Hydropower water conveyance systam

GAZIANTEP UNIVERSITY
FACULTY OF ENGINEERING
DEPARTMENT OF CIVIL ENGINEERING
HYDROPOWER ENGINEERING
WATER CONVEYANCE SYSTEM
Submitted by:
KHABAT STAR MOHAMMED
MARIF MAHMOOD KARIM
ISRAA NAJAT JABBAR
YASIR SHAKIR MAHMOOD
Submitted to :
Doç.Dr.Aytaç Güven

Water Conveyance system
Introduction
Any structure that conveys water from
one location to another.

Hydropower Block Diagram
Plan ( 1 )

Definition of diversion head work
A structure constructed across a river to raise
the normal water level and drive the required
supply in to main canal or power canal

Diversion Head work
Fig. ( 1 )

Components of diversion
head work
1. Barrage or weir
2. Canal head regulator
3. Divide wall
4. Fish ladder
5. Under sluice portion
6. Silt excluder
7. Marginal bunds
8. Guide bank

Function of head work
1. A head work raises the water level in the
river.
2. It regulates the intake of water into the canal.
3. It also controls the entry of silt into the canal.
4. A headwork can also store water for small
periods of time.
5. Reduces fluctuations in the level of supply in
river.

What is intake
A hydraulic-engineering installation for
obtaining water from a source of supply
(river, lake, reservoir, and so on) for
purposes of hydroelectric power
engineering, water supply, or irrigation.

Elements of intake
1. Trash rack and supporting structure.
2. Smolt screens.
3. Bell mouth entrance.
4. Gate slot closing devices with air vents.
5. Ice, log trash boom.
6. Silt excluders and silt ejectors.
7. Under sluices.

1- Trash rack
2- screen
• A trash rack is a wooden or metal structure, that
prevents water-borne debris (such as logs,
boats, animals, masses of cut waterweed, etc.)
from entering the intake of a water mill,
pumping station or water conveyance. This
protects penstock, and sluice gates from
destruction during floods..
• Usually positioned in forebay or intake
structure.

Trash Rack
Trash rack Trash rack

Removing or cleaning process to
trash rack

4 – gate slot closing
It is control regulates the entry of water into the
intake.

5- ICE,LOG,AND TRASH
BOOMS
Floating boom use to perform one or more of the
following functions
1. Deflection of logs and trash from the intake
screens.
2. Deflection of ice away from the intake.
3. Prevention of the boats form being carried into
the intake

6- silt excluders and silt ejectors
• Silt Control Devices
A. Silt Excluder: The silt excluder is located on
the u/s of diversion weir and in front of the
head regulator and the object is to remove silt
that has entered in the stilling basin through
scouring sluices.
B.Silt Ejector: Silt Ejector is located in the
canal take off from the diversion weir it ejects
the silt that has entered in the canal

Silt control
Silt excluder Silt Ejector

LOCATION OF INTAKE
The various factors influencing the choice of location of
intake structure are:
1- Type of storage reservoir
2- Location and type of dam/weir
3- Type of water conductor system that is canal or
tunnel
4- Topographical features of the river.
5- should not be located on curves or at least on shape
curves
6- should remain easily accessible during floods.
7- located at place from where can draw water even
during the driest period of the year

TYPE OF INTAKE
•Depending on the function served and the range in
reservoir head under which it is to operate,
•The discharging capacity and frequency of the reservoir
drawdown, intake for hydroelectric projects or more
elaborate structure raised as a tower above maximum
reservoir level.

A- According to source
1- River Intake

B- According to position of intake
• An Intake structure which remains entirely under water during
its operation is termed as submerged intake.
• It is provided where the structure serves only as an entrance to
the outlet required.
• The conduct intake may be inclined, vertical or horizontal in
accordingly with the intake requirements.
• An inclined intake may be provided with gates and operated
on the upstream slopes of a low dam.
1-submerged intake

2- Exposed intake
• Is in the form of well or tower constructed
near the bank of river or in some cases even
away from the bank of river, they are more
common due to ease in operation and
maintenance .

