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API 653 Out-of-Service Inspection Report i Mill! for J.R. Simplot Inspection Tank No. 8 August 27-28,2008 Lathrop, CA Page 6 of 54 SUMMARY, REPAIR RECOMMENDATIONS AND POST-REPAIR FINDINGS (CONT'D.) BOTTOM: Visual (VT) inspection was performed on the bottom lap welds. Approximately twenty-seven (27) areas of weld corrosion and poor quality weld were identified and marked for repair. These areas should be re-welded using approved welding and NDE procedures per API 653, Para 9.6 guidelines. The location of the areas requiring repair can be found on the Bottom Plate Layout drawing. Post-Repair Comments: At the time of this post-repair inspection, all bottom lap welds identified for repair were properly repaired, and had Visual (VT) inspection performed and were found to be in acceptable condition. The 2"d bottom was installed in 1987. The construction detail does not meet API 650 / 653 requirements in that the bottom does not extend through the shell. A 2-inch by 2- inch angle was utilized at the shell-to-bottom joint to attach the shell to the bottom plates (ref photos). Although no changes are required, this detail is not standard practice and consideration should be given to installing a bottom that meets API 650 / 653 design requirements. The roof support column is welded to a bearing plate that is welded to the bottom. This detail results in the roof being rigidly connected to the bottom and this practice is not recommended. Consideration should be given to modifying this detail so that the column is not rigidly connected to the bearing plate and is allowed to move vertically but not laterally. A wear pad constructed of bricks and bordered by structural angle was installed below the new top fill nozzle on Bottom Plates 5 and 6. The angle was tack welded to the bottom (ref. photos). Consideration should be given to installing bearing plates beneath these items by seal welding to the bottom using appropriate welding and NDE procedures per API 653 guidelines. Bearing plates, while not required, provide additional thickness in areas inaccessible to inspection equipment. SHELL: Shell thickness calculations obtained during this inspection indicate a maximum safe fill height of 23.00 feet can be utilized with product specific gravities up to 1.8 (sulfuric acid at 98% concentration). The hydrostatic test height can, therefore, utilize this maximum fill height (ref. API 653, Para. 4.3.3.1). These calculations do not take into account operational restrictions from such items as high-level alarms or owner 1 operator-imposed safe fill restrictions. APIRPTNE.WT REV 2 2528030418r.coc 912 5/1 0 0 8 10:09 AM