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.

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.

MD&A specializes in servicing E- and F-class gas turbine rotors.

To provide the best solutions for your gas turbine rotor, MD&A will evaluate your specific needs in addition to assessing rotor inspections.

Learn more from Dave Fernandes, MD&A’s Gas Turbine Program Manager, & Spencer Hamilton, MD&A’s Gas Turbine Services Sales Director in the following Q&A:

1. 1. In the early 2000s the US gas turbine market saw a significant boom, often referred to as a «bubble.” – what is the bubble?
      

      The «bubble» refers to the surge in new gas turbine–based power plant expansion in the United States. It was driven primarily by shrinking power reserve margins, relatively low natural gas prices, and power market deregulation.

   2. What did that mean for GE® sales & installs at the time?
      

      GE’s production of gas turbines rose dramatically—from a capacity of about 80 machines per year in 1998, to 180 in 1999, and 240 in 2000. The majority of these sales were the GE 7FA gas turbine.

   3. Fast forward, what does that mean for these gas turbines for their remaining life? Why is it important to look at?
      

      A large percentage of the 7FA installed base came from the 1998–2001 bubble. Many of these units are now approaching their rotor end-of-life, as outlined by the OEM: 144,000 fired factored hours (FFH) or 5,000 fired factored starts (FFS).

      Operating profiles vary, but some combined cycle units can accumulate more than 7,000 fired factored hours in a single year.

      As a result, many bubble-era units—especially base-loaded combined cycle plants—are nearing their end-of-life limits.

   4. What role do these aging assets currently play in our overall energy mix, and how critical are they to grid reliability?
      

      Thanks to their favorable heat rate (efficiency) and lower emissions compared with many other fossil fuel plants, 7FA combined cycle units form one of the backbones of the U.S. power grid. In addition, simple-cycle 7FA and 7EA units play an essential role in supporting peak load demand and grid stability.

   5. Are all 7FA rotors the same?
      

      No. The early 7F models, known as 7F.01 and 7FA.02, have significant design differences compared with later models (7FA.03 and beyond). Most of the turbines installed during the bubble were the 7FA.03, which remains widespread today, along with the 7FA.04. There are no major differences between the 7FA.03 and 7FA.04 rotors. The difference between a 7FA.03 and 7FA.04 gas turbine is associated with the combustion and hot gas path parts.

   6. With the high demand for new manufacturing impacting the industry & other items, Why should customers be thinking now about their rotor for next 3-5 years? Why the urgency? 
      

      Planning ahead is critical due to supply chain constraints. Forging houses that produce gas turbine components also serve the aerospace and defense industries, all of which are experiencing simultaneous surges in demand. This results in longer and less predictable lead times.

      Shop capacity is also strained, with limited space and workforce available to handle the growing number of gas turbines nearing rotor end-of-life. Securing both parts and shop availability early is essential to keeping these valuable assets running.

   7. Is there increasing difficulty or expense in sourcing parts and technical expertise for these aging turbine models? 
      

      Yes. Supply chain challenges have driven costs higher, while shifting tariff policies add further unpredictability to the price of key components.

      In addition, OEM technical expertise often shifts toward supporting newer product lines—particularly as the latest “bubble” of gas turbine development has emerged, with the H-class leading new unit sales.

      In contrast, MD&A remains committed to legacy assets, continuing to prioritize support for the 7FA, 7EA, and 7B fleets for years to come.

With changes in the industry, growth and the bubble, you should be thinking now for next 3-5 years!

A Rotor Life Assessment & Extension service can help decide if component repair, replacement, or use is the best option for your gas turbine rotor to meet operational and maintenance forecasts.

Want to learn more? Watch our Video!

Or Secure a spot to our Rotor Life Extension webinar

The post The Clock Is Ticking On 7FA And 7EA Gas Turbine Rotors: Is Your Fleet Prepared? appeared first on MDA Turbines.

During full-load operation, the steam pressure differential between the HP and IP turbine section forces the packing casing towards the IP section. The outer perimeter main axial locating fit of the packing casing resists this unbalanced steam force.

At full operating temperature, the casing material is vulnerable to cumulative creep rupture damage. Radial circumferential cracking has occurred within the industry and has led to loss of axial positioning of the N2 packing casing, potentially causing internal damage to the turbine rotor and diaphragms.

Inspection and Engineering

Incoming disassembly, blast cleaning and detailed inspections were performed by component specialists at MD&A’s Turbine Generator Repairs Division facility in St. Louis, MO.

