Brief Introduction of SH/MH ComponentsBrief Introduction of SH/MH Componentsand and

Civil Engineering aspects of SH/MHCivil Engineering aspects of SH/MH

Janak Das KoiralaJanak Das KoiralaTreasurer Treasurer -- Nepal Micro Hydro Power Development Association Nepal Micro Hydro Power Development Association

(NMHDA)(NMHDA)Executive Director Executive Director -- AG Power Company P. Ltd.AG Power Company P. Ltd.

Executive Director Executive Director -- DAT Engineering Consultancy P. Ltd.DAT Engineering Consultancy P. Ltd.

INTRODUCTIONINTRODUCTIONA Micro Hydro (Or A Small Hydro) Power Project Is A System Of ElA Micro Hydro (Or A Small Hydro) Power Project Is A System Of Electricity Generation By ectricity Generation By

Water Driven Forces And Power Is Supplied To Villages/Cities ForWater Driven Forces And Power Is Supplied To Villages/Cities For Different Uses.Different Uses.

Generally Hydro Energy From MHP Is Basically Used For LighteningGenerally Hydro Energy From MHP Is Basically Used For Lightening..

Diesel Type Mills For Grain Grinding, Rice Hulling Etc. Are ReplDiesel Type Mills For Grain Grinding, Rice Hulling Etc. Are Replaced By Electrical Driven aced By Electrical Driven

Type.Type.

History of Micro hydro in Nepal History of Micro hydro in Nepal -- since 1960 after establishment of Balaju Yantra Shala since 1960 after establishment of Balaju Yantra Shala

assisted by Swiss and at the same period United Mission to Nepalassisted by Swiss and at the same period United Mission to Nepal (UMN) support also (UMN) support also initiated.initiated.

Water Mills were used extensively during 1970.Water Mills were used extensively during 1970.

Private Manufacturing Companies spread up in eighties.Private Manufacturing Companies spread up in eighties.

Contd..Contd..

Most of the equipments/components e.g.. Gate Valves, Turbines, TMost of the equipments/components e.g.. Gate Valves, Turbines, Trash rash

racks, MS Pipes for penstocks, Conductors and Load Controllers aracks, MS Pipes for penstocks, Conductors and Load Controllers are in re in general locally manufactured in Nepal.general locally manufactured in Nepal.

Generators are imported from abroad especially from India and ChGenerators are imported from abroad especially from India and China, and ina, and also from Europe in some cases.also from Europe in some cases.

Standardization started in late eighties.Standardization started in late eighties.

Intermediate Technology Development Group (ITDG) and AgriculturaIntermediate Technology Development Group (ITDG) and Agricultural l

Development Bank Nepal (ADB/N) contributed for enhancement of Development Bank Nepal (ADB/N) contributed for enhancement of technological base of the micro hydro installations in the counttechnological base of the micro hydro installations in the country.ry.

After establishment of Alternative Promotion Centre quality aspeAfter establishment of Alternative Promotion Centre quality aspects of micro cts of micro hydro power project has been given more emphasize and standards hydro power project has been given more emphasize and standards has has

been established in survey, design, manufacturing/fabrication anbeen established in survey, design, manufacturing/fabrication and d

installations steps.installations steps.

Small Scale Water Power SchemesSmall Scale Water Power Schemes

S.N. Type of Scheme Capacity

Power supply System

Isolated Grid

1 Full Scale hydro >10MW

2 Mini Hydro Scheme300KW- 10

MW

3 Micro Hydro Scheme

Nepal hydro power Nepal hydro power

S.N.S.N. SizeSize CategoryCategory

11 Project < 5kwProject < 5kw Pico Hydro Pico Hydro

22 100 kw > Project > 5 Kw 100 kw > Project > 5 Kw Micro HydroMicro Hydro

33 100Kw > Project > 1 MW100Kw > Project > 1 MW Mini HydroMini Hydro

44 10MW > Project > 1 MW10MW > Project > 1 MW Small HydroSmall Hydro

55 Project > 10MWProject > 10MW Large HydroLarge Hydro

What we do in design of a MHP?What we do in design of a MHP?