C – According to presence of water in
the tower
• In dry intake tower the entry ports are directly
connected with the withdrawal conduit and water
inside the tower when gates are in a closed
position.
• Dry Intake tower has a merit that the intake tower
being dry is made accessible for inspection and
operation besides that the water can be withdrawn
from any level by opening the port at that level.
1- Dry intake tower

2- Wet Intake Tower
• A wet intake tower has entry ports at various levels and
the vertical shaft is filled with water up to reservoir
level.
• It differs from the dry intake tower is that the water
enters from the ports into the tower and then into the
withdrawal conduct through separate gated openings.

QUALITY WATER
1- Location of intake is required to be such as to draw
the best quality of water from the reservoir.
2- Depth of water at intake is important.
3- Quality of water varies at different levels in the
reservoir and it is necessary to draw water from
different elevation of the reservoir at different
seasons of the Year for which multi-level intakes
are frequently provided.

Water conveyance system
The main components are :
A. Open channel flow
system
B. Pressure flow system

Open channel flow and pressure flow systems

What is Open channel?
A covered or uncovered conduit in which
liquid (usually water) flows with
its top surface bounded by the atmosphere. Typical
open channels are
rivers, streams, canals, flumes, or
sewers, and water-supply or hydropower aqueducts

Classification of open channel
Based on :
1. shape
2. natural / artificial (man made)
3. change in cross section and slope
4. boundary characteristic

Classification based on a shape
1.Rectangular
2.Trapezoidal
3. Triangular
4. semi-Circular
5.Parabolic
6.Compound

Trapezoidal open
channel
Rectangular
open channel

semi-circular
open channel
Triangular
open channel

Compound open
channel
Parabolic
open channel

Open channel geometric relationships for varies cross-
section

Classification based on
• Natural channel
All watercourses that exist naturally on the
earth like Brooke ,creeks , tidal
• Artificial channel
Those constructed to perform various project
requirements and termed canals
Flumes , culverts

Natural channel Artificial channel

Classification based on change in
slope and cross section
Prismatic : a channel in which cross section shape
and size also the bottom slope are constant , most of
man-made channels(artificial) are prismatic channels
like rectangular ,trapezoidal , triangular ,circular
channels
• Non – prismatic : slope or cross section
changes, all natural channels generally have varying in
cross section and consequently are non- prismatic.

Classification based on boundary
characteristic
Mobile boundary channel Rigid boundary channel

Forebay
• A forebay is an artificial pool of water in
which located before and connected with
penstocks
• Provided in case of run-off- river plants
• The major use of forebay was to distribution
Flow of water in to penstocks , store water
which is rejected by hydropower plant
, Containing a trash rack and bye-pass channel.

Forebay connecting with penstock and
Containing a trash rack and bye-pass channel

Trashrack that which used to prevent undesirable
material (planate , dead animals) for entering to
penstock that may choke the system

BANK AND CHANNEL
PROTECTIVE LINING
Lining are Protective layer artiﬁcial or natural
material which placed in a channel bottom and
banks that may be used to:
• prevent erosion resulting from high velocities
of water
• breaking down resulting from entering water
in Cracks and gaps
• shapely appearance and proper

Lining classification
The main classifications of open channel
linings are based on the material which
that covered the channel and we have two
items :
• Rigid Linings
• Flexible linings

Rigid Linings
Rigid linings are generally constructed of
concrete, pvc, or concrete blocks pavement
they are more expensive , prevent
infiltration and Require periodic
maintenance
whose smoothness offers a higher capacity
for a given cross-sectional area and Higher
Velocities
The following are examples of Rigid
Linings:

Pri –cast concrete channel
concrete blocks channel Pvc channel

Flexible linings
Flexible linings have several advantages compared to
rigid linings They are generally less expensive,
permit infiltration and exhilaration and can be
vegetated to have a natural appearance, have self-
healing qualities which reduce maintenance
In many cases flexible linings are designed to
provide only transitional protection against erosion
The following are examples of Flexible linings:

Grasses or natural vegetation
Grass linings are suitable for applications where they will be
exposed to periodic relatively slow flow of water
This type of lining has a pleasing appearance,
is economical and is not subject to damage as a result of
undermining or settlement of the supporting soils

B:Pressure flow system
1- Low-pressure conduits and tunnels
2- High-pressure conduits, commonly called the
penstocks

Tunnels
Tunnels can be designed as underground passages
made without removing the overlying rock or soil.

