Handling Nine

7/28/2019 Handling Nine

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Handling Nine-Chrome Steel in HRSGs

Steam-Plant Industry Wrestles with Increased Use of P91/T91 and Other Advanced Alloys

By Robert Swanekamp, P.E., Contributing Editor

Nine-percent chrome-moly steels (9Cr-1Mo) have been used successfully in US fossil boilers as

far back as the 1980s. Early pioneers included Tennessee Valley Authority, Dayton Power &Light Co, Appalachian Power Co, and Hawaiian Electric Co Inc. In recent years, the alloy(known as P91 in piping applications and T91 for tubing) also has been applied in large heat-recovery steam generators (HRSGs), in order to reduce thermal fatigue and creep damage inmain-steam piping and superheaters.

However, HRSG users generally haveexperienced more trouble with the alloy than their counterparts in the fossil-boiler sectorhave. Combined-cycle plants have been hit with problems in the fabrication, construction, andrepair of P91/T91 components. In fact, HRSG users have experienced failures in dissimilarmetal welds and transition areas in less than 1,000 operating hours, and failures caused bypoor weld geometry or inappropriate heat treatment in less than 5,000 operating hours.

Primer on P91

The history of P91/T91 began in the late 1970s, when high-chrome alloys (9 percent to 12percent Cr) were being studied by the U.S. government and Combustion Engineering (nowAlstom) at the Oak Ridge National Laboratory. Researchers were trying to develop improvedsteels for the Liquid Metal Fast Breeder Reactor program. While the fast breeder reactorprogram in the United States never took off, the groundbreaking metallurgical work certainlydid. Note: Oak Ridge continues its advanced-alloy research today, developing new structuraland cladding material for so-called Generation IV reactors which include thermal and fastwater-cooled, gas-cooled, and liquid-metal-cooled Fast Reactors. Other efforts hope to developnickel-based alloys for ultra-supercritical coal plants (Figure 1).

Click here to enlarge imageFigure 1. Metallurgical advances have enabledthe development of more efficient steam

plants. Application of ultra-supercritical steamconditions in the next generation of fossilstation likely will require the use of expensive,nickel-based alloys. Graph courtesy of AlstomPower Inc

The researchers in the 1970s found that 9Cr-1Mo steels possessed lower thermal expansion,higher thermal conductivity, and improved oxidation resistance, compared to traditional powerplant steels such as 2.25Cr-1Mo ferritic steel and 300-series austenitic stainless steels.


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These enhanced properties, the power industry quickly learned, would enable steam-plantcomponents to be manufactured with thinner walls, thus they would minimize thermallyinduced stresses. With the addition of niobium, vanadium, and nitrogen, the standard 9Cr-1Mo (ASTM P9/T9) also exhibited a substantial increase in creep-rupture strength, comparedto traditional steels, thus giving birth to what we know today as modified 9Cr-1Mo.

Modified 9Cr-1Mo was certified in the 1980s as ASTM A213 Grade T91 for tubing and ASTMA/Sa 335 Grade P91 for headers and piping. Note that while piping and tubing applications aresimilar, there are subtle differences. In piping, the metal temperature will never exceed steamtemperature, because steam is the source of heat. Thermal energy flows from the centerlineof the pipe to the pipe"s outside wall. In a fossil boilers superheater and reheater tubes, incontrast, hot furnace gas is the source of heat, and thermal energy flows in the oppositedirectionfrom the tube"s outside wall toward its centerline. Under these conditions, the tube-metal temperature can be higher than the steam temperature. As a result, 9 percent Cr-steelcan be used for piping applications up to steam conditions of 1,100 F. But for tubingapplications, the operating steam temperature is limited to 1,050 F.

Kahe Unit 5

By the mid-1990s, P91/T91 was gaining acceptance in conventional fossil plants. Superheater

sections made of T91 were retrofit at Tennessee Valley Authoritys Kingston Unit 5, whileheaders made of P91 were installed at Appalachian Power Co.s (now AEPs) G len Lyn andClinch River stations and at Dayton Power & Light Co.s Stuart Station. Though these projectsfaced several challenges, the retrofits overall proved successful.

A retrofit completed by Hawaiian Electric Co. Inc. (HECO) typifies the fossil industrysexperience in that decade. HECO"s Kahe station Unit 5 had suffered a series of failures ofsecondary-superheater tubes. A life-extension study proved the feasibility of replacing theentire secondary-superheater tube bundle and T91 was selected as the optimum material.

