O&M

Relatively simple upgrades to legacy turbine systems can yield big payoffs in efficiency and reduced maintenance.

Boiler tube failures (BTFs) are responsible for the largest portion of availability loss (about 4%) in the fossil boiler industry, and approximately 25% of all tube failures are due to fly ash erosion (FAE). An Electric Power Research Institute report indicated that the problem was being managed in U.S. utilities by maintenance activities that were put into effect each time a boiler was taken off-line. The cost of an individual repair was a small fraction of the forced outage cost, and therefore has been considered justified in the past. However, many forced outages continue to be experienced each year due to FAE, and in many cases, these occur at identical locations, indicating that applied solutions relieve, but do not cure, the problem.

This is the sixth in a series of predictive maintenance (PdM) articles that began in the April 2011 “Focus on O&M” in which the essentials of PdM were introduced. In this occasional segment, we have explored specific PdM techniques, such as motor-current signature analysis, oil analysis and thermographic analysis and their routine use, and ultrasonic and vibration analysis. In this issue we look at lubricating oil wear-particle analysis.

A chronic operational problem with circulating fluidized bed boilers is ash buildup or agglomeration that turns into slag, which forces frequent shutdowns for cleaning. Solving the problem is tricky, because combustion efficiency relies on good fuel quality, but the best fuel for efficiency may not be the best fuel for minimizing furnace and tube fouling and ash plugging.

Low natural gas prices and still-soft electricity demand are forcing low-load and cycling operations at traditionally baseloaded coal units across the country. The resulting challenges were top of mind at the Electric Utility Cost Group’s (EUCG’s) fall meeting in Denver last week. One member of the EUCG’s fossil generation committee from an Ohio Valley utility said that cycling and low-load operations pose challenges for one of his company’s 1,300-MW coal-fired plants that “two years ago we wouldn’t have considered possible.”

After years of development, design, and construction, your plant is finally nearly ready for startup. But don’t light that cigar yet—at least not until you’ve developed a strategy for commissioning your water cycle chemistry. Root causes of corrosion can be predicted and avoided. The best way to avoid corrosion is to develop and implement plant-specific cycle chemistry commissioning guidelines.

Because Powder River Basin (PRB) coal is smaller, more friable, and contains more fine particulates than bituminous coal, controlling the fugitive dust generated as PRB coal moves from bunker to burner tip is problematic. The challenge for material-handling systems at power plants that have switched coals is to minimize this dust and capture it cost-effectively and without compromising safety.

The natural gas and electricity industries have entered into an increasingly codependent relationship as coal-fired electricity gives way to natural gas–fired generation. Both industries are firmly committed to providing reliable service, although each goes about its business in different ways. Utilities, regulators, and stakeholders are searching for ways to align interests and expectations.

Plentiful supplies of low-cost natural gas have changed unit dispatch orders across the U.S., led to thermal stress–induced maintenance issues at cycling coal plants, and resulted in management challenges at coal and gas units alike. This scenario is unlikely to change so long as gas holds its competitive edge over coal.

When Verbund Thermal Power needed reliable and flexible condensate pumps for its new combined heat and power plant in Mellach, Austria, it used a new type of self-regulating centrifugal unit. 

Nobody can schedule unplanned events that will affect power generation. And no one wants to start a day expecting an emergency to occur. But when critical systems fail in the power supply system, it’s time to respond. That’s a given of power plant maintenance.

AES Gener recently completed construction of twin coal-fired, 260-MW units in the electricity-starved desert of northern Chile that may serve as models for future hybrid-fossil plant designs. For meeting an aggressive construction schedule, integrating a 20-MW battery energy storage system, embracing desalination, using the first-of-its-kind seawater cooling tower in South America, and employing innovative financing methods, the AES Gener Angamos plant has earned POWER’s 2012 Plant of the Year Award.

Moving thousands of tons of coal per hour at high speeds through a complex handling system is a main cause of airborne coal dust in a coal-fired plant. Depending upon the coal’s characteristics, that dust can become explosive when its concentration reaches 80 g/m3 and, hence, a threat to life and property. The best option is to stop the dust from becoming airborne in the first place.

