Preventing Condenser Tube Failures Through Effective Cleaning and Nondestructive Testing

Generating companies lose hundreds of millions of dollars annually to problems related to condenser and heat exchanger fouling, corrosion and tube leaks. In fact, the Condenser Tube Failure Control Program of Electric Power Research Institute (EPRI, Matthews, J.) disclosed that condenser tube failures contributed to almost 25,000 outages nationwide during a recent four year period and continue to be one of the most pressing issues related to plant output and availability. To adequately prevent condenser tube failures, effective condenser tube cleaning and nondestructive testing must be performed. Effective tube cleaning should ideally remove all deposits, leaving only the cleanest metal surface. Once tubes are free of fouling deposits, multi-frequency eddy current testing should be used to establish the overall integrity of condenser tubes. Plugging is recommended for the tubes with poor integrity that put condenser reliability at risk. If tube failures do occur, advances in tracer gas leak detection, specifically those using sulfur hexafluoride and helium, can be used to quickly locate sources of circulating water tube leakage and return the unit to reliable operation. This paper will examine implications of condenser tube fouling and failure, and the available nondestructive technologies for their prevention and correction.

A Case Study of Optimizing Combined Cycle Performance at Kalaeloa

Fuel is by far the largest expenditure for energy production for most power plants. New tools for on-line performance monitoring have been developed for reducing fuel consumption while at the same time optimizing operational performance. This paper highlights a case study where an online performance-monitoring tool was employed to continually evaluate plant performance at the Kalaeloa Combined Cycle Power Plant. Justification for investment in performance monitoring tools is presented. Additionally the influence of various loss parameters on the cycle performance is analyzed with examples. Thus, demonstrating the potential savings achieved by identifying and correcting the losses typically occurring from deficiencies in high impact component performance.

Micro-Hydro Power Systems: Current Status and Future Research in Pakistan

The total installed electric power capacity of Pakistan is about 20,000 MW. Pakistan is currently facing a power deficit of about 4,000 MW. This deficit is creating huge difficulties for the consumers as electrical power load shedding has become a norm in all over the country. Currently only about 33% of the total power is being produced by hydro sources and major electric power is still produced by burning oil and gas. The hydro potential of Pakistan is estimated to be about 41 GW, out of which 1,290 MW can be generated by micro-hydro systems. These potential off grid micro-hydro systems are very essential for the consumers living in the remote areas of Pakistan and may be installed on canals and water falls which are abundant in the remote areas. This paper discusses the potential and the status of installed of hydro power systems in Pakistan. Cross flow turbines are being manufactured in Pakistan and are usually quite successful for micro-hydro systems. However, cross flow turbines are not suitable for majority of the prospective site conditions. Furthermore, custom made conventional turbines are not mass produced and for the micro-hydro systems, standard centrifugal pumps may be used as turbines. These centrifugal pumps are easily available in the market at comparatively much lower cost and shorter delivery periods. A pump was installed at a suitable site for generation of electricity, while running in turbine mode. It was initially estimated that the Pump as Turbine, PaT would be able to generate about 70 kW of power based on the available flow rate and head parameters at the site. Currently only half of that power is being generated by the PaT, under study. Efforts are underway to rectify the problems being faced and improve the power generation capacity of the installed unit. This paper discusses the problems associated with the use of PaT and measures being undertaken to make it feasible for the use of micro-hydro systems. Two major issues; draft tube design and presence of trash in the canal water, responsible for performance deterioration have been discussed in this paper.

