1. Bow in headres -for membrane panels 1mm/M (min) / 8mm (Max)
2. Bow in headers - for other panels 1mm/M ( min) /10 mm (Max)
3. Headers scarfing line -for membrane panels 2mm (Max)
4. Headers scarfing line -for other panels 4mm (Max)
5. Membrane Panel width + 2mm to -5 mm
6. Diagonal difference of Panel (D1-D2) 10mm (Max)
7. Verticality of Downcomer lines 1mm/M , 5 mm (Max)
8. Bow in seperator /collector tanks 1mm/M, 10 mm (Max).
9. Headers -elevation and spacing + / - 3 mm.
10. Furnace alignment ( Front and back Pass) width & depth + 10 mm or -15mm
11. --------------- Do------------------------ Diagonal difference 20 mm (Max)
12. Fire ball angle -Permissible limit + /- 1 degree
13. Pitch of water wall screen tubes & Back Pass front wall tubes + /- 3mm
14. Pitch of Screen Tubes +/- 10mm
15. LTRH Coil and Pitch between centre line of side wall end to coil assembly + /- 10mm
16. LTRH- Pitch coils + /- 10 mm.
17. LTRH Coil and Pitch between centre line of front /rear wall to coils end +/- 20 mm.
18. Spacing between RH hanger tubes + /- 3mm.
19. Platen Super heaters coil and pitch between centre line of side
water wall and end coil assembly. + / - 25 mm.
20. Platen Super heaters - Pitch of coils + /- 25 mm.
21. Final Super heaters - coil and pitch between centre line of side
water wall and end coil assembly. +/- 10 mm.
22. Final Super Heaters - Pitch of coils + /- 10 mm.
23. Economiser- coil and pitch between centre line of side
backpass wall and end coil assembly. +/- 10 mm.
24. Economiser- pitch of coils +/- 10 mm.
25. Economiser -clearance between centre line of back pass front/
rear wall and coil ends. +/- 20 mm.
26. Re -heaters - coil and pitch between centre line of side water wall
and coil assembly. +/- 10 mm.
27. Re-heaters - Pitch of coils + / - 10 mm.
In sub critical boiler where drum erection is involved instead of seperator an collector
following field quality checks are made.
1. Drum suspension U rod twist between limbs 10 mm max.
2. Disposition of Drum axis centre line of ceiling Girder 1mm/M max +/- 5 mm
3. Spacing of washer plate w.r.t. longitudinal axis and drum axis 1mm/M max +/- 3mm
4.Diagonal difference between washer plate locations max 5 mm.
5.Elevation of Drum +/- 5mm
6. Elevation of drum -cummulative max 8mm
7. Spacing of Drum axis w.r.t to centre line of ceiling girders. 1mm/M max +/- 5 mm
8. Axial shifting of drum w.r.t longitudinal axis 5 mm max
9. Verticality of drum suspension U rod 10 mm max.
Beisdes above checks for pressure parts there are certain checks to be carried out and
recorded like above. It is to be noted that all Pressure parts item vessels , pipes and tubes
etc .are coming under the perview of Boiler directorate and their acceptance is must and
binding to all. Therefore all the records are to be maintained accordingly.
- Inspection authority's stamp to be checked in every material and if possible take the copy
of the stamp . Also match with the paper certificate.
- All the pressure part items like vessel , pipes , coils ,panels etc are to be cleaned from outside
and inside. Sponge ball test to be carried with compressed specially for coils , panels etc .
- For major items like drum , vessel etc level marking to be done accurately for future reference.
For sub critical Boiler all the reference of headers start from drum positioning.
- Alignment of headers , coils ,panels are to recorded.
Platen super heater coils and Final super heater coils are visible through water wall panel
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I would like to know the effect of deviations in coil (super heaters,reheaters economisers etc) alignments, spacings in THERMAL POWER PLANT BOILERS
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