REPAIR PROCEDURE OF FIRE TUBE BOILERS

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.