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.

MD&A provided all tooling, supervision, and labor to perform the planned generator major inspection outage scope.

This generator life extension project exemplifies MD&A’s position as a preferred non-OEM one-stop organization throughout the turbine-generator industry.

Generator enclosure

After removal of all attachments, MD&A experts held the critical lift meeting and removed the 24,000 lb generator enclosure and installed all FME covers, removed upper half T4 and T5 bearings, and prepared the base for generator field removal.

The field would be prepared and transported to MD&A’s Turbine-Generator Repair facility in St. Louis, MO. The T4 and T5 bearings and inner and outer oil deflectors would be transported to MD&A’s Bearings, Seals and Hydraulics division in Euclid, OH for inspection and repair.

Scaffolding was then installed for the generator rewind activities.

Coolers were removed from the TEWAC assembly and cooler heads were disassembled. New isomode pads were prepared for the reinstall.

Stator

This was a planned stator rewind, scheduled as preventive maintenance due to significant observed partial discharge. Over time, this could lead to a ground fault condition and forced outage.

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

The existing flat wedge system was removed by traditional methodology and MD&A procedure.

Top bars were then removed without issue, using come-alongs to remove the bars out of individual slots. Bottom bar removal was completed in the same manner. Significant levels of partial discharge were found on several bars.

Following full visual inspection, all connection ring blocking and ties were removed and replaced with new conforming material. A post-disassembly ELCID was performed to ensure no damage to the core iron. Each of the 72 core slots were cleaned of all contaminants and thoroughly inspected.

A core knife test determined the need for complete stator core tightening, completed by MD&A procedure. At the completion of torque activities, an additional ELCID was completed with satisfactory results.

Once received, binding bands were aligned axially and made concentric to the stator core. Three bottom bars were then fit into slots 120 degrees apart to ensure proper alignment. Two top bars were also aligned with the pitch of the bars to ensure the top and bottom bar series plates were properly aligned.

A thin layer of insulation was installed in each slot, and bottom bars were then installed and bottom-bar testing was performed.

A total of six dual-element RTDs were removed during disassembly and were replaced with twelve new dual-element RTDs and operation was verified.

All top bars were then installed, blocked and tied, with no issues.

A tapered wedge and slider design with a top ripple spring was selected to provide sufficient radial pressing forces. Following all winding activities, a final ELCID was performed to ensure no damage to the core iron.

After brazing, a winding resistance test was performed to ensure each of the three phases produced similar resistance values, and all other electrical testing was completed with good results.

Field

Following removal of the generator field the customer opted for a generator field exchange. We sent a refurbished field to site that had been completely rewound with the latest in rewind technology. The field forging had undergone NDE and inspections to ensure long term viability, along with it being high speed balanced with a full heat run to ensure no shorted turns. The exchange of the generator field produced a shorter outage duration which allowed for the customer to be back online sooner.

The original generator field was transported for complete inspection and rewind. On arrival in St. Louis, the field received in-depth visual and mechanical inspection. Three-dimensional scanning and hand mechanical dimensions were obtained.

During disassembly, indications were found on a few field body wedges, and some material damage was found on both retaining rings. All field coils were removed and sent for cleaning.

The cleaned coils were determined fit for service and reinstallation began.

Each installed coil was HI-POT and turn-to-turn tested. A baker surge test was also completed on each coil. During the rewind process, the MD&A standard strap and design blocking was installed. Turn insulation was coated, requiring a rotor bake cycle. After the bake cycle, a full set of electrical tests was completed.

The field was then moved from the clean room to the shop floor to install retaining rings and complete the electrical testing. It was then moved to the high-speed balance facility. After balance, it was staked and painted and prepared for exchange sale.

Isomode Pad 

During this project, the TEWAC assembly was removed. Mating surfaces with the generator enclosure were cleaned and weatherstrips were installed. Generator cooler heads and all piping were cleaned of corrosion and buildups, and new gaskets were installed.

The generator stator was raised to remove the old isomode pads and shims. The MD&A team cleaned the area and installed new isomode pads with pre-existing shims.

The TEWAC assembly was then reinstalled.

Summary

All MD&A inter-divisional work was performed on schedule without any injuries or accidents.

There were no issues with turbine-generator synchronization during startup.

Once again, the MD&A organization drew on its experience and multi-divisional expertise to complete a major inspection and repair project and ensure owner/operation confidence in continued unit operation.

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

The post 7A6 Generator Isomode Pad Replacement with Major and Rewind appeared first on MDA Turbines.

Stator Rewind

MD&A performed a complete rewind of the generator stator during this outage. The rewind kit supplied by MD&A included new stator bars, connection rings, and end winding support components.

