WS Chapter8 Print

8/13/2019 WS Chapter8 Print

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CH-7.0 RESERVOIRS and DISTRIBUTION SYSTEMASSIGNMENT # 1

1. Describe on the system of water supply.2. Why intermittent system is adopted for water

supply in Nepal besides its disadvantages?

3. What are various types of layout systems ofthe distributions?

4. Which layout system can be applied for theBhaktapur city?

5. Explain on methods of water supply.6. How does you prefer, the method of water

supply to a town?6/25/2013 1Chapter-7/Water Supply Engineering



CH-7.0 RESERVOIRS and DISTRIBUTION SYSTEMASSIGNMENT # 2

1. Derive the relation for pipe network byequivalent method using (i )Hazen William’s and(ii)Darcy’s formula, when pipes are in series.

2. Derive the relation for pipe network byequivalent method using (i )Hazen William’s and(ii)Darcy’s formula when pipes are in parallel.

3. Write the detail procedure to solve looped pipenetwork flow by Hardy Cross method (usingbalancing heads by correcting assumed flowmethod)?

6/25/2013 2Chapter-7/Water Supply Engineering



8.0 CONVEYANCE OF WATERConveyance from intake to treatment plant andtreatment plant to reservoir is called transmissionand reservoir to consumer tap is called distribution.

Water is under pressure always and hence the pipematerial and the fixture should withstand stressesdue to the internal pressure, vaccum pressure, waterhammer and temperature stresses.The selection of material is based on:

• Carrying capacity of pipe• Durability and life of pipe• Type of water to be conveyed and its corrosive action• Availability of fund• Maintenance and repair cost etc.

6/25/2013 Chapter-7/Water Supply Engineering 3



8.0 CONVEYANCE OF WATERREQUIREMENTS OF PIPE MATERIAL

1. It should be capable of with standing internal andexternal pressures

2. It should have facility of easy joints3. It should be available in all sizes, transport and

erection should be easy.4. It should be durable5. It should not react with water to alter its quality

6. Cost of pipes should be less7. Frictional head loss should be minimum8. The damaged units should be replaced easily.




8.1 DIFFERENT TYPES OF PIPES1. C.I. PIPES

ADVANTAGES Cost is moderate The pipes are easy to join The pipes are not subjected to corrosion The pipes are strong and durable Service connections can be easily made Usual life is about 100 years

DISADVANTAGESBreakage of pipes are large

The carrying capacity of these pipes decreases with theincrease in life of pipes.The pipes are not used for pressure greater than 0.7 N/mm2The pipes are heavier and uneconomical beyond 1200 mmdia.




8.1 DIFFERENT TYPES OF PIPES2. G.I PIPES

ADVANTAGESThe pipes are cheapLight in weight and easy to handle

The pipes are easy to joinDISADVANTAGES

The pipes are affected by acidic or alkaline

watersThe useful life of pipes is short about 7 to 10years.




8.1 DIFFERENT TYPES OF PIPES3. W.I PIPES

manufactured by rolling flat plate of metal toproper dia. and welding the edgesEasily cut, threaded and worked

Lighter than CI pipesMore costly and less durable than CI pipesDue to corrosion, use internal work inbuildingTo increase life, they are galvanized with zinc




8.1 DIFFERENT TYPES OF PIPES4. STEEL PIPES

ADVANTAGESNo. of Joining are less because these are available in long lengthsThe pipes are cheap in first costThe pipes are durable and strong enough to resist high internal waterpressureThe pipes are flexible to some extent and they can therefore laid oncurvesTransportation is easy because of light weight.DISADVANTAGESMaintenance cost is highThe pipes are likely to be rusted by acidic or alkaline waterThe pipes require more time for repairs during breakdown and hencenot suitable for distribution pipesThe pipes may deform in shape under combined action of externalforces




8.1 DIFFERENT TYPES OF PIPES5. CONCRETE PIPESA. RCC PIPES

ADVANTAGESThere are pipes are most durable with usual life of about 75yearsThe pipes can cast at site work and thus there is reduction in

transport chargesMaintenance cost is lessInside surface of pipe can made smoothNo danger of rusting.DISADVANTAGESTransportation is difficultRepair work is difficultInitial cost is highThese pipes are affected by acids, alkalies and salty waters.




