The 501F Users Group is a private community of owners and operators of 501F gas turbine/generators established to discuss the operation, maintenance, inspection, troubleshooting, repair, and optimization of their plants and equipment. Membership in the organization is limited to individuals who are directly involved in the construction or O&M of Siemens Energy, Westinghouse, and Mitsubishi Power 501F, 701F, and SGT6-5000F gas turbines and who are employed by companies with a direct ownership and/or operational interest in those engines.

Annual conferences are developed and moderated by the group’s officers and directors (sidebar). Agenda highlights for the F frame’s portion of the 2023 joint meeting are presented immediately below for Tuesday, Wednesday, and Thursday (half day), February 21-23. Highlights of Monday’s program, for both 501F and 501G users, are in the previous section. CCJ’s printing deadline prevented the sharing of more detail in this special edition for the Reno conference. Updated information is available at the meeting registration desk.

501F Users Group Officers and Board of Directors

President and Chairman of the Board
Ivan Kush, principal CT and con­trols engineer, Cogentrix Energy Power Management

Vice Chairman
Carey Frost, program manager, Duke Energy

Secretary and Board Member
Brian Berkstresser, plant manager, Liberty Utilities

Board Members:

Blaine Gartner, principal engineer, Xcel Energy
John Burke, O&M manager, Cottage Grove Power Plant, NAES Corp
Dave Gundry, senior engineer, Xcel Energy
Greg Dolezal, managing director, Klamath Energy LLC (Avangrid Renewables)
Jaime Oliveira, O&M senior man­ager, Norte Fluminense, EdF

Tuesday, February 21:

First half the morning session encompasses a closed user section and generator roundtable with associated presentations by owner/operators. Siemens Energy’s program follows the refreshments break at 10 a.m. and runs until lunch at noon.

PSM is at the podium for the entire afternoon.

Wednesday, February 22:

Inlet and exhaust and compressor roundtables and their associated user presentations run from the opening bell to the break at 10 a.m. The rotor and hot-gas section roundtables complete the morning program.

Mitsubishi Power is at the podium for the entire afternoon.

Thursday, February 23:

Morning-only program features combustor and auxiliaries roundtables before refreshments and the outage roundtable following. Conference concludes at noon.

Useful Conference Links

• 501F and G users meet together—again (includes Monday highlights)
• 501F Users Group program for 2023
• 501G Users Group program for 2023
• 501F 2022 conference recap: User sessions
• 501F 2022 conference recap: Vendor presentations
• Excerpts from recent 501G plant reports
• Abstracts of recent 501G user presentations
• Remembering Steve Bates

A Covid outbreak a week or so before the 2022 meeting was to start at the Hyatt Regency in New Orleans, February 20, dramatically reduced the number of attendees expected, both user and vendor. Recall that this conference was the group’s return to an in-person program following a virtual meeting in 2021.

Since many owner/operators participating in the 2023 conference were not able to attend last year, the editors have compiled some of that meeting’s technical highlights below to help you “connect the dots” since the 2020 in-person conference.

User presentations

Just shy of a dozen presentations by owner/operators were incorporated into the seven 501F roundtables conducted in 2022: Inlet and exhaust, compressor, rotor, hot-gas section, combustors, auxiliaries, and outage planning and conduct. Summaries follow. Get the details by accessing the PowerPoints on the group’s website at https://forum.501Fusers.org.

Find them in the “2022 Conference Materials” forum post. Only registered users are admitted to this portion of the website.

2021 outage highlights for this unique 2 × 1 combined cycle, described in two presentations, include a steam-turbine major, ST valve inspections, second majors and FD3 upgrades for the gas turbines, and generator inspections on the steamer and one of the gas turbines.

Planning for the outage, the largest in the plant’s history, started in 2019. Given the large amount of work slated for 2021, some was moved forward to 2020 to free up crane time, reduce interferences, and level-out the workload of facility personnel.

History: First unit installed on the greenfield site nearly 30 years ago was a 501D5. A 501FC+ was added two years later. Year 2000 saw installation of a 501FD2 and a steam turbine. Upgrade of the FC+ to FD2 and conversion to the combined cycle followed immediately.

Key topics in the first presentation were implementation of (1) purge credit, to eliminate purging during startup and (2) inlet heating, to improve availability and expand the unit’s operating range. P&IDs are provided for both enhancements. Lessons learned provide valuable guidance.

Note that the current purge procedure uses normal spin-down time at the end of a run to count as the purge credit for the next run. (Consult NFPA 85 for details.) It eliminated the air entrainment into the oil system experienced with the method replaced which was said to have damaged the torque converter wheel. Benefits of purge credit include a 10-min decrease in startup time, longer oil life, reduced stresses on the HRSG, etc.

The second presentation discusses changes to the outage plan made necessary by Covid-19 restrictions, reviews schedule and contractor laydown considerations, and profiles, by way of photos, rotor swaps and upgrades to single-piece exhaust cylinders on both gas turbines.

GT major inspections and exhaust replacements presentation is recommended reading by the editors, who are both familiar with the facility profiled and similar work done at other plants. Original scope of work for this 501FD2-powered 2 × 1 combined cycle, planned as a 30-day effort, was the following:

• Major inspection of one gas turbine with rotor exchange and turbine upgrade, plus exhaust refurbishment. Second GT: upgrade only.
• Steam-turbine medium inspection with bearing and valve replacement.
• Pressure-wave cleaning of both HRSGs, plus floor-liner replacement on one.
• Controls upgrade for the entire plant.
• Generator robotic inspections.
• Rebuilds of one cooling-water pump and one boiler-feed pump.

The work described in greatest detail is that for the exhaust section. Inspections conducted as soon as the units had cooled found that Row 4 tip measurements in one engine were significantly different than those recorded only five months earlier. Plus, two of the unit’s six exhaust struts severed during that time.

