Pipework
Long lengths of pipe work should be avoided, as should be tight bends as these can lead to fluid friction losses in the steam and pressure loss. Hangers and sweeping curves before inlet to casing should be employed to ensure no weight on casing.
For the cross over pipes, to avoid large curves or frictional losses the following is now employed.
The pipes fitted to the casing should have large flexibly supported bends and/or bellows pieces. If not they can give side or top thrusts on the casing and lead to stressing and misalignement.
An alternative to sliding feet as shown is to use elongated holes. The holes being elongated in the direction of required expansion. The bolt is then of the loose fit design.
Care must be taken with all sliding arrangements to ensure freedom of movement. Surfaces should be kept clean, lubricated ( molybdenum disulphide ) and free of rust and paint.
Differing materials may be used for the varying components.
Expansion arrangements
Allowance for expansion over the temperature range in which the turbines operate is essential to reduce thermal stress, mechanical stress and maintain proper tooth contact and blade clearance. This is acheived by securing the turbine at one end and allowing to expand. The free end is normally the hotter end of the turbine where expansion is expected to be greatest.
The turbine is allowed to expand in the fore and aft direction by molybdenum disulphide lubricated sliding feet