Complying with air emissions rules doesn’t always require construction of a scrubber or SCR. Finely ground trona has proven to be very successful at economically removing SO₃, SO₂, and HCl from stack gases.

Natural gas-fired generation enjoyed a competitive advantage through this past winter and spring as historically low prices for the commodity combined with mild weather and relatively light demand to turn the dispatch stack on its head and favor gas over coal. That advantage is narrowing as summer demand approaches. A senior market analyst with Bentek Energy expects coal-fired generation to be advantaged at least until the fall shoulder season.

Announcements about coal plant retirements have become commonplace. Are new EPA rules completely to blame, or are there other power market pressures at play?

The primary considerations in slurry valve selection are reliability in function and design, abrasion resistance, and ease of maintenance. In addition, valves with a straight-through, unobstructed flow minimize the effect of abrasion and therefore reduce the need for maintenance.

The season’s blockbuster includes white-hatted heroes, good-natured regulatory sidekicks, bar fights, and a lurking menace named Fugitive Dust.

A lot goes into the decision to upgrade a simple-cycle plant to combined cycle. Careful planning and analysis can make the difference between a profitable, successful switch and an expensive hassle.

None of you reading this magazine needs an article—or new governmental regulations—to tell you that flash fires and explosions involving coal dust can cause catastrophic incidents, fatalities, facility damage, and financial consequences.

Combined cycle power plants use fuels and other materials that can cause fires or explosions in the combustion turbine, ducting, or heat recovery steam generator. Purging that equipment with ambient air to displace residual combustible gases before starting is a normal safety practice. But when plants are cycled, the disadvantages of purging often outweigh the advantages.

Most power plants use some form of condenser performance-monitoring protocol. Some of those protocols are deficient because the proper instrumentation is not installed to collect the necessary data. Three case studies illustrate how collecting good condenser performance data enabled plant staff to troubleshoot problems and make good plant performance improvement decisions.

Coal combustion products often can be recycled into a variety of construction and building materials. However, first you must be able to retrieve the wet ash from a holding pond before the ash can be dried and sold.

Following safety rules is the foundation to eliminating injuries. Commonly, a safety presenter will say that safety rules are “written in blood.” At one time, such dramatic statements were a way to get attention and illustrated the seriousness of following safety rules. Today, more highly educated workers demand less drama and more facts.

This is the fifth in a series of predictive maintenance (PdM) articles that began in the April 2011 “Focus on O&M” in which the essentials of PdM were introduced. In the May and June 2011 issues, we explored specific PdM techniques, such as motor-current signature analysis and oil analysis. In the November 2011 issue, we introduced the value of thermographic analysis and its routine use. This installment focuses on ultrasonic and vibration analysis.

Natural gas–fired fleets comprising diverse turbine unit types are operating their units more these days because of the historic low price of natural gas. With increased operating hours, fleet owners are challenged to find the best ways to manage their SCR catalyst systems.

Confined space work is often considered to be one of the most dangerous types of work performed in power generation settings. Confined spaces may contain hazardous atmospheres, they can trap entrants, and they generally can increase the hazards associated with otherwise common tasks. When the risks are not recognized, workers all too often regard incidents as surprises, but the hazards of working in confined space can be predicted, monitored, and mitigated. These “accidents” are caused by unsafe conditions, unsafe acts, or both; all accidents are preventable.

Common fuel-handling problems in the power industry often result in production downtime, costing the owner perhaps up to $200,000 per hour. There are many areas within a coal-fired power plant where mishaps can cause stoppage of material flow. Here we discuss how to select the best switch technology to reduce the possibility of coal flow stoppages.

Optimizing combustion control is critical to reducing emissions and increasing plant operating efficiency, particularly for fluidized bed combustion (FBC) boiler plants burning biomass fuel that has unpredictable moisture content. The secret: measuring actual energy flow.