TBM: also known as a "mole", is a machine used to excavate
tunnels with a circular cross section through a variety of soil and
rock strata. They may also be used for micro tunneling. They can
bore through anything from hard rock to sand.

Layout of a tunnel alignment
The first aspect that needs to be decided for a tunnel is the
alignment .

Hydraulic tunnels can be divided
into the following categories:
1- Pressure tunnels
2- Free flowing tunnels
Depending on their shape, tunnels may be
classified as:
1- D-shaped
2- Horse-shoe shaped
3- Circular shaped
4- Egg Shaped and Egglipse Sections

Tunnel section
Cross – section of a tunnel depends on the
following factors:
1- Geological conditions prevailing along the
alignment,
2- Structural considerations, and
3- Hydraulic requirements,
4- Functional requirements.

D-SHAPED SECTION:
• D-shaped section is found to be suitable in tunnels located
in good quality, intact sedimentary rocks and massive
external igneous, hard ,compacted , metamorphic rocks
where the external or internal pressures.

Horse-Shoe section
This sections are strong in their resistance to external pressure. Quality of rock and
adequate rock cover in terms of the internal pressure to which the tunnel is subjected
govern the use of these sections. This section offers the advantage of flat base for
constructional ease and change over to circular section with minimum additional
expenditure in reaches of inadequate rock cover and poor rock formation.

Note: For tunnel excavated to horse -shoe section
and concreted to circular section.

Egg Shaped and Egglipse Sections
• Where the rock is stratified soft and very closely laminated (as
laminated sand stones, slates, micaceous schists , etc) and where the
external pressure and tensile forces in the crown are likely to be high
so as to cause serious rock falls, those sections should be
considered.

Circular section
The circular section is most suitable from structural consideration. It is
difficult to excavation where cross-sectional area is small. In case where the
tunnel is subjected to high internal pressure, but does not have good quality
of rock and/or adequate rock cover around it. circular section is considered
to be most suitable.

Steel supports
These are built of steel sections, usually I-sections, either shaped or
welded in pieces in the form of a curve or a straight section

ROOF BOLTS OF ROCK
• Rock bolts were used to support the roof and walls of major structures
such as tunnels and power stations
• These steel bolts, of different length and spacing, were inserted into the
rock where they were found to be an excellent anchorage for the rock.

Tunnel Lining
• Tunnel linings: main types. Tunnel linings are grouped into three
main forms some or all of which may be used in the construction
of a tunnel.
• Temporary ground support
• Primary lining
• Secondary lining
• Temporary ground support: In rock tunnels where the ground has
insufficient stand-up time to allow the construction of the
primary lining some distance behind the face.
• Primary lining. A primary lining is the main structural component
of the tunnel support system which is required to sustain the
loads and deformations that the ground may induce during the
tunnel's intended working life.
• Secondary lining. Various tunnels require smooth bore profiles
for their intended use, eg sewer and water tunnels or aesthetic
finishes for public usage, eg highway and pedestrian tunnels.

Tunnel Grouting: This is a cement mortar with
proportion of cement, sand and water in the ratio 1:1:1 by weight
usually, though it may be modified suitably according to site
conditions.
types of grouting:
• Back-fill grouting :to fill spaces between initial lining and
rock.
• − Contact grouting: to fill gaps between initial lining and plug
concrete.
• − Consolidation grouting: to improve the quality of the
surrounding rock.
• − Curtain grouting: To preventing water seepage from the
waterway end portion.

• Pattern of Holes for Grouting
• Backfill or Contact Grouting - Backfill grouting is limited to
the arch portion of the tunnel. The number of holes normally
three in each section, the pattern being staggered in each
subsequent sections located 3 m center to center.

Consolidation or Pressure Grouting -
• Consolidation grouting is done to consolidate the shattered rock
all around the cavity. The pattern of holes is such that these are
distributed all along the periphery but staggered in alternate
sections space 3 m center to center. The number of holes may be
four for smaller tunnels six for bigger tunnels.

Consolidation or Pressure Grouting 6
holes

What is surge tank
Surge tank is located between the headrace pressure conduit
and the steeply sloping penstock pipe and is designed either as
a chamber excavated in the mountain or as a tower raising
high above the surrounding terrain.

