MD&A provided all project management, inspection and analysis, supervision, labor and tooling for the owner’s dual-unit work scope.

During disassembly of the first unit, MD&A Gas Turbine Services personnel first removed roof sections, recorded thrust and lift checks, removed all relevant casings, and labeled/removed relevant piping/hoses. Half shell readings were taken on the turbine and compressor by recording all rotor and stator tip clearances.

The service run 7FA.04 hot gas path components were inspected and analyzed onsite by specialists from MD&A’s San Antonio Service Center to determine the potential for future component repairs. Our team has extensive knowledge on a range of gas turbine component repairs, including weld repair, blending, dimensional restoration, and machining. They can extend the service life of gas turbine components whose OEM service limit has passed or whose configuration is no longer suitable to operate. These experts provided feedback on the component repairability.

For these outages, the turbines’ first, second, and third stage buckets were removed and replaced with Customer provided components.

Additionally, nozzles and shrouds were removed and exchanged. For the compressor, stage 14 through EGV’s stator vanes were removed; new vanes were drilled and pinned upon installation.

MD&A inspected T1 and T2 bearings and determined replacements were required, in addition to new thrust bearings.

All combustion components were removed and inspected. Transition pieces, liners, flow sleeves, outer bellows, inner crossfire tubes and fuel nozzles were exchanged during reassembly.

The GE® 7FH2 generator was disassembled, including coolers, oil deflectors, gas shields and bearings. Hydrogen casings and seals were removed and sent to MD&A’s Bearings, Seals and Hydraulics Division in Euclid, Ohio for refurbishment.

The generator field was then removed and transported to our Turbine-Generator Repair Facility in St. Louis, MO for a complete field rewind utilizing the existing copper. The rewind process was expedited to allow for the rewound field to be installed in the sister unit. A spare generator field from the Customer’s inventory was installed on the first unit, to support the expedited outage schedule.

MD&A experts inspected the generator stator and found areas of greasing indicated a loose wedge structure and necessitating a full stator rewedge. Core and bellyband tightening was also required.

Stator electrical testing was completed, and electromagnetic core imperfection detections (ELCID) tests were conducted before and after wedge replacement.

MD&A’s Generator Experts replaced the wedges, then completed bellyband and core tightening. With the stator repairs complete, the generator field from owner/operator’s inventory was able to be installed.

During component reassembly, new hydrogen seals and springs provided by MD&A’s Bearings, Seals and Hydraulics facility were utilized.

Following reassembly of the gas turbines and generators, coupling alignments were performed by MD&A technical experts in full collaboration with the Owner/Operator.

MD&A’s Turbine and Generator Controls Division performed a complete inspection of the exciter and inverter equipment, ensuring no issues on return to service. Startup was completed with no operational concerns and full compliance with emissions standards.

Following execution of the first outage, MD&A personnel shifted focus to the sister unit, to complete a nearly identical work scope.

For this unit, turbine first, second, and third stage buckets were replaced as were nozzles and shrouds.

A spare Customer provided Gas Turbine rotor was installed after conducting green rotor inspections and repairs. At startup the green rotor run-in was completed in compliance with industry standards.

As with other unit, all Technical Information Letters were listed as completed, as were all Extra Work Authorizations.

For this unit, the service run generator field was removed for transport to our Turbine-Generator Repair Facility for a complete field rewind utilizing the existing copper. This field would be rewound and returned to Customer after the outage to be held as inventory.

Conclusion

Throughout these major overhauls on two 7F.04 Gas Turbines and 7FH2 Generators, detailed daily written and visual (photographic) job reports and updates documented all current and planned activities, alerts, needs, schedules, recommendations, and resolutions.

For every repair job, large or small, the speed and effectiveness of our response team is matched only by the depth and breadth of our engineering expertise.

Successful completion of these back-to-back projects clearly exemplifies the multi-divisional breadth, versatility, and corporate commitment of MD&A as a premier non-OEM service provider to the global gas and steam turbine-generator market. Call us at (518) 399-3616 today or use our contact form.

The post Back-to-Back Major Overhauls on Two 7F.04 Gas Turbines and 7FH2 Generators appeared first on MDA Turbines.

In fact, MD&A established itself in the beginning as the preferred non-OEM supplier, regardless of original supply or design.

Founded in 1982, MD&A takes great pride in the extensive OEM experience, knowledge, and skills of both its technical experts and management personnel.

A recent case in point: MD&A performed a full stator rewind of a GE® 7A7 generator that suffered an in-service ground fault failure. In order to meet the owner/operator return-to-service schedule for the stator rewind, the owner operator called in MD&A. The rewind was completed on schedule with no safety incidents or concerns, and the unit passed all detailed testing for return to operation.

Specialists from MD&A’s Generator Division arrived on site and completed all site-specific training, walkdowns, and tool staging.

Initial baseline testing, physical measurements, and winding configurations were confirmed. Stator end windings and core were scanned and modeled to aid in the manufacture of new stator bars. To meet the return-to-service schedule, MD&A experts were able to get the new bars quickly.

