Initial inspection revealed numerous deficiencies that needed to be remedied. Outage consisted of High Pressure/Intermediate Pressure (HP/IP) turbine section major inspection, HP control valves #3 and #4 inspection, and the left-side combined reheat valve, as well as the Ventilator valve and Blowdown valve. Low pressure A bearings #3 and #4 were also inspected and a start-up trim balance was performed.

Further, recommendations were made for maintenance and repair tasks in the future. Significant work was performed as follows:

HPIP Rotor Repairs

MD&A’s Steampath division performed on-site inspection and repairs of the HPIP rotor. Several issues were noted and resolved, as well as more significant deficiencies, particularly in the IP steampath. Repairs included the replacement of the IP stage 7 buckets, blending of the stage 1 leading edge cover and the stage 2 leading edge airfoils. Strap lapping was performed on various diameters, and low speed balancing of the rotor was performed.

Upon inspection, the original stage 7 buckets were found to be in need of replacement. MD&A replaced the stage 7 buckets with new hardware provided by the customer. The buckets and covers were assembled onto the rotor and the tenons peened. They were assembled in sequence per the customer-provided moment weight diagram. The HPIP rotor was installed in the lathe, the covers were final machined, and the tenon rivet heads were NDE inspected and accepted.

Repairs were required on stage 1 and 2 due to foreign object damage. For stage 1, MD&A’s technicians blended and polished the leading edge, cover and airfoils, thus removing any raised or rolled over material. The airfoils for stage 2 were straightened, benched back, blended and polished to remove stress risers and any raised or loose material. Rotor was low-speed balanced at the completion of the repairs.

Minor circumferential scoring was found on the inboard oil deflector diameter of the turbine end shaft end. MD&A strap lapped both oil deflector diameters to remove any raised material.

Inner Shell

A detailed visual inspection of the removed HP inner shell upper half and in-place lower half was performed by MD&A’s Steampath division. Components were closely reviewed for any signs of corrosion, erosion, foreign object damage (FOD), or other damage. As a result of the team’s findings, on-site repairs were performed, which included thermowell repairs, general stoning, blending, and polishing, and replacement of inlet snout seal rings.

Inspection revealed that the tip of the thermowells on the shell’s ID had severe foreign object damage. MD&A repaired three thermowells on the upper half HP inner shell. Two outboard thermowells were removed, replaced, and re-welded. The third middle thermowell was no longer utilized by the plant and a plug was produced, installed, and welded.

Stoning, blending, and polishing was conducted on several components where needed. On both right and left axial locating fits, minor galling and raised material was found. Stoning was performed to remedy this. The upper half left side bolt hole spot face had arcing damage due to destructive nut removal, which was blended and polished. Minor galling and raised material was found on the faces of the transverse gib key post, which was stoned. Stoning was also performed on the N2 Packing Casing axial locating fits as well as HP2- HP6 diagram grooves to remedy rough surfaces and minor galling.

Inlet snout bore seal rings were found loose on both the left and right side of the upper half and required replacement. After the client had the snout bores machined and honed, MD&A’s technicians installed new inlet seal rings.

HPIP Diaphragm Repairs

A detailed inspection was also conducted on the HPIP diaphragms. The results showed mostly dings, bends and FOD on the partition trailing edge and sidewalls, as well as minor rub and/or bent teeth on the root radial on several stages. Many of the axial steam seal faces demonstrated minor galling and raised material, which were also noted on the HJ faces of several stages

MD&A’s Steampath division performed partition trailing edge straightening, blending, and polishing on stages 3 through 7, and 10 through 12. They also performed minor partition weld repairs to diaphragm halves on stages 7 and 9. Significant foreign object damage was noted on stages 2 and 8. On stage 2, major partition weld repairs were made on both the upper and lower diaphragm halves. Due to time constraints, full repair of stage 8 was postponed until the next outage. There was enough time to conduct immediate repairs, and some preparation for the next outage. Both diaphragm halves were benched back, and corners were weld repaired. Area and contour measurements were also taken and recorded as benchmarks for future reference.

