Condition Monitoring of a Power Tower Using Metallurgical Investigations of Structural Members

A spectacular damage occurred at the end of 2005 in Münsterland when a large number of power towers in 110 kV transmission lines collapsed due to increased loads of ice and snow, which raised awareness amongst experts for the evaluation of a continuous safe operation of historical towers. At the time, it was found that embrittlement by strain ageing was a contributing factor. The in-house client ordered the condition evaluation of a power tower located on his premises. The evaluation was performed by testing four so-called structural members from this tower. Mechanical-technological material tests were performed exclusively on samples from the flat, mostly not cold-formed areas of the structural members' angle irons. The results of all these tests were inconspicuous, including the notch impact tests at −20 °C. Therefore, it is safe to say that the material at hand is generally not in an embrittled condition. In this context it is also interesting that the nitrogen content of the batch the angle irons of the examined structural members were made from, did not exceed the embrittlement sensitivity threshold of 0.01 percent by weight set by the Federal Institute for Materials Research. From a material-technological perspective, there is no objection to a continued safe operation of the power tower on the client's premises. Further tests and repairs were not considered necessary.