Boiler system is one of the most critical systems for a utility plant. A utility plant had experienced high percentages of boiler downtime owing to boiler tube sheet cracking failures. Investigations carried out revealed high stress at the tube-to-tube sheet joint in the boiler fire-side entrance. Tube-to-tube sheet joints at the boiler fire-side entrance had been fabricated by strength welding and without any expansion. The strength welded joint had created undue stress leading to cracking of the weld joint by thermal expansion. A higher quality expanded joint consisting of expanding, flaring and seal welding the fire-side entrance was implemented during the re-tube process. The utility plant has now zero downtime due to boiler tube failure. This article summarizes the description and history of failures with the boiler at the utility plant; investigations and corrective actions carried out; and the present improved condition of the boilers.

Subject
Water, Tubes, Welding, Leaks, Inspection, Joints, Acidity, Thermal stress, Repair, Boilers, Boiler feed water, Steam, Blow down
Keywords:
Failure Investigation, Boiler tubes, Fire tube boiler, Weld defect, thermal stress, infrared thermography, boiler chemical treatment, pH, TDS, dissolved oxygen
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2019
Association for Materials Protection and Performance (AMPP)
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