Layout Design:Layout Design:We Specify the locations, sizes, materials, and other We Specify the locations, sizes, materials, and other parameters of all civil engineering structures/components that parameters of all civil engineering structures/components that are to be constructed or installed at the site. are to be constructed or installed at the site.

Design of Electro Design of Electro Mechanical EquipmentMechanical EquipmentWe determine the sizes, types of Electrical and Mechanical We determine the sizes, types of Electrical and Mechanical equipments, depending up on the proved science and equipments, depending up on the proved science and engineering laws as well as national and international engineering laws as well as national and international guidelines and practiced guidelines and practiced

Economical and financial AnalysisEconomical and financial AnalysisWe determine the financial viability of the project by determiniWe determine the financial viability of the project by determining ng some financial indicators like B/C Ratio, Net Present Value some financial indicators like B/C Ratio, Net Present Value (NPV), Internal Rate of Return (IRR) etc. (NPV), Internal Rate of Return (IRR) etc.

Operation and Maintenance Operation and Maintenance Designer should mention the level of human resources, spare Designer should mention the level of human resources, spare parts required, frequency of maintenance of different type of parts required, frequency of maintenance of different type of equipments etc. in the design report.equipments etc. in the design report.

Ideal DesignIdeal DesignOptimize the use of resources.Optimize the use of resources.

An ideal design should be such that based on it an experienced iAn ideal design should be such that based on it an experienced installer should be nstaller should be able to construct the scheme independently of, with only nominalable to construct the scheme independently of, with only nominal assistance from, assistance from, the designer. the designer.

Conclude the findings and recommend to the concerned parties Conclude the findings and recommend to the concerned parties developer, donor, developer, donor, approval committee etc. for required action.approval committee etc. for required action.

Base for designBase for designThe design of the scheme is based primarily on the information oThe design of the scheme is based primarily on the information obtained during the btained during the various surveys. Therefore, it can only be as good as the resultvarious surveys. Therefore, it can only be as good as the results of surveys.s of surveys.

The design process is iterative since the dimensions and other pThe design process is iterative since the dimensions and other parameters of the arameters of the MHP components are interdependent.MHP components are interdependent.

Design guidelinesDesign guidelinesVarious organizations and institutions has developed Various organizations and institutions has developed design guidelines incorporating the national and design guidelines incorporating the national and international standards, country situation, enhancing international standards, country situation, enhancing available indigenous technology etc. available indigenous technology etc. Example Example Micro Hydro Design Manual Micro Hydro Design Manual by Adam by Adam Harvey Harvey ITDGITDGDetail Feasibility Study and Design Guidelines Detail Feasibility Study and Design Guidelines AEPC, NepalAEPC, NepalManual for Decentralized Distribution & Generation Manual for Decentralized Distribution & Generation Projects (Based on Community Participan) Projects (Based on Community Participan) Uttaranchal Renewable Energy Development Agency Uttaranchal Renewable Energy Development Agency (UREDA), India(UREDA), IndiaEtc. Etc.

MHP Project Cycle in Nepal/AEPCMHP Project Cycle in Nepal/AEPC

1.1. Request for survey by entrepreneur/communityRequest for survey by entrepreneur/community2.2. PrePre--feasibility study by prefeasibility study by pre--qualified consultants qualified consultants

Quality Check by AEPCQuality Check by AEPC3.3. Detailed feasibility study Detailed feasibility study Consultants: QC Consultants: QC --AEPCAEPC4.4. Subsidy Approval Subsidy Approval Further QC Further QC -- AEPCAEPC5.5. Project construction: PQ installation companies & Project construction: PQ installation companies &

manufacturers manufacturers QC by independent InspectorsQC by independent Inspectors6.6. Power verification Power verification QC by Indpnt. Inspector.QC by Indpnt. Inspector.7.7. 1 year warranty check 1 year warranty check QC (Indpnt. Inspctr)QC (Indpnt. Inspctr)

CIVIL COMPONENTSCIVIL COMPONENTSIntakeIntakeWeirWeirSpillwaySpillwayDesilting BasinDesilting BasinHeadrace Canal/ PipeHeadrace Canal/ PipeForebayForebaySupport StructuresSupport Structures

