visual pump glossary.pdf

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PUMP AND PUMP SYSTEM GLOSSARY

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Absolute pressure: pressure is measured in psi (pounds per square inch) in the imperial system and ka (kiloascal or

bar) in the metric system. !ost pressure measurements are made relati"e to the local atmospheric pressure. #n that case

we add a $%$ to the pressure measurement unit such as psi% or ka%. &he "alue of the local atmospheric pressure "aries

with ele"ation (see this pressure "s. ele"ation chart on this pa%e). #t is not the same if you are at sea le"el (. psia) or at

*** feet ele"ation (+. psia). #n certain cases it is necessary to measure pressure "alues that are less then the local

atmospheric pressure and in those cases we use the absolute unit of pressure, the psia or ka a.

pa(psia) pr(psi%) - patm(psia), patm . psia at sea le"el.

where pais the absolute pressure, prthe relati"e pressure and patmthe absolute pressure "alue of the local atmospheric

pressure.

and in the metric system

pa(ka a) pr(ka%) - patm(ka a), patm ** ka a at sea le"el.

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2/62

Accumulator: used in domestic water applications to stabilie the pressure in the system and a"oid the pump cyclin% on and off e"ery time a tap is opened

somewhere in the house. &he fle/ible bladder is pressuried with air at the pressure desired for achei"in% the correct flow rate at the furthest point of the house or

system. 0s water is pulled from the tank the bladder e/pands to fill the "olume and maintain the pressure. When the bladder can no lon%er e/pand the water

pressure drops, the pressure switch of the pump is acti"ated on low pressure, and the pump starts and fills the water "olume of the accumulator. &he bladder keepsthe air from enterin% into solution with the water resultin% in less frequent re1pressurisation of the accumulator.

umps are often sold as a packa%e with an accumulator.

Affinity las: the affinity laws are used to predict the chan%e in diameter required to increase the flow or total head of a pump. &hey can also predict the chan%e in

speed required to achie"e a different flow and total head. &he affinity laws can only be applied in circumstances where the system has a hi%h friction head compared

to the static head and this is because the affinity laws can only be applied between performance points that are at the same efficiency. see affinity laws.pdf

&he followin% fi%ure shows a system that has a friction head (cur"e 0) hi%her than its static head for which the affinity laws apply, as compared to cur"e 2, a system

with a hi%h static head as compared to the friction head where the affinity laws do not apply.


3/62

3omain of application of the affinity laws for an a/ial flow pump.

&he affinity laws are e/pressed by the three followin% relationships where 4 is the flow rate, n the pump rpm, 5 the total head and the power. 6ou can predict the

operatin% condition for point + based on the knowled%e of the conditions at point and "ice "ersa.

&he process of arri"in% at the affinity laws assumes that the two operatin% points that are bein% compared are at the same efficiency. &he relationship between two

operatin% points, say and +, depends on the shape of the system cur"e (see ne/t Fi%ure). &he points that lie on system cur"e 0 will all be appro/imately at the same

efficiency. Whereas the points that lie on system cur"e 2 are not. &he affinity laws do not apply to points that belon% to system cur"e 2. 7ystem cur"e 2 describes a

system with a relati"ely hi%h static head "s. system cur"e 0 which has a low static head.


4/62

Diameter re!uction&o reduce costs pump casin%s are desi%ned to accommodate se"eral different impellers. 0lso, a "ariety of operatin% requirements can be met

by chan%in% the outside diameter of a %i"en radial impeller. 8uler's equation shows that the head should be proportional to (n3)+pro"ided that the e/it "elocity

trian%les remain the same before and after cuttin%. &his is the usual assumption and leads to:

which apply only to a %i"en impeller with altered 3 and constant efficiency but not a %eometrically similar series of impellers.#f that is the case then the affinity laws can

be used to predict the performance of the pump at different diameters for the same speed or different speed for the same diameter. 7ince in practice impellers of

different diameters are not %eometrically identical, the author's of the section called erformance arameters in the ump 5andbook recommend to limit the use of

this technique to a chan%e of impeller diameter no %reater than * to +*9. #n order to a"oid o"er cuttin% the impeller, it is recommended that the trimmin% be done in

steps with careful measurement of the results. 0t each step compare your predicted performance with the measured one and adust as necessary.

&ry this affinity law calculator.

