performance evaluation of desilting devices

Under the guidance ofDr. Arun Kumar

Alternate Hydro Energy Centre

IIT Roorkee

1

Presented by

GURDEEP SINGH

OUTLINE

2

Problem of sediment in SHPDesilting basinsNeed of Performance Evaluation of Desilting basinsObjective of StudyMethodology AdoptedAnalysis and EvaluationResultsConclusionLiterature ReviewReferences

Problem of sediment in SHP Plants Sedimentation problem in Hydropower starts from headwork’s to power

house. Each and every Structure intact with water is susceptible and vulnerable

due to sediment laden water. This problem is more serious in Himalayan region where good potential of

SHP exist. In the case of run-of-river, a relatively small dam or a barrage is built across a

mountain stream to divert the river water into the intake which in turn feeds

the power house through a water conductor system. Due to the large quantities of sediment likely to be transported by the rivers. This will leads to various problems:-

1. The diversion dam/barrage may get silted up to the crest within short period of construction.

2. Thus large quantity of sediment may enter the intake and decrease in the discharge carrying capacity of the water conductor system.

3. Cause damage to the tunnel lining,4. Erode the turbine blades and auxiliaries

3

Effects on civil structures

Sediment deposited in lined channel Sediment deposited in tailrace channel of hydropower plant

Sediment deposited near diversion weir

4

Sediment erosion at Pelton turbine needle

Sediment erosion at Pelton turbine

Eroded guide vanes Erosion(At Runner) at pressure side of blade

Effects of Erosion on various components of Turbine

5

DESILTING BASIN Desilting basins are constructed close to the intake to trap incoming sediment

before leading to water conductor system/turbine.

Removal of sediment in desilting basins is done by reducing the velocity of flow through them and remove settled sediment under gravity or mechanical or manually.

There are two types of desilting basin mainly used for SHP sites in India are :-

i. Settling basin

ii. Vortex settling basin

6

Design parameters for settling basin

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1. Size of sediment load to be removed 2. Settling basin dimensions 3. Velocity in chamber basin 4. Flushing discharge 5. Trap Efficiency 6. Sediment removal techniques

8

1. Basin diameter d, and basin height H; 2. Flushing discharge, Qo or flushing pipe diameter, d0 3. Depth of flow in the basin; 4. Radial slope of basin floor, Sc (horizontal to one vertical)5.Basin depth at periphery, h2

6. length of overflow weir, Li, and 7. Modelling criteria to ascertain the performance of the designed VSB with the aid of a physical model

Design parameters for vortex settling basin

Need for performance evaluation

9

1. Settling basin are being designed oftenaly by Indian shp designer on basis of

limited data on sediment due to its poor availability on account of not using

skilled persons which are not available easily.

2. It has been observed that often desilting basins are inefficient for silt

removal. The silt removal arrangement are poor, resulting in frequent

choking. This result frequent forced outrage of plant.

Thus performance of these desilting basin are evaluated to make aware to plant

owner sediment impact and loss of generation

10

Desilting tank in himanchal pradesh 3MW SHP project

Desilting tank in Uttrakhand 5MW SHP project

Objective of study

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The objective of this work :-

1.To evaluate the performance of existing desilting devices.

2.To study the impact of sediment on turbine runner

corresponding to desilting basin efficiency

Methodology Adopted

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1. Reviewed various desilting devices deployed for small hydro power plants.

2. Identified the projects for data collection covering high and medium head in different location.

3. Prepared a questionnaire, approach the project owner for data and visit the site. Data covering the type of desilting devices, dimension ,number of chamber provided and flushing arrangement and impact of sediment on turbine and other components.

4. Collected sediment(inflow and flushed out) from different SHP sites by undertaking site visits.

5. Sieve analysis of sample collected.6. Evaluation is done by :-

1. Comparing the relation/charts of efficiency of desilting basin given by different author’s with observed efficiency.

2. Impact of sediment on turbine runner.

Site visit details

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Location Visit durationSites located in Chamba and Kangra District visited (Tarila shp station, Tarila-II shp station, Upper awa shp, Baner-III shp, Sahu shp station, Iku-II shp, Upper khauli shp, Drinidhar shp station, Bhuri singh power house, Khauli shp station, Gaj shp)

Nov 17-29,2012

Sites located in Kullu and Mandi District visited (Jirah shp station, Aleo shp station, Baragan shp station, Sarbari shp , Brahmaganga shp station, Patkari shp station, Gurahan shp station

Jan 25- Feb 5,2013

HPPCL design office,Sunder nagar,HP May 22- 26,2013

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Sr.no

Name of station Name of stream

Installed capacity(

MW)

Type of Turbine

Head (m)

Discharge

(cumec)

Inlet channel

width(m)

