A Rehabilitation Scheme for the Lake Chelan Hydroelectric Project

8/11/2019 A Rehabilitation Scheme for the Lake Chelan Hydroelectric Project

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A Rehabi li tat ion Scheme for t he Lake Chelan Hydroelec tr ic Pro jec t Based onSchedule Reduction

By Sphane Roy, Alstom Hydro CanadaJean Doyon, Alstom Hydro Canada

Vincent De Henau, Alstom Hydro CanadaSteve Sembritzky, Public Utility District no. 1 of Chelan County

ABSTRACT

Alstom Hydro and the Public Utility No. 1 of Chelan County recently signed a Contract for therehabilitation of the Lake Chelan Units A1 and A2 turbines and generators, including associatedgovernor systems and ancillary equipment. The Lake Chelan Hydroelectric Project is locatednorth of the city of Wenatchee in the Chelan County, near the geographic center of WashingtonState.

Two important factors affecting the project schedule is the goal to minimize the outage periodand the fact that the generators are considered to be at the end of their useful life andnecessitate an urgent overhaul. In order to provide the shortest project schedule and outageperiods, with the aim to diminish the risks of a generator failure resulting in important losses inproduction, Alstom proposed to the PUD a rehabilitation scheme based on an acceleratedschedule, aggressive outage times and new components which reduce risks to the overallproject. The outage period was critical to PUD in terms of lost revenues, but also to guaranteeavailability to the network for the most energy-consuming cold season.

The purpose of this paper is to present an overview of the rehabilitation scheme adopted tomeet the Contract schedule. It was not possible to proceed with the normal stage scheme ofmodel development, mechanical engineering, material procurement and manufacture.

Introduction Availability, outage time and schedule are important to many projects, but particularly critical forthis project. The Lake Chelan Hydro project is operated in a manner which regulates reservoirlevels and maximizes the high load generation capability and capacity. Plant capacity is closelymatched to the available inflows and reservoir operating restrictions, resulting in a plantutilization factor of over 90%. Outages of short duration will shift production from high load hoursto low load hours resulting in lost generation value. Longer outages result in spill andsignificantly higher losses in generation value. Availability, outage time and schedule areimportant to many projects, but particularly critical for this project as a result of the minimal timeallowed for downtime.

The first impact of the schedule reduction is evident for the hydraulic development phase of thenew runner with the model testing being conducted in parallel with the castings supply process,reducing the delay between the time the blade profile design is frozen and the machining of allthe runner blades.

Reliable computational fluid dynamics (CFD) calculations rather than model test outputs werewidely used for the design of mechanical components, such as the new wicket gates and

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servomotors. With the close collaboration between the PUD and Alstom, the units were madeavailable at a very early stage in the project for a thorough site inspection of the units.

The units will also be upgraded in terms of environmental friendliness as the turbine oil guidebearing is being replaced by a water-fed hydrostatic guide bearings, which also acts as a shaftseal and all bronze greased bearings are replaced with self-lubricated bushings. The pressureof the hydraulic unit operated by the new electronic speed governor is increased by more than aten-fold factor thus significantly reducing the volume of oil.

The upgraded generator contains among other things, an all-new stator frame and coolers, andnew rotor poles to suit the extra 20% generator output.

The project is actually in its site activities phase while the refurbishing of the first unit is beingcompleted during the 2009 summer.

Powerhouse location and units descriptionThe Lake Chelan Hydroelectric Project is located north of the city of Wenatchee in the ChelanCounty, near the geographic center of Washington State. The dam is located adjacent to theCity of Chelan at the lower (southeasterly) end of 55-mile-long Lake Chelan. The Powerhouse islocated near the West Bank of the Columbia river, just north of the community of Chelan Falls.

The existing Units A1 and A2, originally commissioned in 1927, are vertical shaft Francisturbines, directly connected to vertical synchronous generators. The original exciters werereplaced with static exciters in 2003. The turbines are controlled by analog-electronic governorsthrough a 175 psi hydraulic pressure system.