Air entrainment "in#estion$: air in the pump suction can reduce the performance of a pump considerably. &he followin% chart from ;oulds shows that e"en +9 air

by "olume in the liquid can ha"e an effect on performance.

erformance reduction due to air in the pump

&here are many causes of air entrainment, the air may be comin% in at the suction tank due to improper pipin%

or due to leaka%e iin the pump suction line (assumin% that conditions are such that low pressure is produced in the suction line).


5/62

iscous dra% pumpscan handle lar%e quantities of air.

ALLO%A&LE P'PE STRESS: the allowable or ma/imum pipe stress can be calculated usin% the 07!8 ower ipin% =ode 2??.. &he allowable pipe stress is

fi/ed by the code for a %i"en material, construction and temperature from which one can calculate the allowable or ma/imum pressure permitted by code. 7ee this

applet's 5elp Filefor more info.

ANS': 0merican @ational 7tandards #nstitute. 0 term often used in connection with the classification of flan%es, 0@7# class A*, ?**, etc. 7ee this e/cerpt of the

07!8 2B.A code for the pressure ratin% of 0@7# class flan%es.

ANS' &()*+: this is a standard that applies to the construction of end1suction pumps. #t is the intent of this standard that pumps of all sources of supply shall be

dimensionnally interchan%eable with respect to mountin% dimensions, sie and location of suction and dischar%e noles, input shafts, baseplates, and foundation bolts.

&his ne/t ima%e shows the dimensions that ha"e been standardied (source: the ump 5andbook by !c;raw15ill)

&his ne/t ima%e shows a cross1section of an end1suction pump built to the 2?.standard (source: the ump 5andbook by !c;raw15ill).


6/62

&his web pa%e from the !c@ally #nstitute%i"es comments on the scope of pump standards and recommends "arious chan%es to apply to pumps prior to orderin%

and modifications that will increase the operatin% life after receipt of a pump.

Anti ,orte- Plate: 0n anti "orte/ plate pre"ents the formation of a "orte/ and and therefore air entrainment into the pump by forcin% any emer%in% "orte/ to %o

around a plate and then into the suction pipe. &he swirlin% motion cannot be maintained and the "orte/ dissipates and cannot form if the path is too lon% and

contorted. Source: NFPA 22, Standard for water tanks for private fire protection 2008 edition . 6ou can find the entire code here.

AP' .+/: 0merican etroleum #ndustry, a pump standard adopted by the petroleum industry. &he intent bein% to make pumps more robust, leak1free and reliable.

ASME: 0merican 7ociety of !echanical 8n%ineers. &he 2oiler pressure power pipin% code 2?.? is a code that is often used in connection with the term 07!8,

the ma/imum pressure safely allowable can be calculated usin% this code.

&ry this calculator to determine the ma/imum allowable pipin% pressure.


7/62

&he help file of this applet shows some e/cerpts of 2?.? 07!8 code.

Atmosp0eric pressure: usually refers to the pressure in the local en"ironment of the pump. 0tmospheric pressure "aries with ele"ation, it is . psia at sea le"el

and decreases with risin% ele"ation. &he "alue of the local atmospheric pressure is required for calculatin% the@750of the pump and a"oidin% ca"itation.

&ake a look at this "ideo of an interestin% e/periment with atmospheric pressure.

&he "ariation of atmospheric pressure with ele"ation.

&he ;oulds pump catalo%ue pro"ides more information on atmospheric pressure "s. ele"ation.

A-ial flo pump: refers to a desi%n of a centrifu%al pump for hi%h flow and low head. &he impeller shape is similar to a propeller. &he "alue of the specific speed

numberwill pro"ide an indication whether an a/ial flow pump desi%n is suitable for your application. see a/ial flow pumps.

&hey are used e/tensi"ely in the state of Florida to control the water le"el in the canals of low lyin% farmin% areas. &he water is pumped o"er low earthen walls called

burms into the 7outh Florida Water !ana%ement 3isctrictmain collectin% canals.

!W# in Floridais a reputable supplier of these pumps.


8/62

&ac1 2anes: see end1suction pump.

&ac1 plate: see end1suction pump.

&arometric pressure: the same as atmospheric pressure, the pressure in the local en"ironment. 2arometric pressure is a term used in meteorolo%y and is often

e/pressed in inches of !ercury.

