Comprehensive Industrial Outage

Mechanical Dynamics & Analysis (MD&A) experts recently completed a comprehensive industrial outage for a customer. During the planned major outage, the work scope included inspection and repairs of their industrial steam turbine-generator unit.

The major inspection included disassembly, cleaning, inspection, performing recommended actions, and reassembly of the turbine, generator, and auxiliaries. The work scope also provided project planning, technical direction, supervision, tooling, craft labor, subcontract services, generator testing and inspection, high-speed balancing, controls and excitation checkout, as well as, balance engineering support for startup.

MD&A worked 24×7 through the disassembly, cleaning, and inspection phases to identify any needed repairs for discussion and approval from the customer in order to minimize schedule and cost impacts. During the non-destructive testing and inspection phase, 14 partitions required major repairs.

An MD&A Steam Path Specialist arrived on-site to complete a steam path audit including visual inspection of the rotor and buckets. Additionally, recommendations were made to replace the 1st & 2nd stage buckets during this outage and then replace stages 3 through 6 during the next major inspection. Besides the 1st & 2nd stage bucket issues, no other significant findings were noted. The turbine rotor was shipped to MD&A’s Turbine-Generator Repair Facility in St. Louis, MO for bucket replacement (Figure 1) and diaphragm repairs.

Figure 1. Stage 1 and 2 Buckets Removed and Dovetails Blast Cleaned

Part of the planned inspection included the removal of the upper and lower inlet nozzles to inspect the leading edges of the partitions and the shell. Full contact (100%) between the nozzle and shell is required and the onsite team used line boring equipment to skim cut and polish the shell nozzle to realign faces. Additionally, in order to ensure correct axial clearances, the nozzle was built up to offset any material removed during the shell boring and polish operations.

The nozzle segments were sent to our Turbine-Generator Repair Facility for cleaning, inspection, and minor repairs which included weld buildup of the sealing faces, stress relief heat treating, machining, and final grinding and polishing (Figures 2 and 3). The nozzle segments were then checked with a flat plate in an effort to ensure flatness and minimize the lapping time onsite need to achieve the final desired contact. Typically, priority is placed on the lower half nozzle so that it can be installed and steampath alignment started.

Figure 2. Upper Half Nozzle Partition Erosion

Figure 3. Machining Lower Half Nozzle

The valves were also completely disassembled and the onsite team completed dimensional and runout checks on the stems and bushings. Four inner and outer bushings were found to have excessive wear and MD&A Parts provided all necessary replacement components.

Inspection of the generator field journals revealed a moderate amount of imperfections, including radial scoring.  MD&A recommended machining both journals, including the hydrogen seal journals, and the collector rings.

The generator field was shipped to our Turbine-Generator Repair Facility for High-Speed Balance and journal repair & testing (Figure 4). Prior and after repairs and balance, incoming inspections were performed. MD&A Bearings, Seals, & Hydraulics supplied the new bearings and hydrogen seals.

Figure 4. Completed tool/hone/polish of the turbine end journal including the H2 seal area on the journal

After completion of assembly, locks (LOTO) were removed, and MD&A’s team supported system check-outs, and balance engineering support for startup.  Our experts submitted a comprehensive report for this comprehensive industrial outage.

MD&A is proud to have served the needs of the customer on inspection, repair, and parts replacement during the planned outage. The project was a total team effort with almost every division of MD&A contributing.

MD&A is a full-service OEM alternative for generator services, parts and repairs with a track record of hundreds of inspections on industrial units performed safely, in a quality manner on schedule and within budget all aimed at helping to ensure reliable unit operations.

Please call MD&A today for any industrial turbine-generator support needs, call us at (518) 399-3616, or use our Contact form.