Flow-accelerated corrosion (FAC), also

Transcription

1 FAC and cavitation: Identification, assessment, monitoring, prevention By Dr Otakar Jonas, PE, Jonas Inc Flow-accelerated corrosion (FAC), also called erosion/corrosion, and cavitation are significant and costly damage mechanisms common to all types of utility and industrial steam cycles. There has been an increased emphasis on correcting these problems because of recent fatal accidents and costly material damage. In combined-cycle (CC) plants, thinning of pipe and damage to system components made of carbon and low-alloy steel typically occur in the feedwater and wet-steam sections of the cycle. Experts estimate that more than half of all CC units have FAC in the heat-recovery steam generator (HRSG) and elsewhere. Sufficient knowledge exists to predict and prevent these two types of damage. However, designers and plant operating staffs must be proactive to avoid it. FAC is a mass-transfer process in which the protective oxide (mostly magnetite) is removed from the steel surface by flowing water. Material wear rate depends on () steel composition, temperature, flow velocity and turbulence, (2) water and water-droplet ph, and (3) the concentrations of both oxygen and oxygen scavenger. These complex relationships are identified in Fig. Fig 2 shows the impact of piping and component geometry. Most of the above factors have strong, exponential effects on the material wear rate, as Figs 3 thorough 7 indicate. The FAC problem is most pronounced in carbon steels. In these materials, even small concentrations of chromium, molybdenum, and copper can improve FAC resistance. A survey of 38 heats of carbon steel found that, depending on the scrap composition, there could be up to 0.3% Cr, which may improve FAC resistance by up to 00-fold. Where FAC problems cannot be resolved by changing water chemistry, carbon steels often are replaced by low-alloy steels, such as P and P22 or a welddeposited overlay is used. Temperature has a pronounced effect on the FAC wear rate (Fig 4) and when a system is inspected, components in the 2-400F range get a priority. Flow velocity (Fig 5) has a strong effect, which makes wet steam systems very susceptible to FAC. Reason is that the velocity of the steam usually is much higher than that of the water. Water chemistry effects on FAC often are not well interpreted. The ph of feedwater and steam droplets must be kept above a certain threshold, which depends on the ph agent used (Fig 6) and on temperature. For ammonia and amines, their effect diminishes with temperature. For feedwater treatment with ammonia, a room-temperature ph above 9.5 is desirable. Oxygen actually is good for preventing FAC. Experience indicates that 5 ppb of oxygen in feedwater can practically stop FAC, while excessive concentration of oxygen scavengers accelerates it. In most CC units that do not have copper-alloy tubing, oxygen concentrations can be as high as 20 ppb without causing any problems. TL = F(x), FG, FT, FC, FR k c = k c = k c = k c = 0.75 Steel composition factor Water treatment factor (ph, etc) Temperature dependence factor Geometry factor Mass-transfer dependence function Thickness loss rate. Material wear rate depends on many variables including steel composition, oxygen concentration, flow velocity, temperature, etc (above) 2. Component shape impacts FAC, (right) with higher numbers in chart above signifying a stronger influence k c = 0.6 k c = 0.52 k c = 0.3 k c = 0.23 k c = 0.5 k c = 0.5 k c = 0.6 k c = 0.04 k c = 0.6 to 0.24 COMBINED CYCLE JOURNAL, Second Quarter 2004

2 ½Mo steel Carbon steel 2 Carbon steel µm Metco 33 Carbon steel µm nickel 8Cr stainless steel 3Cr stainless steel 2¼Cr-Mo steel 3 Cr-½Mo steel 4 Cr-Mo-Ni-V steel Ni-Cr-Mo-V steel Ni-Cu-Mo-Nb steel ph O 2 content 7 0 µg/kg 9.5 <5 µg/kg 7 <5 µg/kg ASTM designations A6 Gr T 2 A44 Gr B 3 A23 Gr T22 4 A23 Gr T Wear rate of various materials from erosion/corrosion in 356F water at 580 psig moving at 65.6 ft/sec is shown for three typical ph/oxygen combinations Ni-Cu-Mo-Nb Cr-½Mo (A23 Gr T2) 2¼Cr-Mo (A23 Gr T22) Carbon steel ½Mo (A6 Gr T) Temperature, F 4. Temperature effect on erosion/corrosion is greatest in F range. Data are for neutral 580-psig water with an oxygen content of less than 40 µg/kg flowing at 5 ft/sec. Exposure time is 200 hr FAC experience