&aseplate : all pumps require some sort of steel base that holds the pump and motor and is anchored to a concrete base.

see this ;oulds web pa%e for more information, these baseplates are built to the 0@7# standard 2?. and will therefore accomodate any pump built to the same

standard.

&est Efficiency Point "&*E*P*$: &he point on a pump's performance cur"e that corresponds to the hi%hest efficiency. 0t this point, the impeller is subected to

minimum radial force promotin% a smooth operation with low "ibration and noise.


9/62

Fi%ure #mportant points of the pump characteristic cur"e.

Cadial force on the impeller "s. the flow rate (source: the ump 5andbook by !c;rawhill).

When selectin% a centrifu%al pump it is important that the desi%n operatin% point lie within the desirable selection area shown in the ne/t fi%ure.

see articles on best efficiency on this web pa%e:pumpworld.htm

&in#0am plastic: 0 fluid that beha"es in a @ewtonian fashion (i.e. constant "iscosity) but requires a certain le"el of stress to set it in motion.

For more information see non1newtonian fluids.pdf

&our!on pressure #au#e: the 2ourdon tube is a sealed tube that deflects in response to applied pressure and is the most common type of pressure sensin%

mechanism.


10/62


11/62

&o find out more about control systems, this is an e/cellent treatment of the types of control systems for a centrifu%al pump. &hanks to Walter 3ried%er of =olt

8n%ineerin% a consultin% en%ineerin% firm for the petro1chemical industry in 0lberta, =anada.

3alculation softare: doin% pump system calculations and pump selection can be a lon% manual process with opportunities for many errors. 5elp yourself produce

accurate, consistent and error free total head calculation results with #81F


12/62

=a"itation dama%e on an impeller of a Cobot 2WA*** pump (ima%e pro"ided by my pump friend 2art 3ui"elaar).

6ou can oin the pumpfun!amentals centrifu%al pump discussion forum at http:DDwww.pumpfundamentals.comDforum

3entrifu#al force: 0 force associated with a rotatin% body. #n the case of a pump, the rotatin% impeller pushes fluid on the back of the impeller blade, impartin%

circular and radial motion. 0 body that mo"es in a circular path has a centrifu%al force associated with it .

&ry this e/periment, find a plastic cup or other container that you can poke a small pinhole in the bottom. Fill it with water and attach a strin% to it, and now you%uessed it, start spinnin% it.

Fi%ure ? 0n e/periment with centrifu%al force.

&he faster you spin, the more water comes out the small hole, you ha"e pressuried the water contained in the cup usin% centrifu%al force, ust like a pump.

A 3ENTR'4UGAL PUMP AN'MAT'ON


13/62

&his animation shows my interpretation of what happens to fluid particles (represented by %ray balls) once they enter the eye of the impeller and after they turn H*

de%rees. 0t this point they are at the entrance of the "olume formed by two adacent impeller "anes. &he rapid rotation of the "anes (impeller blades) displaces the

fluid particles by mo"in% them in a radial direction where they come into contact with the pump "olute and are decelerated and pressuried. =heck out the direction

of rotation, not what one would e/pect at first %lance.

For those of you who would like to ha"e this ima%e for your presentation here is

an animated %if "ersion.

30aracteristic cur2e: same asperformance cur"e.

30ec1 2al2e: a de"ice for pre"entin% flow in the re"erse direction. &he pump should not be allowed to turn in the re"erse direction as dama%e and spilla%e may

occur. =heck "al"es are not used in certain applications where the fluid contains solids such as pulp suspensions or slurries as the check "al"e tends to am. 0 check

"al"e with a rapid closin% feature is also used as a pre"entati"e for water hammer. see also check "al"e => coefficient.

>arious check "al"es (source: &he =rane &echnical aper no *)

do your own calculation of Fittin% friction loss with this a"a applet

3olebroo1 e5uation: an equation for calculatin% the friction factor f of fluid flow in a pipe for @ewtonian fluidsof any "iscosity. see also the !oody dia%ramfi%ure H.


14/62

&his factor is then used to calculate the friction loss for a strai%ht len%th of pipe. 3o your own calculation of pipe friction loss with this a"a applet

&o understand how to sol"e the =olebrook equation for the friction factor f usin% the @ewton1Caphson iteration technique, dowload this pdf file.