For those not familiar with exhaust sections, the presentation provides excellent drawings, complete with detailed callouts, explaining the issues and parts involved. In addition, there are summaries of both fleet and plant experiences involving the exhaust section.

Repair options to correct the major deficiencies identified included weld repair and exhaust cylinder and manifold replacement. A new plan was developed: Extend the outage from 30 to 45 days to conduct majors on both gas turbines and replace the exhaust cylinders and manifolds on both machines.

The presentation concludes with a list of additional findings and corrective actions.

DLN to ULN conversion. Upgrades of SCR systems incorporated in this 2 × 1 combined cycle’s HRSGs were not viewed as adequate to meet new rules governing NOx emissions and expected future limits on ammonia slip. Ultra-low NOx was selected as the preferred solution. It was believed capable of reducing NOx from 25 ppm to 9 to 12 ppm. Pictures describe the work in progress.

Here are the results described by the speaker:

• Plant output decreased by about 5 MW.
• Plant heat rate increased by about 290 Btu/kWh.
• Combustor dynamics were virtually zero.
• Plant is meeting its NOx requirements, but struggling with CO.
• Ammonia consumption has been reduced by about half.

One year of experience with FlameTOP. Presentation discusses recent modifications to one of two gas turbines at this 501FD2-powered 2 × 1 combined cycle that are providing the additional power expected (and sometimes more). Here’s a list of the changes:

• Retrofit of FlameSheet™ combustors to boost engine output and increase efficiency.
• Installation of PSM’s GTOP system, with its hardware upgrades to increase output and extend maintenance intervals.
• Addition of inlet bleed heat to the compressor to increase turndown.
• Installation of AutoTune 3.0/PLP for tighter unit control.
• Retrofit of PSM’s exhaust cylinder and manifold.
• Installation of Arnold insulation for the walls, floor, and ceiling of the exhaust transition duct to reduce performance-robbing heat losses.

FlameTOP7 from PSM is said to increase the simple-cycle output of a standard 501FD2 by 20 MW while reducing heat rate by 3.8%. Unit turndown can extend below 40% of the full-load rating with both FlameSheet and inlet bleed heat installed. NOx emissions are less than 9 ppm across the load range.

After flipping through the slide deck, read “Desert Basin reports experience, success with first 501F FlameTOP7” in CCJ No. 66 (2021) for details.

A second plant also reported a GTOP success, this one involving GTOP6 mods to both engines of the 501FD2-powered 2 × 1 combined cycle—including new combustion hardware, 16th-stage compressor blades, first- and second-stage turbine vanes and blades, and other improvements. The benefits: More than 22 MW of additional combined-cycle capacity and a heat-rate reduction of 80 Btu/kWh.

This presentation is valuable for the balance-of-plant (BOP) assessment described, which was part of the process for evaluating the benefits of upgrading the gas turbines. The report for this effort highlighted safety valves and steam silencers as having insufficient capacity. Plus, the steam turbine’s pressure and temperature limits were identified as a potential limitation, along with both the condensate pumps and the boiler-feed pumps. Changes to safety-valve settings were required, too. Other modifications needed post implementation also are discussed.

Multiple gas-turbine events experienced at a 501F4-powered 3 × 1 combined cycle that occurred during a three-month period are described in this presentation. Here’s a description of the events and what was done to correct them:

• Operators noted that one gas-turbine in the eight-year-old combined cycle experienced a step change in vibration (relative and seismic) and an output loss of about 1 MW. About a week later, personnel reported hearing a fast-rattle/buzz type of noise inside the exhaust end of the machine. It was accompanied by a nominal loss in unit output of about 3 MW. The engine was shut down and inspected. Initial findings: damage to Row 3 and 4 turbine blades, vanes, and ring segments. Repairs were made and the unit returned to service.
• A second gas turbine tripped along with a loud bang and high relative and seismic vibrations. Vibration levels across the unit reached trip levels and were at or above 16 mils. Inspection findings included damage to Row 3 and 4 turbine blades, vanes, and ring segments, plus the rotor, exhaust cylinder, lube-oil piping, and inlet manifold. Repairs were made and the unit returned to service.
• A major inspection was initiated on the combined cycle’s third gas turbine about six weeks after a borescope inspection of Row 3 blades and ring segments did not reveal any significant findings. However, first inspection conducted during the major revealed some distorted Row 3 blade shroud platforms and exhaust-cylinder heat erosion. Unit returned to service after a two-month outage.

Details on how cooling flows and exhaust temperatures were measured at load loads to verify model calculations. Input from Siemens Energy based on RCA results also is summarized.

IGV history/maintenance. The presenter walks you through inlet-guide-vane modifications made over the years to prevent sticking by improving bushing lubrication—the first, for the top half of the bushing, ProdMod 98-1410 in 1998. Westinghouse modified the lower half the following year using the procedure described in ProdMod 99-0240. Siemens Service Bulletin 51004 Rev 2 is recommended reading.

IGV seize-up/icing. The same W501FC+ engine with the sticking problem (summary immediately above) experienced freeze-up when moisture accumulated in some of the IGV bushings (lower half in particular) and the ambient temperature dropped to minus-2F. All blades in Row 1 had ice deposits, those in Row 2 had some ice or frost. Operational information related to mitigation efforts is included in the slide deck.

Problem was resolved by installation of a torpedo heater to defrost ice followed by exercising all the bottom-half IGVs. Borescope inspection revealed no damage. A chart provided by the speaker shows first-stage icing potential at several IGV angles. Attendees were referred to Siemens Energy’s TA 2005-015 Rev 1 to learn more about icing and how to avoid it.