Desilting basin dimensions(m) no. of

outlet

Flushing conduit(

mm)U/S Transition

Length

Width

Depth D/S Transition

1 TARILA Tareila nallah 2X2.5 Francis 184 6.00 2.0 10.4 54.7 7.5 4.5 7.8 1 600Ø

2 TARILA-IITareila nallah 2X2.5 Francis 133 6.10 2.0 5.0 36.0 8.5 3.1 5.0 1 600Ø

3 BANER-III Baner khad 2X2.5 Pelton 302 2.70 1.8 7.5 30.0 5.0 2.5 1 500x5004 IKU-II Iku khad 2X2.5 Pelton 362 3.96 1.8 7.7 52.0 5.0 2.5 4.0 1 500x500

5 UPPER KHAULI Khauli Khad 2X2.5 Pelton 430 2.34 1.8 8.0 51.5 4.5 4.1 4.0 1 500x500

6 DRINIDHAR Brahl Khad, 2X2.5 Pelton 249 3.10 1.8 10.5 45.0 5.0 2.5 5.0 1 500x500

7 ALEO MANALIAllain stream 2X1.5 Pelton 290 1.60 1Ø 25.0 5.0 2.0 5 300Ø

8 BARAGOAN Sanjoin nallah 1X1.9 Francis 170 4.25 2.3 18.0 62.0 6.0 3.0 1 1000Ø

9 SARBARI Sarbari khad 2X2.25 Pelton 202 4.50 43.9 9.4 4.1 4 300Ø

10 JIRAH Jirah Nallah, 2X2 Pelton 348 1.31 1.2Ø 9.5 30.0 5.0 6.0 3 800Ø

11 TOSS Toss nallah 2x5 Pelton 186 4.32 45.0 7.0 3.0

12BRAHMAGANGA

Bharamgana 2X2.5 Pelton 230 3.15 1.6Ø 20.6 40.0 7.0 3.0 6.0 1 500Ø

13 GURAHAN Gurahan Khud 1X1.5 Pelton 216 1.10 1.2 4.5 40.0 3.0 1.0 4.5 1 300Ø

14 PATKARI Bakhli khad 2X8 Pelton 375 5.83 3.5 10.0 54.0 7.0 3.5 3 500Ø

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Sr.no

Name of station

Name of stream

Installed

capacity(MW)

Type of Turbin

e

Head (m)

Discharg

e (cu

mec)

Inlet channel width(m

)

Desilting basin dimensions(m)

slope(1V:H)

no. of

outlet

Flushing

conduit(mm)

Diameter Depth

15 GAJ Gaj & Leond 3x3.5 Pelton 213 6.93 3.4 17 2.05 01:10 1 600Ø

16 KHAULI Khauli Khad 2x6 Pelton 475 3.19 2.4 12 2.00 01:10 1 450Ø

17BHURI SINGH Sal nallah 0.45 Francis 13.72 5.14 3.4 17 2.15 01:10 1 600Ø

Vortex settling basin sites

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1 2

11

10

12

9

7

14

13

8

6

4

5

1615

17

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D-tank Baragran shp station(1x1.9MW) D-tank Drinidhar shp station (2x2.5MW)

D-tank Sarbari shp station (2x2.25MW)D-tank Jirah shp station (2x2.0MW)

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D-tank Tarila-II shp station (2x2.5MW) D-tank Tosh mhp station (2x5 MW)

D-tank Upper khauli shp station (2x2.5 MW) D-tank Tarila shp station (2x2.5MW)

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Vortex Settling Basin

D-tank Khauli shp station(2x6 MW) D-tank Bhuri singh power house(450 kW)

D-tank Gaj shp station(3x3.5 MW)

Efficiency evaluation of desilting basin

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I. Efficiency of settling basin and vortex settling basin first computed by relation /charts given by various authors and then compared with observed efficiency.

II. Observed efficiency of desilting basins calculated by comparing the GSD curve at inlet and flushing oulet.

III.Relation and charts used for efficiency evaluation of settling and vortex basin are:-

settling basin:-a. Camp Dobbins curve b. Garde methodc. GSD curves (At inlet and flushing outlet)

vortex settling basin:-a. T.C Paul relation b. M.Ather relationc. GSD curves (At inlet and flushing outlet)

Efficiency evaluation of settling basin

1. The minimum size of particle to be removed is selected.

2. Then with help of Hunter Rouse curve fall velocity(Vs) of the selected square quartz particle at particular temperature is obtained. The Hunter Rouse curve of fall velocity(Vs) .

