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

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

Multiple Divisions

The focal point was the one-stop shop, MD&A’s Turbine Generator Repair Facility 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.

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.

Scope

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.

Generator

Upon arrival in St. Louis, MD&A completed rings-off testing, inspection 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.

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.

After repairs, the fields were moved to our high-speed balance facility 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.

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

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.

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.

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

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.

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.

Steam Turbine Rotors

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.

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.

Minor repairs completed consisted of:

• Rabbet fit restoration via peening and machining
• Minor bucket repairs were completed by MD&A’s expertly trained bucket technicians
• Deburring and cleaning to remove any stress riser concerns, and
• Low speed balance

All detailed data inspections, repairs and as left conditions, including future repair recommendations were included in final reports to support future planning.

Valves

Example valve repairs, following complete inspection, included the following:

1. Main Stop Valve
   1. Installed new stem & anti-rotation key
   2. Lapped the pressure seal head backseat to achieve a 100% blue contact check
   3. Installed a new stem/disc nut anti-rotation pin and staked, torqued and blue checked to the disc
   4. Machined the pressure seal head gasket face to correct runout and true it to the bushing bore
   5. Ground & polished the main disc seating surface to remove runout and surface imperfections

2. Control Valve
   1. NDE revealed indications in the nitride around the disc OD, a new disc was purchased and installed
   2. New disc nut anti-rotation pin for the was installed and staked into the new disc

3. Turbine End Reheat Stop Valve
   1. Honed pressure seal head bushing tight spots to restore design clearance to the stem
   2. Lap the pressure seal head backseat to achieve a 100% blue contact check
   3. Performed a weld buildup on the pressure seal head casing fit and machined to restore clearance to the steam chest on-site
   4. Machined the pressure seal head gasket face to correct runout and true it to the bushing bore
   5. Ground & polished the main disc seating surface to remove runout and surface imperfections
   6. Installed a new stem anti-rotation pin
   7. Installed a new disc cap bolt

4. Generator End Reheat Stop Valve
   1. Honed the disc bore to restore design clearance to the stem
   2. Honed pressure seal head bushing tight spots to restore design clearance to the stem
   3. Lap the pressure seal head backseat to achieve a 100% blue contact check
   4. Machined the pressure seal head gasket face to correct runout and true it to the bushing bore
   5. Ground & polished the main disc seating surface to remove runout and surface imperfections
   6. Installed a new stem anti-rotation pin

5. Intercept Valve #1
   1. Honed the disc bore to restore design clearance to the stem
   2. Restored the split ring ID to stem OD design clearance and verified
   3. Ground the split ring face in the surface grinder to restore the design stem lift
   4. Stoned the seal ring face to restore the axial clearance upon valve reassembly
   5. Ground & polished the main disc seating surface to remove runout and surface imperfections

6. Intercept Valve #2
   1. Honed the disc bore to restore design clearance to the stem
   2. Restored the split ring ID to stem OD design clearance and verified
   3. Ground the split ring face in the surface grinder to restore the design stem lift
   4. Stoned the seal ring face to restore the axial clearance upon valve reassembly
   5. Ground & polished the main disc seating surface to remove runout and surface imperfections
   6. Installed a new seal ring bolt

At MD&A’s Bearings, Seals and Hydraulics in Ohio, two sets of steam turbine valve actuators (Rexroth and MOOG) were completely refurbished. The refurbishment included disassembly, cleaning, and inspection of all components. All soft parts and sealing parts were replaced, and in some instances some critical components were replaced, and this includes the following: large disc springs, piston shafts, servos, solenoids, LVDT components, packing glands, bushings, piston rings. Additionally, some components were restored using chrome and grind restoration methods to reestablish critical dimensions.

After repairs were complete the actuators were re-assembled, fluid flushed and tested at 110% operating pressure with the same fluid used at site. This ensures that the actuators function properly and ensures that the actuators are leak free during operation.

This testing greatly reduces the need for field troubleshooting and adjustment on site during start-up.

Explore the Benefits of MD&A

These Steam Turbine-Generator Majors and repairs led to their life extension, continued operation and longevity of the plant in the future.

Mechanical Dynamics & Analysis enjoys a firmly-established global reputation as a reliable and trustworthy non-OEM service firm with deep roots in all major OEM products and developments. MD&A’s professionals are up to date on all industry issues and offer these benefits:

• Comprehensive service and precise coordination.
• Multi-talented MD&A personnel in multi-faceted long-established facilities.
• One-stop gas turbine, steam turbine and generator point of contact for estimating, scheduling and project execution.
• Long-term operating assurance and operating guidelines for the owner/operator.
• All backed by MD&A’s world-class corporate commitment.

No job is too complex for MD&A. To discuss and schedule your next turbine generator service and repair project, contact the experienced professionals at MD&A. Call us at (518) 399-3616 today or use our contact form.

The post Quadruple Steam Turbine-Generator Majors with Precision, Breadth, and Coordination appeared first on MDA Turbines.

The gas turbine bubble of 2000 to 2004 saw between 600 and 700 GE installed across the U.S., with approximately 900 7EA units in operation worldwide. Two decades later, those units are converging on a common problem: rotor end-of-life. With the fleet facing a 144,000-hour, 5,000-start threshold set by the original equipment manufacturer (OEM), and with superalloy forging lead times stretching into years, the math presents a supply chain challenge that no single provider can solve alone.

