O M Manual
O M Manual
O M Manual
.
OPERATION & MAINTENANCE
MANUAL
FOR 2 X 20TPH
SUPPLIED TO
GUMMIDIPOONDI, TAMILNADU
THERMAX LIMITED
BOILER & HEATER GROUP
PUNE, INDIA
PSK & 23.07.2010 AA 23.07.2010 USU 23.07.2010 0
SD
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
i
Operation & Maintenance Manual
ii
Operation & Maintenance Manual
iii
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
iv
Operation & Maintenance Manual
v
Operation & Maintenance Manual
vi
Operation & Maintenance Manual
Section A
PARAMETERS VALUE
Section A 2
Operation & Maintenance Manual
PARAMETERS VALUE
3 Technical Specification
3.1 Flue gas Velocity profile: (for design case)
Sr
Component Velocity, m/s
No.
1 Radiation cavity 8
2 Superheater 12 to 15
3 Evaporator 10 to 11
4 Economiser 8 to 9
Sr
Component Deg C
No.
1 Radiation chamber inlet / outlet 950 / 878
Pre Evaporator cum Support Tube
2 878 / 849
(Pass 1) inlet / outlet
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
Sr Component Deg C
1 Radiation chamber inlet / outlet 285 / 285
Pre Evaporator cum Support Tube
2 285 / 285
(Pass 1) inlet / outlet
3 Superheater II (Pass 1) inlet / outlet 328 / 485
Section A 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
4.2 Superheater- II
Sr
Description Value
No.
1 Design code IBR 1950 with its latest amendments
2 Design pressure 75 kg/cm² g
Section A 4
Operation & Maintenance Manual
Sr
Description Value
No.
3 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
Sr
Description Value
No.
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
Sr
Description Value
No.
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
7 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
4.5 Economiser
Section A 6
Operation & Maintenance Manual
4.6 Attemperator
Sr No. 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
4.7 Insulation
Sr No. Description Value
1 Type Mineral wool mattress
100 Kg/M3 up to 400 Deg C
2 Density
120 Kg/M3 above 400 Deg C
3 Cladding Aluminum sheet of 24 SWG
4 Skin Temperature 30 Deg C above ambient temp.
5 Utilities
5.1 Electrical power
Parameters Units Value
For LT motors (UPTO AND INCLUDING 200 KW)
Voltage V 415 +/- 10%
Section A 7
Operation & Maintenance Manual
5.3 DM Water
Parameters Unit Value
Supply Pressure KSC (g) 5 @ Battery Limit
Supply Temperature Deg C Ambient @ Battery Limit
Flow Kg/Hr 1200 (Normal) , 15000 (Maximum)
Section A 8
Operation & Maintenance Manual
6 ID Fans
Sr
Description Value
No.
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.
By variable frequency control & Pneumatic
11 Type of ßow control
operated multi louver damper.
12 Type of isolation Not required
13 Type of Lubrication Grease (Servo Gem; EP2)
7 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
ASME SECT. VIII DIV Edition 2004, ADDENDA
Design & Construction code
2006 (WITH ‘U’ STAMPING)
Section A 9
Operation & Maintenance Manual
10 Soot Blower
Long Retractable soot
Sr No. Description Rotary soot blower
blower
Section A 10
Operation & Maintenance Manual
11 Gauge Glass
Drum level Gauge
Description Details
12 Safety Valve
DESCRIPTION
UNIT DRUM #1 DRUM #2 SH
APPLICATION
SIZE ORIFICE -
Section A 11
Operation & Maintenance Manual
DESCRIPTION
UNIT DRUM #1 DRUM #2 SH
APPLICATION
RELIEVING
TPH 8000 8000 6000
CAPACITY
QUANTITY - 1 1 1
FLUID - Sat Steam Sat Steam Sup Steam
DESCRIPTION /
UNIT Details
APPLICATION
14 EMR Valve
DESCRIPTION /
UNIT Details
APPLICATION
Section A 12
Operation & Maintenance Manual
15 Gauge Glass
Section A 13
Operation & Maintenance Manual
Section B 14
Operation & Maintenance Manual
Control philosophy of these loops is described in rest of boiler’s instrument and valves shall be as
the document submitted separately. per the following nomenclature.
Referance Drawings: Refer the P & I diagram for the tagging procedure.
• D12-0WH-09484 - P & ID for Waste Heat Instrument Tagging Procedure.
recovery Boiler – Refer latest revision. Tag numbers of Instruments, motorized valves,
pneumatic control valves, safety valves, manual
This O & M manual shall be for applicable for both
valves, & drives to be preÞxed with 10 for
the 02 boilers. The description in the manual of
common items. 11 & 12 for WHRB 1 & 2
the instrument and valve tag no. is dealt with
respectively
typically one boiler. However the tag no. for the
Section B 15
Operation & Maintenance Manual
Section B 16
Operation & Maintenance Manual
level. Two steam distribution headers connected Apart from this remote level indication direct level
to the supply pipe are lied at the bottom and along gauge glass [10-LG 103 & 104] are provided to
the length of the storage tank. These headers are cover the height between very low level and upto
perforated pipes to distribute the steam along the over ßow level. These level gauge are mounted
entire length of the storage tank water space. on a water column connected to the Nozzles N10
A/B
Steam rises from the bottom of Storage
Tank, heating the water and rises through Over Flow Shut Off Valve
the interconnection pipe into the Vapor Tank.
Perforated Trays inside the Vapor tank increase [10-XV 109] shut off valve is provided to drain
the residence time of water and Heating Steam. the excess water from deaerator if level increases
Oxygen, Carbon dioxide and other dissolved beyond recommended value. Connection N6 is
gases are vented out along with Vent Steam assigned for that.
through the nozzle N13. Pressure Control
The dissolved Oxygen level in the feed water The deaerator operating pressure of 1.76
by mechanical deaeration can be brought to kg/cm2(g) is maintained by the pressure control
0.02 to 0.03 ppm. If required the residual loop, which contains the pressure control valves
dissolved Oxygen can be further scavenged [10-PCV 105] in the steam line, a pressure
by the reaction with chemicals such as sodium transmitter [10-PT 105] mounted on the storage
sulphite (catalyzed or un-catalyzed) or Hydrazine. tank nozzle N12 and an electronic pressure
By chemical scavenging the dissolved Oxygen indicating controller [10-PIC 105] in the control
level can be brought down to as low as 0.007 room. Set point for the pressure controller shall
ppm. Chemical may be dosed in the storage be kept at 1.76 kg/cm2 (g).
section of the deaerator through a header. Nozzle
N4 is provided for this and can be utilised. The Pressure Relief Valve (10-PSV 005)
dosing of the particular chemicals is done in A Nozzle N17 is provided at the top of vapour
predetermined quantity and concentration. A tank to mount a relief valve. Relief valve would
sample cooler provided in the feed water outlet relieve the steam at the design set pressure of 3
piping is used to collect the sample for analysis bar(g), when there is excessive pressure build-up
of water. inside the vessels (system) incase of sudden
Storage tank is supported by saddle supports. reduction of water out ßow/ intake to deaerator or
One of the saddles is Þxed and the other is sliding malfunctioning of pressure control loop.
one to take care of thermal expansion. PTFE Temperature Gauge
sheets are provided under the sliding saddle for
free movement of saddle. Platforms and ladders A temperature gauge [10-TE 107] is Þxed on to the
are provided for tanks and condenser for O & M storage tank nozzle (N14).
feasibility.
Vacuum Breaker
THE ACCESSORIES AND THE MOUNTINGS
A Vacuum Breaker assembly consists of Non
Deaerator Level Control Return Valves directed towards vapor Tank from
atmosphere mounted on the Nozzle N18. This is
The desired normal water level (NWL), which is to prevent Deaerator from operating at vacuum or
maintained through a level control valve [10-LCV negative Pressure. Vacuum condition inside the
102] of DM water line & condensate return line. Deaerator would mean that the Deaerator is not
Level in the storage tank is monitored remotely being supplied with enough Steam with respect to
by the level transmitter [10-LT 102 A & B ]. Two the water ßow leading to condensation of heating
nozzles (N11 A/B) at this elevation are provided Steam. In case the Deaerator happens to go
for LT connection at distance of 301 mm above under vacuum, atmospheric air will rush through
and 1392 mm below the NWL. these Non Return Valves breaking the vacuum.
A Feed back control loop with the electronic
Air vent
controller [10-LIC 102] is provided for automatic
level control. Process variable signal for the level Air vent is provided (nozzle N2) on topside of the
controller is transmitted by the [10-LT 102 A & B vapour tank. Air vent is provided with an oriÞce
]. Set point of the level controller is to be kept at and a globe Valve in parallel with it. Through the
’0’ mmWC, which corresponds, to NWL. Air vent, Steam and dissolved gases are vent out
Section B 17
Operation & Maintenance Manual
to the atmosphere. The Valve shall be throttled to Feed water pump’s associated system
minimize the outßow of Steam. N20 is also one
Suction piping
connection provided for air vent without oriÞce.
Common suction header for both the pumps
Other Connections
is connected from the deaerator outlet piping,
Feed water outlet nozzle N3 is provided. Water providing necessary suction to the pump.
outlet piping going to the boiler feed water pumps
Individual pump is provided with isolation valves
suction header.
[LFW-VG-117 / 118 / 119] and a suction Þlter.
A drain nozzle (N4) for draining the storage tank. Filter prevents foreign particle entry into the pump.
Pressure gauge installed at the pump inlet to
Pegging steam connection (Nozzle N22): A indicate the available suction head while the pump
perforated pipe connected to the nozzle is laid is running. Differential pressure transmitters
along the length of the storage tank below the helps to monitor the condition of strainer. If
water level. Admitting steam in a small quantity the dP of suction strainer increases beyond the
through pegging line and heating the water to recommended value, then the feed pumps gets
a temperature upto 80 Deg C before admitting signal for trip
the main steam in large quantity will reduce the
possible hammering. Balancing piping
Steam connection N5 is provided for admitting the Pump is provided with a balancing line, which is
LP steam for heating the deaerator after initial connected to suction line of pump.
warm up. Minimum circulation piping
Nozzle N16(A to F) are provided for recirculation The minimum circulation piping is provided with
line from the boiler feed water pumps. individual pump. This ensures that during the
A Manhole is provided each for storage and operation of the pump there will always be a
vapour tank. minimum ßow across the pump even when there
is no discharge into the boiler.
A sample cooler is provided in the water outlet of
deaerator for the analysis of the water sample. An auto re-circulation valve is provided on
Sample cooler is a coil & shell heat exchanger, individual pump discharge line for the above
sample water is passing through the coil and purpose
cooling water through the shell. Needle valves Throttle valve – for controlling the ßow through the
are provided at the inlet and outlet respectively to circulation line.
regulate the sample ßow.
Non-return valve – to prevent the back ßow.
Condensate return line is provided at connection
N21 Discharge Piping
Discharge of each pump is connected to the
Balancing leak off line from feed pumps are
common discharge header, which supplies feed
provided at connections N19 (A to F) .
water to the boiler. A pressure gauge [10-PG
REFERENCE DRAWINGS 124 / 125 / 126] & transmitter [10-PT136 / 137
/ 138] are installed on the discharge header for
P & I Diagram for Deaerator,FWP & dosing - D12
observing the discharge pressure.
-1WH-59879 Rev 3
Auto re-circulation valve (ARC) installed at the
P & I Diagram for WHRB - D12 -0WH-09484 Rev pump discharge maintains the minimum ßow
4 required through the pump, when the ßow to boiler
Assly of Deaerator - W21-1WH-63955 Rev0 is low. This minimum circulation ßow is taken
through a line connected back to the deaerator
2.1.2Boiler Feed Water Pumps storage tank with a NRV [LFW-VC-131/134/137]
and a globe valve [LFW-VC 130/133/136].
Deaerated water from the deaerator is delivered
Cooling Water Piping
to the boiler by means of boiler feed pumps.
There are three motor driven feed water pumps Feed Pump Gland cooling arrangement is
available. One pump is a standby pump. The provided for stufÞng boxes + lift off devices at DE
Feed water pumps are of Multistage Centrifugal and NDE side. The cooling water is fed through
type. The Vendor’s manual is to be referred for plant cooling water system. Refer the pump
more details on operation and maintenance. vendor drawing for details.
Section B 18
Operation & Maintenance Manual
Section B 19
Operation & Maintenance Manual
and anchor support with provision for downward (c)Conditioning of Boiler Water
thermal expansion.
Due to continuous evaporation of boiler water in
The drain valves are used for draining the ECO the drum, minor impurities present in the feed
tubes when the WHRB is not in service, if required water, concentrate to high impermissible levels
for maintenance. in the boiler water. Rise in hardness of water
(conductivity), content of chlorides, silica etc.,
Feed water, after picking up heat from the
have to be kept to a minimum to prevent scale
Economizer, enters the Drum through t
formation or deposits, in the evaporator tubes and
Economizer outlet pipe. Temperature Indication
drum.
/ Recording Instruments 11-TE-138 / 141 are
meant for indicating feed water temperatures Sample of Boiler water is collected from the
before and after Economizer respectively. There continuous blow down line through a sample
are pressure gauges 11-PG-139 / 140 at inlet and cooler. If the analysis indicate high conductivity,
outlet header of economiser to monitor the feed (chlorides, silica) etc., small pre-determined
water pressure. amount of water is continuously drained from
the steam drum through the continuous Blow
3.2 Steam Drum down valve CBD-104 with a needle valve for
controlling the ßow to reduce their concentration
The Steam Drum is a long (4000mm approx.) all to permissible levels in the steam drum.
welded cylindrical vessel made of SA-516 Grade
Tri-Sodium phosphate is dosed into steam in the
70 material. The steam drum is supported by
boiler drum to maintain a phosphate concentration
the main down comers and the down comers
and a pH. The Phosphate has the capacity to
are placed on the WHRB structure over beams.
convert hardness producing insoluble calcium/
The sliding arrangement permits a limited shift
magnesium salts to soluble sodium salts, which
due to thermal expansion. The drum is insulated
are drained through the blow down. A typical
by lightly resin bonded mineral wool mats. Two
reaction can be as follows.
manholes, at either end of the drum, provide
access to the drum. The drum is closed tight 3 CaSO4 + 2 Na3 PO4 →Ca3 (PO4)2↓ + 3Na2
at either end cover plates bolted against the SO4.
manhole rim by two holding bars. A gasket is Þtted
between the cover plate and the mating machined The dozed phosphate also provides desired
surfaces in the dished ends. The cover plates alkalinity to the boiler water. An alkaline pH
swing inside, for convenience during opening. minimizes the possibilities of corrosion.
Steam Drum is Þtted with several components The following facilities have been provided in the
to perform important functions, which are listed steam Drum for the above operations:
below: (d) Emergency Blow Down (EBD)
(a) Steam Drum receives feed water from During WHRB startup situations arise resulting
the Economizer outlet through feed pipes and in high drum water levels. As high drum water
distributes the feed water along the length of the levels are not permissible provision has been
drum by a perforated pipe 80NB to maintain a near made for quickly draining some water from the
constant level (Normal water level) for continuous boiler drum under this condition. The EBD line,
supply to the evaporator. (to be described further drawn from the entire length of the drum consists
later) through down comer pipes. While ßowing of a manually operated inlet isolating valve
through the evaporator panels, by absorbing heat EBD-VG-101, a manual operated parallel slide
from the coke oven exhaust gas, the hot water emergency blow down valve EBD-102, The EBD
gets converted to water / steam mixture and ßows line drains to the blow down tank. The isolating
back to the Drum through riser tubes. valves are normally kept closed and are opened
(b) Steam drum receives the water – steam only when emergency blow down has to be done.
mixture from the evaporator panels through the Ensure that the EBD should be close to Blow
riser tubes, the water – steam mixture ßows Down tank so that the operator can easily operate
tangentially through the Diemeister pad installed the valve during emergency.
in the steam drum. In this tangential ßow, water,
(e) Level Gauges, Level Indicators, Level
which is heavier, is separated from steam and
Transmitters
trickle down to mix with the water in the steam
drum. Saturated dry steam collects at the top of As maintaining normal water level in the steam
the drum and distributed to the Superheater I. drum is one of the important parameters to be
Section B 20
Operation & Maintenance Manual
(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 WHRB ID fan trip has been envisaged on Drum
perforated pipe 25NB is laid along the water space level very Low conditions. To avoid a false trip
of the drum and connected to the CBD line to from malfunction of any one instrument, two out
the Blow down tank. There is one isolating valve of the above three instruments must vote for a trip
CBD-VG-101,a needle valve CBD-104. The valve action.
for Boiler water continuous Blow down (CBD) is The level transmitters provide drum level signal to
positioned to drain continuously a pre-calculated the single element and three element controllers.
quantity.