The turbines have a rated output of37250 HP under a net head of 346 ftand a speed of 300 rpm. They were

originally manufactured by I.P. Morrisand are equipped with a Moody coneunder the 76.50 inches throat diameterrunners. The runner dismantling is frombelow and is attached to the shaftthrough a keyed taper hub. The shaftruns in an oil lubricated guide bearing.The wicket gates are a steel castingand are supported by 3 greasedlubricated bronze bushings. Two22"diameter low pressure servomotors

control the wicket gate mechanism thatcontains shear pins protection but nofriction device to avoid flailing of the wicket gates. With such old units, it is not surprising to findextensive use of cast iron, even for the largest components like the headcover, the bottom ringand the draft tube cone. The spiral case/ stay ring is a five piece cast steel assembly embeddedin concrete. The runners were replaced in the mid 80's as well as a portion of the draft tubecone.

Figure 1: The original assembly

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The existing generators, originally manufactured by General Electric, were commissioned in1928, rewound in 1950-1952, and have otherwise been in continuous service, subject toavailability of water to operate the turbines. The main exceptions to this was when the turbineinlet valves were replaced in 1998 and no water was available in the tunnel for an extendedperiod and also, in 1985-1986 when the turbine runners were replaced and the units weredisassembled. The generators are rated 30MVA, 0.8 power factor, 24 MW, 11 kV, 60 Hz, basedon 60C temperature rise. The normal operating point today is 27 MW, 0.95 power factor.

The overall generator efficiency, according to the original 1928 test report, maximizes at 97.4%.No records have been located identifying any cut out or shorted stator coils. During the turbinerunner replacement in 1985 and 1986, the generator was dismantled to facilitate the line boringof the turbine runner seals and the turbine shaft. At the same time, the generators were also re-

wedged and new thrust bearings were installedalong with a high-pressure lift system.

The original thrust bearing was a GeneralElectric spring type of the vintage available in1926. The new thrust bearing is a Kingsburytype bearing, reusing the original thrust runnerwhich is removable from the main shaft. It isanticipated that the units were plumbed andcentered at this time. The thrust bearing islocated above both the generator rotor and theoriginal cast iron upper spider bracket. The unitis also equipped with a shell type upper guidebearing located below the thrust bearing, insidethe generator air housing. Based on thetemperature rise in the thrust bearing pads andoil, the thrust bearing has margin for additionalloading, should it be required. The shaft line is

very long with about 10.5 meters (34'7")between the centerlines of the turbine and thegenerator. The turbine shaft itself measures 27feet long.

The hydraulic-mechanical part of the governoris the original 70 year old equipment withselected modifications added when upgraded in

1978 to an analog electronic governor. The present electronic governor provides PID control ofthe governing function, reusing the previous mechanical governor components to the furthestextent possible. The original gate restoring rod system from the turbine servomotors was reusedas well as the governor manual control valve.

Figure 2: Cross section of the powerhouse

Condition of the generating units A condition assessment of the powerhouse completed prior to commencement of therehabilitation project, identified that over the last twenty-five years many replacements and/orupgrades took place on the civil structures, electrical/mechanical systems and equipment. The80+ year old plant remains in relatively good condition with only some minor systems requiringimmediate attention. However, the generating units require replacement in the near future andthis represented an opportunity to utilize common outages and resources to complete the

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modernization of the plant, to maximize production and to ensure reliable generation for the next40 years.