A baseline electromagnetic core imperfection detection (ELCID) analysis was performed on the stator core iron to determine the integrity of as-found laminations.

The existing wedge system was then removed according to MD&A procedure. Series loop connections were removed and collector-end circuit ring connections were cut.

After bar tie removal, top bars were removed, stacked, and placed in recycling containers. Inner radial ring and bottom-bar ties were then removed, followed by all bottom bars.

Significant levels of partial discharge were noted on several bars with high line-to-neutral voltage potential.

T4 connection ring inspection found material missing at the extension, likely a source of discharge during the generator failure. The T2 ring showed damage at the phase-strap location.

All connection ring pieces were removed and inspected to be repaired and reinstalled. Damaged pieces were replaced with newly-manufactured material. A DC HiPot test was then completed on the circuit rings. A post-disassembly ELCID was also performed to ensure no damage to the core iron, and a loop test confirmed the integrity of the stator core.

For reassembly, binding bands were received and aligned on both ends and made concentric to the core – a vital step for proper bar alignment and consistent felt buildup.

Binding bands were installed and bar installation began. A thin felt layer in each slot served as a bottom breaker between the bar and core iron.

After close-up bar installation, bottom bars were installed and permanently tied with blocking, saturated felt, and saturated roving ties. Side-ripple springs were installed to secure proper seating and avoid any vibrational movement. A bottom-bar Hi-Pot verified the integrity of bar armor insulation.

At this point, a total of 12 new Resistance Temperature Detectors, more accurate than traditional thermocouples, were installed, terminated, and verified. Inner radial rings were installed and top-bar installation began, followed by comprehensive Hi-Pot testing.

For wedging, a tapered low-shrink black canvas (LSBC) wedge and slide design with a top ripple spring was selected for sufficient radial pressing force. Filler was adjusted at each wedge for proper compressive force. Center and body wedges were installed throughout the core, followed by end wedges cut specifically for each of the 72 slots.

Brazing was completed by traditional method and MD&A procedure, and a winding resistance test ensured that the three phases produced similar resistance values. Series, circuit ring, and jumper connections were then installed. The insulating tape used by MD&A ensures no voids or cracks form along the phase breaks during operation, where the voltage potential is the greatest. Series blocking was installed and tied to reduce vibrational movement. Frequency response testing followed.

After the generator stator rewind, comprehensive electrical testing included copper and insulation resistance, final DC HiPot, and DC leakage testing of each phase. All testing results were verified and accepted.

A final crawl-through inspection was completed with the owner/operator. Field installation could begin, and the generator would soon be returned on schedule for dependable, long-term operation.

Once again, MD&A has shown the global electric utility industry its depth of knowledge, finely-tuned technical skills, and repeatedly-proven owner/operator commitment.

MD&A is truly a premier non-OEM service provider to the global gas and steam turbine-generator market. Call MD&A about your next outage today at (518) 399-3616 or use our Contact Form.

The post MD&A Generator Stator Rewind with Timely New Bars appeared first on MDA Turbines.

Several 7FH2 units have experienced failures of the core step iron, caused by inadequate compression of the core laminations.  This issue was first brought to light by GE® TIL 2260, which only covered certain units; however, this recent failure was outside the scope of this TIL, indicating that other units may be at risk of a similar failure.

MD&A recommends that all 7FH2 generators be subjected to core tightening, preferably during the rewind of the stator.  However, if no rewind is in scope, then the core tightening should be performed during the next planned outage. Many of the 7FH2 units are more than 25 years old and are approaching their intended design life.  This particular unit had the damaged core iron replaced and windings replaced.

The unit was last inspected during spring 2020 utilizing a generator robot and was classified as “good” with no issues noted, indicating that the issue can develop & present over a short period of time.

The outage started as a Gas Turbine Hot Gas Path with Generator Robotic In-Situ Inspection. The Generator scope included a full battery of electrical testing on the field & stator. The Robotic In-Situ Visual Inspection included a Wedge Map, & ELCID core iron assessment.

The Robot crawler traversed axially from CE (collector end) to TE (turbine end) utilizing both a straight facing camera and 360-degree rotating camera to assess wedges, core iron condition, field body, and to note any abnormalities. The initial inspection proved highly challenging due to the amount of oil/greasing present on the stator, particularly on TE – as the robot began slipping. At the 12 o’clock position, MD&A noted high amounts of contamination at TE step iron and body wedge system.

After discussing recommendations and repair options, the Customer opted for a partial re-stack of the core step iron and full stator rewind. Three full packs of iron and full set of 7FH2 windings were readily available as part of MD&A’s inventory. The generator field was shipped to MD&A’s Turbine-Generator Repair Facility where thorough inspection and testing of the field was performed. This allowed the field to be in a controlled climate to reduce the potential for moisture ingress during the stator repair activity duration.

