2.Turbine and Accessories

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TURBINE AND ACCESSORIESJ uly-2007 2-1

KOTLIBHEL H.E PROJ ECT, STAGE-IAVolume IIIB (PTS)

2. TURBINE AND ACCESSORIES

2.1. Scope of Work

Scope of work under this section covers the provision of labour, tools,plants, materials and performance of work necessary for the design,model testing, manufacture, quality assurance, quality control, shopassembly, shop testing, delivery at site, site storage and preservation,installation, commissioning, performance testing, acceptance testing,training of Employers personnel, handing over to NHPC and guaranteefor two years of three (3) sets of vertical shaft Francis Turbines as per thespecifications hereunder, each complete with all auxiliaries, accessories,spare parts and warranting a trouble free safe operation of the installation.

The scope of work shall be a comprehensive functional system coveringall supply and services including but not be limited to following:

2.1.1. Vertical shaft Francis turbine and accessories

Three (3) sets of vertical shaft Francis Turbines each have a rated outputof not less than 66.33 MW at rated head of 63.33 metres at guide vaneopening not more than 85%, shall be complete and comprising offollowing main components:

2.1.1.1 Three (3), sets of fixed/ embedded components including Draft tube liner,Dewatering arrangement, Stay ring, Spiral case, embedded piping andfoundation parts.

2.1.1.2 Three (3), sets of stationary, removable components including Draft tubecone, Discharge ring, Bottom ring, Head cover, Stationary Labyrinths,Guide apparatus, Guide bearing and Shaft sealing arrangement.

2.1.1.3 Three (3), sets of rotating components including runner, movinglabyrinths, runner cone and turbine shaft etc.,

2.1.1.4 Three (3), sets of Runner/turbine shaft and turbine shaft/generator shaftcoupling bolts

2.1.1.5 Three (3), sets of pit liners,

2.1.1.6 Three (3), sets of anchors, turn-buckles, fixtures, machine pads, baseplates, jacks and foundation bolts, rails etc.

2.1.1.7 Three (3), sets of Grease Lubrication System for turbine, if applicable.

2.1.1.8 Three (3), sets of Turbine pit drainage complete with submersible pumps,piping, fitting, level controllers and accessories etc.

2.1.1.9 Three (3), sets of Turbine pit monorail hoists, platforms, walkways,handrails, stairs, cover plates, access doors, acoustic barriers etc.


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2.1.1.10 Two (2), sets of draft tube plugs

2.1.1.11 Three (3), sets of necessary fittings / piping / accessories etc.

2.1.1.12 Three (3), sets of Winter Kennedy flow measurement system

2.1.1.13 Three (3), sets of fixed type online and One (1) set of portable optical typesilt measuring instruments to indicate and record the silt content of thewater passing through the Turbine.

2.1.1.14 Three (3), sets of all necessary control, monitoring, safety and meteringinstruments/devices/system including interfacing with plant SCADA.

2.1.1.15 One (1), set of Runner, Runner Cone/ Bottom ring / Guide vane / Drafttube cone / labyrinths etc. handling devices/ slings etc for dismantling ofunder water components from below.

2.1.1.16 One (1) set of runner inspection platform sectionalised into componentsincluding scaffolding which can be manually handled though draft tubemanhole door

2.1.1.17 Three (3), lot of Turbine oil, grease etc.

2.1.1.18 One lot of Spare parts in accordance to clause no. 2.8 of this section

2.1.1.19 One lot of Tools & instruments in accordance to clause no. 2.9 of thissection.

2.1.1.20 Any other items not specified above but are necessary for completion of

the Turbines.

2.2. Specific Parameters and Layout Conditions

2.2.1. Water conductor system

The main components of water conductor system are as follows:

2.2.1.1 Type of Project : Run of the River

2.2.1.2 Head Race Tunnel (HRT) Intake

Invert Level : EL 513.5M

Number and Size of entry : 1 no., 27.2mx10.8m

2.2.1.3 Head Race Tunnel (HRT)

Number : 1

Size and Shape : 9.5 m diameter, D-shaped

Length : 250m

Design Discharge : 341.16cumec


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2.2.1.4 U/S Surge Shaft

Number of Shaft & size : 1 no., Central orifice type

Shaft diameter : 22mShaft height : 21.50m

Maximum surge level : 541.0m

Minimum surge level : 526.0m

2.2.1.5 Trifurcated pressure shafts

Numbers, diameter & shape : 3 nos., 5.2m diameter, circularshape

Discharge : 113.72 cumec each

2.2.1.6 Power House

Type : UndergroundNo of Units : 3

Type of machine : Vertical Francis

Centre line of units : El. 451.5M

2.2.1.7 Tailrace Tunnel

Branch Tunnels :

Nos., Size and Shape : 3 nos., 6.35m , D- shaped

Maximum length : 120m, 125m and 140m

Main Tunnels :

Nos., and size : 1 no., 11.0m, D-shaped

Maximum length of TRT : 50m

2.2.2. Hydraulic conditions

The hydraulic conditions under which the turbine shall be operated aregiven below:

2.2.2.1 Full Reservoir Level (FRL) EL 532.0M

2.2.2.2 Minimum Draw Down level (MDDL) EL 532.0 M

2.2.2.3 Probable Maximum Flood Level EL 497.0M

2.2.2.4 Normal Tail Water Level EL 467.0M

(With all units operation)

2.2.2.5 Minimum tail water level El. 465.45M

(With one unit operation)

2.2.2.6 Extreme Minimum tail water level EL 464.0M

(Zero plant discharge)


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2.2.2.7 Head losses :

One unit in operation 1.6 m

Two units in operation 2.0 mThree units in operation 2.7 m

2.2.2.8 Operating conditions

Continuous operation depending on availability of discharge

2.2.2.9 Operating head

Rated net head 63.33m

Maximum net head 64.95 m

Minimum net head 62.30m

2.2.3 Design cons iderations

2.2.3.1 Power House Lay out

The project is envisaged as an underground power house having threevertical-shaft generating units, each comprising of a Francis turbinedirectly coupled to a synchronous generator.

Layout of power house and general arrangement of generating units andother equipment, details of water conductor system have been outlined inthe layout drawings.

The centreline of the turbine has been fixed at EL 451.5M.

2.2.3.2 Assembly and disassembly

Turbine may require frequent disassembly for repair. The Contractor shalldesign the turbine such that disassembly and assembly of the upper/lowerdraft tube cones, guide vanes, bottom ring, runner, guide vane lowerbearings etc. can be done from below the turbine without disturbing thegenerator components.

The runner, after dismantling from the turbine shaft, shall be lowered andclamped on the runner-handling cart for which suitable arrangement shallbe provided. The runner-handling cart shall be taken out under the hatchand runner shall be lifted by the power house EOT crane and be taken toservice bay at EL 467.0m. Other turbine components shall also behandled through the cart.

2.2.3.3 Special design considerations

1. The turbine and/or generating unit shall be designed to withstand theadditional stresses resulting from operation of unit with three adjacentguide vane passages in blocked condition. The Contractor shallprovide calculation to substantiate the provision in design for thisaspect during detailed engineering.


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2. The discharge ring / bottom ring shall be designed to support therunner and shaft when disconnected from the generator, if applicable.

3. The turbine guide bearing lubricating oil and governor oil shall be ofthe same specification as the generator bearing oil.

4. The turbine shall be designed for direct coupling to a 73MVA, 0.90power factor, 50 5% Hz, 166.67rpm synchronous vertical shaftgenerator.

5. Inertia constant of generating unit at rated output shall not be lessthan 4.0 kW-Sec/kVA.

2.2.3.4 Noise

The maximum noise level at any place at 1.0 m distance shall not exceed

85 dB.

2.2.3.5 Silt erosion considerations and petrographic analysis

The project is situated in Himalayan region where the silt content duringhigh flow period is excessive and peaks abnormally during high flood.Turbine may be expected to operate continuously under silt concentrationupto 6000 ppm during high flood. The petrographic analysis of silt in waterand chemical analysis of water is detailed in Section 1, Enclosure 1.

The Contractor shall critically study the silt data and chemical analysis ofwater and take the same into account in designing the turbine andauxiliary equipment susceptible to abrasive effect of silt, making all such

specific provisions.

2.3 Rating and Functional Characteristics

2.3.1 Turbine rating

Each turbine shall have a rated output of not less than 66.33MW at shaftcoupling and at rated speed of 166.67 rpm when operated at a rated nethead of 63.33m within 85% guide vane opening. It shall also be capableof delivering 110% rated output at rated net head.

2.3.2 Rated speed

The speed of the units shall be 166.67rpm in a clockwise direction whenviewed from top.

