Many units in the combined cycle setup, which can be comprised of two MS7001FA gas turbines and a D11 steam turbine, are also equipped with 7FH2 generators. Many of these machines have unbolted babbitted hydrogen seals. If there’s any contamination of the oil or improper assembly, those conditions may cause the unbolted seals to tilt, which could lead to a hydrogen leakage and oil ingress into the generator.

The OEM recommendation is to upgrade the hydrogen seals to a bolted style which involves replacing the housings. MD&A offers a more cost-effective option to modify the existing housing to accept bolted seals.

The customer requested an upgrade of their existing unbolted hydrogen seals to a bolted design for two of the two generators.

MD&A supplied the two casings with a bolted style along with the upgraded hydrogen seals and all the hardware required. We also supplied a spare set of D11 valve parts and hardware.

For upcoming maintenance, MD&A also supplied one set of 7FA refurbished third-stage hot section parts (including buckets, nozzles, and shrouds).

Our Bearings, Seals & Hydraulics division stocks a large number of hydrogen seals at our Euclid, OH facility, and we can service any size machine. If we don’t have the seals in stock, our skilled technicians can fabricate them using materials we have in the shop.

When a customer orders a set of hydrogen seals from us by part number, we don’t just manufacture the seals to the standard original size. Instead, we always have a dialogue with the customer to learn what their journal size is and what their housing cavity thickness might be. Then we custom-size the seals to fit properly. Some of our craftsmen have been doing hydrogen seals for 20-plus years, so they are well-seasoned and trained in doing the work.

Since 1984, MD&A Bearings, Seals & Hydraulics Division has designed, manufactured, retrofitted, and repaired hydrogen seal rings to correct operational issues such as excessive oil flow, excessive hydrogen consumption, and electrolysis. We have also developed a level of service designed to substantially reduce the manpower traditionally associated with the field ­fitting of critical seal assemblies.

Call our MD&A Bearings, Seals & Hydraulics division today at (800) 446-4776 or use our Contact form.

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The horizontal bore machine, shown in the video below, is just the latest example of how MD&A ensures that you get the best people, the best equipment, and the best service available anywhere.

For additional information call MD&A’s Bearings, Seals & Hydraulics Division today at (440) 946-0082 or use our Contact form.

We remain committed to being the power industry’s trusted partner for refurbishing and manufacturing high-quality turbine bearings. Our experts are continually looking at ways to broaden our capabilities so you can maximize uptime. It’s how we retain our leadership position in the industry and our reputation for great products and top-notch customer service.

The post Investing in Journal Bearing Ball Ring Repairs appeared first on MDA Turbines.

The Turbine end shaft end was bent and found to have a 0.007” total indicator runout (TIR) at the coupling outer diameter. The generator end shaft end was bent and found to have a 0.053” TIR at the coupling outer diameter. MD&A was able to straighten both shaft ends to within 0.0015” TIR using a combination of thermal and machining straightening processes. Then, MD&A completed the final high-speed balance and final machining of the shroud covers.

Shaft End Thermal Straightening
The rotor thermal straightening process included an initial rotor stress relief and multiple thermal straightening iterations. MD&A expert technicians performed detailed visual, dimensional, and non-destructive examination (NDE) of the rotor forging before and after each thermal process to confirm that no issues were present. Rotor NDE inspections consisted of both hardness testing and wet fluorescent magnetic particle testing.

Based on the amount of shaft end distortion and the experience and expertise of MD&A technicians, it was recommended carrying out an initial stress relief of the rotor and additional thermal straightening iterations of the shaft ends to further reduce the shaft end runouts.

The initial stress relief of the rotor forging was performed on both shaft ends to relieve any internal stresses and determine the final relieved state of the shaft end runouts. This involved removing all installed blades and seal strips, stress relieving the rotor, blast cleaning, NDE, hardness checks, and runout checks along the length of the rotor.

Additional thermal straightening iterations were also performed on the generator end of the shaft to further reduce the amount of runout. This involved thermally moving the shaft end, stress relieving the rotor, blast cleaning, NDE, hardness checks, and runout checks along the length of the rotor.

Due to the high temperatures of both couplings during the stress relief processes, a vertical stress relief was not possible. As a result, the stress reliefs were performed in the horizontal orientation while rotating the rotor periodically 180° during the heating process so as not to set a thermal bow into the rotor.

DFLP Rotor Machining
Based on results of the thermal straightening iterations, machining straightening of both shafts was performed. The work involved final straightening machining of both shaft ends and final dimensional, NDE, and runout checks along the length of the rotor.

The thermal straightening operations reduced the Turb End shaft end TIR from 0.007” at incoming to 0.003” after completion. The Turb End shaft end straightening machining included final machining of the steam gland diameter, all steam gland seal grooves, all transition radii, and the coupling to remove any remaining runout.

