Power Engineering

Intermountain Generating Station


George Cross, Intermountain plant manager
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The Intermountain Generating Station, a 1775 MW coal-fired power plant in Delta, Utah, is owned by the Intermountain Power Agency, an organization of 23 Utah municipalities. The Los Angeles Department of Water and Power (LADWP) is the operating agent for the plant. The two-unit plant features Babcock & Wilcox subcritical boilers, GE tandem compound steam turbines, and low-NOx burners, fabric filters and a scrubber for emissions control. Power can be transmitted along several routes: a 490-mile 500 kV DC line to Adelanto, Calif.; two 50-mile 345 kV AC lines to Mona, Utah; and one 144-mile 230 kV AC line to the Gonder Station near Ely, Nev. About 95 percent of the energy is sent to California.

Intermountain's operating record has been remarkable since coming on-line in the mid-1980s. Capacity factors have consistently averaged 85-95 percent, well above the industry norm, with operating availability in the 90-95 percent range. Part of the reason for the plant's success can be traced to its location. "Sitting in the desert, we have to be pretty self-sufficient," says George Cross, plant manager. "We maintain our own fire brigade crew and hazmat team, as well as fully independent engineering, purchasing and accounting departments. This has built teamwork and has helped sustain our performance figures."

Intermountain has capitalized on the original conservative design of the plant. For example, the boiler is about 70 feet taller than comparable designs for the same steam flow, which has enabled the plant to minimize fouling and slagging. Redundancy was also built into various systems, such as the pulverizers and water treatment equipment, although some of this redundancy is being lost as the units have been upgraded in recent years.

Boiler tube leaks, the bane of most fossil power plants, have been held in check at Intermountain. Most years, the plant has none, or only a few. Plant management attributes the success to carefully following EPRI guidelines for water chemistry control; a good working relationship with the Energy Control Center in Los Angeles, which works with the plant if a load drop is needed to address a chemistry problem; and to a fully equipped chemistry laboratory. "We've never had a water chemistry-related tube leak in the history of the project," says Cross.

Using its plant information system, Intermountain has implemented an effective heat rate improvement program that relies on 13 controllable parameters, such as main steam temperature, main steam pressure, and exit flue gas temperature. "Each of these parameters is related to a corresponding loss or gain in tons of coal burned to give the operators - as well as the supervisors and engineers - a real-time indication of how the plant is running," says Cross. "We also conduct refresher courses in heat rate improvement to keep our employees aware of how their actions translate into overall plant efficiency." The plant had a gross heat rate of 9,028 Btu/kWh in the most recent fiscal year, with a goal for the coming year to reach 9,015 Btu/kWh or less on a gross basis.

One of the main components of the heat rate improvement plan is the high-pressure steam turbine upgrade program underway at Intermountain. "We were approached by GE and Alstom about upgrades they had performed at other stations, and they felt our plant was a good candidate," says Cross. "We discovered that the economics were terrific, at about $200/kW." This past Spring, Alstom performed the High Pressure Turbine upgrade on Unit 2, increasing capacity from 875 MW to 900 MW, without burning any additional coal. The Unit 1 upgrade will be completed next Spring. "We're getting a payback on the HP upgrade project of approximately one year, based on the current market cost of replacement power," says Cross.

With only one four-week outage every other year for each unit (with a one-week outage in alternate years), outage management is critical at Intermountain. "When we did the HP turbine changeout on Unit 2 this past spring, Alstom had never done one in under six weeks," says Cross. "We were able to get it done in four weeks because of the advance planning and the commitment to 24-hour work schedules." The boiler is always a challenge during outages because of the tremendous amount of surface area. Intermountain throws 20-30 people into the boiler during the first week of the outage to conduct a thorough inspection, which leaves time for the maintenance staff to make repairs.

Cross-training has also benefitted outage work significantly. Entering an outage, a bare minimum crew is left to run the unit still on-line, enabling the extra operations personnel to assist in outage maintenance tasks. "Our basic philosophy is that no work belongs to any one individual or group," says Cross. "During normal plant operations, a back-shift maintenance crew - consisting of two mechanics, one I&C tech, and one electrician - rotates with an operating crew. These guys are here 24 hours a day, so if we have a problem, we don't have to call someone out. And because they rotate with an operating crew, they get to know each other better, improving the relationship between departments."

The personnel story at Intermountain is unique. Charged by the project with hiring a Utah workforce when the plant was built, Intermountain ended up hiring 75-85 percent of its staff from Utah, most of whom had no power plant experience. These first employees, who trained for 2-3 years in plant fundamentals in a classroom environment and used a full-plant simulator before Unit 1 came on-line, have become the backbone of the workforce. "Our turnover has been less than 2 percent over the history of the project," says Cross, "and 15-20 percent of the entry-level laborer workforce typically have college degrees."

Intermountain is proactively addressing the aging of its workforce. "Within the next 5-8 years, 75 people could retire from critical plant positions," says Cross. "We're striving to capture this experience by having some of these world-class craftsmen - boilermakers, welders and others - teach their skills to less experienced employees. We've added about 25 people to the organization in anticipation of it taking 3-5 years for those people to be trained to a skilled craft level."

Intermountain pays special attention to the physical appearance of the plant, believing that the pride employees take in keeping their plant clean translates into the pride they take in keeping the equipment running smoothly and effectively. "At the very beginning, we instituted a staff walkdown on every Monday afternoon," says Cross. "The plant manager and the staff walk down one of 13 areas in the plant to identify things that need to be improved, cleaned, etc."

Another unique personnel twist at Intermountain is that operators are used to haul limestone for its scrubbers. The plant paid for the operators to obtain commercial drivers licenses. When the operators have some downtime after getting their equipment checked and cleaned, they can jump in a truck to get a few loads of limestone. This saves the plant about $150,000 annually, and is a defining example of the self-sufficient spirit that pervades the Intermountain culture.

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