Generator main-lead failure experienced by a South American owner/operator covered problem identification, steps to repair, and lessons learned. Background: Four failures occurred: Broken B phase for the KN steam turbine/generator at this 3 × 1 combined cycle was found in December 2008 and occurred again three months later. Since that time, all main leads have been x-rayed during every turbine outage.

The NDE effort paid off: Phase A in one of the W501FD2 gas turbine/generators was found broken in November 2011 (at more than 900 equivalent starts and 38,000 equivalent baseload hours). T1 failed at the brazed joint below the main lead flange connection to the bushing; x-rays showed cracks in T2, T3, T5, and T6 in locations similar to T1. A second failure occurred in this gas turbine in April 2021 at 1327 ES and 113,453 EBH.

Photos of the first and second GT failures are provided in the presentation together with an overview of repairs, inspections, and tests conducted. Best-effort cleaning also is described.

RCA of a 16-kV flashover. This case history pertains to a unit in reserve shutdown. Incident overview: The GSU and isophase bus (IPB) to the generator circuit breaker (GCB) were energized at 16 kV. A flashover event occurred in the C phase of the breaker on a high-side potential transformer. Inspection revealed water/condensation only in C phase.

Heaters in the IPB were working, but the breaker that feeds heaters inside of the GCB had tripped. Subsequent removal of isophase links at the auxiliary transformer for hi-pot testing revealed water inside of the adapter between the isophase and transformer. Cracks were found in the weld that secures the adapter to the top of the transformer. Photos are provided.

Corrective actions:

• Cleaned and sealed the weld with silicone and spray sealant and began investigating a long-term solution—including possible weld repair.
• Added GCB heater breaker status to plant rounds.
• Planned the addition of humidity sensors and thermometer in the GCB and the transmission of data back to the control system for alarming purposes.

Useful Conference Links

• 501F and G users meet together—again (includes Monday highlights)
• 501F Users Group program for 2023
• 501G Users Group program for 2023
• 501F 2022 conference recap: User sessions
• 501F 2022 conference recap: Vendor presentations
• Excerpts from recent 501G plant reports
• Abstracts of recent 501G user presentations
• Remembering Steve Bates

The 501G Users Group is a small organization of well-connected engineers and technicians who have “grown up” together—so to speak—and very familiar with their colleagues’ plants and equipment. The first Siemens/Westinghouse 501G, installed by Lakeland Electric, began commissioning operations in April 1999, but COD wasn’t until March 2001—only one month before the second machine began commercial operation at Millennium.

Steering committee

Chair (acting): Mark Winne, plant manager, Millennium Power Partners

Scott Wiley, outage manager, Vistra Corp

Guy Taylor, plant engineer, Lakeland Electric

John Wolff, technical support/compliance manager, Ironwood, LS Power

Fleet size is small by industry standards—24 engines at 13 sites in the US and one in Mexico (sidebar). Four plants are equipped with one engine each; seven have two gas turbines; two are equipped with three machines each, arranged in 1 × 1 combined cycles.

User meetings typically host one-third to one-half first-timers, so many discussions are similar from year to year because newcomers have to be brought up to speed. But there’s not much turnover in the top positions at G facilities which means each meeting pretty much picks up where the last one left off. This contributes to presentation efficiency because there’s a minimum amount of repetition.

Most user groups serving GT owner/operators organize their technical programs by sections of the engine—for example, compressor combustion section, turbine, etc. By contrast, the G users generally begin with an “annual report” from each plant and follow that nominal half-day program with user presentations on emerging and significant plantwide issues of importance to the fleet.

Excerpts from plant reports and abstracts of selected presentations made during the pandemic and not previously presented in CCJ follow the summary agenda for the 2023 conference, immediately below, which is based on information made available to the editors on January 17. An updated conference program is available at the conference registration desk.

W501G fleet: 13 plants, two-dozen units

Ackerman Combined Cycle Plant, TVA, Ackerman, Miss

Athens Generating Plant, operated by NAES Corp, Athens, NY

Ennis Power Plant, Vistra Corp, Ennis, Tex

Fuerza y Energia Naco Nogales SA de CV (FENN), Gas Natural Fenosa México, Agua Prieta Sonora, México

Granite Ridge Energy Center, Calpine Corp, Londonderry, NH

Harquahala Generating Facility, operated by NAES Corp, Tonopah, Ariz

Hillabee Generating Station, Constellation Energy Corp, Alexander City, Ala

Ironwood, operated by EthosEnergy Group, Lebanon, Pa

Magic Valley Generating Station, Calpine Corp, Edinburg, Tex

Magnet Cove Generating Station, Arkansas Electric Cooperative Corp, Malvern, Ark

C D McIntosh Jr Power Plant, Lakeland Electric, Lakeland, Fla

Millennium Power Partners, operated by NAES Corp, Charlton, Mass

Wise County Power Plant, Vistra Corp, Poolville, Tex

501 G Users Group agenda highlights

Tuesday, February 21:

• Morning session (first half) features a highly interactive workshop on Human Performance, complete with (1) an explanatory presentation by an experienced user, (2) learning teams, and (3) tips on how to avoid the Blame Game.
• Presentations and discussion on retubing of rotor air coolers (RAC) and the fuel-gas heater complete the morning program. User experiences and challenges are shared by attendees.
• Siemens presents after lunch. A technology review of the inlet and compressor sections, plus a general discussion on debris contributors and management, get the afternoon program rolling. A technology review of the combustor, turbine, and exhaust sections follows, with updates on NextGen and Row 1 vanes completing the day.

Wednesday, February 22:

• Morning session (first half) reviews fleet statistics and key issues, which are incorporated into the plant reports presented by representatives of all facilities participating.
• User presentations on HP bypass replacement and OST valve replacement close out the morning program.
• Afternoon session includes two interactive roundtables:

1. Generators, focusing on:

• Major maintenance.
• Risk/reward and how it may change based on a variety of factors.
• Major spares, rewind kits, and contingency planning.