MD&A, a Mitsubishi-owned company historically focused on steam turbines, recognized this convergence early. Beginning in the early 2010s under then-CEO John Vanderhoef, the company made a strategic pivot toward gas turbines, targeting the 7FA and 7EA frames specifically because of the sheer volume of installed units.

“When you want to get into a new industry, you focus on what investment to make based on what opportunities are out there,” said Dave Fernandes, MD&A’s Gas Turbine Program Manager. “The 7FA, and additionally the 7EA, were the two units of focus based on the sheer number of opportunities out there.”

Starting from Zero Hours

The foundation of MD&A’s reverse engineering effort was the acquisition of a 7FA.03 gas turbine & 7EA gas turbine, both of which had never been fired. Kevin Roy, MD&A’s Principal Engineer, Parts, who led much of the reverse engineering work, explained why zero-hour components were essential.

“You need something that is exactly as it was produced,” Roy said. “Those parts having not run, they’re exactly as they left the machine shop and left the factory. You don’t want to have to worry about how parts have worn over time or if they’ve deformed, trying to back into what it could have been.”

The reverse engineering process involved far more than dimensional scanning. Teams employed a combination of hand tools, coordinate measuring machines (CMM), and blue light scanning to capture geometry. But critical characteristics like coatings, shot peening, and surface finishes required hands-on expertise that no laser could provide.

“It takes a lot of expertise and experience to understand what a coated part looks like versus a shot-peened part, what surface finishes are—all things that you’re not going to get from a laser scan or from a CMM measurement,” Roy noted.

Material characterization came from separate used components that could be destructively tested, while the unfired parts provided pristine geometric references. MD&A’s parent company provided metallurgical support and testing capabilities that proved essential during the development phase.

Building a Global Supply Chain

Creating detailed production drawings was only the first step. MD&A then had to identify vendors worldwide capable of producing forgings and machining the high-temperature alloys used in turbine sections to the required tolerances and surface finishes.

“This is very niche capability within the world,” Roy said. “We had to search the globe for vendors that were capable.”

The company evaluated both internal resources and external suppliers, optimizing the supply chain for quality rather than convenience. MD&A continues to expand its vendor network to provide redundancy for critical components.

Quality control operates on multiple levels. First-article inspections received intense scrutiny, but that rigor extends to ongoing production. Jason Wheeler, MD&A’s Gas Turbine Rotor Repairs General Manager, described the verification process. “We lean on our vendors that we’ve gained this experience and relationship with, but then we also check the parts when they show up in the shop,” Wheeler said. “We’re probably providing more scrutiny than these vendors might be doing for other similar parts. We’re pushing quality as high as possible.”

The Seed Rotor Strategy

MD&A’s approach centers on minimizing customer downtime through a seed rotor exchange program, a model the company already operates successfully for 7FH2 generators. Rather than having customers wait while their rotor undergoes inspection and refurbishment, MD&A aims to maintain ready-to-install rotors that can be exchanged, limiting outages to the time required for removal and reinstallation.

“The downtime for customers that come our way for rotor life extensions only involves disassembly, putting the turbine on a half shell, removing the rotor, putting it on stands, taking the rotor that we’re providing, putting it into the unit, reassembly, and startup,” Fernandes explained.

The returned rotor then enters MD&A’s refurbishment cycle, eventually becoming available for the next customer. Recognizing that lead times can stretch for years, the company maintains strategic inventory of the components most frequently replaced during life extensions.

The Convergence Problem

The urgency for operators to plan ahead stems from a convergence of factors. Between 800 and 900 7FA units in MD&A’s target market are approaching or have reached their rotor life limits within roughly the same timeframe. The superalloy forgings needed for life extension carry multi-year lead times. And only a handful of facilities worldwide have the specialized equipment and capabilities to service these large gas turbines.

“The number of units, coupled with the long-lead-time parts, coupled with limited shop space in the world are the three prongs which should give customers some angst and make it a high priority to get out in front of their rotor life extension needs,” Fernandes said.

The situation is compounded by the data center boom driving increased utilization of existing gas turbine assets. Units that operators might have expected to run intermittently are now logging hours at higher rates, accelerating the timeline to end-of-life thresholds.

Wheeler emphasized that customers who wait for a forced outage to address rotor issues face the worst outcomes. Added Roy, “If you know you need a rotor in three to five years, it starts getting built today. These are not parts that get built in a week. These are parts that take multiple years to be produced.”

Proving the Concept

MD&A has completed several 7FA & 7EA rotor end-of-life inspections and refurbishments, but the 7FA.03 rotor currently in the St. Louis shop represents a milestone. It’s the first 7FA.03 rotor purchased specifically for the company’s seed rotor program to go through the full production cycle with newly manufactured MD&A components integrated alongside serviceable original parts.

“There’s a fear that what you’ve done over the past 10 years is not going to line up, not going to be correct, not going to mate up to old-run mating components,” Wheeler acknowledged. “On the rotor that’s stacked right now, there are a couple of new wheels intermixed in the middle of a compressor with a bunch of old wheels. They mated up to the old wheels perfectly—as expected and designed.”

