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PUMP HYDRAULICS BASIC TERMS.

HYDRAULICS:-

It is the study of fluids at rest or in motion.

Fluids include oth li!uid and "ases.

D#$SI%Y:-

%he &ei"ht 'er unit (olume of a sustance.

Sometimes referred to as s'ecific &ei"ht.

S)#CIFIC *RA+I%Y:-

%he ratio of the &ei"ht of a "i(en (olume of the sustance to that of an e!ual (olume of

&ater at a standard tem'erature and 'ressure. ,r the ratio of a li!uids density to that of&ater.

ater has s'ecific "ra(ity of /.0

A centrifu"al 'um' &ill al&ays de(elo' the same head in feet re"ard less of a li!uids

s'ecific "ra(ity.

)ressure &ill increase or decrease in direct 'ro'ortion to a li!uids s'ecific "ra(ity.

1ra2e H) re!uired &ill (ary directly &ith a li!uids s'ecific "ra(ity.

+ISC,CI%Y:-

+iscosity is fluid 'ro'erty that is inde'endent of s'ecific "ra(ity3 it is the internal friction of

fluid.

%he instrument used to measure the (iscosity is (iscometer.

)R#SSUR#:-

)ressure is the force e4erted 'er unit area. If the 'ressure is a''lied to the surface of a

li!uid5 the 'ressure is transmitted undiminished in all directions. )ressure is e4'ressed in'ounds 'er S! .in or 2ilo"rams 'er s!uare centimeter.

A%,6S)#RIC )R#SSUR#:-

%he force e4erted on a unit area y &ei"ht of the atmos'here.

Atmos'heric 'ressure at sea le(el is /7.8 )si or / ar.

*AU*# )R#SSUR#

%he difference et&een 'ressure and that of the atmos'here.

A1S,LU%# )R#SSUR#:-

%he sum of "au"e 'ressure and atmos'heric 'ressure. *au"e 9Atmos'hericAsolute.

. +ACCU6

Used to e4'ress 'ressure elo& atmos'heric.

Fre!uently e4'ressed in inches of 6ercury.

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)U6) )R#SSUR#S:

SUC%I,$ )R#SSUR#

%he actual 'ressure5 'ositi(e or ne"ati(e at the 'um' suction connection as measured on

"au"e.

$#*A%I+# SUC%I,$- If the suction line is elo& the im'eller eye ;datum line< then it is ne"ati(e suction.

),SI%I+# SUC%I,$:-

If the suction line is ao(e the im'eller eye ;datum line< then it is )ositi(e suction.

DIFF#R$%IAL )R#SSUR#.

Differential Dischar"e =Suction.

DISCHRA*# )R#SSUR#

%he actual 'ressure at the 'um' dischar"e connections as measured on

"au"e.

It is e!ual to 'um' suction 'ressure 'lus differential 'ressure de(elo'ed

y the 'um'.H#AD

Head is term for e4'ressin" 'ressure.

Commonly used to re'resent the (ertical hei"ht in feet or meters of static

column.

Also considered as the amount of &or2 necessary to mo(e the li!uid from

its ori"inal 'osition to the re!uired deli(ery 'osition.

S%UFFI$* 1,> )R#SSUR#:-

%he 'ressure actin" in the stuffin" o4 &hich must e sealed.

It is a function of 'um' im'eller desi"n and 'resence or condition of &ear

rin"s.

+A),UR )R#SSUR#

%he 'ressure at &hich a li!uid &ill flash in to a (a'or cur(e &here the

(a'or 'ressure is 'lotted +?S tem'erature.

A li!uid at its (a'or 'ressure affects 'um' 'erformance.

Lo& $)SH at a 'um's suction can cause the li!uid to flash in to a (a'or.

A tem'erature increase of the li!uid can cause it to flash or (a'ori@e.

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Flashin" li!uid in the suction of a 'um' creates ca(itations.

$#% ),SI%I+# SUC%I,$ H#AD ;$)SHseful in freezing climates. /////////////

5. 7ate valve Pressure drop is low' this valve

weighs and costs less than othercompara"le size valves.

%t is almost completely incapa"le

of throttling.

6. )am valve?

Displacement

valve

%t is very useful for ta$ing accurate

samples of solid "earing streams.

These valves are custom

designed to some exact# correct

valve should "e chosen for each

application.

*. Non ( return #al#es

T$pes A%#anta!es &isa%#anta!es

0. Split disc/chec$ valve

%t is generally the least expensivechec$ valve in medium to large sizes.

Shutoff is somewhat "etter in this

valve.

%t is not suita"le for largematerial.

1. ,ift/chec$

valve

%n small sizes# it is also one of the

cheapest chec$ valve. %n large sizes#

it can "e used in pulsating flows.

The pressure drop is fairly high.

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3. Swing/chec$

valve

%t will operate well whether installed

horizontally or vertically. The "ody

can "e equipped with drain or "ypass

taps.

%t is large 4 heavy compared

with other types of such valves.

This valve is not suita"le for

pulsating flows containing

entrained material.