The rewind process began with the removal of the stator wedges and stator bars. Following bar removal, the stator slot walls and core vent ducts were cleaned and prepared for bar installation. The core was both visually inspected and electrically tested using an Electromagnetic Core Imperfection (ELCID) test to identify any shorted laminations that could lead to future overheating and damage. ELCID tests were performed three times throughout the rewind process with no relevant indications found.

The winding installation included the replacement of the original end winding supports and connection rings. Additionally, Glaskyd sausage (conforming material) was installed in place of the original radial rings between the top and bottom bars in the end winding. Conductive side ripple springs were installed to ensure proper electrical contact between the slot wall and the bar. Following bar installation, a contact measurement test was performed to ensure the bars were properly grounded to the core.

New connection rings were then installed, and all series and phase connections were brazed using induction heating. The bars were appropriately blocked, and the series loops were insulated with two-piece molded caps filled with insulating epoxy filler. Following stator slot wedge installation, all final electrical tests were completed with excellent results.

Field Rewind

Once removed from the stator, the generator field was identified with damaged end-winding blocking. The field was then sent to our Turbine-Generator Repair Facility in St. Louis, MO.

Incoming electrical testing was completed once the field arrived in St. Louis, confirming multiple shorts within the field winding. After the retaining rings were removed and the unit was inspected, MD&A recommended a full rewind to remove the shorted turns and properly adjust the end-winding blocking. After the rewind was authorized by the customer, the unit was stripped and cleaned. During this time, all removed components underwent a complete visual and NDE inspection. Indications were noted on one of the snap rings. Ultimately, the customer elected to have both snap rings replaced at the same time.

After the copper windings were removed, electrical testing was completed on the bore copper and collector rings with acceptable results. The coils were blast cleaned and inspected. Following the inspection, the coils were deemed suitable for continued operation and returned to service. The wedges were blast cleaned and sent for NDE inspection. The field body was blast cleaned and underwent NDE inspections. All NDE results were satisfactory, and the field body was repainted. The field forging and field body wedges were returned to service.

After each coil was re-installed, an AC Hi-Pot test was performed, and an AC turn-to-turn test was completed. A baker surge test was then completed on each coil to ensure that there were no shorts present in the winding.

The turn insulation was coated on one side with heat-cured glue. This glue required a bake cycle of the rotor after it was wound. After the bake, a full set of electrical tests were completed and the unit underwent a high-speed balance, two heat runs (with a flux probe test before each heat run). All test results were acceptable.

MD&A is a full-service, OEM-alternative for generator service, parts, and repairs with a 35+ year track record of successful generator stator and field repairs. All inspections and necessary repairs are completed by our experts in a timely manner that allows units to be placed back online on an expedited basis.

Call MD&A today for any generator repair at +1 (314) 880-3000 or use our Contact form.

View the video to see how you can minimize costly outages by having our expert technicians perform your next full stator rewind.

The post Comprehensive Generator Stator and Field Rewind appeared first on MDA Turbines.

The customer contracted MD&A to perform the inspection and emergent repairs on a tight schedule. Our industry experts completed the work on time maintaining full customer communication throughout the outage utilizing our on-site project management.

For the gas turbine, all combustion and hot gas path components were removed, cleaned, and inspected. All required hardware was provided by MD&A. Our San Antonio Service Center, which is our Gas Turbine Parts Service Facility, refurbished all combustion parts of fuel nozzles, combustion system liners, liner caps, transition pieces, and flow sleeves.

The stage 1 nozzle was replaced with a new assembly. The site team replaced both the right and left stage 1 forward wheelspace thermocouple guide tube assemblies. The stage 2 and stage 3 nozzle segments were also replaced. New shroud blocks and new installation hardware were provided for all stages. Moderate fretting was observed that warranted the replacement of the exhaust frame flex seals.

Simultaneously, MD&A experts removed both turbine-end and collector-end upper half end shields to perform a generator minor inspection consisting of stator and field visual inspections, including in-situ robotic inspections, ELCID, and electrical testing.

The Generator Specialist immediately recognized that the stator had significant connection ring damage that could have led to catastrophic damage had it continued to operate.

The solution: MD&A expeditiously removed, reverse engineered, and replaced the damaged components with no impact on the overall outage schedule (5 days total repair time).

Scoring was identified on both the turbine-end and collector-end journals. The lower half bearings had moderate abrasion/scoring. Minor babbit damage was also noted. The turbine-end and collector-end hydrogen gas and air side seals were found in poor condition and replaced.

Winders were mobilized to perform numerous tie repairs on each end of the unit and connection ring replacement on the collector end with the rotor still in place.

As a result of MD&A’s impact testing and modal analysis, additional blocking and ties were made on the connection rings to ensure the unit will not see this type of problem again.