MD&A has delivered a life-extended 7FA.03 rotor to a leading power producer in 2026. In a highly risk-averse power generation market, a major owner’s decision to partner with MD&A and move forward with this deployment underscores strong confidence in both the 7FA Rotor Life Extension program and MD&A’s ability to execute it end-to-end.

The successful integration validates MD&A’s decade-long investment and positions the company to offer utilities an alternative path for extending the life of their 7FA & 7EA fleet, one that doesn’t depend solely on OEM capacity and timelines. For operators running 7FA & 7EA gas turbines beyond their original design life, the message from MD&A is clear: the time to plan is now, because the forgings needed three years from now need to enter production today.

The post MD&A Positions Itself as Alternative Source for 7FA & 7EA Gas Turbine Rotors appeared first on MDA Turbines.

In the power generation industry, reliability and efficiency are paramount. Gas turbines, such as the 7FA series, are critical assets for utilities, and their performance directly impacts grid stability and profitability. Periodic major inspections are essential to ensure these machines operate within OEM specifications and maintain compliance with environmental and safety standards.

For this combined project, MD&A provided all tooling, supervision and labor to perform the outage work scope.

• 7FA Gas Turbine Overhaul: Complete disassembly of the compressor, combustion, and turbine sections for inspection and refurbishment.
• 7FH2 Generator Inspection: Disassembly and electrical testing of the 7FH2 generator, including stator and field assessments.
• Technical Information Letters (TILs): All TILs were completed.

As part of the outage, the inlet filter house and ducting were visually inspected internally down to the inlet plenum and confirmed to be in sound operating condition.

A customer-supplied, refurbished gas turbine rotor would be installed after MD&A inspection.

Arrival

Once onsite, tooling preparation and disassembly began, working two shifts. All as-found clearances were measured, and initial alignment checks were completed.

Turbine compartment scaffolding and field stands were installed, and preparations were made for removal of both the gas turbine rotor and the generator field.

Throughout disassembly, all reusable materials were identified, stored, and prepared for reuse.

7FA Gas Turbine

Following turbine casing and bearing removal, compressor component inspection and repairs began. Inlet guide vanes (IGVs) were inspected and would be returned to service. IGV inner bushings and spring/thrust washers were replaced. Bearings were replaced as needed.

Oil deflectors and seals were prepared for shipping to MD&A Bearings, Seals and Hydraulics Division in Ohio for inspection and repair. New seals would be required.

Stator compressor blades S1-4 and S5-8 were worn and replaced. Several rows exhibited foreign object damage (FOD) and casing pinch marks, requiring precision blending and vane replacement.

For the combustion section, chamber components revealed wear and coating damage. MD&A experts replaced the following with either new or refurbished parts: liners, flow sleeves, crossfire tubes and retainers, liner caps, FWD cans, TP bull horns and transition pieces. Check valves were also replaced. Fuel nozzles were swapped and flow-tested to ensure proper atomization.

For the hot gas path, First-, second-, and third-stage buckets and nozzles were installed with concentricity and clearance checks verified against OEM tolerances. For the exhaust, flex seals were replaced with new pins installed, and the diffuser was weld-repaired.

A new Bearing T1 was replaced. T3 and T4 bearings were also transported to MD&A Bearings, Seals and Hydraulics division in Ohio, refurbished, returned, and reinstalled. The T1 thrust journal was also replaced.

Degraded gaskets were replaced in the discharge casing, and the casing received blend repairs.

7FH2 Generator

At project start, generator shaft jacking devices and eyebrows were installed. Our team constructed our generator field support platform to allow for easy removal of the field when performing this 7FH2 Generator Major Inspection.

This system addresses the unique challenges associated with the 7FA/7FH2 configuration:

1. The shaft centerline height is 13 feet above machine baseline (grade)
2. The gas turbine inlet ducting and filter house limit crane access.

MD&A’s team removed the turning gear and disassembled the journal bearings, and shipped them to MD&A Bearings, Seals and Hydraulics division in Ohio for refurbishment. Oil deflectors and hydrogen seals were also prepared for shipment.

After end shield and fan blade removal, MD&A experts removed the generator field for covered storage on the turbine deck. The field was inspected, and field windings were found to be clean.

The generator end shields and gas shields were inspected, cleaned, and returned to service.

MD&A performed high-resolution borescope visual inspection of normally inaccessible areas on the generator, outside of the bore region. These areas include under the collector and turbine end retaining rings and the stator end windings, field coil end turns, auxiliary components and stator terminal connections.

The generator stator received visual inspection, insulation resistance testing, winding resistance measurements, DC leakage and RTD tests, and wedge inspection. The field received visual inspection, insulation resistance testing, winding resistance and impedance tests, and turn-to-turn pole balance.

T3 and T4 H2 casings were removed, visually inspected and sent to MD&A Bearings, Seals and Hydraulics division for further inspection and repair. New seals would be installed with refurbished casings.

New T3 and T4 lift oil lines were installed.

Stator testing revealed that more than one-third of the wedges were loose and/or hollow. MD&A experts therefore performed a complete rewedge on the generator stator. A full stator wedge tightness survey map followed.

The new turning gear was installed and aligned, followed by the hydrogen leak check. The gas turbine/generator load coupling was aligned to OEM specifications.

Rewedge on the Generator Stator

Completed Stator: New Rewedge, Painted

Startup

Precision alignment was critical to minimize vibration and extend component life. Rim/face checks were performed and coupling bolts were replaced.

