New last stage is a first

A retrofit at Great River Energy’s 1100 MWe Coal Creek coal station marks the first installation of GE’s new 26.8 in last stage bucket (LSB) with axial entry dovetail. The technology has been developed to help older power plants remain competitive by increasing the output and reliability of the low pressure sections of their steam turbines, which account for about 50% of total output, and to thus help offset power used for new environmental control equipment.

The new 26.8 inch LSB was applied to the first of the two GE steam turbines at Coal Creek. The section replacement was completed in April 2008 with the unit re-entering commercial service in May 2008.

The new steam path replaces the original 26 in LSB steam path design. The bigger exit annulus and reduced exhaust losses increase plant output without increasing heat to the turbine or fuel to the boiler.