|By Rolf Diederichs|
In Germany happened in July at Cologne's railway station an incidence which released a strong debate on Deutsche Bahn's safety management. A defective axle caused one of the high-speed trains to derail. Without much doubt we have to deal with a fatigue damaging mechanism, which apparently has been underestimated. In the NDT.net forum this issue was discussed by Rolf Diederichs and Herman Wuestenberg, but why nobody else joined this discussion? To complex? Business relations with Deutsche Bahn? Perhaps some experts of the aircraft field could enlighten the railway scene.
Prof. Dr.Ing. Hermann Wuestenberg is an outstanding NDT professional who has contributed significantly to the research and development. He writes in the forum how to deal with a fatigue damaging mechanism. "There are always three factors to be considered, the mechanical strength of the structure, the collective of loads and the non-destructive inspection strategy based on a clearly defined knowledge about the crack growth to be expected. Those influences are the mayor ingredients of what is called a Risk Informed Inspection, a concept discussed and applied e.g. in the nuclear industry for the inservice inspection of pressurized components (see also ASME Section XI)."
As member of the reactor safety committee of Germans environment ministry, Wuestenberg has deep experience in Risk Informed Inspection. Since the end of 2001, he retired from BAM, but is still active in some committees and in teaching.
The expert continues in the forum: "First remark to be made is, that even new and modern inspection techniques have to demonstrate their performance as e.g. described in the Appendix VIII of ASME Section XI or in the European ENIQ document. It is not sufficient to demonstrate with the help of a reference axle with test reflectors the correct sensitivity setting. A performance demonstration should deliver a kind of POD (probability of detection) estimate for cracks with different depth under the realistic surface condition of an axle in service. Only with such an information the contribution of the NDT to a general risk management can be evaluated. Are there any efforts made by the DB AG to assure the NDT performance according to the above mentioned concepts?". The complete post of Hermann Wuestenberg click here.
German readers may read an interesting "ICE3" blog by Winfried Wolf, a German Author, Journalist and democratic socialist politician. In his blog a comment of someone himself called expert writes among other things "Ultraschalluntersuchungen sind sozusagen der Hosenträger".