API-653 Inspection of 3.5 Million Gallon AST |
| Posted by Robert Sherby on Mar 07 2011 |
| News >> Projects |
TSP was recently approched by a long time customer to perform an inspection on a 3.5 million gallon aboveground storage tank. The tank was originally constructed during the 1940s and had spent many years unused. The tank's owner desired to return the tank to service and contacted TSP to provide a certification report in conformance with API-653.
TSP's API-653 inspector immediately identified the tank's age as a potentially significant issue. In the 1940s, API-650 had not yet been written, so the tank had been written under the earlier API-12A standard. More importantly, our understanding of the effects of carbon during the steel milling process was not as developed as it is today, raising suspicion that the older steel may be excessively brittle.
Visual and ultrasonic thickness inspection of the tank revealed few significant problems other than the potential for age related brittleness. Many of the welds on the tank were subjected to magnetic particle testing by a certified SNT-TC-1A magnetic particle inspection technician.
To evaluate brittle fracture potential, TSP clipped coupon samples in accordance with the recommended practices in API-650. The samples were submitted to a third party laboratory for brittle fracture evaluation.
TSP further performed minor repairs and evaluation of the floating roof. During the visual inspection, oil had been identified within the pontoons supporting the roof structure. TSP drained the pontoons, conducted repairs, then conducted dye penetrant testing to ensure that the welds would not leak.
Based on TSP's evaluation, the tank was found to be in generally good condition under the API standards. TSP issued a certification report finding the tank to be fit for service.
Last changed: Mar 07 2011 at 1:05 PM
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