At project conclusion, comprehensive reports were provided listing each step of the process and its engineering rationale, along with detailed analysis and long-term predictions and recommendations.

MD&A site and shop repair teams worked closely together to deliver first-class service. MD&A provides a one-stop shop solution for turbine & generator services, parts, and repairs.

Call our MD&A Gas Turbine Services today at (518) 399-3616 or use our Contact form.

The post Coordinated 7FA Hot Gas Path and 7FH2 Generator Inspection and Repair appeared first on MDA Turbines.

Rotor field inspections can either be performed on-site or in a shop environment.  Repairs generally require the rotor field to be transported to a qualified repair facility. 

MD&A has developed a field pulling & support system to address 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.

The MD&A system consists of a modular work platform using adjustable rotor field trolley carts to efficiently and safely extract the field from the stator core, providing a stable work platform for on-site inspections and sufficient length to enable crane access to lift the field for off-site repair transportation.

Key features of the system include:

• Modular design work platform for expedited setup/teardown and efficient transportation on standard trailers
• Overall platform length and height can be adjusted based on site and workscope requirements
• Tongue and groove work platform connections and integrated trolley cart rail system provide seamless transitions between platforms
• Wide walkway wings on left & right sides enable worker & equipment access
• Modular safety rail system allows flexible scaffold stair access based on site arrangement
• Adjustable trolley carts use low-friction, self-guided rollers for safe and fast positioning of the field on the platform
• The system is very stable and is rated for continuous use with steady wind speeds up to 30 mph (with minimum 3x factor of safety)

MD&A offers a complete suite of parts, repairs, and services solutions for gas turbine fleets. We focus on delivering consistent quality and value with fast response, superior communications, and innovative solutions.

Call our MD&A Gas Turbine Services today at +1 (518) 399-3616 or use our Contact form.

The post Generator Field Support Platform appeared first on MDA Turbines.

First unit:  This was a major outage and generator test & inspection. In addition, this unit was retrofitted with a new rotor, bearings, and steam path components that required machining, including installing and fitting new nozzles. MD&A provided Project Management, Technical Direction, a Controls Engineer, and a Vibration Engineer for startup and balancing.

In order to maintain the outage’s schedule, MD&A worked closely with the OEM’s engineering team to ensure that the new retrofitted components were installed correctly and to resolve any technical or engineering issues quickly. MD&A’s knowledge, experience and our skilled project manager and technical adviser resulted in this successful outage.

MD&A’s Repairs Division personnel performed onsite final machining of the nozzle plates and their associated shell locations. Our repair technicians also performed on-site diaphragm repairs.

MD&A also provided a packing installation specialist to install and final machine new upgraded packing.

To support the major outage schedule and expedite the on-site work, MD&A sourced equipment locally to overcome the time required to get the specialty tooling and equipment trailers through Colombian customs.

This unit was started up without incident and has been operational since.

Another unit: MD&A provided Project Management and Technical Direction on a Steam Turbine Generator (STG) major inspection and performed Generator testing and inspection. MD&A also provided a balance engineer, Topless Alignment®, and start-up commissioning support through our Turbine and Generator Controls Division.

The steam turbine had not been inspected for 23 years. Using MD&A’s pre-outage planning processes and experience, the execution team immediately started working to identify & mitigate potential project risks. One example was special tooling, which needed to be located and prepared for use.

After the balancing work was performed, the machine was started up smoothly, synchronized, and brought to full load. This unit has been operational without issue since this start up, after 23 years without maintenance.

Another unit: MD&A worked this unit and the one above in parallel to minimize the impacts on schedule caused by the emergent work.  MD&A provided Project Management, Technical Direction, and balance support at start up for this valve, bearing, and turning gear inspection.  MD&A also supported conversion of the Mechanical Hydraulic Controls (MHC) to Electro-Hydraulic Controls (EHC) (with the exception of the mechanical overspeed trip, which was retained).

This unit was started up without incident and has been operational ever since.

Last unit:  This major outage was similar to the other unit’s scope including valve, bearings, and turning gear, but was expanded to include generator bearings and coupling alignment. As was the case for all units, a lube oil flush was performed. For this start up, vibration data was analyzed remotely by MD&A, saving the customer the mobilization cost for the vibration specialist.

This unit was also started up without incident and has been operational ever since.

Epilogue: These successful outages demonstrate the full-service capability, responsiveness, and flexibility that MD&A can provide. The customer was very appreciative of our flexibility and our ability to adjust our execution plan as required to support the overall outage plan.

Throughout the U.S. and around the globe, MD&A provides responsive support, thorough communication, and excellent execution, making MD&A the service provider of choice for numerous power generation asset owners who desire a one-stop solution for all of their turbine-generator needs.

