PRESENTED BY:

RAJ KUMAR BAIRWA13512026

M.TECH Ist YEARA.H.E.S, IIT ROORKEE

INTAKE WORKS AT DIVERSION

WHAT IS INTAKE?“A structure to divert water into a conduit

leading to the power plant” is called Intake.- The glossary of Hydropower Terms-1989.

POSITION OF INTAKES -

Factors governing the arrangement of an intake include the following:

• The intake should be aligned so that the trash and ice tends to float past and not collect at the

intake screens.

• The intake should be arranged so that the effect of such movement (movement of boulders,

stones and sand) will not lead to a partial restriction or blockage of the intake.

• The intake can often be located so as to enable it to be constructed before the level of the

reservoir is raised.

• Give minimum hydraulic losses.

• Prevent formation of air entraining vortices.

COMPONENTS OF INTAKES:

• Intake Gates

• Trash rakes & screens

• Fish ladders

• Ice, log and trash boom

• Silt Excluders and Silt Ejectors

• Smolt screens

• Under sluices

• Divide wall

INTAKE GATES:• Gates are installed on the crest of the dam.

• Permit a temporary lowering of the crest level in time of flood.

• Vertical and Radial gates can also used in low level passages through the base of a dam.

INTAKE GATES:VERTICAL-LIFT GATES

• The vertical-lift gate, with wheels (rollers) at each end, moves vertically in slots formed in the piers and consists of a skin plate and horizontal girders that transmit the water load into the piers

• Lift gates can be operated under moderate heads, but not under reverse head conditions.

• Vertical-lift gates have been designed for spans in excess of 100 ft.

• High vertical-lift gates may consist of two or more sections in order to facilitate storage or ease passing of ice and debris.

RADIAL ARM (Tainter) GATES

• Consist of a moveable framework is the form of a sector of a circle.

• Economical to install, operate, and maintain.

• More efficient at partial openings than vertical-lift gates.

• Less liable to vibration than vertical-lift gates.

• No capacity of passing trash except in their fully open position.

• Frictional resistance is less as compare to vertical-lift gate of equivalent size.

• Generally used for head range of 200-250 feet.

Radial Gates at Älvkarleby, Sweden

Jhimruk Power Plant, Nepal

TRASH RACKES & SCREENS :

•Trashracks are usually positioned in forebay or intake structure as a means of excluding floating and

submerged debris, thereby preventing damage to the power plant, plant equipment, or waterway.

• secondary benefits of trashrackes include the protection of boaters, swimmers, and operation personnel .

•Trashrackes have been used as a method of fish exclusion.

•A trash rack is made up of one or more panels, fabricated from a series of evenly spaced parallel metal bars.

bars (from 100 mm to 300 mm between bars) used to reduce the work of the automatic trash rack cleaning

equipment.

•Trashrack bar sizes should not be less than 2 inches X 0.5 inch. This size is based on minimum section

required to resist corrosion.

•The trashrack bars are slightly off vertical and with the flow with slope of 1 horizontal to 4 vertical.

•The maximum possible spacing between the bars is generally specified by the turbine manufacturers. Typical

values are :

20-30 mm for Pelton turbines,

40-50 mm for Francis turbines and

80-100 mm for Kaplan turbines.

Fig:-Panauti power plant, nepal

Smolt Screens At Cruachan Power Station, Scotland

Fish ladder :• Provided just by the side of the divide wall for the

free movement of fishes.

• The tendency of fish is to move from upstream to

downstream in winters and from downstream to

upstream in monsoons.This movement is essential

for their survival.

• Due to construction of weir or barrage, this

movement gets obstructed, and is detrimental to the

fishes.

• In the fish ladder, the fable walls are constructed in a

zigzag manner so that the velocity of flow within the

ladder does not exceed 3 m/sec.

• The width, length and height of the fish ladder

depend on the nature of the river and the type of the

weir or barrage.

Floor baffles fish pass on the river Thames (UK)A small fish ladder on the River Otter, North America

Pool fish pass with triangular weirs at Sarrancolin dam on the Neste River (France)

The Kotri Barrage on river Indus near Hyderabad

ICE,LOG,AND TRASH BOOMS:

Floating boom use to perform one or more of the following functions:

• Deflection of logs and trash from the intake screens.

