Abstract: The broach assembly includes alternate spacers and cutters arranged in a sub-assembly having a lead at a leading end and a lag at a trailing end. The cutters have side margins in excess of the margins of the spacers for cutting material from the dovetail slots of the turbine wheel as the broach assembly passes through the slots. The bottom or apices of each spacer and cutter are tapered to form a continuously tapered surface along the bottom of the broach assembly. Upon passing the broach assembly through the slot, the assembly is progressively displaced in a radial outward direction to progressively cut the active dovetail slot surfaces. Shims may be disposed in the bottom of the slot to further displace the broach assembly radially outwardly in multiple passes.

Abstract: A broach assembly includes an elongated base having a central upward projection and a pair of side flanges and a tapered undersurface. Releasably mounted on the projection are multiple tool holders spaced along the length of the base. The tool holders mount cutters for engaging active surfaces of the wedge slot as the broach assembly is passed through the wedge slot. Shims may be interposed between the tool holders and base to increase the elevation of the cutting surfaces relative to the undersurface of the base to progressively increase the bearing pressure of the cutting surfaces against the active surfaces of the slot during multiple passes of the broach assembly through the wedge slot.

Abstract: An insert assembly is provided for a rotary machine wherein the rotary machine comprises a rotor and a casing. The rotor comprises a generally longitudinally-extending axis. The casing is generally coaxially aligned with the axis. The casing circumferentially surrounds and is radially spaced apart from the rotor. The insert assembly comprises a channel circumferentially disposed on the rotor and an insert circumferentially disposed in such channel such that the insert assembly is configured to thermally isolate frictional heat from the rotor to the insert.

Abstract: The broach assembly includes alternate spacers and cutters arranged in a sub-assembly having a lead at a leading end and a lag at a trailing end. The cutters have side margins in excess of the margins of the spacers for cutting material from the dovetail slots of the turbine wheel as the broach assembly passes through the slots. The bottom or apices of each spacer and cutter are tapered to form a continuously tapered surface along the bottom of the broach assembly. Upon passing the broach assembly through the slot, the assembly is progressively displaced in a radial outward direction to progressively cut the active dovetail slot surfaces. Shims may be disposed in the bottom of the slot to further displace the broach assembly radially outwardly in multiple passes.

Abstract: A broach assembly includes an elongated base having a central upward projection and a pair of side flanges and a tapered undersurface. Releasably mounted on the projection are multiple tool holders spaced along the length of the base. The tool holders mount cutters for engaging active surfaces of the wedge slot as the broach assembly is passed through the wedge slot. Shims may be interposed between the tool holders and base to increase the elevation of the cutting surfaces relative to the undersurface of the base to progressively increase the bearing pressure of the cutting surfaces against the active surfaces of the slot during multiple passes of the broach assembly through the wedge slot.

Abstract: A method of repairing a turbine rotor wheel having a damaged dovetail includes removing the damaged dovetail from the turbine wheel, leaving a turbine wheel body and welding a ring about the turbine wheel body in place of the removed damaged dovetail. During the welding process, including during preheating, welding or stress relieving, the temperature of the wheel body and ring is differentially controlled to introduce residual stresses in the ring. After welding a dovetail is formed in the ring for receiving turbine bucket dovetails. As a result, the ring has residual compressive stresses in a cold condition of the turbine whereby reduced net stresses in the ring in the location of the new dovetail during hot turbine operating conditions are reduced.

Abstract: A method of brazing a plurality of copper strands to a buss bar includes: a) cleaning the buss bar and the copper strands; b) positioning a filler shim on the surface of the buss bar; c) placing a copper strand on the filler shim, the filler shim and the strand having substantially equal lengths; d) stacking additional copper strands on the buss bar, with a filler shim between each adjacent pair of strands; and e) heating the filler shims utilizing an induction brazing coil to a temperature sufficient to cause melting of the shims and to thereby form a brazed lap joint between the copper strands and the buss bar.

Abstract: A repaired turbine rotor wheel includes a rotor wheel body having an outer rim. A forged ring is disposed about the outer rim and welded to the wheel body. A dovetail is formed in the ring, the arcuate weld between the ring and the wheel body being located radially inwardly of the dovetail.

Abstract: A method of repairing a turbine rotor wheel having a damaged dovetail includes removing the damaged dovetail from the turbine wheel, leaving a turbine wheel body and welding a ring about the turbine wheel body in place of the removed damaged dovetail. During the welding process, including during preheating, welding or stress relieving, the temperature of the wheel body and ring is differentially controlled to introduce residual stresses in the ring. After welding a dovetail is formed in the ring for receiving turbine bucket dovetails. As a result, the ring has residual compressive stresses in a cold condition of the turbine whereby reduced net stresses in the ring in the location of the new dovetail during hot turbine operating conditions are reduced.