Support PiersSupport PiersAnchor blocksAnchor blocks

Machine FoundationMachine FoundationPower HousePower HouseTailraceTailrace

NForbay

Tailra

ce

Penstock Pipe

Power House

WEIR

Spilw

ay

Canal

River/Khola

Spilw

ay

Anchor Block

Anchor Block

Support Pier

Kholsa

Crossing

Headrace CanalDes

ilting Ba

sin

Major Civil Components Of Micro Hydro Scheme

n3n3'' hnljBhnljB''t cfof]hgfsf l;lent cfof]hgfsf l;len ;+/rgfx?;+/rgfx?

Intake

Weir

Desilting

Basin

Canal

CrossingForebay

Anchor Block

Support Piers

Power House

Tailrace

Source

Spill way

Trashrack

Spillway

Civil Components of Micro HydroCivil Components of Micro Hydro

Diversion WorksDiversion WorksThe diversion works of a microThe diversion works of a micro--hydropower scheme hydropower scheme control the flow control the flow of water from the source river in to the headrace.of water from the source river in to the headrace.The diversion structures comprise The diversion structures comprise a diversion weir, a diversion weir, an intake, and sometimes an intake, and sometimes Some river training works.Some river training works.

Collectively the diversion works together with a gravel trap andCollectively the diversion works together with a gravel trap andspillway is termed as spillway is termed as Headwork.Headwork.

Diversion WeirDiversion WeirA diversion weir is a low structure (small dam) placed across thA diversion weir is a low structure (small dam) placed across the e river which diverts the river flow safely in to the hydropower sriver which diverts the river flow safely in to the hydropower system ystem through side intake.through side intake.The weir can be of a permanent, semi The weir can be of a permanent, semi --permanent or temporary permanent or temporary nature.nature.The main function of a weir is to ensure that the channel flow iThe main function of a weir is to ensure that the channel flow is s maintained with the river in low flow period.maintained with the river in low flow period.

Function of Diversion worksFunction of Diversion works-- Maintain the design flow with nominal head Maintain the design flow with nominal head losses during both monsoon and dry seasonlosses during both monsoon and dry season-- prevent, or at least minimize, the bed load prevent, or at least minimize, the bed load and other floating material entering the canaland other floating material entering the canal-- safely contain peak flows in the river and safely contain peak flows in the river and away from the microaway from the micro--hydro system so that hydro system so that damage is not caused to the structures.damage is not caused to the structures.

Diversion Weir contdDiversion Weir contd

Site selection Site selection General General rules/principles:rules/principles:

Extraction of water from the river in a reliable Extraction of water from the river in a reliable and controllable way and controllable way Use natural features of river if possible . eg. Use natural features of river if possible . eg. Natural Permanent pool in the river may provide Natural Permanent pool in the river may provide the same function as a weir.the same function as a weir.Adopt traditional management known to local Adopt traditional management known to local peoplepeopleAdopt traditional method of construction of Adopt traditional method of construction of temporary weirs as far as possible.temporary weirs as far as possible.Generally, It should be located 2Generally, It should be located 2--10 m 10 m downstream of the intake depending on the site downstream of the intake depending on the site conditions.conditions.Should be located at a narrow part of the river Should be located at a narrow part of the river

Temporary WeirTemporary WeirTemporary weir is constructed using boulders available at the siTemporary weir is constructed using boulders available at the site, te, stone masonry in mud mortars placed across a part or all of the stone masonry in mud mortars placed across a part or all of the river river width.width.This is the traditional method used by Nepali farmers and quite This is the traditional method used by Nepali farmers and quite extensively used in micro hydro schemes in Nepal.extensively used in micro hydro schemes in Nepal.It is simple and low cost but it is not possible to divert all oIt is simple and low cost but it is not possible to divert all of the river f the river flow in dry season by this structure.flow in dry season by this structure.It is suitable only for the diversion of flows below 1 m3/secIt is suitable only for the diversion of flows below 1 m3/sec

