Training material for air preheater

Air Preheater
Mongduong 2 560 MW Coal Fired Power Plant
January, 2014
Environmental Plant Engineering Team
TRAINING MANUAL

1
Table of Contents
3. Technical Specification
2. Description
5. Operating
4. Commissioning
6. Maintenance
1. Overview

2
1. Overview
Air Preheater Design
 The Tri-sector is a single Ljungstrom-type Air Preheater designed to perform the
function of two separate Air Preheaters. It provides both primary air and secondary air
on large coal-fired boiler.
What does an Air Preheater do ?
 The Ljungstrom-type Air Preheater absorbs waste heat from flue gas, then transfers
this heat to incoming cold air by means of continuously rotating heat transfer
elements of specially formed metal plates.
 The of rotor slowly revolves the mass of elements alternately through the gas and
air passages, heat is absorbed by element surface passing through the hot gas
stream ; then, as these same surface are carried through the air stream, they release
stored up heat thus greatly increasing the temperature of the incoming combustion air.

3
1. Overview
Plant Overview
Air Preheater
Air Preheater
SCR

4
1. Overview
Plant Overview
Boiler SWFGD StackGGH
FDF
FDF
Mill
SCR GAH
PAF
PAF
ESP IDF

5
1. Overview
Air Preheater P&ID
Hot Sector Plate Drive Unit
Gas
Air
GAH
Support
Bearing
Guide
Bearing
Rotor
Drive Unit
M
A/M
Stationary Washing Device
Stationary Washing Device
M
Retractable Soot Blower
Cooling Water(in)
Cooling Water(out)
Compressed Air (from Air Motor Piping)
Sealing Air (from Pri. Air Duct)
From Boiler Steam Header
Extinguishing Water
Washing Water
Boiler
EP
Air in
(Primary)
Air in
(Secondary)
Gas in
Oil Circulation Unit
Primary Air Fan Forced Draft Fan
Extinguish Water Device
M
M
M
Actuator
Actuator
Actuator
M From Boiler Steam Header

6
1. Overview
Typical Tri-sector Air Preheater
Primary
Air Inlet
Secondary
Air Inlet
Gas Outlet
Gas Intlet
Primary
Air Outlet Secondary
Air Outlet

8
1. Overview
Erection Procedure-1

9
1. Overview
Erection Procedure-2

10
2. Description - Rotor assembly
 The rotor assembly provides the structure for holding the heat transfer surface
(heating element) within air preheater.
 The rotor consists of the rotor post attached with 24 diaphragm which are rotor
reinforced by stay plates arranged in concentric alignment.
DIAPHRAGM Rotor
Rotor Post
Rotor

11
Rotor

12
 The heating element is packed in three layers in the 24 sectors which the rotor
evenly in the circumferential direction.
 The heating element is held in a steel container called basket.
 The cold layer is to be removed by side removal it through the basket removal door
locked on the rotor housing.
The hot and intermediate layer is to be removed by lifting it through upper side duct
by using the provisionally installed mono rail and hoist.
 The baskets are reversible for extended service life.
Heating Element with Basket

13
Hot and Intermediate
Heating Element (DU type)
Cold
Heating Element (NF type)

14

15
 Located between the gas path and the air path, the rotor seal serves to reduce the
migration of gas and air which is caused by pressure differential existing between the
two flows.
 The rotor seal is made up of radial seal, rotor post seal, by-pass seal and axial seal.
These are mounted to the rotor diaphragm, rotor shell, rotor post and rotor housing.
 The individual seal members are set at predetermined clearance against the moving
parts so that a minimum gap is retained despite the thermal distortion of those parts
during operation. By reducing air leak to a minimum, the best performance is obtained
from air preheater.
 Radial seals at hot and cold end of the rotor are attached to the diaphragm plates of
the rotor.
 By-pass seals are attached to the rotor housing.
 Axial seals attached to the rotor and positioned axially along the cylindrical shell of
rotor.
 Post seals are attached to the end of the rotor post.
Rotor Seal
2. Description – Rotor Seal

