Tip grinding may not cure R1 blade-tip distress on 7FA compressors
Tip rubs generally are considered the most common cause of R1 blade-tip distress in 7FA compressors. Such distress can lead to radial tip cracks (leading and trailing edge) and tip liberations with significant collateral damage to forward and aft compressor stages. This is not news, as a review of TIL 1509-R3 indicates. But what is news, Mike Hoogsteden, field service manager for engine inspection experts Advanced Turbine Support LLC, told the editors, is that cracks are appearing more frequently than in the past.
Ten inspections last summer revealed cracks in three 7FA 7241s, Hoogsteden said. He is not sure that the tip grinding “fix” supported by the OEM is the answer. The tip grinding profile illustrated in Fig 1, he pointed out, is not as “clean” as you might expect and the results of the dye-penetrant inspection in Fig 2 reveal a crack in the circular indication (invisible during conventional visual inspection). The ATS service manager attributes the increased frequency of cracking to more aggressive operation than GTs generally experienced in the past.
Hoogsteden next pointed to the 1509 recommendation that after repairs, blades should be inspected at 25, 50, and 100 actual starts. He believes that users often don’t understand the intent of the recommendation and offered this explanation: If you identify a flaw during your 50-start inspection, after repairs are complete your next inspection is following 25 starts, not 50 as many believe. In effect, the inspection cycle starts again after any repairs are made.
Hoogsteden said that turbine owner/operators had gotten used to doing borescope inspections once or twice annually. But, he suggested that inspection frequency increase because engines are running longer and harder than they had been operating previously. Maintenance issues are not only associated with the 7FA, Hoogsteden noted. Issues with 501F transition pieces, he continued, are occurring more frequently as well.
Believe it or not: Steam drain lines can overheat
A steam-turbine OEM released a safety bulletin last summer warning of possible localized overheating of drain piping and valves. Pictures incorporated into the bulletin showed a ruptured steam drain and a glowing (cherry red) isolation valve. Consensus view of several knowledgeable engineers: The condition described was not specific to any given OEM and that it possibly could occur as well in steam drains other than those on the turbine. However, no users the editors spoke with about the phenomenon had first-hand knowledge.
Overheating events acknowledged in the bulletin had occurred on four of the OEM’s steam turbines, both during commissioning and turbine startup. During commissioning, the drain-leg piping and open manual isolation valve, located just upstream from the closed motor-operated drain valve, were much hotter than the steam. An overheating event experienced during turbine startup occurred in a combined cycle when one of the two stop/control valves did not open during loading of the steam turbine and a section of drain piping was damaged.
Indicators of possible overheating include cherry-red pipes and valves, deteriorated or burned pipe insulation, and thermocouples reporting temperatures significantly above that of the steam. The bulletin noted that the condition may be mitigated by cracking open the motor-operated drain valve downstream of the isolation valve to establish a small amount of steam flow through the drain line.
- The phenomenon had occurred previously (at least one occasion) when a piece of slag became trapped in a tee section of dead-legged pipe. The vortices caused by the tee caused the slag to spin continuously until the pipe got red hot in that region. Public discussion among owner/operators and others revealed the following:
- A user suggested that an acoustic resonance, or a vortex, that traps energy in the dead leg might be the cause. This person said he had seen the phenomenon modeled in a lab, but not in practice.
- An expert on heat-recovery steam generators reported having seen drain lines inside the boiler casing hotter than the bulk steam temperature because of additional heat contributed by exhaust gas bypassing the superheater. This can be avoided, he said, by passing a controlled amount of steam through the drain lines.
- Another engineer likened the damage mechanism to FAC, except that the velocity of the oxides or debris in the pipe swirls around so fast it creates friction.
Calpine has a good year, to buy back more shares
Most CCJ readers have little interest in financial statements published by power generators, but Calpine Corp’s annual reports offer much more than numbers. CEO Jack Fusco summed up what engineers understand best with this statement: “2012 was a breakout year for Calpine, as we capitalized on the secular shift toward greater utilization of combined-cycle gas turbines. . . . We achieved record operating results, generating 116 million MWh—23% more than last year. The increased generation was primarily due to our excellent powerplant operations and unprecedented coal-to-gas switching. Overall, our business continues to be resilient across a wide range of natural-gas prices.”
More good news for the company was that plant personnel were able to reduce the cost of major maintenance and hold plant operating expenses essentially flat. Fusco attributed this to continued focus on operational excellence and preventive maintenance. The result: The company’s lowest-ever annual forced-outage factor—1.6% fleet wide.
Highlights in asset management included the sale of the 847-MW Broad River Energy Center peaking facility in South Carolina for $504/kW and the 603-MW combined-cycle Riverside Energy Center in Wisconsin for $667/kW; purchase of the 800-MW Bosque Energy Center combined cycle in central Texas for $540/kW; and plans to bring online about 1600 MW of additional gas-fired capacity in California, Texas, and Delaware over the next 30 months.
After adding in new long-term contracts for more than 2100 MW, the good news amounted to a surplus of $1 billion at the end of 2012, enabling a hefty increase in Calpine’s share repurchase program.
