cve 471 - 5. water supply 2 - middle east technical university
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CVE 471 Water Resources Engineering 1/58
Assist. Prof. Dr. Bertuğ Akıntuğ
Civil Engineering ProgramMiddle East Technical University
Northern Cyprus Campus
CVE 471CVE 471WATER RESOURCES ENGINEERINGWATER RESOURCES ENGINEERING
WATER SUPPLYWATER SUPPLY
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55. WATER SUPPLY. WATER SUPPLY
Overview
Elements of Municipal Water Supply SystemsDistribution ReservoirsPipesPumps and Valves
Hydraulics and Operation of Gravity PipelinesDesign of Transmission Lines
Gravity LinesPumped LinesMixed Lines
Construction and Maintenance of Municipal Water Supply Systems
CVE 471 Water Resources Engineering 3/58
55. WATER SUPPLY. WATER SUPPLY
Elements of Municipal Water Supply System
Water is conveyed from a source or combination of sources to community in mainly closed conduits.
pressurized flow is possiblepollution control
Possible element of a water transmission system:canals and flumesgrade aqueductsgrade tunnelspipelinesvalvespumpspressure reducing chambers etc….
1915-19 Winnipeg, Manitoba, Canadahttp://www.mhs.mb.ca/docs/pageant/24/winnipegaqueduct.shtml
CVE 471 Water Resources Engineering 4/58
55. WATER SUPPLY. WATER SUPPLY
Elements of Municipal Water Supply System
Transmission pipelineshttp://www.wau.boku.ac.at/fileadmin/_/H81/H811/Skripten/811356/05_Supply_Storage_distribution.pdf
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55. WATER SUPPLY. WATER SUPPLY
Elements of Municipal Water Supply System
Typical arrangement of a municipal water supply system
Distribution reservoirs are designed to meet the hourly variations in water demand and to store extra water for fire fighting and emergencies.
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55. WATER SUPPLY. WATER SUPPLY
Elements of Municipal Water Supply System
In the main transmission line Qdesign= Dmd = Dad x (P.F.)day
In a main feeder Qdesign= Dmh = Dmd x (P.F.)hour
OR
Qdesign= Dmh = Dad x (P.F.)hour x (P.F.)day
CVE 471 Water Resources Engineering 7/58
55. WATER SUPPLY. WATER SUPPLY
Elements of Municipal Water Supply System
A water distribution network is normally composed of pipes, valves, hydrants, and pumps. Distribution of water is possible by
gravity (storage reservoir is required at a sufficient altitude)pump without storage (may be required during any emergency), andpump with storage (the most common way).
Types of distribution systems depends on street plantopography,location of supply works,level of service dictated.
CVE 471 Water Resources Engineering 8/58
55. WATER SUPPLY. WATER SUPPLY
Elements of Municipal Water Supply System
Types of distribution systems: a) a branching pattern with dead ends,b) a gridiron pattern,c) a gridiron pattern with central feeder.
A branching pattern with dead endssuitable for strip-shaped districts where water flow in one directionduring any repair downstream of the section cannot take water
A gridiron patternpreferred for flat and wide terrains
A gridiron pattern with a central feederpreferred as the auxiliary main is in a looped pattern
CVE 471 Water Resources Engineering 9/58
55. WATER SUPPLY. WATER SUPPLY
Overview
Elements of Municipal Water Supply SystemsDistribution ReservoirsPipesPumps and Valves
Hydraulics and Operation of Gravity PipelinesDesign of Transmission Lines
Gravity LinesPumped LinesMixed Lines
Construction and Maintenance of Municipal Water Supply Systems
CVE 471 Water Resources Engineering 10/58
55. WATER SUPPLY. WATER SUPPLY
Elements of Municipal Water Supply System
Distribution ReservoirsIn large cities (population > 100,000) pumping stations and distribution reservoirs are operated in conjunction with each other.Pumping stations usually pump the average daily demand to distribution reservoirs during the minimum demand hours of the day.Distribution reservoir release the water when the demand is above the average daily demand to meet the fluctuations in use.Location: as close as the center of use as possible.Water Level: high enough to permit gravity flow at satisfactory pressure.
