Turbine blade ring assembly and method for assembling turbine

A method for assembling a turbine, the method comprising:

• a step of attaching a seal-ring retention ring upper-half portion including a plurality of split plates disposed in a circumferential direction and a plurality of biasing springs that bias the plurality of split plates in an axial direction to a casing lower half to which a turbine blade ring lower-half portion including a blade ring in which a plurality of stator blades are retained and a seal-ring retention ring is attached;
• and
• a step of attaching a blade ring upper-half portion in which the plurality of stator blades are retained to the seal-ring retention ring upper-half portion attached to the casing lower half,
• wherein the plurality of stator blades included in the blade ring upper-half portion have protrusion portions protruding to a radial inner side,
• the plurality of biasing springs included in the seal-ring retention ring upper-half portion bias the plurality of split plates included in the seal-ring retention ring upper-half portion to abut against the protrusion portions,
• the plurality of split plates included in the seal-ring retention ring upper-half portion include
• a first split-plate group in which the plurality of split plates are disposed in the circumferential direction on one side in the circumferential direction of the seal-ring retention ring, and
• a second split-plate group in which the plurality of split plates are disposed in the circumferential direction on the other side in the circumferential direction of the seal-ring retention ring,
• the plurality of split plates constituting the first split-plate group include
• first split plates, and
• second split plates disposed at positions close to an end portion on the one side in the circumferential direction of the seal-ring retention ring with respect to the first split plates and adjacent to the first split plates in the circumferential direction,
• the first split plates have one-side first overlapping portions overlapping the second split plates in the circumferential direction,
• the second split plates have other-side second overlapping portions overlapping the one-side first overlapping portions in the circumferential direction,
• the one-side first overlapping portions abut against the other-side second overlapping portions via the first split plates being biased by the biasing spring,
• the plurality of split plates constituting the second split-plate group include
• third split plates, and
• fourth split plates disposed at positions close to an end portion on the other side in the circumferential direction of the seal-ring retention ring with respect to the third split plates and adjacent to the third split plates in the circumferential direction,
• the third split plates have other-side third overlapping portions overlapping the fourth split plates in the circumferential direction,
• the fourth split plates have one-side fourth overlapping portions overlapping the other-side third overlapping portions in the circumferential direction, and
• the other-side third overlapping portions abut against the one-side fourth overlapping portions via the third split plates being biased by the biasing spring.