Getting to the root of the problem.

This paper reports on new instruments for identifying corrosion of steel lighting columns. CMT (Instruments) has spent two years addressing the problem of assessing the two areas most vulnerable to corrosion: the root and sleeved or swage joints. In the past inspection has been visual or by ultrasonic thickness. The Relative Loss of Section meter uses an electromagnetic technique to compare the mean sectional wall thickness of the column above and below ground level. A transponder head is located against the column to obtain reference terms. The head is then placed on the ground with the face against the column and a reading obtained; this process is repeated at 90-degree intervals round the column. Field testing has defined four categories in terms of Loss of Section Units, the worst category being those columns at risk of collapse. The Swage Joint Analyser was developed to assess loss of section from the internal surface at the swage joint. It also uses the same techniques and can be used to produce a three dimensional assessment of relative wall thickness. The instruments enable those columns at risk to be scheduled for action, and those in sound condition to have future monitoring economically scheduled.