8.1 DIFFERENT TYPES OF PIPESB. PRESTRESSED CONCRETE PIPES

ADVANTAGESThe inside surface of pipes can be made smoothMaintenance cost is lowThe pipes are durable with life period 75 years

No danger of rustingThese pipes do not collapse or fail under normal trafficDISADVANTAGESThe pipes are heavy and difficult to transport

Repairs of these pipes are difficultThe pipes are likely to crack during transport andhandling operationsThere pipes are affected by acids, alkalies and salty




8.1 DIFFERENT TYPES OF PIPES6. AC PIPES

ADVANTAGESThe inside surface of pipes are very smoothThe joining of pipe is very good and flexibleThe pipes are anticorrosive and cheap in cost

Light in weight and transport is easyThe pipes are suitable for distribution pipes of smallsize.DISADVANTAGESThe pipes are brittle and therefore handling is difficultThe pipes are not durableThe pipes cannot be laid in exposed placesThe pipes can be used only for very low pressures




8.1 DIFFERENT TYPES OF PIPES7. PVC PIPES

ADVANTAGESPipes are cheap

The pipes are durableThe pipes are flexibleThe pipes are free from corrosionThe pipes are good electric insulatorsThe pipes are light in weight and it can easy to mould anyShapeDISADVANTAGES

The coefficient of expansion for plastic is highIt is difficult to obtain the plastic pipes of uniform compositionThe pipes are less resistance to heatSome types of plastic impart taste to the water.




8.2 LAYING OF PIPES1. Detail map of all roads and proposed pipe lines with size

and length are prepared, in which existing pipe line andother structures are shown

2. Marking of centre line of pipe line on the ground bystakes at 30m interval in straight line and 7-15m intervalon curves. The location of pipe line can be marked on

nearby structures3. Excavation of trench 30-40cm extra width than dia. ofpipe. Min. depth of pipe top is 90cm and at joint 15-20cm more excavation for fitting and joining work

4. Bracing and Formworks for high depth excavation5. Pipe are laid in trench and joined with manually or with

help machines, if heavy6. Testing of pipes for leakage7. Backfilling and disposal of surplus soils




8.2 LAYING OF PIPES




8.3 PIPE JOINTS AND TYPES1) Spigot and socket joint•

Also known as ball and spigot joint• Mostly used in cast iron pipe• Spigot or normal end of one pipe inserted into

the socket or ball end of other pipe• Yarn of hemp is wrapped around the spigot pipeend and tightened• Gasket or joint runner is clamped around outer

edge of the bell• Hot lead is poured through V-shaped opening• When the lead is cooled, runner is removed and

is tightened by chalking tools




8.3 PIPE JOINTS AND TYPES2) Expansion joint•

Use to allow the pipe expand and contractduring temp. change• Socket end is flanged and attached with cast iron

follower ring which can freely slide on spigotend

• Rubber gasket is placed between socket baseand spigot end by means of bolts

•

Some space is left between socket base andspigot end for free movement during tempvariation

• Rubber gasket makes the joint water tight6/25/2013 Chapter-7/Water Supply Engineering 17



8.3 PIPE JOINTS AND TYPES3) Flanged joint• Mostly used for temporary pipe lines• Both pipe end has flanged ends• Between two flanged ends washer or rubber

ring/gaskets is placed forsecuring perfect watertight joint

• To join pipes, they arebrought in level position




8.3 PIPE JOINTS AND TYPES4) Mechanical joint• Used when both pipe ends are plain or spigot• Consists of one middle ring, two follower ring

and two rubber gaskets• Two follower rings are connected together by

bolts and when they are tightened, theypress both the gaskets tightly below the ends

of middle ring and joint became tight• Joints are strong and rigid, and can withstand

vibration and shocks upto certain limit6/25/2013 Chapter-7/Water Supply Engineering 21



4) Mechanical joint




8.3 PIPE JOINTS AND TYPES5) Screwed (socket) joint• Common joint for connecting small dia. CI,

WI and GI pipes• End of pipes are threaded outside and socket

is threaded inside• Socket is screwed on both ends of the pipe to

join them• To make water tight jute is placed in the

threads




5) Screwed (socket) joint




8.3 PIPE JOINTS AND TYPES6) Collar joint• Used to join concrete pipes and AC pipes• Two pipes ends are brought in level• Rubber gasket or jute soaked in cement is

kept in grove and then collar is placed at the joint

• 1:1 cement mortar is filled in space betweencollar and pipes




8.3 PIPE JOINTS AND TYPES7) Flexible joint• Bell and socket or universal joint• Used where settlement is likely to occur after

pipe laying• Can also used in curve• Socket end is spherical shape and spigot end

is plain but has bead at end




8.3 PIPE JOINTS AND TYPES8) AC pipe joint• Used for smaller dia. AC pipes• Two ends are butted against each other, then

two rubber rings are

slipped over the pipesand the coupling will bepushed over the rubberrings


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