The unit was started on schedule and tuned with no issues.

Long-term recommendations to increase owner/operator confidence in continued operation included monitoring of the T3 area, ongoing inspections of variable inlet guide vanes, filter house visual and mechanical checks (with specific details), water washing frequency, and monitoring CDC (compressor discharge casing) slip issues.

MD&A’s multi-divisional team of experienced technicians and product experts successfully completed the GE 7FA gas turbine major inspection and 7FH2 generator major inspection on schedule. The project demonstrated MD&A’s ability to coordinate cross-divisional resources and execute complex inspection and repair scopes. Detailed recommendations were also provided to support long-term reliability, giving the customer assurance of a well-executed outage and confidence in future full-service operations.

For service of any generator regardless of original design, contact the premier non-OEM service provider to the global turbine-generator market. Call us at (518) 399-3616 today or use our contact form.

The post 7FA Gas Turbine and 7FH2 Generator Major Inspections appeared first on MDA Turbines.

View our video and then call MD&A’s Turbine and Generator Controls Division today at (970) 224-2223 or use our Contact form.

Benefits to Your Operation:

• Reduce unplanned downtime
• Improve reliability and asset longevity
• Optimize maintenance schedules
• Enhance situational awareness
• Support outage planning with AI insights

Key Features:

• Industry-Leading Support Network: With over 40 years of trusted expertise, MD&A specialists are equipped to deliver unmatched support across the energy and industrial landscape.
• Continuous Monitoring: Our system uses live data from rotating assets ensuring uninterrupted visibility into plant health and performance.
• Enhanced Operational Efficiency: By integrating advanced digital control systems and predictive analytics, our engineering solutions optimize performance, boost fuel efficiency, and extend equipment lifespan.
• Cybersecurity and Compliance: Our Monitoring and Diagnostics Center delivers a robust, multi-layered cybersecurity framework that safeguards assets and ensures compliance with industry standards.

Empowering Reliability Through Innovation: As part of the Turbine and Generator Controls Division, our Monitoring and Diagnostic Center, located in Fort Collins, Colorado, delivers safe, modern, and effective solutions tailored to meet evolving operational and regulatory demands.

Our Monitoring and Predictive Maintenance Service marks a significant advancement in remote monitoring and analytics for the power generation sector. Designed to enhance plant reliability, efficiency, and sustainability, this service provides comprehensive support that helps operators stay ahead of potential issues, optimize performance, and extend asset life!

The post Remote Monitoring Video appeared first on MDA Turbines.

MD&A has an inventory of new or refurbished generator fields in our field exchange fleet, featuring the latest in rewind technologies. Additionally, we have stator rewind kits with stator bars available in stock, ready to support planned or forced outages.

Disassembly and Component Inspection

MD&A’s experts disassembled the generator and inspected critical components in the process.

Our team conducted visual and non-destructive examinations (NDE) on the load coupling Riverhawk bolting. No indications were found – all components successfully passed VT and UT requirements before being returned to service. The unit’s generator bearings were also inspected dimensionally and visually by our technicians before being sent to MD&A’s Bearing, Sealing and Hydraulics Division for refurbishment and sizing to ensure proper fit for the new field journals.

Rotor fan blades were removed, hand-cleaned, and subjected to NDE and visual inspection before being returned to service with new locktabs during the final installation. Hydrogen seal components were also examined, with MD&A providing new seals properly sized to the refurbished rotor configuration and lapped to the refurbished gland specifications.

Our technicians sent the H2 gland seals to MD&A’s Bearing, Sealing and Hydraulics Division for segment replacement and housing refurbishment. Oil deflectors were  modified for insertable teeth design before being reinstalled and aligned to shaft specifications. In addition, our experts removed and replaced the old seal carrier.

Stator Rewind

During this planned outage, MD&A’s team performed a full stator rewind. Our onsite experts performed baseline and post-disassembly ELCID testing to assess stator core iron integrity, with all results indicating acceptable lamination condition. The existing opposing wedge system was then removed by the team.

Our personnel removed series loop connections, circuit ring connections, and top and bottom bars. Core compression flange nuts underwent breakaway torque verification. Several nuts were found to be well below OEM specifications. Our team cleaned the mating surfaces and retorqued all nuts.  Following core tightening, the belly bands were tightened with new shim packs installed.

New 7FH2 bars were installed with proper alignment verification. Our technicians completed electrical testing, which included hi-pot tests at specified voltages, with all phases achieving resistance results within target ranges.

Impressively, this all was completed within 21 days. MD&A has a consistent track record of handling rewinds of this complexity, including core and belly band tightening, within the same timeframe.

Field Spare Rewind

Our team also conducted a field rewind on the 7FH2 generator field. Our technicians disassembled the unit, which included removal of the bore copper and collector rings. The field forging underwent media blasting and comprehensive non-destructive examination (NDE), including magnetic particle testing on the field body and penetrant testing on wedges and retaining rings. All NDE results were satisfactory.

During reassembly, our generator experts installed newly insulated bore copper, main lead studs, and coil components in a controlled, clean room environment. Each coil underwent individual electrical testing before installation and clamping. The field completed a successful bake cycle during which the coils were compressed to their specified diameter via bake clamps.

