drum is one of the important parameters to be

20

Operation & Maintenance Manual

monitored and controlled, elaborate provisions for level instrumentation has been made on the Steam Drum. Brief mention of these instrumentation will be made in this section.

3.2.1 Drum Level Control

(f)Continuous Blow Down Line

Level Transmitters and indicators 11-LI- 142A / 142B.

To enable the water drained from the drum to reßect the true composition of Boiler water, a perforated pipe 25NB is laid along the water space of the drum and connected to the CBD line to the Blow down tank. There is one isolating valve CBD-VG-101,a needle valve CBD-104. The valve for Boiler water continuous Blow down (CBD) is positioned to drain continuously a pre-calculated quantity. (g)Sampling Line The CBD line provided to the sample cooler through two isolating valves CBD-VG-102 & CBD-VL-103. (h)HP (Phosphate) Dozing Line Dosing of phosphate to the Boiler water is to be done in a manner that it quickly mixes with the whole of Boiler water. To enable this, a perforated pipe, 25 NB has been laid along the length of the drum and connected to the HP dosing line through a non-return valve HPC-VC-117 and an isolating valve HPC-VG-118. (i)Level Gauges (11-LG 143 / 144) The Level Gauges is of multi-port type. The top of the gauge glass is connected to the steam side of the drum through two isolating valves. The bottom portion of the gauge glass is connected to the water side of the drum through two isolating valves. Care is taken to ensure that the center line of the center port coincides with the center line of the drum which is the required normal water level. Twin drain valves are Þtted to each gauge. The drains normally remain shut when the gauge is in service with steam side and water side isolating valves open. The level gauges are simple direct reading instruments and serve for quick and accurate reading of the drum level. During the start up of WHRB, level gauges may be the only instruments which can be relied upon as other instruments may not be accurate. The level gauges are also used to verify the readings of other instruments. The level gauges being located at the drum level are not convenient for regular operation of the Boiler. The level gauges however must be maintained in service as IBR requires that atleast one of the level gauges must be in service to operate the WHRB.

Section B

Control of water Level in the steam relies on the following Instruments.

WHRB ID fan trip has been envisaged on Drum level very Low conditions. To avoid a false trip from malfunction of any one instrument, two out of the above three instruments must vote for a trip action. The level transmitters provide drum level signal to the single element and three element controllers. The above level instruments are connected to the steam drum, steam and water space through twin isolating valves. The reading of the steam drum water level by the above instruments are sensitive to the drum pressure. Transmitter 11-PT-145 (through twin isolating valves) mounted on the steam drum, provide a pressure compensation signal to the level transmitters, so that their signals represent true level neutralizing variations due to pressure changes. They also provide steam drum pressure signal to DCS. 11-PG-146 is a local instrument indicating Drum pressure at the drum elevation. 3.2.2 Drum Safety Valve To protect the boiler and personnel against consequences of abnormal pressure increases caused by sudden load decrease, malfunction of Þring system, closure of steam valves etc., two spring loaded safety valves have been Þtted on the drum. On increase of steam pressure beyond a pre- determined set value, the safety valve opens automatically to relieve steam from the drum to the atmosphere. The safety valve closes when the steam pressure falls by around 4% of the set value. IBR prescribes norms for installation, care and testing of the safety valves, which are mandatory. Safety valve, 11-PSV-001 and 11-PSV-002 along with the 11-PSV-003 have the capacity, as per IBR, to relieve steam from the WHRB in such a manner that pressure rise above 103% of the working pressure is prevented on any condition. As the spring loaded safety valves result in high noise levels when they open, the exhaust of the safety valves are connected through a silencer to substantially reduce the noise level. Installation, adjustment and maintenance instructions for safety valves are enclosed which

21

Operation & Maintenance Manual

may be referred for a full understanding of the safety valves.

3.5 Evaporator

3.3 Silencer Mention was made that the exhaust of various safety valves, steam dump & startup valves are exhausted through Silencers. The Silencers are acoustically & mechanically designed to attenuate the large noise made during operation of these valves The silencers are made out of suitable casing in which the sound absorbing materials are packed in a certain pattern & wrapped by scrim cloth and wire mesh to avoid ‘ßy off’ of sound absorbing materials during operation of silencer at high ßow rates The process ßuid enters the annular space between the sound absorbing materials packing where the sound energy is absorbed throughout the length of the silencer. The Silencers are mounted on separate structures on top of the WHRB and the exhaust pipes from the valves are connected to the silencers. As the silencer contain no moving parts, no operational care is needed except opening the drain plug provided in the drain line, once in three months to drain the line.