CVE 471 Water Resources Engineering 11/58
55. WATER SUPPLY. WATER SUPPLY
Elements of Municipal Water Supply System
Distribution Reservoirs (con’t)May be located in critical points in the city in such a way that the hydraulic grade line is still above the highest storey buildings.Elevated tanks: circular cross-section (cylinder gives a max. volume).Buried reservoirs: rectangular
cross-section (easy to construct)Small: concrete or stone masonryLarge: reinforced concrete with dividing walls
Cylindrical Reservoirs: reinforces concrete or steel
CVE 471 Water Resources Engineering 12/58
55. WATER SUPPLY. WATER SUPPLY
Elements of Municipal Water Supply System
Distribution Reservoirs (con’t)A fill layer of about one meter thick is placed.Lower temperature in summer (better quality and taste)
Buried distribution reservoirhttp://www.wau.boku.ac.at/fileadmin/_/H81/H811/Skripten/811356/05_Supply_Storage_distribution.pdf
CVE 471 Water Resources Engineering 13/58
55. WATER SUPPLY. WATER SUPPLY
Elements of Municipal Water Supply System
Distribution Reservoirs (con’t)
Buried distribution reservoirhttp://www.wau.boku.ac.at/fileadmin/_/H81/H811/Skripten/811356/05_Supply_Storage_distribution.pdf
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55. WATER SUPPLY. WATER SUPPLY
Elements of Municipal Water Supply System
Distribution Reservoirs (con’t)The capacity of a distribution reservoir is determined by the summation of the following components:
Storage to meet hourly fluctuations,Required storage to put out a fire with certain duration (Cfire)Storage to meet emergencies
CVE 471 Water Resources Engineering 15/58
55. WATER SUPPLY. WATER SUPPLY
Overview
Elements of Municipal Water Supply SystemsDistribution ReservoirsPipesPumps and Valves
Hydraulics and Operation of Gravity PipelinesDesign of Transmission Lines
Gravity LinesPumped LinesMixed Lines
Construction and Maintenance of Municipal Water Supply Systems
CVE 471 Water Resources Engineering 16/58
55. WATER SUPPLY. WATER SUPPLY
Elements of Municipal Water Supply System
PipesPipes materials:
reinforced concrete (no corrosion problem),asbestos cement (limited use cancerous effect of asbestos fibers),ductile iron (corrosion problem interior is coated with cement),steel (good for large diameter and high pressure, buckling under high negative pressure)plastic (widely used, highly smooth, light, easy to install and remove)
The minimum pipe size required in a distribution network is dictated by the population.
CVE 471 Water Resources Engineering 17/58
55. WATER SUPPLY. WATER SUPPLY
Overview
Elements of Municipal Water Supply SystemsDistribution ReservoirsPipesPumps and Valves
Hydraulics and Operation of Gravity PipelinesDesign of Transmission Lines
Gravity LinesPumped LinesMixed Lines
Construction and Maintenance of Municipal Water Supply Systems
CVE 471 Water Resources Engineering 18/58
55. WATER SUPPLY. WATER SUPPLY
Elements of Municipal Water Supply System
PumpsPumps: mechanical energy potential energyTypes of pumps are named according to the direction of the movement of water from the rotating element of the pump (impeller).The specific speed:
where Q: discharge (m3/s)N: rotative speed of impeller (rpm)Hp: Head (m)
2/3p
sHQN
n =
CVE 471 Water Resources Engineering 19/58
55. WATER SUPPLY. WATER SUPPLY
Elements of Municipal Water Supply System
Pumps (con’t)Centrifugal Pumps:
For the requirement of high heads (low ns).Impeller in series having radial flow characteristics are adopted.
http://en.wikipedia.org/wiki/File:CetriFugal_Pump.jpg http://www.thomasnet.com/articles/pumps-valves-accessories/centrifugal-principles
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55. WATER SUPPLY. WATER SUPPLY
Elements of Municipal Water Supply System
Pumps (con’t)Axial-flow Pumps:
For greater flow rates under low heads (high ns).Having axial flow characteristics with respect to the pump axis.
http://en.wikipedia.org/wiki/File:Axial_2.png http://www.directindustry.com/prod/weir-minerals/axial-flow-pump-23306-376724.html
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55. WATER SUPPLY. WATER SUPPLY
Elements of Municipal Water Supply System
Pumps (con’t)Mixed-flow Pumps:
For medium head and discharge (medium ns).
http://www.shakthipumps.com/download/mixed-flow-pumps.pdfhttp://www.pattersonpumps.com/axial.html#
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55. WATER SUPPLY. WATER SUPPLY
Elements of Municipal Water Supply System
Pumps (con’t)Power of the pump:
where Pp: the power (kW).γ: specific weight of water (kN/m3)Q: discharge (m3/s)Hp: head of the system by the pump (m)ηp: the efficiency of the pump
p
pp
QHP
ηγ
=
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55. WATER SUPPLY. WATER SUPPLY
Elements of Municipal Water Supply System
Pumps (con’t)Multiple pump operations are often used to increase the discharge or head.