Throughout the rewind process, MD&A’s engineers performed thorough electrical testing. These tests included: insulation resistance, polarization index, AC impedance, winding resistance, as well as repetitive surge oscillation (RSO), turn-to-turn testing, pole balance, and AC hi-pot. Once fully wound, the field was then high-speed balanced, which included a heat run before the unit was staked, painted, and wrapped for storage.

Reassembly and Alignment

The arrival of the refurbished generator field marked a pivotal moment in the outage. Our team constructed our generator field support platform to allow for easy install of the field. This system addresses the unique challenges associated with the 7FA/7FH2 configuration: 1) the shaft centerline height is 13 feet above machine baseline (grade), and 2) the gas turbine inlet ducting and filter house limit crane access.

During reassembly, MD&A’s technicians performed a 16-point turbine-to-generator alignment. The stator was repositioned to meet OEM specifications. The newly rewound replacement field was then carefully set into place, followed by the installation of lower half bearings with precise tilt and twist measurements recorded.

All of the generator’s systems were returned to service with proper clearances and operational parameters verified.

Conclusion

This multi-faceted scope, including a 7FH2 generator field replacement and full stator rewind, demonstrates the technical complexity and precision required for successful power generation equipment maintenance.

The project required specialized expertise across multiple disciplines. Our ability to coordinate these complex activities with our expert knowledge of OEM specifications and decades of field-proven success exemplifies why power generation customers worldwide rely on MD&A to keep their assets operating reliably.

Call us at +1 (314) 880-3000 today or use our contact form.

The post 7FH2 Generator Field Replacement with Stator Rewind appeared first on MDA Turbines.

The HPIP section features six high-pressure impulse stages, and six intermediate-pressure reheat stages in an opposed flow configuration. Over time, thermal cycling, mechanical stresses, and environmental conditions had contributed to severe cracking in the integral valve chest of the lower half shell, along with additional minor and moderate indications throughout the upper and lower shells.

Comprehensive Scope of Work

MD&A’s experts began by preparing a detailed “as-found” inspection of the HPIP outer shells. This initial assessment revealed not only the originally defined severe cracking in the valve chest but also several additional minor and moderate internal and external shell indications. The scope quickly expanded to include:

• Excavation and weld restoration of the original valve chest severe cracks.
• Grinding, blending, and welding of newly discovered moderate indications across both shell halves.
• Employing proven and proprietary distortion control measures during the welding.
• Post weld heat treatment (PWHT) to relieve residual stresses and restore metallurgical integrity.
• Final nondestructive surface and subsurface examinations (NDE) and hardness testing to validate the repairs.
• Dimensional inspections to assess shell geometry and fit-up conditions.
• Reinstallation and welding of small bore piping, removed to gain access for the major weld repairs.

This multi-phase repair required precise coordination, advanced welding techniques, and rigorous quality control to meet OEM specifications and ensure safe and reliable operation.

The lower half shell presented the most significant challenges. In addition to the original valve chest severe cracking, MD&A identified eight minor internal indications and four moderate external indications. While the minor indications were accepted and documented for future evaluation, the moderate ones were excavated and prepared for weld restoration.

The valve chest indications were excavated and prepped for welding.  The welding was performed utilizing a GTAW welding process for the root passes and a SMAW welding process for the subsequent layers. In-kind weld filler materials were selected for their compatibility and mechanical properties. Each weld layer was cleaned, inspected using a hot magnetic particle testing process, and control measures were employed to minimize distortion.  The team applied approximately 350# of weld between the two sides of the valve chest.

Once welding was complete, the shells were wrapped and insulated for PWHT. The heat treatment cycle included a ramp-up to 1225°F, soak at temperature, and a controlled cool-down. This step was essential to relieve residual stresses and restore the mechanical integrity of the repaired areas.

The upper half shell also revealed additional indications during inspection—one internal and three external. These were addressed through localized grinding and blending to clear the indications, and in one case, weld restoration using GTAW with local flame preheat. Per ASME code, no PWHT was required for this minor repair, but all locations were subjected to final NDE to confirm the absence of defects.

Following the repairs and heat treatment, MD&A conducted comprehensive dimensional inspections. These revealed improvements in shell flatness and roundness, particularly in the lower half shell. However, the lower half valve chest flange face, bonnet bores, and seat bores remained out of specification due to the legacy distortions from previous weld repairs.

MD&A provided detailed recommendations for machining and alignment to correct these conditions, including boring bar sweeps and machining of valve seat bores, bonnet bores, gasket pockets, and flange faces. These steps were critical to ensure proper fit-up and alignment during reassembly, and the final machining was performed by Mitsubishi.

In conclusion, this project underscores why MD&A is a trusted partner for utilities facing complex turbine repair challenges. With decades of experience in turbine-generator systems, MD&A brings unmatched technical expertise, agility in the field, and a commitment to quality that ensures successful outcomes, even when unexpected issues arise.

Their ability to adapt to evolving site conditions, execute precision repairs, and deliver comprehensive documentation gives plant operators confidence in the long-term reliability of their assets. Whether it’s a planned outage or an emergent repair, MD&A’s team is equipped to respond with speed and precision. Call us at +1 (518) 399-3616 today or use our contact form.

The post HPIP Outer Shell Valve Chest Weld Restoration Onsite appeared first on MDA Turbines.