Though FAC control programs have been implemented in all US nuclear plants, and in many fossil-fired utility and industrial plants, major damage still occurs, as several references listed at the end of this article attest. This is particularly true at CC units, as noted earlier, generally for one or more of the following reasons: Limited experience in the design, construction, and operation of CC plants by many OEMs, architect/engineers, and owner/operators. Imperfect technical tools that is, software for quantifying the effects of temperature, oxygen scavengers, cavitation, and water chemistry on FAC. Misrepresentation of water-chemistry history and material compositions, leading to gross errors in FAC assessment. Any carbon- or low-alloy-steel component or piping system at a CC plant is a candidate for FAC. These include: Single-phase systems HRSG economizers, headers, drum liners, boiler tubes, and feedwater pipes in drums; condensate/feedwater; auxiliary feedwater, heater, and other drains; pump glands and recirculation lines. Two-phase systems low-pressure (l-p) turbine wet-steam extraction sections and pipes, glands, blade rings, casing, rotors, and disks; flashing lines to the condenser (miscellaneous drains); feedwater-heater vents, shells, and support plates; feedwater heaters; HRSG moisture separators; condenser shell and structure. Where to look for FAC HRSGs. Typical locations of FAC damage in HRSGs is shown in Fig 8. It occurs in () areas of high turbulence, such as in the transitions from vertical generating tubes to headers and drums; (2) economizers and l-p drum circuits which often operate in the peak temperature range, and (3) downcomers, particularly the lower-header areas where FAC can be combined with cavitation. Use of sodium phosphate boiler-water treatment can prevent FAC in HRSGs. However, in CC designs where the l-p boiler serves as a heater for the intermediate-pressure (i-p) and high-pressure (h-p) boilers, it cannot be used. Reason: Phosphate would concentrate in the i-p and h-p boilers and cause other problems. Feedwater piping. Most frequently, FAC damage is found in feedwater piping with the pipingcomponent geometry effect following the classification index shown in Fig 2. There have been at least three fatal accidents caused by ruptures of thinned pipes, none reported in combined cycles. Deaerators. FAC thinning of deaerator piping, partitions, and liners, and of the deaerating vessel itself in the water outlet and steam inlet areas, are experienced occasionally. Condensers. Exhaust steam leaving the l-p turbine can contain from 5 to 0% moisture and the wet-steam velocity at the exit of the last row blades is hundreds of feet per second, an ideal environment for FAC. Also, the moisture-droplet ph often is suppressed. There have been many cases of condenser-support-structure FAC, and the iron oxides produced by this process are a major impurity in condensate. Return condensate from various processes often is contaminated with organic and inorganic impurities and carbon dioxide, which reduces its ph and increases the likelihood of FAC. To avoid problems, make provision for automatic dumping of bad condensate or for condensate purification by ion exchange. 2 COMBINED CYCLE JOURNAL, Second Quarter 2004

3 Feedwater heaters and other heat exchangers. Tubes: Carbon-steel tube bundles, particularly the tube inlets, are among the components most vulnerable to FAC. Such tubes typically are designed with the minimum wall thickness necessary to support the mechanical loads because a thinner wall promotes more efficient heat transfer. Thus even a small reduction in wall thickness caused by corrosion can result in failure. FAC can occur on both interior and exterior tube surfaces. On the steam side of feedwater heaters, FAC attack depends significantly on the design and the moisture content of the steam. Keep in mind that the actual moisture content of the steam extracted from the turbine can differ from the theoretical moisture level because of drainage and other conditions that are specific to each turbine. Vessel: Thinning of the feedwater-heater pressure vessel occurs mainly at the steam and drain nozzles and where the flow of wet steam turns. This thinning is caused by direct impingement of the jet or by the deflected jet after it has struck a poorly designed