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Consider these guides for stress relieving of vertical towers

12.01.2011  |  Ayari, H.,  Ultragen Ltd., Quebec, CanadaTruong, K.T.,  Ultragen Ltd., Quebec, CanadaTruong, D.,  Ultragen Ltd., Boucherville, Quebec, Canada

This case history investigates all required post-weld heat treatment for an existing column

Keywords: [corrosion] [welding] [heat treatment] [pressure vessel codes] [maintenance] [towers] [refinery]

Damage from corrosion mechanisms often leads to failure in refinery equipment and creates safety hazards, which interrupt refinery operations. The corrosion-under-insulation (CUI) phenomenon occurs in insulated vessels when the vessel shell is in continuous contact with insulation that has become wet, thus enabling oxidation and loss of material. During a routine external inspection, the removal of the insulation around the shell of a process vessel revealed that the CUI had extended around its entire circumference (Fig. 1). The remaining thickness in affected areas of the shell ranged from 0.338 in. to 0.625 in. (being the original thickness). The tower was assessed for potential risk of collapse, and an external weld overlay technique was used as a permanent repair method that restored the corroded areas to original thickness (Tables 1 and 2).

 
  Fig. 1. Corroded area (A) and inspection
  sketch (B).  

 


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