O&M

By design, combined HP-IP turbines have a small amount of internal leakage from the high-pressure turbine to the intermediate-pressure turbine. As turbines age, the leakage increases considerably and becomes excessive, creating a heat rate penalty and possibly a reliability problem. Last month we explored the symptoms and causes of steam leakage within GE steam turbines and how to correct the problem. In Part II, we examine the same issues for Westinghouse and Allis-Chalmers turbines from both theoretical and practical angles.

Several states have mandated faster and/or deeper reductions in plant mercury emissions than those called for by the Clean Air Mercury Rule. Unfortunately, differences between plants make accurate evaluation of control options difficult. In most cases, even statistically based Hg emission models don’t pass muster because they don’t account for the dynamic chemical behavior of Hg species in gas cleaning systems. This article describes one system evaluation tool that has been validated using Hg field test data from 50 full-scale flue gas cleaning systems. It is already being used by TVA and other utilities.

Have you bought electrostatic or agglomeration equipment to rid your turbine oil of varnish deposits, but its varnish potential rating failed to improve? Or, after an initial drop, has the varnish potential returned to its previous level? Even worse, have you had recurring valve sticking problems after making a sizeable investment to "solve" this problem? Welcome to the world of soluble varnish caused by autodegradation. Read the unvarnished truth about varnish and how to get rid of it for good.

Hydro-demolition speeds reactor dome entry;
Tips for keeping your unit stable;
Air makes heavy move a breeze

When injuries or accidents occur, the employer ultimately loses on two counts: increased medical costs and employee absences. A policy of "safety, compliance, and then production" is more than just good business; it’s also good stewardship of the health and safety of employees who deserve no less.

The 1990 amendments to the Clean Air Act require coal-fired power plants to reduce their emissions of the pollutant SO2. To do so, many have switched to, or are considering switching to, Powder River Basin (PRB) coal. Unfortunately, PRB coal has a tendency to leave excessive and tenacious deposits on boiler heat-exchange surfaces. Complicating the problem, the distribution of the deposits is far from uniform.

The U.S. Department of Energy (DOE) and Great River Energy are testing a new coal-drying technology that could dramatically reduce the emissions of lignite-burning power plants. The project was selected for funding during Round I of the DOE’s Clean Coal Power Initiative (CCPI), a series of competitions to demonstrate a range of promising clean-coal technologies. […]

Lawrence Energy Center (LEC) proudly hosted about 60 representatives of the Powder River Basin Coal Users’ Group (PRBCUG) at its July 24th open house, luncheon, and plant tour. LEC was named the PRBCUG’s 2007 Plant of the Year at this year’s ELECTRIC POWER Conference and Exhibition in Chicago, May 1 – 3. Traditionally, the winning […]

Ready for your NERC close-up? / Synthetic oils for industrial applications

At the heart of most boiler combustion control systems (and most coordinated boiler/turbine control systems as well) is throttle pressure correction, usually applied by the "master controller." Throttle pressure is considered a key variable to control because it represents the energy balance between the boiler and the turbine. When throttle pressure is constant, the boiler […]

Cyber security and the grid; Harnessing the Yangtze;

Hydraulic system overhaul;

O&M problems not caused by cycling;

During 2005, about 150 million tons of coal were transported to power plants by hopper barges plying U.S. inland waterways. With coal-fired plants expected to continue producing 50% of America’s electricity, coal barge traffic is not likely to fall off. In fact, it may increase, for two reasons. One is cost. Shipping coal by barge […]

The Fayette Power Project (FPP, aka the Sam K. Seymour Power Station) is a three-unit, coal-fired generating plant sited near La Grange, Texas (Figure 1). Units 1 and 2, each with a nominal rating of 600 MW, are co-owned by the Lower Colorado River Authority (LCRA) and Austin Energy (AE). LCRA is a conservation and […]

Reducing NOx emissions from large utility coal-fired boilers has been a primary focus of the U.S. power generation industry since passage of the 1970 Clean Air Act and subsequent legislation. By the early 1990s, nearly all such boilers had installed some form of low-NOx burner (LNB) technology and/or overfire air (OFA) — the least expensive […]

Control pollution and slagging on a shoestring / Keeping HRSGs young, cool, and clean / Natural air conditioning

Hyperbolic cooling towers have a distinctive shape, but that form is subordinate to function—natural-draft cooling is cheaper than mechanical-draft cooling. The lower operating costs are offset to some degree by the higher cost of protecting internal tower surfaces from swings in humidity that foster corrosion damage. Learn how one utility added cathodic protection when it repaired its corroded hyperbolic tower, giving it a new lease on life.