5. Tilting/disc/

chec$ valve

The pressure drop is lower than that

of the swing/chec$ valve.

%T is large 4 heavier than the

swing/chec$ valve. *n over/sized valve is prone to flutter or

slamming.

USEFUL PUMP &ATA

E))ect o) Small Can!e o) Pump Spee%

0. The capacity varies directly as the speed.

1. The head varies as the square of the speed.

3. The "rea$ horsepower varies as cu"e of the speed.

E))ect o) Small Can!e o) Impeller &iameter

0. The capacity varies directly as the diameter.

1. The head varies as the square of the diameter.

3. The "rea$ hoarse power varies as the cu"e of the diameter.

E))ect o) Speci)ic Gra#it$

2rea$ hoarse power varies directly with specific gravity. %f the liquid has

a specific gravity other than water 0.=! multiply the "rea$ HP for water

"y the specific gravity of liquid to "e handled.

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* centrifugal pump will always develop the same head in feet no matter

what the specific gravity of the liquid pumped. However# the pressure

%n pounds per square inch! will "e increased or decreased in direct

proportion to the specific gravity.

E))ect o) "iscosit$

@iscous liquid tend to reduce capacity pump capacity# head and

efficiency and to increase pump "rea$ hourse power and increase pipeline friction. onsult manufacturers for recommendation when pumping

viscous liquids.

E))ect o) Altitu%e

Suction lift data are "ased on values at sea level. Therefore# a"ove sea

level the total suction lift must "e reduced.

E))ect o) +ot Li,ui%s

Hot liquid vaporize at higher a"solute pressures than cold liquids#

therefore the suction lift must "e reduced when handling hot liquids with

a high vapor pressure or a high temperatures the liquid must flow to the

pump suction under pressure. Selection o) pumpin! Unit

%n order to select appropriate pump the following data is essential.

0. apacity required in term of L.P.+.orG.P.+.

1. Discharge head# i.e. highest level up to which water is to "e

supplied -friction loss# if any.

3. Suction lift# i.e. lowest water level from which water is to "e

drawn.

%f the source of supply is a well# following information should "e

availa"leA

5. Diameter in case of tu"e well!

6. Standing water level.

8. ,owest water level while pumping and in summer. %t is also

desira"le to ascertain the yield of the well to ensure that pump

capacity matches with the yield.

Some use)ul %ata on selection o) Pump (

0. %n cites# every individual person consumes app. 06= to 1== lit per/day. %n village# it may "e assumed to "e 5= to 8= lit per persons

per day.

Bther data of consumption of water.

Animal Consumption

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Horse 6= liters per day

Cil$ ow 05= liters per day

Sheep 0= liters per day

Poultry Per 0==! 1= liters per day

1. Height of an average story can "e assumed to "e 0=& to 01&.

3. To find the capacity in gallons! of an overhead tan$. Cultiply the

length "y the width "y depth in feet. This will give the volume in

cu"ic feet. Cultiply this volume "y 9.6 to get capacity in >.S.

gallons.

Formulas an% Con#ersions Factors

Pipe velocity ft. per second!

5= x 7.P.C. 310 x 7.P.C.

EEEEEEEEEEEEEEEE EEEEEEEEEEEEEEE

pipe diameter!1 pipe area

Pipe velocity ft. per second!1

@elocity head feet! EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE

85.5

7.P.C. x head in ft. x specific gravity

Fater horsepower EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE

3G8=

7.P.C. x head in ft. x specific gravity

2rea$ horsepower Pump! EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE

3G8= x pump efficiency

-fficiency pump!

7.P.C. x head in ft. x specific gravity F.H.P.

EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE EEEEEEEEEEE

3G8= x 2.H.P. 2.H.P.

PUMPING TERMINOLOG/

A

ACCELERATOR ( Apump inserted in a closed system to increase the rate of

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flow.

AFFINIT/ LA0S ( The laws governing the performance of rotodynamic

pumps of the same design "ut of different sizes. They ena"le the performance

of full/size pumps to "e accurately forecast from tests on models. They are

q?nd3 ?ND3

and h?n

1

d

1

H?N

1

D

1

where h and H are the heads

n and N the speeds

q and the quantities

and d and D the rotator diameters of the two pumps in the same system of

units.

AIR C+AMERS OR "ESSEL ( Avertical cham"er with the upper end

closed and lower end connected to the discharge "ranch of a pump. Fhilst it

contains air it tends to dump out pressure surges and pump pulsations.

ARC+IME&EAN SCRE0 ( An inclined helical screw rotating in a trough or

the raising liquid from one level to another. Bne of the oldest types of pump

and still used for land drainage.

B

ALANCE &ISC ( Adisc fitted to one end of the shaft of a single or multi/

stage centrifugal pump which is acted on "y pressure to counteract the axial

forces in the impellers.

ALANCE PIPE ( The pipe ta$ing the liquid lea$ing past the "alance disc to

the pump inlet.

ALANCE SUCTION ( An arrangement where"y the axial forces on the

impeller of a centrifugal pump are "alance "y ma$ing it symmetrical and

having two suction "ranches.

