ArcelorMittal Newcastle South Africa
Blast Furnace N5, Hot Blast Stoves, Cross-over Repair

In February 2014 AMSA awarded an order to HeatTeQ for various repairs of the hot blast stoves of blast furnace N5. The stoves, designed by Krupp Koppers, are of the external combustion chamber type provided with ceramic burners. Included in the scope was the repair of the cross-overs connecting the burner shaft with the checker shaft.

Facts and Figures

Site: ArcelorMittal Newcastle South Africa
Duration: 3 months
Plant: Hot Blast Stoves BF N5
Design: Krupp Koppers
Execution: May-September 2014
Scope: Cross-over repair
Subcontractor Mechanical: Elinem
Subcontractor Refractories: Anmar

Scope of work

The external combustion chamber Koppers design stoves at AMSA's Newcastle BF5 have suffered from hot spots at the cross-over section. Because endoscopic inspection of the inside of the cross-overs showed no damage to the dense lining it was assumed that the cause of the problems was failure of the insulation. The Koppers design external combustion chamber stoves compensates the difference in the shell expansion between the checker and combustion chamber and the radial expansion of the domes due to thermal expansion and pressurizing and depressurizing by two stainless steel expansion bellows installed in the cross-over.

Based on the results of internal and external inspections the following scope of work was agreed upon:

  • Replacement of the existing damaged expansion bellows by new bellows
  • Replacement of the outer shell ring 360*
  • Replacement of the inner shell (both sides) 180*
  • Replacement of the upper 180* of the two layers of insulation lining.

To allow repair under hot conditions a special repair scenario was developed.

  • Remove the existing compensators complete with the outer shell between the two existing thrust collars.
  • Remove top half of the inner sleeves exposing the refractories.
  • Remove and replace two layers of insulation over the top half.
  • Install new inner sleeves over the newly installed insulation.
  • Install new expansion bellows on both sides of the cross over. Because the cross over refractories remained inplace the bellows had to be installed as clam shells in two halves. Welding the two halves together was done in situ by specialized welders from the supplier.
  • Install the outer shell in two halves and weld in situ to the bellow stubs.

During the execution of the repairs it appeared that on stove 1 the condition of the lower half of the cross over was so bad that complete replacement was required. It was therefore decided to cool the stove down to ambient. After cool down the old expansion joints, the outer and inner sleeves and the refractories in the cross over were removed. After installation of new inner sleeves new refractories were installed and the new expansion joints and outer shell could be erected. The space between the inner sleeves and the outer shell was filled with an insulating castable.