The generators, originally commissioned in 1928, and rewound in 1950, are overdue forrehabilitation. Only the stator winding was renewed in 1950; the stator core, rotor and fieldwindings are over 80 years old. Because of the age and the technology utilized in thegenerators, staff concluded based on industry data and internal and external expert opinion, thegenerators, are statistically beyond their useful life, and have a high probability of failure in thenear future. Further, there is a high likelihood that a winding or end-turn failure will result in agenerator fire due to the age of the generator, insulation type, and current condition of theinsulation. Economic studies evaluated several scenarios, from waiting for a generator to fail inservice, to proactively pursuing a planned replacement. These studies conclude that there is asubstantial economic benefit from a planned replacement of the generators rather than fromwaiting for them to fail in service. Estimates of the unplanned outage costs from lost generationand from rewinding the failed generator approached the cost of the planned generatorreplacement for this project due to potential lost revenue costs.

The existing stainless steel runners were replaced around 1984 with minimal modifications tothe other turbine components. The replacement was done without conducting any physical orcomputer modeling and the performance exceeded the output guarantees but efficiency waslower than expected. Currently the runners are in good condition but require cavitation repairoutages every three to five years. An in-depth performance assessment justified replacementwith a new more powerful runner of modern design. Replacement of the turbine componentsalso allowed for a better match of preferred unit performance, with the best efficiency nearmaximum output, and eliminated the present cavitation problems.

The hydraulic-mechanical portion of the governor is the original 70 year old equipment withselected modifications added when upgraded in 1978 to an analog electronic governor.Surprisingly the governor has the highest probability of failure due to the obsolescence of theelectronic controls and known accumulator and sump tank leaks. Any failure of the 30 year old

electronic controls has to be analyzed and repaired at the board level, resulting in extendedoutage duration. Recent pressure vessels inspections on the accumulators noted minor leaks atthe riveted joints and recommended replacement in the near future. Leaks indicate there couldbe some corrosion or cracking of the surrounding metal or rivets.

The typical refurbishing s chemeSince the beginning of the 90's, with the installed base becoming older and older, an importantnumber of refurbishing projects has been done. During those years, the typical scenario of arefurbishing scheme evolved slightly as the factors affecting the return on the investmentbecame better known and as the statistical values of the cost and outage period were built. Thefirst projects performed were mainly focussed on the replacement of the runner to increase the

efficiency of the unit and to reduce the maintenance cost of cavitation repairs. The use of the 5axis machining and of the use of martensitic stainless steel for the runner helped to achievethose targets. In parallel, the development of the CFD permitted a better understanding of thedifferent losses in the existing components, combined with the new runner. Better performanceswere then achieved by replacement of some components, mainly the wicket gates, and by somemodification of the embedded ones.

The typical scheme following the contract award to a manufacturer is to perform the hydraulicstudies in which the proposed solution is developed and tested on the model to validate the

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performances. The second phase is then allowed to start, in which the mechanical design of thecomponents is done and the fabrication process of the new components starts. The scopeusually includes the replacement of the wearing parts, the verification of the alignment of theunit and the inspection of the re-used components. The base scope also involves thereplacement of the greased bronze bushings by self-lubricated material; the economic impact isnot so important and the environmental benefit is clear. Different procedures and plans are thendeveloped for the site activities and the first unit is then shut down for refurbishing. Roughfigures will show a 1 year schedule for the hydraulic development and model testing, a 1 yearperiod for the mechanical design and purchasing of raw material and another year formanufacturing. A typical outage will then add 40 weeks before the completion of the refurbishingof a first unit. Those figures will vary greatly depending on the scope and specificities.

More recently, there is a big challenge to reduce the outage period to perform the site works. Astopped unit does not produce revenues and the period of the year where the outage is plannedis easily defined. Because the reservoir does not have enough capacity to store predictedinflows during the outage, any spill that must occur represents lost revenue.

For sure, the planned outage is greatly influenced by the scope of work to be performed. Withgood experience and know-how, it is relatively easy to identify the critical path of the knownworks and to keep the workflow as scheduled. However, in any refurbishment project, there aremany situations that influence the work to be performed and additional activities are oftenneeded to restore some components or systems that show unforeseen defects. This results in arisk of delay during the outage period as unknown situations may impact the critical path.

