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WELCOME
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MAINTENANCE OF WATER
WALLS, ECO,SH AND RHCOILS
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MAINTENANCE PLANNING
Maintenance Planning is callednerve center
Maintenance Planning enables tocarryout maintenance activities atthe appropriate time, method and
at minimum cost.
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Maintenance planning is deciding in
advance about
Jobs
Material
Tools
Machines
Labour Time required
Sequence
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Maintenance Planning
Lowers the cost of overhaul
Lowers maintenance time
Helps to utilize the overhaul period effectively
It eases the problems of purchase of criticalspares.
It plays a vital role in achieving higher production.
Prevents accidents.
Helps to solve complicated problems.
Helps to utilize the manpower and machines
effectively.
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HOW TO DECIDE OVERHAUL
PERIOD
Monsoon season ( July to Dec )
Previous overhaul period
Furnace conditions
Operational parameter
Spares position Major problems in Boiler, TG etc.
Which quarter to be utilized for O/H
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AGENCY FOR O/H
Past experience
License holders
Fixing pre-qualification requirements
Fixing responsibility
Safety to be followed
Statutory requirements
Minimum wages, PF etc. CIB approval, IBR approval
Inspection
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Criteria for maintenance planning
Commitment to grid
Periodicity between overhauls
Fuel availability
Engineering factors related
Rolling plan for five years
Target by CEA
Spares availability Cost optimization
Modernization / up gradation
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Types of maintenance
Preventive maintenance as per schedule
Break down maintenance
Short shut downs
Major overhauls
RLA / LEP / R & M
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Pressure Parts & Furnace
Coil cleaning
Furnace cleaning
Thickness survey
Header inspection
Inspection of De-superheaters
Window normalizing Sample cutting
Fixing of sleeves and baffles
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PREVENTIVE MAINTENANCE
- Physical Inspection During Cleaning
- Overheating
- Clamping
- Integrity of the Coils
- Erosion Pattern- Condition of Sleeves / Baffles
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THICKNESS SURVEY
Cleaning of Coils
Measuring of Thickness
Around 2500 to 3000 Spots Per Boiler
Preparation of Report
Comparing the Results With PreviousValues
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REMEDIAL ACTIONS
Analysis of erosion
Planning for procuring of spares &
consumables
Planning for execution
Thickness reduction up to 20%, putsleeves
More than 40% replacement
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Thickness Reduction -Causes
Ash erosion
Soot blowers
Due to failure of adjacent tubes
Corrosion
Rubbing with clamps / other coils Overheating/ bulging
Oxidation
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SAMPLE CUTTING
Presence of micro cracks
Fe3 O4 coating.
Pitting if any
Internal / external corrosion
Physical dimensions
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BREAK DOWN MAINTENANCE
INDICATIONS
- Noise at local
- More make up
- FG temperature variations
- Furnace vacuum
- ID fan loading- Drum level
- Difference between SF / WF
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Follow up of previoushistory
No. of outages
Location of failure
Nature of the failure
Probable causes
Remedial actions taken
Performance
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IDENTIFICATION
Local inspection
Shutting down of boiler Start one ID fan
Physical inspection at 10 ksc
Draining clearance
Forced cooling
Assess the damage Analyze the cause for the failure
Take prevent actions
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COILS
Reasons for punctures
Erosion
Weld defects
Rubbing
Corrosion
Overheating Faulty material
Steam soot blowers
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WATER WALLS
Erosion
Mechanical impact
Weld defects
Starvation
Blockage
More bends Faulty materials
Soot blowers
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REPLACEMENT
Sufficient cooling
Removal of insulation
Removal of WSB if required
Removal of refractory if required Identification of damaged tube
Level cutting ,edge preparation
Spool piece preparation
Positioning , alignment Welding
welding of clamps / fin
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GENERAL RULES FOR WELDING
REPAIRS
Carefully cut away fins and clamps to have
enough access for chamfering.
Remove the damage tube.
Clean the tube ends to bright metal inside and
outside for at least an inch.
Remove all scales and deposits
Tube edges shall be squared and chamfered.
Minimum length of the tube should be 150mm.
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Correct fit up shall be given
Maintain correct root gap. Both joints shall be tack welded.
First pass shall be done by TIG welding.
Complete the root, inter and final pass
welding.
Use correct polarity for TIG and SMAW.
Weld back fins and clamps.
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MAJOR OVERHAUL
Follow up of previous history
No. of outagesLocation of failure
Nature of the failure
Probable causes
Remedial actions taken
Performance
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Furnace & coil cleaning
Soot blowers are to be operated at periodic
intervals
During overhaul coils are to be cleaned
either by air, water or manual.
Acid cleaning if the internal deposits are
more.