3. Parameters comprising of flow velocity, settling velocity, length and depth of basin calculated. The following parameters are:-

(a) Settling velocity x depth of tank(1/6) Flow velocity x regosity coefficient x √g (b) Settling velocity x length

Flow velocity x Depth of tank

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I. Camp-Dobbins curve

Hunter Rouse curve Fall velocity of quartz sphere in water and air

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Sediment removal Efficiency of settling basin by Camp-Dobbins

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II.Garde method

Relationship developed by Grade to find the sediment removal efficiency of settling basin give by:-

where ηo is the limiting efficiency obtained for a given w/u* at large values of L/D and k is a coefficient.

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Efficiency evaluation of vortex settling basin

I. Paul’s relation

The Efficiency computation relation given by T.C Paul et al. is :-

Where P is Efficiency in (%),Dt = Diameter of tankSc = slope adopted at all project sites (10H : 1V)Vs is settling velocity of particle W is vertically upward velocity(W=(4Qs/πDt2).Qs= overflow Discharge(Qi-Qo)Qi= Inlet dischargeQo= Flushing discharge

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II.Ather’s relation

The efficiency computed method given by M. Ather relation is as follows:-

Where Qi =Discharge in the inlet channel ; Qu =Discharge flushed out through the under flowω = Fall velocity of sediment; d = Sediment size; hp =Depth of flow at periphery of the chamber; Zh =Elevation difference between inlet and outlet channel beds at their junctions with the vortex chamber, RT =Radius of the vortex chamber,g = Gravitational acceleration, v = Kinematic viscosity and K =CoefficientQw= Qu+k(Qi-Qu)

Grain size Distribution

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With the help of this distribution ,percentages of various size of soil grain in a given dry soil sample can be find out.

Sieve analysisThe soil sample is separated in to two fraction by sieving through 4.75mm sieve.

The fraction retained on this sieve (+4.75 mm) is called gravel fraction which is subjected to coarse sieve analysis.a set of sieve sizes 80mm, 20mm 10mm and 4.75mm is used for further gravel fraction.

The material passing through 4.75mm (-4.75mm) is subjected to fine sieve analysis.the set of I.S. sieves for fine sieve analysis consist of 2mm, 1mm, 600μ, 425μ, 212μ, 150μ,75 μ sieves.

Procedure

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A suitable sieve size for the aggregate should be selected and placed in order of decreasing size, from top to bottom, in a mechanical sieve shaker.

A pan should be placed underneath the nest of sieves to collect the aggregate that passes through the smallest. The entire nest is then agitated (10 -15 min), and the material whose diameter is smaller than the mesh opening pass through the sieves.

After the aggregate reaches the pan, the amount of material retained in each sieve is then weighed.

ResultsThe results are presented in a graph of percent passing versus the sieve size. On the graph the sieve size scale is logarithmic. To find the percent of aggregate passing through each sieve, first find the percent retained in each sieve. To do so, the following equation is used,

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The cumulative percent passing of the aggregate is found by subtracting the percent retained from 100%.

%Cumulative Passing = 100% - %Cumulative Retained.

Sieves used in grain size distribution

Experiment Set-up for Sieve analysis

Efficiency computed by comparing the GSD curves :-

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31

32

Vortex settling basin GSD curve

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ANALYSIS AND EVALUATION

Performance of desilting basin are evaluated by :-

1.Comparing the results computed from different methods

2.Effect of desilting basin efficiency on turbine runner

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size of particles in (mm) 0.15mm 0.2 mm 0.25 mm 0.5 mm 1 mm

Site location

Efficiency from Camp Dobbins curve

Efficiency from Garde method

Oserved site efficiency













TARILA SHP STATION,TARILA 100% 85% 30% 100% 95% 33% 100% 95% 41% 100% 95% 46% 100% 95% 75%TARILA-II SHP STATION,TARTILA 75% 37% 63% 97% 94% 60% 100% 94% 58% 100% 94% 58% 100% 94% 67%

BANER-III SHP,BANER 78% 37% 33% 98% 94% 41% 100% 94% 56% 100% 94% 78% 100% 94% 91%IKU-II SHP 88% 23% 30% 99% 69% 29% 100% 99% 38% 100% 99% 58% 100% 99% 85%

UPPER KHAULI SHP,KHAULI 98% 95% 58% 100% 95% 69% 100% 95% 74% 100% 95% 89% 100% 95% 90%DRINIDHAR SHP STATION,DRNIDHAR 95% 31% 0% 100% 95% 0% 100% 99% 25% 100% 99% 44% 100% 99% 82%

ALEO SHP STATION,MANALI 95% 86% 14% 100% 95% 36% 100% 95% 67% 100% 95% 100% 100% 95% 100%BARAGRAN shp station,baragran 97% 48% 50% 100% 99% 56% 100% 99% 60% 100% 99% 53% 100% 99% 61%