16
Rotor Seal

17
Rotor Seal

18
Rotor Setting Chart

19
Rotor Setting Chart – Upper Radial Seal Setting

20
 The rotor drive unit is responsible for the rotation of the rotor containing heating
element through the gas and air streams. As the pinion gear (mounted on the low
speed output shaft) rotates, it engages the rotor pin rack mounted on the outside
diameter of the rotor shell, causing the rotor to turn. The rotor RPM is 1.02.
 The rotor drive unit normally uses the main drive (AC electrical motor) to drive the
rotor. It switches to the auxiliary air drive in case of emergency such as electric motor
failure or loss of power supply. Switching to the air motor is automatically
accomplished by solenoid valve.
 The auxiliary air drive motor is also used during performance of off-load water
washing or maintenance work such as heating element replacement.
Rotor Drive Unit
2. Description – Rotor Drive Unit

21
Rotor Drive Unit

22
 AC Electric motor : This motor is the primary power input to the speed reducer.
 Speed reducer : Transforms the high-speed rotation of the electric motor ouput into
the low-speed rotation of the pinion gear.
 Pinion Gear : The pinion gear is connected to the output shaft of speed reducer and
engages the rotor pin rack.
 Air Motor : This is connected to a secondary high-speed shaft input of the speed
reducer by a coupling and an over-running clutch.
Rotor Drive Unit Main components

23

24
2. Description – Rotor Support Bearing

25
 The support bearing is installed in the bearing housing located in the lower center of
air preheater.
 It takes on the whole weight of the rotor revolving with full load of the heating
element via the trunnion, as well as the radial load created by the pressure differential
between the flue gas and combustion air ducts.
 The support bearing assembly is lubricated by an oil bath and will be naturally
cooled due to low temperature area of air preheater support side.
Rotor Support Bearing
2. Description – Rotor Support Bearing

26
2. Description – Rotor Guide Bearing

27
2. Description – Rotor Guide Bearing
 The guide bearing is installed in the bearing housing located in the upper center
section of air preheater.
 It keeps the rotor in alignment with vertical rotational center line via the trunnion
and is responsible for supporting the radial loads generated by the pressure
differential between the flue gas and combustion air ducts.
 The bearing assembly is lubricated by oil bath to provide continuous operation and
maintains lube oil temperature at a suitable range by water-cooled lubricating oil
circulating system.
Rotor Guide Bearing

28
2. Description – Lube Oil Circulation Unit

29
 The air preheater is furnished with a Lube Oil Circulation Unit at the guide bearings.
 A thermocouple is provided in guide bearing housing for control of the pump motor.
 The purpose of this unit is to circulate the oil for cooling when the temperature of
the oil in the guide bearing housings reaches a predetermined set point.
 When the oil temperature reaches the set point, the pump motor is started. After the
temperature of the oil falls below the set point, the pump motor is stopped.
Lube Oil Circulation Unit
2. Description – Lube Oil Circulation Unit

30
2. Description – Retractable Sootblower
RETRACTABLE
SOOTBLOWER
LANCE TRAVEL LENGTH

31
2. Description – Retractable Sootblower
 To keep the heat transfer surface clean, the Air Preheater is equipped with two part
retractable type sootblowers.
 One sootblower is located in the flue gas outlet side of the air preheater to control
deposit build up on the “cold end” heating elements. An additional sootblower may be
installed in the gas inlet side of the air preheater for cleaning the “hot end” heating
elements.
 Recommended blowing frequency (for initial operation of the air preheater)
 Normal operation
- Cold end : Once every eight (8) hours – until optimum schedule is developed
- Hot end : Once every twenty-four (24) hours – until optimum schedule is developed.
 Start-up on oil
- Cold end : Continuously until stable firing conditions exist.
Retractable Sootblower