Semi Permanent WeirSemi Permanent WeirGabion structures can be use as semi permanent weir.Gabion structures can be use as semi permanent weir.If there is no significant boulder movement along the river streIf there is no significant boulder movement along the river stretch at the tch at the intake area, it may be effectiveintake area, it may be effectiveIt can tolerate some ground movement without significant damage It can tolerate some ground movement without significant damage on on its bodyits bodyAs the gabion wires are more vulnerable to damage by moving As the gabion wires are more vulnerable to damage by moving boulders, it cannot used in the steep streams, which carry such boulders, it cannot used in the steep streams, which carry such boulders.boulders.Seepage can be control by using an impermeable membrane.Seepage can be control by using an impermeable membrane.

Diversion Weir contdDiversion Weir contd

Permanent weirPermanent weir If flow is limited during dry season and river does not carry laIf flow is limited during dry season and river does not carry large boulders rge boulders

permanent weir may be built across the river.permanent weir may be built across the river. These are constructed of mass concrete, stone masonry in cement These are constructed of mass concrete, stone masonry in cement mortar and mortar and

using plum concrete.using plum concrete. A reinforced concrete surface layer may be provided to protect tA reinforced concrete surface layer may be provided to protect the weir body he weir body

from damage by boulders moving in flood season.from damage by boulders moving in flood season. A permanent weir should be considered in the following conditionA permanent weir should be considered in the following conditions, if:s, if:

large boulders do not move in the river at the weir site.large boulders do not move in the river at the weir site.the river bed is not eroding, aggrading or shifting course.the river bed is not eroding, aggrading or shifting course.there is a scarcity of flow in dry season.there is a scarcity of flow in dry season.there is sufficient fund for construction.there is sufficient fund for construction.the site is not in remote areas.the site is not in remote areas.

Factors to be considered during design of weirs:Factors to be considered during design of weirs:If a weir across part of the river width is sufficient, it shoulIf a weir across part of the river width is sufficient, it should not be extended d not be extended across the entire width.across the entire width.The weir length should allow safe passage of design flood.The weir length should allow safe passage of design flood.The weir height should be as low as possible but should be such The weir height should be as low as possible but should be such that the that the water level rises above the upper edge of the intake mouth.water level rises above the upper edge of the intake mouth.The weir profile should be such that it is possible for the bed The weir profile should be such that it is possible for the bed load to move load to move the boulders to roll over it. the boulders to roll over it.

Diversion Weir contdDiversion Weir contd

Photo : Temporary WeirPhoto : Temporary Weir

Photo : Permanent WeirPhoto : Permanent Weir

Intake/ Function of the intake/TypesIntake/ Function of the intake/TypesAn intake is a structure in the diversion works where the water An intake is a structure in the diversion works where the water to the power to the power plant is either abstracted or separated from the river flow. plant is either abstracted or separated from the river flow. To ensure the withdrawal of flow from the river in the required To ensure the withdrawal of flow from the river in the required quantity and quantity and directing towards water ways of the scheme.directing towards water ways of the scheme.To limit excess flow into the intake during high flow season.To limit excess flow into the intake during high flow season.To control the sediment inflow towards water ways from the sourcTo control the sediment inflow towards water ways from the source river.e river.Minimizes hydraulic losses.Minimizes hydraulic losses.Prevent formation of air vortices.Prevent formation of air vortices.Prevents floating debris, trash and ice from entering the water Prevents floating debris, trash and ice from entering the water conveyance conveyance system.system.Types of intake structure are chiefly distinguished by the methoTypes of intake structure are chiefly distinguished by the method used to d used to divert water from the river. In MHP generally two types of intakdivert water from the river. In MHP generally two types of intake are used:e are used:

Side IntakeSide IntakeBottom IntakeBottom Intake

Coanda Intake ( Innovative Intake tested in a MHP in UK)Coanda Intake ( Innovative Intake tested in a MHP in UK)

Side IntakeSide Intake

A structure built along a river bank and in A structure built along a river bank and in front of a canal / conduit end for diverting front of a canal / conduit end for diverting the required water safely. Side intakes are the required water safely. Side intakes are simple, less expensive, easy to build and simple, less expensive, easy to build and maintain.maintain.

