Non-Destructive Testing of metal tubing for medical and industrial applications

Tubes are often made by a series of sequential drawing operations, each of which can introduce defects into the final product. These defects include both discontinuities (e.g draw lines) and dimensional inaccuracies (which can be in wall thickness, outer diameter (OD), inner diameter (ID), concentricity or straightness. As the tubes become smaller, the difficulty in measuring these accurately increases, resulting in the use of statistical sampling of tubes for destructive testing. Needless to say this is not ideal, resulting in the wastage of perfectly good tubes.

The problem of analysis of tubes such of these is not new, but the small scale of the tubing produced by Johnson Matthey introduces further problems to the testing, increasing the complexity of the testing. Furthermore, the range of sizes also provides its own obstacles. It is entirely likely that there will not be a one size fits all solution to the problem. The size range is also affected by the aspect ratio of the tubes, with each tube being up to 2 m in length. This length is then often sectioned by customers, giving them access to areas of the tube JM does not have access to.

The aim of the project therefore is to explore with the NPL enhanced methods for testing using existing NDT techniques. The project will start by considering the currently available methods, then downselect to the most promising techniques. These will then be developed to function on the smaller sized components produced by JM. Finally, the feasibility of the derived techniques will be considered from a manufacturing viewpoint. Ideally the techniques would be useable inline with the drawing process, but if this proves impossible then consideration will need to be given to where the testing would fit into the production facility, as well as at what stage the tube will be investigated.