Following incoming inspections, the original geometries of the casing main axial fits were reverse engineered, a key activity by MD&A’s experienced and precision-oriented professionals. This process measured the main axial fit widths, main axial fit fillet radii and chamfers, and fit faces critical axial positions.  MD&A experts found evidence of distortions, galling and fretting damage.

A complete and clear listing of recommended repairs and hardware replacements was then prepared and reviewed with the owner/operator.

Findings and Resolutions

Initial recommendations focused on the lower half and upper half N2 packing casings.

For the lower half casing, inspection revealed rough surface and erosion on the outside diameter main axial locating fit steam seal face. MD&A experts would restore the steam seal face by welding and machining. For the upper half casing, findings included rough surface and erosion on the OD main axial locating fit steam seal face. Also, the fillet radius-to-steam seal face showed visible intermittent liner crack indications. They removed the crack indications and restored the original geometry by welding and machining.

Further investigations revealed additional requirements. For the upper half casing, OD left and right-side dowel pin though holes would need repair due to excessive clearance.

Horizontal zero-clearance joint packing groove key pocket threaded holes, both left and right sides, showed thread damage and excessive tap wobble. This appeared on both the turbine and generator ends. MD&A actions included removal of the damaged threaded hole, weld restoration and machining for all four locations, followed by post-weld heat treatment.

Horizontal joint studs, softened during the original work scope, were removed by destructive machining and replaced with new hardware. Selected new hardware would also be required for horizontal joint steam dam springs and screws; left and right-side elevation block bolts, clearance keys and key screws; horizontal joint nuts; and horizontal joint studs.

Restoration

The packing casing halves were welded and post-weld heat treated. The main axial locating fit was weld restored, as was the zero-clearance groove keeper block screw holes.

Post-weld heat treatment was performed, utilizing distortion control bars, which were removed, followed by blast cleaning of both casing halves.

Final machining and grinding were then performed. This included the main axial fit geometry, and final grinding and blending to clear all NDE indications. In addition, the back-side boss surface of the main axial fit steam seal face was welded to increase thickness and improve stiffness.

Inspections, Assembly and shipment

Final inspections, and final NDE and dimensional checks were then performed by MD&A Quality personnel.

Full 100 percent magnetic particle inspections revealed no findings. Casing upper and lower halves were laser mapped to confirm flatness. Final diameters and vertical radial drops were also completed.

MD&A then completed final assembly of the upper and lower halves in preparation for return shipment.

MD&A successfully completed the inspections, engineering, repairs, restoration and improvement of the N2 packing casing at its St. Louis facility. This project enters the MD&A portfolio as another example of the company’s global response as a premier, non-OEM service provider to the worldwide steam and gas turbine generator industry.

Call us at +1 (518) 399-3616 today or use our contact form.

The post Steam Turbine N2 Packing Casing Repairs appeared first on MDA Turbines.

As a result, over 40 years later, MD&A has evolved from a small firm to a large service provider with over 600 employees reaching more than 100 customers each week during outage season.  The reputation for outstanding service in the US has enabled MD&A to spread globally with parts, repairs, and services on large turbine-generator sets.

Watch our company video!

The post MD&A Company Video appeared first on MDA Turbines.

Here are the significant initiatives we have in place to ensure continuous growth and development within our organization.

Mentoring Program and Succession Planning

Kristin Esterby, our Human Resources Director, addressed the critical need for effective succession planning, particularly as many of our seasoned professionals approach retirement. «We’re facing a unique challenge with our workforce,» Kristin noted. «Not only are we navigating the aftermath of the COVID-19 pandemic, but we also have an aging workforce.» This demographic shift necessitates proactive measures to maintain our high standards of service and expertise.

To address these challenges, MD&A has implemented several strategic initiatives:

• Succession and Talent Planning: Our approach focuses on evaluating individual performance, setting clear goals, and creating tailored development plans. This ensures that our employees are prepared to step into critical roles as they become available.
• Mentoring Programs: We are in the process of developing both formal and informal mentoring programs. These initiatives aim to facilitate knowledge transfer between experienced leaders and newer employees, fostering an environment of continuous learning and growth. Technical-specific mentorships are also being established to address the unique challenges of our industry.

Kristin emphasized the importance of these programs in bridging the knowledge gap and ensuring a smooth transition of expertise. «Mentorship is not just about transferring knowledge; it’s about building relationships and creating a culture of support and mutual growth,» she explained.