The Steam Turbine Retrofitting of Six Boiling Water Reactor Units Using Innovative Engineering and Laser Scanning Techniques

Alstom Power is executing the steam turbine retrofit of six nuclear units for Exelon Generation in the USA. The existing turbine-generators are an 1800 RPM General Electric design originally rated at 912 MWe and 1098 MWe and powered by Boiling Water Reactors. 18 Low Pressure inner modules will be replaced, with the first due to be installed in March 2010. This project is particularly challenging — the aggressive retrofit installation schedule is compounded by the requirement to handle radioactively contaminated equipment and also comply with demanding regulations applicable to BWR plant. The author’s company has extensive experience in the steam turbine retrofit business, having supplied around 800 retrofit cylinders globally since the 1970’s. However, this LP upgrade challenges the established techniques used in the business and requires extraordinary effort. Traditional retrofit engineering and installation principles have been interrogated and developed to meet the specific requirements of this project. Innovative techniques are introduced, including the extensive use of the Leica HDS 6000 laser scanner to model the existing plant. The approach has advanced the field of steam turbine retrofit design and installation significantly. The first section of this paper focuses on the extraordinary considerations of the project and the challenges surrounding BWR plant. The second part describes the laser scanning technique and the application of scan data. It outlines the innovative solutions which have been developed.

Temperature Measurement Applications in Power Plants

Temperature is one of the most widely measured parameters in a power plant. Temperature is monitored and also used for control in some areas. The paper covers some of the basics of Temperature measurement, and leads into some of the technical advances that impart higher a degree of safety and reliability to power plant operation. These advances are based on some of the latest and innovative technologies that are being implemented in process instrumentation. Irrespective of the type of power plant (coal-fired, Oil or gas based), temperature measurement remains high on the list for operational excellence throughout the plant. Implementation of some of the new technologies results in improved Safety and lower installation and maintenance costs. Incorrect measurement information due to temperature effects, non linearity or stability can result in major equipment getting damaged. Ensuring instruments that have minimal downtime from a maintenance standpoint, not just devices that have been evaluated to provide Safety Integrity Level service in Safety Instrumented Systems, is crucial for daily operations in a power plant.

Conveyor Architecture for the 21st Century

To address issues associated with the recently updated OSHA Instruction on combustible dust hazards, this presentation will explore an innovative concept of conveyor design. The author will also examine two “leading edge” conveyor technologies and review recent projects that employed these two technologies. This presentation will first address concerns associated with the OSHA Instruction on combustible dust hazards by exploring the architecture concept for conveyor design and the new dust accumulation resistant conveyor structure. This pioneering approach to conveyor design focuses on prevention of fugitive dust accumulation and ease of maintenance. The next of these advanced technologies is “engineered-flow” chutes. Designed from material testing and flow studies, these transfer chute systems provide better material control, continuous flow at higher capacities, and dramatic reductions in material spillage and the release of airborne dust. By regulating the path of material movement, these engineered chutes improve the load placement on the belt, eliminate chute blockages, reduce safety hazards, and minimize maintenance costs. A third leading edge conveying system is air-supported belt conveyors. Rather than using rollers, these leading edge systems use a film of air rising from a troughed pan to support the belt and cargo. These totally enclosed conveyors offer a number of benefits, including improved tracking, improved control of dust and spillage, and reduced friction and power consumption. In this presentation, the author will present “project profiles” of recent installations of these systems. The author will look at the reasons these systems were selected and report on the lessons learned from system engineering, installation, and operation. These projects will include systems handling Powder River Basin (PRB) coal in mines and power plants.

Design Methodology and Valve Sizing for Heater Drain Systems

Heater drain systems in fossil and nuclear power plants have proven to be among the most complex systems to design due to the occurrence of two–phase flow phenomena. The overall performance of heater drain systems directly relates to proper sizing and design of the piping and control valves. Proper sizing is highly dependent upon accurate and conservative calculation of two-phase flow pressure losses. This paper outlines the various options of solution methods available to the engineer and details one possible method which is simple, yet adequate, and based on the homogeneous equilibrium model (HEM) for two phase flow for calculation of heater drain system performance. General comparisons are made to the more complex multi-fluid models, flow regime considerations, and non-equilibrium models.