Site IntakeSite Intake

Site selection for IntakeSite selection for Intake

It should be possible to divert the design flow from the river tIt should be possible to divert the design flow from the river towards the owards the headrace.headrace.The river should not change its course at the intake location ovThe river should not change its course at the intake location over time.er time.The river should not have high gradient at the intake site.The river should not have high gradient at the intake site.Placed it at the side of rock outcrop or behind the large bouldePlaced it at the side of rock outcrop or behind the large boulderrPlace at straight reach as far as possiblePlace at straight reach as far as possibleIn case of bend, it should be on the outer side of the bend In case of bend, it should be on the outer side of the bend never on the never on the inner side of a bend. (Sediment deposit protection + dry season inner side of a bend. (Sediment deposit protection + dry season flow flow assurances)assurances)

Bottom IntakeBottom Intake

Photo : Bottom IntakePhoto : Bottom Intake

!" #!" #

HYDROLOGYHYDROLOGY

11 month (~92%) exceedance criteria in MHP context11 month (~92%) exceedance criteria in MHP contextThe installed capacity should be available to the Community The installed capacity should be available to the Community at least 11 months a year (12 Months for REDP Projects)at least 11 months a year (12 Months for REDP Projects)Maximum demand during the winter season Maximum demand during the winter season The driest season (12 month exceedance) is winter (mid Jan The driest season (12 month exceedance) is winter (mid Jan mid Feb) for streams that are snow fed & April mid Feb) for streams that are snow fed & April May for May for streams that come from spring sources.streams that come from spring sources.

In the absence of flow exceedance criteria, schemes could be In the absence of flow exceedance criteria, schemes could be oversized.oversized.~ 80~ 80--85 % of 11/12 months Discharge is taken as the designed 85 % of 11/12 months Discharge is taken as the designed dischargedischarge

55--10% for losses consideration10% for losses consideration 10% for down stream discharge10% for down stream discharge

Design Discharge

Civil Works General RequirementCivil Works General Requirementa.a. Flow Duration Curve (FDC) shall be established from stream Flow Duration Curve (FDC) shall be established from stream

gauging at least one lean season measurement gauging at least one lean season measurement ..b.b. QQdesigndesign < Q < Q minmminm from FDC for stand from FDC for stand alone mode , Down stream alone mode , Down stream

flow requirement must be as per government rules.flow requirement must be as per government rules.c.c. Water conveyance system (excluding penstock and tailrace) shallWater conveyance system (excluding penstock and tailrace) shall

be designed for 10 be designed for 10 20% higher flow.20% higher flow.d.d. Specification for drawing, c/s interval, etc.Specification for drawing, c/s interval, etc.

Diversion and IntakeDiversion and Intakea.a. Where to use lateral intake or a bottom intake?Where to use lateral intake or a bottom intake?b.b. Flood period Flood period eg. For MHP30Kw, it is 50 years. c.c. OrificeOrificed.d. Stop logStop loge.e. Provision for debris etc.Provision for debris etc.

Gravel Trap and Sand TrapGravel Trap and Sand Trapa. a. Where these are not requiredWhere these are not required-- spring sourcespring sourceb.b. Sluice gate requirementSluice gate requirementc.c. Size of grains to be settled are >0.2mm, minm. 90% should be setSize of grains to be settled are >0.2mm, minm. 90% should be settled tled

for design head 100mfor design head 100md.d. LL-- slope should not be < 1:30 for side intake, flushing arrangemenslope should not be < 1:30 for side intake, flushing arrangement, t,

ForebayForebaya.a. Shall house an overflow spillway, a drain valve or stop log Shall house an overflow spillway, a drain valve or stop log

gate to flush sediment, and a trash rack, Disposal gate to flush sediment, and a trash rack, Disposal requirement of spilled waterrequirement of spilled water

b.b. Length, width, submergence for PSP, leakage etc. are Length, width, submergence for PSP, leakage etc. are mentionedmentioned

c.c. Thickness of concreteThickness of concretePenstockPenstocka.a. Excavation/ depth in case of PVC/HDPEExcavation/ depth in case of PVC/HDPEb.b. Types, sizes, of support piers, anchor blocksTypes, sizes, of support piers, anchor blocksc.c. Movement and clearances in support structuresMovement and clearances in support structuresd.d. About acting forces and their transmissionAbout acting forces and their transmissione.e. Air vent and sizeAir vent and size