impingement plate. Impingement of steam moisture has locally eroded feedwater heater shells almost to perforation in several fossil-fired units. Internals: Feedwater heaters often contain partitioned-off areas which serve a specialized heat-transfer purpose. These boxes cool the exiting drain flow or desuperheat the entering steam, and are subject to the same damage mechanism as the vessel. In addition, when there are leaks through a box wall, the secondary flows created can cause rapid damage. In drain cooling boxes, damage can occur even without leaks if there is improper control of the condensate level. Heater drains. Major problem areas include the drain lines below the feedwater heaters. They often experience problems with level control valves. However, even without valve problems, these lines frequently experience FAC because the liquid is near saturation conditions and it may flash across the level control valves. In these locations, FAC could be combined with cavitation. Downstream of flowmeters. The piping immediately downstream of flowmeters, orifices, and other restrictions has been a source of problems because of the increase in local velocity and local turbulence, and the susceptibility to cavitation. Downstream of control valves. There have been a large number of reported instances of FAC degradation, including Carbon steel Ni-Cu-Mo-Nb some significant failures, at locations downstream of control valves. Thermowells, sampling nozzles, and injection quills. These obstacles to flow can produce vortex shedding with locally high velocities leading to small areas of pipe thinning caused by FAC or cavitation. Pipe-wall thickness should be measured starting from these obstacles to about three feet downstream. How to control FAC An effective FAC control program begins with an assessment of the propensity of different plant systems and components to FAC, and also includes the use of available software with water and steam-chemistry corrections and periodic inspections. Monitoring of iron concentration around the steam cycle also is useful; elevated concentrations may indicate ongoing damage in a specific subsystem. Inspection and NDT. After conducting a theoretical evaluation of your CC unit s Rankine cycle for its propensity to FAC and cavitation attack, select several of the most susceptible components for inspection. The nondestructive examination (NDE) methods typically used include ultrasonic wall-thickness measurement and radiography of small sections of equipment and piping systems with geometries that can cause turbulence. Inspec- ½Mo (A6 Gr T) Cr-½Mo (A23 Gr T2) 2¼Cr-Mo (A23 Gr T22) Flow velocity, ft/sec 5. Flowing water increases material loss rate exponentially with flow velocity. Data are for neutral 580-psig/356F water with an oxygen content of less than 5 µg/kg. Exposure time is 200 hr (above) 6. Decreasing ph increases material wear, particularly below 9.2 (above right) 7. Oxygen content above 00 µg/ kg gives maximum steel protection in neutral water (right) COMBINED CYCLE JOURNAL, Second Quarter ½Mo (A6 Gr T) 580 psig, Cr-½Mo 356F, (A23 Gr T2) 28 ft/sec, <5 µg O 2/kg Carbon steel 0 psig, 67F, 5.25 ft/sec, 20 µg O 2/kg ph Carbon steel: 0 psig, 67F, 5.25 ft/sec Cr-½Mo (A23 Gr T2): 580 psig, 248F, 5 ft/sec ½Mo (A6 Gr T): 580 psig, 248F, 5 ft/sec Oxygen content, µg/kg

4 All: Layup corrosion, weld corrosion cracking Internal insulation and lagging Steam drum: FAC, high carryover FAC FAC, cavitation Outlet duct Stack Inlet ducts Expansion joint Expansion joint Downcomer: FAC, corrosion Manway Evaporator: Superheater: low-cycle fatigue, stress corrosion pitting, hydrogen damage Integral structural steel cracking, exfoliation, creep, low-cycle fatigue 8. Typical locations of FAC and other types of damage found in HRSGs reveal that problems generally occur in regions of boiler that experience high turbulence (above) 9. Sharp reduction in static pressure causes the production of vapor bubbles which translates to cavitation attack in components that experience a high pressure drop (right) Inlet (p ) Static pressure p Flow Orifice Vapor pressure (p v ) Economizer: FAC, pitting, corrosion p vc Vena contracta p vc Outlet (p 2 ) p 2 tion grids have been developed to facilitate the ultrasonic wall-thickness measurements of typical geometrical elements. Often neglected are piping