Unit disassembly began with MD&A’s Outage Services Division crew mobilizing to site and setting up the outage plan.

During the disassembly, all critical as-found measurements were taken, recorded, and transmitted to both MD&A Engineering and the owner/operator.

After removal of bearings, oil/hydrogen deflectors and seals, eyebrows were installed, end shields lowered and support brackets removed. Hydrogen coolers were removed and MD&A’s experts withdrew the field from the stator core.

A complete list of replacement parts, bolts and gaskets needed for reassembly was prepared. Bearings were inspected and FME protection was installed, as 330H stator bar shipments arrived from MD&A stock.

Stator Rewind and Repairs

The phase connections were stripped and unbrazed from the connection rings which allowed for ease of rewind and much needed replacement, due to known cracking issues in similar models.

Series connections and top bar ties were cut for bar removal. A base-line electromagnetic core imperfection detection (ELCID) test was performed before wedge removal to determine integrity of the as-found core laminations.

The existing tapered wedge system was then removed by traditional methods and MD&A’s procedure. Although the wedge system had recently been given a clean bill of health by another provider during a previous in-situ wedge tap, it was obvious that the entire wedge system was loose, allowing premature aging of the bar ground wall insulation and likely a contributor to the failed insulation.

Series loop connections were removed. Original circuit ring connections were unbrazed and removed showing poor condition, to be replaced with new parts manufactured by MD&A. Top bars were then removed followed by inner radial rings for access to the bottom bars.

After bottom bar removal, core cleaning began followed by a post-disassembly ELCID. During cleaning, MD&A also replaced high-voltage bushings (HVB) with new O-ring seals.

Stator bar installation then began.

All tie materials were saturated with air-dry epoxies for more-solid bonding, limiting any loosening post installation. All bar ties and phase blocking ties were made with epoxy saturated “8-strand” glass roving.

Previous side ripple spring (SRS) abrasion was a concern. MD&A generator engineering improved the SRS design to prevent abrasion issues that have led to premature failure in several similar units. This process was followed on each end of the bar for the top and bottom bars.

Following completion of bottom bar installation and electrical testing, inner radial rings were installed, and resistance temperature detectors (RTDs) were placed in slots. Top bar and side ripple spring installation was completed, followed by full electrical testing.

New slot wedges were installed. Significant attention was given to the wedge system to ensure proper and tight installation. Compression of the top ripple springs (TRS) is a vital part of ensuring that the wedge system is correctly installed. TRS are installed to provide constant force overtime as the slot build materials relax and potentially loosen. The system is designed to make up for this relaxation with their inherent spring forces.

Each wedge was tested with an electronic hardness tester to ensure adequate TRS compression and to use as a baseline for future inspections.

Following wedge installation, a third and final ELCID test was performed to ensure no core laminations were damaged by the wedge installation process, and the original flux probe was installed. Another HiPot was performed to ensure that the bar ground wall insulation had not been damaged by wedging activities.

Series and phase brazing began. Brazing was performed with specialized double-headed torches for heating the plate/bar assembly. The phase and jumper connections were completed with the new plates manufactured by MD&A. Phase connection insulating series cap installation and all blocking completed the generator rewind work.

After completing all brazing work, copper winding resistance was measured to ensure that each of the three phases produced nearly identical resistance, indicating quality braze connections.

Final electrical testing was performed to ensure all components were ready for service.

The MD&A team is confident in the quality of the rewind completed on this generator. The bar ties installed are of the strongest and most durable type available in the industry. The wedge system is tight and the top ripple springs are compressed to 90%.

Reassembly

The generator coupling flange had an indication on the rim, so our Engineering team created a 3D model and performed a stress analysis to confirm it was in a low stress area.  It was recommended to blend out the indication and the 3D model confirmed the final geometry maintained full capability of the coupling flange. The blended area was polished and a final NDE (dye penetrant inspection) of blended area confirmed the indication was successfully removed.

Ongoing inspections included fan blades, bearings, load coupling bolts, hydrogen casings, oil deflectors and all coolers. Bearings were inspected and cleaned.

Hydrogen seals were measured and inspected. Bluing of the seals to the casing determined that lapping was required for acceptable contact.

With hydrogen coolers and shields reinstalled, the field was prepared and inserted into the stator. Inner oil deflector clearances were reset to limit the ingestion of seal oil into the unit.

All axial fan blades were inspected, verified, and returned to service. Six collector fan blades, showing trailing ends tip blends, were replaced.

The load coupling was aligned to OEM specifications.

Return to Service

The global team of MD&A experts returned this 330H generator to full service and renewed owner/operator confidence in its ongoing contribution to dependable electricity demand in the home country.

MD&A stocks stator bar sets for 330H, 324, 7FH2 and several other commonly found generator stator models.  MD&A is ready to mobilize anywhere in the world at a moment’s notice to support your emergent or planned outage needs

Contact the premier non-OEM service provider to the global turbine-generator market. Call us at +1 (518) 399-3616 today or use our contact form.

The post MD&A Completed 330H Generator Stator Rewind appeared first on MDA Turbines.

This guide outlines the 12 most important factors to evaluate before making the switch. It is designed to help plant leaders, maintenance teams, and procurement specialists assess providers based on what truly matters: performance, safety, flexibility, and long-term operational success.