The above level instruments are connected to the
(g)Sampling Line steam drum, steam and water space through twin
The CBD line provided to the sample cooler isolating valves. The reading of the steam drum
through two isolating valves CBD-VG-102 & water level by the above instruments are sensitive
CBD-VL-103. to the drum pressure.
Transmitter 11-PT-145 (through twin isolating
(h)HP (Phosphate) Dozing Line
valves) mounted on the steam drum, provide
Dosing of phosphate to the Boiler water is to be a pressure compensation signal to the level
done in a manner that it quickly mixes with the transmitters, so that their signals represent true
whole of Boiler water. To enable this, a perforated level neutralizing variations due to pressure
pipe, 25 NB has been laid along the length of the changes. They also provide steam drum pressure
drum and connected to the HP dosing line through signal to DCS.
a non-return valve HPC-VC-117 and an isolating
11-PG-146 is a local instrument indicating Drum
valve HPC-VG-118.
pressure at the drum elevation.
(i)Level Gauges (11-LG 143 / 144)
3.2.2 Drum Safety Valve
The Level Gauges is of multi-port type. The top of
the gauge glass is connected to the steam side To protect the boiler and personnel against
of the drum through two isolating valves. The consequences of abnormal pressure increases
bottom portion of the gauge glass is connected to caused by sudden load decrease, malfunction
the water side of the drum through two isolating of Þring system, closure of steam valves etc.,
valves. Care is taken to ensure that the center line two spring loaded safety valves have been Þtted
of the center port coincides with the center line of on the drum. On increase of steam pressure
the drum which is the required normal water level. beyond a pre- determined set value, the safety
Twin drain valves are Þtted to each gauge. The valve opens automatically to relieve steam from
drains normally remain shut when the gauge is in the drum to the atmosphere. The safety valve
service with steam side and water side isolating closes when the steam pressure falls by around
valves open. 4% of the set value. IBR prescribes norms for
installation, care and testing of the safety valves,
The level gauges are simple direct reading
which are mandatory. Safety valve, 11-PSV-001
instruments and serve for quick and accurate
and 11-PSV-002 along with the 11-PSV-003 have
reading of the drum level. During the start up of
the capacity, as per IBR, to relieve steam from
WHRB, level gauges may be the only instruments
the WHRB in such a manner that pressure rise
which can be relied upon as other instruments
above 103% of the working pressure is prevented
may not be accurate. The level gauges are also
on any condition.
used to verify the readings of other instruments.
As the spring loaded safety valves result in high
The level gauges being located at the drum
noise levels when they open, the exhaust of the
level are not convenient for regular operation of
safety valves are connected through a silencer to
the Boiler. The level gauges however must be
substantially reduce the noise level.
maintained in service as IBR requires that atleast
one of the level gauges must be in service to Installation, adjustment and maintenance
operate the WHRB. instructions for safety valves are enclosed which
Section B 21
Operation & Maintenance Manual
3.3 Silencer
Section B 22
Operation & Maintenance Manual
the Evaporation panel tubes, the hot water An inter-stage attemperator is provided in
absorbs heat from the exhaust gas of the coke the superheater to maintain the Þnal steam
oven and gets converted to a water/steam temperature. Spraying a controlled quantity of
mixture. This circulation is assisted by the feed water into the superheated steam lowers its
higher density of water in the down comer temperature as it looses some heat in evaporating
compared to the lower density of water / steam the sprayed water.
mixture in evaporator and riser tubes
The attemperator is a header, which
• The water / steam mixture from the top headers accommodates an inner sleeve shaped like a
of the Evaporation panel, ßows in the steam venturi. A spray nozzle is Þxed at the entrance
drum. to the restricted venturi section. The sleeve
is held in position Þrmly by the locating pins
• In the steam drum, the steam water mixture
welded to the header at the steam entry side.
ßows through the separators where water &
The sleeve is free to expand at the steam exit
steam are separated and saturated steam
side. Water is sprayed through the spray nozzle.
ßows to the Superheaters. Seperated water
The steam passes through the venturi picks up
mixes with boiler water to ßow through the
the spray, which completes the evaporation and
Evaporator panels again.
thoroughly mixes the steam. The connection of
the inlet to the spray nozzle embodies a thermal
3.6 Super Heater sleeve construction to protect the steam line from
temperature differential between the spray water
Superheating of saturated steam from drum and the steam. A drain connection is provided at
is done in two stages in Superheater I & in the exit of the attemperator.
Superheater II. Between Superheater I & II, an
attemperator is located to control the temperature
of Þnal steam outlet at 485°±5°C. 3.9 Super Heater II
Superheaters are made of modules, each Superheater II receives the steam from bottom
consisting of a top header and a bottom header, header of Superheater I. From the top header of
with tubes between the headers. Superheater the SH II, steam ßows through the panel tubes to
modules are hung from their top headers with the bottom header of the same panel, absorbing
provision for thermal expansion down wards & in heat. Then the steam ßows into main steam line.
the sides.
Super Heater II top header (being the top most
point) is provided with Air vents (HPS-VL-110 &
3.7 Super Heater I HPS-VG 109). The interconnecting pipes of the
Superheater and lower headers (Lowest point),
Saturated steam from the drum ßows to the Þrst are provided with two drains (MSS-VG-101/102).
super heater top header of Superheater I. From These drains are operated manually. The air
the top header of the SH l, steam ßows through vents & drains are opened before light up of the
the panel tubes to the bottom header of the same boiler. They are closed at a drum pressure of 2
panel, absorbing heat. Then the steam ßows To 5 Kg/cm².
through the super heater II.
Super Heater I top header (being the top most 3.10 Steam Temperature Control Loop
point) is provided with Air vents (HPS-VL-106 &
HPS-VG 105). The interconnecting pipes of the Attemperator spray control is designed to maintain
Superheater and lower headers (Lowest point), the steam temperature at 485 deg C. As the heat
are provided with two drains (HPS-VG-107/108). pickup in the superheater increases with load, the
These drains are operated manually. The air spray water requirement increases with load.
vents & drains are opened before light up of the
boiler. They are closed at a drum pressure of 2 The spray water line for the Attemperator, spray
To 5 Kg/cm². water is obtained from the Boiler Feed water main,
before the ßow transmitter 11-FE 137. The spray
water line consists of the following.
3.8 Attemperator
An manually operated isolation valve
The function of the attemperator is to control the DSW-VG-101. The isolation valve needs to be
temperature of HHS steam at Superheater I outlet opened when attemperator is to be taken into
and Super heater II inlet to 410°C. service.
Section B 23
Operation & Maintenance Manual
Drain valves DSW-VG-112/113, these drain valves are kept opened during start up upto 5
valves are opened to drain the line for kg/cm2 pressure.
maintenance.
• FLOW NOZZLE Flow nozzle 11-FE-157 is
Pneumatically operated ßow control valve installed on the steam line to provide impulse
11-TCV-153. The ßow control valve is to upstream & down stream pressure readings
provided with inlet/outlet Isolating valves to steam ßow transmitter 11-FT-157. The ßow
DSW-VG-102/108. The inlet/out Isolating transmitter reading, after steam pressure &
valves remain normally open. The drain temperature compensation is used for the
valves DSW-VG-103/104/106/107 which remain following,
normally closed. These drain valves are opened
– Steam ßow reading. (11-FI 157)
after closing inlet/outlet Isolating valves, when
control valve is to be taken for maintenance. – Steam ßow compensation for feed ßow,
steam temperature controllers
The spray water line connects to the spray
nozzle of the attemperator through a non return • SH STEAM TEMPERATURE INPUT
valve DSW-VC-111. Pressure gauge 11-PI-159, Temperature transmitter 11-TE 153 provide the
indicates pressure of the spray water ßowing to steam temperature input for the following
the nozzle.
– Temperature Indicating controller 11-TIC-153
Temperature Indicators 11-TE-151 & 11-TE 152 which provides steam temperature High &
provides steam temperature indication before and low alarms and also controls positioning
after the attemperator to judge the effectiveness of of the attemperator spray control valve as
attemperation. described earlier.
– Temperature compensation signal to the feed
4 Main Steam Piping ßow, steam ßow instruments.
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
Steam Drum
the WHRB from the plant / Common steam
header. This valve is provided with an • Maintain Feed water, Boiler water quality, and
electrically operated, integral by pass valve phosphate concentration.
11-MV 303.
• Maintain water level in the drum within
• SAFETY VALVE 11-PSV-003 This is a spring permissible low and high levels. The protection
loaded, valve set at 71 Kg/cm², pressure to system envisages boiler trip at very high and
protect the boiler against over pressures. The very low levels, which should not be by passed.
safety valve is similar to Drum safety valves
described earlier. The exhaust of the safety • Maintain drum level gauge glasses LI 3401 &
valve is piped to a silencer to reduce the noise PI 34102 in good working condition. Operators
levels when the safety valve is operating. The may verify the readings of level transmitters
silencer is mounted on a separate structure on with the readings of the drum level gauge
top of the WHRB. glasses once a day.
• START UP VENT VALVE 11-PCV 154 is an • Drain superheaters thoroughly during startup.
pneumatically operated regulating start up vent
• THERMAL STRESSES IN DRUM DURING
valve. 11-MV 301 is an electrically operated
START UP AND SHUT DOWN Steam Drum
Isolating valve preceding 11-PCV 154. The
is a large cylindrical shell. Before light up of a
outlet of the start up vent valve is exhausted to
boiler, the inner and outer surfaces of the drum
atmosphere through a silencer. The start up
are at the same temperature. When boiler
vent valve is to be kept open while start up. If
is lighted up, the inner surface gets heated
provides initial steam ßow for the superheaters.
up Þrst by the water (and then by steam) and
• STEAM LINE DRAIN The steam line drain transmits heat to the outer surface of drum.
consists of the following valves manually The heat transfer is by conduction and is a bit
operated MSS-VG-101/102/108/109. These slow. For short time after light up, there can be
Section B 24
Operation & Maintenance Manual
differences of temperature between steam and • Manually operated valves must be closed hand
water surfaces of the drum. Such a difference tight only. Use of levers on hand wheels is not
can set up thermal stresses, which are not desired.
desirable, and an alarm sounds at DCS. To
minimize the thermal stresses, the operator 5.1 Steam and Water System
must restrict the Þring rate when starting the Technical Performance Data
WHRB by modulating the diverter damper.
Boiler water temperature rise rate must not be WHRB HEATING SURFACES
above 56 0C per hour till operating pressure
is reached. ECO Modules (Pass 2) - 827.33 m²
Section B 25
Operation & Maintenance Manual
the noise it creates, and also it affects the visibility d) Low-pressure steam, which can be recovered,
around the draining area. if required, is wasted.
b) High temperatures of these drains can cause HIGH PRESSURE / HIGH TEMPERATURE
scalding injuries to workmen who may come in STEAM AND WATER DRAINS
contact with it.
c) The force and temperature of these drains will
erode the linings of the drain canals.
Sr.
Source Valve Nos Temp of drain °C Frequency of usage
No.
Continuous, quantity
Continuous blow
1. CBD-104 291°C depending on quality
down
of baler water
Occasional during
Emergency blow
2. EBD-102 Upto 291°C high levels in drum,
down
during start up
The drains indicated above table are connected 6.2 Continuous Blow Down Control
to the blow down tank. The blow down tank
is capable of separating steam from the drain CBD control involves the following operations
water. The drains are connected tangentially in
• Obtaining a sample of boiler water from the
the upper half of the drum, to direct the drain ßuid
steam drum.
circumferentially around the inner wall of the tank,
to aid separation of steam and water by their • Analyzing the sample for conductivity,
differences in densities. A vent line of the tank is hardness, NaCL, Silica, Fe, etc., and working
connected to Deaerator. out a rate of draining of boiler water to maintain
the concentrations as suggested in Boiler
Level of water is maintained by a control valve water.
11-FCV-137 through level controller 11-LIC-142
• Manually positioning the CBD valve is to be
decided depending on the sample analysis
6.1 Other Drains
• Repeating the sampling, analysis and
The drains indicated above table are connected repositioning the CBD valve after certain
to the blow down tank. The blow down tank interval is necessary to maintain the required
is capable of separating steam from the drain Boiler water quality. This system of manual
water. The drains are connected tangentially in control requires the services of a sampler, a
the upper half of the drum, to direct the drain ßuid chemist and a laboratory round the clock.
circumferentially around the inner wall of the tank,
The arrangements provided for CBD control is:
to aid separation of steam and water by their
differences in densities. A vent line of the tank is • A perforated pipe, laid along the water space
provided open to atmosphere. in the steam drum connects through a stub to
the continuous blow down line.
It can be seen that drains have been provided in
the feed water line and the attemperator spray • CBD line from drum connects to the blow down
water lines connected to the drain canal. As tank.
these drains are either for operation to drain these
• A tap off from the CBD line is taken to the
lines after an isolation or for short time during
sample cooler for continuous analysis of boiler
charging, their connections to the open canal is
water conductivity and also for a grab sample
not expected to pose a problem.
Sampling of CBD / Boiler water is done in one
• All level control station drain
of the sample coolers of the sampling package.
• All pressure control station drain This package provides analysis of the following
samples to provide a comprehensive information
• Steam drum level indicator.
of quality of steam and water of WHRB.
• Steam drum safety valve drains
• Samples of saturated steam from Top saturated
• Sample cooler sample let off drain steam header of WHRB.
Section B 26
Operation & Maintenance Manual
• Samples of main steam from Steam header • Two dosing pumps (with one stand by)
of WHRB. • DM Water source for preparation of the
• Samples of boiler water (CBD) from the steam phosphate solution as well as for ßushing
drum of WHRB.
7.2 Mixing Tank
• Samples of feed water.
While all the samples above are analyzed for The Mixing tank is a stainless steel covered
conductivity by separate analyzers, the CBD cylindrical vessel of 150 litres capacity; with a
sample and the feed water samples are analyzed level indicating gauge glass (11-LI-701), DM
in addition for pH also. A brief description of the water inlet line (with a manual isolating valve)
salient features of the sample cooler of the CBD HPC-VL-101, an over ßow drain line, a tank drain
analyser is given. Care of other sample coolers line with a manual isolating valve HPC-VB-121, a
is identical. CBD-104 is normally kept open to basket for placing required quantity of tri-sodium
maintain small continuous ßow of boiler water to phosphate powder for preparation of the solution.
the blow down tank. This is required to ensure A solution inlet connection to the pumps with
the sample at any time to the sample cooler is a manual isolating valves HPC-VB-105/106. A
truly representative of the sample being analysed. motor operated stirrer is also Þtted for preparation
This continuous ßow also ensures that these lines of chemical solutions.
do not get chocked for want of adequate ßow. The level of the mixing tank is monitored by level
Valves CBD-VG-102 & CBD-VL-103 are isolating switch (11-LSL-701). Availability of a minimum
valves to the sample cooler which remains open. level is a required permissive condition for starting
The sample cooler is a tube and shell type heat or continued service of a dosing pump.
exchanger with the boiler water ßowing through
tubes and the cooling water in the outer shell, with 7.3 Preparation of 5% Phosphate
the speciÞc purpose of sampling. Cooling water Solution in the tank
is provided from the plant fresh water (DM water
• Tank drain valve HPC-VB-121 is closed.
circuit) in a closed loop.