The repair of this unit required that the generator be stripped of all stator windings, followed by a thorough cleaning of the stator to remove all core ferrous debris from the stator prior to performing the rewind.

The damaged iron was removed from the stator core in circumferential sections moving axially inboard from the TE step iron where the fretted iron was located. Core iron packs were removed just past the damaged section to ensure reliability for future operation of the unit.

Once the core iron was removed, new core iron was replaced in the reverse process, moving axially outboard in circumferential bands. With the new core iron in place, MD&A then axially compressed the core to the required values. A Core Loop test was performed at the completion of the partial re-stack to verify successful compression of the new core and to ensure no hotspots were present on the newly installed or original remaining core iron.

After the core iron was replaced, new 7FH2 generator stator windings were installed. All quality checks were performed according to MD&A procedures to ensure reliable future operation of the unit.

Stator Experts

MD&A has a long track record of successful generator stator inspections and rewinds on-site. You can count on MD&A’s attention to quality!

Additionally MD&A has Stator Rewind Kits available for immediate use along with new step iron laminations in stock for 7FH2 units. There are several options of on the shelf rewind kits including GE® 7FH2, 7A6, 9A4 and 324 units.

For any questions or concerns about operational issues with these large generators, or to arrange service or inspection, contact MD&A’s generator experts today at +1 (314) 880-3000 or use our Contact Form.

The post 7FH2 Partial Re-Stack of the Core Step Iron & Full Stator Rewind appeared first on MDA Turbines.

Mechanical Dynamics & Analysis has analyzed and resolved generator stator bar abrasion events that have become common on some newer GE® Frame 7F and 324, 330, or 390 generators. The damage can cause ground faults leading to forced outages and complete stator rewinds.

A principal cause of the abrasion is traceable to side ripple spring-induced damage.

All high-output, high-voltage machines experience elevated stator bar forces during operation. These forces can also be intensified by today’s start/stop operations.

OEM documents on these machines include warnings about ripple spring migration resulting in possible bar abrasion and leading eventually to stator failure. Although not all units are susceptible to these bar abrasion issues, MD&A recommends investigation and, if required, correction before the problems become critical.

[CCJ Credit]

The details

Stator bars lay within the stator core iron, and bar sparking can occur when the energized bar loses contact with the stator core. The loss of contact occurs when there are air gaps, or voids, between the bars and the stator core.

Unwanted movement or bar fluttering must be eliminated. Usually, the bars are supported radially by top filler, top ripple springs, and stator wedges. Support in the tangential direction, to avoid fluttering, is normally accomplished by semi-conductive side ripple springs or side packing.

The side ripple springs provide continual pressure and contact, compressing the bar against the stator core iron. The ripple has a 45-degree orientation to the bar as opposed to the 90-degree ripple orientation for top springs.

Proper installation of side ripple springs must maintain 80 to 90 percent contact between the face of the spring and the side of the insulated bar. This gives optimal compression to eliminate any voids between the bar and core.

Example/case study

MD&A experts found evidence of bar abrasion in an air-cooled machine containing side ripple springs and experiencing partial discharge.

Bar removal and investigation revealed clear evidence of partial discharge that could be attributed directly to side ripple spring damage.

Forces applied to the bar and spring during operation or a lapse during the manufacturing process had flared the spring’s corner, causing a sharp edge to be present resulting the damage to the wall insulation. Penetration into the side wall insulation was approximately 3 mm (0.11 in.).

MD&A found similar damage events in 2015 and 2017, leading to full rewinds. The first unit had operated just over 19,000 hours, with 700 starts.

Solution and guide

MD&A experts can inspect and analyze these side ripple spring installations to detect any potential for stator bar damage.

Replacement with smooth-corner side ripple springs should eliminate the potential for cutting into the bar insulation. It remains critical to specify the proper thickness of the ripple spring, and contact between the spring and bar should remain at 80 to 90 percent.

Stator bars need to be manufactured for proper space between the stator core and insulated bar and must account for the chosen dimensions of side ripple springs or side packing design. The bars must also be uniform down the slots.

MD&A has a long track record of successful on-site generator stator inspections and rewinds. You can count on MD&A’s attention to quality!

Additionally, our experts have Stator Rewind Kits available for sale. There are 2 options: GE® 7FH2 Stator Rewind Kit with 6” of Step Iron Stator Bars and GE® 7A6 Stator Rewind Kit.

For any questions or concerns about operational issues with these large generators, or to arrange service or inspection, contact MD&A’s generator experts today at (314) 880-3000 or use our Contact Form.

The post Generator Stator Bar Abrasion Risk and Prevention appeared first on MDA Turbines.

For Hermiston Generating Plant in Oregon, Mechanical Dynamics & Analysis (MD&A) completed a complex, multiple-component combined-cycle major inspection and overhaul project that successfully brought both turbines and both generators back to full and reliable operations.

The 474 MW combined-cycle plant was depending on the complete and efficient renewal of its Unit 2 system.