Kahe Unit 5 is a Babcock and Wilcox Co. El Paso-style pressure-fired radiant reheat boiler witha continuous rated steam output of 965,000 lb/hr at 1,955 psig/1,005 F. The furnace is 27feet wide, 23 feet deep, and 118 feet from the upper-drum centerline to the centerline of thelower-wall header.

Commissioned in 1974, Kahe Unit 5 experienced its first secondary-superheater tube failure in1988, and five more by early 1993. Five of the six failures occurred in the T22 material of thesecondary-superheater inlet tubing. The sixth failure occurred in 304H stainless-steel material.

All tube failures were attributed to creep damage from excessive metal temperatures. Acontributing factor to one of the T22 failures was misalignment that exposed the tubes to theradiant heat of the furnace. Oil-ash corrosion resulting from the firing of high-sulfur oilearlier in the unit"s life also contributed to the failure of the 304H stainless material. Acondition assessment conducted in 1989 showed some tubes in the inlet section hadremaining useful life as low as 13,000 hours.

HECOs refurbishment specification called for two types of bids: "replacement in-kind" andreplacement of the T22 material with T91. HECO engineers understood that T91 would offer

the following advantages:

Higher allowable stress for a given temperature Lower coefficient of expansion than stainless alloys Potential for improving plant efficiency by raising turbine-inlet temperature Potential for lowered thermal-fatigue cracking because of thinner walls


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Importantly, HECO engineers also understood and paid attention to the potential drawbacks tousing T91, which included:

Higher fabrication cost, because of the stress-relieving required after bending andwelding, and the straightening and removing of oxide scales required after stress-relieving

Concerns with quality assurance of the tubing from U.S. manufacturers with limitedexperience in 9Cr-1Mo steel

Maintaining the design pressure drop through the secondary superheater with thethinner-walled T91 tubes

The successful bidder advocated replacing T22 in Rows 2 through 39 with T91, and usingthicker-walled 304H in Row 1. Two of the most important features of the winning bid were theaddition of "safe-ends" to the T91 and 304H tubes outside the furnace, and minorrearrangement of the 304H tubing. Together, these features reduced the number of dissimilar-metal welds inside the furnace to one per element total number dropped from 189 to 27. All"safe-ends" were radiographed in the shop during the fabrication process.

Because of concerns about quality control and the lack of material availability in the UnitedStates, HECO bought its T91 material from Vallourec Industries" Power Generation Division

(France), an experienced supplier to European plants where the new alloy had already beenapplied for several years.

Field installation of the T91 secondary-superheater tubing was accomplished in five weeks with30 people working seven days per week. Existing elements were removed with saws instead oftorches to minimize contamination of the headers with foreign debris. The only T91 fieldwelding required was to join the upper and lower sections of secondary superheater. TheseT91 field-welds were radiographed and stress-relieved according to the supplier"s stringentprocedures and ASME Code. All welding documents and radiographs were reviewed andapproved by the authorized inspector. Also, a steam-blow was conducted to purge the systemof foreign debris prior to conducting a hydrostatic test at the drum working pressure of 2,300

psig.

Quality AssuranceHECOs attention to quality assurance was a key reason for Kahe Unit 5s successful retrofit.Thats also a key difference between the fossil-boiler and the combined-cycle experience,according to William F. Newell, Jr, EuroWeld Ltd.s vice president. Newell made his commentsduring a presentation at the P91/T91 Workshop, conducted in July 2005 in Philadelphia by theHRSG Users Group (see sidebar). In the fossil-boiler industry of the 1990s, Newell explained,The designers, fabricators and installers followed all the rules. They operated withconservative design margins (wall thickness), at reasonable steam temperatures (1,050 F orlower), and they carefully chose their steel producers and component fabricators. Newellemphasized that all Grade 91 welds regardless of thickness or diameter require a precisepost-weld heat treatment (PWHT), and that welds between dissimilar metals should beminimized and properly designed. HECO, along with other P91/T91 users in the fossil-boilerbusiness, applied these principles well.

However, by the late 1990s and early 2000s, competitive pressures within the U.S. powerindustry and the building boom in new capacity pressed many in the combined-cycle sector toneglect some of the principles.