3.4 Air Vent An air vent on the drum to vent out air during initial boiler Þlling, before start up and during start up. During start up, the air vents are closed at a drum pressure of 2 Kg/cm² (g) and when copious steam is passing. The air vents are opened after shut down of the boiler when the boiler pressure falls to 2 kg/cm2.

EVAPORATOR Figure 1

The Evaporators convert hot boiler water received from the Drum through down comer pipes into a steam water mixture, by absorption of heat from the Coke oven exhaust gas. The steam water mixture is led back to the drum from the evaporators through riser pipes. There are two sections Evaporator 1 & Evaporator II.

of

Evaporators,

The Evaporators are hung from the top headers in the ßue path, on two guide supports and one anchor support with provision for thermal expansion downward & in the sides. Hot water ßow to the evaporators from the drum and steam / water mixture to the drum from the Evaporators through risers. A down comer header of the Evaporator spans all the Evaporator panels. The top headers of the panel are connected to the drum by riser tubes .The circulation through Evaporator panels takes place as follows •

Heated Boiler water from the drum ßows through the two down comer pipes to down comer header.

• From the down comer header, the hot water ßows to the lower headers, and then through Evaporation panel tubes, to the Evaporation panel top headers. During its passage through

Section B

22

Operation & Maintenance Manual

the Evaporation panel tubes, the hot water absorbs heat from the exhaust gas of the coke oven and gets converted to a water/steam mixture. This circulation is assisted by the higher density of water in the down comer compared to the lower density of water / steam mixture in evaporator and riser tubes • The water / steam mixture from the top headers of the Evaporation panel, ßows in the steam drum. • In the steam drum, the steam water mixture ßows through the separators where water & steam are separated and saturated steam ßows to the Superheaters. Seperated water mixes with boiler water to ßow through the Evaporator panels again.

3.6 Super Heater Superheating of saturated steam from drum is done in two stages in Superheater I & in Superheater II. Between Superheater I & II, an attemperator is located to control the temperature of Þnal steam outlet at 485°±5°C. Superheaters are made of modules, each consisting of a top header and a bottom header, with tubes between the headers. Superheater modules are hung from their top headers with provision for thermal expansion down wards & in the sides.

3.7 Super Heater I Saturated steam from the drum ßows to the Þrst super heater top header of Superheater I. From the top header of the SH l, steam ßows through the panel tubes to the bottom header of the same panel, absorbing heat. Then the steam ßows through the super heater II. Super Heater I top header (being the top most point) is provided with Air vents (HPS-VL-106 & HPS-VG 105). The interconnecting pipes of the Superheater and lower headers (Lowest point), are provided with two drains (HPS-VG-107/108). These drains are operated manually. The air vents & drains are opened before light up of the boiler. They are closed at a drum pressure of 2 To 5 Kg/cm².

3.8 Attemperator The function of the attemperator is to control the temperature of HHS steam at Superheater I outlet and Super heater II inlet to 410°C.

Section B

An inter-stage attemperator is provided in the superheater to maintain the Þnal steam temperature. Spraying a controlled quantity of feed water into the superheated steam lowers its temperature as it looses some heat in evaporating the sprayed water. The attemperator is a header, which accommodates an inner sleeve shaped like a venturi. A spray nozzle is Þxed at the entrance to the restricted venturi section. The sleeve is held in position Þrmly by the locating pins welded to the header at the steam entry side. The sleeve is free to expand at the steam exit side. Water is sprayed through the spray nozzle. The steam passes through the venturi picks up the spray, which completes the evaporation and thoroughly mixes the steam. The connection of the inlet to the spray nozzle embodies a thermal sleeve construction to protect the steam line from temperature differential between the spray water and the steam. A drain connection is provided at the exit of the attemperator.

3.9 Super Heater II Superheater II receives the steam from bottom header of Superheater I. From the top header of the SH II, steam ßows through the panel tubes to the bottom header of the same panel, absorbing heat. Then the steam ßows into main steam line. Super Heater II top header (being the top most point) is provided with Air vents (HPS-VL-110 & HPS-VG 109). The interconnecting pipes of the Superheater and lower headers (Lowest point), are provided with two drains (MSS-VG-101/102). These drains are operated manually. The air vents & drains are opened before light up of the boiler. They are closed at a drum pressure of 2 To 5 Kg/cm².