Parameters affecting the outage duration Outage duration will be affected by a few main parameters. The scope of the base refurbishingwork will have a direct impact on the outage duration. Re-stacking and re-wedging a generatorin place will take more time than just replacing the rotor poles. Machining of the embeddedcomponents will also be time-consuming. When dealing with refurbishment, the turbine

components are often on the critical path; the wicket gates and bottom ring/headcover are aboutthe last components available for refurbishing but also the first ones needed to start the re-assembly. A good selection of the base work scope will perhaps tend to increase the plannedoutage duration but will also tend to minimize the risk of delay. For example, a minimal scope toreplace only the runner could lead to an important delay because the condition of the fixedlabyrinths was not assessed and could not be reused. On the other hand, some refurbishingprojects have already been done where each of the machined surfaces of the existingcomponents was machined anew. This minimizes the risk of delay but also increases the basescope duration and project cost. The decision to put an activity on the base scope or on anoptional scope may be managed by experienced people but there is still the case of unexpecteddefects found during the inspection phase.

Beside the site works needed to install and modify the components that offer increasedperformances of the unit, the shut down period also gives the opportunity to inspect everydismantled component . After all, the unit should not be dismantled again for many years and itis of a prime importance to assess condition of the components that will be reused. Theinspection will take place directly at site or in a shop depending on the nature of the inspectionto be done and on necessity to modify/refurbish the component. The inspection will cover NDT,dimensional and geometrical verifications. Some of those verifications will be used to quantify aknown problem. The repair works will usually be already planned and will not affect theschedule. However, unknown defects will also be discovered and will possibly impact the

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schedule. Those defects are of various types but usually involve soundness of the material. Wemay think of cracks, wear, deformation, electrical defects, etc. When such defects are found oncomponents that are already on the critical path, the impact on the schedule is immediate.

Finally, the outage will also be impacted by any problem arising during the commissioning. Therisk related to such problem will be minimized by the seriousness of the base work definition,the inspection plan and the know-how of the team in charge of the refurbishing. As an example,during re-commissioning of Unit A-1 in 1985, a packing gland failed and the generator bearingspilled oil and water on the windings. The repair to the packing was made. The generator wascleaned by spraying it with carbon tetrachloride, and then given a dry-out run. The failureresulted in an extended outage lasting from August to October before final cleanup, repairs anddry-out were completed.

The proposed solutionBecause of the specific context, Alstom proposed a solution to reduce the overall projectduration with a particular focus on the outage duration. A brief analysis concluded that newcomponents for the turbine would be preferable than refurbishing: the size of the unit is not quitelarge, the expected service life is 40 years, the refurbishment of those components is on thecritical path and many of the components are made of cast iron. This last characteristic isparticular to very old units and the risk of impact on the schedule is important. Any service crackon the component is not easily reparable since welding is usually not acceptable. The repair willhave to be made using mechanical means like stitching or steel plate bolt-on stiffeners. Thosetechniques can be used to successfully repair cast iron components but needed engineeringanalysis and repair time will impact the schedule.

The solution for the new turbine components is based on a standardization effort made by Alstom a few years ago, for medium head/medium output Francis units. A base configurationand characteristics of the components was implemented in the existing embedded componentseven if the standardization was developed for a new unit. The use of the standard configuration

accelerated and facilitated the design choices. Little adaptation was needed to fit with theexisting components but the impact was negligible. The complete replacement of the governorand HPU system was also in line with this approach since the higher pressure permitted toinstall the servomotors directly on the headcover as suggested by the references.

To reduce the project duration, several tasks were also conducted in parallel during thehydraulic design and runner material purchasing. Mechanical design also started before modeltesting.

Finally, the use of new components also helped to reduce the outage duration since most of thecomponents of the turbine are replaced. By doing so, the critical path for site works was pushedon the generator works. To reduce the outage duration, it was also decided to propose some

new components for the generator as well. The following sections give some details about theretained solution.