2. O&M considerations for fuel-gas heaters:

• Identifying fuel-gas leaks and operating with them.
• Alarms versus trips—prudent engineering guidance.
• Bundle replacement options.

Thursday, February 23:

• Two user presentations before the morning refreshment break address Row 3 turbine-blade ring deflection and AVR upgrades.
• One user presentation is scheduled after the break but the topic was not available at press time.

Useful Conference Links

• 501F and G users meet together—again (includes Monday highlights)
• 501F Users Group program for 2023
• 501G Users Group program for 2023
• 501F 2022 conference recap: User sessions
• 501F 2022 conference recap: Vendor presentations
• Excerpts from recent 501G plant reports
• Abstracts of recent 501G user presentations
• Remembering Steve Bates

• Challenges getting into the market because of high gas prices.
• Two big outage events: Row 1 blade failure and generator lead failure, the latter attributed to misalignment of the lead from the generator to the isophase bus.
• L-1 steam-turbine blade failure (generator drive end) damaged the L-0 row and tubes in the condenser impingement zone. Analysis revealed stress corrosion cracking as the cause. Opened the HP/IP turbine while the LP blades were being replaced and found some problems there as well. The distribution grid, located just ahead of the reheater in one of the HRSGs, also failed, damaging some tubes. Temporary repairs made; permanent repairs deferred a couple of months to accommodate the addition of necessary structural support.
• At a 2 × 1 plant with about 50k hours of operation on the GTs and steamer, and 1000 starts on each gas turbine and about 650 on the steamer, addressed an exhaust-casing split-line leak on one GT. Recommended fix was casing-bolt replacement at 110% of the recommended torque. Trunnion vibration issues on a 501G were solved by regreasing. Plant’s greasing process then was updated to reflect lessons learned. Similar problem on another unit in the fleet was corrected by replacing the grease fittings. The originals were worn out and grease was not getting to where it was needed. Yet another user, similarly affected, reported that his plant’s solution was to jack up the unit and remove old hard grease.
• Combined cycle with just over 100k hours on both GTs and the steamer reported that the NextGen upgrade done a couple of years ago to permit operation at lower loads continues to perform well. However, CO is still elevated (two- or three-fold higher) during starts compared to DLN hardware. On the plus side, output increased and NOx emissions were about 20% lower than DLN.
• Flashback thermocouple failures were problematic at this plant and all t/cs were replaced on both gas turbines. Issue wasn’t resolved until Siemens redesigned the thermocouples.
• Key issues reported by a user involved turbine through bolts, Row 1 blade/vane events, L-0 blades. LP economizer was replaced because of degradation caused by ammonia salts, which were attributed to early operating problems caused by tube leaks.
• Catastrophic failure of a steam turbine was described by an attendee who said the unit was rebuilt over a 250-day outage and back in operation at the time of the meeting. No one was hurt. Damage included shaft failure, generator and many condenser tubes destroyed, and HRSG casing hammered by liberated bearing parts.
• Another plant reported positive results from a gas-turbine NextGen upgrade. Hardware is cleared to run 12,000 hours to HGP, but borescope inspections will continue—to track degradation. T3000 was upgraded, too, and the control system is performing well. Participants were reminded that if they upgrade their controls, set points must be reinstalled. A small hydrogen leak also was mentioned but it is actively monitored and not considered a problem.
• OST valves are believed associated with the rotor air cooler (RAC) not operating properly. Seats can stick and valve not open as intended during startup. Plant has identified a vendor that may be able to provide an alternative with a replaceable seat.
• Plant reported an issue with its Nash vacuum pumps. Steam jet ejectors believed too small for the duty so Nash pumps must run all the time and can overheat. Last time a condenser leak check was performed, the steam jets and one Nash pump were required to hold vacuum. A couple of other participants recommended doing a helium leak check and paying special attention to the integrity of the crossover pipe.
• A 2 × 1 combined cycle was operating in true peaking mode because of low gas prices. A rotor swap on one of the gas turbines forced operation in the 1 × 1 mode.
• Major on a KN steam turbine involved machining out and replacing stellite seats on valves. During the overhaul, investigation of actuator oil leaks revealed the wrong plugs had been inserted previously. Bearing oil leakage was high because a worn seal ring had not been replaced during the last overhaul. Plant struggled with vacuum leaks in the last year which were attributed to rupture discs being near end-of-life.
• Plant reported high ammonia slip, corrected temporarily by cleanout of the ammonia injection grid (AIG). Replacement and upgrade alternatives are being considered. An attendee offered that the Peerless Edge® AIG retrofit it implemented operates with ammonia slip and NOx within specifications. Prior to the retrofit, plant reduced load to control slip.
• A vibration step change on one of plant’s two gas turbines was investigated with borescope inspection finding Row 4 hardware missing and several Row 1 vanes breached. Operator training was being considered.
• Leaking tubes in the fleet leader’s kettle boiler were simply plugged to enable continuing operations.
• Wear and tear on this 1 × 1 plant’s HRSG prompted use of thermography to identify hot spots, resulting in a partial rebuild of the boiler’s walls. The floor also was rebuilt to eliminate release of insulation. Finally, ports were added on top of the HRSG for NOx traverse testing.
• Another plant reported rebabbiting and repair of its exhaust bearing, plus replacement of Row 1 ring segments, one combustion basket, and one transition piece.
• One gas turbine at a 2 × 1 plant with more than 100k hours of service completed a rotor exchange and replaced four Row 1 blades and three Row 1 vanes during that major. Its sister unit also conducted vane and blade work during the overhaul, including a few airfoil replacements.
• The representative of a 3 × 1 combined cycle discussed a DCS upgrade to T3000 Version 8.2 on the trio of gas turbines, which averaged about 70k operating hours and 2000 starts. The steam turbine, with about 100,000 hours under its belt, and one GT benefitted from AVR (automatic voltage regulation) upgrades.
• One gas turbine at a 2 × 1 facility experienced an expansion-joint failure, resulting in a unit trip. Other happenings: A significant forced outage was caused by the failure of a startup frequency controller. One unit suffered flashbacks on Can 3 following a low-gas-pressure event.
• Plus, pieces of lockwire wire were found in combustion cans during a borescope inspection and removed; there were multiple igniter failures (some sticking after insertion); Row 1 STM (short-term mitigation) vanes were installed on both units to address the vane-distress phenomenon reported in the fleet. Regarding the last point, the modified vanes increase backflow margin, improve impingement cooling, and supply additional film cooling to the leading-edge of concern.
• Major inspections were conducted on both the steam and gas turbines at a 1 × 1 facility with about 100k service hours. However, within one month of outage completion, five of six RTDs monitoring the generator had failed; ST vibrations were high during post-outage starts, increasing regularly from 8 to 14 mils; throttle and governor valves on the steamer began sticking during starts; and the reheat stop valve was sticking—sometimes.
• Borescope inspections on two gas turbines, each with nearly 100k hours of service and 1800 starts, revealed no issues with Row 1 mitigation vanes. Center igniters were installed on one unit; however, cables were not connected properly, causing a fired abort on startup. Second GT experienced a full-load trip attributed to a flameout caused by initiation of steam power augmentation. Logic mod fixed that problem.
• A 1 × 1 plant with more than 100k service hours and 2700 starts identified flow-accelerated corrosion (FAC) in the HP economizer upper headers and LP economizer. Planning for replacements during the next outage is underway. Other issues of concern included turbine through bolts, Row 1 blades and vanes, increase intervals for blade inspections (8k to 12k hours). Plant experienced its first through-bolt failure at 20k hours, second at 30k; current set of bolts has been in service about 40k hours.