32
2. Description – Water Washing Device
 The stationary water washing device is run when Air Preheater is shut down for regular
inspection or maintenance service. It directs low-pressure water sprays at the heating
surface to remove deposits that did not give in to cleaning by the sootblowers.
The washing device consist of two (2) stationary multi-nozzle pipes. One is located in
each the gas inlet and gas outlet of the air preheater.
Water Washing Device

33
2. Description – Water Washing Device

34
2. Description – Fire Fighting System
 Thermocouple - The gas-outlet thermocouples measure the temperature of the
combustion gas leaving the air preheater, at various radial locations in the gas-outlet lower
center section side.
 Fire extinguishing device - The fire extinguishing device is designed to extinguish a fire
in it’s incipient state before the soot fire develops into a metal fire the fire. This device is
installed on gas inlet side of Air Preheater and consist of pipe and spray nozzles.
 When the fire alarm is activated, take a proper action (such as the operation of the fire
extinguishing device) while monitoring the fire by the MIS alarm and simultaneously by
firsthand survey through the gas air heater's inspection ports.
Fire Fighting System (Fire detecting and extinguishing)
FDS
(MIS) (High temp Alarm)
(High rate Alarm)
(T/C open Alarm)
1
2
3
4
5
6
7
(Fire Alarm)
(Open Alarm)
T/C (Thermocouple)
(Analog In : 7 points)
(Digital Out : 2 points)

35
2. Description – Fire Fighting System

36
2. Description – No Rotation Detector
 This detector is designed to monitor electrically whether the rotor of air preheater is
normally rotating and to send out a signal when the rotation is abnormal.
 The device consists of a target and proximity switch.
 The target and proximity switch, which is coupled with the support bearing housing
cover of air preheater, catches the rotation of rotor.
 Air preheater no rotation alarm signal shall be generated when the rotor speed is below
than 0.1 RPM. (Air preheater normal speed is 1.07 rpm.)
No Rotation Detector

37
2. Description – No Rotation Detector
SUPPORT
BEARING HOUSING
PROXIMITY SWITCH
TARGET
BRACKET
LOWER CENTER SECTION
SUPPORT BEARING HOUSING
PROXIMITY SWITCH

38
2. Description – Hot Sector Plate Drive Unit
 The actuator connected outward to the sector plate moves the sector plates down to the
position(s) pre-set with the boiler operation control signal (boiler load and gas inlet
temperature of air preheater), which results in reducing hot end radial leakage.
Hot Sector Plate Drive Unit

39
2. Description – Hot Sector Plate Drive Unit

40
Air Preheater Design Data

41
Heating element and Basket
Rotor Seal

42
Proper

43
Recommendable Lubricants-1

44
Recommendable Lubricants-2

45
4. Commissioning
Pre-Start up checks
 Final Check-out
Verify that all dimensional inspection and final check-out record sheets included in ERECTION
MANUAL (T08035-DM01-61-HLD-470001) 5.0 Inspection Documentation have been properly
documented.
 Lubrication
Check the oil levels in the guide and support bearing housings, all gear boxes, air motors, air
motor lubricators, etc. are at the correct fill level.
 Rotor Inspection
Check to insure that there is no construction materials lying on the heating elements, between
the heating elements and the sector plates, or between the rotor and housing shell.
 Rotor seals
Verify that all the post, radial, axial and by-pass seals have been set to the clearances as
shown on the Seal clearance table drawing.
 Guards and Covers
Check the rotor drive unit and auxiliary equipment drives to insure that all shaft guards and
access covers are in place and secure.

46
4. Commissioning
Pre-Start up checks
 Plant Utilities
Check to insure all water, steam and service air connections have been made in accordance
with the drawings and specifications for the air preheater and auxiliary equipment.
 Electrical Connections
Check all electrical circuits serving the air preheater and its auxiliary equipment to insure that
they are connected correctly and protected with thermal relays or fuses in MCC.