• Gauge glass inlet cocks are opened and its
Tri-sodium phosphate dosing to Boiler water to drain is closed.
maintain its phosphate content at 2 to 6 PPM. The
tri-sodium phosphate at the suggested levels, • The lid of the tank is opened, and a calculated
maintains the alkalinity of the boiler water (pH 9.5 quantity of phosphate to prepare 150 litres of
to 10.2) and also converts the harmful, insoluble solution is placed in the basket and lid closed.
calcium and magnesium salts which forms the • The water inlet valve HPC-VL-101 is opened
residual hardness of boiler water, to benign to admit water (from the DM water line). The
soluble, sodium salts, in the form of a soft sludge, level gauge is watched and when the level in
to be drained by the CBD. Phosphate dosing, the tank is nearly full, the water inlet valve is
prevents corrosion of the water washed parts of closed.
the steam drum and the evaporator tubes, by • The stirrer is placed in service for 30 minutes
adjusting the speed or the stroke of the pump by operating its switch in the local panel.
provided as described below. Excess as well as Availability of a minimum level is a precondition
reduced phosphate levels in Boiler water should for starting and running of the stirrer.
be avoided. (The phosphate dosing is also some
times called as "HP dosing" as the pump used 7.4 Phosphate Dosing Pump
develops high pressure to dose against the boiler
drum pressure). Two phosphate dosing pumps are provided, out
of which one is in service at a time, and the other
7 Chemical Dosing & Sampling is a standby. The pumps are plunger operated
System reciprocating, positive displacement type. The
stroke of the plunger can be altered. The motor is
7.1 HP Dosing System provided with a variable frequency drive through
a gear box for continuous speed control. The
The equipment, which are of stainless steel, vendor manual of the pump and gearbox is to be
provided for phosphate dosing (“HP dosing”), are provided for full information on construction and
shown in P & I diagram and consists of parts detail.
• A mixing tank for preparation of 5% tri-sodium Each pump is connected to a common discharge
solution. line with the following valve arrangement:
Section B 27
Operation & Maintenance Manual
• An inlet valve with a "Y" strainer at the pump the motor. The pressure gauge is observed. It
inlet. Y strainer traps dirt or other solid particles should show a reading, higher than the steam
in its basket. The Y strainer is to be cleaned drum pressure. An accumulator on the pump
once a month, after stopping the pump and discharge line dampens the pulsations which
closing its inlet and outlet isolating valves. otherwise would be there as this is a positive
displacement reciprocating pump.
• On the discharge side of the pump, a pressure
gauge and an outlet isolating valve is Þtted • Any abnormal noise from the pump, motor
before the common discharge line. A safety or gearbox is noted. The safety relief valve
relief valve has also been Þtted on the should not also be operating. If there are no
discharge line to relieve any over pressures in abnormalities the pump is allowed to run.
case of closure of valves on the discharge line. • Every four hours, the phosphate content in the
The outlet of the relief valve is returned to the boiler water is checked by laboratory sample
mixing tank. The relief valve must be tested for analysis and also by the pH meter. The pump
its operation at the set pressure atleast once speed stroke is increased or decreased to
a year. The pump must not be operated with maintain the phosphate content within 8 to 10
the relief valve continuously operating. (cause PPMS by continuous pump operation.
of relief valve operation must be found and
rectiÞed). • The phosphate solution level is observed in the
mixing tank by the gauge glass. If the level
• The common discharge line is connected to falls to 25% of the gauge glass level, additional
the HP dosing line of the steam drum through solution is prepared as stated above.
an NRV and an isolating valve1. The isolating
valve is veriÞed open before boiler light up and FLUSHING THE PHOSPHATE PUMP AND
normally remains open all the time. Phosphate THE LINES WITH WATER DURING LONG
dosing is through a perforated pipe along the STOPPAGE OF THE WHRB:
full length of the water space in the drum. If the WHRB is to be stopped for more than a few
Availability of a minimum level in the mixing days for servicing or maintenance, the phosphate
tank is a pre condition for starting or running of pumps and the line are ßushed with water to keep
the dosing pumps. Out of the two pumps, one them clean in the following manner.
pump is selected for service and the other is in A (ßushing) line is connected from the tank
reserve (DCS macro, Local panel). The pumps solution preparation DM waterline to the inlet line
are interlocked such that when a working pump of the pumps . The pump which was in service
trips, the reserve pump starts automatically. earlier is run, for about 30 minutes to one hour.
DM Water ßushes the phosphate solution from
A phosphate pump is placed immediately in
the pump and the lines to the steam drum and
service after the WHRB start up in the following
cleans them. The pump is stopped. The outlet
manner:
valve from the mixing tank, is not opened till the
• Boiler water sample is analyzed and phosphate boiler is again lighted and a phosphate pump is
content is determined. required in service. At that time the isolating valve
on the DM line is closed.
• The pump is prepared by opening the outlet
valve from the mixing tank, opening the inlet NOTE:Do not operated the Stirrer of the HP
and the two outlet valves of the pump. Two dosing pump when the HP tank is dry or not
minutes are allowed after opening the inlet Þlled with water or the dosing solution. The dry
valve for the pump to get Þlled with phosphate operation of the stirrer can lead to failure of the
solution. The pump is started by switching on stirrer (misalignment of the stirrer).
Section B 28
Operation & Maintenance Manual
7.5 Water And Steam Quality Control free operation of the WHRB and for obtaining pure
And Monitoring steam. Methods of control of boiler water are also
explained.
AIM
Suggested quality of boiler feed water (and
This chapter describes the standards for the boiler attemperator water) fed to the WHRB is given in
feed water and boiler water for corrosion and scale 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 <0.02ppm
Total Iron as FE < 0.01 ppm
Copper as CU < 0.003ppm
Dissolved Oxygen < 0.007cc/lit
Sodium Sulphate Not traceable
Residual Hydrazine Traces
Organic matter Nil
Oil Nil
Total dissolved solids < 0.1 PPM
Conductivity at 25°C after cation exchanger and
< 0.15 micro siemens per cm
CO2 removal
Total CO2 Nil
Sodium + Potassium Not traceable
Section B 29
Operation & Maintenance Manual
Section B 30
Operation & Maintenance Manual
• Increase of saturation steam conductivity may the WHRB through an expansion bellow. The
be a warning for check of drum internals or following are the instruments in the ßue gas
maintaining high water levels in steam drum. system.
It should be understood that if the quality of Boiler Exhaust gas from the Sponge iron kiln enters
feed water deteriorates, the steam quality is the WHRB through an expansion bellow. The
directly affected as the attemperator spray water following are the instruments in the ßue gas
is by boiler feed water.. system.
After several years of service, during a boiler BEFORE SUPER HEATER:
over haul, bafßes and demister are checked for
• Flue gas pressure at DCS, from pressure
damage or erosion holes, which may bypass
transmitter 11-PT-160.
steam from the separation devices. Steam which
bypasses the separation devices carry with it • Temperature transmitters 11-TE-162 &
moisture, with its salt contaminants to steam. 11-TE-164 for remote indication in DCS.
Higher than permissible levels of Silica in boiler • These temperature transmitters measure the
water will result in Silica carry over in steam. temperature of exhaust gas. This is provided
to safeguard the Superheater II, Superheater
7.7 Operational Control I, Evaporator panels.
• Pressure transmitter for remote indication
• The water chemistry for determining low
11-DG-161/163
levels of impurities in water calls for special
instruments, special analytical procedures and AFTER SH II
an experienced chemist. These should be
• Temperature indication at DCS 11-TE-165.
available from the time of commissioning the
boiler. (An increase in pressure drop for the same inlet
• In a chemical process plant, in spite of the best conditions or drop in heat pickup may suggest
available demineralization facilities the boiler fouling of SH II panels and a need for soot blowing)
feed water may occasionally get contaminated AFTER SH I
by return condenses from the system. A
procedure to systematically check the return • Temperature indication at DCS 11-TI-167
condensates (particularly for contamination by • Local pressure indication 11-DG-166
Fe, Chlorides and Oil) must be established and
contaminated condensates must be discarded. AFTER EVAPORATOR I
• pH & Conductivity meters must be calibrated • At DCS 11-TE-168 the instruments are for
once a month. measuring the heat pickup in Evaporator I and
to institute soot blowing if fouling is suspected
• Phosphate dosing must be adjusted for
in Evaporator panels.
continuous operation.
• Local pressure gauge 11-DG-169 for
8 Flue Gas System measuring draft.
AFTER EVAPORATOR II
This chapter describes the sponge iron kiln
exhaust ßow through the WHRB, insulation and • At DCS 11-TE-170 the instruments are for
casing of WHRB and the Stack, various sealing measuring the heat pickup in Evaporator I and
air connections are also indicated.. to institute soot blowing if fouling is suspected
in Evaporator panels.
8.1 System Description • Local pressure gauge 11-DG-171 for
The steam drum & WHRB pressure part panels measuring draft.
are supported on column structures. Insulation AFTER ECONOMISER
& steel casing is applied enclosing the panels
to provide a gas tight passage for the exhaust • AT DCS : Temperature indicator 11-TE-172 to
gas from the Sponge iron kiln. WHRB panels & measure the heat pickup in Economizer and to
drum are supported on structures. The panels evaluate fouling if any on Economizer panels.
are covered fully with insulation and aluminums • Local pressure gauge 11-DG-171 for
cladding. The insulation is held by strips and measuring draft
the screws as shown in the respective drawing.
Exhaust gas from the Sponge iron kiln enters STACK (CHIMNEY)
Section B 31
Operation & Maintenance Manual
The oven exhaust gas after ECO is exhausted 9 Soot Blower System
through the Stack. The stack is a hollow
cylindrical structure (Customer scope) 9.1 Soot Blower
Aviation warning lights are Þtted at two elevations
AIM
on the stack. Sampling probes for measurement
of CO, NO2 & SO2 are Þxed at two suitable Soot blowers, 09 in number, have been provided
elevations on the Stack. There are Þve platforms for SH II, SH I, Evaporators and Economisers.
providing access to the aviation lights, sample A PLC based local control panel for operation
probes and ease of repainting the Stack. The and control of these soot blowers are provided.
platforms are accessible from the ground by Vendor manuals of the soot blowers and the local
ladders. On the top 20metres of the Stack, helical control panel have been included in Volume VIII
wind breakers are built around the outer shell, to of this manual, which may be referred for details
provide stability to the Stack against wind forces. of their construction and mode of operation. This
chapter explains steam supply to the soot blowers
8.2 Operational Control and deals with the need for soot blowing, factors
determining the optimum frequency and care to
• The anticipated performance Þgures both be taken during its operation.
steam / water and gas side has been given
in following section. The operator shall
9.1.1System Description
familiarize himself with these Þgures. Elaborate
instrumentation has been provided to measure Operating environment of Soot blowers
each of these factors. Alarms also have
been provided to alert the operator in case of
deviations for several of these readings
• Operator attention is needed particularly for
the following - Kiln Exhaust Gas inlet pressure
and temperature - Gas side pressure and
temperature drop, Steam/Water side heat pick
up across pressure parts like,
– SH II
– SH I
– Evaporator Panels
– ECO
Evaluating these Þgures the operator should
decide the need for soot blowing. (Or other
checks during a shut down).
– Levels of CO, NOX, SOX emissions must
be monitored and any abnormalities must be
reported to the shift in charge
– Healthiness of aviation warning lamps are to
be check periodically
Soot Blower
LRSB LRSB LRSB & RSB RSB
Number
Between Between Between Between
Position Evap II & Eco
SH II & I SH I & Evap I Evap I & II
modules
Angle of rotation° 0-360° 0-360° 0-180° 0-360°
Section B 32
Operation & Maintenance Manual
in use. The steam admission to the LRSB is • Flue gas temperature across super heaters,
automatically established as soon as the LRSB Evaporators, Economizers.
enters the ßue gas path. Cleaning operation, by
• Feed water / steam temperature pick up across
jetting steam from the LRSB takes place both
super heaters, Evaporators, Economizers.
during its advancing and retracting cycles. The
steam ßow through the lance also serves to cool • Spray water ßow through de-super heater
the lance tube from the excessive heat of the ßue Effective soot blowing increases the heat pick
gas. For this reason, the LRSB should never be up. De-super heater spray water ßow may
advanced, When an WHRB is in service, without increase.
steam, if an LRSB is being operated, occasionally
It can also happen that there is no change after
it may happen that it gets stuck in the extended
a soot blowing. From a careful study of these
position due to overload. ("Blower Mechanical
parameters, an optimum soot blowing program
Jamming", Soot blower motor overload" Travel
can be established related to the fuel.
time exceeded alarms on panel). When this
happens, steam from the lance nozzles will be An effective soot blowing can only be done when
jetting against the same position on the tube the WHRB steam ßow is above 50% MCR. Soot
panels which may cause on erosion of those blowing at lesser loads may disturb the ßue gas
tubes leading to a possible tube failure at a later regime. The Þrst soot blowing after the WHRB
date. To avoid such steam cutting of the tubes, start up is done as soon as 50% MCR steam ßow
the operator must declutch and manually retract is established on the WHRB. Similarly when a shut
the soot blower immediately using the hand down is planned on the WHRB for inspection or
cranks provided (see soot blower vendor manual). maintenance, the last operation before reducing
("Travel time exceeded alarm"). Steam must not the load below 50% MCR should be a soot blowing
be closed to the LRSB till it is fully retracted for so that the panel tubes remain clean during the
cooling requirement. Special care is needed for shut down without harmful effects of corrosion.
retraction of soot blowers 1 to 3 which work in
possible high temperature zone which will get 9.1.3Operation and Control
damaged without cooling steam.
The operation & control is described by a write-up
Soot blowers are operated in a deÞnite sequence
on sequential soot blowing operation
in the line of ßue gas ßow, starting from SH II
through SH I, Evaporators, Economizer. When
a soot blower is operated, say from SH II, the 9.1.4Pre Interlocks
soot dislodged from it is likely to resettle on Soot blowing operation can be selected either in
any of the subsequent heating surfaces (SH I, Auto mode from PLC or manual mode by using
Evap II, II, ECO modules) etc. When the soot selector (soft) switch available in PLC. In auto
blowing is done in the speciÞed sequence, all the mode following interlocks need to be satisÞed for
soot, including those which resettle are cleared. starting the operation.
Resettlement of soot however will be more
pronounced on cooler heating surfaces (ECO) for • All soot blowers in rest position, feedback
instance. taken from individual S.B. Limit switches
Frequency of soot blowing : When the • SB Steam isolation valve open and drain valve
WHRB are on line, once in a day may be closed
considered. An optimum frequency can only be With these, Soot Blowing in Auto Lamp will glow.
established by carefully studying the beneÞts Auto sequence can be started from PLC by giving
of soot blowing or excessive fouling caused by start command with following conditions in healthy
inadequate soot blowing. When the WHRB is state
in continuous service, a fouled super heater will
make attaining the design steam temperature • SB in Auto selected (a knob is provided in the
difÞcult. Unabsorbed heat from Evaporators control room which can select the SB in Auto
and Economizers will increase the ßue gas exit or Manual mode, to continue the sequence of
temperature from WHRB higher than design, the SB, Auto mode needs to be selected)
reducing the thermal efÞciency. Effectiveness of
• SB sequence reset PB not operated
each soot blowing can be studied by noting down
the following performance parameters before and With this, auto sequence ON lamp will glow and
after soot blowing. sequence continues on sheet 3 for drain valve
Section B 33
Operation & Maintenance Manual
open logic. Reset P.B. is used for resetting Positive feedback of forwarding contactor in MCC
before restarting the sequence and resetting the is taken for SB1 forwarding lamp indication.
mechanical fault condition
As soon as the S.B.1 forward position L.S.
DRAIN VALVE OPERATION (OPEN) is operated in forwarding operation of SB
-1, forwarding command shall break & SB1
Drain Valve to be kept open before starting the
forwarding shall stop. Also if any of the above
soot blowing cycle for LRSB and RSB. This
mentioned condition goes unhealthy state
ensures removal of condensate accumulated
forwarding shall stop. Simultaneously Retracting
inside the piping.
command shall start retracting operation with
The removal of condensate is important because following conditions satisÞed.
the water if injected during soot blowing operation
• Fault (overload) not operated
will result in water hammering effect, erosion of
soot blower lance, erosion of tube surface and • S.B 1 is not forwarding
more temperature gradient than required at that • S.B 1 rest position limit switch is not operated
zone causing thermal stresses.
In retracting operation when SB1 hits the rest
S.B. STEAM ISOLATION VALVE OPEN position limit its retracting stop pulse command
Ensure that the inlet isolation valve MPS-VG-101 stops the retraction. Sequence is continued to
is in open condition. The upstream and next pre selected soot blower.
downstream valves of soot blower pressure
Manual operation of SB1 forwarding is possible
control station should be in open condition.
from Local P.B. when manual mode is selected
DRAIN VALVE OPERATION (CLOSE) from PLC (which is Auto mode de selected).