3.10 Steam Temperature Control Loop Attemperator spray control is designed to maintain the steam temperature at 485 deg C. As the heat pickup in the superheater increases with load, the spray water requirement increases with load. The spray water line for the Attemperator, spray water is obtained from the Boiler Feed water main, before the ßow transmitter 11-FE 137. The spray water line consists of the following. An manually operated isolation valve DSW-VG-101. The isolation valve needs to be opened when attemperator is to be taken into service.

23

Operation & Maintenance Manual

Drain valves DSW-VG-112/113, these drain valves are opened to drain the line for maintenance. Pneumatically operated ßow control valve 11-TCV-153. The ßow control valve is provided with inlet/outlet Isolating valves DSW-VG-102/108. The inlet/out Isolating valves remain normally open. The drain valves DSW-VG-103/104/106/107 which remain normally closed. These drain valves are opened after closing inlet/outlet Isolating valves, when control valve is to be taken for maintenance. The spray water line connects to the spray nozzle of the attemperator through a non return valve DSW-VC-111. Pressure gauge 11-PI-159, indicates pressure of the spray water ßowing to the nozzle.

valves are kept opened during start up upto 5 kg/cm2 pressure. • FLOW NOZZLE Flow nozzle 11-FE-157 is installed on the steam line to provide impulse to upstream & down stream pressure readings to steam ßow transmitter 11-FT-157. The ßow transmitter reading, after steam pressure & temperature compensation is used for the following, – Steam ßow reading. (11-FI 157) – Steam ßow compensation for feed ßow, steam temperature controllers • SH STEAM TEMPERATURE INPUT Temperature transmitter 11-TE 153 provide the steam temperature input for the following

Temperature Indicators 11-TE-151 & 11-TE 152 provides steam temperature indication before and after the attemperator to judge the effectiveness of attemperation.

– Temperature Indicating controller 11-TIC-153 which provides steam temperature High & low alarms and also controls positioning of the attemperator spray control valve as described earlier.

4

– Temperature compensation signal to the feed ßow, steam ßow instruments.

Main Steam Piping

The SH steam line connecting the top header of Superheater II to the plant steam main.

5

This line incorporates the following.

This section explains the major operational control points described in this chapter.

• ELECTRICALLY OPERATED SH STEAM STOP VALVE 11-MV 302 This valve Isolates the WHRB from the plant / Common steam header. This valve is provided with an electrically operated, integral by pass valve 11-MV 303. • SAFETY VALVE 11-PSV-003 This is a spring loaded, valve set at 71 Kg/cm², pressure to protect the boiler against over pressures. The safety valve is similar to Drum safety valves described earlier. The exhaust of the safety valve is piped to a silencer to reduce the noise levels when the safety valve is operating. The silencer is mounted on a separate structure on top of the WHRB. • START UP VENT VALVE 11-PCV 154 is an pneumatically operated regulating start up vent valve. 11-MV 301 is an electrically operated Isolating valve preceding 11-PCV 154. The outlet of the start up vent valve is exhausted to atmosphere through a silencer. The start up vent valve is to be kept open while start up. If provides initial steam ßow for the superheaters. • STEAM LINE DRAIN The steam line drain consists of the following valves manually operated MSS-VG-101/102/108/109. These

Section B

Operational Control

Steam Drum • Maintain Feed water, Boiler water quality, and phosphate concentration. • Maintain water level in the drum within permissible low and high levels. The protection system envisages boiler trip at very high and very low levels, which should not be by passed. • Maintain drum level gauge glasses LI 3401 & PI 34102 in good working condition. Operators may verify the readings of level transmitters with the readings of the drum level gauge glasses once a day. • Drain superheaters thoroughly during startup. • THERMAL STRESSES IN DRUM DURING START UP AND SHUT DOWN Steam Drum is a large cylindrical shell. Before light up of a boiler, the inner and outer surfaces of the drum are at the same temperature. When boiler is lighted up, the inner surface gets heated up Þrst by the water (and then by steam) and transmits heat to the outer surface of drum. The heat transfer is by conduction and is a bit slow. For short time after light up, there can be

24

Operation & Maintenance Manual

differences of temperature between steam and water surfaces of the drum. Such a difference can set up thermal stresses, which are not desirable, and an alarm sounds at DCS. To minimize the thermal stresses, the operator must restrict the Þring rate when starting the WHRB by modulating the diverter damper. Boiler water temperature rise rate must not be above 56 0C per hour till operating pressure is reached. • SWELLING During WHRB startup, as the Boiler water temperature reaches 90°C, there is an increase of water level caused by increase in the volume of hot water. Such swelling, if not controlled, can cause a High Level trip. To avoid this, initial Þlling is normally restricted to low level (say – 100 to 150 mm) and the smart Operator anticipates a swell and uses the IBD to drain and control the level.