areas downstream of flowmeters, thermowells, and injection quills, where both FAC and cavitation can be active. Keep in mind that vortices generated by the flow obstruction can travel for many feet. Many components can be inspected during operation using x-ray techniques. However, if there is an urgency for safety or other reasons to verify that FAC and/or cavitation damage is not of immediate concern, and system shutdown is not possible, a successful hydro test of at least % overpressure offers sufficient proof. Software solutions. At least three software packages are available for assessment of wall thinning caused by FAC. These have been developed by the Electric Power Research Institute (EPRI), Palo Alto, Calif; Electricite de France (EdF), Paris; and Siemens AG, Erlangen, Germany. Results of predictions of FAC with the use of the software have been mixed, some realistic, some very wrong. The main reasons for the wrong predictions include poor representation of water chemistry in the software (at-temperature ph, concentration of oxygen scavenger, concentration of oxygen, and chemistry of water droplets), oversimplification of the waterchemistry history, and a failure to use the actual steel composition. Cavitation Cavitation is a repeated generation and collapse of bubbles (or cavities) in a liquid because of local static-pressure fluctuations, usually caused by changes in flow velocity. If the pressure of a flowing liquid decreases to below its vapor pressure for example, because of significant increases to the local flow velocity then vapor bubbles are nucleated. The bubbles are transported downstream from the flow disturbance, and when they reach a region of higher pressure, they collapse suddenly and may erode any solid material in their vicinity. The phenomenon is predominantly mechanical in nature, but corrosive environments do accelerate the damage. Shock-wave emission and jet formation caused by the collapse of individual cavities are the fundamental factors responsible for cavitation. Tests indicate that the fatigue endurance limit of the material is the primary parameter that controls cavitation. Damage occurs to the surface of the component, just downstream from the cavitation source. Cavitation bubbles are reabsorbed within five to 0 pipe diameters. Barring any obstructions or changes in direction, reabsorption is accomplished causing further damage. In CC plants, cavitation damage can occur in pumps, valves, and piping. The effect of flow on pressure is illustrated in Fig 9 for flow through an orifice. Note that in the 4 COMBINED CYCLE JOURNAL, Second Quarter 2004

5 Checklist helps identify FAC, cavitation before they become serious problems There s little reason for a plant manager to be surprised that his or her plant is experiencing FAC and/or cavitation damage. The majority of combined-cycle (CC) facilities were designed and built to meet the needs of the competitive generation market. The large number of plants ordered in the timeframe stretched the personnel and material resources of the entire industry. Designs and construction work often did not get the rigorous review and oversight that had become a tradition in the generation industry. Mistakes were made. Also, many asset owners thought CC plants so simple typically, just a matter of hooking up modules on a slab of concrete and connecting gas and electric lines that the detailed procedures used for coal-fired and nuclear plants didn t apply. Another mistake, as plant managers know well. One thing for certain, the industry has a wealth of knowledge of FAC and cavitation as the many references at the end of this article attest. This information offers a competitive advantage to the plant manger who takes the time to do the appropriate eavaluations. It helps identify areas where FAC and cavitation already exist and where they are likely to occur, what corrective action is warranted, and what type of monitoring program will enable you to avoid forced outages and the possibility of life-threatening damage. Assessment of the propensity of individual systems and components to FAC and cavitation begins with a comprehensive plant walkdown paying particular attention of areas of attack identified in the adjacent text. Your evaluation should consider the combined effects of component geometry, flow velocity, water and