The thermal straightening operations reduced the Gen End shaft end TIR from 0.053” at incoming to 0.015” after completion. The Gen End shaft end straightening machining included final machining of the journal, oil deflector, steam gland diameter, all steam gland seal grooves, all transition radii, and the coupling to remove any remaining runout. Also, the coupling holes were line bored to set the bolt circle pattern back on center.

High-Speed Balance
In parallel to the blading and seal strip installation, MD&A produced a new stub shaft in support of performing the high-speed balance.

The balance work involved the installation and aligning of the new stub shaft, installation of the rotor in the high-speed balance facility, balancing the rotor at operating speed, and performing an overspeed test of the rotor.

The rotor work was completed on schedule and returned to the owner.

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.

Have us look at your bowed rotor today. Call our Turbine-Generator Repair Facility at (314) 880-3000 or use our Contact form.

The post DFLP Rotor Straightening and Machining appeared first on MDA Turbines.

The utility weighed several repair options. These included rotor welding, which would have been time-consuming and expensive, and field replacement, which presented an unacceptably long lead time and high cost. A third option—stub shaft repair—proved to be the best choice in terms of cost and downtime for the revenue-generating asset. MD&A designed and performed the repair, which involved severing the rotor outboard of the collector-end journal and then installing a bolted-on stub shaft.

As part of the repair, the generator rotor shaft end was removed and the bolted-on stub shaft was fitted in the journal outboard seal area. To ensure that no hydrogen leak would occur around this flange face, an O-ring groove and O-ring were installed. Also, to ensure that the new stub-shaft bolted connection could support the assembly torque, as well as, the exciter that bolts to the shaft, MD&A prepared calculations using the original shaft end bore, the key holding the shrunk-on coupling, and the shrunk-on coupling bolting to the exciter.

Machining of the rotor shaft end included severing the rotor just outboard of the collector-end journal in the middle of the outboard oil seal diameter. Once severed, the shaft-end face was milled, drilled, and tapped to allow for a bolted flange, an alignment female spigot, and an O-ring seal groove.

Machining the new stub shaft included all reverse-engineered features of the original collector shaft end. The forging was bored to the original shaft bore diameter to include the bore plug fit. The flange face was machined to include 14 thru holes and a male spigot fit-in support of bolting up to the original shaft. The shaft was machined to include all the fit diameters for the collector rings, the fan hub, and the shrunk-on coupling. Four radial holes were drilled for the collector ring radial stud assembly.

After it was final-machined, the stub shaft was dimensionally inspected and subjected to a non-destructive examination by MD&A. Before the rotor was returned to the customer, final quality checks were completed, including visual, dimensional and electrical tests.

MD&A provides comprehensive refurbishment and repair of utility generator stators and fields, including high-voltage bushing refurbishment and complete rewinds.

Have MD&A look at your generator rotor today, call our Turbine-Generator Repair Facility at (314) 880-3000 or use our Contact form.

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MD&A’s Turbine-Generator Repair Facility performed a diaphragm dishing repair to the stage 15 diaphragm by cutting out the old weld, re-positioning, re-welding, stress relief, and final machining. Incoming inspections and evaluations consisted of blast cleaning, NDE, visual inspections, and dimensional checks. The stage 15 drop checks were taken as a baseline for the as-received diaphragm. Based on the opening clearance measurements, it was found that the stage 15 diaphragm was dished downstream by approximately 0.215”.

Due to the unacceptable amount of dishing found on the stage 15 diaphragm, the stage 15 diaphragm was repaired utilizing a welding and post-weld heat-treating process.

The repair process included machining to remove the spacer bands to inner and out ring welds, re-positioning the diaphragm back into the correct axial position, restoring the welds to provide a 100% full penetration weld, and then post-weld heat treatment.

After post-weld heat treatment, the diaphragm halves were disassembled from the jacking and backing plates, blast cleaned, and dimensional checks were performed to verify and ensure the diaphragm halves inner web rings were re-positioned back into the correct axial position.

The dimensional checks confirmed that the diaphragm halves’ inner web rings were positioned back upstream by between 0.240” and 0.260”. Once confirmed, each diaphragm half HJ was set up on a horizontal boring mill to machine and restore the HJ surface as well as the dowel holes and keyways. The diaphragm halves were assembled and the assembled diaphragm was set up on a vertical boring mill to the final turn machine. Once all machining was completed, a final NDE was performed on all welded and machined surfaces. Lastly, the stage 15 diaphragm was assembled to the stage 16 diaphragm.

See our handout: Dished Diaphragm Repair Options

Let MD&A perform your next Diaphragm Dishing Repair today, call our Turbine-Generator Repair Facility at (314) 880-3000, or use our Contact form.

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