Abstract: Disclosed herein is a nozzle box assembly including a torus, a steam path ring, and a bridge ring. The torus has a plurality of steam inlets and an annular steam outlet. The steam path ring has an annular steam inlet, the annular steam inlet has an inner diameter (ID) and an outer diameter (OD), the steam path ring is disposed downstream of the torus. The bridge ring has an annular steam inlet and an annular steam outlet, the annular steam outlet has an ID and an OD, the bridge ring is disposed between the torus and the steam path ring, the bridge ring annular steam outlet is adjacent to the steam path ring annular steam inlet, and the steam path ring annular steam inlet OD is greater than the bridge ring annular steam outlet OD and the steam path ring annular steam inlet ID is smaller than the bridge ring annular steam outlet ID.

Abstract: A nozzle box includes a torus, bridge ring and nozzle ring portions wherein steam flowing generally circumferentially in the torus portion is redirected for flow generally axially by the bridge ring portion. The steam exiting the bridge ring portion flows into nozzles formed by adjacent partitions of the nozzle ring portion. Bridges in the bridge ring portion are tangentially leaned to exactly match the angle of inclination of the leading edges of the axially adjacent partitions at like circumferential locations. For strength purposes, there are two bridges for each partition. Every other bridge axially registers with the leading edge of the axially downstream partition matching its angle while remaining bridges are equally spaced between the aligned bridges. In this manner, the steam flow is straightened by the bridges to match the angle of the leading edge of the nozzle partitions with consequent reduction of passage area loss.

Abstract: A packing ring holder assembly for packing seal segments about a steam turbine rotor includes a nozzle box and a holder cooperable to form a dovetail for securing packing ring segments to the nozzle box. A spring is interposed between the nozzle box and packing ring segment to bias the latter radially inwardly for sealing with the rotor. The holder includes a shoulder for preventing axial movement of the spring in one direction.