• Deflection of ice away from the intake.

• Prevention of the boats from being carried into the intake. ICE BOOMS:

• Ice booms are generally required to prevent blockage of intakes resulting in increased head loss and possible damage to screens.

BOAT RESTRAINING BARRIERS:

• The primary purpose of boat barriers is to physically restrain boaters from entering hazardous water near power intakes.

• Restraining barriers should be placed at the upstream end of such channels, preferably at least 300 feet from the channel entrance (Federal Energy Regulatory Commission,1992).

Where possible , the boom should be planned to facilitate trash removal out of the water, the boom should be angled between 30° to 45° to the direction of flow.

Steel pontoons link to form the ice boom.

The ice boom from above. A boom that catches garbage in the Bronx River catches plenty

SILT REGULATING WORKS:

Silt Excluders :

• Silt excluders are those works which are constructed on the bed of the river, upstream of the head regulator. The clearer water enters the head regulator and silted water enters the silt excluder. In this type of works, the silt is, therefore,, removed from the water before in enters the canal.

• Designed such that the top and bottom layers of flow are separated with the least possible disturbance

Silt Ejectors :

• Silt ejectors, also called silt extractors, are those devices which extract the silt from the canal water after the silted water has traveled a certain distance in the off-take canal. These works are, therefore, constructed on the bed of the canal, and little distance downstream from the head regulator.

…..CONTINUE

Location:

• If near head regulator, silt will be in suspension

• If too far away than result in silting of canal.

UNDER SLUICES :• Also known as scouring sluices.

• The under sluices are the openings provided at the base of the weir or barrage.

• These openings are provided with

adjustable gates. Normally, the gates are

kept closed.

• The suspended silt goes on depositing in front of the canal head regulator.

• When the silt deposition becomes

appreciable the gates are opened and the

deposited silt is loosened with an agitator

mounting on a boat.

• The muddy water flows towards the downstream through the scouring sluices.

• The gates are then closed. But, at the period of flood, the gates are kept opened.

The main functions of under-sluices are:

• To maintain a well defined deep channel

approaching the canal head regulator.

• To ensure easy diversion of water into the

canal through the canal head regulator even

during low flow.

• To control the entry of silt into the canal

• To help scouring and of the silt deposited

over the under-sluice floor and removing

towards the downstream side.

Sanjay Vidyut Pariyojna Bhaba,Kinnaur District, HP,India

Obra Dam & Power House,Mirzapur district, Uttar pradesh,india

DIVIDE WALL :

• The divide wall is a long wall constructed

at right angles in the weir or barrage, it

may be constructed with stone masonry or

cement concrete.

• On the upstream side, the wall is extended

just to cover the canal head regulator and

on the downstream side, it is extended up

to the launching apron.

The functions of the divide wall are as follows:

• To form a still water pocket in front of the

canal head so that the suspended silt can

be settled down which then later be

cleaned through the scouring sluices from

time to time.

• It controls the eddy current or cross current

in front of the canal head.

• It provides a straight approach in front of

the canal head.

• It resists the overturning effect on the weir

or barrage caused by the pressure of the

impounding water.

Verbadra barrage , haridwar - Google Maps

REFERENCES:

• A.A. Fulton, “Civil engineering aspects of Hydro-Electric Development in Scotland”, Journal of institution of civil engineers, jan. 1952.

• Hydroelectric engineering practice, Vol-I, Civil engineering, by J.Guthrie Brown.

• Guidelines for design of Intakes for Hydroelectric Plants, by ASCE.

• www.google.co.in

• https://maps.google.co.in

• http://ccpro.in/obra%20dam%20and%20power%20house.aspx

• http://ccpro.in/SanjayVidyutPariyojna.aspx

• http://www.indiamart.com/godbole-gates-limited/products.html

• http://library.water-resources.us/docs/MMDL/FLD/Feature.cfm?ID=7

• http://fixthepumps.blogspot.in/2010/08/gates.html

• http://civilthought.com/wp-content/uploads/2012/09/Typical-layout-of-diversion-head-works.jpg