Manual operation of retracting is possible from
Close the drain valves of LRSB and RSB local P.B. in both auto and manual mode. It
steam piping after ensuring complete removal of is also ensured that if any of the soot blowers
condensate. is somewhere in mid position when the power
However it is advisable to kee the drain valves supply is switched ON, the SB shall Þrst retract
crack open during the entire soot blower cycle and comes to its rest position irrespective of
completion for continuous removal of condensate Auto/Manual mode.
and maintaining the required steam temperature Positive feedback of retracting contractor in MCC
is taken for SB 1 retraction and lamp indication
9.1.5 SOOT BLOWING SEQUENCE
SEQUENCE COMPLETE
SB-1 (RETRACTABLE)
With the sequence continued from SB Steam
Sequence continues from SB -1 forwarding isolation valve close logic and following condition
sequence starts with a time delay of 5 secs with satisÞed sequence completes an respective lamp
following satisÞed. glows
• Sequence continued to SB 2 condition 1. All soot blowers in rest position .
unhealthy. This ensures that there is no repeat
operation of S.B.1 after completion of its one 2. SB Steam isolation valve close
cycle Sequence complete signal is used as pre
• SB1 is pre-selected (if not pre-selected interlocks.
operation of SB1 is skipped and sequence MECHANICAL FAULT
continues to SB 2 or next pre-selected S.B)
In case, any of the soot blowers remains in
• Forward position limit switch is not operated
operation for more than 300 sec. Which is an
• Retract P.B. is not operated abnormal condition in operation, mechanical fault
• SB Steam isolation valve is opened alarm is generated. This condition shall occur
because of mechanical failure of soot blower.
• DV is closed Corrective action can be taken on the same
• Steam temperature is achieved ELECTRICAL FAULT
• SB 1 is not retracting
In case Retractable soot blower trips on overload,
• SB 1 fault (overload) is not operated (contact indication Lamp shall glow. One common
from MCC) overload for all retractable soot blowers is
Section B 34
Operation & Maintenance Manual
provided as at a time only one soot blower is in As the system protections and interlocks have
operation. been described in the preceding chapters along
with the description of equipment, a listing of
GENERAL NOTES
these protections will only be made with brief
• Open, close on commands going to actuators notes on their signiÞcance. Testing of these
and MCC are isolated potential free contacts interlocks & protections is to be done before the
of relays. Þrst start up of WHRB and at suitable intervals
• Actuators shall receive only open or close subsequently.
command from PLC other necessary
interlocking of switch gears for open close Safety Valve on Steam Drum & Superheater
operation is done inside the actuator integral
starter To protect the boiler safety valves have been
provided with set points and blow down capacities
as indicated below
10 Boiler Protection & Interlock
AIM
10.1 Alarms And Interlocks The control acts on spray control valve, which is a
pneumatically operated control valve, positioned
Interlocks provided for various systems ensure by positioner.
safe and sequential operation at any point of
operation which includes start up, shut down and Drum Level Control
emergency conditions. Kindly refer the Section-C
for the detailed description of the Alarms & It includes:
Interlocks Description.
• Single Element Control
10.2 Operational Control • Three Element Control
SINGLE ELEMENT CONTROL After density
The interlocks are to be tested before
compensation the drum level signal is used
commissioning. Repeat tests are advised once a
for indication, control and generation of, Low
year. Any malfunction noted during operation has
alarm, and High alarm.Input goes as PV to the
to be attended early.
single element Controller 11 LIC-142A. Out put
of this controller is feed to the level control valve
10.3 Automatic Control 11-FCV-137. Single element controller should
be used up to 30% load of the boiler. Above
AIM that select three element control to maintain and
To describe the automatic controls provided for control the Drum level with respective to boiler
operation of the WHRB. load.
In case of bad PV both control should go to
Steam Temperature Control Manual mode automatically. And alarm should be
generated.
The steam temperature control has following
function: PV tracking and SP tracking should be provided
to this controller for Auto/ Manual bump-less
To position the spray water control valve such a
transfer.
manner that S.H. steam temperature at outlet of
SH II is controlled at 540 Deg C. THREE ELEMENT CONTROL
Section B 35
Operation & Maintenance Manual
In Three element control O/P of 11 LIC-142B The action of the 11 LIC-142B (Three Element
goes to the summation block where the steam controller) is Reverse i.e. out put of the controller
ßow signal (0-100%) is added to 11 LIC-142B will decrease if the PV increases.
output. Action of 11 LIC-142B controller is
The action of 11 FIC-137 controller shall be direct
reverse. The output of summation block is
action i.e. as the Feed water ßow goes above set
used as a remote set point for the feed water
point; the 11-FCV-137 should close (i.e. the 4-20
ßow controller 11 FIC-137. Remote set point
mA output should increase).
calculation is given below.
(11 FIC 137) shall have only two modes of
Remote SP for Water Flow Controller (11-FCV
operation. 1. Manual mode 2.Cascade mode
137) = Drum Level Controller (11-LIC 142B) O/P
in % + (Steam ßow signal (11-FT-157) in % * Gain) (11 LIC 142A & 11-LIC-142B shall have only two
+ (Bias in %) modes of operation namely. 1. Manual mode 2.
Auto mode
On Bad value of PV, the controller 11-FCV -137
shall be automatically switched to manual mode. SP shall track its PV in manual mode and shall
have its local setpoint.
• If (11-FCV 137) is put in manual mode, then
(11-LIC 142B) is to be forced to manual mode. Indications and alarms to be conÞgured as shown
in the control schematic. Trends, Totalizers,
• SP tracking shall be provided for (11-LIC 142A
indicators and alarms shall be conÞgured in the
& B) in manual mode.
DCS as indicated the Control Schematic drawing.
• (11-LIC 600A & B) SP shall track its PV in
manual mode and shall have its local setpoint. Totaliser 11 FIQ-137, 11 FIQ-157 to be conÞgured
in DCS.
Water ßow is measured using transmitter 11-
Following are trip interlocks on Drum level Low
FT-137 which receives DP from ßow nozzle 11-
Low
FE-137, the square rooting to be done at DCS
side and is used as process variable for Feed • a) ID fan trip
water ßow controller 11- FIC-137. The output
• b) Open ßue gas process stack inlet damper
of 11- FIC-137 is used to control the feed water
(11-DI-004)
control valve 11- FCV-137.
• c) Close ßue gas damper to boiler inlet
Steam ßow is measured using a steam ßow
(11-DI-003)
transmitter 11 FT-157 connected to ßow nozzle;
the steam ßow transmitter shall be square rooted • d) Close damper in recirculation line
at DCS side. (11-DI-005)
T2- Design Temp of steam, in deg C • Action of controller 11 PIC-160 is Direct. The
action of the PID can be changed at site
[P2 = 66Kg/cm2 absolute & T2 = 485+5 Deg C] depending on linkage
11 LIC-142A Controller action should be direct i.e. • HIC-160A and HIC-160B shall have Auto/
Controller output will increase if PV increases. Manual selection.
Section B 36
Operation & Maintenance Manual
• On Selection of VFD mode damper of same with a Þxed set point in the Proportional-Integral
fan should not go to Auto mode controller 11 PIC-147. The resultant control signal
actuates soot blower control valve 11-PCV-147.
• Furnace presses Low & high alarms are
generated from 11 PIC-160. • Trends, • Soot blower pressure Low & High alarms are
indications and alarms shall be conÞgured in to be conÞgured from 11 PIC-147
the DCS.
• The action of the soot blower pressure.
Note Controller 11 PIC-147 is Reverse.
• The ID fan not running signal is taken • Fail safe action is close.
from drive logic to close the ID fan • Trends, indications and alarms shall be
damper when ID fan not running. conÞgured in the DCS.
• When furnace pressure is controlling
through VFD mode then ID fan damper DEAEARATOR PRESSURE & LEVEL
will be 100 % open & controlling is CONTROL
through VFD
Pressure transmitters 11-PT-105 measures the
• When furnace is controlling through deaerator pressure & fed to the 11-PIC-105 for
damper then ID fan motor is in full Deaerator Pressure Controller as a PV . The
speed & controlling is through Damper. output of 11-PIC 105 acts on the deaerator
Pressure Control Valve 11-PCV-105. The
STEAM TEMPERATURE CONTROL controller shall have Reverse action. The
controller shall have PV tracking for manual to
The temperature of Þnal steam is controlled by auto bumpless transfer.
attemperation i.e. by spraying feed water into the
steam after the primary super heater. • The action of the Deaerator Pressure Controller
shall be reverse.
11 TIC-153 receives Þnal steam temperature
as the process value from 11 TT-153. The • Action of DA Pressure control valve 11-PCV
temperature controller shall have 485 °C set point -105 is air to open type.
for the Þnal steam temperature. The out put of the • Fail safe action is air fail to close.
TIC will be given to the Attemperator temperature
control valve 11 TCV-153. The controller shall Deaerator pressure High & Low alarms are
have Reverse action. The controller shall have generated from 11-PIC 105 signal.
PV tracking for manual to auto bump less transfer.
Level transmitter 11-LT-102A & 11-LT-102B
• Steam Temperature Low,High and High High measures the deaerator level.The output of these
alarms are to be conÞgured from 11 TIC-153 given to 11-LY-102 1002 block .The output of
11-LY-102 fed to the 11-LIC-102 as the PV for
• The action of the Steam Temp. Controller 11 Deaerator Level controller. The output of 11-LIC
TIC-153 is Reverse 102 acts on the Deaerator Level control Valve
• The actuator of Steam Temp. Control valve: 11 11-LCV-102. The controller shall have direct
TCV-153 is air to close type. action. The controller shall have PV tracking for
manual to auto bumpless transfer.
• Fail safe action is Stay put /Tends to Open.
• The action of the DA Level Controller shall be
• Trends, indications and alarms shall be
direct.
conÞgured in the DCS.
• Action of DA Level control valve LCV-002 is
SOOT BLOWER PRESSURE CONTROL air to close type.
• Fail safe action is open on air fail..
The soot blower pressure is measured using
pressure transmitter 11 PT 147. This is used as Deaerator Level High & Low alarms are generated
a process variable (PV) and is then compared from LIC 102
Section B 37
Operation & Maintenance Manual
Section C 38
Operation & Maintenance Manual
supply to boiler insuring that proper valves are temperature and the steam drum pressure is to
opened or closed as the case may be. be controlled as mentioned in the Start-up curve
attached. Annexure – I.
3.2.1See the following valves are closed
positively 1. Minimum 1/3rd of steam generation to
be vented to assist natural circulation of
• Feed water regulating valves are closed and boiler and to control superheated steam
are in manual control. temperature. At any point of time during
• All blow-down and drain valves on boiler and startup the superheater steam temperature
water walls should not exceed the temperature mentioned
• Soot blower steam supply valve in the curve. By Adjusting the Attemperator
water ßow and ßue gas ßow this can be
• Main steam stop valve achieved.
• Attemperator control and bypass valves
Note
• Drain valves for instruments.
• CLOSE ALL THE SUPERHEATER
3.2.2Open the following valves: DRAIN VALVES WHEN THE
HEADERS ARE FREE OF
• All steam drum vents
CONDENSATE
(SD-VG-119,SD-VL-120),Puppy header
vent(HPS-VG- 101,HPS-VL-102) • CLOSE DRUM VENTS
• All instrument and control connection to the (SD-VG-119,SD-VL-120) AS
boiler PRESSURE REACHES TO 3
KG/CM2
• Superheater header vents
HPS-VL-106/110,HPS-VG-105/109, drains • CLOSE PUPPY HEADER
HPS-VG-107/108, MSS-VG-101/102, startup VENT Puppy header
vent MV-301,PCV-154, and main steam line vent(HPS-VG-101,HPS-VL-102)
drains MSS-VG-108/109. AND SUPERHEATER VENTS
HPS-VL-106/110,HPS-VG-105/109
3.3 Filling With Water AS PRESSURE REACHES TO 5
KG/CM2.
Fill the boiler to about 2 inches below normal
water level on the level gauge, thus allowing 2. As the steam pressure reaches 60% of
room for expansion of water with heating and operating pressure open the bypass of
pressure rise. Only boiler quality feed water main steam stop valve(MV-303) gradually
should be used for Þlling. It is desirable to Þll and allow heating up of steam piping
the boiler with de-aerated feed water. Filling approximately for 30-45 min. This will help
with hot water is permissible provided water draining of condensate through the steam
is added slowly and ßow does not exceed trap bypass line and attaining operating
capacity of de-aerating heater. Strains set up in temperature of piping. After attaining the
the waste heat recovery boiler from hot water required temperature & pressure gradually
Þlling are minor compared to strains induced open the main steam stop valve MV-302
from heating cold water rapidly. When Þlling and close the startup vent valve PCV-154,
with water, drum vent(SD-VG-119,SD-VL-120) bypass of main steam stop valve MV-302.
should be opened to permit escape of After achieving the above, opens the stop
steam or air. The super-heater header drain valve fully. All steam traps should be lined
valves(HPS-VG-107/108,MSS-VG-101/102) are up and the by pass valve to be closed and
all kept open for removal of condensate (i.e. soon check periodically for proper removal of
after taking the ßue gas in to the boiler). All the condensate..
respective valves on the startup vent piping are
to be kept open. 3. During all the above steps, maintain normal
water level in the steam drum. Initially, the
3.4 Heating Up controls should be on manual mode only
and once the steam supply to the process
Once the boiler has been Þlled with water, the ßue is started, change the controls in auto mode
gas may be taken into the boiler. The ßue gas and monitor continuously.
Section C 39
Operation & Maintenance Manual
Section C 40
Operation & Maintenance Manual
Figure 2
Section C 41
Operation & Maintenance Manual
Section C 42
Operation & Maintenance Manual
5.2 Emergency Shutdown Procedure • Observe the air vent on drum. Air gets expelled
and steady steam starts coming out of the air
1. Open the By pass duct damper (DI-004) vents
and close the damper at boiler inlet (DI-003)
• Observe drum pressure (PT-145) at DCS as
and ID fan outlet damper(HV-179A/B) and
also local pressure gauge PG-146
regulating damper DM-001.
• When drum pressure shows 2kg/cm², drum air
2. Open the start up vent PCV-154 gradually and
vents can be closed SD-VG-119, SD-VL-120
close the main steam stop valve MV-302.
• When the steam pressure builds up to 2 kg/cm²
3. Follow pt. No. 4 to 10 of normal shut down
. super heater drain valves are to be closed
procedure
(HPS-VG-107/8,MSS-VG-101/2)
5.3 During Black - Out Procedure • When the swelling phase of drum water level is
Condition over and the level shows a decreasing trend,
the 25% feed control can be taken into service
• During the Black out condition by opening isolating valves .it can be positioned
as required manually to maintain drum level
• Open the by pass duct damper DI-004 and
close the damper at boiler inlet (DI-003) & ID • Ensure CBD, feed water and super heated
Fan out let (HV-179A/B), regulating damper steam samples are ßowing to the coolers and
(DM-001). the pH, conductivity meters are in operation.
Verify pH and conductivity are within permissive
• Ensure that ID fan inlet controlling damper is in values.
fail-safe position i.e., close condition.
• Allow the WHRB steam pressure and
• Close the MSSV (MV-302) and open the temperature to build up to rated temperature
startup vent (PCV-154) to minimum position and pressure by suitably adjusting ID fan
just for protecting the superheater (ensure speed.
to avoid overshooting of main steam temp
(TT-153). • When steady feeding is established through
the feed control valve, the same can be taken
• The BFP should start with in 3-min with the on auto mode, by switching into automode.
help of emergency power supply and manually If sluggish, continue manual operation of for
maintain the water level in the steam drum. some more time before trying again.
• Emergency power supply has to be provided to • • Monitor the steam drum water level
the MSSV, Startup vent, inlet hot gas damper, (LT-142A/B).
ID Fan discharge damper and by pass duct
damper. The steam drum pressure and the • Monitor the parameters, which can cause a
level has to be manually maintained. WHRB trip
Section C 43
Operation & Maintenance Manual
• Reduce the opening of the start up vent When the steam drum pressure is less than
valve (PCV-154) to about 15%. This valve 2 kg/cm2 (g), the access doors in the WHRB
can be completely closed later (once are kept open to create a natural draft through
boiler is connected to plant completely.) • the WHRB to the chimney. WHRB cools to an
Desuperheater TCV-153 can be taken in accessible level in about three-four days.
service if SH II outlet temperature TT-153 is
exceeding rated value. 7.3 Forced Cooling
• Observe steam temperatures after SHII TT-153 If the WHRB has to be made available for
• Observe the feed control station. When steam inspection or repair and the shut down time has
ßow established FCV-137 can be taken in auto to be reduced to a minimum, forced cooling of the
mode. WHRB is done.