Power housePower housea.a. Elevation with respect to high flood levelElevation with respect to high flood levelb.b. Weather proof requirement, ventilation, doors, windows, Weather proof requirement, ventilation, doors, windows,

roof, working space, store room, etc.roof, working space, store room, etc.c.c. Hoist for turbine/generator installation for >30kwHoist for turbine/generator installation for >30kwd.d. Earthing systemEarthing systeme.e. Foundation Foundation f.f. Drainage in cable ductsDrainage in cable ducts

TailraceTailracea.a. Water level with respect to turbine runnerWater level with respect to turbine runnerb.b. V V notch weir provisionnotch weir provisionc.c. Energy dissipating provisionEnergy dissipating provision

Weir and IntakeWeir and Intake

Orifice Intake DesignOrifice Intake Design

Set V through the orificeSet V through the orificeCalculate Orifice Area required: Calculate Orifice Area required:

Set orifice height or width and calculate the other Set orifice height or width and calculate the other parameter: parameter:

VQA=

$%%&'%()'* )+

HAW =

Orifice Intake design Orifice Intake design (contd(contd))

Check flow through the orifice Check flow through the orifice using the submerged orifice using the submerged orifice equation:equation:

Normal river water (hr) is set Normal river water (hr) is set by weir heightby weir heightCanal height hh is set when Canal height hh is set when sizing headrace. Ensure orifice sizing headrace. Ensure orifice is submergedis submerged

, - ,('.,('/

)(2 hr hhgACQ =

Orifice Intake design Orifice Intake design (contd(contd))

Repeat calculations for flood flow conditionRepeat calculations for flood flow condition Size initial headrace canal to accommodate Size initial headrace canal to accommodate

flood flowflood flow Locate spillway as close as possible & size its Locate spillway as close as possible & size its

capacity to spill the entire flood flowcapacity to spill the entire flood flow

Possible LayoutPossible Layout

Gravel

Flushing Gate

1:50

Gravel Trap

C

Spillw

ay C

anal

Spillway

Gabion

Protection

1:30

CR

EST

Left flood wallRiver / Khola

C

B B

D

D

A

Headrace canal sizingHeadrace canal sizing

Decide on canal type Decide on canal type Earthen, cement Earthen, cement masonry, concrete etc.masonry, concrete etc.Based on type of canal chosen, set velocity Based on type of canal chosen, set velocity & side slopes & side slopes Set either canal water depth or width and Set either canal water depth or width and calculate the other based on Manningcalculate the other based on Mannings s equation: equation:

2

3232 ,1

==

ARQnSSAR

nQ

Headrace canal sizingHeadrace canal sizingManningMannings equations equation Q = flow in m3/sQ = flow in m3/s A = cross sectional area of A = cross sectional area of

canal (up to water depth), m2canal (up to water depth), m2 S = Slope of the energy S = Slope of the energy

grade line ~ ground slopegrade line ~ ground slope n = roughness coefficient of n = roughness coefficient of

canal, also called Manningcanal, also called Mannings s roughnessroughness

R = Hydraulic radius, A/P,R = Hydraulic radius, A/P, P = Wetted perimeter P = Wetted perimeter sum sum

of lengths of two sides and of lengths of two sides and width of canal up to water width of canal up to water depth: w + 2h depth: w + 2h

2

3232 ,1

==

ARQnSSAR

nQ

0

&'''+

Headrace canal sizingHeadrace canal sizingCheck for critical velocity (T = Top width in canal):Check for critical velocity (T = Top width in canal):

Velocity in canal < 0.8VVelocity in canal < 0.8Vcc to ensure stable uniform flowto ensure stable uniform flowSediment deposition in canalsSediment deposition in canalsShieldShields formula d = 11RSs formula d = 11RS d = Particle size transported in canal, md = Particle size transported in canal, m R Hydraulic radius, mR Hydraulic radius, m S = canal slopeS = canal slope

Design to ensure no deposition in canal. e.g., if G. trap is Design to ensure no deposition in canal. e.g., if G. trap is designed to settle particles larger than 2 mm, then, the canal designed to settle particles larger than 2 mm, then, the canal from G. Trap to S. Basin must be able to transport particles up from G. Trap to S. Basin must be able to transport particles up to 2 mm.to 2 mm.