1. Proven Experience with Your Equipment

Every fleet is different and so are the service demands of gas turbines, steam turbines, and generators. A qualified provider should bring deep, hands-on experience with your specific models and configurations. 

Look for a track record across multiple OEM platforms, and don’t hesitate to request detailed case studies, outage reports, or references from similar plants.

The right partner won’t just understand your equipment, they’ll understand how to keep it running at peak performance under real-world conditions.

2. Depth of Engineering Expertise

Look beyond fieldwork to the depth of in-house engineering support. Complex outages often require quick diagnostics, custom solutions, and technical agility. Strong engineering teams can help solve issues faster and prevent them from recurring.

3. Commitment to Quality and Standards

Quality isn’t just about compliance, it’s about confidence. The best third-party providers adhere to rigorous industry benchmarks like ISO certifications, ASME codes, and EPRI protocols, but they also back those standards with transparent, auditable quality systems. 

Ask how they measure workmanship, document inspections, and handle corrective actions. A strong quality culture means fewer surprises during outages, better equipment performance over time, and greater protection for your operational investment.

4. Modern, Well-Equipped Repair Facilities

Repair capabilities are a frontline factor in outage success. A provider’s in-house facilities directly influence quality, turnaround time, and cost control. When possible, tour their shops to assess their investment in infrastructure and craftsmanship. Look for:

• Rotor and component repair capacity that can handle heavy-duty, high-volume work
• Precision machining for tight tolerances and critical parts
• Generator rewind and overhaul expertise for full-unit support
  

Well-equipped facilities allow for faster problem-solving, fewer vendor handoffs, and more predictable outcomes, especially when timelines are tight and margins for error are slim.

5. Field Execution Capabilities

The best plans mean little without strong field execution. Successful outages depend on experienced project managers, skilled technical directors, and craft labor that knows how to perform under pressure. But execution isn’t just about showing up; it’s about being ready. 

• Ask about their track record in safety, schedule adherence, and on-site decision-making. 
• Do they come prepared for contingencies? 
• Can they coordinate multiple scopes simultaneously? 

Your partner’s ability to perform reliably in the field directly affects outage success, budget control, and plant availability.

6. Responsiveness During Emergencies

Unplanned outages don’t wait and neither should your service provider. Every hour of downtime can mean lost revenue, grid instability, or regulatory risk. Evaluate whether your vendor offers true 24/7 emergency response. 

Can they quickly mobilize technical advisors, critical parts, and field crews, even during nights, weekends, or holidays? Ask for real-world examples of emergency response scenarios. A partner’s ability to act fast and effectively when it matters most can be the difference between a controlled recovery and a costly crisis.

7. Parts Availability and Reverse Engineering

Outages can often hinge on one critical variable: parts availability. Delays in sourcing or fabrication can derail even the best-planned outage schedules. That’s why the right service partner offers more than just a supply chain, they bring solutions. 

Look for providers with:

• in-house or expedited manufacturing capabilities
• reverse engineering expertise for obsolete or OEM-proprietary parts
• proactive inventory strategies tailored to your fleet

Whether it’s a last-minute replacement or a long-term stocking plan, the goal is simple: keep your plant running without compromise.

8. Transparency with Data and Analysis

Data isn’t just a deliverable. It’s a decision-making tool. A provider should offer full visibility into:

• inspections,
• findings,
• root cause analyses, 
• with clear, actionable reporting. 

Avoid vendors who limit your access to performance metrics or hold back technical documentation. True transparency empowers your team to plan smarter, extend asset life, and reduce the risk of repeat failures. Ask how data is shared, how frequently, and in what format.

A transparent partner helps you stay in control, with insights you can trust.

9. Customization and Operational Fit

No two plants operate the same; and your service provider should reflect that. One-size-fits-all maintenance plans often miss the mark when it comes to fleet diversity, operational constraints, or outage philosophies. 

Look for partners who take time to understand your plant’s specific goals, risk tolerance, and performance targets. Whether it’s adjusting scope to fit a tight window or tailoring deliverables around your internal resources, true customization helps optimize outcomes, not just complete checklists.

10. Breadth of Services Across Systems

A comprehensive service provider should cover all major rotating equipment, including gas turbines, steam turbines, and generators, under one roof. This breadth simplifies outage planning, reduces coordination complexity, and ensures technical consistency across systems. 

When one partner can support the entire unit, you gain faster diagnostics, fewer delays, and clearer accountability from start to finish. Look for a provider with proven experience across systems and the ability to integrate services into a unified outage strategy.

11. Innovation and Continuous Improvement

A strong service provider doesn’t just maintain your equipment, they help you push it further. Ask whether they offer performance upgrades, custom engineering solutions, or life-extension strategies tailored to your operating conditions. Do they analyze failure patterns and recommend preventative changes, or just return equipment to baseline?

Providers committed to innovation continuously refine their processes, learn from the field, and bring forward new ideas to reduce lifecycle costs and improve long-term asset performance. In a competitive, margin-driven environment, that edge can make a measurable difference.

12. Commitment to Long-Term Relationships

Choosing a service provider isn’t just a transactional decision; it’s a long-term investment in your plant’s reliability and performance. The best partners go beyond the outage at hand to build lasting relationships rooted in familiarity, trust, and shared goals. Look for signs of long-term alignment, such as:

• Repeat business from utilities and IPPs who rely on them year after year
• Account teams who know your fleet, site conditions, and outage history
• Asset tracking tools that support smarter planning

A provider who’s invested in your long-term success is more likely to deliver proactive insights, flexible support, and consistent execution over time.