47
4. Commissioning
Cold Run Inspection
After the pre-start up checks are satisfied, the air preheater is ready for a cold-run
operational inspection.
A. Start the auxiliary drive air motor by opening the service air hand valve.
Observe the rotor for unobstructed operation while making one complete revolution.
B. Continue to use the auxiliary drive motor until satisfactory operation for on
revolution is achieved, then isolate the auxiliary drive motor.
C. Energize the main drive AC motor and run the rotor for one hour at normal speed.
Check the main drive motor temperature.
D. Test the automatic operation of the air motor solenoid valve upon power loss to the
main drive motor.
E. Override the thermocouples located at the guide bearings to start the oil circulation
unit. Allow to run for one hour checking for proper pump operation and oil leaks.

48
5. Operating
Start-Up
After all the pre-startup checks and the cold-run inspections have been completed in
accordance with the instructions, the air preheater is ready for commercial operation.
The following operation sequence should be used to place the air preheater into service
before emitting hot flue gas through the Air Preheater.
The operation shall be automatically controlled by the DCS.
A. Activate the Fire Detection system.
B. Start the air preheater's main drive motor before the forced and induced daft fans are
started.
C. Start the forced and induced draft fans.
D. When firing the boiler on oil, start cold end sootblowing the air preheater continously
during start-up an auxiliary blowing medium until stable boiler conditions are
achieved and the normal sootblowing medium is available.
E. Energize the guide bearing oil circulation unit.
F. Energize the hot sector plate drive unit
G. After normal sootblowing medium is available, activate the air preheater sootblower
sequence.

49
5. Operating
Normal Shutdown
The following sequence should be used to remove the air preheater from service.
A. De-energize the hot sector plate drive unit.
B. Activate the air preheater cold end sootblower cycle to remove any deposits.
C. Keep the FD & ID fans running during the cleaning operation so that the air preheater
temperature will decrease more rapidly.
D. Deactivate the air preheater sootblowers.
E. De-energize the air preheater’s Fire Detection System.
F. Keep the rotor turning and the fans operating until the gas inlet temperature at the
preheater inlet drops below 150°C. This will evenly distribute the effects of thermal
distortion, over the entire rotor structure.
G. Shut down the FD & ID fans.
H. De-energize the rotor drive unit.
I. Close the manual valve to stop service air to the auxiliary air drive motor.
J. Deactivate the guide bearing oil circulation unit.

50
6. Maintenance
1) Inspection Procedure During Operation
As daily inspection is carried out during operation of the unit, its positions and items
are limited for the reasons such as safety. However, it is a thing indispensable to grasp
if Air Preheater is normal or abnormal. "Daily & weekly inspection program during the
Air Preheater operation" has been made as regards the following positions for items of
inspection.
Component Parts Extent of Inspection
Contents of Inspection Procedure Check
Rotor drive unit
Electric motor
Temperature Feeling with hand
Vibration Feeling with hand
Electric current(with ammeter)
Watch for more than minute
or DCIS
Bearings (sound of rotation) Sound stick
Speed reducer
Temperature Feeling with hand
Vibration Feeling with hand
Sound from bearing Sound stick
Rotating sound from bearing Sound stick
Oil level & oil leak Visual check
Others
Oil level of lubricator Visual check
Sound from pinion gears Sound stick
Gas leak Visual check
 Daily Inspection check list during the Air Prehearter operation

51
6. Maintenance
Rotor bearing Guide & Support bearing
Rotating sound from bearing Sound stick
Oil level & oil leak Visual check
Position of dust seal ring Visual check
Gas leak Visual check
Oil Temperature Visual check or local panel
Droppage of trunnion bolt locking bars
Visual check from outside
Rotor proper
General
Draft loss DCIS
Temperature of fluids DCIS
Rotor seal Sliding sound of seals Sound stick
Soot blower
Upper & Lower side soot
blower
Blowing travel Visual check
Blowing pressure Visual check
Leak from wall box joint Visual check
Looseness of clamps Visual check
Leak from individual sections Visual check
Oil circulation unit Guide bearing
Oil & Water leak Visual check
Oil discharge pressure Visual check
Oil temp.(Inlet & Outlet) Visual check
Cooling water flow Visual check
Water temp.(Inlet & Outlet) Visual check
Component Parts Extent of Inspection
Contents of Inspection Procedure Check
Electric
Motor
Hot sector plate dr
ive unit
Vibration Visual check
Actuator
Vibration Visual check
Sector plate lifting rod Indicator Visual check
Gas leak.(Bellow) Visual check
Sound from sector plate Sound stick