Modified 9Cr-1Mo was seen by the booming combined-cycle industry as a silver-bullet remedyfor two major troubles plaguing large HRSGs in cycling duty: thermal fatigue of thick-walledcomponents, such as main steam piping and superheater headers, and creep damage in thesuperheaters (Figure 2). Modified 9Cr-1Mo is effective because the alloys mechanicalproperties allow pressure-containing components to be made in thinner sections, leading to

smaller temperature gradients across the wall and reducing time for the metal to reach


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thermal equilibrium, and ultimately resulting in less thermal fatigue. For example, the upgradeof a typical HRSG superheater header from P22 to P91 can reduce wall thickness by 54percent, and component weight by 65 percent.

Click here to enlarge imageFigure 2. Most early-service life failures in HPsuperheaters, reheaters, and economizers

have occurred at the attachment weldbetween an acute tube bend and the header,or occasionally at small radius bends used toconnect tubes to the header. Photo courtesyof EuroWeld Ltd.

In addition, the alloys high creep-rupture strength and resistance to oxidation would minimizedamage to superheater sections, particularly those coupled to the latest F- and G-class gasturbines that experience the highest metal temperatures.

Unfortunately, as Newell reported to the HRSG Users Group, many of the owners and buildersin the combined-cycle industry downplayed the concerns of the early fossil-boiler adopters,and handled the advanced alloy as if it were a traditional steel. It is anything but.

Focus on Microstructure

Modified 9Cr-1Mo alloy is an advanced material whose mechanical properties depend on thecreation of a precise microstructure, and the maintenance of that microstructure throughoutthe components service life, explains Jeff Henry, director of Alstoms materials technologycenter. Henry also is chairman of an ASME Task Group assigned to study the material, anddevelop new standards for handling it. With traditional low-alloy steels like Grades 11 and 22operating at the low stresses typical of power applications, the microstructure produced duringsteel-production and component fabrication was of only minor importance. In fact, for thesematerials it was found that a wide range of microstructures produced by both authorized andprohibited heat treatments would still provide satisfactory service.

At the July Workshop, Henry emphasized how the superior properties of P91/T91 hinge on aprecise addition of vanadium (V), niobium (Nb) and nitrogen (N), and a carefully controlled

normalizing process to produce a complete phase transformation from austenite intomartensite. This produces a hard steel with high tensile strength at elevated temperatures andhigh creep resistance. Next, a controlled tempering process must follow, to allow the V and Nbelements to precipitate as carbides and carbon nitrides at defect sites in themicrostructure. This serves to anchor or pin the defect sites, thereby holding themicrostructure in place.

Henrys advice concerning the importance of the V and Nb additions and their precipitatingaction was backed up by a recent study in Japan. Conducted by Takashi Onizawa, and others,of the Oarai Engineering Centre, Japan Nuclear Cycle Development (Tokyo), the study was


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presented at the ECCC Creep Conference, held in September 2005 in London by the EuropeanCollaborative Creep Committee. Until Onizawas recent work, the long-term efficiency andstability of the strengthening mechanisms provided by the fine particles had not been clarified.In the Onizawa study, a series of trial products controlling V and Nb contents were produced,and mechanical tests were conducted both before and after a 6,000-hour aging process.While the eventual goal of the study is to confirm the strengthening mechanisms under thefast breeder reactor operating conditions 1,112 F for 500,000 hours the current study

clearly confirmed that higher strength and lower ductility were entirely dependent on theproper additions of V and Nb contents and the attainment of the proper microstructure.

Failure to achieve that proper microstructure during original steel production or to maintain itduring any subsequent action in the steels life such as the hot bending, forging or weldingthat regularly occurs during component fabrication, plant construction and component repairsat a power plant will cause a phase change away from 100 percent properly temperedmartensite or will disrupt the precipitates. Either of these effects, Henry reported, will destroythe mechanical properties of the alloy.

Click here to enlarge imageFigure 3. The microstructure of P91components has been damaged at somecombined-cycle plants. A common error has

been performing localized heating of thecomponent with oxy-fuel torches, which arenotoriously difficult to control. Photo courtesyof EuroWeld Ltd.

Unfortunately for HRSG users, the microstructure of P91 components has been damaged atsome combined-cycle plants. A common error, as Newell explained during the July workshop,has been performing localized heating of the Grade 91 component with oxy-fuel torches(Figure 3). These are notoriously difficult to control and almost always provide destructive,non-uniform heating. Another common error has been following an incorrect procedure forPWHT temperature too high, temperature too low, or temperature not maintained for thecorrect duration. Even worse, some contractors are repairing P91 components without

performing any PWHT at all.