• Observe the feed control station. When After the shut down of the WHRB, the HP dosing,
steam ßow exceeds 25%, full load control CBD, IBD and sample cooler valves are closed
station comes into service (based on operator as for natural cooling. Water level in the drum is
selection) also maintained between permissible levels till the
steam drum pressure falls to 2kg/ cm2 (g).
7 Cooling of Shutdown WHRB &
For 8 hours after the shut down, the WHRB is
Its Preservation
allowed to cool naturally in the boxed up condition.
This chapter describes the methods of cooling a After 8 hours, access doors on WHRB are opened
shut down WHRB and the steps to be taken to to allow airßow through the WHRB to the stack.
preserve the WHRB to minimize corrosion. The de-pressurization of steam in the WHRB is
also speeded up by controlled opening of the start
7.1 System Description up valve PCV-154.
WHRB after shut down has to be cooled carefully. However forced cooling is not done unless
Permissible cooling rate of the WHRB is only half absolutely essential.
the permissible rate of heating. If the cooling
rate is accelerated, thermal stresses develop in 8 Do’s and Dont’s
the thick components such as the steam drum,
Economiser, Evaporator, Super Heater headers, DO’S
Attemperator etc.,
1. Maintain all instruments and interlocks in good
A WHRB is shut down either for keeping it in working condition.
reserve as a stand by unit or for maintenance
2. All equipment interlocks should always be in
and inspection. The purpose of the shut down
line
determines the method of cooling to be adopted.
3. Maintain normal water level in steam drum
7.2 Natural Cooling 4. Maintain water quality as per the
recommended limits. A table showing the
The WHRB after a shut down is allowed to cool
DM water & drum water quality is included at
slowly in a ‘boxed up condition’. The following
the end of this section
valves are also closed.
5. Pressure raising from cold start must be done
• HP dosing to Drum HPC-VG-118 as per the cold start up curve
• CBD from Drum CBD-104 6. All the duct joints must be leak proof
• Sample line to WHRB water sample cooler
7. Use proper lubricant and maintain
• Sample line to saturated steam sample cooler the schedule as recommended by the
& SH steams sample coolers manufacturers
The WHRB cools slowly, loosing its heat by 8. Operate the WHRB within the recommended
radiation to the environment. Till the steam drum operation limits
pressure drops to 2 kg/cm2 (g), permissible 9. WHRB, piping, ducts must be properly
water level is maintained in the drum (+150mm insulated
to – 250mm) by intermittent feeding. After
the steam drum pressure falls below 2 kg/cm2 10. Servicing of equipments should be done as
(g) maintaining water level in the drum is not per the manufacturer’s schedule
essential. 11. Maintain proper operation log sheets regularly
Section C 44
Operation & Maintenance Manual
Section C 45
Operation & Maintenance Manual
Section C 46
Operation & Maintenance Manual
SL
NO PARAMETER UNIT Time
26 FEED WATER ANALYSIS:
PH
CONDUCTIVITY
TDS
SILICA
HARDNESS
OXYGEN
27 DRUM WATER ANALYSIS:
PH
TDS
ALKALINITY AS CaCO3
SILICA
PHOSPHATE AS PO4
SULPHITE AS SO3
Section C 47
Operation & Maintenance Manual
10.2.1Causes
10.1 Low Water Level
CAUSES
10.1.1Causes
• Feed water control malfunction
• Feed water control system failure. • Operator error
• BFP failure 3
• Instrument air supply failure
• Tube leak
• Foaming
10.1.2Action
10.2.2Action
Compare control room indication with gauge
glass level. If the water level falls out of sight due • Take the drum level control loop into manual
to momentary failure of water supply system, due mode
to negligence of the operator, due to momentary • Reduce the water level immediately by
ßuctuations that might occur with extraordinary operating the emergency blow down to
changes in load, appropriate action should be maintain the drum level
taken at once to trip the fuel. Any decision to
continue to operate, even if only for a short time • Reduce the steam discharge rate, if necessary
at a reduced rating would have to be made by
• Start the stand by compressor if required
someone in authority who is thoroughly familiar
with the circumstances that led to the emergency
and positively certain that the water level can be 10.3 Tube Failure
restored immediately without damaging the boiler.
In the absence of such a decision
Operating the boiler with a known tube leak is not
• Stop the ID fan and open the stack cap recommended. Steam or water escaping from
a small leak at pressure can cut other tubes by
• Shut off steam ßow impingement and set up a chain reaction of tube
Simultaneously, if feed water has become failures. Large leaks can be dangerous. The
available and the operator is assured that no boiler water may be lost, boiler casing can get
pressure part has been damaged damaged.
• Take the feed water control system into manual Small leaks can sometime be detected by the loss
mode. of water in the cycle or system. A loss of boiler
water chemicals or by the noise made by the leak.
• Allow the water ßow to boiler gradually to If a leak is suspected the boiler should be shut
normal water level. (Do not hurry up which down as soon as possible by following the normal
may lead to sudden quenching and tube leak) shutdown procedure.
if pressure part damage is suspected
After the exact location of the leak or leaks is
• Reduce the steam pressure gradually located, the leaks may be repaired by replacing
• Open the drum air vent when the pressure the failed tube or by splicing in a new section of
drops below 2 kg/cm2 tube, conforming to relevant ASME code.
• Cool the boiler so as to examine the extent of An investigation of the tube failure is very
damage important so that the condition causing the tube
failure can be eliminated and future failures can
• Drain the boiler after cooling be prevented. This investigation should include
a careful visual inspection of the failed tube and
• If any tube rupture and bulging is observed
in some cases a lab analysis.It is recommended
rectify the same
that every effort be made to Þnd the cause of tube
• After the repairs conduct Hydrotest failures before operation is resumed.
Section C 48
Operation & Maintenance Manual
Interlock
Sr. No. Tag No. Service Alarm Alarm value
Details
Deaerator
1. PAH 105 HIGH 2 kg/cm.2 (g)
Pressure
Deaerator
2. PAL 105 LOW 1.5 kg/cm.2 (g)
Pressure
Deaerator
3. LAH 102 HIGH 60%
level
Deaerator
4. LAHH 102 HIGH HIGH 75%
level
Deaerator
5. LAL 102 LOW 40%
level
Deaerator
6. LALL 102 LOW LOW 30% BFWP TRIP
level
Steam drum
7. LAH 142 High 100 mmWC
level
Steam drum
8. LAHH 142 HIGH HIGH 200 mmWC
level
Steam drum -100mmWC
9. LAL 142 Low
level from NWL
Open Bypass
Steam drum -250 mmWC duct damper
10. LALL 142 Very Low
level from NWL
Trip ID Fan
Close Boiler
inlet damper &
11. ID 160A/B ID fan motor Trip simultaneously
open by pass
duct damper.
Super Heater
12. TAL 153 Low 480°C
steam temp.
Super Heater
13. TAH 153 High 500°C
steam temp.
ID Fan
14. PAH 178 discharge FG HIGH 40 mmWC
pressure
ID Fan
15. PAL 178 discharge FG LOW 30 mmWC
pressure
FG pr. at boiler
16. PAL 160 Low -70 mmWC
inlet
FG pr. at boiler
17. PAH 160 High -10 mmWC
inlet
Soot blower
18. PAL 147 Low 15 kg/cm.2 (g)
Pressure
Section C 49
Operation & Maintenance Manual
Interlock
Sr. No. Tag No. Service Alarm Alarm value
Details
Soot blower
19. PAH 147 High 23 kg/cm.2 (g)
pressure
DP across
20. DPH 118 High 0.1 kg/cm.2 (g)
BFWP strainer
DP across 0.15 kg/cm.2
21. DPHH 118 High high BFWP trip
BFWP strainer (g)
Note
• Interlock is indicated in BOLD
• All the values mentioned are preliminary may undergo revision at time of commissioning if
required.
Section C 50
Operation & Maintenance Manual
12 Troubleshooting Chart
Section C 51
Operation & Maintenance Manual
Section C 52
Operation & Maintenance Manual
Section C 53
Operation & Maintenance Manual
13 Water Quality Recommendations This chapter must be read in conjunction with the
following vendor manuals.
AIM • HP dosing system -
This chapter describes the standards for the boiler • Steam and Water analysis system
feed water and boiler water for corrosion and scale
free operation of the WHRB and for obtaining pure Suggested quality of boiler feed water (and
steam. Methods of control of boiler water are also attemperator water) fed to the WHRB is given in
explained. following table:
NOTE FEEDWATER
Section C 54
Operation & Maintenance Manual
Minor permissible contaminants present in the • Do not attempt to open the observation ports
WHRB feed water concentrate to high levels in in a working WHRB without observing proper
boiler water due to continuous evaporation in the safety procedure.
steam drum - evaporator circuits. Two controls
• For personal safety in handling hot valves,
are exercised on Boiler water to avoid corrosion
piping, oil guns etc. wear protective gloves
of WHRB tubes and the drum water - washed
while working around the WHRB.
surfaces. The controls are:
• Never enter drums, ducts, furnace etc., until
• Tri-sodium phosphate dozing to convert
the WHRB has been shut down and cooled.
the hardness producing insoluble calcium,
magnesium salts to soluble sodium salts which • When you need illumination for inspection,
can be drained by CBD and to maintain the only use low voltage extension cords with low
alkalinity levels of boiler water. The controls voltage bulbs with the cords properly earthed.
are described below. The power supply be from an earth leak circuit
breaker (ELCB)
NOTE The drum water quality should
be continuously monitored and suitable • Do not open or enter rotating equipment such
adjustment in blowdown to be made to as fans, unless it has been isolated and tagged
maintain the drum water as per above from power supply and the rotating equipment
recommendations. has come to a complete stop.
• Before removing manholes or ßanges in drum
14 Safety In WHRB House or pipeline, ensure that the drum/line has been
isolated and drained.
• It is expected that BHATIA ENERGY & STEEL
LTD will evolve a comprehensive safety • Do not use toxic ßuids like CTC for cleaning in
code for all operations in the plant. A few a conÞned space without adequate ventilation.
suggestions are listed below which can form • Install and strictly follow a system of permits
part of the plant safety code for the WHRB. and tagging for any maintenance or inspection
• Hazards of High pressure, high temperature work to be done by any person in the WHRB
steam, water must be recognized by the WHRB house.
operation and maintenance staff. • Operators trained in Fire Fighting, First AID,
• Fire extinguishing equipment should always be handling electric shocks etc may save lives
available around WHRB and property in an Emergency.
Section C 55
Operation & Maintenance Manual
Section D 56
Operation & Maintenance Manual
• Renewing the bonnet joint, and assembling the Objective of these inspections is to ensure that:
trim on the valve seat 1. The components are in trouble free condition.
• Renewing the gland packing 2. To carry out any minor repairs or adjustments
• Renewing the valve ßange joint, if necessary. which can be done with the boiler in service.
3. To plan for repair of such items, which cannot
3.2 Preventive Maintenance Program be attended when the boiler is in service,
for Spares during the next available shutdown.
4. To collect a database to determine optimum
It may be found that in the Þrst two years of service life of the systems and components
operation due to variations of site conditions, before maintenance if required.
some additional spares are also required. Action
has to initiate to procure such spares. The schedule can be expanded, curtailed or
modiÞed based on experience in the Þrst two
The prepared master plan for maintenance should years of operation.
be periodically reviewed during the Þrst three
years of the boiler operation.
4.1 Daily Checks
It may be found that due to varying site conditions,
the frequencies and quantum of work scheduled To be done once a day by the local operator during
as per vendor manuals are either too much or too his walkdown checks. Such walkdown checks are
less. Based on site experience, the frequencies to be encouraged to be done in each shift by the
and work schedules can be modiÞed local operators. Only those operational checks,
Section D 57
Operation & Maintenance Manual
Comparison of levels Compare the levels after verifying If there are serious discrepancies
indicated by local level gauge there are no leaks from valves, calibration of the remote level
with that of remote level glands etc. of the level gauge and indicators has to be planned
indicators in the control room indicators. Report discrepancies. immediately.
Traces of water, oil spots on Such spots are indicative of valve Maintenance to be planned
boiler ßoor, buck stay beams, leaks, instrument tapping leaks to eliminate the source either
boiler cladding etc. etc., Trace the source of leak. immediately or during next
planned shut down (depending on
the source and quantity of leak)
and accessibility for maintenance.
Lubricating oil levels of Fans, Check adequacy of oil level. Top up if required (immediately)
& feed pumps bearings,
If leakage through oil seals,
dosing pump gear box etc.
gaskets drain plugs etc. are
noticed plan for maintenance
during next planned shutdown.
Fans, BFW pumps dozing • Check bearing temperatures . If higher than normal bearing
pumps temperatures are noticed check
• Check for Vibration Levels
for cause proper oil level, correct
grade and quality of oil or grease,
abnormal sound or vibration.
If bearing temperatures are very
high, start the reserve equipment (
if avl.) and plan for a maintenance
checks .
If vibrations are above the
satisfactory limits. Check for
mechanical looseness and start
the reserve equipment ( if avl.)
and plan for a maintenance check.
Section D 58
Operation & Maintenance Manual
Boiler cladding, air duct or Check for hot spots Hot spots may be due to leakage
ßue gas duct. of ßue gas or hot air. Source of
leakage has to be located after
selective removal of insulation (to
be planned for the next planned
shutdown)
Section D 59
Operation & Maintenance Manual
Section D 60
Operation & Maintenance Manual
Dosing system Cleanliness of dosing tank, Clean dosing tank with normal
operation of pressure relief valve, water, Adjust relief valve ,if required
lubrication oil level in pump. Fill lubrication oil , if required
D P Manometer Choking of impulse tubes Liquid Clean impulse tube with air Keep
level in manometer liquid level at zero
Level switch for steam Close the steam out let valve and If switch or alarm is not working, do
drum water level very low gas by pass damper. Open blow the rectiÞcation work.
down valve and check for level
switch very low alarm.
Section D 61
Operation & Maintenance Manual
Section D 62
Operation & Maintenance Manual
• Steam impingement
• Refractory status
• Insulation
• Erosion
Inbed evaporator coils • Erosion
– Þre side • Corrosion
• Build up
• Blisters
• Sagging
• Over heating
• Sealing
• Cracks
• Steam impingement
• Refractory status
Super heater if provided. • Corrosion
(steam side) • Erosion
• Scale
• Pitting
• Metal reduction
• Flare cracking
• Deposits
Super heaters if provided. • Corrosion
(gas side) • Build up
• Sagging
• Over heating
• Fly ash erosion
• Sealing
• Supports
• Cracks
• Exp clearance
• Steam impingement
• Refractory status
• Insulation
Economiser • Corrosion
(water side) • Scale
• Pitting
Section D 63
Operation & Maintenance Manual
Section D 64
Operation & Maintenance Manual
Section D 65
Operation & Maintenance Manual
Section D 66
Operation & Maintenance Manual
5 Boiler Annual Maintenance and 5.2 Shutdown and Cooling the Boiler
Overhaul
1. Shutdown the boiler in a planned manner.
In addition to the check and inspections listed 2. Don’t force cool the boiler.
under preventive maintenance, the boiler requires 3. Open all access and inspection doors.
an annual shut down of about 10 to 15 days
for cleaning, inspection ad overhaul of boiler 5.3 Inspection after Cooling
pressure parts. The shut down period is restricted
to a minimum by deploying adequate resources. 1. Carry out a preliminary inspection after
If required, Field Engineering department of cooling to check cleanliness and sign of
Thermax Ltd. can assist the customer in carrying deposition on water wall panels and needs
out the boiler overhaul. any cleaning.
The annual shutdown is utilized for cleaning and 5.4 Drum Inspection
inspection of the pressure parts and to collect
data on the wear pattern of boiler, superheater 1. Open the access doors at either side of the
and economizer pressure parts. The shutdown drum.
opportunity is also utilized for overhaul of safety
2. Allow the drum to ventilate for about 8 hours.
valves, regulating and isolating valves and
If necessary a fan cooler can be Þtted over
components, which can not be attended when the
temporary stand to force air through the drum.
boiler is in service. (The valve overhauls need
not be done every year). 3. From the time the drum manholes are opened
till they are closed after inspection, the
area around the drum must be cordoned to
5.1 Planning Before Overhaul restrict entry only to speciÞcally authorized
personnel.