• Manually operated valves must be closed hand tight only. Use of levers on hand wheels is not desired.

5.1 Steam and Water System Technical Performance Data WHRB HEATING SURFACES ECO Modules (Pass 2)

- 827.33 m²

Evaporator I & II

- 662.6 m²

Superheater I & II

- 200.45 m²

WHRB Design Pressure : Maximum working pressure - 75.0 kg / cm2 (g) Set pressure and capacity of safety valves

• Do not operate the WHRB with safety valves gagged. Passing safety valves must be attended during the next planned shut down. Super Heaters & Attemporator • Super heaters must be drained after shut down and cooling of the boiler. They must also be kept open before a cold start up till 2 - 3 kg/cm2 pressure is built up. During hot light ups they are opened for a few minutes.

General • Boiler water can be drained after a shut down only after depressurizing to 2 kg/sq. cm and after cooling to 80 °C • Draining of Boiler water must preferably done through the blow down tank. • If a tube failure is detected, it is advisable to plan for an early shut down. It may be possible to quickly repair the failed tube and return to service. If the shut down is in-ordinately delayed, there are possibilities of larger secondary damages, which may prolong the shut down, required for repairs.

Section B

Set Pressure kg / sq. cm (g)

Capacity (Kg/Hr)

11-PSV-001 (Drum)

74.5

7500

11-PSV-002 (Drum)

75

7500

11-PSV-003 (MS Line)

71

5000

Drum Level Gauge

High Level Alarm

Drum Axis (‘0’ mm) – 50 % 65%

Low Level Alarm

35%

Low Level Trip

25%

Normal Water Level

• Soot blowing of Super Heaters may be done once a shift to keep their surfaces clean, it liquid fuels are burnt. • Super heat steam temperatures at exit of Super Heater- 1, Super Heater 2 main steam temperatures must be monitored to see there is no excessive heat pick up. Compare these Þgures with predicted performance values. High steam temperatures may mean high metal temperatures.

Tag No

6

Boiler Blowdown System

AIM This chapter describes the WHRB blow down system for safe draining of high pressure / High temperature steam and water from the boiler using the blow down tank. System Description The P & ID of the steam and water system shows the various drains from the WHRB, SH steam line and the soot blower system. Large quantities of steam or high pressure / temperature water are not to be drained through open canals for the following reasons: a) Such draining will cause splashing of high volumes of steam, which can be a nuisance by

25

Operation & Maintenance Manual

the noise it creates, and also it affects the visibility around the draining area.

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

b) High temperatures of these drains can cause scalding injuries to workmen who may come in contact with it.

HIGH PRESSURE / HIGH TEMPERATURE STEAM AND WATER DRAINS

c) The force and temperature of these drains will erode the linings of the drain canals. Sr. No.

Source

Valve Nos

Temp of drain °C

Frequency of usage

1.

Continuous blow down

CBD-104

291°C

Continuous, quantity depending on quality of baler water

2.

Emergency blow down

EBD-102

Upto 291°C

Occasional during high levels in drum, during start up

The drains indicated above table are connected to the blow down tank. The blow down tank is capable of separating steam from the drain water. The drains are connected tangentially in the upper half of the drum, to direct the drain ßuid circumferentially around the inner wall of the tank, to aid separation of steam and water by their differences in densities. A vent line of the tank is connected to Deaerator. Level of water is maintained by a control valve 11-FCV-137 through level controller 11-LIC-142

6.1 Other Drains The drains indicated above table are connected to the blow down tank. The blow down tank is capable of separating steam from the drain water. The drains are connected tangentially in the upper half of the drum, to direct the drain ßuid circumferentially around the inner wall of the tank, to aid separation of steam and water by their differences in densities. A vent line of the tank is provided open to atmosphere. It can be seen that drains have been provided in the feed water line and the attemperator spray water lines connected to the drain canal. As these drains are either for operation to drain these lines after an isolation or for short time during charging, their connections to the open canal is not expected to pose a problem. • 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

