Probe holder providing constant lift-off for in-line bar-pipe testing

Abstract

Disclosed is a probe holder for in-line inspection of the surface of bars of high value alloys. To attain full coverage of the inspected surface, the bar is rotated while either the bar or the probe holder is translated. The probe holder of the invention ensures constant probe lift-off by allowing the probe to move freely under its own weight, while constraining the motion to be only in the radial direction of the bar. The lift-off distance is defined by a spacer which is made of soft material to avoid damaging the inspected surface. Although the spacer is soft, its wear due to friction with the rotating bar is minimized by minimizing the pressure between the spacer and the bar. This is achieved by resting most of the mechanism weight on two rollers, with only the much smaller weight of the probe resting on the spacer.