An Efficient Technique for Storing Eddy Current Signals

Abstract

Preventive maintenance schemes often involve periodic inspection of plant and equipment in industry. Evaluation of the integrity of the plant at regular intervals provides data not only for the detection of defects in their incipient stages but also for monitoring the evolution in the growth of defects that were considered benign in previous inspections. Evolution in the nature of defects is tracked by comparing the signals obtained with test data obtained and recorded from previous tests. Consequently the procedure entails storage of a large amount of data during each inspection. As an example, the Nuclear Regulatory Commission mandates periodic inspection of steam generator tubing in nuclear power plants using eddy current techniques. The signals are recorded on a multichannel analog tape recorder with one of the tracks dedicated for storing the voice of the operator who records the details of the test conditions. A major disadvantage of this approach lies in the voluminous nature of the data necessitating the use of a large amount of storage media. In addition it is difficult to address and access specific data records.