Learning and Training (LEAP)

One of our most impactful initiatives is the Leading Effectively at Power (LEAP) program. This week-long training event brings together 20-25 leaders from various divisions to enhance their leadership skills. The curriculum covers crucial topics such as finance, legal considerations, and change management. Participants engage in interactive sessions that promote cross-functional learning and collaboration.

Kristin highlighted the dual benefits of the LEAP program: «Participants not only gain insights from our expert instructors but also learn from each other, which is invaluable for their development as leaders.» This collaborative learning environment helps build a cohesive leadership team equipped to handle the complexities of our industry.

In addition to LEAP, we are launching a pilot series called Leadership and HR 101. This program aims to equip our leaders with foundational knowledge in key areas such as human resources and basic management principles. By providing this training, we ensure that our leaders are well-prepared to manage their teams effectively and foster a positive workplace culture.

Engineers in Training (EIT) Program

Charles Monestere, our General Manager of Technical Services, provided insights into the Engineers in Training (EIT) program. Initially, MD&A focused on hiring experienced engineers. However, in 2009, we shifted our strategy to recruit recent graduates, recognizing the value of fresh perspectives and new talent. This structured program combines intensive classroom training with hands-on, on-the-job experience under the mentorship of our seasoned engineers.

Charles outlined the program’s objectives: «We aim to hire about ten new engineers each year. Our goal is to provide them with a comprehensive understanding of our operations and prepare them for long-term careers with MD&A.» The EIT program has grown significantly since its inception, reflecting its success in developing well-rounded engineers who are ready to contribute to our mission.

Personal Experience: Colin Baker

To provide a personal perspective on the EIT program, Colin Baker, a Field Engineer and recent EIT program graduate, shared his journey. «I joined MD&A straight out of college with minimal turbine experience,» Colin recounted. «The EIT program allowed me to learn from experienced engineers and apply that knowledge in the field.» He emphasized the importance of networking and continuous learning, which are integral components of the program.

Colin’s story is a testament to the program’s effectiveness. He highlighted how the EIT program not only provided technical training but also fostered a supportive environment where he could grow both professionally and personally. «The mentorship and hands-on experience I received were invaluable. It helped me build confidence and develop the skills necessary to excel in my role.»

Looking Ahead

At MD&A, we believe that investing in our people is crucial to our long-term success. Through our comprehensive mentoring and training programs, we are preparing our workforce to meet future challenges head-on while fostering a culture of continuous learning and development. These initiatives ensure that we remain at the forefront of the power industry, delivering excellence and innovation.

View Open Positions & Apply

The post Building A Powerful Future: Insights from Our Mentoring and Training Programs appeared first on MDA Turbines.

We were contracted to perform an inspection and any necessary Steam Turbine rotor repairs. After a thorough inspection, bucket and cover repair work was performed on the 1^st and 17^th stages of this rotor due to damage identified.  This rotor has a total of 19 stages, 12 high pressures and 7 reheat stages.

The 1^st stage buckets and covers were replaced with hardware supplied by the customer.  The new buckets were installed on-site, the notch bucket was driven and pinned and the new covers were peened into placed using gathered reverse engineering data.

The 17^th stage had the covers that were found partially liberated.  The tenons of those buckets that had liberated covers were welded up, and then new covers installed.

Both stages were machined to restore the proper clearance and required features.

Further inspection of the rotor showed that the underside of the bucket covers on the other stages had excessive debris build up, which was was removed and the entire rotor was then blast cleaned.

1st stage row restoration and machining completed

17th stage cover restoration and machining completed

1st stage admission side machined

Additionally, during the on-site inspection of the turbine first stage stationary blading (diaphragm) severe damage was found and MD&A was requested to repair this diaphragm.  The diaphragm was shipped to our Turbine-Generator Repair Facility in St. Louis MO. Upon inspection, it was discovered that the diaphragm exhibited significant Foreign Object Damage (FOD) and linear indications were detected in the partitions.

When the diaphragm was received, it was cleaned and given a complete Non-Destructive Examination.  Due to the extent of damage found on the blading in the steam path partitions, major repairs were required. After weld repair was performed, a post weld heat treatment was done to remove residual stresses.

Repair of the partition side wall, as well at the horizontal joint, were necessary due to extensive damage found. The steam seal face was machined, and an insert installed to restore the axial position of this diaphragm.

New diaphragm root radial seals, seal strips and horizontal joint keys were installed as well as the support bars for the diaphragm.

