module 8 - pumps for water supply 1(revised)

7/22/2019 Module 8 - Pumps for Water Supply 1(Revised)

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Danilo V. Ravina NAMPAP - CEBU 1

MODULE 8

PUMPS FOR WATER SUPPLY

PLUMBING FUNDAMENTALS


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What is a Pump?

Pump is an equipment used to transfer fluid from a

region of low pressure to another region at same or

higher pressure. (PSME Code 1993)

Pump A device or machine that compresses and/or

transports fluids usually by pressure or suction, or both;

may be used to remove water from a construction site orto convey water from one elevation to another. (Harris,

C.M.; Dictionary of Architecture and Construction, 1975)

In about 120 BC someone, probably the Greek mathematician Ctesibius,

invented the first force pump. It had 2 cylinders with single acting pistons,

connected to a single beam so that they delivered an almost continuousstream of water.


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DESIGN OF PUMPS

Data needed to purchase

pumps:

1. Pump Discharge (Q)

2. Total Dynamic Head (TDH)

Pump Discharge or Capacity

of Pump:1. If the pump is used directly to

supply water, the capacity

must be equal to the

maximum hour demand.

2. If the water distributionsystem has a reservoir, the

pump capacity must be equal

to the maximum day demand

Pump Selection:

1. In the absence of electric power

and in cases of isolated small

population, hand pumps are

recommended because of higher

capital, maintenance and

operating costs of diesel or

gasoline engine driven pumps.

2. If the well water depth is 6 meters

or less, use centrifugal pumps(maximum suction lift = 6.00 m).

3. If the well water depth is 6 to 20

meters, usejet pumps.

4. If the well water depth is more

than 20.00 meters, use

submersible pumps orvertical

line shaft turbine pumps.

Pump operating Time = at Least

at least 8 12 hoursDanilo V. Ravina NAMPAP - CEBU 3


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What are the different classifications

of pumps?

The different classifications of pumps are categorized as

follows:

1. As to Operating Principle

2. As to Casing Design3. As to Mounting

4. As to Connection with Driver

(Motor or Engine)

5. As to Construction Materials


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Classification of Pumps as to

Operating Principle:

1. Centrifugal Type

a. Radial Flow

b. Axial Flow

c. Mixed Flow

2. Positive Displacement

Type

a. Reciprocating Piston

b. Reciprocating Plunger

c. Rotary Bladesd. Rotary Roots

e. Screw Types

f. Gear

3. Turbine Type

a. Axial Flow

b. Mixed Flow


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Classification of Pumps as

to Casing Design:

1. Horizontal Split Case

2. Vertical Split Case3. Submerged

Classification of Pumps as

to Mounting:

1. Base Mounted

2. In line Mounted

Horizontal Split Case

Vertical Split Case

Submerged

Base Mounted

In line Mounted


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Classification of Pumps as toConnection with Driver:

1. Flexible Coupled

2. Case Coupled

3. Belt Driven

Classification of Pump as to

Construction Materials:

1. Cast Iron

2. Stainless Steel

3. Bronze

4. Concrete

5. Plastic

6. Fiberglass

Case Coupled

MOTORIMPELLER

PUMP

Belt Driven


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What are the Classifications of Pumps?


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Pumps are generally referred to according to their

principle of action, manner of construction or

method of operation.

Centrifugal Pump(Built by Osborne Reynolds, 1875) A vane orimpeller rotate inside a close-fitting case, draw in liquid at the center and,

by virtue of centrifugal force, throw liquid out through an opening in the

periphery of the case.

1. The higher the speed of rotation, the greater the volume that can bepumped or the greater the head that can be generated.

2. The recommended suction lift is 4.5 meters and should not exceed 6

meters. Therefore, if the well water depth is 6 meters or less, use

centrifugal pump

3. A centrifugal pump cannot operate unless the pump casing is full of

water. For the pump to begin developing a suction at the eye of thepump, the case will have to be filled with water or primed.