2.3.3 Pressure Rise and speed rise

The maximum pressure rise at turbine inlet, considering the effect of waterhammer under worst conditions of load acceptance/rejection and governorclosing/opening times shall be indicated by the Contractor. However, thepressure rise shall not be more than 50% of the rated head and speed


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rise shall not be more than 45% of the synchronous speed i.e., 166.67rpmunder any worst condition.

2.3.4 Runaway speed

The generating unit shall be designed to withstand the forces andstresses occurring at maximum runaway speed condition for a period of atleast thirty (30) minutes without any damage and to safely withstand anytransient over speeds.

2.4 Performance Guarantee

The generating units along with all auxiliaries and accessories shall becapable of performing intended duties under specified conditions. TheContractor shall guarantee the reliability and performance of the individualequipment as well as of the complete system.

Field tests shall form the final basis to establish fulfilment of guarantee ofthe turbine and for purposes of liquidated damages and rejection of theplant.

2.4.1 Guaranteed output

The Contractor shall guarantee the following turbine outputs at shaftcoupling at rated speed of 166.67rpm:

1. Rated output not less than 66.33MW at a rated net head of 63.33mand within 85% guide vane opening,

2. Full gate output of not less than 73MW at a rated net head of63.33m.

2.4.2 Guaranteed effic iency

The guaranteed weighted average efficiency at the rated net head shallnot be less than 93.5 percent and shall be calculated as follows:

a w=0.1 x 110+0.6 x100+0.2 x75 +0.1 x50

where,

a w = Weighted average efficiency

110 = Efficiency at 110 percent of rated outputwhen operating at net head of 63.33m





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Liquidated damages shall be imposed as per Clause 2.4.4, Liquidateddamages for shortfall in output and efficiency in case of shortfall inweighted average efficiency vis--vis the corresponding guaranteed value.

The liquidated damages on account of shortfall in weighted averageefficiency shall be computed separately for each unit and the total amountof liquidated damages shall be the sum of all the units. However,tolerance in computation of efficiency shall be in accordance with the IEC60041-1991 for field acceptance test for hydraulic turbines.

2.4.3 Cavitation pit ting guarantee

The Contractor shall guarantee that pitting due to cavitation during aperiod of 24 (twenty four) months or 8000 operating hours, which ever isearlier, from the date the unit is placed in to commercial operation, will notimpair the strength of the runner or be measurably detrimental to theefficiency or power output of the turbine.

1. For stainless steel runner

The material loss during this period shall not exceed the weightas calculated by the following formulae.

m =kD2/8000

Where: m =metal loss rate, kg/h

D =runner outlet diameter, m

k =0.6

2. For all other turbine parts combined - stay ring, guide vanes, headcover, bottom ring, discharge ring and draft tube liner.

i. an average metal loss rate, calculated by the formula above usinga value of k =0.6 on the basis of the total metal loss divided by thenumber of operating hours,

ii. Any single continuous area of 25 cm2 or larger to an averagedepth of 3 mm.

If any of the runner passages or any individual turbine componentseparately listed above fails to meet the above guarantee, the Contractorshall, at his own expense, repair the pitted area by welding and also repairin a satisfactory manner all other areas, at the same location, of otherwater passages or identical turbine components where similar damagedue to the same cause may have occurred although to a lesser extent.

The Contractor shall also make the necessary alterations to remove thecause or causes of the pitting or, if necessary, shall replace the runner.Subsequent to repair, the repaired runner and turbine components will besubject to the above pitting guarantee for another period of 8,000operating hours of power production. The guarantee will be renewed eachtime the turbine fails to meet the guarantee. Cavitation inspection will becarried out after first year or after 4000 hours of operation at which timethe Contractor can assess the amount of damage and effect minorcorrections.


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2.4.4 Liquidated damages for shortfall in output and efficiency

For any shortfall in the tested values of rated output and the weighted

average efficiency of turbine vis--vis the corresponding guaranteedvalues respectively, shall be computed as follows:

a) Output

For each one tenth of one percent(0.1%) shortfall in tested value of ratedoutput of not less than 66.33MW at anet head of 63.33m vis--viscorresponding guaranteed value

Equivalent to US$ 97,100

b) Weighted average efficiency

For each one tenth of one percent

(0.1%) shortfall in tested value ofweighted average efficiency vis--viscorresponding guaranteed value

Equivalent to US$ 97,100

For fractional values of shortfalls in percentage, the liquidated damagesamount will be computed on pro-rata basis.

The liquidated damages on account of shortfall of output and weightedaverage efficiency shall be computed separately. The total amount ofliquidated damages shall be the sum of these two multiplied by number ofturbines.

No tolerance limits shall be permissible over the calculated value of ratedoutput. However, tolerance in computation in efficiency shall be in

accordance with the IEC 60041-1991 for field acceptance tests forhydraulic turbines.

2.4.5 Rejection limit

The Employer reserves the right to reject the turbine if the tested values ofeither weighted average efficiency or the rated output (not less than66.33MW) at rated net head of 63.33m falls short by two (2) percent ormore of the corresponding guaranteed values during field acceptancetests.

2.4.6 Model acceptance tests

2.4.6.1 General

Turbine model test shall be performed in an approved test laboratory inpresence of a team of the Employer, to demonstrate that the efficiencyand other guarantees, as well as the requirements of the specifications forthe performance of the turbine, will be met.

The model test shall be conducted within nine months following the awardof the contract and six (6) hard copies of the Model Test Report and six(6) soft copies shall be submitted for perusal of the Employer.


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The tests shall be as per latest IEC test code publication No. 60193International code for Model Acceptance Test of Hydraulic Turbines. Thestep-up of the model efficiency to the prototype efficiency shall be in

accordance with IEC Publication 60995.Model test results shall be subject to the approval of the Employer and theContractor shall commence manufacture of the prototype after approvalfor the same has been accorded.

2.4.6.2 Place of model test

The laboratories proposed shall be accredited by reputed agencies. Thelist of laboratories shall be got approved from the employer beforeproceeding for the model test. Employer reserves the right to get themodel tested in any of the renowned approved test laboratory orContractors facilities/ recommended agencies by the Contractor.

In case model tests are conducted at the Contractors facilities, theContractor shall guarantee the repeatability of the results within theallowance provided in IEC. Nevertheless the Employer reserves the rightto get the model test repeated in presence of both the parties in aninternationally recognised independent laboratory at his own cost.

The Contractor shall supply his model test data, method of testing fromprevious tests and turbine model, for each component of turbine, to thelaboratory selected for conducting the tests, if it is different than theContractors facilities.

2.4.6.3 Tests to be conducted on model

The model tests shall be conducted in range of unit speeds corresponding

to 65 % to 125 % of rated headand guide vane opening corresponding tono-load to 100% guide vane opening. The guide vane positions shall besuperimposed on the efficiency contours. The model hill diagram shallshow unit flow / unit power versus unit speed or head with lines ofconstant efficiency, power, gate position and cavitation limits. Theprototype hill diagram shall show prototype power output versus headwith lines of constant efficiency, flow, gate position and cavitation limits.Prototype curves of efficiency, flow and gate position versus power outputshall be made for net heads corresponding to 65% to 125% of rated head.Guide vane torque, Axial thrust at various operating points at each guidevane opening shall be measured and plotted on model and prototype hillchart.

The cavitation limits, runaway speed characteristics, hydraulic thrust,guide vane torque and draft tube vortex phenomena shall be determinedby the laboratory tests on model.

The efficiency characteristics of the homologous turbine shall also bedetermined and the complete hill diagrams of both model and prototypeshall be incorporated in the report.

The step-up of the model efficiency to the prototype efficiency shall be inaccordance with IEC 60995.


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Runaway speed tests shall be made to determine the maximum runawayspeeds under conditions corresponding to prototype net heads with rangeof 65% to 125% of rated net heads with the guide vane opening that

produces the highest runaway speed.Guide vane torque tests shall be conducted over the full range of outputsfrom no-load to full guide vane opening and at runaway speed. Themaximum opening and closing torque on a guide vane out of synchronismwith the other guide vane shall be determined for both on-load andrunaway conditions.

The model test shall include but not be limited to the following tests:

1. Efficiency Tests

2. Determination of peak efficiency of the model and estimation of peakefficiency of the prototype,

3. Measurement of flow, hydraulic thrust and runaway speed tests atvarious openings and unit speeds corresponding to 65% to 125% ofrated net head.

4. Complete Hill chart,

5. Cavitation characteristic at various points corresponding to 65% to125% of rated net head.

6. Guide vane torque tests,

7. Verification of dimensions of various sections of spiral case, drafttube guide vanes, Runner vanes etc.

8. Runaway characteristics at various guide vane openings

The model test shall simulate all possible operating conditions of theprototype for the entire range of operation at unit speeds from 65% to125% rated head.