Doctors and engineers realize that solving a health problem is better done by identifying and eliminating its cause than by treating its symptoms. For machinery, the class of multidisciplinary methods known as root cause analysis (RCA) is an important tool for addressing chronic reliability problems. But RCA often is improperly applied to lubrication-related problems. Read on to learn how to use the technique correctly.

Want some good news about your predictive maintenance program for a change? A recent research report by the Aberdeen Group found the electric utility industry benchmarks exceptionally well against other industries in its PDM practices. In fact, the research found that best-in-class companies outperformed industry peers in improving asset availability by up to a three-to-one margin. In a web exclusive, the Aberdeen Group has provided its report for download from powermag.com as a service to our readers.

Part I of this three-part series (POWER, October 2006) explored the negative impacts of sulfur trioxide (SO₃) on the operations and maintenance of back-end plant equipment. Part II (February 2007) listed and quantified the likely and potential benefits of limiting the concentration of SO₃ in flue gas to 3 ppm at the entrance to the air heater. This final part describes the characteristics of an optimal SO₃ removal technology and details the operating experience of a patented process that has worked successfully at a half-dozen plants for up to three years.

The challenge for suppliers of aftermarket turbine blades is that their starting point is an existing blade and nothing else. There are no CAD models, drawings, measurements, tolerances, or inspection data associated with it. However, thanks to the latest in computer tools, a blade now can be digitally recreated to exact specifications and built using the latest design and manufacturing practices. Here’s an inside look at how turbine blades are captured, reconstructed, inspected, and remade to be better than the originals.

The critical subset / Aging workforce challenges / Tighter tolerances in retrofits / Writing sensible start-up and shutdown procedures

The term "water hammer" encompasses a handful of hydraulic and thermohydraulic mechanisms. They include water hammer in steam and water piping, water piston, water induction, flash condensation and evaporation, and shock waves generated by transonic flow. All can lead to failures of steam and water cycle components and put plant operators and workers at risk. Proper design and O&M practices can keep water hammer and similar phenomena under control.

A century ago, boiler explosions were an all-too-familiar event. But with the universal adoption of the ASME Boiler and Pressure Vessel Codes in 1914, explosions caused by poor design or manufacturing became relics of history. Electrical classification codes had the same effect on safety. This article explains how designers and operators practically apply those standards. Code details and samples of area classification drawings for a gas turbine plant are included in an online supplement (see end of story).

Carbon capture and sequestration (CCS) have elbowed their way into the nation’s lexicon with the rise in concern over climate change. But few of the journalists who are hyping global warming have taken the trouble to learn the ins and outs of producing affordable electricity from coal. Citizens of the industrialized world now wring their […]

As gencos seek to improve plant reliability and availability, many are turning to on-line condition monitoring for help. Huge advances in the capabilities of on-line diagnostics have occurred over the past five years. By using this technology, plant personnel can spot early warning signs of impending equipment failure and take action to correct the underlying […]

Dominion Generation (DG) has installed selective catalytic reduction (SCR) systems on many of the large coal-fired generating units it operates. The catalyst used has an SO2 to SO3 oxidation rate of about 1%, which roughly doubles the SO3 concentration at the outlet of the boiler economizers. The magnitude of the increase was proportional to the […]

Flyash and condensed sulfur trioxide (SO3) are the major components of flue gas that contribute to the opacity of a coal plant’s stack emissions (stack opacity). Estimates are that 75% to 85% of bituminous coal-fired plants with selective catalytic reduction (SCR) and/or wet flue gas desulfurization (FGD) systems are likely to produce enough SO3 vapor […]

The compliance clock is ticking / First-class maintenance in a developing country / Bypass losses squander big bucks / Revised operating procedures

A systematic, performance-driven maintenance program for optimizing combustion can achieve great results. The challenge for an O&M staff is deciding which proven strategy and tactics for reducing NO_x and improving plant reliability to adapt and implement. The structured approach presented here has proven its worth at several plants that have wrestled with problems similar to yours.

The welds on superheater and reheater headers are arguably the most stressed parts of a modern steam plant. For that reason, it’s surprising that they also may be the most under-inspected. Cracks are rare, but they can be repaired if found early. One plant avoided a long forced outage to replace a reheater outlet header by using the correct condition assessments and welding techniques.