Pumps in Series: Increase the head
Pumps in Parallel: Increase in discharge
CVE 471 Water Resources Engineering 24/58
55. WATER SUPPLY. WATER SUPPLY
Elements of Municipal Water Supply System
Valves Sluice or gate valves are used to isolate the flow especially during repair works.
http://en.wikipedia.org/wiki/Gate_valve
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55. WATER SUPPLY. WATER SUPPLY
Elements of Municipal Water Supply System
Valves Butterfly valves are widely used at the exits of distribution reservoirs for regulation or isolation purposes.
http://en.wikipedia.org/wiki/Butterfly_valvehttp://www.scanco.no/produkter_ventiler.php
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55. WATER SUPPLY. WATER SUPPLY
Elements of Municipal Water Supply System
Valves Check valves are used to stop flow automatically in the reverse direction.
http://www.checkall.com/valvestyles/un3/un3enlargedphoto.htm
http://www.spiraxsarco.com/resources/steam-engineering-tutorials/pipeline-ancillaries/check-valves.asp
http://www.checkvalves.co.uk/
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55. WATER SUPPLY. WATER SUPPLY
Elements of Municipal Water Supply System
Valves Hydrants are those appurtenances used for the withdrawal of pressurized flow from the network for fire fighting.
http://en.wikipedia.org/wiki/Fire_hydrant
CVE 471 Water Resources Engineering 28/58
55. WATER SUPPLY. WATER SUPPLY
Overview
Elements of Municipal Water Supply SystemsDistribution ReservoirsPipesPumps and Valves
Hydraulics and Operation of Gravity PipelinesDesign of Transmission Lines
Gravity LinesPumped LinesMixed Lines
Construction and Maintenance of Municipal Water Supply Systems
CVE 471 Water Resources Engineering 29/58
55. WATER SUPPLY. WATER SUPPLY
Hydraulics and Operation of Gravity Pipelines
CVE 471 Water Resources Engineering 30/58
55. WATER SUPPLY. WATER SUPPLY
Hydraulics and Operation of Gravity Pipelines
when (inflow > Qmax) Q - Qmax spills over the reservoirwhen (Q0 < inflow < Qmax) 0 < reservoir water level < Hmax
when (inflow < Q0) free surface flow in the pipe (empty reservoir).
To prevent free surface flow in the pipe use control valve at the pipe exitThe valve dissipates the excess potential energy, Hv.
Then flow is pressurized in the pipe and the water level in the reservoir is controlled.
CVE 471 Water Resources Engineering 31/58
55. WATER SUPPLY. WATER SUPPLY
Overview
Elements of Municipal Water Supply SystemsDistribution ReservoirsPipesPumps and Valves
Hydraulics and Operation of Gravity PipelinesDesign of Transmission Lines
Gravity LinesPumped LinesMixed Lines
Construction and Maintenance of Municipal Water Supply Systems
CVE 471 Water Resources Engineering 32/58
55. WATER SUPPLY. WATER SUPPLY
Design of Transmission Lines
The pipe size should be determined to meet future requirements.The system should confirm to the required hydraulic performance:
velocity criteriapressure criteria etc…..
In this section design principles ofgravity lines,pumped lines, andmixed lined
are introduced.
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55. WATER SUPPLY. WATER SUPPLY
Design of Transmission Lines
Design of Gravity LinesFor a gravity pipeline, neglecting operating cost, the optimum diameter minimizes the capital cost of the pipeline.
The optimum diameter minimum diameter which can convey the specified design discharge with the available gravity head.
In gravity lines there are several design criterions:Velocity: 0.5 – 2.0 m/sPressure head: 3-5 m – 80 m
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55. WATER SUPPLY. WATER SUPPLY
Design of Transmission Lines
Design of Gravity Lines (con’t)
Step 1:Determine the control points (C,E,F) and their topographic elevations zc, zE, zF.Add the minimum required pressure head Pmin/γ to these elevations.Determine the energy grade line slopes (S1, S2, S3), between the reservoir and the control points and select minimum slope.
( )AC
cALPzHS )/( min
minγ+−
=
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55. WATER SUPPLY. WATER SUPPLY
Design of Transmission Lines
Design of Gravity Lines (con’t)
Step 2:Compute the pipe diameter for line A-C. Using Darcy-Weisbach equation,
and select the nearest larger commercial available diameter, D.