5ere is an interestin% article on alternate e/plicitand "ery precise "ersion of the =olebrook equation.

30opper pump: a pump with a serrated impeller ed%e which can cut lar%e solids and pre"ent clo%%in%.

=hopper pump

see specialtyIpumps.pdf for more information

3lose! or open impeller: the impeller "anes are sandwiched within a shroud which keeps the fluid in contact with the impeller "anes at all times. &his type of

impeller is more efficient than an open type impeller. &he disad"anta%e is that the fluid passa%es are narrower and could %et plu%%ed if the fluid contains impurities or

solids.

#n the case of an open impeller, the impeller "anes are open and the ed%es are not constrained by a shroud. &his type of impeller is less efficient than a closed type

impeller. &he disad"anta%e is mainly the loss of efficiency as compared to the closed type of impeller and the ad"anta%e is the increased clearance a"ailable which will

help any impurities or solids %et throu%h the pump and pre"ent plu%%in%.

also read this article on closed "s. open impellers by John oel, president of the 7ims ump >al"e =ompany re1printed with his permission. 6ou can "iew the

7ims company web site at www.simsite.com

3, coefficient: a coefficient de"eloped by control "al"e manufacturers that pro"ides an indication of how much flow the "al"e can handle for a psi pressure drop.

For e/ample, a control "al"e that has a => of A** will be able to pass A** %pm with a pressure drop of psi. => coefficients are sometimes used for other de"ices

such as check "al"es.


15/62

=> coefficients for a wafer style check "al"e.

3utater6the narrow space between the impeller and the casin% in the dischar%e area of the casin%.

this is the area where pressure pulsations are created, each "ane that crosses the cutwater produces a pulse. &o reduce pulsations in critical process', more "anes are

added.

Darcy7%eisbac0 e5uation: an equation used for calculatin% the friction head loss for fluids in pipes, the friction factor fmust be known and can be calculated by the

=olebrook, the 7wamee1Jain equations or the !oody dia%ram.

Dea! 0ea!: a situation that occurs when the pump's dischar%e is closed either due to a blocka%e in the line or an inad"ertently closed "al"e. 0t this point, the pump

will %o to it's ma/imum shut1off head, the fluid will be recirculated within the pump resultin% in o"erheatin% and possible dama%e.

Diffuser6located in the dischar%e area of the pump, the diffuser is a set of fi/ed "anes often an inte%ral part of the casin% that reduces turbulence by promotin% a

more %radual reduction in "elocity.

&he followin% ima%e comes from this web site http:DDwww.tpub.comDcontentDdoeDh*K"DcssDh*K"IH.htm


16/62

Diap0ra#m pump: a positi"e displacement pump. 3ouble 3iaphra%m pumps offer smooth flow, reliable operation, and the ability to pump a wide "ariety of "iscous,

chemically a%%ressi"e, abrasi"e and impure liquids. &hey are used in many industries such as minin%, petro1chemical, pulp and paper and others.

0n air "al"e directs pressuried air to one of the chambers, this pushes the diaphra%m across the chamber and fluid on the other side of the diaphra%m is forced out.

&he diaphra%m in the opposite chamber is pulled towards the centre by the connectin% rod. &his creates suction of liquid in chamber, when the diaphra%m plate

reaches the centre of the pump it pushes across the ilot >al"e rod di"ertin% a pulse of air to the 0ir >al"e. &his mo"es across and di"erts air to the opposite side of

the pump re"ersin% the operation. #t also opens the air chamber to the e/haust.

this type of diaphra%m pump is dri"en by pneumatic air so these can be used where electric dri"es are not preferred, is self primin% and can run dry for brief periods,

an handle haardous liquids with almost any "iscosity, can pump solids up to certain sies.


17/62

Wilden is a maor manufacturer of such pumps http:DDwww.wildenpump.comD

Dilatant: &he property of a fluid whose "iscosity increases with strain or displacement.

For more information see non1newtoninan fluids.pdf

Disc0ar#e Static 8ea!: &he difference in ele"ation between the liquid le"el of the dischar%e tank if the pipe end is submer%ed and the centerline of the pump. #f the

dischar%e pipe end is open to atmosphere than it is the difference between the pipe end ele"ation and the suction tank fluid surface ele"ation. &his head also includes

any additional pressure head that may be present at the dischar%e tank fluid surface, for e/ample as in a pressuried tank.