Conclusion: Your Decision Impacts the Future of Your Fleet

Shifting away from the OEM can yield faster service, better value, and more flexible solutions, but only with the right third-party partner. Use this guide to evaluate providers with long-term reliability and strategic fit in mind.

Your turbines power the grid. Choose a partner who powers your success.

Why Partner with MD&A?

Mechanical Dynamics & Analysis (MD&A) has been helping power generators across the globe navigate OEM transitions for over 40 years. Our deep expertise spans gas turbines, steam turbines, and generators, from complete overhauls to life-extension strategies and performance upgrades.

When you work with MD&A, you gain a partner focused on your plant’s long-term reliability, flexibility, and performance. Our engineers, field technicians, and repair specialists are committed to delivering solutions that work, not just today, but for years to come.

We understand that every plant is different. That’s why we offer fully customized scopes of work, proprietary and reverse-engineered parts, and fast-response service. All backed by clear communication, collaborative planning, and transparent data.

Let’s Talk

If you’re exploring options beyond your OEM, or simply want a second opinion on how to optimize your next outage, we’re here to help. Let us provide answers to all of the considerations outlined above and show you what’s possible with the right partner.

Call us at 518-399-3616

Or reach out directly via our contact form to schedule a consultation.

Let MD&A show you what’s possible, beyond the OEM.

The post Thinking Beyond the OEM: 12 Critical Considerations for Choosing a Third-Party Turbine Services Partner appeared first on MDA Turbines.

In today’s energy landscape, regional capacity shortfalls are creating more restrictive outage durations. At the same time, supply chain constraints continue to challenge the availability of critical components. Lastly, manufacturing and repair shop capacity is nearing full utilization due to high demand. For power generators, this means that every minute of downtime matters and every part must be ready when needed.

That’s why MD&A is helping customers take a proactive approach to parts inventory planning.

The Solution: Increase Inventory Ahead of Planned Outages

By building up inventory of critical spares before outages begin, this enables faster turnaround, reduced risk, and keeping your outage on track.

Here’s a breakdown of the key components we’re helping customers stock in advance:

1. ‘Drop-in’ valve assemblies

Our Drop-in Valve Solution combines the valve wear parts into a pre-assembled set and allows you to replace them more quickly. This moves the detailed shop inspection and repair work for individual valve parts off the outage critical path. The Drop-in set that is removed is inspected/repaired/replaced at the shop and prepared for the next outage.

2. D-11 Upgraded valve components

Such as our MD&A developed MSV Nickel Cladded Stem and Hardened Seat Upgrade can reduce erosion rates & prevent steam leakage. With proven results reducing stem erosion by 80%, these components offer direct interchangeability with existing parts and enable extended maintenance intervals.

3. Stellite-lined Bushing upgrades

The Stellite-lined bushing upgrades help reduce oxide formation/ stem binding, minimize wear while maintaining stem-to-bushing clearances, and support extended maintenance intervals.

4. Patented Triplet Type MSV upgrade

The Patented Triplet Type MSV upgrade provides an effective counter-measure to solid particle erosion experienced on conventional valve designs.  One advantage of the Triplet Type Bypass Main Stop Valve includes significantly reduced erosion on the valve stem and skirt.  Consequently, valve maintenance is reduced.  This design can be applied in both sub and super-critical applications.

5. Long Blades

Our Continuous Cover Blades (CCB) are constructed using a mono-block blade structure that leaves fewer locations for corrosive deposits and is less susceptible to stress corrosion cracking. Also ask about our 34.5” LSB direct replacement option.

6. Packing and Spill Strips  

Packing and Spill Strips can be manufactured in advance of your outage to reduce the critical path. We stock of a large variety of raw materials, and sizes, to serve our customer base. Our extensive technical library provides us with the ability to manufacture to OEM specifications and tolerances or make experience driven recommendations.

7. Stator Rewind and Punching Kits 

7A6 & 7FH2 generator stator rewind and punching kits, along with generator exchange fields – both new & refurbished fields. These in-stock components ready to go will shorten your outage duration and keep your equipment running.

8. Turning Gear Components

Turning gear components often have long lead times, so it’s best to order them well in advance to ensure they’re on hand and ready when needed, rather than waiting during your outage.

9. Flow Parts 

Also stock all your Flow Parts: Valve components, Shell & casing hardware (including Inco/Refractalloy components), Snout rings and bell seals, and new bearings and oil deflectors.

The Impact: Shorter Durations, Longer Intervals, Less Risk

Strategic parts inventory planning isn’t just about having parts on hand. It’s about reducing schedule risks, extending outage intervals, and addressing known reliability issues before they become problems.

MD&A’s approach ensures that your team is prepared, your equipment is supported, and your outage strategy is optimized.

Ready to Plan Smarter?

Let’s talk about how MD&A can help you build a smarter inventory strategy for your next outage. Contact us today or explore our full range of outage support services.

Call us at 518-885-3199 or reach out directly via our contact form to schedule a consultation.

The post Strategic Parts Inventory Planning – Staying Ahead of Outage Constraints appeared first on MDA Turbines.