Useful Conference Links

• 501F and G users meet together—again (includes Monday highlights)
• 501F Users Group program for 2023
• 501G Users Group program for 2023
• 501F 2022 conference recap: User sessions
• 501F 2022 conference recap: Vendor presentations
• Excerpts from recent 501G plant reports
• Abstracts of recent 501G user presentations
• Remembering Steve Bates

Takeaways from safety roundtables:

• Populate your plant safety committee with motivated personnel and use corporate guidelines to ensure job safety.
• Excavations frequently are required at relatively new sites for fixing underground infrastructure. Proper barriers for personnel protection are particularly important. Know where to dig, how to dig, and how to refill to prevent collapse.
• Conduct a 10- to 15-min safety meeting before start of work and at end of day. In the morning, review what could happen given the planned activities; in the afternoon, what did happen. Make discussion topics germane to the work scheduled for the next couple of days.
• Attendees expressed concern about different procedures at different plants, particularly when changes in ownership occur. Procedures are not one-size-fits-all and unless carefully thought through can take control out of the hands of those who know the most.
• Maintain a no-blame culture. If something doesn’t seem right, ask questions. After an incident, all plant supervisors and personnel should ask themselves, “What could I have done to prevent the problem from occurring?”
• Virtually every plant acknowledges that it has a “good” safety program, according to a poll of attendees. But the challenge is to make it better. Remember that complete paperwork doesn’t mean the work is being done safely.
• Contract safety personnel on patrol is money well spent. These folks typically are good at “coaching,” not criticizing.
• Consider implementing a “good catch” program to keep concerns in front of the group until they are corrected.
• Annual air-quality-management and respirator training are recommended for all plant personnel.

Bearing problem? Nah, it was a lube-oil temperature problem.

The details: Collector bearing vibrations on one gas turbine suddenly increased to more than 6 mils. Bearing area was inspected; there were no obvious findings. Vibrations reappeared daily soon after GT restart. Corporate engineering was consulted. Vibrations reached a high of 7.7 mils, but with a trip setting of 8.5 there were concerns.

Was collector compartment temperature a cause? A portable a/c unit was installed, but the problem remained. Was something in the generator causing the problem? Nothing obvious based on a thorough inspection.

One day vibration was not a problem: Weather was cool and wet—an “ah-ha” moment. Put two lube-oil coolers in parallel to reduce oil temperature and the problem disappeared.

Staff found cooling-water temperature was higher than normal because of several failed spray nozzles in the tower; also, the collector bearing was lightly loaded. Nozzles replaced and bearing loading corrected, the unit returned to normal operation with one lube-oil cooler in service.

A two-decade operating history of high HRSG backpressure (BP) and derates for a 1 × 1 combined cycle provided valuable lessons learned. The plant, designed for baseload operation, was commissioned and soon pressed into cycling service for several years. Almost from the get-go, the HRSG experienced fouling by ammonia salts from the SCR and rust accumulation, most evident in the last tube sections. Result: A gas-turbine derate of 15 MW.

After years of monitoring pressures, trying online cleaning methods (sonic horns, vibrators on lower headers) and offline cleaning (dry ice, air jets, pressure wave), and dehumidifiers on the GT inlet and LP inlet to the HRSG, plant, beginning in 2008, resorted to adding stiffeners in the HRSG. Lower baffle plates were removed in the LP and IP sections and several different baffle configurations were tried to identify the most effective alternative. Also, SCR controls, and economizer recirculation temperature controls, were adjusted to increase the allowable BP from 28 to 30 in. H2O.

In the face of continued elevated BP in 2016, the facility pursued permanent modifications beginning in 2017 (through 2020) to increase allowable backpressure to 45 in. H2O and address other issues—such as tube leaks.