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VISUAL INSPECTIONBulging
Erosion
Corrosion
Bowing
Overheating
Loss of integrity
Pitting
FoulingAlignment
Support system
Sleeves & Baffles
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DIMENSIONAL ANALYSIS
Thickness survey
OD measurement
Oxide scale measurement
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INSPECTION OF ORIFICE
At Eco inlet, 8 mm orifice is provided in
each coil.
In random ID of the orifice is to be checkedfor any blockage/ enlargement
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SAMPLE CUTTING
Cutting of sample tubes at various locations
to assess the internal conditions for
following checks. Surface cracks, pitting, erosion, deposits,
chemical analysis and microstructure
analysis.
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Fiberoscopic inspection
To inspect the internal conditions of the
components at intricate locations for
accumulation of debris, cracks, blockage,erosion, pitting and integrity.
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REPLICA
To find out the pattern of microstructure to
assess the degradation.
HARDNESS MEASUREMENT
Weld
HAZ
Parent metal
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DESUPERHEATERS
VISUAL INSPECTION
Bulging, overheating, bowing, support
system, orientation, conditions of NRV,filter and branch lines are to be checked.
Dimensional check
Measurements of OD and thickness checks
are to be carried out in random.
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Fiberoscopic inspection
To assess the internal conditions of DESHS
for
Shifting of thermal sleeve
Cracking of thermal sleeve
Missing / tilting / blockage of nozzles
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Fiberoscopic inspection
To assess the internal conditions of DESHS
for
Shifting of thermal sleeve
Cracking of thermal sleeve
Missing / tilting / blockage of nozzles
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INSPECTION OF SUPPORTS
Hanger support readings
Boiler expansion readings
Buck stay movements
Functioning of boiler guides
Roof supports are to be checked both in hot
and cold conditions
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Manholes
Rectify door clamps and hinges
Replace sealing rope and bricks
Provide refractory on doors
Ensure perfect closing
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Ways to protect boiler pressure parts
Metal temperature should be kept with inpermissible limits.
Raising and lowering of steam parametersshould be as per recommended pattern.
Tube leakage shall be attended at theearliest.
Maintain chemical regime properly.
Maintain drum level as recommended
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Do not by pass drum level and steam temperature
protections.
DESHs shall be maintained above saturation
temperature of spray water.
FGT Temperature between left and right side
should be kept minimum.
Use defect free injection valves.
Avoid entry of foreign materials in to the circuit.
Avoid material defect, material mix up, andwelding defect.
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Do proper heat treatment
Maintain tight inspection and quality
control.
Maintain optimum gas velocity Use quality fuel.
Maintain excess air as recommended.
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Allow strain free expansion
Insulation shall be carried out properly
Proper storage of spare tubes and
consumables.
Engage qualified highly skilled welders.
Maintain proper record for future reference.
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TYPES OF WELDING
- Butt
- Fillet
- Socket
- Build up
- Window
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REQUIREMEMNTS
JOINT DETAILS
BASE METAL DETAILS
FILLER METAL SELECTION SHIELDING GAS
POSITION OF THE JOINT
PREHEAT PWHT
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TECHNIQUE
STRINGER / WEAVE BEAD
SMAW, SAW, TIG etc.
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PREPARATORY WORKS
Welding machine
Cutting set
Gas cylinders
Welding rod
Tungsten rod
Supply points 24V/230V/415V
Safety accessories
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MATERIALS USED
SA 210 Gr-C
SA 106 Gr-B
SA 209 T 1
SA 213 T 11
SA 213 T 22
SA 213 T 91 X 20 Cr Mo V 121
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PRE HEATING
Preheating is raising the
temperature of the parent metal around
the area to be welded to the specifiedtemperature before welding and holding
the temperature until completion of
welding
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PURPOSE OF PRE HEATING
Prevents risk of cracking in the weld and
HAZ
Reduces rate of cooling
Reduces formation of residual stresses
Reduces distortion due to welding
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POST HEATING
Post heating is the heating the
weld metal below the transformation
range, holding for predetermined timeand reducing the temperature at a
controlled rate after completion of
welding.
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PURPOSES OF POST HEATING
Reduces HAZ hardness
Relieves residual stresses
Improves ductility
Improves toughness
Prevents premature cracks
STATUTORY
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STATUTORY
Central Boiler Board Controls Manufacturer
Fabricator
Erector
Repairer
Welder
Testing agency
Stress relieving agency
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IBR Certificates
Form III - A for pipes
III- B for tubes
III C for fittings
III D for pipes (Well known manufacturer)
III E for tubes
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STORAGE
Pipes & Tubes
Both ends shall be plugged
With identification marks ( Size & Material)
Electrodes
To be procure from reputed firms with validcertificates
To be stored in a dry room.
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REPLACEMENT PROCEDURE
Intimation of failure
Commencement report
Obtaining permission Rectification
ND testing
Completion reports Hydraulic test
Obtaining permission for light up
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THANK YOU