Page 49 - Steam Turbines--Design, Applications, and Rerating by Heinz-Bloch, Murari-Singh

30 Chapter Two

accommodation of transient thermal stresses and provide a design that
resists shell cracking and alignment changes during operation.
The double-shell construction prevents initial steam being in direct
contact with the outer casing joint. A double-shell back-pressure tur-
bine for high inlet steam conditions is shown in Fig. 2.1.
Adjusting devices allow all parts of the turbine to be aligned to each
other, and the turbine to be aligned to the foundation, without the need
to machine shims, etc.
The parts of the turbine that control the position of the rotating com-
ponents in relation to the fixed components are supported and located
precisely at shaft height: they move independently of each other. On
large turbine casings distortion cannot be transmitted to the bearings.
On these turbines, the bearings are supported on adjusting devices in
fixed bearing pedestals completely separate from the steam-carrying

Figure 2.1 High inlet pressure reaction turbine, back-pressure type. (Siemens Power
Corporation, Milwaukee, Wis. and Erlangen, Germany)