ASME Code Enhancements

Many combined-cycle plant owners and operators assumed that merely specifying compliancewith the ASME Boiler and Pressure Vessel Code in their new-construction and repair contractswould prevent such problems. However, the ASME Code rules are not comprehensive enoughto address all of the material-processing demands and to prevent continued failures ofP91/T91 components. In fact, Henry believes that the problems in large HRSGs will actuallyget worse unless more comprehensive Code rules are established and enforced. Thats why heis chairing a Task Group, working under the direction of the chairman of Section II (Materials)of the ASME Boiler & Pressure Vessel Code, to develop detailed rules for processing Grade 91,


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as well as other approved steels classified as creep-strength-enhanced ferritic (Grades 23,92, 122, etc).

Henry and his team have identified eight specific issues concerning the use of creep-strength-enhanced ferritic steels, and are studying Code changes that will control their use moreeffectively. The Task Group has presented its recommendations for several of the eight issuesto the Section II Committee of the ASME Boiler & Pressure Vessel Code. It is not clear when

the Section II Committee will act on those recommendations with formal changes to the Code.

In the meantime, Henrys Task Group continues to study the remaining issues it has identifiedregarding P91/T91 and other high-strength ferritic steels. At the HRSG Users Groupworkshop, the issues were discussed in detail between Henry and the many P91 authoritiesparticipating in the meeting. A few are highlighted below.

Post-Weld Heat Treatment

A second issue being addressed by the Section II Task Group is the effect of weld fillers on

PWHT. Certain alloying elements in the filler principally nickel and manganese depressthe AC1 and AC3 temperatures, as well as the martensite start (Ms) and martensite finish (Mf)temperatures. During PWHT, this presents the risks of intercritical heat-treating damage anduntempered martensite in the weld metal. Henry noted that the AWS standards allow up to 1

percent Ni in weld metal, in contrast to 0.4 percent Ni maximum in base metal specifications.

In response to this issue, the Task Group has proposed new PWHT limits on Grade 91components based on Ni plus Mn content. Specifically:

PWHT temperature range must be 1,350 F to 1,425 F, if chemical composition of thefiller metal is not known precisely

If the chemical composition of matching filler metal is known precisely, the maximumPWHT temperature can be increased to 1,470 F (if Ni + Mn < 1.00 percent) or 1,450 F (ifNi + Mn is between 1.00 percent and 1.50 percent)

For components less than or equal to five inches thick, minimum PWHT time must beone hour per inch with a minimum PWHT time of 30 minutes

For components greater than five inches thick, PWHT must be five hours, plus 15minutes for each inch over five inches

For weld thickness less than one-half inch, minimum PWHT temperature is 1,325 FIntercritical Region/Tempering

One of the most significant problems with Grade 91 is post-production exposure totemperatures in the intercritical region. This is above the temperature where martensitebegins to transform back into austenite (referred to as the lower critical transformationaltemperature or AC1) and below the temperature where phase transformation is complete(called the upper critical transformational temperature, AC3). When Grade 91 is exposed tothis intercritical region, the martensite is partially re-austenitized and the carbon-nitride

precipitates are coarsened but do not fully dissolve back into solution. The resulting material i sa part austenite/part martensite metal that lacks the pinning effect of the precipitates, andtherefore has a substantially reduced creep-rupture strength.

Exposure to the intercritical region and the resulting reduction in strength leads to the Type IVcracking found in many P91 welds. In a Type IV failure, cracking takes place in the fine-grainsection on the base-metal side of the heat-affected zone of a weldment. Abrupt changes inwall thickness or other features that create high stresses in the region of the weld set up theconditions necessary for this cracking. Type IV failures are a matter of significant concernbecause they occur at a relatively early stage in component life 20,000 to 40,000 hours


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at lower operating temperatures than the maximum design temperature of 1,110 F, and theycan initiate and grow sub-surface for some distance before breaking through to the surface.There have been about a dozen such failures in P91/T91 components, mostly in the U.K.where the alloy has been in service longer than in the US, but we may be poised to catch up.One U.S. user at the workshop reported several P91 weld failures in steam piping of hiscompanys relatively new fleet of F-class combined cycles.

A related problem is over-tempering, which occurs when P91 or T91 components experienceprolonged exposure to elevated temperatures below the lower critical transformationtemperature. This does not affect the martensite, but it does cause coarsening of theprecipitates, with a corresponding loss in creep-rupture strength due to the loss of theirpinning effect. Over-tempering is a lesser risk during fabrication, Henry explained, due tothe relatively short times of the thermal treatments. But in cases where multiple heattreatment cycles are applied in the fabrication of thick-walled components, weakening couldbecome a significant issue at higher tempering temperatures.

