The inspection revealed severe damage to the Stage 1A airfoils necessitating replacement of buckets. The Stage3 buckets were also replaced. For both rows, bucket hardware was supplied by MD&A and bucket covers were final machined to restore geometry.

In addition, both the L-1 stage & L-0 stage buckets and covers were replaced using material supplied by the customer. Our experts inspected the customer supplied buckets, confirmed critical criteria were met, provided consultation on a material substitution, performed the necessary activities to ensure properly balanced rows and machined bucket covers to restore geometry.

Additional rotor work included supply of a newly manufactured shrunk-on thrust collar and machining of the T1 journal. The overspeed trip was removed and tested by MD&A’s Bearings, Seals & Hydraulics Division. Experts also polished the 11th stage bucket admission edges to remove foreign object debris.

Inspection of the stationary components of diaphragms and packing boxes found some with excessive pitting on the packing groove axial steam seal faces. The seal faces were skim cut and custom packing was installed for these diaphragms and packing boxes. New spill strips were installed and machined for these same diaphragms.

Several diaphragm horizontal joints were weld repaired and restored to address joint indications and erosion damage. The nozzle bolt hole peening grooves were weld repaired, stress relieved and re-machined. The nozzle admission face was weld repaired, stress relieved and machined to restore axial clearance.

Finally, an inspection of the Curtis ring discovered it was out of round. The Curtis ring peening grooves and seal grooves were weld repaired and re-machined. The Curtis ring was bolted to the nozzle discharge face and stress relieved after the weld repairs were completed. This re-rounded the Curtis ring to fit into the nozzle tongue and groove fit. The Curtis seals were replaced and machined on-site with a boring bar to restore design specifications.

These complex and intricate steps were accomplished in minimal time thanks to the skilled experts at our St. Louis Turbine-Generator Repair facility. Our customer’s turbine was back in use with a short downtime and running again at optimum efficiency.

Have MD&A look at your turbine rotor today! Call our Turbine-Generator Repair Facility at (314) 880-3000 or use our Contact form.

The post Bucket and Thrust Collar Replacement appeared first on MDA Turbines.

Motoring is the mode of turbine-generator operation during which the generator acts as a synchronous motor, taking energy from the grid to drive the turbine at operating speed. Motoring can be problematic, however, because the rotor blades are moving at a high velocity without the steam to keep the last stages of the LP rotor cool. MD&A’s engineering and technical expertise provided cost-effective solutions for a power plants after such damage.

The power plant customer expected to find damage in the LP section because of the motoring event. MD&A performed an on-site steam path damage assessment. Damage to the DFLP rotor was noted, and the customer sent the rotor and inner cylinder to the MD&A’s Turbine-Generator Repair facility in St. Louis.

During the rotor inspection, both the governor end and generator end L-2 blades were found to be twisted. A governor end L-1 blade had a large crack emanating from the admission edge just inside of the lashing lug. Multiple covers were missing from the generator end L-1 blades. This caused heavy foreign object damage to both the generator end L-1 blades and tenons, and L-0 blades.

This damage led to reliability concerns with the L-0, L-1, and L-2 blades so the best solution to ensure the rotor’s future reliability was to replace all six blade rows.

Roundness and horizontal joint gap checks were performed as part of the LP inner cylinder inspection, and the bore was found to be elliptical. MD&A machined the horizontal joint to decrease the out of roundness and close up the horizontal joint gaps, as well as, machined the bore to increase clearance.

Once the LP rotor repairs were completed, the rotor was balanced in MD&A’s high speed balance facility. During the balance, a sudden shift in the rotor imbalance occurred. It was determined that the coupling shifted when the rotor was tested at 110% of its rated speed. After consulting with the customer, MD&A removed the coupling and performed a full inspection.

MD&A experts found that the rotor did not have a hole for the coupling radial pin. In fact, the pin was making contact with the outside of the shaft. Once the coupling keys were removed, the coupling was found to have shifted.

The evidence suggested that the coupling was subjected to a large amount of torque during the motoring event and that this caused the coupling to shift. If it were not high speed balanced in a controlled environment, these coupling issues would not have been identified until the unit was reassembled and put back into operation, at which time the customer would have experienced extensive delays and costs to fix the issues.

The coupling was then re-installed onto the rotor, a hole was drilled into the shaft for the radial pin, new keys and a new pin were manufactured and installed, and the coupling face, rabbet fit, and outer diameter were re-machined. This allowed for the proper balancing of the rotor.

This project is just one of the many examples of MD&A’s expertise to fix difficult rotor issues.

Have MD&A look at your turbine rotor today, call our Turbine-Generator Repair Facility at (314) 880-3000 or use our Contact form.

The post Turbine Blade Replacement appeared first on MDA Turbines.