Repairs also included stoning of surfaces as well as straightening and sharpening of seals. MD&A Outage Service division replaced tip seals packing segments on several diaphragm stages.

Alignment was also performed on internal diaphragms and packing casings by an MD&A Turbine Laser Alignment expert.

Also, during the inspection, several bolts and screws we found broken, and damaged threads were noted. Bolts were replaced, and the threaded holes were re-tapped.

L-0 Bucket Visual Inspections

MD&A conducted through the hood visual inspections on the L-0 buckets of the DFLP turbine sections, looking for typical issues. These include signs of mechanical damage, foreign object damage, visible cracks, erosion, corrosion, deposits, missing or “bound-up” midspan dampening sleeves, missing/damaged side entry covers, and missing/migrated wheel dovetail pins.

The findings revealed that most components were in good working order, with one issue that required short-term attention, and several minor issues that should be simply monitored. For instance, the L-0 buckets exhaust sides / trailing edges revealed minor deposits, while the inlet sides / leading edges revealed minor water erosion of the bucket’s nose.  Minor erosion was noted on the leading side bathtub tenons. The LP inner casing above showed minor water erosion / grooving.

One more significant deficiency was noted: atmospheric relief diaphragms rubber disks were found cracked. It was recommended that these be replaced during the current outage.

The visual inspection of the L-0 buckets did not reveal any other issues or findings worth noting or monitoring.

Control Valves

Control valves CV-3 and CV-4 were removed, inspected and serviced. For #3, the bypass seat in the main disc was worn flat, preventing proper seating, and replaced with a new one. The bypass disc for this section was also worn and replaced. For #4, the bypass disc and seat were lapped to restore proper contact. Both bypass discs were also machined to achieve bypass lift per manufacturer’s design specifications. Main seat on both #3 and #4 were lapped to restore 100% contact.

A hydraulic fluid leak was discovered on the CV-4 actuator, leading to replacement. The coupling rod was also replaced, and MD&A machined the rod shoulder to achieve proper clearances

Combined Reheat Valve, Left Side

The combined reheat valve, left side was disassembled, cleaned, inspected and had work performed on major components. The anti-rotation pin hole on the stop valve stem was found oversized. To remedy this, the valve stem and nut were replaced. Significant lapping was required on the reheat stop valve seat and PSH gasket fit to restore 100% contact.

Auxiliary Valves

The Blowdown valve and Ventilator valve were inspected during the outage, and both required repairs. Inspection of the Blowdown valve revealed that the stem and seat were unevenly worn. Both were replaced. Common wear parts on the Blowdown valve and the actuator were noted as worn and replaced. The piston rod bushing inner wall on the Ventilator valve was breaking apart and replaced with a new one.

Conclusion

Detailed above are just many of the significant and minor repairs that were completed based on a thorough inspection by MD&A’s experts. The overall size and success of this particular undertaking cannot be underestimated. In addition to inspection, and repair, MD&A provided single-point project management, which allowed for efficient and coordinated scheduling of all resources involved in the project.

MD&A is a full-service, OEM-alternative, and is respected and utilized worldwide for projects ranging in size and complexity. We are the service provider of choice for power generation asset owners based on their extensive experience, responsiveness, professionalism and dedication to getting the job done both quickly and properly. Above all, MD&A is proud to be a dependable one-stop solution for virtually any power-generation inspection, maintenance and repair need – within the domestic US, and at Global locations worldwide.

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

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In this unit, the HP-IP section contains 12 stages. LPA and LPB each have 7 stages per flow, stages 13 through 19.

All LPB components were sent to MD&A’s Turbine-Generator Repair Facility in St. Louis, MO for immediate incoming inspection, analysis, and recommendations.

Couplings and journals

The rotor was blast-cleaned followed by visual, non-destructive examination, and dimensional assessments.