These included doubling the number of stiffening plates in the roof, floor, and walls; replacing the LP economizer, LP superheater No. 1, and LP evaporator tube bundles; and upgrading the expansion joints. Eleven tube rows in the LP economizer were replaced with 15 smaller-diameter tubes, creating a 20 in. cleaning lane between the LP economizer and the LP evaporator/superheater No. 1.

Pressure wave was by far the most effective cleaning method, being able to remove about five times as much debris as dry ice. The story may not be over, though. The unit has not been cleaned since 2020 and BP is beginning to rise again—even though the unit is now operating baseload.

Transition-piece steam pipe failure. During a local crawl-through inspection, plant personnel found a tube liberated from one transition piece. A full unit check found cracks in two more transition pipes in roughly the same place. Dye-pen inspections of the remaining TPs found no additional problems. Other users in attendance reported similar cracking.

RCA conclusion was that the dynamic frequency of the engine was close to the natural frequency of the transition piping. The OEM recommended increasing the exhaust temperature to create greater separation from the natural frequency of the transition piping. A logic change was made and no problems have been reported since.

Case study of a condenser event may well be one of the most valuable safety briefs you’ll receive if you have a combined-cycle plant with a fuel gas heater (FGH). An abridged account follows.

As a result of the failure of a main lead in the steam turbine/generator, the facility was in a steam-turbine outage in January 2022 during which the GTs remained “available” to the grid (with fuel at pressure up to the FGH stop valves). With the plant experiencing numerous issues with the FGH (for example, leaking gas isolation valves) and its leak-detection system (prone to false alarms), and other factors, natural gas found its way to the condenser via the IP water-side supply line (the source of heat for the FGH).

The plant was down for 10 days, but with cold weather in the forecast, the gas turbines were started to build up pressure to about 50 psig in the HRSG to prevent freezing. The steam pressure in the HRSG provided the motive force to move the gas that had been accumulating in the IP drum to flow down the steam piping to the condenser.

When a welder arrived to repair a 1-in. pipe connection on the outside of the condenser, the arc ignited the gas and the subsequent explosion blew out six rupture discs on top of the unit, caused bolting threads on the LP steam-turbine cover to fail, and damaged internal structural supports. Rupture-disc parts were found all over the plant site. The explosion was heard and felt throughout the plant.

No one was injured (not even the welder), no condenser tube leaks occurred, and the LP section of the turbine suffered no internal damage.

Recommendations to avoid a similar incident elsewhere, included the following:

• Eddy current test FGH tube bundles and perform leak testing at least every six years.
• Utilize more robust inserts when plugging tubes.
• Ease plant staff access to vent valving and instrumentation.
• Establish fleet standard critical preventive maintenance guidelines for FGH systems.
• Perform comprehensive FGH system design review.
• Install permanent redundant methane detectors on air ejectors with feedback to control system.

Plant has no vacuum pumps so steam pressure is required on a unit start to raise vacuum. Staff found the time required for a unit start creeping up and budgeted time for checking piping, drains, valves, etc, to find out where the leak was. One day it was not possible to get the vacuum low enough to roll the steamer. More leak checking required.

The gremlin was in the crossover pipe from the IP section to the LP. OEM’s plan was to remove the 60-in.-diam pipe and re-gasket both ends. Outage time required: Six days.

Alternative plan proposed by Furmanite America: Install scaffolding, remove insulation, remove crossover-pipe bolts and clean threads, lubricate threads, and reinstall. Plus, the steam-turbine/generator enclosure was modified to allow steam/hot air to escape and cool down that area, which got hotter as the unit ran. Bolts were so loose all the way around the pipe flanges, nuts could be removed by hand. Staff believes the bolts worked loose because of unit cycling.

The bottom line: Tough working environment, but the job was completed in two days at less than 20% of the OEM’s quote—including drilling required for Furmanite injection (and the Furmanite) and reinstallation of insulation.

Recommended PM: Check all bolts periodically, especially following a change in operating regimen. If you find two bolts loose on one flange, change the gasket as well as all the bolts. Same goes for flanges on GT bleed piping and air extraction lines.

Generator lead failure caused unit to trip from 42% load. All auxiliary power was lost; unit coasted down on dc lube and seal oil; generator hydrogen loss was significant; electrical testing revealed winding was grounded in all three phases. Significant damage—including melted copper and other debris—was found in the lead box.

Main lead T2 cleat was blown out during the event with carbon dust and debris (molten metal) falling into the generator. Carbon dust was distributed all over the generator by the hydrogen blower. Rotor was pulled for cleaning and full rewind.

The presenter said upgraded main leads, reflecting the realities of today’s operating paradigms, were installed. He recommended others consider doing the same on the advice of experts. It was his opinion that the original brazed joint failed because of years of cycling service.

This forced outage ran six months and cost $15 million. Ownership change and other upset conditions stopped work four times during the outage, which should have taken but 45 days. Speaker said it should take 14 24-hr days to change leads.

D11 bearing damage. MAD 11 bearing temperature on the steamer was running about 12 deg F higher than it had on the previous run. Unit was taken out of service and when coasting down experienced a lockout. It went to 0 rpm within 10 minutes and couldn’t go on turning gear. Bearing damage was suspected.

Unit was opened to access the aft bearing—a big job. Bearing was found wiped; drain holes were blocked so there was no lift oil. Bearing collar also was damaged and required a shop repair effort. MAD 12, a combined thrust/journal bearing, was checked as well. Varnish fouling was identified. Some of the thrust pads were damaged and replaced. Plus, the turning-gear overrunning clutch was damaged and repaired.