The main functions of a surge tank are:
• Reduces the amplitude of pressure
fluctuations by reflecting the incoming
pressure waves.
• Improves the regulating characteristics of a
hydraulic turbine because; it reduces the
water starting time of a hydropower scheme.
• Surge tanks, which are used to dissipate
water hammer pressure

Water Hammer
• Water Hammer is a pressure surge or wave that
occurs when there is a sudden momentum change
of a fluid (the motion of a fluid is abruptly forced
to stop or change direction) within an enclosed
space (Water Hammer).
• This commonly occurs in pipelines when a valve
is closed suddenly at the end of a pipeline where
the velocity of the fluid is high. The pressure
wave created will propagate within the pipeline.

Depending upon its configuration, a surge tank may be
classified as follows;
• 1- Simple surge tank: A simple surge tank is a shaft
connected to pressure tunnel directly or by a short
connection of cross-sectional area not less than the area of
the head race tunnel.

2- Orifice surge tank: if the entrance to the surge tank
is restricted by means of an orifice, it is called an orifice
tank.

3- Differential surge tank: an orifice tank having a
riser is called differential tank.

4-Closed surge tank:
If the top of the tank is closed and there is compressed air
between the water surface and the top of the tank, then the
tank is called closed surge tank, a tank with air cushion.

5-Surge Tank with Spilling Chamber

What is penstock ?
•A penstock is one of the parts of conveyance system that
construct from a steel or reinforced concrete to resist high
pressure in the water conveyance system

• What is the Function of penstock?
• It’s function is conveying water from for bay
or surge tank to the turbine in the power hous
and it’s help to increase the kinetic energy of
water that comes from the end of head race.

Type of penstock
1. Buried penstocks 2. Exposed penstocks

Buried penstocks:
are supported continuously on the soil at the bottom of a trench
backfilled after placing the pipe. The thickness of the cover over
the pipe should be about 1.o to 1.2 m.
Advantage:
• The soil cover protects the penstock against effect of
temperature variations,
• It protects the conveyed water against freezing.
• Buried pipes do not spoil the landscape.
• They are safer against rock slides, avalanches and falling
trees.

Disadvantage:
• the inspection and faults cannot be determined easily.
• It’s installation expensive Especially For large diameters and
rocky soils.
• On steep hillsides, especially if the friction coefficient of the
soil is low, such pipes may slide.
• Maintenance and repair of the pipe is difficult.

are installed above the terrain surface and supported on piers
(briefly called supports or saddles). Consequently, there is no
contact between the terrain and the pipe itself, and the support is
not continuous but confined piers.
Advantage:
•The possibility of continuous and adequate inspection during
operation.
•Its installation is less expensive in case of large diameters of
rocky terrain.
•Safety against sliding may be ensured by properly designed
anchorages.
•Such pipes are readily accessible and maintenance and repair
operations can be carried out easily
Exposed penstocks:

Disadvantage:
• Full exposure to external variations in temperature.
• The water conveyed may freeze.
• Owing to the spacing of supports and anchorages
significant longitudinal stresses may develop especially
in pipes of large diameters designed for low internal
pressures

Design of penstock:
• According to the Bureau of Indian Standards code IS:
11625-1986 “Criteria for hydraulic design of
penstocks” The determination of penstock diameter
based on the following losses may be expected for a
penstock:
a. Head loss at trash rock .
b. Head loss at intake entrance .
c. Friction losses, and .
d. Other losses as at bends, bifurcations, transitions,
values, etc.

Bends
Depending on topography, the alignment of the penstock is often
required to be changed, in direction, to obtain the most
economical profile.

Reducer piece:
In the case of very long penstocks, it is often necessary to reduce the diameter
of the pipe as the head on the pipe increases. This reduction from one
diameter to another should be effected gradually by introducing a special
pipe piece called reducer piece.

Branch pipe: Depending upon the number of
units a single penstock feeds.

Expansion joints :are installed in exposed
penstocks to prevent longitudinal expansion or
contraction when changes in temperature occur.

Manholes: Manholes are provided in the course
of the penstock length to provide access to the
pipe interior for inspection, maintenance and
repair.

Air vents and valves: These are provided on
the immediate downstream side of the control gate or
valve to facilitate connection with the atmosphere.

• Tailraces:
After passing through the turbine the water
returns to the river trough a short canal called a
tailrace.

Hydropower water conveyance systam

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