Abstract
Corrosion under Insulation (CUI) and External Corrosion continue to be a major issue for all Petrochemical facilities throughout the world. Over many years, refineries and petrochemical plants have experienced extensive damage due to these mechanisms. As a result, several of the company refineries have been investing in a CUI and External Corrosion inspection program. This paper details the methodology used by two refineries for addressing this damage and lessons learned throughout the implementation.
The methodologies used by the two refineries differed at first in that one approach involved an initial cursory inspection of all areas in the refinery and history review of all fixed equipment items followed by a thorough inspection and maintenance refurbishment of equipment selected by this initial inspection. The second approach involved a software based desk top study with no initial inspection. The programs are being managed as a total refurbishment project, which include the identification of lines and vessels operating below 350 degrees F; inspection of vessels and lines, including insulated and painted lines; 100% removal of insulation in areas ranked High and Medium High based on the assessment above; repair where necessary; repaint and finally re-insulate if necessary.
The paper also describes the findings from the work carried out so far. At Refinery A which followed the initial cursory inspection approach, 18 vessels have had 100% insulation removal, 200 miles of piping have been visually inspected and 16 miles of piping refurbished. For vessels, 89 areas had lost part or all of the corrosion allowance, 26 areas had undergone weld repairs, 2 tower top heads have been replaced and a further nozzle replaced. On piping, 137 areas were found to have gone through part or all of the corrosion allowance and 61 further pipe sections required replacement. At Refinery B, the areas for inspection were selected using a desk top study. The selection did not include an initial inspection of the entire refinery. The desk top study directed the efforts to discrete areas of the refinery where external conditions of insulation and long range NDE’s were then used to decide whether further insulation removal was necessary. The approach at Refinery B has resulted in fewer inspection finds and it is now adjusting the CUI/External Corrosion program based on these finds and the lessons from Refinery A.
