Development of High-sensitivity Crack Depth Gauge for Narrow Places
February 29, 2012
Chubu Electric Power Co.,Inc.
Chubu Electric Power Co., Inc. (President & Director: Akihisa Mizuno; head office: 1, Higashi-shincho, Higashi-ku, Nagoya, Aichi Prefecture) and Tohoku University (President: Akihisa Inoue; location: 1-1, Katahira, 2-chome, Aoba-ku, Sendai, Miyagi Prefecture) have successfully developed a “high-sensitivity crack depth gauge for narrow places,” which makes it easy to find the depths of cracks in narrow parts of metal components.
Sales of the new gauge will begin on April 1, 2012 from Hoyo Elemec Co., Ltd. (representative: Mitsumasa Toyokawa; location: 7-6, Aza-Ishidzuka, Koriyama, Taihaku-ku, Sendai, Miyagi Prefecture).
Metal components used in bridges and other structures, in oil and chemical plants, in power generation facilities, etc. can develop cracks as a result of metal fatigue, corrosion and so on following long-term use, etc. Maintaining such facilities requires correctly determining crack status, but cracks often have complex shapes and occur in narrow places like corners, so it is difficult to measure their size (depth) with existing technologies like ultrasound method. As a result, determining crack depth and deciding how to repair them has required time-consuming, labor-intensive methods such as scraping back the metal surface.
The recently developed “high-sensitivity crack depth gauge for narrow places” uses a DC potential difference method that was intended for use with cracks on flat surfaces. In contrast to earlier technology, a technique has been newly developed that estimates crack depths in corners based on the route through which direct current flows, the position at which potential difference is measured, and the value measured for the potential difference. This can greatly expand the range of application.
Chubu Electric Power has been doing field experiments with the gauge at a thermal power station for about three years, finding that it provides sufficient precision and ease of operation. As a result, it is now possible to quickly and correctly determine the state of cracks without labor-intensive practices such as scraping back the metal surface as in the past. We believe this can greatly contribute to the maintenance of older facilities and equipment.
Major features of “high-sensitivity crack depth gauge for narrow places”
(1) Able to measure crack depth in narrow places
The gauge can measure crack depth in hollows, places with differences in level, corners and other narrow places difficult to measure with other methods like ultrasound.
(2) Ease of operation
No special qualifications are necessary to operate the newly developed device. By merely placing the probe onto the crack, the operator can easily read the crack depth, which is shown on a digital display in 0.1-mm increments.
(3) Compact and lightweight (battery powered)
The main body of the newly developed gauge weighs about 3 kg, making it possible to carry around the site and take measurements where needed.