steam properties, material composition, water chemistry, and operating experience. Consider these objectives for your evaluation: Find and select components to be inspected. Interpret NDE results. Identify root causes of wall thinning. Determine inspection interval and safety margin. Determine effects on cycle iron transport. Recommend engineering solutions. Project tasks to consider include: Preliminary assessment (drawings, flow velocities, cycle design, experience, leaks). Component details and actual installation (walkdown, steel composition, history). Final system and/or component description and operating and inspection/maintenance history. Water-treatment history and local chemistry. Computer modeling, calculation of erosion/ corrosion rates, contributions of individual effects. Monitor cavitation noises and the rate of wallthinning. Finally, document your conclusions and recommendations in a formal report for executive review and implement engineering solutions approved by the asset owner. Regular follow-up inspections of susceptible systems and components are recommended. flow region immediately downstream of the orifice, where velocity is highest, the static pressure drops below the vapor pressure and steam bubbles form. The change in static pressure, Δp stat, can be measured or calculated from the measured or estimated maximum velocity in individual components using the relationship, Δp stat = 0.5 ρ V 2, here ρ is the water density and V is the local flow velocity. This flow-velocity effect is also called dynamic pressure or velocity head. Cavitation, thoroughly researched in the 960s and 970s, is a damage mechanism well known in the marine industry and among pump manufacturers. In steam power systems, it has been mostly a problem with valves and boiler feed pumps which can be damaged within a few minutes of operation when deprived of proper suction head. Such head normally is provided by the deaerator, typically located more than 30 ft above the pump. Problems in the 990s at nuclear units prompted EPRI to Change in static pressure, psi Flow velocity, ft/sec 0. Relationship between flow velocity and the reduction of static pressure can be used to estimate the susceptibility to cavitation (left). Susceptibility to cavitation of various materials used in powerplant systems illustrates relative resistance of stainless steel (right) Rate of weight loss, mg/hr Brass Mild steel High-tensile brass Gunmetal Monel Stainless steel Test time, hr COMBINED CYCLE JOURNAL, Second Quarter

6 include cavitation effects in its computer. Unlike FAC, which is mostly confined to carbon-steel components, cavitation can attack any material, including stainless steels. Some piping and other component damage that had been attributed to FAC actually was caused by cavitation or possibly by an interaction of cavitation and FAC, because the flow-velocity and turbulence effects are similar and the surface damage often looks the same. Any system handling water at near saturation conditions is susceptible to cavitation damage. For example, the l-p section of condensate/feedwater systems, such as the suction of booster and boiler feed pumps, can be close to saturation. Saturation conditions can be approached by locally increasing flow velocity around obstacles. Also, by reducing the static pressure of the water in turbulent regions, or by increasing water temperature. Components that have been damaged by cavitation include pipes, valves, orifices, pumps, feedwater-heater drains, and other feedwater and auxiliary water components. For example: A feedwater pipe, believed to have been thinned by cavitation after a quill, ruptured in a paper mill. Feedwater approached the saturation conditions because a leaking feedwater heater increased the water temperature and the excessive pressure drop caused by various piping-system components between the feed pump and the drum reduced the static pressure. Management control for preventing cavitation damage is similar to that for FAC. First, conduct a preliminary evaluation of all cycle systems, making sure to include an estimate of the component pressure in relation to the saturation pressure under all modes of operation. Next, schedule a walkdown of all the systems, paying particular attention to the noises generated by cavitation. Finally, inspect for thinning of