Turbine-end and generator-end couplings had minor rust and pitting on the faces and outside diameters, and numerous coupling holes showed moderate galling. MD&A would remove the galling to prepare for proper on-site reassembly. The generator end rabbet fit was peened and machined to maintain diameter and remove .002 in. runout when operating on both journals.

The two journals, T5 and T6, had moderate surface rust, pitting, radial scoring, and between .002” and .004” taper. Both were machined to remove the taper and damaged material, and oil seal lands were strap lapped.

Buckets

All rotor rotating stages had varying degrees of pitting and foreign-object damage on buckets and covers, including the outside of the roots and tenons. Magnetic particle NDE was performed on the rotor, liquid penetrant NDE was performed on the L-1 titanium notch buckets, and phased array ultrasonic NDE was performed on the L-0 finger dovetail pins. NDE reports confirmed corrosion pitting on all stages but revealed no crack-like indications. Moderate to severe erosion was noted on the L-1 tenons and L-0 buckets.

Minor repairs were performed on stages 13 through 18. Leading and trailing edges were straightened and blended, and polishing removed foreign object damage.

Six buckets with severe tenon erosion were replaced on the stage 18 turbine end (TE), including the titanium notch blade. Stage 18 (L-1) TE and generator-end (GE) tenons were high-velocity oxygen fuel coated with chromium carbide to slow the progress of erosion.

At stage 19, the L-0 row, both the TE and GE buckets had heavy erosion on the discharge side of the leading edges. Due to the long lead time for bucket replacements, MD&A experts recommended annual, in-hood inspection of erosion while procuring new buckets for replacement at the next major outage.

Diaphragms

NDE (MT and PT) was performed on the diaphragms. Common to all was moderate pitting on the partitions, setback faces, appendages, horizontal joints, and diaphragm body.

Of highest concern was pitting on the partitions. This had created small holes near some trailing edges.

Also noted was a large amount of missing hardware. Several lower half diaphragms did not have support blocks, and no joint bolts were present for stages 13 or 19.

Stage 13, the first low-pressure stage, is a bolted assembly consisting of both the turbine-end and generator-end diaphragms. The heavily eroded appendage was weld repaired near the joint where damage was most severe. High spots from FOD were removed and trailing edges were hand-blended and straightened. Indications found on previous Inconel restorations were also repaired.

The base material of the stage 14 partitions had moderate to severe pitting on both the concave and convex sides, which was repaired. High spots from FOD were removed and trailing edges were blended and straightened. Four new support blocks and new keys were provided.

Stage 15 partitions had moderate erosion and pitting. Pitting near the thin trailing edges had created small holes. If not repaired, more holes would appear and pieces would liberate and move downstream. Major Stage 15 repairs, therefore, became critical. MD&A specialists repaired the trailing edges by cutting back to a minimum thickness of 0.125 in. and welding new partitions in place, hand-working to match the incoming profiles. A damaged root radial seal was also repaired. Support blocks and various screws and keys were provided.

Although not as severe, small holes were found near the trailing edges of stage 16, primarily near the corners. Stage 16 joint blades were more severely damaged. All affected areas were cut back and repaired with Inconel. The remaining blades were straightened.

At stages 17 and 18, there was moderate damage to the joint blades, causing trailing edge deformation and small tears. These were weld-repaired, as was all FOD.

MD&A straightened and weld-repaired damaged trailing edges and repaired all NDE indications at stage 19.

All damaged packing retaining pin holes were weld-repaired and extra stock was welded to the crush pins to be fit on-site, to expedite reassembly. Broken diaphragm key screws were replaced, and new keys were made to replace those missing.

Recommendations

After all the repairs were completed, a high-speed balance was performed on the LPB rotor. The rotor was cleaned and prepared for shipment.

MD&A analysts recommended that the site monitor any pitting on the rotor and diaphragms and any progression of tenon erosion. Major future repair to stage 14 diaphragms should be considered.