52
6. Maintenance
2) Procedure of Periodical Inspection
Summarized “Check list of periodical inspection” are inspection required items
established through our experiences to be observed during regular annual inspection.
However, the principle is that you are required to pay sufficient attention to every
equipment and accessory of air preheater unit.
 Check list of periodical inspection
Component parts Extent of inspection Contents of inspection
Interval
RemarksEvery
Year
Every
2 years
Every
4 years
Rotor post
1. Weld joints between the header and the stub dia
phragm
▪ Visual check
▪ Color check
●
●
If irregularity is found in
any of the weld joints be
tween the header and th
e stub diaphragm, perfor
m color check on all the
joints.
Rotor
1. Main diaphragm
▪ Visual check
▪ Thickness measurement
●
●
2. Stub diaphragm
▪ Visual check
●
●
3. Weld joints between the main diaphragm and th
e stub diaphragm
▪ Visual check
▪ Color check
●
●
4. Rotor shell
▪ Visual check
●
●
5. Stay plate
▪ Visual check
●
●
6. T-bar
▪ Degree of roundness
●
●
7. Rotor angle ▪ Visual check ●

53
6. Maintenance
Pin rack assembly
1. Pin rack ass’y ▪ Visual check ●
2. Gog pins
▪ Degree of roundness
▪ Pitch
▪ Wear measurement
●
●
●
3. Pin rack ▪ Degree of parallelism ●
4. Weld joint of holding block
▪ Visual check
▪ Color check
●
●
Interval
RemarksEvery
Year
Every
2 years
Every
4 years
Rotor trunnion
1. Trunnion ▪ Visual check ●
2. Trunnion bolts ▪ Hammering ●
3. Locking bars ▪ Visual check ●
Guide & Support b
earing
1. Inner race, outer race, roller
▪ Visual and feeling check wit
h hand
●
2. Bearing retainer ▪ Hammering ●
3. Housing ▪ Visual check and oil leak ●
4. Packing for bearing housing ▪ Visual check ●
5. Lubricating oil
▪ Sampling
▪ Replacement
●
●
6. Packing for air seal cover ▪ Visual check ●
Proper
1. Weld joint of flange plate
▪ Visual check
●
●
2. Partition plate
▪ Visual check
●
●
Carry out inspection ever
y 2 years after the air pre
heater has been in servic
e for 10 years.
3. Housing panel
▪ Visual check
●
●
4. Connecting plate
▪ Visual check
●
●
5. Packing for adjuster bolt of sector plate ▪ Visual check ●

54
6. Maintenance
Interval
Remarks
Every
year
Every
2 years
Every
4 years
Heating element and ba
skets
1. Hot and intermediate and cold
end heating element and bas
ket for at least one sector eac
h.
▪ Visual check
▪ Weight measurement
▪ Looseness
●
●
●
●
Carry out overhaul check a
t least 3 baskets of the sect
or every 2 years after 5 yea
rs service, but before 5 yea
rs, if the damage is found i
n any of the element, overh
aul should be done.
Rotor seal
1. Post seal ▪ Set bolt ▪ Measurement of thickness and clearance
▪ Hammering ●
●
2. Radial seal ▪ Set bolt ▪ Measurement of thickness and clearance
▪ Hammering ●
●
3. By pass seal ▪ Set bolt ▪ Measurement of thickness and clearance
▪ Hammering ●
●
4. Axial seal ▪ Set bolt ▪ Measurement of thickness and clearance
▪ Hammering ●
●
5. Static seal ▪ Set bolt ▪ Visual check or thickness measurement
▪ Hammering ●
●
6. Sealing segment ▪ Visual check ●
7. Sector plate ▪ Degree of parallelism measurement ●
8. Axial seal plate ▪ Degree of parallelism measurement ●

