January 1, 2010

Replacing an HP/IP Rotor

Mike Jirinec and James Heeter

The Replacement Rotor

The rotor forging sections were brought into the Richmond facility, set up and machined in the mill, and then the lathe was used to produce the join welding surfaces. After heat treatment of the welded rotor forging, the rotor’s wheels, dovetails, gland seals, and journals were completely machined. The coupling, balance weight holes, and steam balance holes were machined as part of the milling work (Figure 2).


2. Less is more. Forgings for the IP (shown here) and the HP sections were rough-machined prior to final weld preparation. Courtesy: Alstom Power

The rotor dovetails were then shot-peened. The newly manufactured blades were installed, shrouds were manufactured and installed, and shroud covers were machined. The rotor was first balanced at operating speed and then at 20% overspeed. The replacement rotor was rebuilt from scratch in only six months, and the unit was quickly restored to service (Figure 3).


3. Final touches. Final machining of the complete rotor is in shown in progress. Courtesy: Alstom Power

During a six-month period, two turbine forgings were join-welded and modified by weld build-up to the configuration of the existing rotor. Not only was extensive machining and weld build-up involved, but instead of refurbishment, all 17 rows of new blades (a total of 1,492 blades) were also manufactured and installed to replace the HP and IP straddle roots for the turbine rotor.

Such a solution provides steam turbine owners significant potential cost savings when compared to normal delivery cycles for a new fully bladed turbine rotor; it also avoids considerable purchased power costs.

— Contributed by Mike Jirinec, proposal manager, and James Heeter, business development manager for Alstom Power.