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API 653 Out-of-Service Inspection Report M M hh��A for m m m m J.R. Simplot Inspection Tank No. 8 August 27-28,2008 Lathrop, CA Page 7 of 54 SUMMARY, REPAIR RECOMMENDATIONS AND POST-REPAIR FINDINGS (CONT'D.) SHELL: The tank has no anchor bolts or alternative means of providing shell stability against seismic and wind overturning loads. Seismic analysis of this tank per Appendix E of API 650, 10" Ed., w/Addendum 3 requirements for Zone 3 (i.e. Stockton, CA location).indicates the tank is stable against such overturning loads without anchorage. Wind analysis of this tank per API 650, Para. 5.11 found the tank is stable against such overturning loads without anchorage. Calculations with consideration given to seismic loading indicate a safe fill height of 23.00 feet(at a product specific gravity up to 1.8). Visual (VT) inspection of the internal Course 1 to Course 2 circumferential weld revealed an area of weld erosion on the northeast side approximately 2 feet long. The likely cause is the location of the top fill nozzle (relocated due to this issue) that appears to have circulated the product along the shell. Due to the severity of the erosion on the circumferential weld, this area will need to be repaired using appropriate welding and NDE procedures per API 653'guidelines. The internal shell plates of Courses 1 through 3 have general corrosion present in the east to northeast tank quadrants: Again, the likely cause is the location of the top fill nozzle that appears to have circulated the product along the shell. Pit depth measurements range from 0.030 inch to 0.050 inch. If the tank is operated in future under similar conditions, then the corrosion may continue to worsen. At this time the top fill nozzle has been relocated so that it is not close to the shell. Consideration should be given to monitoring this issue during the next internal inspection and to taking the tank out of service after a shortened future service internal to re-evaluate the corrosion or to coating the inside of the shell at this time. There are numerous pipe support brackets still attached to the inside of the shell that are no longer utilized. Consideration should be given to removing these brackets or grinding them flush to the shell since it appears that the stored product (sulfuric acid at 98% concentration) attacks the underside of the old supports and could cause shell corrosion to develop (ref. photos). The shell coating is weathered and has water 1 dirt streaking down the shell. In addition, the coating has failed at the shell-to-bottom joint at random areas around the tank and behind the level indicator board along the entire shell. Consideration should be given to re-coating the shell in the near future. The overflow downspout, level indicator board and stairway support brackets do not have reinforcing plates. This is provided as information only and no corrective action is required at this time. Consideration should be given to installing seal welded reinforcing plates under each support the next time major repairs are made to the shell or when a hydrostatic test is required for other reasons. APMPTNE.DOT REV 2 2628030418r.doc 912512008 10:09 AM