Inspection limits

BEFORE storage tank managers jump on board magnetic flux systems for storage tank leakage inspection, they should realize the technology's physical limitations, said Morris Kline of HMT Tank Company.

However, he added that the scanner technology is the best method to evaluate a tank bottom condition quickly and cost-effectively. He made the comments at the Independent Liquid Terminals Association International Operating Conference June 5-7 in Houston, Texas.

Although considerable information has been available and presented on the technology limitations, some of the data is not common to all brands and types of the scanners used in the inspections. “So, it is not without controversy,” Kline said.

The American Petroleum Institute is working to quantify the technology limitations through a task group that is rewriting non-mandatory Appendix G in API Standard 653, which calls for operator qualification testing and certifications. “This effort is on-going, but will not happen soon,” he said.

Part of the limitation of using the scanners is a result of the tank bottom obstructions, such as weld seams, plate shapes and sizes, corner welds, patch plates, and thick reinforced coatings and annular plates. In addition, Kline pointed out that the system does not detect corrosion.

Kline advised managers to be aware of the technology's limitations, make an informed risk assessment, and revise or develop a work scope for the tank inspection vendor that addresses either all tanks or is specific to particular tanks based on tank characteristics, risk analysis, or tank condition.

“One of the cornerstones of any tank inspection is a visual check, but it only gives some clues,” he said.

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