2.4.6.4 Model test report

After completion of the model tests, the Contractor shall submit to theEmployer six (6) hard copies and six. (6) soft copies of the model testreports for approval within one month. The test report shall include, butmay not necessarily be limited to, the following:

1. A description of the close loop test facility, test equipments and testprocedures used for model testing.

2. Sample calculations for all calculated parameters includingefficiency, cavitation and run-away speed for the model and step-upfor the prototype,

3. Comparison of test results with the guarantee requirements ofspecification/contract and technical conclusions,

4. Model test curves for:


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i. Unit power, unit discharge, efficiency versus speed for variousguide vane openings,

ii. Relation of power output, efficiency and discharge to cavitation

coefficient-sigma for various guide vane openings and speedscorresponding to the head range to be encountered in service,

iii. Relation of runaway speed to guide vane opening at the 65% to125% of the net head.

iv. Hill diagram as specified above.

5. Prototype turbine curves showing:

i. Relation of efficiency, turbine output and discharge withcavitation limits indicated,

ii. Relation of turbine discharge with guide vane opening for thehead range of 65% to 125% of the net head.

iii. Relation of runaway speed to guide vane opening for the netheads of 65% to 125% of the net head.

6. Photographs of the runner showing appearance of cavitation duringthe cavitation tests,

7. Detailed dimensional drawing of the model turbine, including therunner, guide vanes, spiral case and draft tube used for the tests,

8. A sample calculation for each computation from data to final result,

9. Record of calibration of all test instruments and equipment.

2.4.6.5 Model acceptance

1. Within 60 (sixty) days following the receipt of the model test report,the Employer will communicate his decision of the model test to theContractor. The Contractor shall commence the manufacture of theprototype only after the approval of the model has been accorded.

2. The final report shall be approved within twelve (12) months from theeffective date of the Contract, subject to its submission at least sixty(60) days earlier.

3. Should the model fail to meet the requirement of guarantee andother requirements, the Contractor shall modify the same until itcomplies with the requirements. All expenses involved for themodification and subsequent model tests shall be borne by the

Contractor.

2.4.7 Field acceptance tests

Capacity and efficiency tests shall be conducted on one turbine, chosenby Employer at a later date, to verify that the power output and efficiencyguarantees have been fulfilled.


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The power output and efficiency tests on the turbine shall be made at neteffective head as near as practicable to the rated net head. The turbinecapacity shall be determined from electrical measurements of generator

output corrected for generator losses. The generator losses shall bedetermined from the generator efficiency curves and verified bymeasurement of air cooler and bearing heat losses.

The turbine efficiency and capacity tests shall be conducted inaccordance with the provisions of IEC Publication 60041, InternationalCode for Field Acceptance Tests of Hydraulic Turbines. The test shall beconducted under the direction of a qualified independent expert to bedecided by the Employer, unless otherwise mutually agreed upon by theContractor and the Employer. The costs will be borne by the Contractor.

In addition to the field acceptance test, an Index test for Winter Kennedymethod for flow measurement shall also be performed for its calibrationafter field acceptance test in accordance with IEC.

1. To determine the performance characteristics as expressed by therelative values of power, discharge and efficiency

2. To conduct Index test to check the deterioration in performance ofthe machine with time.

2.5 Design and Construction

2.5.1 Standards

The system and equipment shall be designed, built, tested and installed tothe latest revisions of the following applicable standards. In the event ofother standards being applicable they will be compared for specific

requirement and specifically approved during detailed engineering for thepurpose:

Sl.No.

Standards Description

1. IEC 60193 Hydraulic turbines, storage pumps and pump-turbines - Model acceptance tests.

2. IEC 60609 Cavitation pitting evaluation in hydraulic turbines,storage pumps and pump turbines.

3. IEC 60041 Field acceptance tests to determine the hydraulicperformance of hydraulic turbines, storage

pumps and pump- turbines.4. IEC 60545 Guide for commissioning, operation and

maintenance of hydraulic turbines.

5. IEC 60995 Determination of the prototype performance frommodel acceptance tests of hydraulic machineswith the consideration of scale effects.


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2.5.2 Design stress limits

Design stress limits shall be as per clause 1.5.1.1 Maximum allowable

stresses of Section 1 - General Technical Requirements.

2.5.3 Material selection and standards

The material specifications and their standards for major components ofTurbine shall be as shown below. The material grade and classificationwherever specified are obligatory and proposed equivalentnational/international standard for the same shall also be considered iftheir chemical composition, mechanical properties, manufacturingmethods are similar/superior and are suitable for proposed use. TheContractor shall establish the equivalence/superiority for acceptance bythe Employer.

Sl.No. Item Material Material Standard

1. Runner

2. Runner Cone

3. Rotating labyrinth(Upper & Lower)

4. Fixed labyrinth (Upper& Lower)

5. Shaft seal sleeve/ liner

Stainless Steel,13Cr-4Ni,

ASTM A 743 GradeCA6NM or

ASTM A240 UNSS41500

6. Guide vanes Stainless Steel,13Cr-4Ni,

ASTM A 743 GradeCA6NM

7. Facing plates Stainless Steel,13Cr-4Ni,

ASTM A240 UNSS41500

8. Discharge ring Stainless Steel,13Cr-4Ni,

ASTM A240 UNSS41500

9. Bottom Ring Carbon Steel, ASTM A 537 Class II

10. Head cover Carbon Steel, ASTM A 537 Class II

11. Draft tube cone Carbon Steel, ASTM A 537 Class II

12. Spiral case Carbon Steel, ASTM A 537 Class II

13. Stay ring & stay vane Carbon Steel, ASTM A 537 Class II

14. Draft tube Carbon steel ASTM A 516 Gr. 70

15. Turbine shaft Carbon Steel, ASTM A 668 Class Dor higher class


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2.5.4 Fixed/ embedded components

2.5.4.1 Spiral case

The spiral case shall be built up from carbon steel plate .The design shallbe such that hydraulic losses are minimized.

The spiral case shall be supplied in suitable sections to suit the transportlimitations. These shall be assembled and welded with stay ring.Complete assembly shall be hydrostatically tested at site. The Contractorshall supply all consumables including electrodes and necessary testingarrangements.

Spiral case shall be concreted in depressurised condition by theContractor. Mastic sheets shall be put around the spiral case, supply ofwhich shall be in the scope of the Contractor. Perforated spiral casingdrain channel shall also be installed in this case and shall be connected to

power house drainage system. However, contractor may propose anyother alternative method / technical conditions for concreting of the spiralcasing.

The spiral case shall be designed for minimum internal design pressure of12.0 bars. Three (3) mm corrosion and abrasion allowance in thethickness of spiral casing shall be taken.

All lugs, jacks, foundation bolts, tie rods and turn buckles, bracing etc.,necessary to facilitate assembly and prevent distortion during shipping,pressure testing and concreting shall be supplied by the Contractor.

A watertight casing manhole shall be provided. The clear manholeopening shall be 750 mm wide.

Piezometer & other necessary tapings shall be provided for themeasurement of various parameters for Winter- Kennedy flowmeasurement, field test etc. The piezometer board shall be equipped withtest fittings for ultrasound tests. All piezometer pipes shall be of minimumschedule 40 and seamless stainless steel.

A drain outlet complete with heavy removable stainless steel grating,studs, nuts and cast steel body gate type drain valve with all necessaryfittings should be provided for complete drainage of the spiral casethrough draft tube.

2.5.4.2 Stay ring

Stay ring shall be of fabricated carbon steel plate or cast weldedconstruction, heat treated before final machining to relieve locked upcasting or fabrication stresses and sectionalised as necessary forhandling and shipment. It shall consist of upper and lower rings, rigidlyheld together by stay vanes, which guide the water to the guide vanes.


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For fabricated stay ring with shrouded plate design, the vanes shallprotrude through the upper and lower rings and shall be welded with fullpenetration welds. For fabricated stay rings with parallel plate design, the

stay vanes shall be welded to the flat plates with full penetration welds.The stay rings vanes shall be designed and shaped to direct the waterflow with a minimum head loss and to eliminate vibrations.

Machined flanges shall be provided for bolted connections between thestay ring and head cover, between the stay ring and the bottom ring. Thepit liner (s) shall be welded directly to the stay ring.

The surfaces of the stay ring and welded joints in contact with the watershall be ground to a smooth finish. Suitable number of holes not less than150 mm in diameter shall be provided to facilitate the placing of concrete.Suitable provision shall be made for sealing of the holes after the concreteis placed. Adequate numbers of tapped holes, 20 mm in diameter, shallbe provided for pressure grouting. After pressure grouting, plugs shall be

installed and ground flush. Air-vent holes with sealing arrangement shallbe provided through the webs in isolated pockets.

At least three drains suitably distributed in stay vanes shall be providedfrom the turbine pit through drain holes in the stay vanes. Suitableconnection should be furnished clear of the embedded parts for thecontinuation of these piping to the draft tube.