Fi%ure 3ischar%e, suction and total static head.

7ee this tutorial for more information on dischar%e static head.

Double suction pump: the liquid is channeled inside the pump casin% to both sides of the impeller. &his pro"ides a "ery stable hydraulic performance because the

hydraulic forces are balanced. &he impeller sits in the middle of the shaft which is supported on each end by a bearin%. 0lso the @..7.5.C. of this type of pump will

be less than an equi"alent end1suction pump. &hey are used in a wide "ariety of industries because of their reliabilty. 0nother important feature is that access to the

impeller shaft and bearin%s is a"ailable by remo"in% the top co"er while all the pipin% can remain in place. &his type of pump typically has a double "olute.

&he followin% ima%e is pro"ided by the Flow 7er"e =orporation.


18/62

&his sketch will help "isualie the flow inside the pump.

Double 2olute pump: a pump where the immediate "olute of the impeller is separated by a partition from the main body of the casin%. &his desi%n reduces the radial

load on the impeller makin% the pump run smoother and "ibration free.


19/62

3ouble "olute pump (source of ima%e the ump 5andbook by !c;raw15ill).

see the pump type databasefor more information

For more information see this pdf file from =ornell umps

Droopin# cur2e: similar to the normal profile e/cept at the low flow end where the head rises then drops as it %ets to the shut1off head point. see centrifu%al1pump1

tips.htm

Efficiency6: the efficiency of a pump can be determined by measurin% the torque at the pump shaft with a torque meter and then calculatin% the efficiency based on

the speed of the pump, the pressure or total head and flow produced by the pump. &he standard equation for torque and speed pro"ides power.

&he power consumed by the pump is proportional to total head, flow, specific %ra"ity and efficiency.

for a metric "ersion of this formula see this pa%e.

Flow and total head are measured and then the efficiency can be determined.

&he efficiency is calculated for "arious flow rates and plotted on the same cur"e as the pump performance or characteristic cur"e. When se"eral performance cur"es

are plotted, the equal efficiency "alues are linked to pro"ide lines of equal efficiency. &his is a useful "isual aide as it points out areas of the "arious pump cur"es that

are at hi%h efficiency, which will be the preferred areas or areas that the selected pump should operate within. &he hi%hest efficiency on a %i"en pump cur"e is known

as the 2.8.. (best efficiency point), more information is a"ailable in this area of the "isual %lossary.

=entrifu%al pumps come in many desi%ns and some are more suitable for low1flow hi%h1head applications and others for hi%h1flow low1head and some in between.

&hey are desi%ned to achie"e their ma/imum efficiency to accommodate a particular application.

&he specific speed number %i"es an indication of what type of pump is more suited to your application. &he effect of specific speed on pump desi%n and how to

calculate this number is a"ailable in this area of the "isual %lossary.


20/62

#t is possible to predict efficiency. 7ome years a%o, a sur"ey of typical industrial pumps was made. &he a"era%e efficiency was plotted a%ainst the specific speed and

it shows what the ultimate efficiency limits are for pumps under "arious operatin% conditions. !ore information is a"ailable on the centrifu%al pump tips pa%e.

7uction specific speed is another parameter that can affect efficiency. &his number is a measure of how much flow can be put throu%h a pump before it starts to

choke (reaches it's upper flow limit) and ca"itates (the pressure at the suction becomes low enou%h that the fluid "apories). !ore information is a"ailable in the "isual

%lossary here.

En! suction pump: a typical centrifu%al pump, the workhorse of industry. 0lso known as "olute pump, standard pump, horiontal suction pump. &he back pull out

desi%n is a standard feature and allows easy remo"al of the impeller and shaft with the complete dri"e and bearin% assembly while keepin% the pipin% and motor in

place.