Section B

6.2 Continuous Blow Down Control CBD control involves the following operations • Obtaining a sample of boiler water from the steam drum. • Analyzing the sample for conductivity, hardness, NaCL, Silica, Fe, etc., and working out a rate of draining of boiler water to maintain the concentrations as suggested in Boiler water. • Manually positioning the CBD valve is to be decided depending on the sample analysis • Repeating the sampling, analysis and repositioning the CBD valve after certain interval is necessary to maintain the required Boiler water quality. This system of manual control requires the services of a sampler, a chemist and a laboratory round the clock. The arrangements provided for CBD control is: • A perforated pipe, laid along the water space in the steam drum connects through a stub to the continuous blow down line. • CBD line from drum connects to the blow down tank. • A tap off from the CBD line is taken to the sample cooler for continuous analysis of boiler water conductivity and also for a grab sample Sampling of CBD / Boiler water is done in one of the sample coolers of the sampling package. This package provides analysis of the following samples to provide a comprehensive information of quality of steam and water of WHRB. • Samples of saturated steam from Top saturated steam header of WHRB.

26

Operation & Maintenance Manual

• Samples of main steam from Steam header of WHRB. • Samples of boiler water (CBD) from the steam drum of WHRB. • Samples of feed water. While all the samples above are analyzed for conductivity by separate analyzers, the CBD sample and the feed water samples are analyzed in addition for pH also. A brief description of the salient features of the sample cooler of the CBD analyser is given. Care of other sample coolers is identical. CBD-104 is normally kept open to maintain small continuous ßow of boiler water to the blow down tank. This is required to ensure the sample at any time to the sample cooler is truly representative of the sample being analysed. This continuous ßow also ensures that these lines do not get chocked for want of adequate ßow. Valves CBD-VG-102 & CBD-VL-103 are isolating valves to the sample cooler which remains open. The sample cooler is a tube and shell type heat exchanger with the boiler water ßowing through tubes and the cooling water in the outer shell, with the speciÞc purpose of sampling. Cooling water is provided from the plant fresh water (DM water circuit) in a closed loop. Tri-sodium phosphate dosing to Boiler water to maintain its phosphate content at 2 to 6 PPM. The tri-sodium phosphate at the suggested levels, maintains the alkalinity of the boiler water (pH 9.5 to 10.2) and also converts the harmful, insoluble calcium and magnesium salts which forms the residual hardness of boiler water, to benign soluble, sodium salts, in the form of a soft sludge, to be drained by the CBD. Phosphate dosing, prevents corrosion of the water washed parts of the steam drum and the evaporator tubes, by adjusting the speed or the stroke of the pump provided as described below. Excess as well as reduced phosphate levels in Boiler water should be avoided. (The phosphate dosing is also some times called as "HP dosing" as the pump used develops high pressure to dose against the boiler drum pressure).

• Two dosing pumps (with one stand by) • DM Water source for preparation of the phosphate solution as well as for ßushing

7.2 Mixing Tank The Mixing tank is a stainless steel covered cylindrical vessel of 150 litres capacity; with a level indicating gauge glass (11-LI-701), DM water inlet line (with a manual isolating valve) HPC-VL-101, an over ßow drain line, a tank drain line with a manual isolating valve HPC-VB-121, a basket for placing required quantity of tri-sodium phosphate powder for preparation of the solution. A solution inlet connection to the pumps with a manual isolating valves HPC-VB-105/106. A motor operated stirrer is also Þtted for preparation of chemical solutions. The level of the mixing tank is monitored by level switch (11-LSL-701). Availability of a minimum level is a required permissive condition for starting or continued service of a dosing pump.

7.3 Preparation of 5% Phosphate Solution in the tank • Tank drain valve HPC-VB-121 is closed. • Gauge glass inlet cocks are opened and its drain is closed. • The lid of the tank is opened, and a calculated quantity of phosphate to prepare 150 litres of solution is placed in the basket and lid closed. • The water inlet valve HPC-VL-101 is opened to admit water (from the DM water line). The level gauge is watched and when the level in the tank is nearly full, the water inlet valve is closed. • The stirrer is placed in service for 30 minutes by operating its switch in the local panel. Availability of a minimum level is a precondition for starting and running of the stirrer.

