A detailed incoming inspection was performed for the HP/IP and LP rotors and found relevant indications in the LP rotor steeples at L-1 (stage 20) through magnetic particle inspection, in addition to minor damages identified on the HP/IP rotor.

Finding indications in the last-stage LP rotor steeples (also known as fir-tree grooves) is a common issue.  Basically, the steeple indications are caused by corrosion fatigue (when a material degrades due to the combination of corrosion and cyclic stresses).

Repair of the LP rotor included removal of the L-1 steeple indications by hand tooling, followed by blending and polishing. There were 3 steeple indications that were noticeably deeper than the rest. The approximate depth of these deeper indications was 3 mm (0.12”) located on the convex side of the steeple.

A finite element analysis was performed to verify the structural integrity of the steeples after grinding. Based on the analysis, the L-1 steeple repair was found to be acceptable. After all rotor repairs were complete, the rotors were balanced, and the journals were strapped lapped prior to leaving the workshop.

Incoming inspections were also completed on the HP/IP and LP diaphragms.  The HP/IP diaphragms arrived at the workshop with the lower half appendages removed for reverse engineering. Minor damages were noted on the LP diaphragms including horizontal joint erosion and foreign object damage to the partition trailing edges on all stages, as well as damage to the steam seal face on stages 17-21.

Repair work to the HP/IP diaphragms included installing new appendage rings with honeycomb seals, which were supplied by MD&A Parts.  To ensure proper fitting, the appendage and bore packing fit diameters were machined round prior to the installation of the new appendages. Additionally, the dowel pins were removed, and the horizontal joint was skim cut.  Dowel pin holes were then enlarged, and oversized dowel pins were installed.

New bore packing (with honeycomb seals) for stages 2-9 and 11-15 were also supplied by MD&A Parts.  The bore packing was test fitted after appendage installation.

Minor repairs were performed on the LP diaphragms including horizontal joint weld repairs and removal of broken studs. After all diaphragm repairs were complete, new horizontal joint hardware was supplied by MD&A Parts and test-fitted before the diaphragms left the workshop.

Through MD&A’s state-of-the-art repair facility and quick access to replacement parts, an extensive inspection and necessary repairs were completed by our experts in a timely manner that allowed the unit to be quickly returned to the site.

Call MD&A today for any turbine repair at +1 (314) 880-3000 or use our Contact form.

The post Rotor Steeple Indications and Diaphragm Repairs appeared first on MDA Turbines.

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.

During their planned major inspection, the utility decided to remove the rotor based on prior recommendations from past borescope findings.

Upon inspection, our gas turbine experts discovered that the Row 1 turbine wheel showed indications of heavy wear caused by rubbing to the rear face of the discourager seal. To repair this, the seal area was prepped and built up using a spray metallizing process.

Once the precise build-up was achieved, the seal area was ground to the correct dimensions and contours. In addition, wear damage to the Row 2 turbine disc sealing area was repaired to achieve an acceptable surface after a fluorescent penetrant inspection was completed.

Experts also performed compressor blade blending from wear damage/FOD to all compressor blade rows. One Row 16 blade was removed and replaced, and non-destructive testing was performed on the repaired rotor.

Progressive balance work was completed on two turbine bucket stages. MD&A experts replaced both stages of buckets.  

Our experts also performed the modification to the gas turbine rotor which involved machining the thrust runner face that is located at the No. 1 bearing. This is a common recommendation for the Frame 5 fleet to improve the reliability and operation of the thrust bearing.

Skilled technicians from MD&A’s Bearings, Seals, and Hydraulics Division re-toothed the rotor’s oil deflectors and re-babbitted the bearings.

New replacement buckets were provided by MD&A Parts. The rotor was progressively low speed balanced as the 1st and 2nd stage buckets were installed, technicians secured balance weights and completed the six-point residual unbalance test.  The rotor was then packaged & secured on the shipping skid.  Finally, MD&A transported the rotor to site and successfully supervised the re-installation.

MD&A’s specialized services range from Combustion, Hot Gas Path, and Major Inspections to Compressor & Turbine Rotor Repairs and End of Life inspections. MD&A offers a complete suite of parts, repairs, and services solutions for the Frame 5 gas turbine fleet.

Call our MD&A Gas Turbine Services today at (518) 399-3616 or use our Contact form

The post Frame 5 Gas Turbine Rotor Repair appeared first on MDA Turbines.

Power plant owners face a major challenge of keeping aging turbines up and running — efficiently and cost-effectively. MD&A is uniquely prepared to meet this challenge. We have the experience and expertise to solve your plant’s problems.

A failure of the N-1 retractable packing assembly ground a groove in the rotor shaft at the hi-low packing diameter. Also, during a restart, the rotor ramp rates were violated, causing the shrunk on wheels to shift.

The rotor was received at MD&A’s Turbine-Generator Repair Facility in St. Louis with severe damage to the stage 3 and 4 wheels and the N-1 packing area.

The rotor repairs consisted of the following work:

• Thermodynamic evaluation of operating without the 3rd and 4th stage wheels.
• Destructive machining removal of the 3rd & 4th stage wheels.
• Metal spray buildup of the outboard thrust collar shaft fit area to restore the shrink fit.
• A sleeve repair to the N-1 packing area.
• Straightening, benching back, and polishing the stage 9 leading-edge airfoils.
• Replacement of Qty (4) lifted shroud covers on stage 9 by tenon weld restoration.
• A brazing repair of blade tie wires.
• Supply and installation of new packing segments in the N-1 packing box.
• Reassembly and final inspections of the rotor.
• High-speed balance of the rotor.

MD&A provided a sleeve modification option to repair the damaged N-1 shaft-packing area. The sleeve modification repair included machining of the rotor shaft end to remove the damaged N-1 hi-lo teeth, machining of the shaft to allow for the installation of a new threaded-on sleeve, and final machining of the N-1 hi-lo teeth back to their original position and diameter.

After the N-1 machining modification was complete, the turbine end shaft end components were reassembled. Once assembled, final axial dimensional checks and runouts were performed.

The customer’s primary concern was returning the unit back to service in the most expedited manner, and MD&A fulfilled their needs.

Because of our vast knowledge with many years in the industry and with different types of OEMs (Original Equipment Manufacturers), MD&A experts are capable of performing any steam turbine rotor repairs. We are your full-service turbine-generator service provider. No matter what the problem, MD&A’s experts have the solution!

Let MD&A perform your Steam Turbine Rotor Repairs today, call our Turbine-Generator Repair Facility at (314) 880-3000, or use our Contact form.

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