• Make it habit to reach all critical areas in such shut downs.

• Use binoculars to inspect unapproachable areas

• List , record all the findings at central place preferably with photographs

GOLDEN RULE FOR CFBC INSPECTION

Check that unwanted lug, supports, or any other things which is welded to pressure parts/fin is left out

Check the Kick out zone at every available opportunity for erosion

Check furnace water wall tube for any abnormal external scale or soot deposit.

Try to find out the cause and analyze this deposit wrt fuel feeding, combustion, SA air nozzle location etc. If the deposition appears to be abnormal, it is advisable to have a analysis of this deposit.

Analysis of same shall also provide the characteristics of fuel and its combustion related properties.

COMBUSTOR

Carry out thorough visual inspection of water wall tubes for swelling or thinning.

Try to inspect the tubes viewing from bottom to top with the help of torch light. This type of non conventional inspection will highlight the swelling spots clearly.

For thickness reduction, (either through corrosion or erosion mechanism) always inspect the areas near fuel feeding, burner and Secondary Air Nozzle insertion location into furnace.

Carry out Thickness gauging from reliable thickness meter at predetermined spot to have a record of the same and to have a comparison at later date for monitoring the thickness reduction, if any.

COMBUSTOR

Open the end cap of bottom header to check the internal sludge /scale deposition. This will also reflect Water chemistry management.

If there is considerable amount of deposition, it is advisable to cut a tube sample and check the extent of internal scaling.

The extent of scaling shall be the guideline for need of chemical or acid cleaning. It is also recommended to carry out the internal scale analysis (if required) to determine the major constituents in it; accordingly water chemistry can be monitored.

Inspect and repair the refractory damage as per the specified engineering practices only.

COMBUSTOR

Check and take corrective action for Fuel Spreader parts projected inside furnace for wear and tear. Overheating and distortion of such items can not be ruled out.

Any welding done directly with the tubes for supporting or refractory holding purpose may require Dye Penetrant testing. This testing will be able to detect crack development.

Check the tightness of buck-stay bolt

FURNACECOMBUSTOR

WING WALL

INSPECT AND RECORD VERTICALITY AND ALIGNMENT

CHECK ALL REFRACTORY INTACT..PARTICULARLY BOTTOM AND OUTER MOST COILS FACING DIRECT GASES

DO HAVE A LOOK AT THE AREA OF INTERSECTION OF WINGWALL AND COMBUSTOR FOR ANY RUBBING

TARGET WALL

CHECK ALL REFRACTORY INTACT..

PARTICULARLY AREAS FACING DIRECT FLUE GAS VELOCITY

COMPACT SEPERATOR & VORTEX FINDER

CHECK ALL REFRACTORY INTACT..

HAVE A LOOK ON VORTEX FINDER, ITS SHAPE AND ITSSUPPORTING AND LOCKING ARRANGEMENT

C O D

CHECK ALL REFRACTORY INTACT..PARTICULARLY BOTTOM AND OUTER MOST COILS FACING DIRECT GASES

HAVE A LOOK ON THE ASH ACCUMULATION IN COD

CHECK THE AREA BENEATH ASH.

Check tubes visually for specific soot deposition pattern. Remember, any particular pattern of soot deposition on super hater coils both vertically as well as horizontally shall reflect the combustion and flue gas pattern.

Check super heater tubes for any overheating or thinning symptoms. Although Thickness gauging can reflect the eroded portion, but for overheating /swelling damage, it is useful to make a Gauge equivalent to OD of the tubes and then check. This is the fast and useful way to detect the swelling, if any.

SUPERHEATERS

Check the gap between bend of superheater coil and convection cage . Record it and cross check it with the specified gap. Any abnormality in this, shall reflect the expansion, supporting related problem exclusively for that loop.

Check specifically the superheater sealing area for any rubbing or gaps at the Cage intersection point. Gap observed at this area shall cause flue gas leakage during operation and rubbing may lead to failure at later date.

Pitching of coil and supporting arrangement need to be seen and recorded for comparison at later date.

It is advisable to take photograph of superheater coils in position prior to boiler light. This will help in comparing the misalignment at later stage

SUPERHEATERS

Measure and record thickness of bends at accessible area as well as of tubes at extreme ends.

Check thoroughly the tubes connected to inlet and outlet headers at the intersection of side casing. This area is more prone of erosion.

Do not forget to have a glance of tubes in the vicinity of soot blowers.

Have a look of the supports for any abnormal rubbing symptoms on the coils.

Check areas in vicinity of soot blowers for steam erosion

ECONOMIZERS

One may wonder for a fact that a boiler during start of season performs well in terms of ID fan loading and power consumption of ID and FD fan both, while at the fag end of season, to achieve rated boiler loading become difficult due to constraint in Fan capacity specifically ID fan.

Very often the root cause lies in leakages in APH tubes.

Any leakage in APH tube will cause air ingress in flue gas path, thus increasing the volume of gas to be handled by ID fan. On the other hand, quantity of FD or SA air has to be increased for combustion to compensate the leak.

AIR HEATERS

Hence APH tubes need to be checked for leakage and chokage. In both cases, boiler operation will not be smooth.

Smoke test shall predict the leakage, while visual inspection will reflect the chokage aspect.

There are also chances of leakage through Tube sheet, which would be very difficult to check, hence non- conventional method need to be adopted for checking the same.

AIR HEATERS

Check the internal surface of drum for integrity of protective magnetite layer.

Inspect the surface of drum for carryover symptoms.

If carry over signs are present then check the baffles or internals that were supposed to be seal welded.

Check the condition of mesh/demister pad and other internals for deposits and wear/ tear.

Depending upon water chemistry being followed, there will be a need to check Feed water pipe, Blow down pipe and chemical dosing pipe for corrosion and thickness loss.

STEAM DRUM

Carry over symptom

Con

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Drum Internal surfaces

Check condition of Air Nozzle ( PIG TAIL, RETURN LEG) for erosion

Check the condition of supports (specifically hanger supports).

Inspect ID fan impeller, suction cone and related ducting for any abnormal wear/tear.

Have a look of expansion joints provided in main flue gas passage/ Air . There is every possibility of leakage/ingress through the gaps.

Do not forget to attend the areas of leakages which were identified during operation of boiler

OTHER INSPECTION AREAS

Check condition DCF chain , its pin and other locking washers

Inspect Stoker from Catenary for any abnormal wear of Grate bar and damage of Supporting beam, chain and other parts.

Check condition, Integrity and ash deposition on guide baffle plate provided in various ducts.

Check Ducts & Hoppers for any distortion, overheating or refractory damage ( if provided)

Check & Mark the leakage area from furnace, ducts.

Check condition of Grit Interceptor pipes for erosion or damage

Check Deaerator Spray nozzles, condenser & Tray supporting arrangement