The stay ring shall be designed to transmit the required loads to theconcrete based on the design of the generating unit.

A hydrostatic pressure test of the spiral case and stay ring shall beconducted before concreting for each unit at a hydrostatic pressure of 1.5times maximum internal design pressure as per standards. Requiredquantity / numbers of testing arrangement i.e. test cylinder (s), bulkshead(s), pump motor set etc shall be provided by the contractor to meetthe schedule.

2.5.4.3 Draft tube liner

The draft tube liner shall be fabricated from carbon steel plate andadequately ribbed and stiffened to prevent distortion. The top of the linershall be machined true to level and diameter for bolting to the draft tubecone.

Sufficient number of piezometer taps shall be furnished in the liner at drafttube outlet for efficiency tests. Contractor shall supply these piezometertaps and stainless steel piping for embedment in concrete. All the

embedded piezometeric pipes shall be protected by passing the samethrough suitable larger diametric pipe.

Provision shall be made in the draft tube liner for support of beams onwhich a repair and inspection platform may be erected.


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Two dewatering pipe connection on each side of the draft tube shall beprovided at the lowest point of the elbow complete with necessary valves,to discharge unit water in to dewatering sump. The valves shall be

operable from higher elevation to be decided during detail engineering. Airpipe connection shall be provided for cleaning of the valve / dewateringpipe.

The draft tube liner shall be completely assembled and match marked inthe shop with all stiffeners, ribs etc. accurately fitted.

Sufficient number of levelling screws, jacks, anchors, turn buckles andhold-down bolts shall be provided to permit centring, levelling andsecurely holding the liner both vertically and laterally during assembly andwhile concrete is being placed.

Suitable number of holes not less than 150 mm in diameter shall beprovided to facilitate the placing of concrete. Adequate number of suitablyspaced 20 mm diameter tapped grout holes covering each grid formed byribs shall be provided to facilitate final low pressure grouting of the linerafter shrinkage of the embedding concrete has taken place. Suitable plugsshall be installed for the grout holes and ground flush after grouting iscompleted.

Minimum limit of supply of Draft Tube liner shall be 9500 mm (referdrawing no. NHKL1A4AT141GA012) from the centre line of the unit. Thevelocity at this point is envisaged to be approximately 4.0 m/sec.

2.5.4.4 Pit liner

Pit liners of heavy steel plate, with servomotor pockets, shall be provided.It shall be made in sections with welded connections as necessary for

shipment. Pit liners shall be prepared for welding to the stay ring. The linershall be adequately ribbed and substantially anchored to the surroundingconcrete in order that forces may be transmitted from the structure abovethe casing through to the stay ring without appreciable distortion of the pitliner. Contractor shall provide additional pit liner anchors in the vicinity ofthe servomotor mounting to ensure adequate support.

The upper pit liner servomotor pockets shall be welded to the pit linersection. Flanged openings shall be provided for connection to the variouspiping inside the turbine pit.

A lower pit liner, if applicable, of steel plate shall be provided for draft tubecone pit in sections with welded connection as necessary for shipment.The top of the liner shall be prepared for welding to the stay ring with full

penetration. It shall extend up to the rooftop of the runner removal galleryaccess.

Adequate number of grout holes shall be provided as specified underclause 2.5.4.3.


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2.5.5 Stationary/ removable components

2.5.5.1 Draft tube cone

Draft tube cone connecting discharge ring to draft tube shall be fabricatedfrom carbon steel plate and suitably designed to provide ease of removalfrom the turbine pit/ runner removal gallery, for dismantling of runner frombelow.

Two (2) watertight and air tight diametrically opposite manhole doors,having a clear opening of at least 750X750 mm, shall be provided in thedraft tube cone. The manhole doors shall have rounded corners, hingedto open outwards into the runner removal gallery. The hinges shall be ofrugged design and provided with an adjustment to accurately align thedoor. The inside surface of the doors shall be contoured and ground flushwith the inside of the draft tube cone. Bolts and accessories of the doorsshall be of stainless steel. A test cock, which provides a clear bore in the

open position for rodding, shall be provided in the draft tube cone belowone of the doors.

Suitable nos. of piezometer taps shall be furnished in the draft tube cone.The taps shall measure pressure at three points: two at the same leveland 180 degrees apart, and the third at a different level but in the samevertical plane as one of the other taps. The piezometer taps shall be pipedto the runner removal gallery and provided with isolating valves.

One pipe at minimum possible elevation connecting draft tube cone &drainage channel/ gallery along with the valve shall be provided for stagedewatering of draft tube below the bolting elevation of draft tube plug. Airpipe connection shall be provided for cleaning of the valve / pipe.

2.5.5.2 Head cover

The Head cover shall be fabricated from carbon steel plate. It shall be ofheavy construction, adequately ribbed and shaped so as to give rigidsupport to the turbine guide bearing, regulating ring, and the bearings forthe upper stems of the guide vanes. It shall be bolted and doweled to aflange on the stay ring and also along radial joints where the head cover issectionalized for handling and shipment.

All major stress carrying welds shall be fully penetrated and furnace stressrelieved. Radial ribs of the head cover may be fillet welded. Balancingpipes preferably with valves shall be provided for releasing the pressure inthe annular space between the runner crown and head cover. Material for

balancing pipes shall be seamless steel of at least schedule 40 ofadequate size so that the pressure remains within the acceptable limitseven with worn out labyrinths after long operations.

The head cover shall be designed to withstand safely and withoutdetrimental deflection the maximum water pressure, bearing load and allother forces acting upon it.


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The head cover assembly shall have machined seats for the turbine guidebearing, regulating ring, shaft seal, guide vanes and any other auxiliaryequipment such as air vent, pipe connections, etc. The head cover shall

be so designed as to provide rigid support for the turbine guide bearing. Aretaining ring or pads shall be furnished to prevent any lifting tendency ofthe regulating ring.

The guide seat for the regulating ring shall be provided with renewablebronze or self-Iubricating liners accurately machined so as to ensureminimum lost motion and friction in the operation of the regulating ring.Provision shall be made for supplying grease under pressure to bronzeregulating ring bearings.

Bush bearings and water cup seal arrangement for each upper guidevane stems as described in Clause 2.5.6.1 Guide Vanes and OperatingMechanism shall be provided in the head cover. Suitable drains shall beprovided for any leakage water from the seals so that water cannot collect

in the spaces between the ribs. The lower surface of the head cover shallbe accurately machined to provide a smooth surface to the water passageat the entrance to the runner.

Replaceable 13Cr-4Ni stainless steel facing plates of adequate thicknessin suitable sections shall be provided on the inner surface of the headcover and lower face of the head cover coming in contact with water.Fixing arrangement of liner shall not be susceptible to silt erosion/damage and shall be easily accessible for maintenance.

Provision should be made so that the installed runner can be movedupwards sufficiently to relieve the thrust bearing of the total rotating massduring maintenance and to remove the pads and arrangements withoutany damage/ rubbing.

A replaceable stainless steel labyrinth seal ring or rings, accuratelymachined to form a water seal with the runner crown and shaped toreduce leakage, shall be secured to the head cover. Any hydrostaticpressure build-up behind the labyrinth seal rings shall be relieved throughbuilt-in pressure relief holes. The labyrinth seal rings may be of the samecomposition as the sealing face on the runner provided it is at least 50BHN lower in hardness. Leakage of water through the labyrinth seal willbe directed to the draft tube without building pressure under the headcover.

At least four inspection holes shall be provided in the head cover to permitinspection and check on clearances of upper labyrinth of the runner. Theinspection holes shall have gasketted covers bolted to the head cover.

A minimum of three piezometer connections shall be provided on thehead cover piped to a common manifold equipped with suitable valvesand a pressure gauge. These connections shall be arranged so that radialvariations of water pressure under the head cover can be measured. Thepressure gauge will be mounted on the turbine gauge panel on the pitwall.


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Walkways around the head cover and turbine bearing shall be providedwith gratings or suitable openings to facilitate visual inspection ofequipment located below the walkways.

Adequate number of eye bolts and nylon rope slings shall be supplied tolift the head cover. Provision through suitable anchors shall be made inthe turbine pit to raise the head cover. The head cover shall be designedto pass through the wound generator in one piece during erection anddismantling and with the runner and shaft in place. Suitable access shallbe provided in the head cover for maintenance of the shaft seal withoutremoval of the head cover and to facilitate easy removal of shaft sealcomponents.

Provision of minimum 300 mm diameter or more pipes connected toturbine pit at suitable elevation and the drainage gallery should be madeto drain the top cover to avoid ingress of water into turbine guide bearingin any eventuality. This shall be in addition to the gravity drainage and

other systems.