Call MD&A today at +1 (518) 399-3616 or use our Contact form.

Also be sure to sign up for our MD&A Insight e-newsletter delivered quarterly.  Fill in sign up form on the left-hand side and hit SUBSCRIBE!

The post Global Multiyear Major Outages appeared first on MDA Turbines.

Because the nature of the forced outage was not fully known when the job was awarded, the scope of work initially was incomplete. Despite the uncertainties, MD&A’s experienced technical team quickly evaluated the damage and designed a comprehensive scope of work.

As part of its work, MD&A’s gas turbine maintenance team both opened and closed the gas turbine. In addition, the team removed the original rotor and shipped it off-site for refurbishment and high-speed balance.

As well, MD&A removed the generator field and sent it to our St. Louis facility for a complete test and inspection, and high-speed balance before being returned to site.

The scope of work included:

Site Work Services

• GT Major Inspection & Rotor Removal
• Generator Major Inspection and test & inspection – the insulation was repaired, flux probes installed and completely re-painted inside
• Stage 9 Stator Hook Fit Mod- removal of Upper & Lower Compressor Casings
• Installed New Electronic Gas Valves – removal of old Hydraulic Gas Valves
• Remove Existing Liquid Fuel System, and associated support systems, such as Atomizing Air and Water Injection – A Controls Software Upgrade to eliminate these control sections
• Accessory and Load Gear Refurbishments
• Exhaust Frame Repairs

Shop Work Repairs

• Gas Turbine Rotor Inspection
• Remove and Inspect 1st stage buckets – Apply coating for excessive rock and repair Aft Angel Wings
• Replace out 2nd stage buckets
• Compressor Blending
• Refurbish HGP Components, Combustion Hardware
• Generator Field Rings Off Inspection, test & inspect, and high-speed balance
• Gas Turbine rotor high-speed balance

New Parts

• 2nd Stage Buckets
• 2nd Stage Shroud Blocks
• Consumables & Hardware
• Auxiliaries
• Exhaust Plenum

MD&A also performed major repairs on the turbines accessory system, such as refurbishment of Accessory & Load Gears, replacement of turbine compartment vent fans, rebuilding of Exhaust Ducting, replacement of Exhaust Expansion Joints, as well as removal of hydraulic overspeed bolt and replacement with redundant electronic overspeed protection.

MD&A’s specialized services range from Combustion, Hot Gas Path and Major Inspections, as well as, Compressor & Turbine Rotor Repairs to Plant Performance Testing and Analysis. We also provide turbine internal alignment to your gas turbine, along with vibration analysis and balance (low-speed & high-speed.)

Call our Gas Turbine Services at (518) 399-3616 or use our Contact form.

Read the Combined Cycle Journal (CCJ) article.

The post Gas Turbine Major and Generator Test & Balance appeared first on MDA Turbines.

Our reputation for accuracy and reliability in power plant services has spanned over 30 years. Our technical expertise and effective project management will get the job done on time and within budget.

MD&A provided our customer with a replacement 7FH2 generator field. MD&A’s gas turbine maintenance team removed the original generator field from the site and shipped it to our St. Louis turbine-generator repairs shop for refurbishment. As well as, we sent the new generator field to St. Louis for a complete test and inspection, and high-speed balance before being brought to site.

The scope of work also included:

• The replacement generator field was removed from a unit in storage, and sent to the St. Louis Repair facility, and subsequently installed at the customer site.
• The unit was re-assembled with a new 7FH2 field with the existing #4 bearing installed and a new #3 bearing. Both were cleaned and measured, before installation.
• All new oil deflectors were used on both ends, inner and outer.
• The coupling faces were cleaned, inspected, and found to be in good condition. MD&A performed a 16-point alignment.
• New hydrogen seals were lapped and installed with existing cases.
• The air shields were cleaned and reinstalled and torqued to OEM specifications.
• The generator air test was performed, and the results were within acceptable limits.

After MD&A performed its checks, the unit started up without issues.

The gas turbine maintenance team replaced the faulty field with the new one under very difficult circumstances during the peak of the outage season. MD&A made this project happen in a few weeks from start to finish.

MD&A also performed minor repairs on the customer’s steam turbines as well, including a turning gear replacement and thrust bearing adjustment.

MD&A’s specialized services range from Combustion, Hot Gas Path and Major Inspections, as well as, Compressor & Turbine Rotor Repairs to Plant Performance Testing and Analysis. We also provide turbine internal alignment to your gas turbine, along with vibration analysis and balance (low-speed & high-speed.)

Call our Gas Turbine Services today at (518) 399-3616 or use our Contact form.

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