This major project demonstrates the full capabilities and product knowledge of MD&A personnel, and the organization’s commitment as a premier, fully integrated non-OEM supplier to the turbine/generator community.

It began with a full major inspection of a late 1990s vintage 170 MW GE® 7FA gas turbine and included the 7FH2 generator robotic inspection work. The GE® A-10 steam turbine and 7A6 generator would also be fully inspected and refurbished by MD&A in the same outage.

7FA Gas Turbine

MD&A mobilized and completed the disassembly process utilizing a two-shift operation. Detailed visual inspections began, coupled with detailed NDE, followed by the recommended refurbishments.

In the turbine section, first-, second-, and third-stage buckets were replaced due to rubbing wear and thermal barrier coating (TBC) loss.

First-, second-, and third-stage nozzles were also replaced due to foreign object damage, evidence of cracking, and coating loss. Inspections and similar indications revealed the need to also replace the shrouds.

In the combustion section, liners and transition pieces were replaced with refurbished sets due to TBC loss. New inner crossfire tubes and retainers were installed due to wear and outer crossfire tube packing was replaced at reinstallation.

Although no abnormal visible wear was found, forward combustion cans and fuel nozzles were replaced with customer-provided refurbished sets. Flow sleeves also showed no wear, but the flow sleeve piston rings were replaced.

Liner caps were replaced with refurbished, and transition piece bullhorn brackets were found worn and replaced with new.

For the compressor section inlet guide vanes, MD&A replaced gears, rack, inner and outer bushings, and spacers. Inlet guide vane blades themselves will need to be replaced at the next major inspection.

Rotating and stationary blades showed no damage. R-0 inlet compressor blades were replaced with a refurbished set and shims were added to stages 14, 15, and 16. The casing and rotor showed no need for immediate action, but the discharge casing retention bars were replaced.

The inactive thrust bearing showed heavy scoring and the T-1 & T-2 bearings revealed pitting and scoring, which were subsequently replaced with refurbished bearings. The active thrust bearing was cleared for service.

7FH2 Generator

For the generator, the initial scope of work was visual inspection, robotic wedge map analysis, electromagnetic core imperfection detection (ELCID), and a full battery of electrical testing.

The borescope inspection showed substantial widespread greasing and several areas that had loose hardware. The field was recommended to be removed for a more comprehensive stator investigation. After field removal, a core wedge map was performed that showed approximately 90% of the wedge system was loose and/or hollow, not meeting MD&A criteria. A full stator re-wedge, replacement of greasing blocking/ties, and axial support tightening was recommended and performed.

MD&A also provided and installed an improved the wedge design.

Prior to re-wedging, a significant amount of time was expended cleaning the core. All slots were cleaned including dovetails.

New filler material and top ripple springs were installed during the re-wedge. A modification was made to the end wedges to improve mechanical strength. The original flux probe was installed without issue, and a final ELCID was performed with acceptable values.

Based on modal bump testing, MD&A recommended that the entire collector and turbine ends have series blocking installed to reduce resonant frequency response. Saturated felt and ties were added to dampen the response.

New axial support hardware was installed, replacing the loose axial supports and hardware found during initial inspections. Locking epoxy was applied on all hardware to ensure no complications during operation.

H2 seals were replaced with new, and field collector rings were ground.

Successful electrical testing was performed at the completion of all work performed.

A-10 Steam Turbine

MD&A performed a major inspection and overhaul of the 81MW GE® A-10 steam turbine, generator stator, and field installed in 1996.

The main steam valves were also removed by MD&A and sent to MD&A’s St. Louis Repairs Facility for inspection and repairs.

MD&A specialists performed a complete steam path structural audit of the A10 steam turbine.

Although many minor diaphragm indications could be repaired by MD&A onsite, ILP diaphragms 9, 10, 11, and 13 were shipped to MD&A’s repair facility for major repairs. Stages 10 and 11 would also have inserts installed on the steam seal face due to dishing.

HP and ILP rotors remained coupled and were removed for sand blasting and NDE. Minor bucket repairs were performed on site to correct impact damage and moderate solid particle erosion.

On reassembly, MD&A performed a Topless Alignment®, and MD&A On-Site Seal Services fit and installed new diaphragm and gland steam packing.

7A6 Generator

The 7A6 air-cooled generator was disassembled and the field removed. The generator field was shipped to MD&A’s St. Louis Facility for a full rewind. In addition, MD&A’s Generator Division mobilized onsite to perform a full stator rewind.

The combined HP stop and control valve was disassembled and the cores were shipped to MD&A’s St. Louis Repair Facility for inspection and repairs. The Steam Turbine Repairs Division also received two reheat stop valve and two intercept valve cores for inspection and repair.

Stator

Concurrent with the major steam turbine inspection, an elevated workspace onsite was constructed to support the generator division for stator disassembly and reassembly work. A baseline ELCID was performed to determine integrity of the current stator core iron. No shorted laminations were noted.

The wedge system was removed, then the flex probe was carefully set aside for reassembly.

