Safe Diagram - A Design And Reliability Tool For Turbine Blading.

The complex field of turbine blade vibration has long been in need of improved tools to help predict the reliability of blading. The SAFE interference diagram is presented as such a tool. It presents much more information than the widely used Campbell diagram. In evaluating interferences, the SAFE diagram compares not only the frequencies of exciting harmonies with natural frequencies of blades, but also the shape of these harmonics with the normal mode shapes of a completely bladed disc including packeted blading. Examples are given of cases where the Campbell diagram predicts a dangerous resonance while the SAFE diagram shows that no resonances exist which are supported by experience. Examples are also provided to show when the SAFE diagram can pinpoint what interference is likely to cause the largest blade vibration. Finally, it is shown how a simple change in packeting can be used to change the blade interference and to avoid dangerous operation.