5/1
min2
28
=
SgfQDcom
π
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55. WATER SUPPLY. WATER SUPPLY
Design of Transmission Lines
Design of Gravity Lines (con’t)
Step 3:Compute velocity
If umin < u < umax, the selected diameter, D, is used in the projectIf u < umin, a booster pump may be installed at the reservoir site to increase the velocity to umin.
4/2DQu
π=
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55. WATER SUPPLY. WATER SUPPLY
Design of Transmission Lines
Design of Gravity Lines (con’t)
Step 3: (con’t)The additional head supplied by the booster pump, Hp, is compute using
If u > umax, reduce the velocity to umax, by increasing the pipe diameter from Since the velocity, and hence headlosses
are reduced, install a pressure reduction valve or allow increased pressures along the pipeline if (P/γ) < (Pmax/γ)
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55. WATER SUPPLY. WATER SUPPLY
Design of Transmission Lines
Design of Gravity Lines (con’t)
Step 4:After determining the diameter for pipe segment A-B-C and computing the piezometric level at point C (HC), repeat the above procedure for the remaining segments C-D-E-F.Note that for the above example point E now becomes the control point.Therefore, first the diameter for segment C-D-E, and then the diameter of segment EF are determined.
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55. WATER SUPPLY. WATER SUPPLY
Design of Transmission Lines
Design of Gravity Lines (con’t)
Step 5:Install a control valve at point F, and determine the necessary headloss at the valve, to maintain pressurized flow at segment E-F.
CVE 471 Water Resources Engineering 40/58
55. WATER SUPPLY. WATER SUPPLY
Overview
Elements of Municipal Water Supply SystemsDistribution ReservoirsPipesPumps and Valves
Hydraulics and Operation of Gravity PipelinesDesign of Transmission Lines
Gravity LinesPumped LinesMixed Lines
Construction and Maintenance of Municipal Water Supply Systems
CVE 471 Water Resources Engineering 41/58
55. WATER SUPPLY. WATER SUPPLY
Design of Transmission Lines
Design of Pumped LinesFor a pumped line, the economical diameter is the one which minimizes the total cost.
investment cost of pipes (placement and installation costs),cost of pump,energy cost of operation (operation and maintenance costs).
A small diameter reduces initial cost but increases pumping and energy costs.
For the most economical diameter:
CVE 471 Water Resources Engineering 42/58
55. WATER SUPPLY. WATER SUPPLY
Design of Transmission Lines
Design of Pumped Lines (con’t)Step 1:
Compute the annual energy cost, CE, to overcome friction and static head:
where Pp: power of the pump.γ: the specific weight of water (kN/m3).Q: design discharge (m3/s).E: energy cost ($/KWh).t: annual operating hours.η: the pump efficiency.Hp: the required pump head (m). Hp=Hs+hfHs: the static head between the lower and upper reservoir (m)hf: the friction headloss along the pipe connecting these reservoirs.
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55. WATER SUPPLY. WATER SUPPLY
Design of Transmission Lines
Design of Pumped Lines (con’t)Step 1: (con’t)
Using Darcy-Weisbach equation, the annual energy cost, CE, can be expressed in terms of diameter D:
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55. WATER SUPPLY. WATER SUPPLY
Design of Transmission Lines
Design of Pumped Lines (con’t)Step 2:
Pipe cost, CD, per unit length for various diameters is obtained from manufacturers, and converted to annual cost, CP, :
where i : interest rate.N: economic life of the project in years.
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55. WATER SUPPLY. WATER SUPPLY
Design of Transmission Lines
Design of Pumped Lines (con’t)Step 3:
Initial pump cost, Cpi, is normally expressed in terms of monetary units per kW of installed power. The power of the pump in kW units is
where γ : the specific weight of water (kN/m3).Q: the discharge (m3/s)
The annual pump cost:
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55. WATER SUPPLY. WATER SUPPLY
Design of Transmission Lines
Design of Pumped Lines (con’t)Step 4:
Ignoring annual operation and maintenance costs, the economic diameter is obtained as the value corresponding to the minimum total annual cost.