Abstract: A method of repairing a turbine rotor wheel having an annular damaged dovetail includes removing the annular damaged dovetail from the turbine wheel, leaving a wheel body having a rim. A forged ring is welded to the rim and dovetails are formed in the forged ring to accommodate turbine bucket dovetails. The welding process including preheating, welding, and stress-relieving are performed while the rotor under repair is disposed in a lathe for rotation about a horizontal axis. The turbine rotor repair is accomplished from start to finish without displacing the rotor from the lathe.

Abstract: A method for weld repairing an article formed of a low-alloy steel, such as a steam turbine component. The method generally includes the step of depositing a first weld repair (14) on a surface of the article, during which a hard heat-affected zone (HAZ) (18) having a fine grain size is formed in the article beneath the surface on which the weld repair (14) is deposited. The first weld repair (14) and at least a portion of the HAZ (18) adjacent the first weld repair (14) are then locally heat treated at a temperature above a critical temperature A.sub.1 of the alloy from which the article is formed. As a result of this localized heat treatment, the original grain structures of the first weld repair (14) and the HAZ (18) are entirely replaced with a fine-grain structure with acceptable hardness. Thereafter, at least one additional weld repair layer (16) is deposited on the first weld repair (14).

Abstract: A method for repairing the rim of a steam turbine rotor, and a weld material for repairing such rotors. The method generally includes the steps of removing a damaged rim and its associated dovetail region, so as to form a surface at the perimeter of the rim portion. A weld repair region is then formed on the surface, which is machined to reconstruct the rim portion and the dovetail region exclusively with the weld repair region. Thereafter, an appropriately configured blade is secured to the rim portion with the dovetail region. The method is particularly intended for the repair of a steel alloy rotor, such as a NiCrMoV, NiMoV and CrMoV alloy, while the weld repair is formed with a nickel-base superalloy whose mechanical and thermal properties are compatible with the repair method and the steel alloy over a broad temperature range.

Abstract: A damaged turbine rotor wheel dovetail is repaired by cutting off the annular dovetail and welding a new forged ring onto the remaining wheel body. Fine-line welding is accomplished by inserting welding apparatus into grooves opening through axial faces of the wheel body and ring and rotating the rotor to provide multiple welding passes. Periodic ultrasonic inspection of the welds is provided by applying an ultrasonic transducer to the periphery of the ring to detect defects in the weld. To enable the transducer to operate at high welding temperatures, a manifold is disposed about the transducer defining a coolant cavity. Cooling medium is supplied the coolant cavity to maintain the transducer operable within predetermined temperature operating limits.

Abstract: The welding method for repairing a turbine rotor dovetail includes removal of buckets from damaged dovetails, removing a damaged dovetail from a turbine wheel, leaving a rotor wheel body having a rim. A plurality of ring sections are disposed about the wheel body rim, leaving axially opening annular grooves along opposite sides of the wheel. Welding apparatus including an electrode, welding wire and gas-carrying tube are inserted into the groove through an axial face of the wheel. One or more cover plates are disposed to overlie the groove at the location of its opening through the axial face of the wheel to at least partially seal the groove at its opening and maintain welding gas in the groove, enveloping the electrode and weld wire.

Abstract: A turbine rotor comprising a radially-inward portion of a steel alloy and a radially-outward rim portion circumscribing the radially-inward portion, the rim portion being formed by a weldment that includes a nickel-base superalloy region joining the rim portion to the inward portion of the turbine rotor, the nickel-base superalloy having a room temperature ultimate tensile strength of at least about 690 MPa.

Abstract: A method for weld repairing an article formed of a low-alloy steel, such as a steam turbine component. The method generally includes the step of depositing a first weld repair (14) on a surface of the article, during which a hard heat-affected zone (HAZ) (18) having a fine grain size is formed in the article beneath the surface on which the weld repair (14) is deposited. The first weld repair (14) and at least a portion of the HAZ (18) adjacent the first weld repair (14) are then locally heat treated at a temperature above a critical temperature A.sub.1 of the alloy from which the article is formed. As a result of this localized heat treatment, the original grain structures of the first weld repair (14) and the HAZ (18) are entirely replaced with a fine-grain structure with acceptable hardness. Thereafter, at least one additional weld repair layer (16) is deposited on the first weld repair (14).