REPAIR PROCEDURE OF FIRE TUBE BOILERS

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TUBE TO TUBE SHEET LEAKAGE

  • Check visually and mark the area where leakage is observed.
  • Remove the water from boiler
  • Carry Out Dry Penetrant  * (D.P) Examination Of Weld and about 25 To 30 mm Inside Circumferences of tube.
  • If visual Examination or D.P Test confirms leakage is through tube, it means tubes is cracked and it must be replaced
  • If the leakage is through weld mark the area from where leakage is observed
  • Remove the defective weld completely
  • Carry out D P test to confirm defect is removed completely
  • Clean the area thoroughly and preheat the area to 100 deg minimum.
  • Weld root pass using # E7018 @ 3.15 mm electrodes only
  • After root pass carry out d.p test to confirm sound root
  • Clean the area and again preheat to 100 Deg C. minimum
  • Complete the welding using E 7018  @ 3.15 mm electrode
  • Ensure cleaning between subsequent passes
  • Carry out the D P test to confirm the weld
  • Conduct the hydro test to confirm no leakage occurs

Alternatively E 6013 electrodes can be used if welder is not competent to use E 7018 electrodes. But preference should be given to e 7015 electrodes.



REPLACEMENT OF FIRE TUBES

  • Confirm holes on tube plate are free from any foreign particles e.g. spatters, grinding burr etc.
  • Clean the tubes 2 inch on either end from oil, grease. Rust etc.
  • Insert the tubes in position as per drawing
  • Lightly expand tube to ensure no air gap between tube and tube plate contact surface.
  • Clean the joint from grease, oil, rust etc.
  • Preheat the area to 100 Deg C. minimum.
  • Weld root pass with 3 E 7018 @ 3.15 mm electrodes only.
  • Clean the weld thoroughly to remove slag, spatter etc
  • Check visually root pass to ensure sound weld i.e. It is free from crack, lack of side wall fusion etc.
  • Also carry out dye penetrant* (D P.) examination of free tubes, randomly selected, to ensure sound weld.
  • If any defect in weld is observed in visual /or D P. test remove the defect by grinding follow steps nos. 05 to 10.
  • Continue subsequent welding following step no 05 to 08
  • After completion of welding carry out visual examination 100% & D P examination of few randomly selected welds.
  • Conduct hydro test to confirm leak proof joint
  • Tube projection beyond the front and plate should be 2.5 to 3 mm max

Alternatively E 6013 electrodes can be used if welder is not competent to use E 7018 electrodes. But preference should be given to e 7015 electrodes.

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