SARBARI SHP ,SARBARI 98% 93% 71% 100% 93% 60% 100% 93% 38% 100% 93% 47% 100% 93% 74%

JIRAH SHP STATION,TOSH 100% 70% 50% 100% 70% 50% 100% 70% 57% 100% 70% 92% 100% 70% 97%

TOSH MHP STATION,TOSH 92% 60% 4% 100% 97% 5% 100% 97% 8% 100% 97% 34% 100% 97% 79%

BRAHMAGANGA SHP STATION,MANIKARAN 98% 94% 90% 100% 96% 88% 100% 96% 89% 100% 96% 100% 100% 96% 100%

GURAHAN SHP STATION 97% 19% 38% 100% 43% 36% 100% 76% 36% 100% 100% 57% 100% 100% 80%PATKARI SHP STATION,PATIKARI 90% 43% 22% 100% 97% 21% 100% 98% 22% 100% 98% 51% 100% 98% 82%

Computation efficiency of settling basins

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Efficiency of settling basin evaluated by different methods

37

38

Variation of efficiency of settling basin w.r.t paricle size(mm)

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Name of site 0.15 0.2 0.25 0.3 0.5 1

Efficiency from Paul relati

on

Efficiency from Ather relati

on

Observed site

efficiency


on


on

Observed site

efficiency


on


on

Observed site

efficiency


on


on

Observed site

efficiency


on


on

Observed site

efficiency


on

Efficiency from Athe

r relation

Observed site

efficiency

Bhuri singh SHP 75% 98% 91% 84% 98% 93% 91% 98% 92% 97% 98% 100%113% 98% 100%141% 99% 100%

Gaj SHP 82% 98% 80% 92% 98% 81%100% 98% 75%106% 98% 82%123% 98% 97%155% 99% 100%Khauli SHP 82% 98% 12% 92% 98% 100% 98% 50%106% 98% 67%124% 98% 86%155% 99% 94%

Computation efficiency of vortex settling basins

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Efficiency of vortex settling basin evaluated by different methods

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Variation of efficiency of settling basin w.r.t particle size(mm)

Impact of turbine runner

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Factors influencing erosion -

Silt characteristicsI.Size and Shape of ParticlesII.Hardness of ParticlesIII. Concentration

Resistance of turbine Material,

Net Head on turbines

Velocity of water carrying silt

HEAD (M) MAXIMUM SIZE OF PARTICLES100 – 200 0.60 mm to 1.00 mm200 – 300 0.50 mm to 0.60 mm300 - 500 0.30 mm to 0.50 mm

> 500 0.10 mm to 0.30 mm

Erosive Wear on turbine

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To calculate erosive wear on turbine following relation to be used:-

For Pelton Turbine:-

Where, ‘S’ silt particle size (m). ‘t’, operating hour (h) ‘V’ velocity of flow (m/s) =0.47x0.98x√(2gh)‘W’ normalized wear (g/g) per unit discharge (m3/s)

For Francis Turbine:-

Where W = erosion rate in kg/h,V = velocity of particle in m/s = 0.4x√(2gh)d = particle size in meter, C = silt concentration in g/liter, and K, β, γ and ψ is equal to 0.98, 1.1, 0.8 and 0.85 respectively.

( M.K.Padhy & R.P. Saini, 2008)

(B.K.Gandhi et. al,1999)

Continue…

44

Erosive wear at different sites due to particle size(0.2mm-1mm) have concentration 3000 ppm during the monsoon season in north region of India ( from July to September,t ime=24x90 =2160 hours) calculated.

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Wt loss in kg for particle sizeHead range(m)

Sr.no Name of site Capacity(MW)

Type of turbine

Design discharge(cumec)

Head(m) Velocity(m/sec)

0.2mm 0.25mm 0.3mm 0.5mm 1mm

100-200

1 Tarila-ii shp station,tartila 2 x 2.5 Francis 2.26 133 20.43 0.065 0.078 0.090 0.135 0.236

2

Baragran shp station,baragran 1x1.9 Francis 1.5 170 23.10 0.074 0.089 0.103 0.155 0.270

3 Tarila shp station,tarila 2 x 2.5 Francis 1.589 184 24.03 0.078 0.093 0.108 0.162 0.282

4 Tosh mhp station,tosh 2 x 5 Pelton 3.2 186 27.82 0.094 0.095 0.096 0.099 0.103

200-300

5 Sarbari shp ,sarbari 2 x 2.25 Pelton 1.373 202 29.00 0.047 0.048 0.048 0.050 0.052

6 Gaj shp,dharamshala 3 X3.5 Pelton 3.1 213 29.78 0.118 0.119 0.121 0.124 0.129

7

Brahmaganga shp station,manikaran 2 x 2.5 Pelton 2.52 230 30.94 0.111 0.112 0.113 0.117 0.121