4. Care must be taken to ensure that air is not present in the casing and

whenever possible the suction should be of the positive or flooded type.


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Centrifugal Pump:


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What is a Submersible Pump?

Submersible

Pumpis basically acentrifugal pump

complete with electricmotors which are

positioned underwater

in a suitable bored

hole that delivers the

water to the surface.


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What are the important considerations for

accurate Submersible Pump selection?

Well Diameter indicates the size ofthe pump to be installed.

Well Depth indicates the Static WaterLevel, the vertical distance from the surface(Datum Line) to the water level when nowater is being pump.

Pumping Water Level the verticaldistance from the Datum Line to the waterlevel when specified capacity is beingpumped. During the pumping test, PumpingWater Levelis the depth of water when theamount of water withdrawn from the well &the amount of replenishment of water to thewell is equal.

Drawdown the vertical distance or the

difference between the Pumping WaterLeveland the Static Water Level.

Head above Datum indicates theTotal Discharge Head(Static plus Friction)between Datum line & point ofmeasurement.

Pump Capacity volume rate of flowexpressed in cubic meters perhourorliters

per secondto be produced by the pump.

Pump Setting the nominal verticaldistance (in meters) from Datum to thedischarge pipe connection at the pump.

Water Composition make-up of thewater to be pumped.

Type of Drive the specification of theavailable power source (single phase or 3phase)

Allowable Motor Overloadpercentage of rated motor main plate power(in kilowatts or horsepower) that will bepermitted to be used.


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WellDe

pth

Discharge Pipe

Well Diameter

PumpSetting

Drawdown

Submersible Pump

Submersible Pump:


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Positive Displacement Pumps:

Reciprocating and Rotary

Reciprocating PumpA pump which operates with a to and fromotion. The different types of Reciprocating Pump are:

1. Lift Pump The simplest of the reciprocating pump and consists of apiston moving up and down in a cylinder or barrel.

A Lift Pump cannot be used to raise water above 7.50 to 8.50 meter atnormal atmospheric pressure (101 kPa) due to:

a. Loss of efficiency in the pump

b. Friction in the intake pipe

c. Impossible to obtain a perfect vacuum

2. Piston or Plunger Pump A plunger is driven backwards &forwards, or up & down by a mechanical working head.

3. Deep well Piston Pump When water is more than 7.50 metersbelow the ground, it is virtually necessary to place the pump in or near thewater in the well and pump from there. Water is forced up the drop pipeand out into the delivery pipe.


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A LIFT PUMP / HAND PUMP

START OF UPSTROKE

FOLLOWING

DOWNSTROKE

NEXT UPSTROKE


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The Working Cycle of a Piston Pump


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A Deep Well Piston Pump


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What is a Diaphragm Pump?

A Diaphragm Pump is a displacement pump in which a flexible diaphragm

replaces the piston in other displacement pumps. The diaphragm is of

leather or heavy gauge rubber. The upward movement of the diaphragm

has the same effect as the upward movement of the piston; the outlet valve

closes & the inlet valve opens & admits water. The downward movement of

the diaphragm causes the inlet valve to close & water is forced into thedischarge pipe.


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What is a Rotary Pump?

A Rotary Pump is used primarily as a source of fluid power in hydraulicsystem. It continuously scoops the liquid from the pump chamber.

It is classified with respect to the impelling element as:

1. Gear Type

2. Vane Type3. Piston Type


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What is a Jet Pump?

A Jet Pump is a pumpconsisting revolving impeller in the

pump housing which forces water

down a pressure line to an ejector

assembly below water level. This

ejector consists of a nozzle whichdischarges the water into a

constricted throat. This throat

leads from a suction pipe. This

arrangement permits energy of a

high pressure fluid to be converted

into a high velocity fluid.


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What is a Hydraulic Ram or Ram

Pump?

