Ultrasonic guided wave technique for the detection of extremely shallow corrosion defects in tie rods of coke oven batteries

Coke oven batteries utilize tie rods embedded within the concrete structure to enhance the structural strength of the oven walls. The tie rods are susceptible to corrosion in the form of gradual reduction in cross-section over a large length (1-2 m) of the tie rod which compromises the structural integrity of oven walls. This work describes an ultrasonic guided wave technique utilizing low frequency L(0,1) mode to detect and locate such shallow corrosion defects with access only to the ends of the tie rods. FEM studies describing the behaviour of L(0,1) mode for various geometrical parameters of the defect are discussed. The FEM results are validated by few experimental results on tie rods with corrosion defects. The accuracy of the measurement technique, in the experimental results, for locating the axial position of defect and its length was found to be >94% and >86% respectively.