8 Gurahan shp station 1 x 1.5 Pelton 0.83 215.5 29.95 0.032 0.033 0.033 0.034 0.035

9

Drinidhar shp station,drnidhar 2 x 2.5 Pelton 1.49 249 32.19 0.076 0.077 0.078 0.080 0.083

10 Aleo shp station,manali 2 x 1.5 Pelton 0.63 290 34.74 0.043 0.044 0.044 0.045 0.047

300-500

11 Baner-iii shp,baner 2 x 2.5 Pelton 1.19 302 35.45 0.088 0.089 0.090 0.092 0.096

12 Iku-ii shp 2 x 2.5 Pelton 1.69 362 38.82 0.176 0.178 0.180 0.185 0.192

13

Patkari shp station,patikari 2 x 8 Pelton 5.83 374.5 39.48 0.646 0.654 0.661 0.681 0.708

14 Upper khauli shp,khauli 2 x 2.5 Pelton 0.834 430 42.31 0.120 0.122 0.123 0.127 0.132

15 Khauli shp station,khauli 2 x 6 Pelton 1.525 475 44.47 0.265 0.269 0.271 0.279 0.291

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location Site Type of turbine Head(m) Head range Efficiency(%) of settling basin computed from G.S.D curves w.r.t size

of particles (mm)Remarks

0.15 0.3 0.5 1 Regarding efficiency Effect on turbineTARILA-II FRANCIS 133

100 to 200

63 57 58 67 Inefficient in removing particle size upto 1mm Susceptible to erosion

BARAGOAN FRANCIS 170 50 56 53 61 Inefficient in removing particle size upto 1mm Susceptible to erosion

TARILA FRANCIS 184 30 42 46 75 Inefficient in removing particle size upto 1mm Susceptible to erosion

TOSH PELTON 186 4 6 34 79 Inefficient in removing particle size upto 1mm Susceptible to erosion

SARBARI PELTON 202

200 to 300

71 33 47 74 Inefficient in removing particle size upto 0.5mm Susceptible to erosion

GURAHAN PELTON 216 38 42 57 80 Inefficient in removing particle size upto 0.5mm Susceptible to erosion

BRAHMAGANGA PELTON 230 90 92 100 100 efficient in removing particle size upto 0.5mm

Not susceptible to erosion

DRINIDHAR PELTON 249 0 20 44 82 Inefficient in removing particle size upto 0.5mm Susceptible to erosion

ALEO PELTON 290 14 92 100 100 efficient in removing particle size upto 0.5mm


BANER-III PELTON 302

300 to 500

33 76 78 91 Inefficient in removing particle size upto 0.3mm Susceptible to erosion

JIRAH PELTON 348 50 83 92 97 efficient in removing particle size upto 0.3mm


IKU-II PELTON 362 30 40 58 85 Inefficient in removing particle size upto 0.3mm Susceptible to erosion

PATKARI SHP PELTON 375 22 29 51 82 Inefficient in removing particle size upto 0.3mm Susceptible to erosion

UPPER KHAULI PELTON 430 58 81 89 90 efficient in removing particle size upto 0.3mm


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Site location

Type of turbine

Head(m)

Head range(m)

Efficiency(%) of settling basin computed from G.S.D curves w.r.t

size of particles (mm)

Remarks

0.15 0.3 0.5 1Regarding efficiency

Effect on turbine

BHURI SINGH FRANCIS 13.75 <100 91 100 100 100

efficient in removing particle size upto 1mm


GAJ PELTON 213100-200 80 82 97 100

efficient in removing particle size upto 0.5mm


KHAULI PELTON 475300-500 12 67 86 94

Inefficient in removing particle size upto 0.3mm

Susceptible to erosion

48

Economic evaluation of desilting basin

The project taken for the economic study of desilting basin is Upper khauli SHP situated in Kangra, Himanchal Pradesh. The features of project as follows:-Design discharge = 2.3cumec(including flushing discharge)Head = 430mCapacity = 2x2.5 MWType of turbine = Horizontal pelton

Comparative features of Desilting basins

Inlet Discharge (cumec) 2.3 2.3

Basin Dimensions(m) 51.5(L) x 4.5(B) x 6(D) 9m(dia) x 2.55m(D)Volume of Basin(m3) 1390.5 162Flushing Discharge(cumec) 0.58 0.23Water Available for power generation(cumec) 1.73 2.07Cost of Basin(Millon of Rs.) 4.5 0.93Power generation(kW) 5000 6025Settling Efficiency(%) 95 98

49

Economic analysisDifference saving in construction cost = 4.5-0.92 = Rs3.58 Millon

Assuming life of project 35 years and internal rate of return (IRR) as 8%Annual equivalent saving = Rs. 3.58x105 x(1.0835 x0.08 )/( 1.0835 – 1) =Rs. 0.31 Millon/ year

Annual Power saving assuming 60% generation = (6024.99 -5000)x8760x0.60 = 5.2 million units

Net increase in saving due to increase in power assuming rate Rs. 3/kWh =5.2x3 = 15.6 Millon

Thus total saving per year if vortex settling basin is adopted instead of settling basin = 0.31+15.6 = 15.91 Millon

50

Settling basin.