As compared to a typical scheme, the project duration reduction is of almost 1 year between thecontract award and the first unit on-line. The outage duration reduction is of about 15 weeks.

The hydraulic design and model development In the course of a typical rehabilitation project, the optimization of the hydraulic design of thenew runner is performed using CFD calculations followed by a validation on a homologous

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model of the prototype turbine. In addition, several hydraulic characteristics such as cavitation,runaway and stability, which are difficult to predict by calculations, are investigated on model toinsure the overall integrity of the hydraulic design of the new runner in the existing frame. It isonly once this phase of the project is completed that the runner blade profile design is frozenand released for casting procurement.

Because of the reduced schedule for the Lake Chelan project, the usual procedure for thehydraulic development and casting procurement could not be followed. During the hydraulicdevelopment phase, several tasks were performed in parallel, including the model design andfabrication, the CFD studies to investigate potential improvements to the water passages, therunner design and the casting procurement procedure.

Thanks to a close collaboration between the PUD and Alstom, the units were made available fora thorough site inspection of the turbines. A dimensional control was performed to verify thedrawings and ensure homology between the prototype and the model turbine. Following thisinspection, recommendations were formulated to correct some dimensions of the inlet casingand draft tube cone drawings to match the prototype dimensions.

As the model was being designed and built, potential design improvements to the waterpassages were investigated using CFD studies rather than adopting the lengthy approach oftesting various modifications on model, thereby reducing the time spent on the test-rig. Thesestudies led to an improved design for the wicket gates, with a significant reduction in losses forthe whole operating range (see Figure 3). This new design was directly implemented on themodel. In addition, the hydraulic torque on the wicket gates under normal and most-adverseconditions was also evaluated from the CFD simulations. Based on feedback results obtainedfrom previous projects, where good correlation has been observed between CFD and prototypemeasurements, it allowed designed of mechanical components at an early stage, prior toobtaining any results from the model tests.

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Figure 3 : Comparison of the estimated head losses for th e existing and the new wicketgates at Lake Chelan for the min imum and maximum n et heads.

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10 12 14 16 18 20 22 24 26 28 30

Flow angle e xiting W.G.

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Existing W.G., H=308 ft

Existing W.G., H=393 ftNew W.G., H=308 ft

New W.G., H=393 ft

Expexted operating zonefor Lake Chelan

Several CFD analyses were also performed to investigate modifications to the stay vaneprofiles. It was however estimated that the potential gain in efficiency was not sufficient to cover

the cost of the modification at site as well as the risk and delay associated with this type of work.The original stay vane profile was therefore adopted for the model.

The hydraulic performance of the existing draft tube with a Moody cone proved to be veryefficient based on CFD analysis and it was decided not to make any significant modification toits shape. The site inspection revealed that the Moody cones of both units were very differentfrom each other, as well as different from the original design. Based on the CFD results for thedraft tube, it was decided to keep the original Moody cone design and implement it in the model.

In parallel to the water passages studies, the runner hydraulic design was also optimized withthe help of CFD simulations. These simulations provide a good estimation of the proposeddesign efficiency, power output and cavitation behavior. After several iterations between the

mechanical and hydraulic optimizations, a blade profile was selected for the model runnerfabrication. Because of the reduced schedule of Lake Chelan, the decision was also taken touse this profile for casting procurement prior to the model test confirmation that it satisfied all thecontractual hydraulic guarantees. Sufficient extra material was added to the blade geometrysent to the foundry to accommodate any eventual modification to the profile following the modeltest. In fact, based on the model test, the initial runner design satisfied all the hydraulicguarantees but suffered from a small inlet cavitation problem. A minor modification to the bladeprofile was necessary to eliminate this problem. Because this modification consisted in

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removing some material from the original design, the blade geometry sent to the foundry wasstill adequate and the casting procurement process was not interrupted.

