Construction of Diaphragm Nozzles (all riveted attachment)
Diaphragm is a loose fit in the slot in the casing to allow for expansion. Construction of Diaphragm Nozzles (partial welded attachment)
The nozzle is assembled in batches by pushing the tenon of the blade throught the channel hole and riveting. A spacer is fitted and the whole tack welded. The blade batch is caulked into the casing. A small allowance is made for expansion. Some sections on the first stages may be blanked where partial admission used.
Modern turbine designs have a curtis wheel first stage which absorbs a large portion of the energy in the steam. The exahust from this stage has a relatively high volume therefore all further stages are full admission.
Construction of Diaphragm Nozzles (welded attachment)
Modern diaphragms are all welded.Nozzle plates or guide vanves fit into slots in the inner and outer rim. The whole is welded to the centre body and perpipheral guide ring. Expansion is allowed for in the casing groove. The Nozzle blades or guide vanes are commonly made from stainless iron. The centre body from Chrome Molybdenum steel in higher temperature regions, mild steel for the lower.
Archaic design
Included for general interest .