Designed settling basin at the selected sites are sufficient to tap the particles less than 0.5mm in spite of that, these settling basin showing less efficiency this may due to:-

Inadequate design flushing arrangement.Turbulence in water, causes the sediment in suspension.Transitions are not designed properly.These settling basin mostly designed for intermittent flushing, but timely flushing are not done due to this flushing arrangement get chocked frequently causes decrease in efficiency of these basins..

Vortex settling basinThe observed efficiency of vortex settling basin is very close to designed efficiency for all particle Further these basin required less volume of water to flush the sediment and proves to be economical desilting device specially for removal of particle size 0.1mm- 0.2mm cause sediment erosion on hydro mechanical components.

RESULTS

51

Comparative study of settling basin and vortex settling basin shows that vortex settling basin is efficient and economical desilting device as compared to settling basin for small hydropower sites having advantages:-

Land area required for sedimentation is less.Require lower flushing.Cost of construction is about one fourth of settling basin cost.Hydraulic efficiency as compared to settling basin is high.In vortex settling basin water may diverted directly to power channel during lean season when water is almost free of sediments. This is important in cold region where settling basin freeze due to lower vicinity and causes the shutting down of machines.

CONCLUSIONS

Author Title of Paper Objective ResultsDevelay et al. (1996)

Desilting basin of Dul Hasti hydro electric project

To trap a high percentage of the coarser particles generally made of quartz

The trapping efficiency increases with the sediment concentration.

Raju, et al. (1999)

Sediment Removal Efficiency of Settling Basins

To find a new relationship for sediment settling basin for non-cohesive sediments

It was also found that Continuous flushing of the basin improves the sediment removal efficiency of settling basins.

Weerakoon et al. (2007)

Effect of the Entrance Zone on the Trapping Efficiency ofDesilting Tanks in Run-of-River Hydropower Plants

To find effect of the entrance zone on the sand trapping efficiency of the desilting tanks

The sand trapping efficiency was found to vary from 50% to 85% with the reduction of expansion angle from 30o to 10o.The trapping efficiency of the tank increases with the reduction of the expansion angle of the entrance zone in the desilting tanks, the optimum expansion angle was found to be about 10 deg.

Shah et al. (2008)

Transitions For Desilting Basin With Open Channel Flow

To study the effect of Transitions For Desilting Basin With Open Channel Flow

The hydraulic model studies by providing a simple hump and a central divide wall

Literature ReviewEfficiency of Desilting BasinEfficiency of Settling Basin

52

Author Title of Paper Objective ResultsAlired D. Mashauri (1983)

Removal of sediment particlesBy vortex basin

discussed the hydraulic performance of vortex-type settling basins both, with horizontal and sloping floor

settling efficiency η , and amount of water through orifice arc given for both versions - horizontal floor and sloping floor showed a respectable performance

Paul et al (1991)

Vortex Settling Basin Design Consideration

vortex settling basin design for extraction of sediment smaller than 0.5 when a diaphragm and a deflector were incorporated in the inlet canal and basin, respectively

Diameter of the flushing pipe and flushing discharge depend on the grade of sediment transported by the inlet canal

Athar et al (2002)

Sediment Removal Efficiency of Vortex Chamber TypeSediment Extractor

Studied the sediment removal efficiency of vortex chamber type sediment extractors.

a new relationship was developed for determination of the sediment removal efficiency of the vortex chamber type sediment extractors.

Nguyen Quang Troung (2010)

Effect of deflector on removal efficiency of a deep-depth vortex chamber sediment extractor

To study effect of deflector in circular basin

The experimental results also indicate that the values of η was considerably stable and reach the maximum value for the case of three deflectors.

Naser et al. (2011)

Improvement the Trap Efficiency of Vortex Chamber for Exclusion ofSuspended Sediment in Diverted Water

To improve trap efficiency of vortex sediment settling basin.

It was found that the best location for the deflector is between the inlet channel and the outlet overflow weir, when the inlet channel is located under the overflow weir increases the trap efficiency and the hydraulic efficiency

Efficiency of vortex type of settling basin

53

Author Title of Paper Objective ResultsThapa et al. (2005)

Problems of Nepalese hydropower projects due to suspended sediments.

To study effect of type mineral of sediment on turbines.

It was found that higher amount of quartz content gives higher erosion rate and the percentage of quartz, shape of the particles also has influence in erosion rate.

Bajracharya et al.(2008)

Sand erosion of Pelton turbine nozzles and buckets.