MD&A can be called upon to perform any technical evaluation anywhere and do the work needed for your rotating power generation equipment to get it back online safely and quickly.

For all steam turbine rotor repairs questions, and to discuss creative resourceful solutions, call MD&A today at +1 (518) 399-3616 or use our Contact form.

Steam seal face prior to insert installation

Extensive damage to the steampath

Final diaphragm repair finished and ready for shipment back to site.

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Since standard documentation was lacking and this was an atypical configuration, the bucket replacement process began by developing a new assembly procedure specific to this unique configuration. MD&A’s team worked closely with the customer to acknowledge and overcome this challenge with open communication being at the forefront.

HP/IP Rotor Inspection

The process began with blast cleaning and inspection of the rotor by MD&A’s experts.  Visual, dimensional, and magnetic particle inspections (periphery and axial headshot) were performed prior to assessing any required repairs.

Several issues were found during the inspection. It was noted that airfoil HVOF (High-Velocity Oxygen Fuel) coating had visible lines, which were later determined to be acceptable. Incoming rotor runout measurements were collected. No major findings were discovered on the control shaft or packing lands. It was noted that the T1 journal had scratch marks, taper and diameter were assessed, and found to be within acceptable tolerances. The T2 journal, however, demonstrated deep grooves, a .004” taper, and a diameter deviation. As such, MD&A suggested that the journal be skim cut.

Prior to blast cleaning, stage 10 buckets were removed: both foreign object damage and solid particle erosion. Inspection revealed that there was foreign object damage (FOD) at every stage. On stage 1, damage was noted on the covers, roots, and tenons, while other stages had FOD primarily on the leading edges and some on the covers. Several stages had HVOF coating to the airfoils, while debris remained after blast cleaning beneath stage 11 and 12 covers. Raised material was noted on stage 14.

HP/IP Bucket Replacement

Bucket replacement was conducted at MD&A’s Turbine-Generator Repair Facility in St. Louis, MO. MD&A’s technicians replaced 90 standard buckets supplied by the customer, in addition to one auxiliary bucket, and a two-piece lock bucket.

Five D-keys were supplied along with 2 special keys for the last bucket. These keys fit between the bucket root and the rotor groove and serve to fix the buckets axially. The removed D-keys had mechanical damage and needed to be replaced, however none were in stock. As this was a time sensitive job, MD&A’s machinists fabricated 82 standard D-keys in the shop. Reverse engineering measurements were then taken in preparation for the overhaul. New buckets were scanned to record geometry, and hand measurements were taken.

The process involved fitting new buckets with an interference fit, necessitating the tightening of bucket groups by MD&A’s technicians using heavy-duty straps. Rubber protection was employed to safeguard trailing edges during this process. The last 5 buckets were secured axially with twist-locks. The twist locks were secured by bending over the tabs. The 2-piece lock bucket also had a special key installed to fix the airfoil axially.

Shims were inserted post-bucket installation, before cover machining. Following machining, shims were removed. A low-speed balance was then performed with the control shaft installed. After completing these repairs, the rotor was cleaned, coated with lubricant, and plastic wrapped.

Minor Bucket Repairs

In addition to the major bucket repair for stage 10, several other repair and maintenance tasks were executed in response to the inspection findings and recommendation detailed earlier. Raised and loose material was removed off the covers, root, and tenons on stage 1. For stage 2 and 11, loose material was removed from the airfoils. For stage 3-9,12, and 13, foreign object damage was removed from the leading edges. Debris was removed from underneath the covers for stages 11 and 12, while raised material was removed off the rubbed root axial seal on stage 14. The T2 journal was skim cut.

The overspeed trip device was inspected and tested at our Bearings Seals and Hydraulics facility in Euclid, OH, leading our technicians to install new lock plates with the control shaft and overspeed trip device. The final runout was recorded and noted as within tolerance.

HP/IP Diaphragm Inspection and Repairs

MD&A experts performed minor repairs to the diaphragms and removed broken hardware.

This included corner weld repairs, bench backing of trailing edges, loose material removal, and straightening of trailing edges with foreign object damage (FOD). Localized weld repairs were also performed by MD&A’s technicians for damaged HJ bolt spot faces, NDE indications, and stage 3 HJ steam cut. Broken hardware, such as HJ bolts, packing screws, and spill strip retaining screws, were removed, and replaced as needed. Raised material was removed off steam seal faces and keyways, and the rubbed root radial seals were sharpened. Weld was also added to select crush pins and centering keyways. Ledge keys were destructively removed and replaced with MD&A’s stock components.