For the stage 19 L-0 buckets, annual in-hood erosion inspections should be performed until near-term replacement.

MD&A completed both analysis and repair of this spare LPB unit on schedule and returned the unit ready for full service.

MD&A experts focused on detailed analysis and needed repair while leaving the owner/operator with both near-term confidence and a long-term plan for reliable performance of this critical G2 design unit.

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

The post Spare LPB Rotor and Diaphragm Repairs appeared first on MDA Turbines.

Our engineers make steam turbine repairs and recommendations based on the owner’s intended operating plans for the unit. With over fourty years of experience in steampath engineering, our aim is to give high-quality service and assistance to our customers.

We maintain a staff of experienced full-time steampath engineers who specialize in the repair of stationary and rotating components. We are committed to providing high-level Steam Turbine Repairs.

Why choose MD&A

For over 40 years, 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.

MD&A is easy to work with. We provide immediate access to expert help when you need it, where you need it. Around the corner or the globe, we ensure prompt, thorough communication and follow-through. For every repair job, large or small, the speed and effectiveness of our response team are matched only by the depth and breadth of our engineering expertise.

Find out today why so many power generators use MD&A to maximize operational effectiveness.

Steam Turbine Repairs

The Steam Turbine Repairs that we offer include the following:

1.     Stationary Component Repair

We specialize in the repair of blade rings and diaphragms and provide full-time on-site supervision during your steampath turbine repairs. From small-scale weld repairs to developing new diaphragms, we provide a comprehensive list of restoration services.

2.     Rotating Component Repair

We provide an array of repair services for rotating components to power plant owners. Our team of experts has high-quality steam turbine rotor welding experience. From minor weld-specific repairs to total rotating component replacement, we provide multiple types of Steam Turbine Repairs.

3.     Rotor Straightening

Our Turbine-Generator Repair Facility provides proprietary distortion correction for straightening bowed rotors in steam turbines. We provide computer modeling techniques and recommendations, plus an engineering analysis to find the root issue.

4.     Machining Services

We offer a wide variety of steampath repair equipment and field machining services to use on-site. Our Turbine-Generator Repair Facility machining capabilities include in-shop and on-site repair horizontal joints for turbine casings, defective rotors, valves, or other turbine-generator components.

5.     Portable Machine Shops

We have multiple portable machine shops available for use during plant projects. Clients can also use these shops during an outage. Our shops are available in portable Conex trailers and are fully stocked with drill passes, metal grinders, lathe, and many other essential tools.

6.     Casing/Shell Analysis & Renovation

Our engineers offer multiple steam turbine repair services and engineering to help determine the root cause behind casing/shell failure. Our capabilities range from computer-aided “stress” analysis, metallurgical testing, and innovative solutions to complete turnkey repairs and operating software.

7.     Distortion Correction

Our experts in the Repairs Division provide proprietary distortion correction techniques and procedures to permanently address issues associated with out-of-round shells, nozzles, and other critical steampath components.

8.     Westinghouse® Horizontal Throttle Valves

We provide upgrade and restoration services specifically for the existing design problems in the Westinghouse® horizontal throttle valves. We offer full-service, one-stop valve repair, and upgrade of all steam valves.

9.     Bearing Ball Ring Repairs

MD&A’s Bearings, Seals, and Hydraulics division performs precise bearing ball ring repairs utilizing our horizontal bore machine. We provide a complete restoration to the spherical fit and can perform checks to ensure proper assembly on site.

10.     Turbine Valve Actuators

Our experts can provide complete Rexroth® hydraulic actuator refurbishment. We maintain an inventory of retainers, seals, and disc springs to handle short-cycle turnaround requirements. To assure a seamless transition to system operations, we will perform a documented functional test of your actuator.