Click here to enlarge imageFigure 4. Incorrect at the steel mill was thecause of this failure in a Grade 91 component.In addition to a loss of creep-rupturestrength, risks associated with improper

tempering are brittle fracture and stress-corrosion cracking. Photo courtesy of AlstomPower Inc

Under-tempering also can jeopardize the high-temperature properties of Grade 91, since therequired precipitation does not go to completion, and the precipitates either are absent or are

of insufficient size to stabilize the structure (Figure 4). In addition to a loss of creep-rupturestrength, risks associated with under-tempering are brittle fracture and stress-corrosioncracking.

To avoid intercritical-region exposure, over-tempering, and under-tempering, Henrys TaskGroup is recommending several rule changes to the ASME Code. Specific limits being proposedare:

1,900-1,975 F for normalizing 1,350-1,470 F for tempering 1,325-1,470 F for PWHT of components thinner than 0.5 inch 1,350-1,470 F for PWHT of components thicker than 0.5 inch For any component in which a portion of the component is heated above 1,470 F, the

component would have to be re-normalized and tempered in its entirety, or as an


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alternative, the heated portion could be removed from the component for re-normalizingand tempering and then replaced into the component.

Hardness Testing

Another of the issues that Henrys Task Group is tackling is quality-assurance testing. Todetermine whether the processing of creep-strength-enhanced ferritic steels has been

performed correctly, users need a non-destructive evaluation (NDE) tool that can quickly andinexpensively provide information on the overall condition of the material. Because hardnessprovides a direct indication of a materials room-temperature tensile strength, which can beused to roughly estimate the elevated-temperature behavior of the material, portablehardness testing has been considered as such a tool.

Although commercially available portable indenters have been available since the 1920s,hardness testing equipment really is designed for use in laboratories, not in the field. Withportable equipment, there is substantial variability in hardness test results. Whats needed is arugged attachment for indenting devices that can take accurate hardness readings at a powerplant thats on-line and operating at temperature.

Until such a tool gets developed, the ASME Task Group has not yet been willing to recommendspecific hardness limits on advanced alloys. A leading HRSG manufacturer, NEM b.v.

(Netherlands) feels more confident in establishing some guidance in this area. The companysmaterials and welding engineer, Ing. Patric de Smet, IWE, speaking at the July workshop,asserted that if the Grade 91 material has received proper heat treatment, hardness testresults will fall in a relatively tight range not too high and not too low. NEMs guidance onPWHT calls for a temperature range of 1,380-1,420 F, and a duration of two to three hours. Ifthis guidance is followed, de Smet said, the hardness will drop to 200-270 VHN (VickersHardness Number) and the ductility and high-temperature strength will be suitable for service.

Determining Creep Damage

A different NDE tool was discussed at Septembers ECCC Creep Conference, by several of deSmets fellow countrymen. Harry J. M. Hulshof and Paul G. M. Welberg pf of KEMA Nederlandb.v. (Netherlands) teamed up with Leo E. de Bruijn of E.ON Benelux Generation n.v.(Netherlands) on a paper titled Creep Strain Measurements for Risk Based Monitoring of

Steam Pipes and Headers.

In the paper, the authors presented information on KEMAs Speckle Image Correlation Analysis(SPICA) system, which enables users to measure the deformation caused by creep in criticalareas of their piping and headers such as the heat-affected zone in weldments. Thetechnology can be applied to plants that are on-line and operating at temperature. Accordingto the authors, plant managers can use the strain measurements as an indication of creeprate, from which you can assess how much creep life has been consumed, and by extensionhow much service life remains in the plant component. Note: Creep is a collection ofdiffusion processes driven by temperature and mechanical stress, which cause permanentdeformation that can be measured as strain.

The technique essentially involves making an optical fingerprint of the surface of a componenton the basis of textural features. A recorded image of a rough surface is used as a

"fingerprint" of the object surface. Two images, one recorded before and one after loading, arecompared by image correlation. By analyzing the results, the strain distribution due to theloading is calculated from relative displacements in two directions.

KEMAs strain-measurement technology has been applied at several Dutch power plants, theauthors reported, to monitor strain during the last seven years. One of them is E.ON Beneluxscoal-fired plant at Maasvlakte (Rotterdam), Units 1 and 2 (540 MW each). Provisions for bothSPICA and capacitive sensors were mounted. The locations that were monitored are bends(inner and outer curve), welds in the saddle point of T-joints, Y-joints and circumference weldsin straight pipes. The utility company uses the results to plan activities during the next


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overhaul and to build a strategy for condition-based maintenance. In the past there have beenmajor overhauls at Maasvlakte every two years. This interval now has been extended to fouryears.