2.5.5.3 Bottom ring

The bottom ring shall be fabricated from carbon steel plate. The weldsshall be fully penetrated and stress-relieved before final machining. Thebottom ring shall be of heavy rugged construction and all necessaryanchors and adjusting screws shall be provided. It shall be sectionalizedas necessary for handling, shipment and removal.

Bottom ring shall be so designed that it shall be possible to remove therunner by dismantling the discharge ring only without disturbing thebottom ring and guide apparatus arrangement.

Bush bearings similar to those in the head cover shall be provided for thelower stems of the guide vanes. The bottom ring shall be designed to beadequately bolted and doweled to the stay ring and discharge ring.

Replaceable 13Cr-4Ni stainless steel facing plates of adequate thicknessin suitable sections shall be provided on the inner surface of the bottomring coming in contact with water and upper horizontal surface of thebottom ring. Fixing arrangement of liner shall not be susceptible to silterosion/ damage and shall be easily accessible for maintenance.

2.5.5.4 Discharge ring

The discharge ring shall be fabricated from stainless steel plate,sectionalised as necessary to facilitate shipment and handling. The weldsshall be fully penetrated and stress-relieved before final machining. It shallbe of heavy section and adequately ribbed externally to prevent distortion.


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A replaceable stainless steel labyrinth seal ring or rings, accuratelymachined to form a water seal with the runner band, shall be secured toeither the discharge ring or bottom ring. The labyrinth seal ring shall be

designed to minimize leakage. Any hydrostatic pressure build-up behindthe labyrinth seal ring shall be relieved by the pressure relief holes. Thelabyrinth seal rings shall be of same composition as the sealing face ofrunner but 50BHN lower in hardness.

The discharge ring shall have a machined surface at the top forsupporting the bottom ring. Flanges for bolted connection to the draft tubecone at bottom shall be provided. Necessary adjusting jacks with steelbearing plates shall be furnished to facilitate levelling during erection.

Suitable arrangement shall be provided to support the runner and shaftwhen disconnected from the generator.

At least four inspection holes shall be provided in the discharge ring/bottom ring to permit inspection and check on clearances of the lowerrunner labyrinth seals. The inspection holes shall have gasketted coversbolted to the discharge ring.

2.5.6 Guide apparatus and regulating mechanism

2.5.6.1 Guide vanes and operating mechanism

The turbine shall be equipped with one set of cast stainless steel guidevanes with integral stems and trunnions. The guide vanes shall be uniformin shape, and their sections/profile shall be such as to direct properly andaccelerate gradually the water entering the runner with a minimum offriction and hydraulic disturbance.

The number of guide vanes and the number of runner vanes shall becoordinated in a manner to ensure that the turbine will operate withoutobjectionable vibrations.

The guide vane material shall be 13Cr-4Ni stainless steel. The guidevanes shall be accurately machined and ground to a smooth finish andeven surface. The tips and contact surfaces shall be machined in such afashion as to provide for uniform contact when in the closed position. Allguide vanes shall be interchangeable. The final surface finish of the guidevanes shall be in accordance with relevant latest standards.

Each guide vane shall be provided with bronze bushed grease-lubricatedbearing in the head cover and bottom ring suitable for pressure lubricationfrom the centralised turbine lubrication system or self lubricating guide

bearings shall be provided. Two bronze bushed bearings and a cup sealwith stainless steel cover plate shall be provided for each of the upperguide vane stems in head cover. Provisions shall be made for supplyinggrease under pressure from the automatic greasing system to the bronzestem bushings. Design of the greasing grooves shall ensure thatsubstantial grease pressure shall not build up under the guide vanestems, lifting them up and thus preventing operation of the guide vanes.All bolts and nuts shall be of stainless steel.


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Each upper guide vane stem shall be provided with a bronze thrustbearing or collar. Positive means shall be provided to permit the verticalclearance for the guide vanes to be adjusted from above the head cover.

Wear washers are not acceptable.The entire grease piping and connections to the lower bearing within theguide vane stem shall be tested in the shop. Check valves shall beprovided between the bearings and the grease fittings, where the bearingsare subjected to water pressure.

Guide vane stems, links, and regulating rings shall be designed toproduce a minimum of lost motion and friction. The guide vanes shall beconnected through couplings, links and levers to the regulating ring. Thelink pins shall be of the eccentric type with at least 6 mm of eccentricity tofacilitate adjustment. During tower assembly and before dowelling of theguide vanes items, the eccentric pins shall be set in such a way that all ofthe 6 mm of eccentricity is available for future adjustments. The design

shall be such that repairs and replacements can be easily and quicklymade with minimum dismantling of the turbine. The Contractor maypropose any other proven design subject to approval of the Employer.

The guide vane regulating ring shall be made of cast steel or welded steelplate, with all welds fully penetrated and stress-relieved. The regulatingring and guide vane operating mechanism shall be so designed as toremain undisturbed when dismantling and replacing the main guidebearing and accessories.

The guide vane operating mechanism shall be of ample strength towithstand the maximum load that can be imposed on it by the most severeoperating conditions. All parts having contact in motion shall be providedwith bronze bushings and with convenient means for forced grease

lubrication from the centralized lubrication system.The turbine and/or generating unit shall be designed to withstand theadditional stresses resulting from operation of unit with three (3) adjacentwicket gates passage being in blocked condition. The contractor shallprovide the calculation to substantiate the provision in design of the gatesbecome blocked.

A suitable shear pin shall be provided between each guide vane stem andthe regulating ring, and shall be strong enough to withstand the maximumoperating forces, but which will break in the event of excessive forcesacting in either the opening or closing direction and will protect the rest ofthe mechanism from damage in case one or more of the gates becomeblocked.

For detection of shear pin failure, suitable pneumatic system would beprovided to actuate an alarm in the event of breakage of a shear pin orswitches with normally closed contacts shall be provided on each wicketgate operating linkage to actuate an alarm in the event of breakage of ashear pin.


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Stops shall be provided on the head cover in front of individual guide vanelever to limit the angle of movement of the guide vane stem levers in caseof breakage of the shear pin or link so that interference of the loose guide

vane with operation of the other guide vanes or runner will be prevented.These stops shall have manual adjustment provision with which themotion of the turbine guide vanes in the opening and closing direction canbe positively limited/ restricted.

As a precaution against damage when a guide vane is free to rotate dueto breakage of a shear pin or link, the guide vane levers shall berestrained from excessive movement by means of a friction device locatedon the guide vane stem which provides a restraining force between theguide vane coupling and lever. The friction device shall be designed toresist independent movement of the guide vane for the maximumhydraulic torque at any guide vane position. The friction devicemechanism on each guide vane shall be tested during erection to ensureperformance as designed.

Any other proven arrangement in place of shear pin and shear pin failuredetection shall be acceptable subject to approval of the Employer.

2.5.6.2 Servomotors

The turbine shall be provided with two oil operated double-acting hydraulicservomotors having a combined capacity sufficient to supply themaximum force necessary to operate and hold in closed condition theguide vanes under maximum head, at the minimum oil pressure.

The servomotor shall be rigidly supported from the reinforced pads in thepit liner and shall be capable of moving the guide vanes from a completelyclosed position to a full open position in one stroke, and vice versa. Theservomotors shall be recessed into the pit liner so that the head cover canbe removed with the servomotor and piping in place.

The servomotor cylinders shall be provided with flanges for connecting oilpiping. Connections for pressure gauges shall be provided at each end ofeach cylinder. An air vent and a drain cock shall be provided on eachservomotor for draining purposes.

The servomotor cylinder shall be designed and located so that the forcefor moving the turbine guide vanes shall be divided approximately equallybetween the two cylinders and shall be applied in substantially equalmagnitude to opposite sides of the guide vanes regulating ring andtangentially to the ring.

Provision shall be made for field alignment of the servomotors, usinglevelling plates supplied by the Contractor. The servomotor flange shall bedoweled in the field to its mounting flange.


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A manual locking device of simple construction shall be provided at boththe servomotors to permit locking the guide vanes in fully closed positionsand capable of withstanding safely the full operating force of the

servomotors. Electrical contact switches shall be provided to indicateguide vanes lock in the fully closed positions. An additional contact for unitstart interlock shall be provided. All contacts shall be wired to terminalblocks in the turbine terminal box.

Servomotors shall be shop tested under a hydrostatic pressure not lessthan 150 percent of the maximum design pressure of the governor oilsystem.

2.5.7 Rotating parts, guide bearings and seals

2.5.7.1 Runner

The runner shall be made of 13Cr-4Ni stainless steel which shall be

connected to the turbine shaft in accordance with ANSI/IEEE Std 810IEEE Standard Hydraulic turbine and generator integrally forged shaftcoupling and shaft run out tolerances or applicable standard. Thecoupling shall be proposed by manufacturer as per their manufacturingstandard meeting all guaranteed parameters and proving sufficiency bycalculation. The coupling bolts shall be designed for tightening usinghydraulic tensioner/ tightening device as applicable.