Cp : annual cost of pipeCE: annual energy costCpump: pump costCT: total cost
CVE 471 Water Resources Engineering 47/58
55. WATER SUPPLY. WATER SUPPLY
Overview
Elements of Municipal Water Supply SystemsDistribution ReservoirsPipesPumps and Valves
Hydraulics and Operation of Gravity PipelinesDesign of Transmission Lines
Gravity LinesPumped LinesMixed Lines
Construction and Maintenance of Municipal Water Supply Systems
CVE 471 Water Resources Engineering 48/58
55. WATER SUPPLY. WATER SUPPLY
Design of Transmission Lines
Design of Mixed LinesA pipeline having both
gravitational and pumped flow rates.
Topographic elevation of point C is higher than the reservoir level.In such a case it is convenient to build a small reservoir at C.The pump may be
located at reservoir site A orlocated as a booster pump along the line.
Topographic elevation of point C is higher than the reservoir level.
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55. WATER SUPPLY. WATER SUPPLY
Design of Transmission Lines
Design of Mixed Lines (con’t)If the pump is located at reservoir site A, the economic pipe diameter can be computed considering line ABC as a pump discharge lineThe required pump head:
The diameter of line CD is then determined as a gravity pipeline.
CVE 471 Water Resources Engineering 50/58
55. WATER SUPPLY. WATER SUPPLY
Design of Transmission Lines
Design of Mixed Lines (con’t)If a booster pump is selected, then its location, X, along BC can be determined as follows:
Flow will be transmitted until the booster pump by gravity.Use any available diameters, that keep velocity within the limits (umin < u < umax).The location of booster pump(LBX, zX)
Then the economic pipe diameter for section X-C can be determined as that of a pumped discharge line.
Required Pump Head:
CVE 471 Water Resources Engineering 51/58
55. WATER SUPPLY. WATER SUPPLY
Design of Transmission Lines
Design of Mixed Lines (con’t)If a small diameter is used until the buster pump,
the initial cost will be lessthe energy cost will be high (the pump will be in at a lower elevation)
Note that for the booster pump applications the followings must also be considered:
cost of energy line transportation, andcost of employment of guards, etc…
CVE 471 Water Resources Engineering 52/58
55. WATER SUPPLY. WATER SUPPLY
Overview
Elements of Municipal Water Supply SystemsDistribution ReservoirsPipesPumps and Valves
Hydraulics and Operation of Gravity PipelinesDesign of Transmission Lines
Gravity LinesPumped LinesMixed Lines
Construction and Maintenance of Municipal Water Supply Systems
CVE 471 Water Resources Engineering 53/58
55. WATER SUPPLY. WATER SUPPLY
Construction and Maintenance of Municipal Water Supply Systems
The selection of suitable route for a pipeline has an important bearing on the capital cost and operation cost.
A pipeline route is selected fromaerial photostopographic and cadastral planson-site inspections, andother data available on the terrain, obstacle, and local services.
For suitable route Jointly consider Cost and Practicality.
The general level of pipeline route should be as close to hydraulic grade line as possible to minimize pressures and hence pipe costs.
CVE 471 Water Resources Engineering 54/58
55. WATER SUPPLY. WATER SUPPLY
Construction and Maintenance of Municipal Water Supply Systems
If a pipeline is laid parallel to the natural ground, then it will have many peaks and depressions as the natural ground surface.Air released from water and trapped at peaks
reduces the opening of the waterway,increases energy loss,may interrupt flow.
In this case, air valves are required.In order to minimize the number of air valves the pipeline can be laid
on a more straight profile deeper in the ground,close to the ground surface with a nearly straight profile and covered with earth-fill in depression along the route.
CVE 471 Water Resources Engineering 55/58
55. WATER SUPPLY. WATER SUPPLY
Construction and Maintenance of Municipal Water Supply Systems
The selection of profile is achieved by cost evaluations.In setting up the alternative profiles:
In order to minimize air entrainment problems: (pipe slope) > 0.005On very straight ground surfaces the minimum slope can be droped to 0.002.No upper limit for the maximum slope.
In long supply lines frequent changes in direction should be avoided in order to conserve head and pressure.sharp bends should also be avoided to reduce the dynamic impact of the water thrust.
The bends should be blocked with concrete to take the dynamic action.
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55. WATER SUPPLY. WATER SUPPLY
Construction and Maintenance of Municipal Water Supply Systems
Laying of pipes:excavation of trenches,transportation and handling of pipes and appurtenances,backfilling and repaving.
Pipes should be laid on firm beds in order to prevent the problems due to settlement.The dept of burial of pipes may be governed by
the depth of frost linethe external loads acting on the pipe
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55. WATER SUPPLY. WATER SUPPLY
Construction and Maintenance of Municipal Water Supply Systems