Analysis identified poor oil quality as a contributor to the problem. Oil from the sump was cleaned from 20/18/14 to 18/15/11. All bearings were inspected for damage and the pedestals checked for contamination and cleaned as necessary. Filters were replaced and all bearing lifts were reset after a high-velocity oil flush. Finally, all dead legs in the lube-oil piping system were eliminated.

NextGen CO emissions. Speaker’s experience was reflected in his “warning” to attendees that they should expect higher CO emissions on a cold start after implementing NextGen. He showed different rates of CO emissions during cold, warm, and hot starts and load changes. A slide showing old DLN emissions versus NextGen showed CO with NextGen was higher from 10 to 30 minutes after startup. By the 30-min hold point during a cold start the plant had consumed 40% of its CO allowance.

Experience with a kettle-boiler expansion-joint failure came next. With no replacement readily available a two-piece clamp was designed, installed, and filled with Furmanite. Staff had some concerns initially that this might restrict tube expansion in the boiler, but after five or six starts with the homemade fix everything seemed fine.

Useful Conference Links

• 501F and G users meet together—again (includes Monday highlights)
• 501F Users Group program for 2023
• 501G Users Group program for 2023
• 501F 2022 conference recap: User sessions
• 501F 2022 conference recap: Vendor presentations
• Excerpts from recent 501G plant reports
• Abstracts of recent 501G user presentations
• Remembering Steve Bates

If you didn’t know Steve Bates, who died suddenly November 30 (2022), at age 57, while on vacation with family, be assured it was a privilege. The plant manager of Vistra Corp’s Wise County 2 × 1 G-class combined cycle in Poolville, Tex, and chairman of the 501G Users Group, Steve was a technically competent, respectful, and unflappable leader who never passed on an opportunity to help a colleague.

He was a big supporter of CCJ’s mission and an industry luminary who viewed personnel safety as a top priority long before many others. Example: Most recently, and with his company’s support, Steve alerted powerplant owner/operators to the potential for leakage by fuel-gas-heater stop valves and the possibility of an explosive mixture of fuel and air forming in the condenser.

He presented on this possibility at every opportunity—including meetings of the Combined Cycle Users Group, HRSG Forum, and other industry organizations.

In a world that’s prone to short-circuit discussions of findings in accident investigations, Steve was committed to sharing such knowledge to protect powerplant personnel and the public at large; no corners were cut on his watch. Interestingly, he did everything by the book and it didn’t take longer than not.

Some of the people who knew Steve best share their thoughts below.

Steve was such a nice guy. When I heard the coroner revealed that Steve had a large heart, I laughed—as it wasn’t surprising. Everyone knew Steve had a large heart. You knew it from every interaction you had with him. Steve cared! He cared a lot!

Steve cared about me and my family, he cared about my plant and my team, and he cared about my turbine. He cared about all of our turbines! For more than 10 years Steve selflessly led the 501G Users Group, painstakingly tracking and working diligently to manage a multitude of issues to resolution. Steve was a great listener and worked hard to ensure our voices were heard and our issues were brought forward.

It was a joy to watch Steve wrestle with Siemens. His intimate knowledge and understanding of the 501G, his tenacious grasp of current issues, along with his calm demeanor and good humor made him a formidable foe in any debate or discussion. Steve would hang on to an issue like a pit bull, unwilling to let go until Siemens understood and acknowledged his viewpoint. The drama of watching/waiting for his opponent to capitulate was always entertaining. Steve fought for all of us, because he cared, he cared a lot.

After a tumultuous start to 2022 [the Texas deep freeze], Steve turned his focus to Human Performance and the influence it can have both in our success and in the adversity we face. By allowing the 501G users access and insight into a significant event at his plant, and specifically how human interaction influenced several contributing causes, he gave us an understanding of why it is important that we improve our understanding of Human Performance and strive to integrate human-performance tools and processes into our daily lives.

Again, Steve did this because he cared. He cared a lot. His caring and support will be profoundly missed.

Mark Winne

I am privileged to have worked for Steve for over 14 years. He was a great mentor and friend. Steve showed me the ropes and gave me the tools to be a successful manager. He had a wonderful personality and was deeply engaged with every team member at the plant. Steve’s dedication, knowledge, kindness, and loyalty to the team was key in developing a great culture and family atmosphere at Wise County.

I loved being able to walk in Steve’s office, sit down, and brainstorm ideas to improve plant performance, or even to just share thoughts on recent events. Everyone at the plant has a deep void with the loss of Steve and we will never forget all that he brought to each of our lives. He will be forever in our hearts.

Michael Coffman

I met Steve many years ago through the 501G Users Group. As Chairman for more than 10 years, Steve was very approachable and inviting for anyone to participate. He provided strong leadership for our group with his industry knowledge, and his ability to establish great relationships with all 501G frame owners, vendors, and Siemens. Steve was an open book, always willing to share for anyone who wanted to learn more. He was professional and had a great moral compass. I did not work with Steve as closely as those who interfaced with him on a daily basis; however, he has left quite an impression on me. Steve will be greatly missed.

                                                                                                            Kevin B Robinson

Whether on a fishing boat or in the corporate boardroom, you knew that friendly smile and outgoing personality were always going to be there to greet you. I met Steven Bates while working as a contractor in Arkansas. He was managing the Tractabel facility just outside of Malvern and had a small job for us to do that turned into a very big job and eventually me going to work for him full time—an invitation I always will be grateful for.

Steven was a study of many things and always on top of recent activities, not only in the power business, but anything that piqued his interest. Steven’s leadership with the 501G Users Group is one of the reasons why the G frame has been so successful. He always brought the skills of team-building and inclusion to the table, and doing so with the Siemens team, made our user group’s effort a great environment as well as very productive. We were able to work together to solve many problems in this frame as it was being developed.