selected susceptible components. Where possible, the actual pressures, temperatures, and flow velocities should be measured or otherwise determined and used in the cavitation evaluation. When susceptible components are identified, consider installing acoustic emission monitoring instrumentation to track cavitation long-term. Typical areas where cavitation may occur include: HRSG downcomers, particularly near the lower headers and in economizer-to-drum feedwater pipes; sections of pipe after thermowells and similar obstructions; control valves; condensate, booster, and feedwater pumps; and pump suction pipes. As a guide to estimating susceptibility to cavitation, use Fig 2, which was developed for FAC, and include pressure and temperature information. Fig 0 presents the relationship between the reduction of static pressure and flow velocity, which also can be used to estimate susceptibility to cavitation. Material properties. Unlike FAC, all materials used in steam-cycle water systems are susceptible to cavitation damage (Fig ). The material property which correlates best with the susceptibility to cavitation is the fatigue limit. However, it is not clear whether, for various aqueous environments, the cavitation correlates with air-fatigue or corrosion-fatigue properties. Water chemistry probably does not play a major role in the cavitation damage found in steam cycles. However, effects of concentrated impurities have been measured and have confirmed that a corrosive environment can accelerate cavitation. While cavitation is most often caused by the collapse of steam bubbles, it can also be caused by gases, such as nitrogen and oxygen, and volatile chemicals coming out of solution in water and subsequently redissolving. Recommendations Every CC and cogeneration plant should have a formal program for preventing FAC and cavitation, starting with an early design review that considers all the parameters influencing FAC described in Fig. Where organic water-treatment chemicals such as amines, dispersants, and oxygen scavengers are used, evaluate their effects and the effects of their decomposition products. When using any FAC software, play special attention to the representation of ph at temperature, ph of water droplets, concentration of the oxygen scavenger, and the concentration of oxygen. Inspect piping downstream of all orifices, thermowells, sampling nozzles and chemical injection quills, and leaking valves. Also check HRSG blowdown lines, downcomers, headers, drum liners, feedwater pipes, saturated steam pipes, steam separation systems, turbine extraction pipes and extraction valves, feedwater heater drain valves and shells, feedwater piping, condensers, and boiler-feed-pump recirculation lines. Select a reliable and accurate method for identifying wall thinning. Your best options: ultrasonic wall-thickness measurements, x-ray of piping and other components, pulsed eddy-current technique, and the magneto-strictive sensor technique. Finally, remember that cavitation can be detected on-line by listening to the noise produced by the collapsing steam or gas bubbles using acoustic microphones or by acoustic emission instrumentation. It is important to establish critical locations for periodic long-term monitoring. Continuous in-line monitoring is an alternative. CCJ References Section I: Erosion/corrosion. Low-Temperature Corrosion Problems in Fossil Power Plants State of Knowledge Report, TR , Electric Power Research Institute, December O Jonas and L Machemer, Tight Control of Cycle Chemistry Key to Successful Commissioning, Combined Cycle Journal, First Quarter O Jonas, Safety Issues in Fossil Utility and Industrial Steam Systems, Materials Performance, May 200. See also steamcycle.com/safety_issues_pdf.htm 4. O Jonas, Erosion-Corrosion of PWR Feedwater Piping Survey of Experience, Design, Water Chemistry, and Materials, NUREG/CR-549, ANL-88-23, US Nuclear Regulatory Commission, March G Cragnolino, et al, Review of Erosion-Corrosion in Single-Phase Flows, NUREG/CR-556, ANL-88-25, US Nuclear Regulatory Commission, April S Bush, The Effects of Erosion-Corrosion on Power Plant Piping, 6 COMBINED CYCLE JOURNAL, Second Quarter 2004