The final runner design surpassed the performance guarantees. In less than three months afteracceptance of the new runner design by the PUD, the castings for the blades, band and crownof the first unit were shipped to the Alstom plant in Tracy, Canada, for machining and assembly.

Mechanical designDesign reviews with key members held at very early stages during the design phase yieldedsolutions not originally planned in the original scope of work, but in the best interests of allinvolved parties. A direct relationship between the manufacturer and the end-user was ideal forthe decision making process.

Figure 4: Disconti nuities in t hescroll case

Before performing any site measurement of theembedded components, it was already planned inthe outage schedule to include site machining ofthe headcover and bottom ring seating flanges onthe stay-ring. Alstom has a successful experienceof restoring original flatness and levelling of stay-ring flanges. This prevents the need for customsite adjustment of distributor for clearance andsealing purpose. The coal-tar epoxy coating willbe removed from the scroll case and replacedwith modern epoxy-resin coating. Hydraulicdiscontinuities between the riveted sections of thescroll will be significantly reduced.

Regarding the draft tube, the top part of the liner needed replacement anyway to accommodatethe new runner dimensions, but the intermediate part is replaced because of uncertainties on its

actual condition. Being made of cast iron, potential repairs were considered too risky to delaythe tight schedule. It was then decided to take no risk on outage time and replace with a newcomponent, delivered at site on time to guarantee completion date.

The original Moody cone concrete nose tipsuffered considerable damage over theyears, including a collapse of the tip. Earlyinspection of the units showed significantwear on the rebuilt tip, due to impact, erosionand/or cavitation. Both units were also verydifferent from each other, as well as differentfrom the original design. CFD studies

indicated that the shape of the existing drafttube with the original design of the Moodycone proved to be very efficient. It was thendecided to install a stainless steel liner to anewly design cone tip to make both unitsuniform and to provide homology with themodel.

Figure 5: Damages on nos e tip

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The new dist ributor During typical refurbishment projects, the distributor rehabilitation consists mainly of aninspection of the components in order to determine their actual condition and make correctiveactions, if any. In addition, bronze bushings with grease lubrication system for the wicket gateand the mechanism are usually replaced with environmentally friendly self-lubricating bushings.For the Lake Chelan project, it was decided upfront not to recuperate the old components andrather install all new components. At the start of the outage, most equipment is already at site,available for installation. The period for disassembly of the components is also shortened asmost equipment is sent for disposal.

It also allowed making a complete distributor assembly, including most turbine pit piping andguide bearing assembly, which reduce site fitting of components. Because of the small size ofthe distributor, it is shipped to site in its pre-assembled shape.

The new wicket gates, casted out of martensitic stainless steel, of higher yield and tensilestrengths than the previous wicket gates, significantly reduced the trunnion size and thicknessof the hydraulic profile of the leaf. The original three-bearing gate design is reduced to twobearings. Nevertheless, the original vertical clearance of the distributor is kept identical by shopmachining of the headcover and the bottom ring stainless steel overlay with a variable profile.

The wicket gate mechanism is now operated from two servomotors mounted directly on theheadcover. This was possible because of the increase in the oil pressure system from nominal175 psi to 2500 psi. The previous servomotor arrangement, with the classical configuration,being supported from anchored base into the foundation, could not have been fully tested duringthe shop assembly. All stroke adjustment and cushioning are confirmed prior to delivery at site.

As clearly shown in figure 6, the new distributor is much more compact than the existing one.

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Figure 6: Existing arrangement on left hand side and new arrangement on right hand side

The new guide bearing The units were also upgraded in terms of environmental friendliness, as the turbine oil guide

bearing is being replaced by a water-fed hydrostatic bearing, which also acts as a shaft seal.With the removal of the greased bushings, the only oil product remaining in the turbine pit isused for the regulating servomotors, where the volume of oil has been reduced by more than 10times.

