Harry Allen dedicated; latest 7FA combined cycle to enter service
NV Energy Inc’s President/CEO Michael W Yackira yesterday dedicated the just-completed 2 x 1 combined cycle at Harry Allen Generating Station, which is located about 30 miles north of the Las Vegas strip. The 7FA.03/DLN2.6 gas turbines that power the facility are the most recent units in the nominal 1000-engine Frame 7 fleet to enter service.
VP Generation Kevin Geraghty believes the heavily automated combined cycle will prove itself as the utility’s top performer. He also thinks that the experience gained in operating and maintaining the unit is critical to identifying (1) the most cost-effective upgrades for the company’s earlier combined cycles, (2) right-size future staffing levels, (3) skill sets required by tomorrow’s employees, (4) training needs, etc.
Workforce 20/20, a fleet-level initiative recently launched by Geraghty to prepare NV Energy’s generation department for the future, will make good use of data collected from the new unit. Over the next year to 18 months, he told the editors, the nine-committee Workforce 20/20 task force will put together a plan for accommodating the “silver tsunami” and an evolving generation portfolio. The effort involves nearly three-dozen employees from across the enterprise, aided by an outside facilitator.
Important to success is determining what energy supply will look like eight years from now; one committee is charged with that responsibility. Another was asked to determine the types of service-level agreements that may be required for internal/external services providers. Yet another is creating a job-analysis questionnaire and job descriptions for 2020.
Other committees have responsibilities for assessing staffing needs, developing a labor strategy consistent with the 2020 workforce, creating a two-way communications process necessary for program implementation, identifying emerging technologies and aligning technology strategy within the 2030 workforce, and related tasks.
Plant construction was completed within budget, according to NV Energy’s New Generation Executive Andy McNeil. Project Manager Nitin Luhar added that The Shaw Group Inc was awarded the EPC contract early in October 2008 and arrived onsite the following January. Robert Follett was Shaw’s project director when the “keys” were handed to the utility last weekend. Robert Burke headed the effort for owner’s engineer Zachry Engineering Inc.
McNeil said the specifications for Harry Allen followed the baseline design of the nearby Chuck Lenzie Generating Station, in large measure to maintain consistency in operations, maintenance, and spare-parts inventory between the two plants. The basic layout calls for generous centerline spacing between the gas turbines to facilitate O&M. The steam turbine is placed between the two unit centerlines but beyond the HRSG stacks.
A key project goal was to build a cost-effective efficient and reliable plant capable of competing against merchant generators. This meant avoiding the gold-plating sometimes associated with utility-owned power projects.
Incorporating lessons learned from previous projects into specifications and procedures was critical to this goal. McNeil said his construction team, and the generation group, had gained valuable experience in building and commissioning in the last six years nearly 3000 MW of new gas-turbine-powered capacity, and that was brought to bear on the Harry Allen project.
Luhar headed up the cataloging of best practices with help from Zachry Engineering. He told the editors that NV Energy has a file—a living document if you will—containing more than 200 best practices. Some are relatively simple and might even seem insignificant, Luhar continued. He offered use of quality fasteners and pipe coatings as examples of some “small” things incorporated into the spec that have a positive impact on job quality. Access design best practices from the project.
Having a tighter spec also saves time by not having to “reinvent the wheel” and by not making the same errors multiple times. One example is the handling of demin water during steam blows to minimize leaks. This is important because spills of demin water on the desert floor are permit violations that can initiate “stop work” orders.
The editors asked Luhar what stood out in his mind about this project, something he’d like to experience on all construction projects. His reply: An outstanding level of communication between Shaw and NV Energy personnel. “We never had difficulty working things out,” he said. Constructive attitudes prevailed throughout the project.
Operations. Assistant Regional Director Brian Paetzold was assigned to the project soon after site work began to help assure that the new combined cycle would meet operational expectations. He had managed the Lenzie facility for a period and was well aware of issues the company didn’t want resurfacing at Harry Allen. Plus, Paetzold knew about the experiences of others and their best practices through participation in industry organizations such as the 7F Users Group.
