Abstract: Rhombic shrouded tangential entry buckets are circumferentially applied to the rotor wheel rim of a turbine. A fixture is releasably secured to a lug on each bucket and includes a chamfered surface for engaging a complementary surface on the lug. Upon applying a tangential assembly force, the shroud and airfoil of adjacent buckets are pre-twisted in a rotational direction about a generally radial axis enabling dovetail faces to contact one another notwithstanding interference fit shroud contacting surfaces. The removal of the fixture from the lug enables the bias of the airfoil to rotate the shroud in an opposite direction into final assembly with the shroud edges of adjacent buckets in contact with one another and the dovetail faces thereof in contact with one another.

Abstract: Steam turbine bucket covers have forward and aft clearance surfaces on a pressure side edge of the cover, a contact surface between the clearance surfaces and an undercut fillet between the forward clearance surface and the contact surface. The adjoining bucket cover has forward and aft clearance surfaces, a contact surface between the clearance surfaces and an outside radius between the forward clearance surface and the contact surfaces along the suction side edge of the cover. The undercut fillet includes two different radii to minimize or eliminate fretting damage caused by high stresses in the interference fit between the contact surfaces of adjacent covers.

Abstract: The control stage buckets for a steam turbine have airfoils which are hollowed out to form an interior cavity within the airfoil. The cavity opens through the radial inner platform of the bucket and terminates short of the tip of the bucket. The buckets are therefore of reduced weight. This reduced weight causes reduced creep damage in the axially extending dovetails along the rotor rim.