ARREL ( The cylindrical tu"e which envelops the ram of a plunger pump.

ERNOULLI2S E3UATION ( States that/

@1?1g P?p I constant

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where @ liquid velocity

p density P Pressure I height a"ove datum

ELL MOUT+ ( An enlarged end to a suction pipe which ensure that the

entering liquid accelerates gradually to the pipe velocity# so reducing friction

losses.

UC4ET ( The pumping element or piston pac$ing of some types of plunger

pumps# especially those intended for large volumes at low heads.

C

CA"ITATION ( The information of "u""les of air# steam or vapor due to the

pressure falling too low# especially at the inlet of the pump. The pressure at

which cavitations occurs depends on the liquid and its temperature. %f not

chec$ed it can cause severe shoc$ and erosion or even "rea$ down. %t can "e

prevented or cured reducing the suction lift.

C+ARACTERISTIC CUR"ES ( Performance curves of rotodynamic pumps

on which effective head# discharge and efficiency are plotted for a num"er of

speeds. They are issued "y pump ma$ers and are useful when choosing a pump

for a particular application.

CLOSE& "ALUE OR S+UT(OFF PRESSURE ( The pressure or head

produced "y a centrifugal pump at zero delivery when the power consumption

is at a minimum. This does not apply to positive displacement or screw

propeller pumps.

COUPLING5+/&RAULIC OR FLUI& ( Acoupling for interposing "etween

a prime mover and pump# consisting of an impeller driven "y a prime/mover

and a rotating casting party filled with oil# which drives the pump. * fluid

coupling allow an electric motor to "e started up under no load# damps out

speed fluctuatuations and if of the scoop type# ena"les the pump speed to "e

varied to meet the requirements.

D

&ESIGN POINT ( The condition for which a pump is expressly designed and

usually those at which it will "e most efficient.

&ISPLACEMENT ( The quantity of liquid pumped for each revolution of a

positive displacement pump.

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&OULE ACTING ( Areciprocatin pump with which delivers liquid on "oth

directions of its stro$e.

&UPLE6 ( Areciprocating pump with two pistons and cylinders in line on the

same axis.

E

EFFICIENC/ ( The ratio of the effective wor$ done "y a pump to the power

supplied to it. %t does not include losses in the lines.

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GAS4ET ( Usually understood to mean a sheet of material# often with several

holes# which is placed "etween two relatively fixed metal (oint faces to prevent

lea$age.

GLAN& ( Adevice for sealing a cylindrical part where it passes through the

wall of a pressure vessel. 7lands can "e arranged to seal a fixed part or a

moving part such as piston or rotating shaft. Typical examples of the letter are

stuffing "oxes 4 face seals.

H

+EA& ( The vertical distance "etween a pump and its suction or discharge

points' the pressure equivalent to the height of a column of liquid.

+EA&5 &ELI"ER/ ( The pressure at the pump outlet measured in feet of

water.

+EA&5 SUCTION ( The head at the pump inlet measured in feet of water. %f

the suction pipe is "elow the pump the head may "e negative.

+EA&5 MANOMETRIC ( Ahead as indicated "y a pressure gauge# usually

expressed in terms of the height of a liquid column# e.g. feet of water.

I

IMPELLER ( Asteam operated (et instrument which uses the latent heat oft

the steam to produce $inetic energy. The steam (et produces a vacuum whichdraws in water with which it mixes and the energy in the steam is then a"le to

produce a pressure higher than the original steam pressure. %t is chiefly used for

filling low pressure "oilers# using steam from the "oiler itself.

L

LEA4(OFF ( 0hen a high pressure tur"ine pump operates under closed valve

conditions# the heat produced "y churning is considera"le. * lea$ off value is

opened thermostatically under these conditions to ensure sufficient circulation

through the pump.

LI3UI& ( Anything which can "e pumped.

LI3UI&("OLATILE ( Aliquid which vaporized at a relatively low

temperature and which may# therefore# cause trou"le through cavitations unless

care is ta$en.

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P

PAC4ING ( Any soft material used for preventing lea$age "etween the metal

parts of a pump.

PAC4ING LESS ( Aterm usually applied to electrically driven pumps where

the pump and motor rotor are in one casing.

PRESSURE ( The force exerted "y a fluid when compressed or "y a columns

of liquid. %t is measured as weight per unit area# e.g. pounds per sq. in psi! or

"y feet of columns of liquid it will support e.g. feet of water equals =.533 psi.

PRESSURE5 ASOLUTE ( Pressure measured from an a"solute vacuumed as

datum# *tmospheric pressure is 05.9 psi a"solute when the "arometer is 3= in.

mercury. Phenomena such as cavitation and vapor pressure depend on the

a"solute pressure of the liquid.

PRESSURE5 GUAGE ( The pressure as shown "y an ordinary pressure gaugewhich uses the prevailing atmospheric pressure as a datum.

PRESSURE5"APOUR ( The pressure exerted "y a liquid in a partially filled

closed vessel which contains nothing "ut the liquid and its vapour. @apour

pressure varies with temperature and for water is A/

=.16 psi a"solute at 8=