The contour of the runner blades shall be accurate and shall be machinefinished so that the blade profile precisely conforms to the model designwithin the tolerance set out in IEC Publication 60193. However, in view ofhigh anticipated silt concentration runner blade thickness at outlet edgesshall be approx. 15-20% more than the optimum design. The blades shall

be evenly and symmetrically spaced. Before shipment, the Contractorshall measure the hydraulic surfaces with templates and submit proof thatthe finished runner contours and shape agree with the tested model andthe design requirements.

The surface of the runner in contact with water shall be ground to asmooth finish and even surface, without any humps or hollows. The finalsurface finish of the water passages shall be in accordance with latestInternational standard/practice. Band and crown sealing surface shall befinished to suit the stationary head cover and bottom ring seals.

The runner shall be designed to safely withstand the stresses due tooperation at runaway speed under conditions of maximum head with noload on the generator and any position of the guide vanes. Special

attention shall be paid to reduce stress concentration at the fillet of theblade outlet edge with the band and crown. The runner shall be staticallybalanced in accordance with applicable standards for large rotatingmachinery.

The runner shall be designed to support its own mass and the mass of theturbine shaft (when disconnected from the generator), with the runnerresting on the shoulder of the discharge ring.


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Replaceable 13Cr-4Ni stainless steel labyrinth seals shall be fixed to therunner both at the top and bottom ends with the help of stainless steelfasteners to reduce the leakages.

In case any labyrinth is fitted through shrinkage, at least two sets of fullarrangement of heating with heating pads, tools, slings, levellingturnbuckles etc. need to be supplied.

2.5.7.2 Turbine shaft

A turbine shaft shall be supplied by the Contractor to couple the runnerwith generator rotor. The shaft shall be made of forged carbon steelproperly heat-treated. It shall be provided with coupling flanges at top andbottom for connecting to the generator shaft, and to the runnerrespectively.

The shaft shall be hollow having a diameter of at least 150 mm through

out its entire length and shall have a general out side surface finish ofapproximately 3.2 micrometers Ra.

Suitable oil baffles and water deflectors shall be provided between themain guide bearing and the shaft seal.

Two bands shall be machined and marked on the shaft for use forverticality and alignment purposes. Additionally, one band immediatelyabove the turbine guide bearing housing location, of at least 100 mmwidth line, shall be machined on the shaft for use of non-contact typevibration pickup. The bands shall be concentric with the shaft with highsurface finish of 0.8 Ra.

The shaft couplings shall be designed as per provision of ANSI/IEEE Std810. The coupling bolts shall be designed for tightening using hydraulictensioner/ tightening device.

The turbine shaft diameter shall be coordinated with the generator shaftdiameter. The critical speed of the combined turbine and generator andgenerator rotating parts shall be calculated by the Contractor and firstcritical speed shall be at least 25% above the maximum runaway speed.

2.5.7.3 Turbine guide bearing

The turbine guide bearing for radial support of the turbine main shaft shallbe of babbited oil lubricated shell or segmented type. It shall be as nearas possible to the runner consistent with convenient access to the shaftwater seal. The bearing arrangement shall permit axial movement of the

shaft necessary for adjusting the thrust bearing and for uncoupling. Thebearing shall prevent foreign matter from entering the bearing runningsurfaces.

The bearing housing shall be made of cast steel, or welded plate steel ofheavy construction. The bearing shall be rigidly supported on the turbinehead cover. Irrespective of the material used, the bearing shall be stress-relieved before final machining operation.


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The design of the bearing and oil reservoir shall permit their inspectionand adjustment or removal without disturbing the head cover or majordismantling of other parts of the turbine. The bearing design shall be such

that no water shall enter the lubricating system via the shaft seal, andthere shall be no appreciable loss of oil by leakage past the lower oilshedder or by overflow from any part of the oil system under any conditionof normal operation, within the range of headwater and tail water elevationfrom speed-no-load to full load.

The babbitt lining on the guide bearing shell/segments shall be accordingto a grade suitable for the bearing and anchored tightly to the shell. Thebabbitt lining shall be accurately bored and shall be suitable for oilcirculation. The J ournal shall have a surface finish of minimum 0.8micrometers Ra.

Suitable lifting eye bolts and backing-out studs shall be provided for use inremoving and installing the bearing segments.

The bearing shall be capable of being operated continuously, withoutinjury, at any speed from rated speed to 110 percent rated speed; for halfan hour at any speed from 110 percent rated speed to the maximumrunaway speed. Starting at normal operating conditions, the bearings shallbe designed to operate for at least thirty (30) minutes without coolingwater without any damage to pads. The bearing system shall be designedto withstand the additional stresses resulting from operation of unit withthree adjacent guide vanes passages being in blocked condition or incase of breakage of shear pin of one or more guide vane resulting infreeness of the guide vanes at any location / angle.

The lubricating oils system shall be designed so that the temperature ofthe bearing metal and bearing oil shall not exceed 700C and 650C

respectively under continuous operation in any operating conditions. Thelubricating oils system shall have sufficient capacity to supply the requiredamount of oil to the turbine guide bearing, and the oil reservoir shall havesufficient capacity to hold all the oil in the entire bearing system, and toprovide cool oil to the bearing under conditions of loads. The bearingdesign shall prevent the leakage of oil down along the shaft and shallprovide for returning oil from the bearing to the reservoir. Separate pipingfor filling and draining the bearing from reservoir shall be provided.

If cooling of the lubricating oil is necessary, a heat exchanger of 90:10cupro-nickel coils shall be provided and shall be completely immersed inthe oil. All connections to the coils shall be made outside of the oilreservoir and arranged so that water from a leaky connection cannot drip

into the bearing oil reservoir. The coils shall be arranged to permitremoval without dismantling the bearing. The coils shall be free fromleakage when tested in the shop under a pressure of 10.0 bars for aperiod of 1/2 hour. The arrangement shall be subject to Employersapproval at design stage. To regulate the quantity of water flow in the coilsa suitable valve shall be provided in the discharge line of the heatexchanger.


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The Contractor shall supply and install the following indicating andprotection devices for the turbine guide bearing. All electrical contactsshall be wired to terminal locks in the turbine terminal box.

a) Three (3) or more numbers of DTT, liquid expansion typethermometer, two in case of shell and four or more equally spaced incase of more no. of segments for bearing metal and one in bearing oilfor bearing oil temperature indication shall be provided. The devicesshall have two sets of separately adjustable contacts for alarm andtripping circuits.

b) Resistance temperature detectors (RTDs) - one in each segment/ padfor bearing metal and two in the bearing oil for bearing and oiltemperature indication and recording at a remote location. (The leadextension cables to the terminal box and 3-wire twisted cable shall besuitably shielded. Separate terminals shall be provided in the terminalbox for terminating the shields of individual RTD lead extension

cables.) At least two of the above RTDs shall be configured for rate ofrise of temperature.

c) One electromagnetic induction type flow-meter with two electricallyseparate low-flow alarm contacts and recording at remote location forthe bearing cooling water supply, if cooling water is required.

d) One direct visual indicator of the bearing oil level marked in litres andhigh and low level and oil level relay along with adjustable high andlow level alarm contacts.

e) One oil-water contamination detector,

f) Resistance temperature detectors (RTDs) to measure of thetemperature of the incoming and outgoing water from the turbineguide bearing coolers, if cooling water is required.

g) Temperature indicator for local temperature measurement of theincoming and outgoing water from the turbine guide bearing coolers, ifcooling water is required.

h) Pressure gauges at inlet and outlet of the turbine guide bearing coolerwith low pressure alarm contacts.

2.5.7.4 Shaft seals

The Contractor shall provide two (2) shaft seals, one as main working sealand another as maintenance seal. The turbine sealing proposed by theContractor shall be of special design. The arrangement and design ofthese seals shall be such that they remain fail proof even while the turbineis operating in water having high silt concentration and the maximumleakage shall be guaranteed by the Contractor. The seal shall be axial,water lubricated hydro dynamically balance and automatic self adjustingtype. The seal should be able to sustain at least 15000 hours even ifmachine is operated upto 10000ppm of silt concentration during monsoon.Contacting seal rings shall be tough and wear resistant.


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All components shall be hydraulically designed to meet the maximum andminimum pressure conditions required by the application. However, thearrangement defined shall be as accepted by the Employer at the time of

award of contract/ detailed engineering.Arrangement of main working seal shall be such that it prevents any waterentry into the bearing through the leakage along the shaft. The shaft sealshall be arranged for water lubrication. Two or more connections for watershall be provided, evenly spaced on the periphery to admit supply of cleanwater at a pressure sufficient to exclude foreign matter from the seal. Anyleakage water from the seal shall be removed by drains. The seal shall beso arranged that it may be serviced without disturbing the bearing ordewatering the draft tube.

