In order to improve solid particle erosion (SPE) resistance for steam turbine blades and nozzles, in corporation with Kobe Steel, Ltd., evaluation of hard coatings of TiN and TiAlN deposited by the Arc Ion Plating (AIP ® ) process was performed to verify applicability to an actual steam turbine. The results of high-temperature steam oxidation tests and room-temperature sand erosion tests showed that the TiAlN coating had high-temperature stability superior to that of the TiN coating, and erosion resistance far superior to that in the case of the conventional CrC thermal spray coating and boronizing treatment. High-temperature fatigue and creep tests showed that the characteristic strength of the blade material with the TiAlN coating was equal or superior to that of the base blade material. On the basis of the results of comprehensive evaluation, it was confirmed that the TiAlN hard coating has excellent applicability to an actual steam turbine and it was successfully applied to steam turbine blades of power plants in Japan.

High cycle fatigue (HCF) is the main cause of failure in rotating machinery especially in aircraft engines which results in the loss of human life as well as billions of dollars. More than 60 percent of aircraft accidents are related to High cycle fatigue. Major reason for HCF is vibratory stresses induced in the blades at resonance. Damping is needed to avoid vibratory stresses to reach the failure level. High speed rotating machinery has to pass through the resonance in order to reach the operational speed and chances of failure are high at resonance level. It is therefore required to suppress the vibrations at resonance level to avoid any damage to the structure. Application of coating to suppress vibrations is a current area of research. Various types of coatings have been studied recently. This includes plasma graded coatings, viscoelastic dampers, piezoelectric material damping, and magnetomechanical damping. In this research, the phenomenon of damping using a coating of nickel alloy on a steel beam is studied experimentally and numerically to reduce vibratory stresses by enhancing damping characteristics to avoid aircraft engine and rotating machinery failure. For this purpose, uncoated and nickel alloy coated steel beams are fabricated. The coating procedure was performed using plasma arc method. The beams were then mounted in a cantilevered position and bump and vibration shaker tests were conducted to determine the natural frequencies and mode shapes. One of the most important parameter to measure the damping of a system is the damping ratio. In order to determine the damping ratio, vibration analyzer mode was adjusted in time domain and beam was excited by using a hammer. The vibration analyzer showed the vibration decay as a function of time. Using that decay, damping ratio was calculated by using logarithmic decrement method. In order to investigate and compare the damping characteristics of un-coated and coated beams, forced response method was employed. In this method, beams were excited at 1st and 2nd bending mode natural frequencies using vibration shaker. Results were very encouraging and showed a significant improvement in damping characteristics. The experimental results were then endorsed by numerical results which were achieved by performing modal and forced response analysis using finite element analysis techniques.

The condenser performance benefits afforded by dropwise condensation have long been unattainable in steam cycle power plant condensers due to the unavailability of durable and long lasting wetting inhibiting surface treatments. However, recent work in superhydrophobic coating technology shows promise that durable coatings appropriate for use on condenser tubes in steam cycle power generation systems may soon become a reality. This work presents a nano-scale, vapor phase deposited superhydrophobic coating with improved durability comprised of several layers of rough alumina nano-particles and catalyzed silica with a finishing layer of perfluorinated silane. This coating was applied to solid, hemi-cylindrical test surfaces fabricated from several common condenser tube materials used in power generation system condensers: Titanium, Admiralty brass, Cupronickel, and Sea Cure stainless steel condenser tube materials as well as 304 stainless steel stock. The development evolution of the coating and its effect on condensation behavior on the above materials are presented. Results show that the performance enhancement, measured in rate of heat transfer spikes corresponding to condensate roll-off events, was best for the titanium surface which produced 64% more events than the next most active material when coated using the most durable surface treatment tested in this work.