1. Prepare a list of jobs to be done during the
4. The names of persons who are entering the
overhaul based on earlier inspection reports
drum for inspection, along with tools they
and the jobs listed below.
carry must be entered in a register. Persons
2. Ensure availability of spares required for the coming out of the drum after inspection
proposed jobs. should be asked to account for the material
they carried into the drum. This precaution
3. Ensure tools, tackles, scaffolding materials is to prevent accidental dropping of foreign
required for the job. material through the water wall tubes, which
4. Ensure availability of manpower required may block water circulation through them and
for the job (Own sources, contract labour can cause tube failures.
etc) services of Thermax Ltd. is also 5. Carry out a preliminary inspection of the drum
available for carrying out annual overhauls to check for deposits on the water side of the
and inspections. drum.
Section D 67
Operation & Maintenance Manual
6. Using nylon brushes, the deposits (which are 2. Evidence of pitting / erosion / corrosion on
normally soft) are cleaned, collected on trays tube outer surfaces (exposed to the ßue gas
and disposed off outside the drum. Washing path)
down the deposits to the boiler tubes is not
3. Evidence of overheating (bulging of tubes,
recommended.
blue color of tubes, blisters, disturbed vertical
7. In case of excessive deposits, the chemist is alignment of panels)
asked to analyze the nature of the deposits.
Incase of excessive deposits, a review
of phosphate concentrations (higher than
5.6 Expansion Joints
10ppm) and boiler water quality control ( high
conductivity ?) may be made to reduce the Examine the expansion joints. Eroded / corroded
deposit in the next year of operation. parts can be patched by welding. When severe
erosion is noticed (after several years of service)
After cleaning the following examinations can be the expansion joints are to be replaced. Collapse
made. or stretching of the expansion joints is usually
due to forces exerted by the connecting ducts.
1. Examine the boiler drum metal for scale,
Readjustment of duct supports will solve the
pitting, corrosion and metal wastage. (Drum
problem and will assist the expansion joints to
thickness is measured at a few selected spots
regain their original dimensions.
using ultrasonic instruments and compared
to design thickness).
5.7 Insulation and Cladding
2. Inspect fastenings of the bafßes, cyclones,
and demisters to see that they are intact,
1. Verify insulation as per drawings and correct
without corrosion pitting or holes. Eroded or
wherever necessary.
corroded drum internals can be patched by
welding. No welding however is permitted on 2. Inspect cladding for damages due pitting,
the drum metal. The cyclones and demisters hotspots, dislocation etc. Repaired as
can be examined in position. They need not necessary.
be dismantled. Reasonable water tightness
of the bafßes and cyclones are to be ensured.
5.8 Other Equipment
3. Examine that feed water pipe is intact with
ßange connections tight and discharge exit Overhaul of fans, pumps, fuel feeders, control
correctly oriented. valves, actuators etc., is scheduled as per vendor
4. Examine that the continuous blow down pipe instructions and condition monitoring described
and dosing pipes is not plugged or corroded under preventive maintenance
their supports are normal, their holes have
been correctly oriented. 5.9 Feed & Boiler Water Conditioning
5. Examine that there are no cracks in the stub
welding s of the drum. 1. INTRODUCTION
After the inspection, clean the manhole seats The successful use of boiler is dependent on
and provide new gaskets. Sometimes the boiler proper water conditioning and treatment. The
inspector may like to inspect the steam drum. quality of water must have accurate for trouble
After this inspection and after verifying that all free operation of boiler.
men and material have been removed from the
The water as available to industry is not suitable
drum, close the manholes and bolt them tight.
for boiler use. A complete pre-treatment and
internal chemical treatment is necessary to make
5.5 Inspection of Screen, Primary raw water suitable for boiler feed.
& Secondary Superheaters,
The objective of the water treatment is:
Evaporators I/II & Economiser
• Eliminate scaling - deposition in boiler which
Check the above mentioned sections for any cause tube over heating leading to accidents.
1. Suspicion of abnormalities. If yes, consult • Control corrosion of boiler system, which cause
M/s THERMAX LTD. or a metallurgist for failure of boiler tubes, leading to unscheduled
necessary advice shutdowns.
Section D 68
Operation & Maintenance Manual
• Reduce carry over of water with steam, which is External treatment is used to remove such
the cause of deposition on super heater/turbine impurities.
blades, leading to the expensive failures.
• ClariÞcation - To remove suspended matters.
• To maintain peak boiler efÞciency by keeping
complete boiler water system clean. • Filtration - To remove residual turbidity
Section D 69
Operation & Maintenance Manual
good corrosion inhibitor. The recommended ammonia cyclohexylamine and Þlming amine is
concentration in boiler water is given in Table -1 recommended.
Note 1 : TSP will act as hardness conditioner, E. TURBINE / SUPERHEATER DEPOSITION
only when boiler pH is above 9.5 . Below 9.5 CONTROL:
pH TSP may cause hard scale formation of Ca3
(PO)2. Therefore, coordinated or congruent The solids in boiler feed water get concentrated
phosphate treatment is recommended. The water in boiler. The concentration of solids in boiler is
treatment experts can advise you right treatment decided blowdown and feed water quality. The
after studying your water quality and operation carryover of boiler water with steam depends on;
conditions. Mechanical Factors:
Thermax Chemicals can provide services for • Boiler load - Higher the load, lower is the steam
arriving at right chemical treatment for your boiler. purity
Chelant- Polymer treatment: • Water level in boiler - Higher the water level in
Hardness scales do not precipitate in presence of drum, lower is steam purity.
chelant like NTA/EDTA The chelant treatment is • Load Variation - Sudden increase in load
recommended when hardness ingress in boiler is reduce steam purity for short time.
experienced regularly.
• Separation efÞciency - Higher efÞciency, better
is steam purity.
Chemical Factors:
Excessive chelant dosing cause • TDS - Higher TDS in boiler, lower is steam
corrosion of boiler purity.
Hence balanced chelant program as • Total Alkalinity - Higher alkalinity as % of TDS
recommended by experts should be lower is steam purity
used.
• Organics - Higher the organic contamination,
Organic polymer conditioners are used to lower is steam purity.
prevent hardness scales. Such organic polymer
disperse scale forming compounds like CaCO3 • Foaming - Higher the foaming character of
& Ca(PO4)2 in colloidal form facilitating their water, Lower is steam purity.
removal through blow down. Polymer and The water carried over with steam due to
copolymer of acrylic, methacrylic, styrene maleic above reasons is exactly similar in quality to
acrylics are commonly used. Most of the polymers blow-down or boiler water. In superheater or in
are proprietary in nature and therefore dosage is turbines, water evaporates, leaving dissolved and
best recommended by manufacturer. suspended matter as scales or deposits.
D. FOULING CONTROL Thus severity of scaling and fouling of superheater
Suspended matter, oil/grease /oxygen & iron and turbine depends on boiler water quality and
salts commonly cause fouling inside the boiler. steam purity.
Most of the suspended matter and iron salts are Maintaining boiler water quality as per norms and
removed by external treatment. However due to maximum steam purity is the only way to prevent
mfg. of these equipment, contamination through deposition due to carryover of water with steam.
condensate and concentration in boiler cause Antifoam agents help to some extend to improve
fouling of boiler tubes. steam purity in case of excessive in boiler.
Similar to hardness scales, such foulants are F. SILICA DEPOSIT CONTROL:
poor conductor of heat. Thus fouling causes
overheating of tubes. Silica is volatile under high temperature
and pressure inside boiler. In turbines, the
Fouling can best be avoided by maintaining quality
evaporated silica precipitates during pressure
of feed water as per norms. In case of upsets
and temperature reduction and form hard scales.
or occasional contamination, polymeric disersent
help to prevent fouling due to turbidity and organic Maximum allowable concentration of silica
matter. Iron is picked up mostly in condensate depends on water analysis. Expert’s best decide
system due to corrosion of condensate line. In the maximum permissible concentration after
such case, condensate corrosion inhibitor like striding the operating parameters.
Section D 70
Operation & Maintenance Manual
Section D 71
Operation & Maintenance Manual
Section D 72
Operation & Maintenance Manual
all connections should be blanked or tightly unit to eliminate the danger of water freezing and
closed. subsequent damage to pressure parts.
5. A source of low-pressure nitrogen should be
connected at the steam drum to maintain 0.3 6.4 Nitrogen Blanket
to 0.6 Bar G to prevent air from entering the
unit during the storage period. Nitrogen can be introduced at the following
locations
1. Through the steam drum
2. Through the main steam line
The unit should be properly tagged The nitrogen required to seal the drainable
and the appropriate warning signs components may be supplied from a permanent
attached noting that the boiler is nitrogen system or portable tanks located near
stored under nitrogen pressure and the vent elevations. Due to differences in plant
that complete exhaustion of the layout, the owner should choose his own method
nitrogen must occur before anyone of piping the nitrogen, either from their permanent
enters the drum. Before entering system or from portable tanks, to the vent (or
drums test to prove that the oxygen drain) locations listed.
concentration is at least 19.5%.
Section D 73
Operation & Maintenance Manual
Section D 74
Operation & Maintenance Manual
Section D 75
Operation & Maintenance Manual
washing and drying, during the Þrst annual • It is recommended that every effort be made to
overhaul. The base value is the design thickness Þnd the cause of tube failures before operation
of the tubes. Subsequent measurements are is resumed.
made at the same locations, every alternate year.
• It should be ensured that, whenever a spool
The tube thickness survey provides useful data
piece is inserted in the failed zone, the weld
on corrosion / erosion rates and can alert the
joint needs to be of proper weld quality.
owner when serious loss of thickness is noticed.
• Free from excess weld penetration to avoid
Details with sketches and drawings will give any obstruction in the water / steam mixture
more clarity for analysis ßow inside the tube. Excess weld penetration
• Date of inspection can cause internal tube erosion and results in
tube failures.
• Tube no / Coil no.
• It is suggested to have all the joints are x-rayed
• Inner coil / Outer coil details and interpreted by qualiÞed / experienced
• Location. – RHS / LHS radiographer.
• Clock position.
7.1 Tube Failure Investigation /
• Reference points. Analysis Method
• Thickness including decimals. Investigation / analysis methodology is listed as
• Visual observations follows, which needs to be followed to Þnd the
actual root cause of the problems.
• Condition of studs.
Please fill up the enlcosed form duly filled and
the same may be sent to Thermax along with
7 Tube Failures tube sample for analysis.
Operating a boiler with a known tube leak is not Objectives of Failure Investigation
recommended. Steam or water escaping from a Boiler tube failures are the largest cause of forced
small leak can cut other tubes by impingement outages experienced by a utility. To avoid or
and set up a chain reaction of tube failures. Large minimize outages and the associated economic
leaks can be dangerous. The boiler water may be penalties, it is important to identify the mechanism
lost, the ignition may be lost, and the boiler casing and root cause of tube failures. Informed visual
may be damaged. inspection is often adequate for this purpose,
Small leaks can some times be detected by the however failure analysis involving detailed
loss of water in the cycle or system, a loss in boiler metallurgical investigation is necessary. Tube
water chemicals or by the noise made by the leak. failures may be due to overheating, corrosion,
If a leak is suspected the boiler should be shut erosion, fatigue, hydrogen damage etc. A failure
down as soon as possible by following normal shut investigation and subsequent analysis should
down procedures (If situation permits). determine the primary cause of a failure, and
based on determination, corrective action should
After the exact locations of the leak or leaks are be initiated that will prevent similar failures.
identiÞed, the leaks may be repaired by replacing
the failed tube or by splicing in a new section of Stages of Failure Analysis
tube, conÞrming to IBR code. Although the sequence is subject to variation,
depending upon the nature of a speciÞc failure, the
principal stages that comprise the investigation &
analysis of a failure are:
Section D 76
Operation & Maintenance Manual
5. Selection, identiÞcation, preservation, and/or The failed pressure part tube should not be
cleaning of all specimens. hammered, any mechanical impact should be
avoided.
6. Macroscopic examination and
analysis(fracture surfaces, secondary cracks, 3. Inspect the failed tube and record all Þndings
& other surface phenomena) on the same as well as its adjacent tubes.
7. Microscopic examination and analysis Carry out dimensional measurement of failed
tube and affected adjacent tubes.
8. Selection & preparation of metallographic
sections 4. Number mark the failed tube for its location,
ßue gas ßow, steam ßow with oil paint.
9. Examination and analysis of metallographic After completion of inspection, recording
sections and photography, cut the failed tube and
Collection of Background Operating affected adjacent tube, if any, with the help
Data of HACKSAW only. Gas cutting of the tubes
should be avoided as much as possible.
Boiler operating data just before & at the time The failed tube, keeping the failed portion
of a tube failure is very important as it will give in middle should be cut for total length of
information of the service conditions faced by the minimum 350 mm. Immediately after cutting
tube at the time of failure. This operating data the tube sample both the ends should be
should also be co-related with the past operation covered with plastic caps. While doing this
data & abnormalities if any should be taken care the internal or external scale of tube should
off. Water chemistry analysis, fuel analysis should not fall down.
also form an important part of this data. This data
& the metallurgical analysis will help us in true 5. The failed tube samples nicely packed in
sense to arrive at the exact cause of a tube failure. plastic bag / wooden case accompanying duly
Þlled format with water chemistry of boiler log
Investigation of Tube Failure in a sheets should be sent to H.O Pune.
Boiler
Removal of Failed Tube Sample
1. Study the boiler log sheet & water chemistry
record prior to tube failure and after tube 1. The tube sample should be cut with a
failure. Preserve the copies of these log hacksaw blade. Gas cutting should be
sheets. Record, if any abnormality noticed, avoided.
such as mal operation, malfunction, very 2. The sample should be cut approx. 8-10
high or low temp. / loads, ßuctuating loads, inches above & below the affected area.
sudden increase in load or temp., poor water
chemistry, start up vent crack open / close 3. & elevation should be marked on the tube
etc. etc. (if possible collect and send the sample.
water samples, internal scale from drum & 4. The direction of the ßuid ßow should be
tubes, external scale samples). marked on the tube sample.
2. After entering in boiler and before proceeding
5. Immediately after cutting the tube sample
to tube failure location inspect & record
both the ends should be covered with plastic
the condition of boiler and pressure parts
caps. While doing this the internal or external
without disturbing the evidence i.e. distortion
scale of tube should not fall down.
of pressure parts/coils, bulging of pressure
parts, scaling / lump formation on pressure The failed tube sample nicely packed in plastic
parts, blockage of ßue gas path, other / bag / wooden case accompanying duly Þlled
secondary failures etc. etc. In such case format as given below with water chemistry
taking photographs will help in great extent in of boiler log sheets should be sent to H.O for
analyzing of the tube failure, boiler problem. metallurgical investigations.
Section D 77
Operation & Maintenance Manual
DATA COLLECTION BY
THERMAX LIMITED
ENERGY BUILDING, D1 BLOCK, MIDC, R.D AGA ROAD,
CHINCHWAD, PUNE – 411 019 - INDIA
TELEPHONE 020 – 66126464
FAX : 020 – 27479048
WEB SITE : http://www.thermaxindia.com
EMAIL : Yashwant1@thermaxindia.com
Uumale@thermaxindia.com
DEAR CUSTOMER,
WE WANT TO HEAR FROM YOU,
WE STRIVE TO CONTINUOUSLY IMPROVE THE QUALITY AND PERFORMANCE OF OUR
PRODUCTS. WE WOULD LIKE TO HEAR FROM YOU, SHOULD YOU EXPERIENCE PROBLEMS
WITH OUR EQUIPMENT OR SHOULD YOU WANT TO SUGGEST IMPROVEMENTS,
JUST FILL IN THE INFORMATION NEEDED AT THE ENCLOSED FORMAT AND FAX / POST IT TO
OUR CUSTOMER SERVICE DEPARTMENT TO THE ABOVE MENTIONED ADDRESS.
KINDLY USE ADDITIONAL SHEETS IF REQUIRED.
PLEASE PROVIDE ADEQUATE INFORMATION / DRAWINGS REFERENCE / LOG SHEET
READINGS ETC FOR PROPER ANALYSIS & FEED BACK
WE WILL GLADLY REVIEW YOUR SUGGESTIONS AND REPLY TO YOU WITH IN A REASONABLE
TIME.
WE ARE AT YOUR SERVICES ALWAYS,
U.S. UMALE
DY GENERAL MANAGER (FIELD ENGG.)