With wedges and series loop connections removed, bar removal began. Inner axial supports were left in place and prepared for the reassembly. Connection pieces were cleaned for reuse.

The stator was thoroughly cleaned to remove any contaminants from the wedge/bar removal process. A post wedge/bar removal ELCID indicated no core iron damage during wedge and bar removal.

Each core slot was cleaned, and a detailed inspection of any abnormalities was conducted. The core compression flange and all exposed areas where the end windings sit were painted with an epoxy paint for a uniform color on the compression flange.

After a thorough cleaning, the rewind began.

Bar boxes were moved to the scaffolding deck with an innovative safety-conscious method of disassembling the scaffolding roof and flying the boxes to the deck with a crane following completion of a detailed lift plan.

Each of the six circuit rings were acceptance tested, and the outside binding bands were installed.

A tapered gauge from the bar manufacturer was used to ensure concentricity was achieved on the four binding bands. Concentricity of each band is a vital step that will properly align each bar and subsequentially the end winding basket once the rewind is completed.

Two top and two bottom bars were installed to ensure alignment. Bars were fit into a shoe on the collector end and carefully transferred through the bore to the turbine end. All 72 bottom bars were installed, blocked, and tied. All 72 top bars were then installed, blocked, and tied, along with 12 new resistance temperature detectors (RTD’s).

After all bottom bars were installed, a Hipot test was performed using a high potential voltage to ensure no bar armor insulation damage. Another Hipot was performed on all top & bottom bars at the completion of top bar installation.

Wedges were then installed, and filler was adjusted at each wedge for proper radial compressive force. Axial locking pins were installed, followed by a final ELCID and brazing. The existing circuit ring copper connection pieces were re-used and brazed to respective top and bottom phase connections.

Upon completion of all rewind activities, final electrical testing consisted of winding copper resistance, insulation resistance, and a final Hipot of each respective phase. Each phase produced satisfactory resistance values.

The stator rewind activities progressed as expected throughout this project. The consistent bar shapes and robust bar design aided in completing the project without incident.

Field

The 7A6 generator field was sent to MD&A in St. Louis for testing, disassembly, coil removal, cleaning, further testing, re-assembly, and high-speed balance.

During initial electrical testing of the heavily dished collector rings, collector studs, and bore copper, the collector studs failed high potential testing. This resulted in the replacement of the collector rings which included removing the old collector rings, manufacturing new collector rings, new collector ring insulation, and reinsulating of the collector studs.

Coils were removed and sent off-site for cleaning. They were then returned and checked by MD&A.

After reinstallation, each coil received AC Hi-Pot and turn-to-turn testing.

Also, during the rewind process, the blocking was upgraded to the MD&A standard block and tie design. Turn insulation was coated, requiring a rotor bake cycle.

Electrical testing, high-speed balance, acceptance testing, and shipping followed.

Post-Outage GT Performance Analysis

MD&A issued a report that calculates the relative change in output and heat rate after the gas turbine outage. Operating data from pre and post-outage was used for the analysis.

Full-Scope MD&A

MD&A provided startup and balance support of the unit.

Our team provided full recommendations of what to look for or replace at the next outage.

This combined-cycle inspection and overhaul clearly reveal MD&A’s total service capability and non-OEM commitment with deep and focused product knowledge and experience. The precision of all MD&A divisions in support of a common goal merged into a powerful, comprehensive response, returning the facility to full and long-term operations.

With this project, MD&A has added to its impressive project resume as a holistic provider of services to all makes and models of turbines and generators, returning them to and above their original standards.

MD&A is a one-stop shop! Call MD&A about your next outage today at (518) 399-3616

The post MD&A Completes Significant Combined-Cycle Inspection and Overhaul appeared first on MDA Turbines.

In addition, the project included a full test and inspection on field, where MD&A experts rewound, applied a blocking modification, and restored the journals. Following receipt of the upgrades, the field was high-speed balanced with a thermal heat run at MD&A’s high-speed balance facility in St. Louis, MO.

We are your full-service, OEM-alternative!

View our Generator Stator Replacement video below and then call us today at (518) 399-3616 or use our Contact form.

The post New Generator Stator Replacement appeared first on MDA Turbines.

MD&A sent all 3 rotors from the steam turbine, gas turbine & gas generator to our one-stop shop, which was a huge selling point for the customer. MD&A was able to leverage the full capabilities of our state-of-the-art 250,000 square foot, Turbine-Generator Repair Facility in centrally located St. Louis, Missouri to inspect and repair the major components all under one roof.

To ensure success with this large project, coordination between all MD&A divisions was critical, as well as, constant communication with the customer. MD&A assigned a dedicated project manager responsible for all on-site services, including subcontractors, parts supply & shop services.

MD&A’s scope included a 7EA gas turbine major with a gas turbine rotor inspection & assessment in our St. Louis Repair Facility. Upon incoming inspection, the aft coupling patch ring migrated, leading to galling on the aft flange coupling #12 bolt hole, galling in forward flange coupling #10 bolt hole, wear groove and scratches on #3 journal, and circumferential lines & scratches on #2 journal. Our experts removed the damaged patch ring, manufactured & installed a new ring, and machined the ring fit.