Solar water heaters (SWHs) are a well-established renewable energy technology that have been widely adopted around the world. In this study we have significantly improved the Evacuated Tube solar Collectors (ETCs) by utilizing the “dry-drawable” Carbon Nanotube (CNT) sheet coatings to increase the solar energy absorption and Phase Change Materials (PCMs) to increase the heat accumulation for application in solar water heaters. The proposed solar collector utilizes a phase change material namely Octadecane paraffin, with melting temperatures of 28°C which is categorized as non-toxic with long-term chemical stability PCM. As PCMs particularly in powder form may not be effective by itself due to the poor heat transfer rate, low thermal diffusivity and thermal conductivity, by combining CNT layers with the high thermal diffusivity and thermal conductivity compare to phase change materials, we are able to overcome the shortcomings of PCMs and design an innovative and efficient solar water heater. With the current technology, we can provide a near ideal black body surface, absorbing a maximum of 98%, between 600–1100 nm, of solar light striking the surface, and providing additional spectral absorption which improves the performance of the solar heater. Applying CNT sheets in conjunction with PCM enables heat storage directly on the collector for a more constant output, even on a cloudy day and prolonged output of heat at night.

As part of the design basis of any piping system utilized to convey materials, pipe supports are required to ensure those pipes remain in their designed locations and do not overly expand or move due to sustained or occasional loads. These loads represent the total forces and moments in the piping components and as a result create stresses that affect the life of the component. Proper design and maintenance of these supports per the applicable codes and standards provide a reasonable life expectancy for the piping systems. This presentation will review the various codes and standards utilized for both pipe support design and maintenance. A high level overview of what information must be obtained to perform an analysis and meet ASME B31.1 Power Piping code requirements when modifying piping systems will be presented. Specific inputs to system design and computational software including material properties, stress intensification factors (SIF), thicknesses and tolerances, pressures, temperatures, insulation, coatings, the occasional loads, etc. will be discussed. Guidelines will be discussed for determining what piping modifications warrant a full pipe stress analysis to be performed. Recommendations for pipe support maintenance inspections will be provided to facilitate increased life expectancies of subject piping systems. The mandatory requirements of ASME B31.1 Chapter VII will be discussed, as well as recommendations from the non-mandatory appendix. Implementing maintenance programs at existing facilities will be discussed. Step by step recommendations for how to apply these guidelines within a long-term life extension program will be given. Tolerances and general guidelines associated with these programs will also be discussed. Finally, common pipe support failures, what they can affect, and how to look for early indicators of fatigue or failure will be covered.

Restriction on water consumption is becoming an increasing problem for the power generation industry. As an alternative both to once-through cooling and to surface condenser/wet-cooling tower combination, utility companies and equipment manufacturers are considering, and even implementing, air-cooled condenser (ACC). However, the industry is quite reluctant to switch over to ACC for three important reasons: (a) lower power output, (b) higher capital cost, and (c) larger physical foot-print, all because of the same reason — it is not as efficient to transfer heat from condensing steam to air as it is to transfer to water. In other words, overall thermal resistance from condensing steam to the ambient air is significantly higher than to cooling water. To get a clear and full understanding of the heat transfer process occur in air-cooling condenser, Detailed mathematical equations were derived to model the heat transfer process through the fined-tubes of the ACC. The total thermal resistance model was analyzed and investigated to identify the design components with highest affect in the process. The paper proposes a viable cooling system based on novel heat pipe technology which addresses these problems. This technology employs boiling as the means to store and transfer heat energy. A detailed mathematical set of equations was derived to model the heat pipe thermal resistance. A comparison of the heat transfer performances of the ACC technology and the proposed method is presented. The proposed cooling system suggests a solution for each of the three components of the thermal resistance, the super-hydrophobic coating of the steam ducts internal surfaces increased the condensing heat transfer rate by an order of magnitude, the proposed design of the heat pipes improved the external heat transfer, and the installation mechanism improves the fin efficiency by eliminating the contact resistance between steam duct and the heat pipe.