TAgVC =

CanalCanal

Spillway sizingSpillway sizingSpillway required to spill Spillway required to spill excess flows during excess flows during floods or for canal floods or for canal maintenance maintenance downstream: downstream:

667.0

=

weirWovertop xLC

Qh

1

, 2

1

2

Spillway sizingSpillway sizing

CCww for different weir for different weir ProfileProfile

3

HeadraceHeadrace

Canal width = 1.1 mCanal width = 1.1 mNote: required design depth = 0.5 m only, so Note: required design depth = 0.5 m only, so add another spillway by reiterationadd another spillway by reiteration

Note: this headrace will be too expensive if Note: this headrace will be too expensive if continued downstream. Therefore, resize continued downstream. Therefore, resize headrace downstream of spillway with design headrace downstream of spillway with design flow only.flow only.

0.98 m1.3 m 0.74 m 0.80 m

4.0 m

Headrace & SpillwayHeadrace & Spillway

,4

5

Sizing of headrace pipeSizing of headrace pipe1.1. Select pipe velocity based on whether upstream of G. Trap/S. basSelect pipe velocity based on whether upstream of G. Trap/S. basin in

or downstream. V ~ 1.5 m/s for headrace u/s of G. trap & ~3.0 mor downstream. V ~ 1.5 m/s for headrace u/s of G. trap & ~3.0 m/s /s for d/s of G. Trap for d/s of G. Trap

2.2. Calculate actual velocity:Calculate actual velocity:V = velocity m/sV = velocity m/sQ = design flow in mQ = design flow in m33/s/sD = pipe inner diameter in mD = pipe inner diameter in m

3.3. Total loss = wall loss + turbulence lossTotal loss = wall loss + turbulence loss4.4. Calculate head loss in pipe length, inlet & bendsCalculate head loss in pipe length, inlet & bends

2

4dxQ

AQV

==

Gravel trap/settling basinGravel trap/settling basinGravel trap/Settling basinGravel trap/Settling basin

-- Gravels/particles should Gravels/particles should settle in the basinsettle in the basin

-- It should be possible toIt should be possible tosafely flush the settled safely flush the settled particles from the basinparticles from the basin

-- Gravels should not Gravels should not deposit upstreamdeposit upstream

-- Max gravel size governed Max gravel size governed by coarse trashrack by coarse trashrack spacingspacing

Settling Basin Basic theorySettling Basin Basic theory

Ideal basin:Ideal basin:A particle entering water A particle entering water

surface at beginning surface at beginning of settling basin (point of settling basin (point X) should reach the X) should reach the end of the basin end of the basin (point Y) if it is to be (point Y) if it is to be settled settled

Settling Basin Basic theorySettling Basin Basic theoryL = settling zone lengthL = settling zone lengthB = Settling zone widthB = Settling zone widthy = mean water depth y = mean water depth

or hydraulic depthor hydraulic deptht = time for particle to t = time for particle to

travel L (s) travel L (s) VVpp = horizontal velocity= horizontal velocityw = fall velocity (from w = fall velocity (from

ShieldShields graph)s graph)Q = dischargeQ = discharge

Settling Basin Basic theorySettling Basin Basic theory

For particle to reach For particle to reach from X to Y, these from X to Y, these equations have to be equations have to be valid:valid:

BLwQcbaFromcyBVQ

btVLawty

p

p

==>

=

=

=

,,,

)(

)()(

Settling Basin Basic theorySettling Basin Basic theory

Q = BLwQ = BLwTherefore, for a given Q, & particle size to be Therefore, for a given Q, & particle size to be

settled, ideal dimensions can be determined:settled, ideal dimensions can be determined:In practice larger basin required because:In practice larger basin required because:-- turbulence in basinturbulence in basin-- imperfect flow distribution at entrance &imperfect flow distribution at entrance &-- converge flow at exits, curves etc.converge flow at exits, curves etc.

