Cracks in Incinerator Recuperator – Failure Investigation & Repair

Failure Analysis and Repair of an Incinerator Recuperator at a Chemical Plant.

The investigation revealed a critical issue with cracks developing through the ligaments of the tubesheets, resulting in significant leakage. The root cause was identified as severe differential thermal expansion between the heavy steel frame, which provided peripheral restraint, and the perforated tube sheet.

Failure Mechanism

The differential thermal expansion led to tearing of numerous tube sheet ligaments. Further analysis confirmed that the initial failure of a single ligament triggered an almost instantaneous progression of failure through rows of ligaments. This cascading effect exacerbated the problem, leading to widespread damage and compromising the recuperator’s integrity.

Repair Strategy

To address the issue, O’Donnell Consulting Engineers designed an effective repair strategy:

• Sleeve Insertion: The team inserted and rolled sleeves into the ends of the existing tubes where the tubesheet ligaments had cracked.
• Seal Welding: The inserted sleeves were seal welded to the original tubes, ensuring a secure connection and preventing further leakage.
• Reinforcement: A stainless steel pad was applied to the tubesheet, serving two crucial purposes:
  – Sealing the cracked ligaments
  – Strengthening the tubesheet for temporary operation

This repair approach not only addressed the immediate problem but also provided a temporary solution to maintain operations while a long-term fix could be implemented.