11.     High-Pressure Valve Repair

We offer inspection, restoration, upgrades, and repair services of utility and industrial high-pressure valves and components.  We offer full-service, one-stop valve repair, and upgrade of all high-pressure steam valves.

12.     High-Speed Balance

Our high-speed balance facility is one of the most modern balance facilities which was designed with vacuum capabilities and the ability to excite generator rotors at high speed. This allows our engineering specialists to handle turbine and generator-related balancing and testing effectively.

13.     Control Pac Power Actuators

MD&A provides complete refurbishment and functional testing of power actuators to reduce the need for field adjustments and eliminate variables when troubleshooting operational issues. As part of our steam turbine repair services we offer spring can refurbishment, servo testing, short cycle delivery, spare parts inventory, and stop valve bypass refurbishment.

14.     MHC Operating Governor

We offer functional testing of steam turbine MHC operating governors to decrease field adjustments during start-up. We maintain worm gears, pilot valve types, programmable replacements, incremental upgrades, and performance monitoring diagnostic instrumentation. We also provide short cycle delivery and performance monitoring diagnostic instrumentation.

15.     Steam Seal Regulator

Our Bearings, Seals & Hydraulics Division can refurbish your steam seal regulator. We use calibration and functional repairs to verify the effectiveness of the steam turbine repairs. We also maintain an extensive stock of pressure bellows, seats, high-pressure steams, and piston rings.

16.     Tapered Land Thrust

MD&A’s Bearings, Seals & Hydraulics Division can manufacture, and repair tapered land thrust bearings. We can provide material upgrades, fixture profiling, instrumentation in performance monitoring, and short cycle delivery.

17.     Control Rotor

MD&A’s Bearings, Seals & Hydraulics Division offers cost-effective control rotor services. We also offer critical fit area restoration, pump impeller repair, dynamic balancing, journal grinding, and governor impeller sleeve manufacturing and repairs.

18.     Overspeed Governor

MD&A’s Bearings, Seals & Hydraulics Division offers cost-effective overspeed governor adjustment services. We also offer short cycle delivery and a useful range of specialty spare parts.

19.     Elliptical Journal

We design, repair, and manufacture elliptical bearings to remove the steam whirl or oil whip side effects of your steam turbine. We also provide short cycle delivery, insulation mounting and spherical mounting restoration, and performance monitoring instrumentation.

20.     Tilt Pad Thrust

A tilt pad thrust bearing retrofit is a cost-effective solution when sole plate settling or other foundation changes have created poor alignment conditions. We offer clients predictable bump check shim sizing and complete assembly reconditioning.

21.     Tilt Pad Journal

One of the steampath turbine repair services we offer is tilt pad journal bearing retrofits. A tilt pad journal is useful for managing the effects of steam whirl or oil whip conditions. We offer complete assembly, provide material upgrades, performance monitoring instrumentation, and short cycle delivery.

22.     Bronze Turbine Seal Rings

The Bearings, Seals, & Hydraulics Division at MD&A provides a range of bronze turbine seals rings that include manufacturing to spec, in-house stocking of custom alloys, and expedited delivery on a short cycle.

23.     Oil Deflectors

MD&A Bearings, Seals & Hydraulics Division offers complete oil deflector reconditioning to assure the long-term integrity of a tight oil sealing system. Our inventory includes seal tooth material, dowels, steam painting/cleaning, and body bolt components.

24.     Advanced Rotor Welding

We offer both in-kind and upgraded weld filler materials that address many of the most common operational and stress-related failures.  We provide full turnkey weld repair and reconditioning services to include equipment inspections and damage assessment, weld repair solutions, baseline, and weld repair geometry finite element analysis, as well as root cause failure analysis.

Conclusion

Our skilled and experienced team of experts is invested in providing high-quality testing and steam turbine repair services. With our help, you can improve the operating conditions of your unit and discover any underlying issues. Talk to one of our experts and discover all the repairs we offer, get in touch with us as soon as possible.

Check out our video: Steam Turbine Capabilities.

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