Focus on O&M

Inlet fogging systems for combustion turbines achieve their effect at the molecular level: The cooling effect occurs by converting thousands of gallons of water into single evaporated molecules suspended in the air. The right fog pattern comes down to a matter of selecting the best nozzle design and proper placement in the inlet air stream.

Correct welding procedures are extremely important elements of the work done by the PSEG Central Maintenance Shop (serving Public Service Electric and Gas Co., PSEG, a New Jersey utility). We have, for example, a Critical Weld Inspection Program for high-temperature pressure piping whose goal is to identify cracks in high-temperature piping welds.

In the May issue, we discussed the importance of either preventing copper plating of the high-pressure (HP) steam turbine rotor or finding a good foam or mechanical removal means of restoring lost efficiency. In that article we noted that “copper deposits typically form on the stationary nozzle block or first-stage stationary blades” and that those deposits usually result in a steam turbine loss of capacity at a rate of about 2 to 3 MW per month. We also stated that the “general rule of thumb is that there is a reduction of about 1 MW of generating capacity for each 1 to 2 pounds of deposit that accumulates on the HP turbine.

This is the fourth in a series of predictive maintenance (PdM) articles that began in the April “Focus on O&M” with an introduction to PdM as a process whereby maintenance is performed based on the condition of the equipment rather than on a predetermined interval. In the May and July issues, we began exploring specific PdM techniques, such as motor-current signature analysis and oil analysis.

JEA’s Northside Generating Station in Jacksonville, Fla., Units 1 and 2 were built in 1966 and 1972, respectively, although the Unit 2 boiler had not operated since 1983. Both were heavy oil– and natural gas–fired steam units rated at about 300 MW. The utility “repowered” those two units by removing the old boilers and adding new circulating fluidized bed (CFB) boilers (Figure 1) that entered service in 2002. At that time, they were the world’s two largest CFBs, and the plant won POWER’ s Plant of the Year Award.

Acoustic pulse reflectometry (APR) is a tube inspection method that has been gradually gaining acceptance as a tool for heat exchanger inspection. Different types of heat exchangers operating in different operating environments have different failure mechanisms, making some of them more suited than others for inspection by APR. Finned tube heat exchangers are a typical example of heat exchangers particularly conducive to APR inspection.

Now that many flue gas desulfurization (FGD) systems are reaching middle age, corrosion repairs of structural and process vessels are becoming more common. Corrosion is caused by condensates of acids formed during the FGD process, which accelerate pitting and crevice corrosion, particularly in scrubbers where high sulfate solutions are present. Scrubbers lined with 2205 duplex stainless steel are among the most vulnerable to pit or crevice corrosion, from both chlorides and fluorides.

When adding, modifying, or upgrading a system, many critical infrastructures conduct a factory acceptance test (FAT). A FAT includes a customized testing procedure for systems and is completed before the final installation at the critical facility. Because it is difficult to predict the correct operation of the safety instrumented system or consequences due to failures in some parts of the system, a FAT provides a valuable check of these safety issues. Similarly, because cyber security can also impact the safety of critical systems if a system is compromised, it makes sense to integrate cyber security with the FAT.

Longview Power, a 695-MW coal-fired power plant now under construction in Maidsville, W.Va., is scheduled to begin commercial operation later this year. The $2 billion project reached 580 MW in early June, just a month after completing the “first fire on coal” schedule milestone. Testing and tuning of the controls and various systems continue.

Enwave Energy Corp.’s district heating plants in downtown Toronto will be operating cleaner and more efficiently before the fall 2011 heating season begins when boiler upgrades now under way are completed. Enwave hired Benz Air Engineering (BAE) to design and install upgrades to all eight boilers inside Enwave’s Pearl Street Station. When the $20 million project is completed, the retrofits will produce energy savings exceeding $5 million per year. In addition, the company will receive incentives of $100,000 per boiler from Enbridge, its natural gas provider.

Steel piping systems used to convey coarse materials, often over long distances, are under constant attack from abrasion. In power plants, the materials are usually coal and limestone slurry. The common industry solution has been to install abrasion resistant (AR) pipe that is much harder on the Brinnell Scale than standard steel pipe. The harder the inner wall, studies have shown, the better it resists the gouging or plowing action of abrasive sliding particle flow.

A record 400 attendees participated in KEMA’s 22nd annual Executive Forum in San Antonio, Texas, in late April to debate and discuss the “retail resurgence” of competitive electricity sweeping America.