55
6. Maintenance
Interval
Remarks
Every year
Every 2 yea
rs
Every 4 year
s
Rotor drive unit
1. Speed reducer
▪ Fitting between the shaft, gear
and bearing ▪ Bearing, oil seal
and grease
▪ Overhaul
▪ Visual check and measurement
▪ Visual check and functional test
●
●
●
High speed shaft
1. Over running clutch
▪ Spring
▪ Bearing
▪ Fitting
▪ Overhaul
▪ Visual check
▪ Measurement
●
●
●
●
3. Pinion gear
▪ Visual check and measurement between th
e pinion gear and the cog pins
●
Measure the degree of e
ngagement
4. Air motor
▪ Bearing, oil seal
▪ Rotor blade
▪ Overhaul
▪ Visual check and functional test ●
●
●
5. Carbon ring ▪ Visual check and functional test ●
6. Oil pump ▪ Visual check and functional test ●
7. Coupling bolts ▪ Visual check and functional test ●
8. Lubricating oil ▪ Replacement ●

56
6. Maintenance
Interval
Remarks
Every year
Every 2 ye
ars
Every 4 ye
ars
Oil circulation system
1. Oil pump
▪ Coupling cushion
▪ Oil leak from piping
▪ Overhaul
▪ Visual check
●
●
●
●
2. Oil filter
▪ Element, O-ring
▪ Overhaul
●
●
3. Oil cooler
▪ Gasket
▪ Cooling water leak from piping
▪ Overhaul
▪ Visual check
●
●
●
4. Relief valve ▪ Visual check and functional test ●
Hot sector plate drive unit
1. Actuator
▪ Overhaul
●
●
2. Screw jack
▪ Overhaul
●
●
3. Pillow block
▪ Bearing, packing
▪ Overhaul
●
●
4. Chain & flexible coupling
▪ Packing, oil seal,
▪ bolts
▪ Overhaul
●
●
●

57
6. Maintenance
Interval
Remarks
Every year
Every 2 yea
rs
Every 4 ye
ars
Hot sector plate drive unti
5. Sector plate lifting rod
▪ Rod and pin
▪ Bellows
▪ Overhaul
▪ Visual check
●
●
●
6. Sector plate position indicator
▪ Position indicator
▪ Overhaul
▪ Visual check and position check
●
●
Retractable soot blower
1. Speed reducer
▪ Bearing and oil seal
▪ Overhaul
●
●
2. Feed tube
▪ Packing
▪ Gasket
▪ Overhaul
●
●
●
3. Lance tube
▪ Gasket
▪ Overhaul
●
●
4. Poppet valve
▪ Stem packing
▪ Spring
▪ Overhaul
●
●
●
6. Nozzle ▪ Visual check and plugging check ●
2. Nozzle tube
▪ Overhaul
▪ Measurement of thickness
●
●

58
6. Maintenance
Interval
RemarksEvery
year
Every 2
years
Every 4
years
Water washing device
1. Nozzle
▪ Overhaul
▪ Visual check and plugging check
●
●
2. Nozzle tube
▪ Overhaul
●
●
Fir detecting system
1. Nozzle
▪ Overhaul
▪ Visual check and plugging check
●
●
2. Nozzle tube
▪ Overhaul
●
●
3. Fire detector
▪ Overhaul
●
●
No rotation detector syste
m
1. Sensor
▪ Overhaul
●
●
2. Targets ▪ Visual check ●
3. Clearance
▪ Checking of clearance between the proximi
ty switch sensor and the targets
▪ Overhaul
▪ Measurement of clearance
●
●
Other 1. Packing for man hole and door ▪ Visual check and functional test ●
2. Herme seal, etc. ▪ Application ●
3. Molyton, etc. ▪ Application ●

59
END OF DOCUMENT
Thanks for your listening !
Name : Min-Seok, Shim
phone : +82-55-278-4211
e-mail : minseok.shim@doosan.com

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