7 Proceedings of the 59th General Meeting of the National Board of Boiler & Pressure Vessel Inspectors, Volume VII, No., May Flow-Accelerated Corrosion in Power Plants, TR-066, Electric Power Research Institute, V K Chexal, et al, Recommendations for an Effective Flow- Accelerated Corrosion Program, NSAC-202, Electric Power Research Institute, November Guidelines for Controlling Flow-Accelerated Corrosion in Fossil Plants, TR-08859, Electric Power Research Institute, June 998 Section II: Effects of water chemistry on erosion-corrosion 0. O Jonas, Steam, Chemistry, and Corrosion in the Phase Transition Zone of Steam Turbines, TR-0884, Electric Power Research Institute, February 999. O Jonas, Use of Organic Water Treatment Chemicals, VGB Conference, Organische Konditionierungs-und Sauerstoffbindemittel (Lahnstein, Germany), O Jonas, Controlling Oxygen in Steam Generating Systems, Power, May O Jonas, New Oxygen Scavengers, Jonas Inc, O Jonas, Reduction of Feedwater Iron by Minimizing Oxygen Scavengers, Jonas Inc, October 997 Section III: Inspection methods and codes, erosion-corrosion 5. NDE of Ferritic Piping for Erosion-Corrosion, NP-540, Electric Power Research Institute, September Assessment of the Pulsed Eddy Current Technique: Detecting Flow-Accelerated Corrosion in Feedwater Piping, RS-0946, Electric Power Research Institute, January Assessment of Magnetostrictive Sensor Technique: Detecting Flow-Accelerated Corrosion in Feedwater Piping (Revision ), RS R, Electric Power Research Institute, February O Jonas, Steam Generation in Corrosion Tests and Standards, ASTM MNL 20, June Requirements for Examination of Class, 2, and 3 Systems for Detection of Pipe Wall Thinning Due to Single-Phase Flow-Accelerated Corrosion, ASME Boiler & Pressure Vessel Code (Section XI, Subsection IWH), to be published 20. Examination Requirements for Pipe Wall Thinning Due to Single-Phase Erosion and Corrosion, ASME Boiler & Pressure Vessel Code (Section XI), Case N-480 Section IV: Other references on erosion-corrosion 2. O Jonas, Alert: Erosion-Corrosion of Feedwater and Wet Steam Piping. Power, February 996. See also plant_alert.htm 22. O Jonas, Control Erosion-Corrosion of Steels in Wet Steam, Power, March 985. See also erosion_corrosion 23. H G Heitmann and W Kastner, Erosion-Corrosion in Water- Steam Cycles Causes and Countermeasures, VGB Kraftwerkstechnik 62, March W Kastner, et al, Calculation Code for Erosion-Corrosion Induced Wall Thinning in Piping Systems, Nuclear Engineering and Design 9, L Goyette and G Zysk, Material Sampling in Erosion-Corrosion Programs, Codes and Standards in a Global Environment (PVP Vol 259), American Society of Mechanical Engineers, 993 Section V: Cavitation 26. R Knapp, J Daily, and F Hammitt, Cavitation, McGraw Hill Book Company, New York, I Pearsall, Cavitation, M&B Monograph ME/0, Mills & Boon, London, J Tullis, Choking and Super Cavitating Valves, Journal of the Hydraulic Division, American Society of Civil Engineers, December C Preece, Cavitation Erosion, Treatise on Materials Science and Technology (Vol 6), Academic Press Inc, New York, R Mahini, B Chexal, and J Horowitz, Developing Predictive Models for Cavitation Erosion, Codes and Standards in a Global Environment (PVP Vol 259), American Society of Mechanical Engineers, A Method to Predict Cavitation and the Extent of Damage in Power Plant Piping, TR-0298 and TR-0298-T2, Electric Power Research Institute, J P Tullis, Cavitation Guide for Control Valves, NUREG/CR- 603, US Nuclear Regulatory Commission, April Guidelines for Prevention of Cavitation in Centrifugal Feed Pumps, GS-6398, Electric Power Research Institute, A Bruthman, Feedwater Heater Design Standards and Practices, Proceedings of the Feedwater Heater Workshop, Electric Power Research Institute, July 979 Panel Discussions of Special Interest to HRSG USERS at the upcoming INTERNATIONAL WATER CONFERENCE Pittsburgh October 7-2 Current Ideas for Chemistry Control and Operation of HRSGs Participants include Dave Daniels, Irv Cotton, and Luis Carvalho Pros and Cons of Amine Use in Industrial and Utility Power Plants Participants include Mike Rootham, Jim Bellows, Bill Moore, and Albert Bursik Other Presentations of Interest to HRSG Users Monitoring and control in steam generation cycles New concepts in EDI design Biofouling control in cooling systems Use of heat-tolerant RO membranes for condensate polishing LISTEN LEARN PARTICIPATE Complete program at (click on brochure link) COMBINED CYCLE JOURNAL, Second Quarter