A maintenance seal shall be provided below the main working seal toallow the main seal segments to be serviced without dewatering the spiralcasing. This maintenance seal shall prevent leakage along the shaft when

the turbine is stationary.Water for shaft sealing shall be drawn from the tail race through at leastDN 300 embedded pipe (common suction pipe for shaft seal and HVACSystem) by pumps and shall be suitably cleaned and filtered beforesupplying to the shaft seal at a suitable pressure as per Schematic flowdiagram no. NH/DEM/KTB-1A/CW/01.

Suitable lifting eye bolts and backing-out studs shall be provided for use inremoving and installing the shaft seal parts.

The Contractor shall provide the necessary piping and the valves,including pressure reducing valves, filters, piping and fittings within theturbine pit, terminated by unions or flanges at a point outside the turbinepit.

All bolts, nuts, screws and hardware used in connection with the shaftwater seal shall be of stainless steel.

The Contractor shall supply and install the following indicating andprotection devices for the shaft seal for local and remote monitoring atDCS level. All electrical contacts shall be wired to terminal locks in theturbine terminal box.

a) An electromagnetic induction type water flow meter with adjustablealarm contacts shall be provided in the water supply piping to the sealfor local and remote indication. Additional contact shall be provided tooperate an indication light in the gauge panel to indicate that shaftseal water is ON.

b) Wear indicator and position switch to enable local and remotemonitoring/indications of seal face wears.

c) Pressure gauge shall be provided to indicate the difference inpressure between water supply line and beneath the shaft seal.

d) Pressure gauge and pressure transmitter shall be provided to indicatethe water pressure in the water supply line for local and remotemonitoring respectively.


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e) Temperature indicator and temperature transmitter shall be providedfor local indication and remote measuring of water temperature belowshaft seal.

f) Pressure gauge and pressure switch shall be provided to indicate theair pressure of maintenance seal and seal engage indication.

2.5.8 Auxili ary systems and miscellaneous components

2.5.8.1 Grease lubrication system

In case of applicability, to ensure proper lubrication of all parts requiringforced grease lubrication, the Contractor shall furnish grease lubricationsystem for each turbine. It shall be used to supply grease to variousgreasing points of turbine automatically at required interval. It shallcomprise lubricant reservoir, motor operated grease pump, grease piping,valves, fittings, dozers, timers, pressure controls and control panel,

complete in all respects.

One number manually operated pump for greasing the points when theautomatic system is not in operation shall also be supplied.

One electrically operated transfer pump to supply grease from commercialstandards drums to the reservoir of the automatic grease lubricationsystem shall be supplied.

The system shall be capable of developing 210 bars grease pressure atthe entry to every bearing under all conditions. The frequency of thegreasing cycles shall be decided to suit the operating conditions.

Alarm switches shall be provided to indicate low-lubricant level, nolubricant supply and high pressure. Alarm contacts shall be provided for

remote indication of a blocked line bearing or feeder, or no flow oflubricant when selected by the timer, and for low grease level in thecontainer.

2.5.8.2 Turbine pit drainage

Turbine pit shall be designed in such a way that in case of flooding, theaccumulated water is drained through gravity drain to prevent flooding ofthe turbine guide bearing.

For normal operation, one main and one standby AC motor drivensubmersible pumps with automatic controls and lead-lag selectors shallbe provided to drain head cover water leakage.

All the above pumps will be regulated/operated depending on the waterlevel sensed by float type level switches. Indications such as pumpstart/stop, pump-motor in electrical/ mechanical fault, high level alarm andlow level alarm shall be provided.


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2.5.8.3 Air admission system

An automatic air admission valve of suitable size, which shall be decided

during detailed engineering, shall be provided for admission of air throughopenings through the generator/turbine shaft to the runner cone, to permitsmooth operation of the unit throughout its operating range and especiallyduring part load operations.

An air head shall be provided by the Contractor on top of the generatorrotor to prevent tail water from entering the air vent piping. The air headshall be connected to air vent piping. The design of the air head andpiping should be coordinated with the generator design. The design of theair head shall be such that the same can be inspected and maintainedwithout disturbing the generator assembly.

2.5.8.4 Walkways, access platforms and stairs

Working, operating and inspection walkways and platforms, complete withfloor gratings, stairs and handrails shall be rust free and, shall befurnished in the turbine pit to provide convenient and safe access to alloperating equipment and points of lubrication. The design of the floorgratings, stairs and handrails shall be rust free and shall facilitate easyremoval to permit free access to the turbine.

The platform around the shaft shall be designed to support the weight ofturbine guide bearing.

2.5.8.5 Turbine pit hois t

Each turbine pit shall be equipped with the necessary lugs and circular

monorails with dual hoist (one at PCD of upper bearing bodies and otherat TGB housing) to facilitate easy replacement of all equipment inside thepit.

2.5.8.6 Access door to turbine pit

The turbine shall be provided with a metal acoustic access door to beinstalled in the turbine pit concrete wall. The door shall have suitablehandles and inside panic release bars.

2.5.8.7 Acoust ic barrier for runner removal gallery

The general area at floor at EL 445.0m shall be acoustically isolated from

runner removal gallery by providing acoustic shutter.The shutter shall be of vertical leaf type having suitable number of leavesto close the openings. Door frames/guides and sill beams shall be flushedto concrete. The door shall be operated through electric motor and shallbe lifted to a vault above the gallery provided for the same. Ball/rollerbearings shall be provided for smooth passage through the guides.


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The leaves shall be made of lightweight acoustic material and shall becorrosion, water and vermin proof. The lowest leaf shall have a door forroutine inspection and arrangement shall have an aesthetic look.

2.5.8.8 Nameplate

A rating nameplate of stainless steel shall be attached to each major andauxiliary item of equipment supplied. This plate shall be permanentlyengraved with the designed full load ratings, serial number, type number,date of manufacture and other identification deemed necessary. Hydraulicand electric control system diagram plates shall also be supplied. Theidentifying inscription shall be approved by the Employer.

2.5.9 Control and monitor ing

The turbine and associated accessories/equipment shall be controlled and

monitored at three levels:1. By respective local control cubicles,

2. By respective Unit Control Boards,

3. By computerized control and monitoring (SCADA) system throughUnit Control Boards.

The details of control and monitoring requirement are defined in Section13 - Computerized Control and Monitoring System and Section 14 -Protection System.

The Contractor shall make provision of contacts and/or ports in localcontrol cubicles for interfacing with SCADA system for control andmonitoring.

Local control shall be performed in an independent and standalonemanner, and all information (faults, alarms, measurement, status)necessary for such control shall be displayed locally.

If the system consists of redundant subsystems, the priority of operationof such subsystems shall be selectable either from SCADA system orlocally.

2.5.9.1 Instrumentation

The Contractor shall include suitable instruments, gauges, switches,contacts for achieving desired control and monitoring as defined inSections 13 - Computerized Control and Monitoring System andSection 14 - Protection System.

List of instruments to be furnished with their location is given in Tablebelow. However, the list is indicative only and scope/type shall be as perapproved drawings/bill of materials during detail engineering.


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Sl.No.

DESCRIPTION TYPE OF INSTRUMENT QUANTITY

1. Penstock

a. Turbine Discharge Winter Kennedy flowmeasurement

1

2. Turbine water path

a. Head cover pressure Indicating PressureGauge and pressuretransducer

1

b. Runner downstreampressure (draft tubecone)

Indicating PressureGauge

1

c. Draft tube exitpressure

Indicating PressureGauge

1

d. Shear pin for guidevane Normal / Break

pneumatic system/switch

As perapprovedscheme

3. Turbine bearing

a. Turbine bearing

metal temperature

Dial type thermometer

with adjustable contacts

2/4 in shell

segment/pad

b. Turbine bearingmetal temperature

Resistance temperatureDetector

1 in eachshellsegment /pad

c. Turbine bearing oiltemperature

Dial type thermometerwith adjustable contacts

1

d. Turbine bearing oiltemperature

Resistance temperaturedetector

2

e. Turbine bearing

cooling water outlettemperature

Resistance Temperature

detector

1

f. Turbine bearingcooling water inlettemperature

Resistance temperaturedetector

1


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g. Turbine bearing oillevel relay

Indicating gauge withhigh and low levelcontacts

1

h. Float type oil levelgauge

Indication for high andlow level

1

i. Turbine bearingcooling water flow

Electromagnetic typeflow meter with low flowalarm contacts

1

j. Turbine bearingcooling waterpressure at inlet andoutlet

Indicating pressuregauge at inlet and outletand pressure transducerat outlet

2 gaugesand 1pressuretransducer

k. Turbine bearingcooling water

temperature at inletand outlet

Indicating thermometerand resistance

temperature detector

2

l. Water in oil detector Moisture detector 1

4. Guide Apparatus

a. Guide vane positionindicator

LVDT mounted onservomotor

1

b. Servomotormechanical lockedposition detector

Position indicatormounted on eachservomotor with contacts

1

5. Turbine shaft sealsystem

a. Shaft seal flow andlow flow alarm

Electromagnetic typeflow meter with low flowalarm contacts

1

b. Shaft Seal waterpressure in watersupply line andbeneath the seal

Indicating pressuregauge

1

c. Shaft seal waterpressure in the watersupply line and lowpressure alarm

Indicating pressuregauge with contacts &Pressure transducer

1


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d. Water temperaturebelow shaft seal

Temperature indicatorand resistancetemperature detector

1

e. Shaft maintenanceseal

Indicating pressuregauge & Pressureswitch

1

2.5.9.2 Winter Kennedy method

Each turbine shall be provided with Winter Kennedy apparatus in thespiral case for continuous on-line monitoring of flow through the turbine.The required apparatus shall be installed permanently in the waterpassage for each unit. The equipment shall be as per IEC 60041-1991.