7ome of its components are:

.=asin%, "olute

+. #mpeller, "anes, "ane tips, backplate, frontplate (shroud), back "anes, pressure

equalisin% passa%es or balancin% holes

?. 2ack co"er parallel to lane of the impeller intake

. 7tuffin% 2o/ 1 ;landDmechanical seal housin% or packin%Dlantern rin%

A. ump shaft

B. ump casin%

. 2earin% housin%

K. 2earin%s

H. 2earin% seals

. 2ack pull out

+. 2earin%s

?. 2earin% seals

2alancin% holes

2ack"anes

GLOSSARY NAVIGATION


21/62

E5ui2alent len#t0: a method used to establish the friction loss of fittin%s (see ne/t fi%ure). &he equi"alent len%th of the fittin% can be found usin% the nomo%raph

below. &he equi"alent len%th is then added to the pipe len%th, and with this new pipe len%th the o"erall pipe friction loss is calculated. &his method is rarely used

today. 7ee tutotial?.htmfor the current method for calculatin% fittin%s friction head loss.

Ener#y #ra!ient: see 5ydraulic %radient.

E-peller: a hydro1dynamic seal that pro"ides a seal without addition of water to the %land, specially useful for liquid slurries.


22/62

(ima%e source: Worthin%ton umpworld article, see below)

see an article on the e/peller seal on this web pa%e:pumpworld.htm

E-ternalGear pump: a positi"e displacement pump. &wo spur %ears are housed in one casin% with close clearance.


23/62


24/62

&able of head loss factors for water from the =ameron 5ydraulic data book.

&ry this calculator for pipin% friction head loss.

For more information on friction head.

4riction factor f "pipe$: the friction factor f is required for the calculation of the friction head loss. #t is %i"en by the !oody dia%ram, or the =olebrook equationor

the 7wamee1Jain equation. &he "alue of the friction factor will depend on whether the fluid flow is laminar or turbulent. &hese flow re%imes can be determined by the

"alue of the Ceynolds number.

4ront co2er: see end1suction pump.

4ront plate: see end1suction pump.

Glan!: see stuffin% bo/.

Glan!les s pumps: see sealless pumps.

8a9en7%illiams e5uation: this equation is now rarely used but has been much used in the past and does yield %ood results althou%h it has many limitations, onebein% that it does not consider "iscosity. #t therefore can only be applied to fluids with a similar "iscosity to water at B*F. #t has been replaced by the 3arcy1

Weisbach and the =olebrook equation. #nterestin%ly the @F0 (@ational Fire rotection 0ssociation) mandates that the 5aen1Williams equation be used to do the

friction calculations on sprinkler systems for e/ample.


25/62

&he = coefficients use in the abo"e 5aen1Williams equation are %i"en in the table below.

&he source of this equation is the =ameron 5ydraulic 3ata book .

5aen1Williams equation = coefficients.

8ea!6the hei%ht at which a pump can displace a liquid to. 5ead is also a form of ener%y. #n pump systems there are different types of head: ele"ation head or static

head, pressure head, "elocity head and friction head loss. For more information on headsee this tutorial.

0lso known as specific ener%y or ener%y per unit wei%ht of fluid, the unit of head is e/pressed in feet or meters. see also tutorial+


26/62

&ry this calculator to obtain head from pressure.

8y!raulic #ra!ient60ll the ener%y terms of the system ( for e/ample "elocity head and pipin% and fittin% friction loss) are con"erted to head and %raphed abo"e an

ele"ation drawin% of the installation. #t helps to "isualie where all the ener%y terms are located and ensure that nothin% is missed.

'mpeller6&he rotatin% element of a pump which consists of a disk with cur"ed "anes. &he impeller imparts mo"ement and pressure to the fluid.

7ee this paper on impellers by the !c@ally #nstitute.

Fi%ure A !aor pump parts and terminolo%y.

&he impeller consists of a back plate, "anes and for closed impellers a front plate or shroud. #t may be equipped with wear rin%s, back "anes and balancin% holes.


27/62

for more on the different impeller types see impeller.htm.

'mpeller eye6that area of the centrifu%al pump that channels fluid into the "ane area of the impeller. &he diameter of the eye will control how much fluid can %et into

the pump at a %i"en flow rate without causin% e/cessi"e pressure drop and ca"itation. &he "elocity within the eye will control the @75C, see this chart.

see also centrifu%al1pump1tips.htm

For more information on pump part terminolo%ysee this web pa%e.

'n!ucer6an inducer is a de"ice attached to the impeller eye that is usually shaped like a screw that helps increase the pressure at the impeller "ane entrance and

make "iscous or liquids with hi%h solids pumpable. #t can also be used to reduce the @75C.


28/62

(ima%e source: &he Worthin%ton ump =o. 1 umpworld).

see articles on inducers on this web pa%e:pumpworld.htm

'nternal #ear pump: a positi"e displacement pump.

