The electrical potential drop technique is one of the promising methods for monitoring the pipe wall thinning. In order to verify this method, preliminary thickness measurements were conducted for uniform and local thinning created on plate specimens. The result showed the electrical potential drop technique had a good performance equal to the ultrasonic testing method. The success in the preliminary tests allowed this technique to be applied to some pipes in thermal power plants in order to monitor the wall thinning and this on-line monitoring has continued for two to three years. It was confirmed that this technique was valid in terms of a long-term durability. Following these results, technical requirements on the potential drop technique were proposed to the JSME (the Japan Society of Mechanical Engineers) Rules on Pipe Wall Thinning Management for Thermal Power Generation Facilities (JSME S TB1-2006) and stipulated in those rules. In this paper, these rules are simply introduced and the on-line monitoring of the pipe wall thinning by means of the electrical potential drop technique is discussed through the results in the plate-specimen-tests and the real-pipe-tests in operating thermal power plants.
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