Regional Director Steve Page, who is responsible for the Arrow Canyon Complex (Harry Allen, Lenzie, and Silverhawk Generating Station), and Paetzold reviewed some of the new plant’s features, beginning with automation. Total staff at Harry Allen is 19, with two operators on a shift—one in the control room, the other outside.
When you’re running a plant designed for 150 starts per year with two operators, Paetzold said, NV Energy’s experience suggests automating to the maximum extent possible. For example, he asked rhetorically, why hand an operator a startup procedure when you can program all the steps into the control system and assure that the optimal program is run every time? Automation takes operator variability out of the equation, he added.
To achieve the high degree of automation employed at Harry Allen, virtually all field data and control functions flow through the Ovation™ distributed control system provided by Emerson Process Management, Pittsburgh. The only PLCs in the plant are those for the burner management system (HRSG duct firing), the static frequency converter used to start the gas turbines, and the filter press in the wastewater treatment system.
Enabling a high degree of automation is time-consuming, Page offered. But when this work is complete, your plant has a predictable behavior and can be managed more effectively. Paetzold offered some metrics: Roughly 2500 I/O points are brought into Ovation from each of the Mark VIe gas-turbine control systems and another 3000 or so from the steam turbine; water treatment and BOP add 13,000.
Shaw and Emerson did most of the work associated with configuring the DCS for automation. The effort required to capture operating data in OSIsoft LLC’s PI historian was not included in the EPC contractor’s scope. Harry Allen is the most advanced plant in the NV Energy fleet regarding data capture.
Data storage is cheap, Paetzold noted, “so we’re collecting all the information we can. We’re not sure exactly what we might need for analysis purposes in the future.” Some of the data captured in the near term certainly will help support Geraghty’s Workforce 20/20 initiative in determining future manpower requirements, training requirements, etc.
At this point, no decision has been made regarding the use of predictive analytics for supporting O&M decision-making.
The discussion turned to best practices adopted for Harry Allen. Page began with safety. He said a robust system of permanent platforms and ladders was installed to facilitate safe access to equipment by the one roving operator on duty after the day shift.
Paetzold said participation in 7F User Group meetings enabled better decision-making on gas-turbine package features. The Harry Allen 7FAs are equipped with the latest R0 blade correction and with bellows-type seals at the intersections of cross-fire tubes and combustors.
NV Energy, thought to have more air-cooled condenser cells than any other utility, applied some in-house lessons learned to the heat-rejection system. One was locating condensate pumps out from under the fan deck to facilitate crane access. Another was specification of new type of vibration shutoff device that can be desensitized on startup and load changes to prevent fan trips.
Paetzold said special attention was given to fan-blade selection and handling. Harry Allen’s 36 cells have 36-ft-diam, fixed-pitch fiberglass blades. Blades were handled with “kid gloves” to avoid “dings” that could initiate an in-service failure. Shaw ordered two spare sets of blades in case damage occurred during shipping or installation.
Evaporative coolers were selected for the gas turbines because of their better economics and reduced water use compared to chillers. Paetzold acknowledged that chillers have capacity and heat-rate benefits, but questions remain regarding life-cycle cost.
Details. The plant is designed to produce 484 MW on a 112F day with 11% humidity. Output is restricted by permit limits on heat input to the duct burners as well as to the gas turbines. It can produce 550 MW with duct burners and evap coolers in service when ambient conditions are favorable.
The D-11 steam turbine selected for Harry Allen is similar to the machines installed on the two Lenzie combined cycles: combined HP/IP casing with a double-flow LP section (30 in. last-stage blades) and configured for down exhaust. Generators are hydrogen-cooled.
The heat-recovery steam generators are traditional natural-circulation, triple-pressure horizontal units equipped with gas-only supplementary firing systems to support summer peak-load demand. The OEM’s SMART-box design was selected to simplify construction. It modularizes the harps in groups to reduce onsite handling. Oxidation catalyst and the SCR are designed to meet the permit limits of 2 ppm CO and 2 ppm NOx.