Incoming Runouts and low-speed balance checks were performed on the gas turbine rotor with no runout issues found.

Our team observed the coating peeling from S1 buckets. They measured dovetail wear and bucket rock and found them to be well within MD&A acceptable range, therefore dovetail coating was not recommended. Bucket rock is often caused by cycling power plants that spend a considerable amount of time on a slow roll or turning gear and the result is wear between the wheel and the buckets that often abrade the fir tree surfaces causing a loose fit.  We performed an S1-S3 Bucket replacement during the repair portion and confirmed the final assembly with a low-speed balance.

Our Fuel Nozzle Services Division also performed a 7EA dual fuel Dry Low NOx System 1.0 (DLN1) Primary & Secondary Refurbishment.

The steam turbine major included removal of the rotor and shipping it to our steampath division at our St. Louis Repair Facility for L-0 and L-1 bucket replacements. During the incoming inspection, our experts found heavy damage to the Stage 2 buckets and it was determined that they needed to be replaced as well, which was agreed to by the end customer. Our team removed the buckets and performed a rotor blast cleaning to include the affected wheels. We reverse-engineered and manufactured the Stage 2 buckets and covers. We also installed L-0 buckets and reamed for new pins, machined to fit wheel, and installed L-1 buckets. Lastly, we performed the final NDE and a low-speed balance.

In addition, the scope included a full rewind on the 7A6 gas turbine generator field. After the field was removed from the stator, it was shipped to our St. Louis Repair Facility’s generator clean room. Upon incoming inspection, it was found to have Nomex® tab style end blocking with broken and torn tabs, damage to the original creepage blocking, and cracked & deformed main lead copper leaves. The field was rewound with new creepage blocking, main lead replacement, and our experts incorporated an end winding blocking modification to optimize the field’s future reliability.

After rewind, the field was balanced in our modern high-speed balance facility contained at our one-stop repair shop in St. Louis.  Capabilities of our high-speed balance bunker include the ability to excite the field while at speed in order to ensure no shorted turns when operating at load.

On-site, our Generator Specialist performed a test and inspection on the gas turbine’s generator stator, which included a visual inspection, end winding inspection, borescope inspection, bore crawl through, and inspection. The electrical testing consisted of winding insulation “megger” testing, polarization index (PI), winding resistance, DC leakage testing, and RTD testing. Our specialist additionally performed a wedge tap test to determine tight and loose wedges to produce a wedge tightness map, and lastly a thorough cleaning. A minor inspection was also performed on the steam turbine’s generator.

Lastly, our Alignment division performed a Topless Alignment® on the steam turbine which eliminates the reassembling of the turbine for “Tops-On” measurements, saving hundreds of man-hours and labor per turbine section. Our experts performed a traditional top on/tops off internal alignment on the gas turbine.

Along with having access to MD&A’s St. Louis Turbine-Generator Repair Facility “One Stop Shop”, the customer additionally benefited from choosing MD&A to execute the outage by having a single point of contact for multiple services across the entire combined-cycle platform.

Single point Project Management allowed for coordinated scheduling of concurrent work on-site and in the shop, leading to an optimized execution that was achieved on schedule. The project manager had clear and responsive communication with the elimination of multiple vendor interfaces and provided daily divisional job activity reports directly to the end customer. With the elimination of multiple vendors, there is clear warranty responsibility which gives peace of mind to the customer.  Lastly, the customer was able to derive significant value from having one vendor supply services, parts & repairs due to the inherent efficiencies of this approach.

MD&A is your full-service combined cycle overhaul provider and OEM-alternative! Services, Repairs, and Parts for your gas or steam turbine or generator. For every job, large or small, the speed and effectiveness of our response team are matched only by the depth and breadth of our engineering expertise. Call MD&A today for your combined cycle outage at +1 (518) 399-3616 or use our Contact form.

Sign Up for MD&A’s Insight Newsletter: Get quarterly our turbine-generator expert’s case studies and tips!

The post Combined Cycle Overhaul with our One-Stop Shop appeared first on MDA Turbines.

In addition, the project included a full test and inspect on the 7FH2 field, where MD&A experts applied our patented spring migration repair and blocking modification. Following receipt of the upgrades, the field was high-speed balanced with a thermal heat run at MD&A’s high-speed balance facility on St. Louis, MO.

We are your full-service, OEM-alternative! MD&A also has another 7FH2 Stator for sale!

View our Generator Stator Replacement video below and then call us today at (518) 399-3616 or use our Contact form.

The post Generator Stator Replacement appeared first on MDA Turbines.

Our mission is to ensure quality customer satisfaction and build trust with our clients, resulting in repeat business. Our team of experts is dedicated to providing quick customer support and professional expertise to our clients. Our response team is always available to assist you, and clients can easily get in touch with us at any time and from any location.