The flow meter system supplied shall include all the equipment andinterconnecting wiring required to measure the flow rate for display andprinting the measured values.

2.5.9.3 Vibration monitor ing system

Vibration monitoring system has been defined in section 5 Generator.The Contractor shall make provisions for mounting of probes/transducersat desired location defined below:

1. Two (2) nos. non-contact type proximity probes at turbine guidebearing to measure radial vibration in both axes,

2. Two (2) nos. contact type probes at turbine guide bearing housing to

measure bracket/housing vibration,3. Synchronization probe.

2.5.9.4 Over speed device

The Contractor shall furnish a centrifugal type over speed device withprovisions for electrical and mechanical tripping, on the shaft of eachturbine above the guide bearing. The mechanical tripping device willdirectly actuate the governor shutdown valve though a hydraulicconnection, in case of turbine speed exceeding preset limit. It shall befurnished complete with rotating and stationary trip mechanism, guards,connection to inlet valve control, and necessary supports. The mechanismshall be completely mechanical or oil-hydraulic and not dependent onelectrical equipment for its operation. However, two electrical independentungrounded changeover contacts shall be provided for alarm and initiatinggovernor shutdown.


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2.5.9.5 Silt measuring ins truments

The Contractor shall furnish optical on line silt measuring instruments to

indicate and record the silt content of the water passing through the drafttube. The silt measuring instruments shall be capable of measuringinstantaneous silt content in parts per million (ppm) by volume, with errornot to exceed +/- 2 %. Output shall be indicated on digital indicator, withserial output for SCADA system.

2.6 Drawings, Documents and Design Calculations

2.6.1 Design memorandum

The Contractor shall submit to Employer a design memorandum preparedin accordance to clause 1.6 Record and Documentation of Section 1-General Technical Requirements.

2.6.2 Drawings and documents

The Contractor shall submit all the drawings and documents inaccordance with requirements stipulated in Section 2 - TechnicalDocuments of General Technical Specification (GTS).

2.6.3 Design calcu lation

The Contractor shall submit the design calculation in accordance toClause 2.4 of General Technical Specification (GTS) covering at leastthe following, for review / acceptance.

1. Stress analysis of stay ring, spiral case, head cover, bottom ring,

discharge ring, bearing, draft tube elbow, draft tube cone and pitliners,

2. Stress analysis of runner, turbine shaft and coupling bolts,

3. Critical speed and bearing arrangement,

4. Hydraulic transient analysis including speed and pressure rise,

5. Draft tube elbow and draft tube cone surge frequency,

6. Natural frequency of the unit,

7. Heat exchanger / temperature rise calculation for turbine guidebearing.

8. Calculation of foundation loads under various normal and mostabnormal operating conditions for turbine components.

2.7 Delivery, Installation and Commission ing

The Contractor shall follow the requirements of Delivery, Installation andcommissioning elaborated in clause 1.7 Delivery, Installation andcommissioning of Section 1 - General Technical Requirements.


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2.8 Spare Parts

Recommended spare parts shall be supplied in accordance to clause 1.8

Spare Parts of Section 1 - General Technical Requirements. Specifiedspare parts to be supplied under this section are as follows:

S. No. Descrip tion Quantity

1 Runner complete with moving labyrinthseals complete with hardwares, as perapplicability, runner cone and fixing bolts.

1 no.

2 Set of coupling bolts and keys( ifapplicable) runner to turbine shaft

1 set

3 Coupling bolts turbine shaft to generatorshaft

1 set

4 Labyrinth seals Upper including fastenersFixed labyrinth seals

Moving labyrinth seals

3 sets

3 sets

5 Labyrinth seals Lower including fasteners

Fixed labyrinth seals

Moving labyrinth seals

3 sets

3 sets

6 Liner/facing plates for top cover includingfasteners

3sets

7 Liner/ facing plates for bottom ring includingfasteners

3 sets

8 Complete set of guide vanes 2 sets

9 Shaft seal segments 3sets

10 Set of Shaft seal sleeve 2 nos.

11 Turbine guide bearing segments/ padscomplete set

1 set

12 Guide apparatus

12.1 Bushes for top, middle and bottom stems ofguide vanes

2 sets each

12.2 Guide vane servomotors LH and RH 1no. each

12.3 Shear pins 2 sets

12.4 Bushes for regulating mechanism 2 sets

12.5 Key laid / key driven , if applicable orrelevant part

2 sets each

13 Set of turbine head cover water leveldetector

2 nos.


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14 Turbine head cover pump-motor(Submersible)

2 nos.

15 Grease Lubrication System (if applicable)

15.1 Grease pump with motor 1 no.

15.2 1 set of reservoir including grease pipe,main NRV, dozers, filters and feeders

1 no.

16 DTT (Dial Type Thermometer) /thermometer

6 nos.

17 RTD ( Resistance Temperature Detector) 8 nos.

18 Water flow meter/ switch of each type 2 nos.

19 Pressure gauges of each type 2 nos.

20 Pressure switch / pressure transmitter of

each type

2 nos.

21 Oil level gauges of each type 2 nos.

22 Valves of size 80 mm and above includingpenstock drain valve

1no. of eachused type

One set defines total quantity used in one turbine.

2.9 Tools and Instruments

The Contractor shall supply all necessary tools and instruments etc. forinstallation, repair and maintenance in accordance to clause 1.9 Toolsand Instruments of Section 1 - General Technical Requirements.

2.9.1 Special tool s

The Contractor shall list and supplyall special tools. List of such toolsincluding their make and detailed specification, shall be submitted foracceptance by the Employer.The proposed list of special tools mustinclude the following in addition to tools recommended bymanufacturer(s);

1) One (1) set of hydraulic torque tensioners with two identical tensionersoperated by a common power pack for runner/ turbine shaft flangecoupling bolts, as per applicability

2) One (1) set of hydraulic torque tensioners with two identical tensionersoperated by a common power pack for turbine shaft/ generator flangecoupling bolts

3) One (1) set of hydraulic wrenches each type of bolt size viz. headcover , bottom ring, runner cone bolts, labyrinths , draft tube conebolts etc. used in the plant.


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4) One (1) set of runner blades templates .

5) One (1) set of guide vanes templates

6) One (1) set of different size of Nylon Sling - round, for handling headcover, bottom ring, draft tube cone, guide vane and other turbinecomponents

7) One (1) set of Nylon Sling - Flat, for handling head cover, bottom ring,draft tube cone, guide vane and other turbine components

8) Four (4) no. of Eye Bolts of each size (M20 or above) for handling ofturbine components

9) Four (4) no. of D- shackles of each size (M 20 or above) for handlingof the turbine components.

2.10 Quality Assurance and Testing

The Contractor shall follow the quality assurance and testing requirementsspecified separately in Quality assurance and Testing Specifications(QTS).

2.11 Hard Coating (Optional item)

As the project is situated in Himalayan region due to which underwaterparts of the turbine might get eroded on account of high silt laden water asper the informative PTS clause no. 2.2.3.5. It would be better, if thecoating is repairable. It is envisaged to have suitable HP-HVOF hard

coating on the underwater surfaces on the areas as per below:1. Wicket Gate

a. Lower trunnion complete

b. Upper trunnion atleast 200mm above the guide vane collar

c. Top & bottom mating surfaces with top cover and bottom ring liner

d. Feather portion complete

2. Runner and moving labyrinths

a. Top (crown inlet) and bottom (band inlet) peripheral surfaces

b. Pressure and suction side of the blade in complete height and

complete lengthc. Complete water passage between the blade at crown and skirt in

complete length

d. Top and Inner surfaces of moving labyrinth seal (upper) exposedto the water.

e. Top and Inner surfaces of moving labyrinth seal(lower) exposed to the water.

2.Turbine and Accessories

Documents

Transcript of 2.Turbine and Accessories