Although not currently used in North America, the hydrostatic bearing has been used for severalyears in Europe by Alstom, mainly as guide bearings, but also for thrust applications. This typeof bearing operates with pressurized fluid, injected in pairs of pockets diametrically opposed tocreate a positive load on the shaft, which is contrary to a classical hydrodynamic bearing wherethere must be a relative movement between the mobile and fixed part to create such a load.Since there is a reliable source of pressurized water from the scroll case, it is being used as thefluid. In some cases, the head is sufficient to feed the bearing, but this was not the case for the

Lake Chelan, where a booster pump is needed to be incorporated in the water supply line.When the shaft runs eccentrically within the bearing shell, the different radial clearance createsa pressure differential between the opposite pockets, which has a self-centering effect.

Other benefits from this type of bearing is that it can be located closer to the runner, and havetighter radial clearances which help the shaft line on critical speed and operating runouts. Withfresh water consistently injected, there is no need for cooling, and dissipated power is lowerthan for conventional hydrodynamic oil bearings.

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Figure 7: Self centering effect of the hydros tatic guide bearing

No babbitt is used, but rather, the bearing shell and the shaft must both be coated with theappropriate ceramic coating, which was also selected for its capability to allow dry contact incase of a lubricating system failure.

More details of the hydrostatic guide bearing can be found in reference [1].

The new gov erning syst em The original 175 psi hydraulic system is replaced by a high pressure 2500 psi. Such high

pressure prevented use of traditional and cumbersome air/oil accumulator tanks. More compactbladder type receivers (15 gallons) filled with nitrogen were located much closer to the turbinepit.

The generator works The old stator is replaced by a new stator frame, winding and bars. Prior to starting thedisassembly process, the complete new stator with core stacking and bars is already assembledon the erection bay, with most electrical tests in concordance with the contract requirements.The new rotor poles are delivered at site at the beginning of the unit shutdown. The removal ofold poles and replacement with new ones is done on the erection bay simultaneously with theturbine and stator disassembly.

Document control On such a short-term project, it was necessary to reduce to the maximum the dead timenormally spent for document exchange (drawings, specifications, etc). An efficient Web site wasmade available to access to all key project members. Drawings were often posted, commentedand then reviewed within 24 hours, which contributed to the momentum of the project. Prior tosubmittal of detailed drawings, conceptual studies were often posted for discussion.

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ConclusionsWith the units completely overhauled within the less lucrative period and back in operation in ashort time, before the most lucrative period, Chelan PUD has combined the increase in reliabilityof the units with an upgrade in terms of power outputs, efficiency and environmentalfriendliness. Using a less conventional scheme, the project and outage duration is shortenedwithout any compromise on the quality of the product. The know-how and close collaborationbetween Alstom and Chelan were the key factors of this success.

References:[1]: Gilson, P.; Roy, S.; Doyon, J.. Hydrostatic Water Guide Bearings: Making EnvironmentalTechnology Profitable!, Waterpower 2009

Au thors:Stphane ROY, Eng. B.Sc., is Chief of the Mechanical Engineering at Alstom. He works for thisdepartment since 1989. He is now an expert in Mechanical Turbine Design.

Jean DOYON, Eng, M.Sc., is Principal Project Engineer, in the Turbine Engineering Departmentof Alstom. He has 15 years of experience on various projects mainly in North and South

Americas.

Vincent DE-HENAU, Eng, Ph.D., is a Principal Engineer, Hydraulic Design. He has more then20 years experience in numerical calculation methods in fluid mechanics including 10 years ofapplication of such methods to the design of hydraulic turbines.

Steve SEMBRITZKY, is a Senior Mechanical Engineer for Chelan County PUD on the LakeChelan Rehabilitation Project. He led the team that developed the initial scope, schedule and

justification for the Lake Chelan project.

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Documents

A Rehabilitation Scheme for the Lake Chelan Hydroelectric Project