Efficient decontamination technologies are needed for both decommissioning and safe operation of nuclear power plants. Up to now room walls as well as other structures contaminated with radionuclides have mainly been decontaminated using mechanical removal processes. The aim of such processes is to remove the wall surfaces to a contaminated depth of several millimeters. This generates a large amount of dust, which can lead to secondary contamination, and is associated with high personnel and/or technical expenditures. Advances in high-power lasers allow the use of laser radiation to remove contaminated layers. These layers are melted to depths of up to 5 mm by a laser beam. Most of the radionuclides are dissolved in the melt. The molten layer is detached from the wall by pulsed compressed air jets and solidifies to form small particles in which the radionuclides are fixed. The particles are then suctioned up by means of a negative pressure. The advantages of the innovative process are based on minimal dust formation and force-free coupling of the laser unit and the wall, allowing a very lightweight and flexible overall design of the system. Because the laser processes can easily be automated and controlled by remote control, the personnel exposure time within contamination areas can be minimized in an efficient manner. The present report describes the development and testing of a laser decontamination system for the removal of radioactively contaminated concrete wall layers. A diode laser with a power of 10 kW is used as the radiation source. The laser energy is delivered via a fiber optic cable up to 100 m in length to the laser tool, which is situated on a specially designed autonomous manipulator. The manipulator moves over the wall surface to be processed by means of pneumatic suction plates. For velocities of 400 mm/min and a removal depth of 2 to 3 mm, a removal rate of 1.2 m 2 per hour could be achieved. The laser focus area on the processed concrete surface is 10 mm × 45 mm. Using today’s commercially available lasers with powers of > 50 kW, removal rates higher than 6 m 2 per hour are possible. Development efforts revolving around the presented technology are focused on two main areas which can be understood as spinoffs of the present research: increasing the removal rate using more powerful lasers and adapting the technology for use in decontamination of chemically contaminated surfaces, e.g., for pollutant-free stripping of PCB-containing wall coatings.

Heat dissipation in transportation of nuclear materials is strongly dependant of radiation exchanges from the external faces of the protective caisson, surrounding nuclear material packaging. However, the thermo-optical properties of the external paint, total hemispheric emissivity and solar absorbance factor, are degraded during transportations. This degradation is due to the dirtying, and does not permit to fully use high emissive and low absorbent paint. Commercial “easy-to-clean” coating has been tested on epoxy-based paint. This transparent varnish is hydrophobic and release dirt out of the treated surface. Laboratory dirtying tests with “carbon black” solution simulate penalizing dirt exposure. And different measurements (colour lightness, total hemispheric emissivity and solar absorbance factor), made before and after dirtying and cleaning steps, permit to quantify the “easy-to-clean” property of this coating. The commercial coating tested in this study does not modify the initial thermo-optical properties of the paint, and is very efficient to maintain them after dirtying and simple cleaning steps. So, the addition of this coating could be an easy way to improve the heat release during nuclear material transportations. Dirt exposure test on real caisson are in progress to confirm the conclusions of this laboratory study.

Blade erosion is a serious problem in steam turbines and reduces the life of turbine, requiring periodic maintenance. A fundamental experiment is being performed to evaluate effects of certain control parameters on the droplet formation process and distribution of the shed droplets sizes. Three blade coatings include Epoxy, Teflon®, Viton®, three trailing edge geometries and a new and innovative trailing edge effect are to be experimentally studied. Measurements are to be made in a simulated stationary cascade utilizing real turbine components. The condensed liquid film and the large droplets formed on the three coated blades and one original finish blade will be optically measured. A typical cascade is modeled using Volume of Fluid with different surface properties used to model the formation and breakup of a thin water layer into droplets. Droplet distributions for the various conditions will be compared and the best surface finish and configurations will be identified. Most importantly, the reason for a successful configuration will be given, based on the measurement results.