7.4 Phosphate Dosing Pump

The equipment, which are of stainless steel, provided for phosphate dosing (“HP dosing”), are shown in P & I diagram and consists of

Two phosphate dosing pumps are provided, out of which one is in service at a time, and the other is a standby. The pumps are plunger operated reciprocating, positive displacement type. The stroke of the plunger can be altered. The motor is provided with a variable frequency drive through a gear box for continuous speed control. The vendor manual of the pump and gearbox is to be provided for full information on construction and parts detail.

• A mixing tank for preparation of 5% tri-sodium solution.

Each pump is connected to a common discharge line with the following valve arrangement:

7

Chemical Dosing & Sampling System

7.1 HP Dosing System

Section B

27

Operation & Maintenance Manual

• An inlet valve with a "Y" strainer at the pump inlet. Y strainer traps dirt or other solid particles in its basket. The Y strainer is to be cleaned once a month, after stopping the pump and closing its inlet and outlet isolating valves. • On the discharge side of the pump, a pressure gauge and an outlet isolating valve is Þtted before the common discharge line. A safety relief valve has also been Þtted on the discharge line to relieve any over pressures in case of closure of valves on the discharge line. The outlet of the relief valve is returned to the mixing tank. The relief valve must be tested for its operation at the set pressure atleast once a year. The pump must not be operated with the relief valve continuously operating. (cause of relief valve operation must be found and rectiÞed). • The common discharge line is connected to the HP dosing line of the steam drum through an NRV and an isolating valve1. The isolating valve is veriÞed open before boiler light up and normally remains open all the time. Phosphate dosing is through a perforated pipe along the full length of the water space in the drum. Availability of a minimum level in the mixing tank is a pre condition for starting or running of the dosing pumps. Out of the two pumps, one pump is selected for service and the other is in reserve (DCS macro, Local panel). The pumps are interlocked such that when a working pump trips, the reserve pump starts automatically. A phosphate pump is placed immediately in service after the WHRB start up in the following manner: • Boiler water sample is analyzed and phosphate content is determined. • The pump is prepared by opening the outlet valve from the mixing tank, opening the inlet and the two outlet valves of the pump. Two minutes are allowed after opening the inlet valve for the pump to get Þlled with phosphate solution. The pump is started by switching on

Section B

the motor. The pressure gauge is observed. It should show a reading, higher than the steam drum pressure. An accumulator on the pump discharge line dampens the pulsations which otherwise would be there as this is a positive displacement reciprocating pump. • Any abnormal noise from the pump, motor or gearbox is noted. The safety relief valve should not also be operating. If there are no abnormalities the pump is allowed to run. • Every four hours, the phosphate content in the boiler water is checked by laboratory sample analysis and also by the pH meter. The pump speed stroke is increased or decreased to maintain the phosphate content within 8 to 10 PPMS by continuous pump operation. • The phosphate solution level is observed in the mixing tank by the gauge glass. If the level falls to 25% of the gauge glass level, additional solution is prepared as stated above. FLUSHING THE PHOSPHATE PUMP AND THE LINES WITH WATER DURING LONG STOPPAGE OF THE WHRB: If the WHRB is to be stopped for more than a few days for servicing or maintenance, the phosphate pumps and the line are ßushed with water to keep them clean in the following manner. A (ßushing) line is connected from the tank solution preparation DM waterline to the inlet line of the pumps . The pump which was in service earlier is run, for about 30 minutes to one hour. DM Water ßushes the phosphate solution from the pump and the lines to the steam drum and cleans them. The pump is stopped. The outlet valve from the mixing tank, is not opened till the boiler is again lighted and a phosphate pump is required in service. At that time the isolating valve on the DM line is closed. NOTE:Do not operated the Stirrer of the dosing pump when the HP tank is dry or Þlled with water or the dosing solution. The operation of the stirrer can lead to failure of stirrer (misalignment of the stirrer).

HP not dry the

28

Operation & Maintenance Manual

7.5 Water And Steam Quality Control And Monitoring AIM This chapter describes the standards for the boiler feed water and boiler water for corrosion and scale

free operation of the WHRB and for obtaining pure steam. Methods of control of boiler water are also explained. Suggested quality of boiler feed water (and attemperator water) fed to the WHRB is given in following table:

PARAMETER

Max. permissible value

pH at 25°C

8.5-9.5

Total hardness as CACO3

Nil

Chlorides as NACL

Not traceable

Silica as SIO2