Pyrolysis and Steam Gasification of Paper and Evaluation of Paper Char Kinetics

Main characteristics of gaseous yield from steam gasification have been investigated experimentally. Results of steam gasification have been compared to that of pyrolysis. The temperature range investigated were 600 to 1000°C in steps of 100°C. Results have also been obtained under pyrolysis conditions at same temperatures. For steam gasification runs, steam flow rate was kept constant at 8.0 gr./Min.. Investigated characteristics were evolution of syngas flow rate with time, hydrogen flow rate, chemical composition of syngas, energy yield and apparent thermal efficiency. Residuals from both processes were quantified and compared as well. Material destruction, hydrogen yield and energy yield is better with gasification as compared to pyrolysis. This advantage of the gasification process is attributed mainly to char gasification process. Char gasification is found to be more sensitive to the reactor temperature than pyrolysis. Pyrolysis can start at low temperatures of 400 °C; however char gasification starts at 700 °C. A partial overlap between gasification and pyrolysis exists and is presented here. This partial overlap increases with increase in temperature. As an example, at reactor temperature 800 °C this overlap represents around 27% of the char gasification process and almost 95% at reactor temperature 1000°C.

Ultrasonic Condition Monitoring in Power Plants

Instruments based on airborne/structure borne ultrasound technology offer many opportunities for reducing energy waste and improving asset availability in power plants. They expand the concept of “Condition Monitoring” to include much more than basic mechanical fault inspections. Since these instruments detect friction, ionization and turbulence, their inspection capabilities range from trending bearing condition to determining lack of lubrication, locating compressed air leaks and detecting arcing, tracking and corona emissions in both open and enclosed electric equipment. Portable, instruments based on this technology are used to trend and analyze bearing condition, detect leaks (pressure and vacuum), test valves and steam traps, identify electrical problems and identify potential problems in gears, motors and pumps. This presentation will provide a brief overview of the technology, its applications, energy savings cost analysis and suggested inspection techniques.

Energy Efficiency by Optimizing Annual Testing Schedules: Coordinating RATA Testing With Other Annual Test Requirements

Nearly every power plant in the US must undergo annual Relative Accuracy Test Audits (RATA testing) to confirm the values reported by their continuous emission monitoring systems (CEMS). In order to perform a RATA test, the plant must operate at one or more stable loads for a number of hours. Depending on the type of unit and fuel, the required load levels for RATA testing can range from low, mid and high loads for coal-fired units to a single (normal) load for oil and gas fired units or four loads (from partial load to maximum load) for units utilizing 40 CFR Part 75 Appendix E alternative monitoring systems. Many plants operate in a dispatch environment where the plant is not in control of their load from hour to hour, and some even from minute to minute, such as those operating under Automatic Generation Control (AGC). Scheduling plant loads for the RATA testing must often be done far in advance and can come at a high price when factoring in fuel costs. Because it can be a significant undertaking to schedule the loads for a series of RATA tests, it makes economic sense to schedule other testing also requiring unit stability concurrently with the RATA tests. One of the most important tests that fits this category is performance testing for plant capacity and/or heat rate. Many plants are now required to perform capacity and/or heat rate demonstrations on a periodic basis to support their power purchase agreements or transmission reliability requirements. But even plants without performance test requirements can benefit from gathering performance related data during RATA testing. For plants dispatched based on demonstrated heat rates, understanding the heat rate impact of operating in AGC or at partial loads is essential. Awareness of expected heat rate is also vital for plants that must nominate their fuel consumption requirements in advance. If the RATA test loads are planned correctly, performance data collected during the RATA test periods can be used not only to fulfill required demonstrations for capacity and heat rate, but also to determine the actual annual degradation (recoverable and non-recoverable) observed for the plant equipment. Test data can also be used to build or update performance forecasting tools for dispatch purposes. Depending on the complexity of the RATA testing, multiple load points may be available (from minimum to maximum load) which can provide data on fuel consumption at various loads, supporting fuel purchasing and planning requirements for the plant. This paper intends to outline the value of coordinating annual performance tests with RATA tests in terms of manpower, load scheduling and fuel consumption. This paper will also discuss a number of issues that may arise when coordinating multiple tests — which could be performed by numerous independent parties, as well as the additional benefits which can be gained by collecting adequate performance data during RATA test periods.