Low cost, reliable and accurate real time measurement of individual tube condenser cooling water flow rate, cooling water outlet temperature and tube side fouling for the purpose of condenser performance monitoring and troubleshooting is presented. The importance and the effects of these parameters on condenser performance are well understood and periodically estimated using indirect measurements such as dye dilution testing to represent average tube circulating water velocities, distributed temperature sensors in waterboxes and differential pressure measurements between inlet and outlet waterboxes. These measurements, while useful, are not always effective to identify performance inhibiting issues quickly and accurately. This paper presents a cooperative study on the effects of circulating water flow and fouling and protective tube coatings for the purpose of condenser performance and monitoring improvement. The objective of the study was to evaluate new Circulating Water Flow and Fouling (CWFF) instrumentation [1], [2], [3] to evaluate impact of tube coating [4] on heat transfer and biofouling, and to examine the effect of other variables on on-going Microbiologically Influenced Corrosion (MIC) attack on the SS condenser tubes. However, in addition to providing useful information on the coated tubes, the study unveiled a number of other condenser performance related issues. Real-time in-situ circulating water flow and fouling data over an entire 1-year period will be presented that: • Correlates real-time flow measurements to fouling as it occurs; • Assists in the evaluation of different circulating water pump capacities and configurations; • Identifies flow stratification within the water box and identifies whether or not waterboxes are filled; • Evaluates the heat transfer coefficient differences between the coated and uncoated tubes; • Identifies other performance related findings.

Since the inception of the cyclone style boiler, industry has become accustomed to performing routine maintenance during every scheduled shutdown occurring 12 months to 18 months between cycles. These maintenance cycles are influenced by service factor, loading and the type design. The same problems exist in both the standard and super critical cyclones; severe deterioration of refractory and the anchoring pin studs. This paper focuses on one type of refractory failure mechanism caused by the anchoring pin studs. Most operators have found that the most effective means of applying refractory in this type situation is to “ram” the refractory in and around the anchoring pin studs thus creating a dense lining with maximum integrity. Coupled with proper application of anchoring pin studs and a special designed coating, typical volumetric expansion of the pin studs from corrosion attack and oxidation is eliminated thus extending the life of the refractory. This mechanism is discussed along with the results of the coating performance as it relates to extreme heat oxidation and thermal cycling in laboratory tests. A protective coating was developed using a nano-cored thermal spray wire technology that produces a uniform, adherent protective layer against high temperature corrosion and oxidation. The coating yields similar thermal conductivity as a bare stud thus experiencing excellent thermal cycle performance. This specially designed thermal spray coating is applied to standard 430 stainless steel pin studs thus providing the necessary barrier against aggressive high temperature environments while maintaining excellent heat conductivity. The coating has a high amount of tungsten (40+%) in a nickel matrix with greatly reduced oxides at the substrate and throughout the coating. With these attributes for the anchoring pin studs in mind, a newly designed stud was evaluated in heat oxidation tests up to 2000°F and thermal cycling test and compared to 430 stainless steel, chromized and Alloy 625. The new stud out-performed all others even in the as-welded condition. Further corrosion testing in ferric chloride (ASTM G48) showed them to be superior to Alloy 72 and Alloy 625 in the thermal spray and welded condition. Proper welding equipment and welding techniques are also discussed since weld continuity impacts overall performance of anchoring pin studs with refractory linings. A major test site will be examined in the spring of 2004 for it’s full effectiveness in service and will be documented in order that all data retrieved would be available to the entire industry.

In order to promote high efficiency combined with high power output, reliability, and availability, Siemens advanced gas turbines are equipped with state-of-the-art turbine blades and hot gas path parts. These parts embody the latest developments in base materials (single crystal and directionally solidified), as well as complex cooling arrangements (round and shaped holes) and coating systems. A modern gas turbine blade (or other hot gas path part) is a duplex component consisting of base material and coating system. Planned recoating and repair intervals are established as part of the blade design. Advanced repair technologies are essential to allow cost-effective refurbishing while maintaining high reliability. This paper gives an overview of the operating experience and key technologies used to repair these parts.

