SEDL / STP / STP223-EB / STP41983S

Inspection of Small Diameter Tubing by Eddy Current Methods

Allen, J. W.
Oak Ridge National Laboratory is operated by the Union Carbide Nuclear Co. for the Atomic Energy Commission, Metallurgy Division, Oak Ridge National Laboratory, Oak Ridge, Tenn.

Oliver, R. B.
Oak Ridge National Laboratory is operated by the Union Carbide Nuclear Co. for the Atomic Energy Commission, Metallurgy Division, Oak Ridge National Laboratory, Oak Ridge, Tenn.

Pages: 24    Published: Jan 1958

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Abstract

The present trend toward higher operating temperatures and pressures in the design of thermal power generators, both nuclear and chemical, is causing an increasing amount of concern among those involved in these industries over the quality of heat exchanger tubing used in construction of these devices. This concern has precipitated a search for fast, accurate, and inexpensive methods for 100 per cent inspection of large quantities of small diameter tubing. Of major concern in the inspection of this tubing is the detection of cracks, pinholes, pits, gouges and other mechanical defects, intergranular attack, nonmetallic inclusions, and foreign metal pickup. Also it is desirable to gage tubing continuously for dimensional tolerances. Recently, the inspection of tubing by the relatively new methods of pulse-echo, immersed ultrasonics and electromagnetically induced eddy currents has received a considerable amount of attention. The development and application of these techniques to the inspection of small diameter tubing for small defects has been pursued vigorously in the nondestructive testing laboratory at the Oak Ridge National Laboratory; although a great amount of success has been enjoyed with both methods, it has been found that neither method in itself, nor any other known method in itself, can accomplish all of the previously mentioned requirements. Fortunately, however, the inherent inadequacies of these methods are not common to both; therefore inspection utilizing both techniques will fulfill most requirements.