Final Inspection of 135 TPH FBC Boiler - 27 F

7/31/2019 Final Inspection of 135 TPH FBC Boiler - 27 F

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27 February, 2011

REPORT ON BOILER CONSTRUCTION AUDIT 135 TPH AFBC

This is the final inspection report of our construction audit. The boiler erection work was almostcomplete. Only steam line and feed line erection work was under progress. The insulation work was

under progress.

Observations

1. It is requested that the reports given by undersigned and our engineer shall be read together to seethat the boiler is fit for firing.

2. In this visit the irregularities seen in boiler are brought out and presented in annexure.3. The ESP was inspected this time. One of the important inspection parameter to be done is the

uniformity of gap between collecting and emitting electrodes. A gauge is generally used by theinspector. This shall be carried out the Thermax inspector. Uniformity puts a limitation of fieldvoltage.

4. Pre-commissioning should include mass flushing of boiler to get rid of all ash and coal dust whichhad gone in to the boiler.

5. The spring hangers shall be loaded and commissioned prior to firing of boiler.6. The refractory height is seen to have reduced this time as per the advice from VESPL. It is advised

to complete the hook welding so that any time the refractory can be applied easily.7. Many observations are on insulation. These shall be taken care of.8. Scrap removal and boiler cleaning shall be done well. If the work is started immediately it can be

done better. The dense phase system shall not be connected until the ESP scrap is removed.

K.K.Parthiban


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Photo 1: The thermocouple carrying pipe shall be sealed. During operation bed ash may startspilling from the refractory cracks.

Photo 2: The FD ducting inside is seen here with scrap. Scrap cleaning is to be done at all

places..


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Photo 3: A pipe lying inside the FD duct to windbox.

Photo 4: The Expansion joint in hot air duct to windbox is seen fitted with asbestos rope. These joints are to be seal welded from inside of the duct to prevent air leakage.


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Photo 5: Scrap seen in APH air outlet duct to windbox just below the APH outlet duct.

Photo 6: The compartment damper setting is improper. As such the damper is too small. In thisflow area is covered by the dummy plate here. The plate shall be trimmed to the maximumpossible.


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Photo 7: The compartment dampers were found to close improperly. This can give problemduring compartment operation.

Photo 8: The compartment dampers (FD) shall be seal welded. Air gap is seen in all FDcompartment dampers.


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Photo 9: The inlet cone at PA fan suction shall be trimmed off. This is seen in both PA fans.

Photo 10: The PA fan suction cone is seen with scrap rods. These shall be removed.


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Photo 11: The PA duct tapping from the FD duct is seen improperly taken. The area isobstructed by the extra plate. These shall be trimmed.

Photo 12: The scrap welded to PA duct shall be removed and insulation shall be properly done.


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Photo 13: The PA fan needs guillotine type isolation gate to prevent reverse rotation of thestand by fan.

Photo 14: The fuel piping to furnace is seen with an improperly welded piping. These lead topipe erosion. Whenever the replacement is done, the pipe shall be with a properly set joint.


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Photo 15: The air duct to sparger pipes shall be insulated to reduce heat loss to surrounding.

Photo 16: It is seen that the waterwall bottom header is not properly covered with insulationmattress. To reduce heat loss, the insulation shall be extended.


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Photo 17: The bottom header shall be provided with insulation. In addition expansion joint shallbe provided with a hood to prevent damage due to heat radiation.

Photo 18: The seal box at waterwall shall be filled with refractory. The seal plates are to bewelded to header with a minimum weld size of 3 mm.


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Photo 19: The windbox duct is seen to be on a temporary support. The insulation work iscompleted already.

Photo 20: This is one of the ways to support a hot duct. The roller pipe is retained in the guidechannel. This photo is from a Thermax boiler.


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Photo 21: The sealbox at waterwall inspection door. Bottom seal plate shall be erected and sealwelded.

Photo 22: All inspection doors shall be provided with handle above to enable easy entry in to theduct / furnace / economiser / APH / duct / SH area.


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Photo 23: The spring hanger shall be first loaded by turning the turn buckle. Once the hanger

rod is loaded, the locknuts shall be released.


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Photo 24: The seal boxes shall be covered by a 40 mm thk insulation to prevent heat radiation.We can see a left over area of waterwall without insulation here.

Photo 25: The coal nozzle cap to bed coil gap was less than design. This was pointed out earliervisit. No modifications were carried out as it called for lowering the hopper and sparger headers,which was a major work. The bed coils have to be protected by phoscast castable. It is advisedto lower the edge thermocouples to a level of 50 mm above air nozzle top. This is to ensureoperators drains off settling heavier particles as the bottom thermocouple goes dead.


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Photo 26: The bed material feed chute to seal box shall be seal welded.

Photo 27: The bunker vertical beams in hoppers shall be closed with bottom beams with tie

plates.


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Photo 28: The economiser supports are seen in locked condition. These shall be released.

Photo 29: The insulation at APH is seen to be poor. Rain water should not enter in to insulation.Once the insulation is trenched with water, more fuel is required to evaporate the same.


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Photo 30: The economiser inlet duct is provided with extensive support system inside. It is seenthat the support to casing is with fit up weld only. Stitch welding is required here.

Photo 31: The APH top approach platform column is seen here in open condition. Plate shall beprovided here.


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Photo 32: This column is also seen without top plate.

Photo 33: It is seen that a separate penthouse is provided for superheater headers. However theSH inlet header is left out. There is no sealbox provided. Hence there will be ash insidepenthouse. The SH headers and DESH are at different temperatures. If insulation is providedonly for the penthouse, there will be radiation heat dissipation to each other and there can be a10 15 deg C drop in main steam temperature.