Hydraulic Ram uses the energyof falling water to raise a smaller

quantity of water to greater

heights. It is a pump in which the

power generated from flowing in

an enclosed pipe is used to raisepart of the water to a height above

that from which the flow began.


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What is the Pump Performance

Curve?

The characteristic curve of apump describes the factorsthat affect its performance.They are usually expressedgraphically with the rate ofdischarge (Q) as abscissa &other factors plotted asordinates, such as the Head(H), & the Net PositiveSuction Head (NPSH). Allpump manufacturers supplyperformance characteristic

curves for their pumps whichindicate how the pumpcapacity varies withdischarge pressure orsuction pressure.

Sample of Pump Performance Curve

Source: IBARRA

PUMPS


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Source: GRUNDFOS


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Duty Point & Pump Efficiency

Source: GRUNDFOS


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NET POSITIVE SUCTION HEAD (NPSH)

Low pressure at the suction

side of a pump can

encounter the fluid to startboiling with

reduced efficiency

cavitation

damage

of the pump as a result.

Boiling starts when the

pressure in the liquid is

reduced to the vapor

pressure of the fluid at theactual temperature.

To characterize the potential for boiling and cavitation, the difference

between the total head on the suction side of the pump (close to the

impeller) and the liquid vapor pressure at the actual temperature,

can be used


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Available NPSH (NPSHa)The Net Positive Suction Head made available the suction system for the

pump is often named NPSHa The NPSHa can be determined during design

and construction, or determined experimentally from the actual physical

system.NPSHa : The Pump is Above the TankIf the pump is positioned above the tank, the elevation (he) is

positive and the NPSHa decreases when the elevation of the

pump increases.

At some level the NPSHa will be reduced to zero and the fluid

starts to evaporate.

NPSHa: The pump is Below the TankIf the pump is positioned below the tank, the

elevation (he) is negative and the NPSHa

increases when the elevation of the tank

decreases (lowering the pump).

Ii is always possible to increase NPSHa by

lowering the pump (as long as the major and

minor head loss due to longer pipe do notincrease it more. This is important and it is

common to lower the pump when the pumping

fluids close to evaporation temperature.


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Required NPSH (NPSHr)

The NPSHr as the Net Positive Suction Head as required by the pump

in order to prevent cavitation for safe and reliable operation of the

pump.

The required NPSHr for a particular pump is in general determined

experimentally by the pump manufacturerand a part of the

documentation of the pump.

H d l t th t f t b


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How do we select the type of pump to be

used?PUMP

CAPACITYDEPTH OF WELL

0 to 8.00 m 8.00 to18.00 m

18.00 to27.00 m

27.00 to46.00 m

46.00 m andover

1,200 to

2,400 LPH(300 600 GPH)

Submersible

Pump

Jet Pump

Piston Pump

Submersible

Pump

Jet Pump

Deep Well

Reciprocating

Pump

Submersible

Pump

Jet Pump

Deep Well

Reciprocating

Pump

Jet Pump

Deep Well

Reciprocating

Pump

Submersible

Pump

Jet Pump

Deep Well

Reciprocating

Pump

Submersible

Pump

2,400 to

4,500 LPH(600 1200 GPH)

Submersible

Pump

Jet Pump

Plunger Pump

Submersible

Pump

Jet Pump

Submersible

Pump

Jet Pump

Submersible

Pump

Jet Pump

Submersible

Pump

Jet Pump

Over 4,500

LPH(over 1200 GPH)

Submersible

Pump

Jet Pump

Plunger Pump

Submersible

Pump

Jet Pump

Submersible

Pump

Jet Pump

Submersible

Pump

Submersible

Pump

Pump Selection Rule of Thumb: 1. If the well water depth is 6 meters or less, use Centrifugal Pump.

2. If the well water depth is 6 to 20 meters, use Jet Pump.

3. If the well water depth is more than 20 meters, use Submersible Pump or

Vertical In-Line Shaft Turbine Pumps.


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END OF PRESENTATION

module 8 - pumps for water supply 1(revised)

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