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• Applications Note L <br /> STORAGE TANK LEAK DETECTION <br /> PRAMM 1 <br /> CORP. <br /> Problem Description ' <br /> Many above-grade storage tanks now in service were constructed 20 or <br /> more years ago - sufficient time for the mechanisms of metal corrosion and ' <br /> stress-fatigue cracking to weaken and perhaps breach the tank floors. The <br /> resultant tank floor leaks are often unnoticed by plant personnel during ' <br /> the performance of their daily routines. These leaks can be costly, both <br /> in terms of product loss and potential liability for environmental , <br /> Pollution. <br /> Until recently, techniques for tank-floor integrity testing were ' <br /> generally limited to visual inspection or still gauging. Visual ' <br /> inspections require the tank to be emptied, cleaned and carefully examined, <br /> Putting the tank out of service for weeks or more. Even then, some small <br /> leaks can be overlooked. ' <br /> Still-gauging methods are adequate for only the largest leaks. The <br /> accuracy of most tank-installed liquid level gauges is usually one-eighth <br /> inch at best. A product loss reflected by a 0.062-inch level drop for a ' <br /> 100-foot diameter tank translates to a 306 gal/day leak. If this 1/16-inch <br /> drop in product level is not discernible from the masking effects of fluid ' <br /> expansion, losses in excess of 2650 barrels annually will go undetected. <br /> At twenty dollars per barrel, this loss amounts to over $53,000 for a ' <br /> single tank. The associated liability risks of ground-water contamination <br /> could involve much greater potential costs. <br /> Acoustic-emission (AE) technology offers an economical solution to <br /> leak detection in these large-volume above-grade storage tanks as well as <br /> in pipelines, heat exchangers, valves and pressure vessels. <br /> C M 9173 Chesapeake Drive ' <br /> San Diego. California 92123 ' <br /> Telephone:(6 1 9)292-8922 0 Telex 295468 PL GS UR <br />