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Photo 36: The roller rod direction for steam drum is wrongly oriented. However the drum maystill expand as thermal forces are very high. The steam drum base shall be provided withexpansion guides to prevent rotation of drum axis.

Photo 37: The temporary hanger rods of steam drum can be removed / loosened for free thermalexpansion in horizontal plane.


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Photo 38: The steam drum is seen with dust cakes. The SH coils may be also in similarcondition. This is due to delayed commissioning after the hydro test. It is advised to carryoutmass flushing by fire hose through top header hand holes so that coils are flushed out well. Thebottom header hand holes are also to be open for cleaning. Otherwise we may experience sometube failures post commissioning. The flushing is recommended for SH coils as well from mainsteam outlet side.

Photo 39: The water level gauge is seen in accessible for viewing the level. This shall becorrected. The level gauge except the gauge glass shall be covered with insulation to avoid

failure of glass & to show the right level.


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Photo 44: The economiser outlet duct is seen with depressions. This sort of defect is seen ismany sites. Slopped duct roof is ideal for this. Or else sealant has to be applied at joints toprevent rain water entry. The casing may otherwise last for 5 6 years only. The manhole dooris not required here.

Photo 45: The gas baffle plate has to extend up to casing covering all the economiser bends.This is at the bottom of economiser bank.


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Photo 46: The same defect as in earlier photo is seen on left side as well.

Photo 47: The expansion joints at ESP outlet duct shall be covered with insulation & cladding.

Un-insulated expansion joints would be the first to fail in any plant.


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Photo 48: The ID fan inlet duct expansion joints shall be insulated.

Photo 49: The ID fan delivery duct insulation joint is not insulated.


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Photo 50: The Uninsulated expansion joints generally fail like this in 2-3 years depending on

fuel moisture / fuel sulfur.

Photo 51: Lifting hook found inside ID fan. Scrap removal needs to be perfect in order to avoidany dame to men & machine.


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Photo 52: The transport angle at multi louver damper shall be welded to casing. Or else it maybe removed.

Photo 53: The spacer channel / angle used at ID fan suction duct shall be removed and all

fasteners shall be provided at the flanges.


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Photo 54 & 55: non uniform pitch is seen between collecting electrodes and emitting electrodesare seen inside ESP. This shall be rectified. A gauge is used by the ESP inspector to check theuniformity of electrode spacing.


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Photo 56: The Inside top of penthouse is to be insulated. This is to prevent condensation of fluegas inside.

Photo 57: It is seen that the rain water directly enters in to ESP insulation. It is necessary that acanopy is welded to top chequered plate to prevent rain water entering insulation.


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Photo 58: This clipping is from the ESP insulation drawing provided by Thermax. Penthouse isto be insulated as per detail D10. Ridge is to be provided to prevent drain water entry as perdetail D11. Insulation shall be laid over all casing stiffeners as per detail D10. But the abovewere all missed out.

Photo 59: The rigid frame connecting ID fan discharge duct and ID fan casing shall be removed.


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Photo 60: This is bed zone & waterwall bottom zone refractory. This is to be provided withexpansion gap of 4 mm at 500 x 500 square pattern. Now refractory would crack in service andcreate haphazard cracks. Some places refractory may spall off.

Photo 61: The rpm of the drag chain may be reviewed. Drag chain takes the coal with asurcharge over the height of drag plates. Wear rate of the chain is a function of square of thedrag chain speed.


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Photo 62: One spring support is pending erection on left side of the boiler. This is for thedowncomer.

Photo 63: The metal scrap shall be removed from the primary SH bank.


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Photo 64: The fin to fin welding is pending at waterwall outlet duct. This was pointed out duringthe previous visit. Before welding, the fabric shall be removed. Otherwise it may burn off.

Photo 65: The economiser tube to casing gap is more than the tube to tube gap. Due to this the

end economiser coils would erode. 50 mm Gas baffle is required to prevent gas laning.


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Photo 66: The gas baffle provided for protection of bends is not installed properly. All the tubebends are to be protected.

Photo 67: The insulation is improper. Stiffeners are being left out. This makes the casing toremain hotter.


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Photo 68: This the top tube sheet to air inlet duct joint. It is doubtful whether we have a properseal weld done here or not. Water droplets are seen inside the APH. This area shall be checkedduring air leak test.

Photo 69: The intermediate door in APH- air side is not accessible. Approach platform isrequired.


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Photo 70: The APH casing stiffener should be covered with insulation to prevent condensationdamage. The inspection door shall be provided with platform.

Photo 71: The APH outlet duct welding to lower APH block upper tube sheet shall be checked

for air ingress.


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Photo 72: The Eco to APH duct expansion joint shall be covered with insulation and cladding toprevent condensation damage.

Photo 73: The buckstays shall be corrected as per drawing. The expansion of waterwall shallnot be restricted.


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Photo 74: The Deaerator shall be provided with freedom for thermal expansion.

Photo 75: The scrap inside the deaerator storage tank shall be removed.


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Photo 76: It is seen that the steam can take a direct path to the top of tower. There has to betortuous path for steam so that the water to steam contact will be good.

Photo 77: The radial ribs shall be welded to the central pipe for rigidity.


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Photo 79: The scrap inside the water chamber of tower shall be removed.

Photo 80: What is seen here is also a Thermax ESP with double door system incasing to preventcondensation damage to ESP at doors. Also we can see the sealant between cladding sheets to

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Final Inspection of 135 TPH FBC Boiler - 27 F

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