Notable achievements in power operations for 2012 included the following:
- Maintained stellar safety metrics. Plants recognized for 10 years of service with no lost-time accidents included the Westbrook, Pine Bluff, Baytown, Zion, Tasley, Missouri Avenue, Crisfield, and Bayview Energy Centers; plus, the Geysers plants Aidlin, Sonoma, Cobb Creek Quicksilver, and Socrates.
- Starting reliability, fleet-wide was 98.3%.
- Capacity factor of combined-cycle plants increased to 52.3% in 2012, up from 42.6% in 2011.
- Top producer was the Deer Park Energy Center, which generated 6.2 million MWh in 2012, the most by any individual plant in fleet history.
Development projects include these:
- Russell City Energy Center, a 429-MW (net-interest base-load capacity) combined cycle is expected in service this summer. Calpine holds a 75% share in the facility, which has a 10-year power purchase agreement (PPA) with PG&E.
- Los Esteros Critical Energy Facility, a 4 x 0 LM6000-based peaking plant, is being repowered as a 309-MW combined cycle. It also has a PPA with PG&E and is expected in service this summer.
- Channel and Deer Park Energy Centers in Texas each are being expanded by approximately 260 MW. COD for both is expected in summer 2014.
- Garrison Energy Center, a 618-MW combined cycle, will be built in two equal stages. COD for the first stage is expected by the summer of 2015. The air permit is in hand.
- Turbine modernization program. Through the end of 2012, Calpine had upgraded 11 Siemens and eight GE turbines, adding 200 MW of capability. At least three more projects are planned.
NV Energy: New assignments, EEI award
NV Energy has strategically repositioned the top engineers in its generation department to streamline the organization for economies in operation and maintenance consistent with VP of Energy Supply Kevin Geraghty’s demanding goals for world-class performance.
Dariusz Rekowski, formerly director of O&M, moves into Geraghty’s old position as generation executive, vacant since the latter was promoted last fall. Brian Lawson, who has had a wide range of management responsibilities since joining the company in 1985, takes over Rekowski’s former office. Additionally, Peter Steinbrenner is promoted to director of generation engineering; Bill Simko is named director of special projects.
These five top managers are known to many readers for their insightful presentations and volunteer work on behalf of the industry’s user groups—especially CTOTF™, Combined Cycle Users Group, Southwest Chemistry Workshop, and the Air-Cooled Condenser Users Group, which Geraghty’s team founded five years ago.
Meanwhile, out at the Arrow Canyon Complex, about 45 minutes from headquarters, Director Steve Page announced new responsibilities for his team members to enable the integration of activities at the four 2 x 1 F-class combined cycles he manages (two at Chuck Lenzie, one at Silverhawk, and one at Harry Allen) into one operation.
Ron McCallum is now production manager for asset management, responsible for work planning and long-term equipment health; Forest Hawman is production manager for strategic issues and other ongoing programs and activities; and Shane Pritchard is production manager for tactical issues, including plant operations and routine maintenance execution.
NV Energy’s Fort Churchill Generating Station, a 226-MW gas-fired steam plant in Yearington, Nev, was honored recently by the Edison Electric Institute with the organization’s Safety Achievement Award for 25 years of operation without a lost-time accident. To put the achievement in perspective, the last lost-time accident occurred at Ft Churchill on Mar 30, 1987, when Ronald Reagan was president and a gallon of gasoline cost less than $1.
Over the years, the plant has embraced more than 1500 safety suggestions, which surfaced through safety audits, safety committee recommendations, and individual contributions.
NAES Corp, Issaquah, Wash, announces that Robert E Fishman has been named president and CEO. The industry veteran probably is best remembered by readers of this publication for his time at Calpine Corp as VP operations, engineering, and development and as president of PB Power Inc.
In related news, Tony Downey is appointed director of safety for maintenance and construction for the company, based in Pittsburgh.
ThermoEnergy Corp, Worcester, Mass, appoints James F Wood, former deputy assistant secretary for DOE’s Office of Clean Coal, president and CEO. He was subsequently elected board chairman. Before moving to Washington, Wood had been president of Babcock Power Inc, Babcock & Wilcox Co, and Wheelabrator Technologies. He also has authored several articles for the CCJ over the years.
Associated Electric Cooperative Inc, Springfield, Mo, announces the promotion of Gabriel Fleck to manager of gas plant operations. He takes over for Bob Pasley, who retired. Fleck is best known to most CCJ readers for his tireless work as chairman of the 501D5-D5A Users.
Turbine Generator Maintenance Inc (TGM), Cape Coral, Fla, a third-party provider of inspection, maintenance, and repair services for steam and gas turbines, announces organizational changes to support its continued growth. Mark Sherrill is appointed director of steam turbine/generator services. In his former life as a user, Sherrill was a regular participant in meetings sponsored by the Western Turbine Users Inc and the 7EA Users Group. He was a member of the latter’s steering committee for a few years. Ben Irvine is named director of generator services and David Hamilla director of gas turbine services. Ray Haralson is promoted to president of TGM Servicios Limitada, Concepcion, Chile. David Branton continues as the company’s CEO.