To find effect of sediments on pelton turbine.

It was found that High quartz content and increase sediment load during monsoon along with the small particle size are the major cause for the severe erosion of turbine parts.

Padhy et al.(2009)

Effect of size and concentration of silt particles on erosion of Pelton turbine buckets

To study effect of concentration and size of silt on erosion of pelton turbine.

The erosive wear rate increases with an increase in the silt concentration irrespective of the silt size.

Prasad et al. (2010)

Sediment Erosion in Hydraulic Turbine Using Rotating Disc Apparatus

To find relation between erosion and run time.

From this study, erosion (weight loss) was found directly proportional with sediment size and also erosion was found directly proportional with run time.

Hari Prasad Neopane (2010)

Sediment Erosion in Hydro Turbines

To find sediment erosion effects on hdro turbines

It was found that erosion is strongly depended on the shape of the particle.

Poudel et al. (2012)

Sediment impact on turbine material case study of Modi river

To find out the impact of sediment on turbine material.

The sediments in course of rolling down from upstream to downstream its shape and size changes and have less eroding property than one found in upstream of the river.

Padhy et al. (2012)

Effect of shape of silt particles on erosive wear of pelton turbine bucket

To investigate effect of shape of silt particles on erosive wear of pelton turbine bucket.

It has been concluded that the sharp particles have more eroding capacity than the rounded shaped particles.

Characteristics of sediments

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SILT EROSION ON TURBINE

B.S. Mann (2000)

High-energy particle impact wear resistance of hard coatings and their application in hydro turbines

To study, hard coatings such as hard chrome plating, plasma nitriding, D-gun spraying and boronising were studied for high-energy impact wear resistance

It was found that Borided T410 steel appears to be an excellent erosion resistance shield to combat high-energy particle impact wear. It can provide an appropriate solution to the hydropower stations severely affected due to silt.

Padhy et al. (2008)

A review on silt erosion in hydro turbines

Survey various aspects related to silt erosion in hydro turbines, different causes for the declined performance and efficiency of the hydro turbines

It was found that Silt erosion in hydro turbines cannot be avoided completely, but can be reduced to an economically acceptable level

Peter Joachim Gogstad (2012)

Hydraulic design of Francis turbine exposed to sediment erosion

To carried out new hydraulic design of runner and guide vanes of existing francis turbine at La Higeura power plant where velocity component were reduced.

The best way of reduce erosion will therefore be coating of all wet surfaces.

Thapa et al. (2012)

Empirical modeling of sediment erosion in Francis turbine

To dentify an appropriate erosion model for Francis turbine

It has been found that sediment data from the site can be analyzed to predict the damage in Francis runner due to erosion

Thapa et al. (2012)

Current research in hydraulic turbines for handling sediments

To create and optimize the design of Francis runners.

It was also observed that optimization of hydraulic design of blade profile alone can reduce sediment erosion more than 30%

Design parameters of turbine

Author Title of Paper Objective Results

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Research paper

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Gurdeep singh, Arun kumar, “A Review of Desilting Basins Used in Small Hydropower Plants”, International journal of emerging technology and advanced engineering, ISSN 2250-2459, ISO 9001:2008 certified journal, Volume 3, Issue 5, May 2013 pp 440-444. (published)

Gurdeep singh, Arun kumar “Performance evaluation of desilting basin used in small hydropower projects” (in process)

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REFERENCES1. Guidelines for Development of Small Hydro Electric Scheme, CEA (1982).

2. International course on”Small Hydropower Development”, Feb 2004 by AHEC,IITR

3. “Water Borne Sediments :Problems And Their Solutions”, by H.L.Uppal,FNA ICAR scientist and B.D Sharma ICAR Research Fellow, Punjab Agriculture University,Ludhiana 28 January,1975.

4. “Design Manual For Canal Sediment Extractors “Vol-1 Main text HR Wallingford Ltd August 1993.

5. Badrinath H.S and Bhardwaj S.D “Vortex Desilting Tanks For Sediment Exclusion For small Hydro Projects” .Proceedings design of hydraulic structures Dept of civil engg. UOR, Roorkee pp 283-291 (1994).

6. Garde R. J,Ranga Raju K. G. and A. W. R. Sujudi “Design of settling basins” Journal of Hydraulic Research, vol 28:1, 81-91 (1990).

7. Sumer B. M. “Design Of Settling Basins” Journal of Hydraulic Research, 29:1, 136-143. (1991).

8. Develay D,Binquet J, Divatia and Venkatesha C. R “Desilting Basin System Of The Dul Hastihydroelectric Project” Journal Of Hydraulic Engineering october 1996 pp 565-572.

9. Vittal N and Raghav M.S “Design Of Single-Chamber Settling Basins” Journal Of Hydraulic Engineering / May 1997/ pp 469-471.

