{"id":78433,"date":"2026-05-28T12:09:06","date_gmt":"2026-05-28T16:09:06","guid":{"rendered":"https:\/\/www.mdaturbines.com\/?p=78433"},"modified":"2026-05-28T12:09:06","modified_gmt":"2026-05-28T16:09:06","slug":"quadruple-steam-turbine-generator-majors","status":"publish","type":"post","link":"https:\/\/www.mdaturbines.com\/es\/resources\/quadruple-steam-turbine-generator-majors\/","title":{"rendered":"Quadruple Steam Turbine-Generator Majors with Precision, Breadth, and Coordination"},"content":{"rendered":"

Mechanical Dynamics & Analysis (MD&A) has completed a quadruple Major inspection and repair of two steam turbine<\/a> systems and two gas turbine generators<\/a>, using the precision skills and state-of-the-art capabilities of its dedicated manufacturing, service<\/a>, repair<\/a> and parts<\/a> facilities.<\/p>\n

Coordination and comprehensive planning and scheduling were the pivotal keys to success of this complex work that included rings-off generator fields<\/a>, diaphragms<\/a>, steam turbine rotors<\/a>, valves and actuators<\/a>, and a variety of related items including parts supply.<\/p>\n

Consolidated scheduling, communication, accurate reporting and corporate-wide commitment flawlessly united to ensure customer and MD&A-wide confidence in this landmark achievement.<\/p>\n

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#4 HP Rotor<\/figcaption><\/figure>\n

Multiple Divisions<\/strong><\/h3>\n

The focal point was the one-stop shop, MD&A\u2019s Turbine Generator Repair Facility<\/a> in St. Louis, MO, and encompassed various divisions including Generator, Steam Path, Machining Services, as well as the Ohio-based Bearings, Seals and Hydraulics Division<\/a>.<\/p>\n

The precision-based and long-established service and manufacturing capabilities of MD&A joined forces to seamlessly complete each detail of this multifaceted and time-dependent outage.<\/p>\n

Scope <\/strong><\/h3>\n

Overall scope of work included inspection and repair of 9A4 and 7FH2 generator fields, two HP rotors, HP and IP diaphragms, spill strip supply and installation, two sets of valves and two sets of actuators, and critical parts supply.<\/p>\n

Generator <\/strong><\/h3>\n

Upon arrival in St. Louis, MD&A completed rings-off testing, inspection<\/a> and permanent blocking replacement of two steam turbine generator fields. Electrical testing showed unsatisfactory results and mechanical inspection indicated noticeable dishing of the collector rings. These would be honed and polished. Existing amortisseurs showed heat damage and axial cracking, requiring replacement by MD&A.<\/p>\n

Existing blocking was replaced with the MD&A strap and tie design. These unique axial blocks have spring forces acting in opposite directions to add interference to prevent any unwanted axial or radial movement of the blocking after installation.<\/p>\n

After repairs, the fields were moved to our high-speed balance facility<\/a> in St. Louis where heat runs with electrical testing were successfully completed. Fields were then moved to machining services for collector ring work scope, including hone and polish. The fields were then final inspected by the Generator Division before returning to site.<\/p>\n

Detailed recommendations were prepared for ongoing operation. In addition, MD&A recommended a full rewind at the next rings-off opportunity.<\/p>\n

The two gas turbine generator fields also received complete inspection and repair. Mechanical testing indicated noticeable dishing in the collector rings. Slot spring misalignment was found.<\/p>\n

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Top Hat Modification<\/figcaption><\/figure>\n

Blocking would be replaced with the MD&A strap and tie design. Inspection showed that vent holes for the coils were partially blocked, which can result in reduced hydrogen gas cooling flow, leading to thermal instabilities with the rotor leading to excessive rotor vibration and forced outages.<\/p>\n

Our experts performed a unique, patented 7FH2 generator field repair process (top hat modification<\/a>) that eliminated the axial migration of slot leaf springs that restricted the air flow. Collector rings were honed and polished to correct the dishing.<\/p>\n

The following components received non-destructive examination: snap rings, retaining rings, and field wedges. Because these gas-turbine units are hydrogen-cooled, pressure decay testing was performed.<\/p>\n

After machining services work was completed, fields were released to the high-speed balance facility, then to the Generator Division for final inspection and shipping preparation.<\/p>\n

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Unit Undergoing High Speed Balance<\/figcaption><\/figure><\/td>\n
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Unit Staged For Final Inspection<\/figcaption><\/figure><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
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Steam Turbine Rotors<\/strong><\/h3>\n

MD&A conducted detailed inspection and repair of the steam turbine rotors in St. Louis. Upon arrival the rotors were visually, dimensionally and non-destructively inspected. Repairs were conducted and detailed recommendations were made for long-term operation.<\/p>\n

Dimensional, run out and non-destructive evaluation (NDE) inspections (including metallurgical evaluations) yielded minor findings that were addressed. Minor indications were identified, reviewed and dispositioned. Low speed balance and a full quality inspection was completed prior to return to service.<\/p>\n

Minor repairs completed consisted of:<\/p>\n