In some aging geothermal steam turbines, the increased steam consumption is found out due to time deterioration of the turbine parts, mainly caused by erosion, corrosion damages or deposits of impurities on the steam paths. Furthermore the heavy damage due to stress corrosion cracking or corrosion fatigue damage, etc. are observed on rotors, blades and other parts and components. On the other hand in other units, the turbine output capacity decreases according to aging decrease of geothermal well pressure, that is, inlet steam pressure of turbine. Under these circumstances, upgrading and life extension are required for reliability and performance on geothermal steam turbines, particularly the existing ones. And as the effective utilization of geothermal energy is important from the viewpoint of decreasing carbon dioxide on environment problem, these technologies can, needless to say be applied to new geothermal projects as well as the existing ones. This paper describes development and application of advanced steam path design such as nozzle and blade for improving reliability and performance, and of advanced rotor design and material including overlay coating technology for improving reliability and extending life. And also it describes uprating of the existing units in opposition to aged decreasing in the inlet steam pressure.

The HEAT™ (High Efficiency Advanced Technology) steam turbine utilizes high reaction technology [1], which is significantly influenced by the effectiveness of sealing between the stages. The thermal-mechanical analysis based clearance design and the combination of labyrinth sealing with abradable coatings offer an effective solution to minimize bucket and nozzle tip leakage through transient and steady state operation of the turbine. The aim of this paper is to describe the clearance design process and the development of abradable-labyrinth seal configurations. The paper describes extensive testing and detailed analysis conducted to evaluate seal properties and behaviors. Properties investigated included corrosion, erosion and in particular, rub characteristics. Rub behavior is investigated in a high temperature, high speed test apparatus designed to simulate clearance changes during transient periods of start-up, shutdown and hot re-start which often result in interference between the sealing components. This paper will discuss the method to predict differential rotor to stator movements and the resulting abradable incursion during the various operating transients. The seal tooth to coating contact is then simulated with component testing for multiple incursion modes (i.e. radial, axial and a combination of the two) and rates. The discussion will also include the application of the clearance design and sealing technology to a reaction type steam turbine.

In early 2005, the 4-unit, 1200 MW Cottonwood Energy facility on the Sabine River in Deweyville, TX experienced a sudden increase in condenser tube failures and eddy current pit indications. Metallurgical analysis of failed tube specimens revealed the presence of a thin, hard manganese-rich coating, with intense pits propagating at breaks in the deposit. Successful mitigation of manganese-induced pitting and repassivation of the condenser tubes requires that the surface and pits first be thoroughly cleaned prior to implementing a manganese deposit control program. This paper reviews the successful cleaning process developed and implemented by Cottonwood Energy to remove manganese deposits from four stainless steel surface condensers. The cleaning procedure employed several novel features to ensure complete manganese removal, minimize environmental impact, reduce costs, control attack on the base tube metal, and ensure personnel safety. The paper also includes a discussion of corrective actions taken to prevent re-occurrence.

The evolution of industrial gas turbines has been a driving factor in the advancement of repair techniques for industrial gas turbine components. Turbine vane segments (also known as stationary blades, non-rotational airfoils, or nozzles) are among the many components that have been a focus for repair development. Due to increasing engine efficiencies, the design of gas turbine vane segments continues to become progressively more complex. Neoteric vanes are cast of highly developed superalloys, have complex cooling designs, and are coated with the latest generation coating systems which utilize advanced oxidation resistant bondcoatings combined with thermal barrier coatings. While advanced technologies enable these vanes to operate at the extreme hot gas path running temperatures of today’s engines, they also significantly increase the level of technology required to successfully repair them. The ability to repair these components is essential to minimize the operators’ life cycle cost of the gas turbine. Recoating, reestablishing of critical cooling, dimensional restoration, along with surface and structural restoration using high strength weld and braze techniques are essential for these vanes. Conventional and advanced repair techniques are key elements in the continuing evolution of industrial gas turbine component repair development. This paper will focus on a variety of Siemens’ technical competencies applied during the restoration of service run vane segments for the turbine section of a gas turbine. These repair competencies and technology/service options include: • Dimensional restoration techniques utilizing hot and cold straightening; • Utilization of refurbished blade rings for completed roll-in/roll-out exchanges; • Coupon repair techniques; • Braze restoration of cracks; • Laser etching; • Strain tolerant coatings; • Future technologies under development.