Risk Assessment of an L-0 Stage Blade Retrofit

Abstract

The tie-lugs on a 46” last stage blade (LSB) operated in a power plant first commissioned in the early 1960s experienced a long service history of cracking problems. A root cause investigation was performed, which identified the third mode of the bladed disc as operating near resonance. The original configuration is a 4-blade group structure with two tie-lugs. The third mode is a group torsional mode in which maximum stress occurs in the outer lugs. Dynamic stress throughout the rotating stage was calculated using a FE model. Based on the results of the investigation features of a retrofit were identified to detune the resonant mode and change the brazed lug to a more reliable forged design. A probabilistic analysis was used to demonstrate how the risk of cracking problem would be dramatically reduced.

Effect of Recycled Aggregate on the Compressive Behavior of Short Concrete Columns.

“…he lower Pcr of RAC can be attributed to the relatively higher water absorptiveness of RG, which should have created a steeper moisture content gradient from the cover layer to the interior layer of the specimen. In turn, the moisture content gradient due to RG can cause higher incompatible drying shrinkage between the interior and exterior RAC, compared to that of NAC [16], thereby facilitating the cover was spalling. Furthermore, the lower bond strength between the rebar and RAC than NAC [17] also contribute to the lower cover spalling load and the faster rate of cover degradation in RAC compared to those of the NAC columns.…”