For use in the pipe mill to measure the thickness of the Inconel lining in the pipe after extrusion. The head carries several sensors in order to detect radial variations in clad thickness, such as eccentricity. Normally 4 sensors are sufficient but up to 8 can be accommodated.
The sensors are continuous reading. A computer data collection system samples the readings at pre-determined intervals, typically 500 samples per second. The pull speed through the pipe is typically 0.5 metres per second resulting in clad thickness reading every millimetre. Faster pull speeds and sampling rates are possible.
The pipe to be inspected is placed in line with a reference pipe, the probe normally ‘lives’ in the reference pipe and is driven out into the other pipe for the inspection run.