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.
Development of Corrosion Loops or areas with emphasis on CUI and External Corrosion.
Completion of an initial inspection of all areas in the refineries to establish scope.
A thorough review of the equipment history.
Criticality and risk ranking of pieces of equipment based on initial inspection and equipment history review.
Amount of insulation removal and inspection coverage in line with the initial inspection and risk ranking.
Project approach to assure sustainability for the CUI and External C
External corrosion and CUI continues to be a major issue for all refineries and petrochemical plants throughout the world. CUI was brought to the awareness of the industry as a damage mechanism in the early 1980?s(1,2). Over many years, refineries and petrochemical plants have experienced extensive damage due to these mechanisms and as the refineries and petrochemical sites age, this external damage become more prevalent. To mitigate this damage, most refineries and petrochemical sites are instigating a CUI/External Corrosion Program. This paper details the methodology used by two of these refineries to address this damage. Most CUI/External Corrosion programs follow the same basic steps as noted below:
