Many pipes and pipelines are covered with a thick coating (weightcoat) to keep heat in (or out), to add weight, or to protect against corrosion. In some instances, the coating process may not give a uniform thickness and it is required to measure the variation in coating thickness around the pipe.

Caliper measurements can only give a value for the average thickness at any diameter, not the position of the pipe under the coating.

The process of pipe laying forces the pipe to be bent and re-straightened which can lead to the pipe becoming oval. If the pipe is uncoated this ovality can be measured by calipers, but this technique does not work on coated pipe where the coating may be varying in thickness, or bulging away from the pipe surface.

TSC’s Lift-off sensors can be used to give spot measurements of the distance between the coating surface and the underlying pipe surface, or between a fixed circle and the pipe surface, and hence give values for coating thickness and/or pipe out-of-roundness.