Following the conclusion of the KEMA conference (see previous story), Mark Axford had the opportunity to talk with Phillip Tonge, recently appointed president of Spark Energy LP. Spark Energy is a retail energy provider (REP) of electricity and natural gas in 16 states that have opened their markets to competition for industrial, commercial, or residential customers.

This installment of the series continues our review of different conditioning-monitoring techniques commonly in use at power plants using any generation technology. In the May issue we began exploring specific PdM techniques with an examination of electrical surge comparison and motor-current signature analysis.

The North American Electric Reliability Corp. (NERC) Reliability Standards are under constant revision even while new requirements are under active development. Three important regulatory definitions are currently being contested.

Radial, axial, and circumferential metallic seals installed on rotary, regenerative air preheaters have evolved little from the original metal strip designs that date back to the original Ljungström preheaters developed nearly a century ago. Unfortunately, metallic strip seals degrade soon after installation, allowing excessive air-to-gas leakage, which translates into increased fuel consumption and fan power.

In November 2008, a central Texas utility commissioned HPI, a full-service turbomachinery design and construction firm based in Houston, to perform a major upgrade of its plant’s power distribution and turbine control systems.

Many large utility-scale units with copper alloy condensers and feedwater heaters lose generating capacity when copper and copper oxide deposits develop on high-pressure (HP) steam turbine blading. It is not unusual for a 400-MW unit to lose 10% of its generating capacity over a six-month period when water treatment processes aren’t properly tuned to prevent copper transport in the steam and condensate systems. In fact, one utility reported that it lost 20 MW of capacity in one month because of such deposits. The financial implications of such deposits, particularly in power markets where plants are pushed to their generating limits, are tremendous.

This series of articles focuses on the nuts and bolts of predictive maintenance (PdM), also known as condition-based maintenance. A well-defined and well-executed PdM program saves time and money by reducing unneeded time-based maintenance tasks and by identifying and fixing problems before they cause equipment failure or plant shutdown. In this article, we begin introducing condition-monitoring techniques commonly in use at power plants.

This year’s series will focus on predictive maintenance (PdM), also known as condition-based maintenance.

Imagine this scenario: Two separate power plants experience a bowing problem greater than 18 mils with a steam-turbine rotor. The turbines are from the same manufacturer and several repair options are reviewed. Management at both plants selects an innovative approach involving removal of a substantial amount of material, which is replaced with weld overlay and then machined to correct diameters and centerline of the balance piston area. One plant’s insurance company covers the repair, the other plant’s doesn’t. Why?

Thule (“Two Lee”) Air Base is a 254–square mile base located in a coastal valley in the northwestern corner of Greenland, within the Arctic Circle. The base, the U.S.’s northernmost military installation, is nestled between mountains and surrounded by icebergs and glaciers as far as the eye can see.

Beginning each spring and continuing through the fall, backpressure readings at Rosebud Operating Services Inc. indicated substantial drops in the condenser’s efficiency. Increased backpressure results in higher net plant heat rate and a corresponding measurable decrease in power generation.

On January 27, the U.S. Chemical Safety Board (CSB) released a case study examining the causes of a heat exchanger rupture and ammonia release at the Goodyear Tire and Rubber Plant in Houston in 2008. Use these lessons learned to check your employee tracking system and to determine whether your plant has installed valves that […]

If your facility has recently seen an upsurge in bearing failures on boiler feedwater (BFW) pumps, you are not the only plant experiencing these unnecessary and costly failures. The failure causes are often elusive, which is why plants have so many unresolved repeat failures.

Designing large package boilers rated at over 400,000 lb/h steam production is a challenge because of shipping limitations within the U.S. and Canada.

Sudden bumps and shocks are great fun when you are off-roading or are riding on a rollercoaster. But when you are operating a piece of equipment, you want it to be running as smoothly as a Cadillac rolling down the interstate. Sudden changes in pressure produce vibration, cavitation, and water hammer and generally lower the lifespan and reliability of fluid systems.

In all of these cases, frequent oil analysis monitoring and preestablished action plans were able to allow for transformer replacement before the occurrence of a catastrophic failure. Exelon’s experience, as well as that of other power utilities across the grid, has spawned a report by the Institute of Nuclear Power Operations (INPO) of Atlanta, Georgia, that recommends that performance monitoring and trending be applied to all large transformers in order to establish a baseline for transformer maintenance strategies.

Survey wind turbine manufacturers about how to calculate wind farm availability and you will get countless different definitions and exceptions to the rule.

The quality of the cooling water intake and the amount of debris in that water affects the operation and performance of the condenser and therefore the thermal performance of the typical steam plant.