Our MD&A experts are skilled engineers and technicians who provide prompt support and innovative solutions to our clients. Our Turbine and Power Plant Generator services and repairs are quick and efficient, ensuring that your power plant runs smoothly and efficiently. Trust MD&A for all your Power Plant Generator needs, and we will ensure that your power plant is running at optimal performance.

Services

Our Power Plant Generator Services team is made up of trained and skilled experts who have the experience and knowledge to conduct full-scope electrical testing, visual inspections, and specialty tests as per customer requirements. We have a proven track record of successful projects, and our experts approach each challenge with the knowledge and skills gained from these experiences.

Outage Planning  Technical Direction  Turnkey Labor

Outage Planning 

Power plant professionals can manage their tasks, lower outage times, and increase their online time with effective planning. Our workers focus on reviewing the available objectives, performance, and reliability of the unit, and plan the outage schedule for Turbine and Power Plant Generator Services. With Maintenance Advanced Planning Services (MAPS), we compile historical data, fleet data, and OEM recommendations in a final report for the client. 

Technical Direction 

Our project managers and technical directors are experienced professionals who specialize in the many unique and complex areas of turbine-generator engineering.  Many of our TDs have a broad background of experience with many OEM equipment types, enabling them to effectively address even the most complex technical challenges.

Turnkey Labor 

We offer skilled turbine-generator mechanics, supervisors, tools, equipment, and other required services for turnkey installation, maintenance, and overhaul of the Power Plant Generator and turbines. 

Balancing & Vibration Analysis

Our advanced High-Speed Balance Facility based in St. Louis was designed with both vacuum capability and the ability to excite generator rotors at high speed, allowing the testing and balancing of both turbine and Generator rotors.  High-speed balancing has effectively shown to minimize any testing stresses during repairs, ensuring effective usage when returned to operation.

Generator Testing and Inspections 

Our generator specialists perform a comprehensive series of inspections and tests on all stator and field components. Machines are subjected to both electrical tests and visual inspections. The goal of our Generator Specialist is to compile the results from a series of applicable tests that collectively help you make decisions about the necessity and priority of repairs. 

Robotic Generator In-Situ Inspection 

Our generator in-situ inspection robot (called Air Gap-Bot) fully inspects the system without removing the generator field. Leading to shorter outage duration and reduced inspection cost.

It can perform a visual inspection, a stator wedge tightness assessment, and an Electromagnetic Core Imperfection Detection (ELCID) in order to find possible faults, shorts, material deterioration, and more.

Control and Excitation Field Engineering, Consulting & Training

We have OEM experienced field engineers which provide installation, technical support, advanced troubleshooting, training, and consulting services for gas and steam turbine controls, generator excitation, and auxiliary systems.  

Generator Excitation Retrofits 

In order to enhance the voltage protection and control of the generator, we offer multiple options for turnkey replacement in generator excitation systems. Also, we give customized solutions for brushless, static, and multiple other legacy OEM configurations. 

Operating Surveillance Program 

Our power plant generator experts conduct this program to find the leaks and various issues in generators. This system can work even when the unit is in operation, and usually takes 2-3 days to complete, based on unit complexity and size. 

Turbine System Enhancements 

Our experts conduct targeted improvement in generator system components in order to improve system performance. They offer premium upgrades in generator hydrogen systems, turbine trip manifolds, valve actuators, Overspeed systems, and hydraulic systems.

Turbine Foundation Monitoring 

We combine optical and laser measurements to gauge the custom monuments that are installed in the turbine foundation.

Center-line Installations

Our skilled project managers, craft labor, and technical experts handle center-line installations completely and cost-effectively. These installations include steam turbine-generator sets manufactured by nearly all OEMs.

Repairs 

Aiming to provide efficient, comprehensive overhaul and repair of large utility and industrial power plant generator stators and fields, we are trusted by our clients all over the world. Our facility has two climate-controlled generator clean rooms to accommodate multiple field rewinds at a time.

On-Site Stator Repair  Generator Field Rewinds

On-Site Stator Repair

Our experts provide complete turnkey stator repair services for water-cooled, hydrogen-cooled, and conventionally-cooled generators.  We can perform full Rewinds, Wedge System Upgrades, Flush & Bake Services, and more.

Generator Field Rewinds

In terms of power plant generators, we have experienced and trained winders and technicians in our Turbine-Generator Repair Facility that can accommodate generator field rewinds of any capacity, including large 4-pole nuclear units.  It has two climate-controlled generator clean rooms to accommodate multiple field rewinds at a time. We offer turnkey testing and inspection services and retaining ring change-outs.

Stator Bar Water Leaks (TIL-1098)

As prescribed in the TIL-1098 (Technical Information Letter 1098), our patented Two-Piece Clip aids in handling all possible leakage issues as well as porosity conditions of water-cooled stator bars of General Electric®.

