Higher order modes cluster (HOMC) guided waves for online defect detection in annular plate region of above-ground storage tanks
Corrosion detection in the annular plate region of above-ground storage tanks is a critical need for tank farm operators in the oil and gas industry. The critical zone between the tank shell wall and the first few inches of the annular plate is difficult to inspect with conventional
floor scanning methods due to the presence of coatings, uneven surfaces and a lack of access due to the presence of the weld toe. This region, however, is prone to accelerated corrosion due to the additional stresses caused by the weight of the tank wall and the increased possibility of water
entrapment under the annular plate. Repairs in this region demand replacement of the entire annular plate and this leads to long shutdown of the tank, and often failures occur without any warning. A new method using the Higher Order Modes Cluster Guided Waves (HOMC )
to detect and screen defects in the critical inaccessible zones in the annular plate is discussed. This testing can be carried out online while the tank is in operation using HOMC guided waves generated on the outer exposed region of the annular plate. Robotic scanners allow for the inspection
to be carried out in relatively short periods of time. Data collected in the laboratory as well as from the field trials are presented. The HOMC technique has potential for non-destructive inspection of inaccessible regions in structures for medium-range applications (2 to 3 m).
Keywords: Corrosion; HOMC; annular plate critical zone; condition monitoring; guided waves; petroleum industry; storage tanks; stress cracks
Document Type: Research Article
Affiliations: 1 Centre for Nondestructive Evaluation and Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai, India.
Publication date: 01 November 2009
- Official Journal of The British Institute of Non-Destructive Testing - includes original research and development papers, technical and scientific reviews and case studies in the fields of NDT and CM.
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