Thus, required plan area should be doubled. Thus, required plan area should be doubled.

Settling BasinSettling Basin--Basic theoryBasic theorySmooth transitionSmooth transitionL/B = 4 L/B = 4 1010

can be 27can be 27oo (1:2 (1:2 1:5).1:5).ddlimitlimit

h h 100 m, ddlimit limit = 0.1 = 0.1 0.2 mm0.2 mm

itdByQV lim44.0

Incorrect: High velocity in centre stream and turbulence in corners

Correct: Low velocity throught width, no turbulence

Desilting Basin

Desilting BasinDesilting Basin

Forebay Forebay -- design criteriadesign criteria

-- Trashrack, VTrashrack, V

Forebay Cum Desilting BasinForebay Cum Desilting Basin

L(entry) = 3.80 L(settling) = 10.00

Over Flow Length = 6.00

12.5

Sluice gate W(settling) = 2.50

L(exit)

A. Block-1

Expansion JointPenstock Pipe

Trash RackAirvent Pipe

HDPE pipe (spill way)

ForebayForebay

SUPPORT STRUCTURESSUPPORT STRUCTURES

Support piersSupport piers

Penstock Penstock AlignmentAlignment

Support piersSupport piers

Use of Tar paper Use of Tar paper (asbestos sheet) (asbestos sheet) minimizes friction minimizes friction between pipe & between pipe & support piersupport pierBase plate Base plate provides provides additional safetyadditional safety

Spacing of support piersSpacing of support piers

Diameter (mm) 100 200 300 400 500Thickness mm support piers spacing in meter 2 2 2 2.5 3 34 3 3 3 4 46 4 4.5 5 5 6

Sizing of Anchor BlocksSizing of Anchor Blocks

Thumb rule for P Thumb rule for P

Sizing of Anchor BlocksSizing of Anchor Blocks

ii.ii.Bends < 45Bends < 45oo

Double the concrete volume than for Double the concrete volume than for straight sectionstraight sectione.g., if dia=200 mm, bend = 20e.g., if dia=200 mm, bend = 20oo

Anchor block volume=2x(200/300) Anchor block volume=2x(200/300) =1.33 m=1.33 m33

Sizing of Anchor BlocksSizing of Anchor Blocksiii. bends > 45iii. bends > 45oo

Treble the concrete than for straight Treble the concrete than for straight sectionsectione.g., dia. = 350 mm, Bend = 58e.g., dia. = 350 mm, Bend = 58oo

Volume required = 3 x (350/300) = 3.5 mVolume required = 3 x (350/300) = 3.5 m33

Note: 1 anchor block every 30 m even if Note: 1 anchor block every 30 m even if there is not a bend at this length.there is not a bend at this length.

Sizing of Anchor BlocksSizing of Anchor Blocks

Some construction detailsSome construction details

Machine FoundationMachine Foundation

Generator

T

u

r

b

i

n

e

T

a

i

l

r

a

c

e

c

a

n

a

l

(20 mm dia.)Anchor rods

TurbineGenerator

T/G Base frame

300 mm stone soling200 mm RCC ( 1:1.5:3)

Stone masonry

in 1:4 c/s mortar Tailrace canal (Slope = 3.5%)

1 : 1.5 : 3 RCCstone soling

100 mm 1 : 1.5 : 3 Pre cast slab

A

APLAN

SECTION - AA

1

.

2

0

.

7

0

Machine FoundationMachine Foundation

Power HousePower House

OPERATORQUARTER

A

A

T

G

ValveBT

Penstock Pipe

ELC

75 mm PCC (1:2:4)

200 mm soling

1:40 SlopeTailrace

CGI Sheet Roofing

W

W

W

W1

DD1

D1

W1

Powerhouse and Tailrace

Thank You!Thank You!