Creep-Data Assessment

Our understanding of creep is advancing steadily (no pun intended). For example, the

European Collaborative Creep Committee (ECCC) was founded in 1991, and today includesnearly 50 organizations from the United Kingdom, Germany, Italy, France, Switzerland,Austria, the Netherlands, Belgium, Sweden, Denmark, Finland, Portugal, The Czech Republicand Slovakia. Companies participating in ECCC cover a wide range of industries andorganizations dealing with high-temperature metallurgy: steel makers; boiler and turbinemanufacturers; powerplant architect/engineers; power producers; inspection agencies;research institutes; technical universities; and testing laboratories. One of the committeesachieved results according to a paper presented by G. Merckling, Istituto Scientifico Breda,Milan, Italy, at the ECCC Creep Conference, conducted September 2005 in London is thedevelopment of an accepted evaluation method to understand and to weight the quality ofcreep-data test results.

Click here to enlarge imageFigure 5. Collaborative efforts in Europe aimto develop one accepted evaluation method tounderstand and to weight the quality ofcreep-data test results. Diagram courtesy ofIstituto Scientifico Breda.

For years, different creep-strength authorities have applied different evaluation methods, eachone resulting in quite different creep-strength and life-assessment predictions using the verysame test data. In contrast, the ECCCs evaluation method dubbed the Post AssessmentTests (PATs) yields consistent creep-strength predictions, which according to the committeewill be suitable for inclusion into European standards (Figure 5). With only minor variations for


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various assessment conditions, Merckling reports, the PATs have proved to be sound andreliable. In addition, mechanisms in the PATs allow for upgrades and additions in the future,so that its application can be expanded to relaxation strength, small and weldment data sets,post-exposure remnant creep strength, and creep strain models. And with the recentdevelopment of an Excel-based tool, referred to as the ePAT, the program is automated forquicker and more user friendly application.

Other ASME Code Changes

While Henry and his Task Group are working to revise Section II of the ASME Code (Materials)to improve fabrication and repair practices for creep-strength enhanced ferritic steels, two ofhis Alstom colleagues are working to revise Section I of the Code (Power Boilers). Their goal isto improve the economics for next-generation fossil units.

Speaking at the ECCC Creep Conference in September, Alstoms I. J. Perrin and J. D. Fishburnpointed out that the push to advanced cycles with ultra-supercritical steam conditions willrequire the use of very expensive, nickel-based alloys. New design equations are needed inSection I of the Code, Perrin and Fishburn believe, to better account for secondary stresses

during thermal transients (cycling of the plant). Better design rules will enable designers toreduce the wall thickness of tubing, as well as that of headers and piping, without

compromising component reliability or safety. This will translate into a significant saving ofexpensive material, and thereby improve the economics of advanced ultra-supercriticalboilers, the authors believe. Perrin and Fishburn estimate that in ultra-supercritical steamgenerators a 12 percent reduction in the cost of pressure parts can be achieved.

Proposed revisions to Section I of the ASME code to permit the use of simplified and moretechnically defensible design equations were submitted to Subcommittee I and accepted bythem on September 2, 2004. Subsequent to that, they were included in the Main Committeeballot. Feedback is awaited.

HRSG Users Gathering in the Rockies

William F. Newell, Jr, will be addressing the HRSG Users Group again, this time at the groups

2006 annual conference. Newell, who is vice president of EuroWeld Ltd, will present WeldingTechniques for a Successful Plant Outage. Other presentations at the conference include:

The Risks to HRSGs of Low-Load Operation, by Scott Wambeke, Systems Engineer,HRST Inc

New Technologies for HRSG Tube Repair, by David W. Gandy, EPRI; and Ken Brazell,Encompass Machines Inc

Safety-Valve Testing & Maintenance, by Robert Pabst, Valve Design & MaintenanceConsultant, Movaco Inc

The HRSG Users Group 14th Annual Conference will be held March 13-15, 2006, at theBroadmoor Hotel in Colorado Springs, Colo. For details, visit www.hrsgusers.org/events.php or

call 1-718-317-6737.

Power Engineering February, 2006

Author(s) : Robert Swanekamp

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Handling Nine