In Conclusion

What began as a stressful situation for our customer ended up being a success story for all involved. Our ability to overcome obstacles and be innovative demonstrated MD&A’s breadth and agility within the repair space. Our nine bucket technicians leveraged roughly 300 years’ worth of experience to successfully plan and execute this job. The team excelled at assessing the non-standard configuration, inspecting it, repairing, and maintaining the unit, and developed and provided detailed maintenance procedure documentation for future reference.

This case also serves as an excellent reminder for customers to form beneficial partnerships with their service providers. This teamwork approach, combined with open communication on both sides, leads to quick and thorough resolution of the customer’s challenges. As testament to the customer’s satisfaction, they called MD&A back to perform bucket replacement on a second unit (after the first unit)!

For all service and repair questions, and to discuss creative resourceful solutions, call MD&A today at +1 (518) 399-3616 or use our contact form.

The post Bucket Replacement for Non-Native Bucket appeared first on MDA Turbines.

A braze-cracking issue can occur with F-Class DLN 2.0 and 2.6 end cover designs. Turbines at the greatest risk are those burning unheated fuel.

Low-cycle fatigue is the primary cause of braze-joint fracture at the 4 possible braze locations on each insert location. Thermal stresses are a contributor because temperatures in the susceptible locations can cycle from 100°F to 700°F.

For fuel nozzles of OEM design, insert braze cracking creates the opportunity for gas to leak into neighboring circuits and contaminate burner-tip cooling air. This scenario can create emissions and tuning challenges, not to mention the possibility of increased flash-back potential. Flashbacks can result in nozzle damage which can lead to catastrophic failure.

These failing conditions are identified if insert replacements requirements are met and reported on at incoming inspection (pressure test). At this point, under these conditions, the industry standards are to perform a full insert replacement of each failed cover assembly.

Additionally, the currently understood industry standard for brazed insert replacements (as set forth and published by the OEM) is a maximum of 3 insert replacements per cover before the cover is deemed scrap. Each time an insert replacement occurs, .030” of material is removed from the bore to establish clean parent metal for the new braze joint.

Our team has performed extensive research and development found that the “3-and-out” strategy was only true for the original 7FA DLN 2.0 cover design and not the others.

Using the original 7FA gas turbine DLN 2.0 combustion end cover as a baseline for our assessment, which used the as-designed 5/8-11 threaded wire inserts in order to secure the outer fuel nozzles to the end cover. A minimum wall thickness, at pressure vessel requirements, had been calculated to be .078”.

It was confirmed that the 7FA DLN 2.0’s 3^rd repair cycle, the minimum wall thickness is optimally .081”. Therefore the 3 insert maximum was met.

We modeled and destructively tested the 6FA DLN 2.0 end cover which had also been assessed by the OEM to only permit 3 insert replacements.

However, we had also discovered through destructive testing and 3-D modeling of the “6FA” 2.0 cover’s internal passages, that while maintaining minimum wall thicknesses insert replacements can double over the OEM recommendations of “no more than 3 replacements allowed”.

Solution & Life Extension:

MD&A Fuel Nozzle Services found that insert replacements up to 7 repair cycles, had a minimum wall thickness at .093”.  The same is true for the 7FA DLN 2.6 since the 6FA DLN 2.0 and 7FA DLN 2.6 designs use ½-13 threaded wire inserts rather than the 5/8-11 of the 7FA 2.0 to secure the nozzles to the end cover.

Our team can extend the life of the end cover on the 6FA DLN 2.0 and 7FA DLN 2.6 past the currently understood industry standard by continuing the repair cycles until the minimum wall thickness is obtained. We have also incorporated additional machining of the cover to address the warping issue that is associated with the end covers throughout their lifetime, especially with those that are utilized in an unheated application.

Conclusions & Results:

With a new maximum of up to a final 7^th insert replacements per cover, the life expectancy of an end cover increases from the OEM claim of 48,000 hrs. to over 125,000 hrs. At an average estimated rate of repairing 4 covers every 3 years, you would not need to replace a cover for 75 years!

MD&A is a worldwide leader in the repair and refurbishment of gas turbine fuel nozzles.  Our advanced engineering expertise combined with leading-edge equipment delivers reliable, extended life for new or refurbished fuel nozzle products.

Call MD&A today for Fuel Nozzle End Cover Insert Life Extension at +1 (864) 721-4200 or use our Contact form.

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