10.Ranga Raju K.G, Kothyari U.C, Srivastav S, and Saxena M “Sediment Removal Efficiency Of Settling Basins” Journal Of Irrigation And Drainage Engineering / September/October pp 308-314.

11.Janssen R.H.A. “Analysis and Design of Sediment Basins” The Institution of Engineers, Australia 8th National Conference on Hydraulics in Water Engineering ANA Hotel Gold Coast, Australia 13-16 July 2004

12.Weerakoon S. B. and Rathnayake U. S“Effect of the Entrance Zone on the Trapping Efficiency of Desilting Tanks in Run-of-River Hydropower Plants” International Conference on Small Hydropower - Hydro Sri Lanka, 22-24 October 2007 pp 1-6.

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13. Shah C. M,Verma M. K, and Deolalikar P. B “Transitions For Desilting Basin With Open Channel Flow” ISH journal of hydraulic engineering. Vol. 14. 2008. NO. I pp 117 to 125.

14. Alired D. Mashauri “Removal Of Sediment Particlesby Vortex Basin” Aqua Fennica 13: 27-33.(1983).

15. Paul T. C, Sayal S.K, SakhujaV.S, and Dhillon G.S “Vortex-Settling Basin Design Considerations” J. Hydraul. Eng. 1991.117:172-189.

16. Athar M, Kothyari U.C and Garde R.J “Studies On Vortex Chamber Type Sediment Extractor” ISH Journal of Hydraulic Engineering, vol 8:, 1-16 (2002).

17. Truong N.Q “Effect Of Deflectors On Removal Efficiency of A Deep- Depth Vortex Chamber Sediment Extractor” HCMUT – 26-28/10/2011 pp 1-6.

18. Niknia, Naser , Keshavarzi, Reza A, Hosseinipour, E. Zia “Improvement the Trap Efficiency of Vortex Chamber for Exclusion of Suspended Sediment in Diverted Water” World Environmental and Water Resources Congress 2011,Bearing Knowledge for Sustainability ASCE 2011 pp 4124-4134.

19. Padhy MK and Saini RP. A review on silt erosion in hydro turbines. Renewable and Sustainable Energy Reviews 2008;12:1974e87.

20. Peter Joachim Gogstad “Hydraulic design of Francis turbine exposed to sediment erosion” Mater thesis, Department of Energy and Process Engineering,NTNU Jan 2012.

21. Thapa BS, Thapa B, Dahlhaug OG. “Empirical modelling of sediment erosion in Francis turbines”. Journal of Energy 2012.

22. Thapa BS, Gjosater K, Eltvik M, Dahlhaug OG, Bhola Thapa “Effects of Turbine Design Parameters on Sediment Erosion of Francis Runner”.

23. Mann BS “High-energy particle impact wear resistance of hard coatings and their application in hydro turbines” www.elsevier.com/locate/wear 2000. 140–146.

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24. Hari Prasad Neopane ( March 2010) “Sediment Erosion in Hydro Turbines” PhD thesis Norwegian University of Science and Technology, Faculty of Engineering Science and Technology.

25. Padhy MK and Saini RP. “Effect of size and concentration of silt particles on erosion of Pelton turbine buckets”. Energy 2009;34(10):1477e83.

26. Padhy MK, That oi DK and Acharya AK “Effect of shape of silt particles on erosive wear of pelton turbine bucket” IEEE-International Conference On Advances In Engineering, Science And Management (ICAESM -2012) March 30, 31, 2012 pp 19-24.

27. Bajracharya TR, Acharya B, Joshi CB, Saini RP, Dahlhaug OG. “Sand erosion of Pelton turbine nozzles and buckets: a case study of Chilime hydropower plant”. Wear 2008;264:177e84.

28. Thapa B, Shrestha R, Dhakal P, Thapa BS. “Problems of Nepalese hydropower projects due to suspended sediments”. Journal of Aquatic Ecosystem Health and Management; 2005.

29. Padhy MK and Saini RP “Study of silt erosion mechanism in Pelton turbine buckets” Energy 39 (2012) 286-293.

30. Padhy MK and Saini RP. “A review on silt erosion in hydro turbines” Renewable and Sustainable Energy Reviews 12 (2008) 1974–1987.

31. Padhy MK and Saini RP “Study of silt erosion on performance of a Pelton turbine. Energy “ (2011) 141-147.

32. Gandhi B K, Singh S N, Seshadri V. “Study of the parametric dependence of erosion wear for the parallel flow of solid–liquid mixtures”. Tribol Int 1999; 32:275–82

33. Sharma S.K “Sediment Management in Himalayan rivers” Hydro Vision 2006, pp1-12

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Documents

performance evaluation of desilting devices