Section D 78
Operation & Maintenance Manual
TELEPHONE NUMBER
FAX NUMBER
E-MAIL ADDRESS
CONTACT PERSON
OTHER DETAILS (IF ANY)
BOILER DETAILS
BOILER NUMBER :
DATE OF COMMISSIONING;
BOILER CAPACITY – MCR
STEAM PRESSURE
STEAM TEMPERATURE
FUEL FIRED
EQUIPMENT DETAILS
S.N PROBLEM OBSERVATIONS CORRECTIVE COMMENTS /
DETAILS ACTIONS TAKEN RECOMMENDATIONS
1.
2.
OTHER INFORMATION:
Section D 79
Operation & Maintenance Manual
Section D 80
Operation & Maintenance Manual
in accordance with the requirements of ASME • Completed welds are subject to hydrostatic test
section V. The standard for accepting /rejecting is
speciÞed in ASME section I
Base Material Filler Metal
P1 TO P1 Carbon Steel To Carbon Steel ER 70S.2 E7018
P3 TO P3 Carbon ½ Moly To Carbon ½ Moly ER80S.B2 E7018A1
P3 TO P3 ½ Cr ½ Moly To ½ Cr ½ Moly ER80S.B2 E8018B2L
P4 TO P4 1-1/4 Cr TO 1-1/4 Cr ER80S.B2 E8018B2L
P5 TO P5 2-1/4 Cr 1 Moly To 2-1/4 Cr 1 Moly ER90S.B3 E9018B3L
P8 TO P8 Stainless To Stainless ER308 ER308-16
2. Backing rings must not to be used in welding WELD REPAIR OF SMALL CRACKS IN TUBE
heat absorbing tubes carrying water or In the interest of saving time and cost, it is better
mixture of steam and water. to weld small cracks rather than replace a length
3. If a backing ring is not used, the Þrst pass of the tube.The crack must be ground out to form
of the weld must be made with inert gas-arc an acceptable welding groove. The groove should
or oxy acetylene. The weld passes may be continue well beyond the ends of the crack. Inert
completed by either process, or by a manual gas arc or oxy acetylene process must make the
metal arc. Þrst pass of the weld.
4. Pre heat or post heat is not required for Note
welding carbon steel furnace or boiler tubes.
1. This type of the repairs entails some risk.
5. Prior to welding, clean the tube ends to bright Internal deposits. Particularly copper, may
metal inside and outside for at least 40 mm exist under the crack which will result in
Section D 81
Operation & Maintenance Manual
damaging the parent and/or weld metal another similar failure could occur at or near
causing failure in a short period of time. the original crack.
2. Over-heating the tube may have caused the 4. Also the tube cannot be cleaned from inside
longitudinal crack. In this case, the tube and there is always a possibility internal
has swollen and the weld thickness reduced. deposits will contaminate the weld.
In the modern welded wall construction, it
is difÞcult to accurately measure the tube 9.3 Plugging Tubes in Drums &
diameter or circumference to detect the minor Headers
swelling. If visual indicates swelling and
reduction of wall thickness at the crack, a 1. Often after a tube failure, it is desirable to plug
complete replacement of the damaged tube the failed tube in the drum or header shell
length is the best solution. so the boiler may be returned to service with
3. A circumferential crack indicates a failure the least possible delay. It is recommended
due to excessive stress applied by expansion that the failed tube be replaced whenever
restriction, bending or fatigue; welding can possible in lieu of plugging. If the leak is
repair such cracks. However, unless the remote from the tube seats and accessible,
cause of failure is diagnosed and corrected, the faulty section of the tube should be cut
another similar failure could occur at or near out and replaced rather than plugging.
the original crack. 2. Water wall tubes (space tube) should be
4. Also the tube cannot be cleaned from inside replaced if possible and plugged only as a
and there is always a possibility internal last resort. The plugged tube must be free
deposits will contaminate the weld. to expand and distort with respect to the
adjacent tubes. Membrane tubes must be
repaired and not plugged.
9.2 Weld Repair Of Small Cracks in
Tube 3. When tubes are plugged, the old tube should
be removed from the boiler setting since it
In the interest of saving time and cost, it is better probably will burn off due to lack of cooling
to weld small cracks rather than replace a length and could become displaced and obstruct gas
of the tube.The crack must be ground out to form lanes, foul up soot blowers, be dangerous to
an acceptable welding groove. The groove should personnel after shutdown, and etc. If the tube
continue well beyond the ends of the crack. Inert is not removed from the setting, a deÞnite
gas arc or oxy acetylene process must make the hole must be punched or drilled in the tube
Þrst pass of the weld. to prevent a possible dangerous buildup of
pressure between the tube plugs.
Note
4. A expanded tube leaking at the seat should
1. This type of the repairs entails some risk.
be removed from its seat and
Internal deposits. Particularly copper, may
exist under the crack which will result in a. a new tube rolled in
damaging the parent and/or weld metal
b. a new short stub rolled in and plugged
causing failure in a short period of time.
c. the tube end seal welded to the shell or, if
2. Over-heating the tube may have caused the
the drum shell is internally counter bored,
longitudinal crack. In this case, the tube
a cylindrical plug must be installed and
has swollen and the weld thickness reduced.
seal welded to the drum shell.
In the modern welded wall construction, it
is difÞcult to accurately measure the tube Note: Point. (a) is the preferred Þx with Point.
diameter or circumference to detect the minor (c) the least preferred.
swelling. If visual indicates swelling and
5. Seal welding of tube ends, tapered plugs, or
reduction of wall thickness at the crack, a
cylindrical plugs to the shell should be done
complete replacement of the damaged tube
in such a manner as to minimize the heating
length is the best solution.
of adjacent tube seats, which may become
3. A circumferential crack indicates a failure loose. It is essential that the welding process
due to excessive stress applied by expansion should be as per standard procedure for
restriction, bending or fatigue; welding can carbon steel shells and tubes to be followed
repair such cracks. However, unless the very closely to ensure success. Deviations
cause of failure is diagnosed and corrected, from these parameters will normally result
Section D 82
Operation & Maintenance Manual
in unsatisfactory connections. The major a 2 ½" OD by 0.150-inch wall tube stub for a
welding parameters for shells or tubes 10% wall reduction is as follows
other than carbon steel may be obtained
from qualiÞed welding procedures. Ensure Measure Hold Dia 2.531
that welders are qualiÞed in accordance =
Measure Stub OD -2.500
with ASME Section IX and local provincial
=
requirements. They must also ensure that
the welding is done to the applicable qualiÞed 0.031 Clearance
weld procedure.It also to be ensured that 2.200
Measure Stub ID =
the proposed repair has been approved by
the Boiler Inspection Branch of the local Clearance = 0.031
jurisdiction. 2,231 Stub ID @
6. Machined tube stubs and plugs are used Contact
where the old tube can be removed from Stub ID @ Contact 2,231
its seat without seat damage and for new =
construction that is drilled for future addition
of tubes. The rolled-in tube stub extends into 10% of 0.150 x 2 = 0.030
the shell and a solid plug is installed and seal 2.261 Stub ID after
welded to the stub. These stubs and plugs expanding
are standardized to have only one tube stub
and one plug for each standard tube hole. 9. Plug all internal counter bored holes in the
7. Before rolling stubs in, they should be cleaned Þeld with the cylindrical plug when the tube
inside and outside with a wire brush, abrasive is still in the seat. Some counter bores may
paper, or a liquid cleaner until the metal is free be shallow enough that the tube ends are
of all foreign substances. In general, stubs exposed sufÞciently to permit seal welding to
do not require cleaning beyond the removal a tapered plug. 9.6 See Figure 04, page
of dirt, rust, scale or foreign material.The stub 84. If the tube seat is leaking, then the tube
seat (tube hole) should be similarly cleaned. If must either be seal welded to the drum shell
a liquid solvent is used to clean either the stub or the counter bore can be plugged with the
and/or tube hole, care must be taken to dry the cylindrical plug and seal welded per Figures
metal completely. Liquid trapped between the 04 and 12. It may be necessary to machine
stub and its seat prevents contact of the two the tube ends back in order to provide a seat
metal surfaces. for the cylindrical plug installation. See Figure
05 and Figure 06.
8. Before the expanding tool is inserted, the
inside of the stub should be lubricated 10. Figure 07 shows the details of this cylindrical
with a suitable compound. The compound plug and gives instruction for the speciÞc plug
selected should be water soluble to facilitate size desired.
cleanup. The rolling process should not be
11. Tapered plugs are used to plug existing tubes
rushed since heat generated during rolling is
where it is not practical to remove the tube
detrimental to the strength of the rolled joint.
from its seat and there is no internal counter
The tube stub is properly expanded when the
bore. These plugs must be tailor made for
wall thickness in the seat is reduced by 6 to
each tube diameter and tube wall thickness.
10 percent for generating tubes and 10 to 14
Figure 08 shows the details of this tapered
percent for other boiler tubes. The tube stub
plug and give instructions for a plug to Þt
wall reduction for thin shells should be less
tube diameters from 1-3/4" through 4 ½" OD
than that for thicker shells. This is to prevent
and any wall thickness. Figure 09 shows the
over rolling which could cause adjacent tube
arrangement of the tapered plug seal welded
seats to leak. Since the stub wall itself cannot
to the tube.
be measured after it is rolled in its seat, the
only alternative is to calculate the increase in 12. The plugs and seal welds described above
the stub ID that is necessary to prove that the are designed for the boiler pressure to be on
wall has in fact been reduced by the required the head (seal weld side) of the plug only. The
percentage. This depends upon the tube ¾ inch diameter by 1/8-inch thick button weld
seat ID (hole diameter), tube stub OD, the on the plug is to eliminate leakage through the
clearance between these two and also the “piping” which can occur at the center of some
stub wall. An example of this conversion for bar stock.
Section D 83
Operation & Maintenance Manual
13. Figure 10 shows a tube seal welded to the damage to the tube seats. If the tube seat
shell. This arrangement may be used when is damaged, it may be impossible to ever
the tube seat is leaking and it is not practical roll another tube in and make a tight seal.
to replace or remove the tube and use a rolled Gouging of the tube seat could also affect the
stub and plug. ligaments between tube holes and integrity of
the shell. Tubes can be removed from their
14. Economizer headers and superheater
seats without seat damage if the following
headers may be plugged as shown in Figure
procedures are carefully followed. With light-
11 & Figure 12 where external access is
gage tubes, it is often possible to cold crimp
available and the conditions shown on the
the tube end to loosen it in its seat, then drive
Þgures are met. If those conditions cannot be
or "jack" the tube out.
satisÞed, tube replacement is recommended.
In these two Þgures, the pressure is on the 2. When the tubes are too heavy for cold
internal end of the plug and the external crimping, the two-stage heating method may
strength weld restrains the plug. be used. Heat is applied to the inside of the
15. Plugged tubes that are below the horizontal tube end with a torch. Heat is Þrst applied for
centerline of the shell will not drain. a short period - not long enough for it to be
Therefore, after chemical cleaning it is transferred to the tube sheet. When the tube
necessary that the plug to be removed and the end cools, the joint will have loosened enough
stub swabbed out to remove the chemicals so that the second heat will not be transferred
in these stubs. The plug can then be welded readily to the tube sheet. The tube end can
back in or in some cases it will have been then be heated sufÞciently for crimping and
destroyed in the removal process and anew the tube can be pushed out of its seat. If
one will have to be installed. Care must be neither of these methods is applicable, the
taken in the plug removal process to not following methods may be employed.
damage or thin the tube stubs wall. 3. To remove light tube tubs, it is advisable to
cut grooves about 3/4 inch apart with a round
9.4 Replacement of Tube Section nose chisel. When the tongue (the metal
between the two grooves) is knocked free, the
Experienced personnel must do the replacement tube can be collapsed and removed.
of a section of failed tube.
4. To remove heavy gage tubes, the type of
1. grooving tool shown in Þgure 12 is used
to prepare the tongues without damage to
• The length of the replaced section should
the tube seat. It is used with a pneumatic
be a minimum of 12 inches
hammer, but it is necessary that the tool be
Usual practice is to cut out the defective suited to the tube thickness so that it will
section with an oxyacetylene torch, but it is cut the grooves as deep as possible and yet
preferable to use a hack saw or wafer disc. leave a minimum thickness of metal over
Care must be taken to prevent slag from the tube seat. In very heavy gage tubes, a
entering the tube. The ends are prepared for third groove is often cut, as nearly opposite
welding by grinding or with special tools the tongue as possible, so that less heavy
2. The root pass of the joint should be deposited pounding will be required to collapse the
with the gas tungsten arc process. stub. These latter two methods require that
the ßare on the end of the tube be crimped
A 3/32 - inch diameter shielded metal straight before starting, to cut the grooves for
arc-welding electrode is recommended for collapsing the tube. Of course, the seal weld
the remainder of the joint. around the end of any tube must be ground
The welding parameters for tubes may be or machined off before attempting to cut the
obtained from qualiÞed Welding Procedures. grooves for collapsing the tube. This must be
done carefully to prevent damage to the drum
shell.
9.5 Removing Tubes from Drums,
Headers & Tube Plates
9.6 Plugging of Tubes Drawings
1. The removal of tubes from their tube seats
must be done very carefully to prevent Attached Þgures 04 to 12
Section D 84
Operation & Maintenance Manual
Tapered plug application for shallow internal CTR’B Tube end must be exposed sufficiently for seal welding.
Figure 4
Section D 85
Operation & Maintenance Manual
Figure 5
Section D 86
Operation & Maintenance Manual
Figure 6
Section D 87
Operation & Maintenance Manual
Figure 7
Section D 88
Operation & Maintenance Manual
Figure 8
Section D 89
Operation & Maintenance Manual
Figure 9
Figure 10
Notes:
Section D 90
Operation & Maintenance Manual
Figure 11
Notes:
Section D 91
Operation & Maintenance Manual
Figure 12
Section D 92
Operation & Maintenance Manual
Section D 93
Operation & Maintenance Manual
cause the permanent hardness of the water and number denoting the degree of acidity or alkalinity
magnesium and they cannot be removed just by of a substance. It does not indicate the quantity
boiling because they form a hard scale on heating of acid or alkali in a solution as found by Þltration
surfaces. method. It is derived by measuring the amount of
hydrogen ion (H+) in grams per liter of solution.
10.3 Dissolved Gases The greater the amount of hydrogen ions present
in solution its acid reaction becomes stronger.
A) OXYGEN: Therefore, pure water is being neutral solution,
any solution producing more hydrogen ion than
It presents in surface water in dissolved form with pure water will be acidic and degree is governed
variable percentage depending upon the water by difference and other solution producing less
temperature and other solid contents in water. Its hydrogen ions than pure water will be alkaline and
presence is highly objectionable, as it is corrosive the degree is also governed by the difference.
to iron, zinc, brass and other metals. It causes
corrosion and pitting of water lines, boilers and THE ROLE OF pH IN CORROSION:
heat exchangers. Its effect is further accelerated The role of pH in corrosion of metals is extremely
at high temperature. important. The corrosion rate of iron in the
B) CARBON DIOXIDE: absence of oxygen is proportional to pH up to a
value of 9.6. At this point, hydrogen gas formation
The river water contains 50 ppm & well water and dissolving of iron practically stops. This is
contains 2-50 ppm of CO2. It also helps to the came pH produced by a saturated solution of
accelerate the corrosive action of oxygen. ferrous hydroxide Fe (OH) 2.
The other gases are H2S, CH4, N2 and many The Oxygen in the water unites with ferrous
others but their percentage are negligible hydroxide to form ferric hydroxide. This reaction
Therefore their effects are not discussed here. lowers pH of the solution and levels to stimulate
corrosion.