Rotor Slot Dovetail Repair (TIL-1292)

On-site or in our Turbine-Generator Repair Facility, our experts can conduct inspection and repairs for potential cracking or fretting in the generator rotor slot dovetail surfaces, meeting all OEM requirements.

Collector Ring Machining 

On-site or in our Turbine-Generator Repair Facility, our experts can handle collector ring machining, using our single stone process for final honing and polishing. They do the task without removing the generator field from the stator.

High-Voltage Bushings & Auxiliaries

Our team of experts can simultaneously perform disassembly, cleaning, repair, and reconditioning or manufacture new multiple high-voltage bushings.

High-Speed Balance 

High-speed balancing has effectively shown to minimize any testing stresses during generator repairs, ensuring effective usage when returned to operation. Our advanced High-Speed Balance Facility based in St. Louis was designed with both vacuum capability and the ability to excite generator rotors at high speed, allowing the testing and balancing of both turbine and Power Plant Generator rotors.  

Hydrogen Seals & Housings

Trusted by customers for our short-cycle delivery, we can manufacture, modify or repair hydrogen seal rings in order to help with operational issues like excess consumption of hydrogen, extreme seal oil flow, and grounding-caused electrolysis. 

Elliptical Journal 

Our experts can provide assistance to our clients who wish to remove the unwanted side effects of steam whirl or oil whip. We do this through designing, creating, and repairing elliptical bearings. 

Tilt Pad Journal

A tilt pad journal bearing retrofit is an affordable solution for handling the unwanted side-effects of steam whirl or oil whip.

Oil Deflectors 

Trusted by customers for our short-cycle delivery, we offer total oil deflector reconditioning for long-term operational problems from improper oil seal clearances.  

Parts 

MD&A supplies high-quality power plant generators replacement parts. As a single-source provider, we take a focused approach to our personnel and assets, to provide speedy service to our clients. 

Generator Stator Bars  Collector Rings

Generator Stator Bars

We offer high-quality generator stator bars to our clients so that they can rest assured to continue operation. With MD&A’s highly skilled reverse engineering team, our state-of-the-art manufacturing techniques, and premium insulating materials, the stator bars we install will meet or exceed OEM standards.

Collector Rings

MD&A experts can manufacture a variety of designs of collector rings for your generator.  They can reuse the inner shell and replace all other components. 

Hydrogen Seal Rings & Assemblies

Our experts design, manufacture, and repair hydrogen seal rings to handle problems like excessive oil flow or consumption of hydrogen. Our inventory includes insulation components, custom bronze alloys, and garter springs. 

HV Bushings & Auxiliaries

For the steady functioning of Power Plant Generators, our team with years of experience can manufacture new or recondition multiple high-voltage bushings at once.

Insulated Bearing Rings 

With short cycle delivery and an inventory of insulation materials, MD&A experts can provide a total reconditioning option for insulated bearing rings, which can help decrease electrolysis due to grounding.

Generator Retrofits & Replacements

MD&A provides comprehensive generator replacement and retrofit packages, which provide the latest advances in generator technology.

Oil Deflectors 

We offer full reconditioning of this type in the tight oil sealing system to improve its long-term effectiveness. MD&A experts offer full reconditioning of oil deflectors for long-term operational problems from improper oil seal clearances. Moreover, we provide an extensive inventory full of dowels, body bolts, and seal tooth material.  

Miscellaneous Generator Components

Our premium stock of miscellaneous parts for a Power Plant Generator includes hydrogen seals, thermocouples, shaft grounding devices, brushes and holders, springs, sealants, RTDs, RTVs, and gaskets, among others. 

Fasteners

We provide quick service to clients with our stock of multiple washers & nuts, as well as, various types of alloys for bolting and studs.

Legacy Turbine Circuit Boards, Repairs & Service

MD&A Control Systems can supply many different OEM turbine control circuit cards. The cards work to provide modern and reliable replacements.

IBECS® System

With our easily configured HMI, our IBECS® System provides power plant monitoring with many features and benefits.

Power Plant Generator Differentiators

Power Plant Generator differentiators that make us unique:

• EXPERIENCED: Backed by decades of engineering expertise,  MD&A’s Generator Division has continuously earned customer satisfaction and trust. We operate as a convenient, comprehensive resource of knowledge and equipment devoted to generator technology. 
• EFFICIENT: Regardless of scope or OEM, and whether your needs are planned or emergent, MD&A’s dedicated professionals take pride in their efficient response, in their knowledge, and in the company they represent. We are committed to your success.
• FOCUSED: Efficiency and speed are ensured by our lean and logical approach to both assets and personnel.  This focus on ourselves helps us focus on your bottom line.

Conclusion 

In conclusion, MD&A is a leading provider of Power Plant Generators services and repairs for power generation plants worldwide. Our commitment to excellence has earned customer trust for all turbine-generator needs. We focus on delivering consistent quality and value with fast response, superior communications, and innovative solutions. We are your full service, OEM-alternative!

For further queries or to begin using our services, call us today!

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