Steven was a tri-citizen of the world. Born in England, he moved to Canada and then to the United States; he had citizenship in all three countries. I was working with Steven as he studied for his US citizenship test, learning a few things myself in that process. He and wife Lynn worked hard, passed the test, and were awarded citizenship. Flags of the three countries draped the table displaying the urn with Steven’s ashes (photo).

But above all, Steven’s relationship with his god, wife, children, and grandchildren were always something to aspire to, and as in many other things, Steven led by example in all of these areas. Our industry will miss Steven Bates; I will miss him for his friendship and camaraderie.

Neal Coffey

Having known Steve for the past dozen or so years and working directly with him on the 501G Users Group steering committee for the last decade, words cannot describe the personal and professional loss that we are all feeling. Steve was always willing to help and share his knowledge and experience with anyone needing it. As the committee chair, he worked tirelessly to promote a culture of respect, openness, and integrity among users, vendors, and OEMs.

Although Steve will be missed by all, his legacy will live on through the memories, accomplishments, and friendships made throughout the years. I will personally miss his friendship and camaraderie, in addition to all of the other outstanding character traits that made him the person he was.

John R Wolff

Steve Bates was an exceptional person who will be dearly missed by the Vistra family and the 501G Users Group. He became chairman of the 501G steering committee in 2011 and has provided years of dedicated service. Steve’s leadership on the committee was what drove the 501G users to become a very close-knit family that was well informed of all the issues we were dealing with on the G frame. When I think of Steve, I see a family man, a leader, a communicator, a friend, and a mentor that I will miss.

Scott Wiley

Many years ago, while attending my first 501F and 501G Users Group conferences, I noticed a few guys sitting off to the side of the podium and, based on their looks and my read on their demeanor, I was quickly wondering what I had gotten myself into. One of them was someone I worked with, Pete Sobieski, but the vibes the other two gave off was scary. Turns out they were Mark Winne and Steve Bates, and oh how wrong my read was.

Fast forward almost two decades and I dare say I was barely tapping into the deep well that was Steve Bates. While the last few years have been filled with uncertainty, loss, and changes to the status quo, I consider myself privileged to have grown closer to Steve and wife Lynn during that time.

I feel very fortunate to have vivid memories of what turned out to be our last in-person evening together at Dezerland. Steve, Lynn, myself, and a few others were enjoying some beverages and desert and Steve was laughing harder than I had ever seen. Turns out he found the idea of me on a little Vespa hilarious. That was a wonderful evening and I will always have that memory of him happy and jovial.

Over the last year, the 501G Users Group, which Steve was chairing, got very involved in working with us on the upcoming conference and in that light Steve had just finished working with a Human Performance organization and you could tell it had really kindled a flame for him. He was so excited he brought it to the Boards of both user groups and we decided to include it in the upcoming conference.

Steve was a man of commitment, honor, and grace. His passion for what we do, and how we do it, was awesome to see after such a distinguished career, when some folks are just riding the wave. Steve was full-steam-ahead and just as passionate before his vacation as he was when I met him all those many years ago.

I will miss his unassuming nature, the roles that he filled so well, and the counsel he offered. More importantly, I will miss the person that he was. The author, A A Milne (Winnie the Pooh) summed up so much in the following sentence: “How lucky am I to have something that makes saying goodbye so hard.” I offer, in closing, that all of us who knew and worked with Steve were indeed lucky.

Ivan Kush

I still don’t know what to say. When I heard the news, the first thing I thought was that we still owed Steve a lube-oil pump that we had borrowed.

When we were at the 501G Users Group meeting in Orlando this past May, I ended up in the hospital. Steve called and wanted to come spend time with me so I wouldn’t be alone. He then reached out to ensure I made it home, and reached out again a few days later to see how I was doing.

Steve was one of the most genuine people I have ever met. He had a very calming way about him and no matter what subject I called to discuss, I always came away with a completely different perspective. Knowing and working with Steve has made me a much better person, and I will forever miss him.

Steve Cole

Steve Bates was my friend and a role model for more than 10 years. Steve’s passing it hit me really hard because only a few hours earlier I was commenting on his Facebook post about spending holiday time in Hawaii.

As plant manager, Steve was at all times very knowledgeable, calm, and relaxed. He always had a smile on his face—even during the toughest negotiations. I visited him at Wise County annually and spent quality time with Steve at the many turbine conferences we both attended. He was highly respected in the industry, inspiring, and a caring person who always put family and friends first.

Pierre Ansmann

Leading a user group is no small task: There are many aspects of that role most don’t see. Being a good leader takes a lot of knowledge, pro­fessionalism, interpersonal skills, and tact. Steve Bates was a great leader and helped build a solid framework for cooperation and engagement that helped solve many concerns for the W501G fleet that has benefited both the users and Siemens Energy.

I had the privilege of working with Steve and truly believe we would not have been as successful without his involvement. When we first met, the fleet really needed attention and a dif­ferent approach to tackle some of the tough challenges present in the fleet. He helped pioneer a new way of work­ing with Siemens Energy, and while holding us accountable, was fair in his approach and used his collaboration skills to bring both sides together for the benefit of the fleet.

His engagement allowed us to amplify our interface with better ways to communicate and resolve some of the toughest issues facing the frame. For a period of time, we executed four face-to-face customer meetings annu­ally—including “deep dive” technical meetings as well as monthly net meet­ings to help everyone stay on top of the rapid pace of development of solutions.

Steve helped bring the customers together and was instrumental in creating an atmosphere of cooperation and inclusion that was key to solving some of the most difficult tasks. He was firm and truthful, but also open­minded and accepting of others’ inputs and ideas. This leadership made him stand out in the crowd and brought us all together. We are all better today because of the way Steve facilitated positive engagement while building solid working partnerships and friend­ships. God bless Steve Bates.

Mark Carter, SGT6-6000G product manager