10.4 Other Materials Alkalinity adjustment and Þlm formation are
closely related. The pH value of feed water should
A) FREE MINERAL ACID:
be maintained greater than 9.6 to reduce the
Usually present as sulfuric or hydrochloric acid corrosion effects caused by the reason mentioned
and causes corrosion. The presence is required above. The required alkalinity of feed water is
by neutralization with alkalis. adjusted by adding soda ash caustic soda or
trisodium phosphate. The calcium hardness,
B) OIL:
alkalinity and pH are inter-related variables in
Generally the lubricating oil is carried with steam scale control. Calcium carbonate is one of the
into the condenser & thorough the feed system to most troublesome deposits responsible for scale
the boiler. It causes sludge, scale & foaming in formation.
boilers. Strainers and bafße separators generally
remove it. 10.6 Effects of Impurities
The effects of all the impurities present in the The major troubles caused by the feeding of
water are the scale formation on the different water of undesirable quality are scale formation,
parts of the boiler system and corrosion. The corrosion, foaming, caustic embrittlement,
scale formation reduces the heat transfer rates carry-over and priming. The details described
and clogs the ßow passage and endangers the below: -
life of the equipment by increasing the temp
above the safe limit. The corrosion phenomenon 1. SCALE FORMATION
reduces the life of the plant rapidly. Therefore it Feed water containing a group of impurities in
is absolutely necessary to reduce the impurities dissolved and suspended form ßows into the
below a safe limit for the proper working of the Boiler for continuos generation of Steam. With
power plant. conversion of water into steam in Boiler, solids
are left behind to concentrate the remaining
10.5 pH Value of the Water and its water. The scale formation tendency increases
Importance with the increase in temperature of feed water.
Because, the solubility of some salts (as calcium
The pH value of the feed water plays very sulphite) decreases with the increase in feed
important controlling the corrosion. pH is a water temperature. Calcium sulphite has solubility
Section D 94
Operation & Maintenance Manual
of 3200 ppm. at 15 Deg. C and it reduces to 55 to form carbonic acid and the cycle is repeated.
ppm. at 230 Deg. C and 27 ppm. At 320 Deg. C. Adding alkali solution to neutralize acids in
water and raise the PH value can minimize the
Scale formation takes place mainly due to salts
corrosion. The effect of CO2 is minimized by the
of calcium and magnesium. Sometimes, it is
addition of ammonia or neutralizing the amines in
cemented into a hard mass by Silica. Among all,
water. This is necessary because CO2 lowers the
calcium is the principal offender and particularly,
PH of the boiler feed water and dissolved solids
Calcium sulphate, magnesium sulphate and other
to leave the boiler.
Chlorides are sufÞciently soluble in water and are
not much troublesome. Sodium salts are highly The priming is a violent discharge of water with
soluble in water and are non-scale forming. steam from the boiler. It can be compared to the
The scale formation takes place mainly in feed pumping of water that frequently accompanies
water piping and Boiler Tubes. Its Þrst effect on rapid heating in a open vessel. In priming the
the piping system is to choke the ßow of water by water level in the boiler undergoes rapid and
reducing the ßow area and increases the pressure great changes and there are violent discharges
required to maintain the water delivery. Another of bursting bubbles. Therefore ‘sludge’ of boiler
effect of scale formation is to reduce the transfer water is thrown over with the steam.
of heat form the hot gases to water. Real dangers The priming is caused due to improper boiler
of the scale formation exist in radiant heat zone design, improper method of Þring, overloading,
where boiler tubes are directly exposed to the sudden load changing or a combination of these
combustion. The scale formation retards the ßow factors. The priming effect is reduced by installing
of heat and metal temperature increases. Even a steam puriÞer, lowering water level in the boiler
thin layer of scale in high heat zone can over-heat and maintains constant load on boilers.
the metal enough to rupture the tubes. The metal
tubes weakened due to over-heating yield to The foaming is the formation of small and
pressure providing a protrusion known as bag. stable bubbles throughout the boiler water. The
Such bag provides a pocket for the accumulation high percentage of dissolved solids, excessive
of sludge and scale, which eventually causes alkalinity and presence of oil in water are
failure. The over-heating of metal causes layer of responsible for foaming.
metal to separate and form a blister.
Boiler water solids are also carried over in the
2. CORROSION moisture mixed with steam even when there is
no indication of either priming or foaming. This
The corrosion is eating away process of boiler
is known as ‘carry-over’. The carry-over of boiler
metal. It causes deterioration & failure of the
water solids is partly a mechanical and partly a
equipment, eventually this cause for major repairs
chemical problem. The amount of suspended
or expensive shut -downs or replacements.
solids and alkalinity in the boiler water is also
The corrosion of boilers, economizers, feed important in addition to other reasons like boiler
water heaters & piping is caused by an acid or design, high water level, and overloading and
low PH in addition to the presence of dissolved ßuctuating loads on boiler.
oxygen & carbon dioxide in the boiler feed water.
The presence of oxygen is mostly responsible 3. CAUSTIC EMBRITTLEMENT
for corrosion among all other factors. The The caustic embrittlement is the weakening of
permissible limit of oxygen content varies with the boiler Steel as a result of inner crystalline cracks.
acidity of water. Generally it should not should This is caused by long exposure of boiler steel to
exceed 0.5 cc per liter .O2 generally enters combination of stress and highly alkaline water.
into closed system through make up condenser
leakage and condensate pump packing. The course of embrittlement takes place under
following condition:
CO2 is next to O2, which is responsible for
corrosion. The CO2 comes out of bicarbonates a) When boiler water contains free hydroxide,
on heating and combines with water to form weak alkalinity and some silica. It has been always
acids known as carbonic acid. This acid slowly found that the feed water was high in sodium
reacts with iron and other metals to form their bicarbonate, which broke down into sodium
bicarbonates. The newly formed bicarbonates of carbonate in the boiler and partially hydralized
metals decompose by heat once more and CO2 is as shown by the following reaction in case of
again liberated. This gas again unites with water embrittlement.
Section D 95
Operation & Maintenance Manual
Na2CO3 + HOH = CO2 + 2 NaOH agents to the feed water. The most practical
method of preventing caustic embrittlement is to
b) Slow leakage of boiler water through a joint or
regulate the chemical composition of the boiler
seam.
water. The obvious solution to embrittlement is
c) Boiler metal is highly stressed at the point of to eliminate all free NaOH from feed water by
leakage. This may be caused by faulty design and addition of Phosphates.
expansion etc.
The prevention of caustic embrittlement consists
of reducing the causticity or adding inhibiting
Section D 96
Operation & Maintenance Manual
Section E
1 Lubrication Schedule
This section holds the Lubrication Schedule for the Waste Heat Recovery Boiler on Coke Oven
Lubrication Schedule
Section E 97
Operation & Maintenance Manual
Volume 2 — Drawings
Volume 2 — Drawings 98
Operation & Maintenance Manual
List of Drawings
COMMON DRAWINGS FOR BOILER 1 & 2 WHRB
01. P & ID for Waste Heat Boiler (Coke Oven Plant)_D12-0WH-09484_4
02. P & ID for Deaerator & Pumping Ststion_D12-1WH-59879_3
03. Refractory for Boiler_R11-1WH-67044_0
DRAWINGS FOR BOILER NO. 1 ( PL 0501 )
04. G.A. of Boiler No.1_D11-0WH-09485_3
05. Pressure Part Assembly_D11-1WH-66536_1
06. Steam Drum_ P21-1WH-60701_0
07. Steam Drum Internals (Part I)_P21-1WH-60845_0
08. Steam Drum Internals (Part -II)_P21-1WH-60846_0
09. Steam Drum Internal Attachments_P21-1WH-60847_0
10. Detail of Superheater Coil 1A & 1B_PA1-1WH-59631_1
11. Detail of Superheater Coil II_PA2-1WH-59632_1
12. Assembly of Deaerator_W21-1WH-63955_1
DRAWINGS FOR BOILER NO. 2 ( PL 0502 )
13. General Arrangement of Boiler No..2_D11-0WH-09451_3
14..Pressure Part Assembly_D11-1WH-66537_1
15. Steam Drum_P21-1WH-61431_1
16. Steam Drum Internals (Part -I )_P21-1WH-61520_0
17. Steam Drum Internal (Part - II)_P21-1WH-61521_0
18. Detail of Superheater Coil IA & 1B_PA1-1WH-60871_1
19. Detail of Superheater Coil -II_PA2-1WH-60872_1
Volume 2 — Drawings 99
Operation & Maintenance Manual
Volume 3 — Drawings
E & I Specifications
Section 01
Instruments Hook Up Diagram
Section 02
2.1 Control Schematic Diagram
2.2 Control Narration
Section 03
DCS Input Output List
Section 04
Soot Blower Input Output List
Section 05
Logic Diagram for Drives
Section 06
Electrical System Required For Motor Selection
Section 07
SpeciÞcation for MOV Valve Actuator
Section 08
8.1 Electrical Load List
8.2 Power & Control Cable Schedule
Section 09
SpeciÞcation for PLC Based SB Panel
Section 10
10.1 Electrical Motor Selection for ID Fan Motor
10.2 Electrical Motor Selection for BFW Pump Motor
Section 11
11.1 Instruments Cable Schedule for Boiler 1
11.2 Instruments Cable Schedule for Boiler 2
Section 12
12.1 SpeciÞcation for Transmitters & Analysers
12.2 SpeciÞcation for Gauges & Switches
Section 13
Section 14
Section 15
Section 01
Pressure Transmitter — Emerson
O & M Manual
PRESSURE TRANSMITTERS (MODEL 3051)
Section 02
Temperature Transmitter — Emerson
O & M Manual
TEMPERATURE TRANSMITTERS (MODEL 644HA)
Section 03
Pressure Switch — Switzer Instruments
O & M Manual
Pressure Switch Manual
Section 04
4.1 Pressure Gauge — Gauges Bourdon
O & M Manual
Pressure Gauge Manual
Section 05
Power Cylinder — Keltron
O & M Manual
Damper Actuator - Keltron Manual
Section 06
Loop Power Indicator — Switzer Instruments
O & M Manual
Loop Power Indicator Manual Model (K5105 )
Section 07
I to P Converter — ABB
O & M Manual
I to P Converter — ABB_Manual
Section 08
8.1 Flow Nozzle — Starmech Controls
Data Sheets
Section 09
Control Valves— MIL
O & M Manual
MIL 41000 HEAVY DUTY BALANCED CAGE GUIDED CONTROL VALVES - MANUAL
MIL 21000 HEAVY DUTY BALANCED CAGE GUIDED CONTROL VALVES - MANUAL
MIL 37 –38 SPRING DIAPHRAGM PNEUMATIC ACTUATOR - MANUAL
8013 Valve Positioner Manual
400 L Positional Transmitter
496 Rotary Electric Switch
776 Air Lock Valve
Solenoid Valve Rotex
Data Sheet & Drawings
Control Valve Data Sheets
Section 10
Motorised Valve Actuator— Auma India Ltd.
Manual
Actuator Manual
MOV G. A. Drawings
Section 01
ID Fan - Flakt Woods
O & M Manual
Fan - Flakt_Manual
Drawings
General Arrangement Drawing of ID Fan
Section 02
BFW Pump — KSB Pumps
O & M Manual
Cover Page
Index of Manual
HDA Manual
Technical Appendix Sheets
Pump Data Sheets
Proposed Performance Curve
Drawings
1. General Arrangement Drawing for Pump
2. Cross Section Drawing for Pump
3. List of Components
4. P&I Diagram for Pump
5. P&I Diagram Part List
Section 03
LP / H.P Dosing System - Metapow Industries
O & M Manual
Dosing System Manual
Drawings
L.P. Dosing System Drawing
H.P. Dosing System Drawing
Section 04
4.1 Long Retractable Soot Blower - R.R. Techno
O & M Manual
LR Soot Blower Manual
Drawings
1. General Arrangement Drawing for LRSB for Boiler 1
O & M Manual
Rotary Soot Blower Manual
Drawings
1. General Arrangement Drawing for RSB for Boiler 1
2. General Arrangement Drawing for RSB for Boiler 2
Section 05
5.1 Motors— Siemens
Manual
Motor Manual
Data Sheets
Data Sheets for ID Fan Motor
Data Sheets for BFW Pump
Manual
ARC Valve Manual
Data Sheets
Data Sheets for ARC Valve
Section 01
Safety Valve – Tyco Sanmar
O & M Manual
HCI Model Manual
Drawing & Data sheet
Safety Valve Datasheet
Safety Valve Drawing
Section 02
Safety Relief Valves — Tyco Sanmar
O & M Manual
SAFETY VALVES (JOS — JLT Manual)
Data Sheet & Drawings
SpeciÞcation Sheets
Drawings
Section 03
Drum Level Gauge — Hitech
O & M Manual
Drum Level Gauge Manual
Drawings & Datasheet
Drum Level Gauge Drawings
Section 04
Level Gauge (Tubular ) – Chemtrol
O & M Manual
Tubular Level Gauge Manual
Drawings
Tubular Level Gauge Drawing
Section 05
Reflex Level Gauge — Chemtrols
O & M Manual
Reßex Level Gauge — Chemtrols_Manual
Drawings & Datasheet
Reßex Level Gauge - Chemtrol_Drawing
Section 06
Process Valve — KSB
O & M Manual
Process Valve Manual
Section 07
Process Valve — Xomox Sanmar
O & M Manual
Process Valve Manual
Section 08
Blow Down Valve — Levcon Instruments
O & M Manual
Blow Down Valve Manual
Section 09
9.1 Spring Hanger Support — Techno Industries
O & M Manual
Spring Hanger supports Manual
Support Drawing
Section 10
Damper - United Technomech Engineers Pvt. Ltd.
O & M Manual
Manual Guillotion Damper Manual
Pneumatic Guillotion Damper Manual
Pneumatic Operated Multilouvre Damper Manual
Drawings
Manual Guillotion Damper Drawing
Pneumatic Guillotion Damper Drawing
Pneumatic Operated Multilouvre Damper Drawing
Index
100% Feed Controller ................................... 19 Dry Storage Preservation .............................. 71
During Black - Out Procedure Condition ......... 43
A
Air Vent ........................................................ 22 E
Alarms and Interlocks ................................... 49 Economiser .................................................... 6
Alarms And Interlocks ................................... 35 Economizer .................................................. 19
Annual Maintenance Check Sheet ................. 62 Effects of Impurities ...................................... 94
Attemperator .............................................7, 23 Electrical power .............................................. 7
Automatic Control ......................................... 35 Emergency Procedures................................. 48
Emergency Shutdown Procedure................... 43
EMR Valve ................................................... 12
B Evaporator ................................................... 22
Blow Down Tank ............................................. 7 Evaporator / Convection Bank Tubes ............... 6
Boiler Annual Maintenance and Expansion Joints .......................................... 68
Overhaul .................................................... 67
Boiler Blowdown System ............................... 25
Boiler Feed Pump ......................................... 10 F
Boiler Feed Water Pumps ............................. 18 Failure Reporting Formats............................. 78
Boiler Lay Up Procedures.............................. 75 Feed & Boiler Water Conditioning .................. 68
Boiler Preservation Procedure ....................... 71 Feed Water Control Station ........................... 19
Boiler Pressure Part Description .................... 19 Feed Water Supply ....................................... 38
Boiler Protection & Interlock .......................... 35 Filling With Water.......................................... 39
Boiler Shutdown ........................................... 42 Flue Gas Data ................................................ 2
Boiler Start Up .............................................. 40 Flue gas Pressure drop proÞle: (for design
case)............................................................ 4
Flue Gas System .......................................... 31
C Flue gas Temperature proÞle : ( For Design
Checks Every Six Months.............................. 61 case)............................................................ 3
Checks Every Year ....................................... 61 Flue gas Velocity proÞle: (for design case) ......... 3
Chemical Dosing & Sampling System ............ 27 Forced Cooling ............................................. 44
Chemicals for Dosing ...................................... 9 Furnace and Boiler Tubes ............................. 81
Cold Start Up Procedure ............................... 40
Component Description................................. 16
Conditioned Based Maintenance ................... 57 G
Continuous Blow Down Control ..................... 26 Gauge Glass ........................................... 11, 13
Cooling of Shutdown WHRB & Its General Principle Of Weld Repairs................. 81
Preservation ............................................... 44
Cooling Water................................................. 8
H
High Water Level .......................................... 48
D Hot Startup Procedure .................................. 42
Daily Checks ................................................ 57 HP Dosing System........................................ 27
Daily Maintenance ........................................ 60 HP/LP Dosing System..................................... 9
Deaerator..................................................9, 16
Deaerator Steam ............................................ 8
Dissolved Gases .......................................... 94 I
Dissolved Salts and Minerals......................... 93 ID Fans .......................................................... 9
DM Water....................................................... 8 Inspection after Cooling ................................ 67
Do’s and Dont’s ............................................ 44 Inspection of Screen, Primary & Secondary
Drum Inspection ........................................... 67 Superheaters, Evaporators I/II &
Drum Level Control....................................... 21 Economiser ................................................ 68
Drum Safety Valve ........................................ 21 Instrument Air................................................. 8
113
Operation & Maintenance Manual
114
Operation & Maintenance Manual
115