&he internal %ear pumpin% principle was in"ented by Jens @ielsen, one of the founders of >ikin% ump. #t uses two rotatin% %ears which un1mesh at the suction side of

the pump to create "oids which allow atmospheric pressure to force fluid into the pump. &he spaces between the %ear teeth transport the fluid on either side of a

crescent to the dischar%e side, and then the %ears re1mesh to dischar%e the fluid. >ikin%'s internal %ear desi%n has an outer dri"e %ear (rotor1 shown in oran%e) which

turns the inner, dri"en %ear (idler1shown in white).

>ikin% umps is a maor supplier of these pumps http:DDwww."ikin%pump.comD.

:et pump: a et pump is a commonly a"ailable residential water supply pump. #t has an interestin% cle"er desi%n that can lift water from a well (up to +A feet) and


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allow it to function without a check "al"e on the suction and furthermore does not require primin%. &he heart of the desi%n is a "enturi(source of water is from the

dischar%e side of the impeller) that creates low pressure pro"idin% a "acuum at the suction and allowin% the pump to lift fluids.

see this article for more information

"isit this manufacturer (and no, # don't %et a commission) for more info

0nother %ood web site on this topic.

; factor: a factor that pro"ides the head loss for fittin%s. #t is used with the followin% equation

&he factor for "arious fittin%s can he found in many publications. 0s an e/ample, Fi%ure B depicts the relationship between the factor of a H*L screwed elbow

and the diameter (3). &he type of fittin% dictates the relationship between the friction loss and the pipe sie.

@ote: this method assumes that the flow is fully turbulent (see the demarcation line on the !oody dia%ram of Fi%ure H).

Fi%ure B factor "s. diameter of fittin% (source: 5ydraulic #nstitute 8n%ineerin% data book)

0nother %ood source for fittin% factors is the =rane &echnical 3ata 2rochure.

Fi%ure >alues for the factor with respect to the friction factor for a standard tee.

&he =rane technical paper %i"es the "alue for a fittin% in terms of the term f&as in this e/ample for a standard tee.

0s is the case for the data shown in Fi%ure B, the friction loss for fittin%s is based on the assumption that the flow is hi%hly turbulent, in fact that it is so turbulent that

the Ceynolds number is no lon%er a factor and pipe rou%hness is the main parameter affectin% friction. &his can be seen in the !oody dia%ram. &here is a line in the

dia%ram that locates the position where full turbulence starts.


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&he term f&used by =rane is the friction factor and is the same as that %i"en by the =olebrook or the 7wamee1Jain equation.

When the Ceynolds number becomes lar%e the "alue of f&(usin% the 7wamee1Jain equation) becomes:

furthermore the =rane &echnical aper @o. *assumes that the rou%hness of the material will correspond to new steel whose "alue is *.***A ft. &herefore, the

pre"ious equation for f&becomes:

&herefore the "alue of the factor is easily calculated based on the diameter of the fittin%, the friction factor f&and the multiplication factor for each type of fittin%.

Laminar: 0 distinct flow re%ime that occurs at low Ceynolds number(Ce M+***). #t is characteried by fluid particles in layers mo"in% past one another without

mi/in%.

Fi%ure K


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>ikin% umps is a maor supplier of these pumps http:DDwww."ikin%pump.comD.

Lo NPS8 pump: a pump desi%ned for application with a [email protected]. a"ailable, usually has an inducer. see inducer


Mec0anical seal: a name for the oint that seals the fluid in the pump stoppin% it from comin% out at the oint between the casin% and the pump shaft. &he followin%

ima%e (source: the ump 5andbook by !c;raw15ill) shows a typical mechanical seal. 0 mechanical seal is a sealin% de"ice which forms a runnin% seal between

rotatin% and stationary parts. &hey were de"eloped to o"ercome the disad"anta%es of compression packin%.


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&he 5ydraulic #nstitutehas offered these %uidelines for minimum @750 dependin% on the le"el of suction ener%y.

!inimum @75 !ar%in Catio ;uidelines @750D@75C

7uction ener%y le"els

Application


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but # looked lon% and hard to find a chart that pro"ides the frame sie "s. the rpm and hp, and here it is:

Moo!y !ia#ram: 0 %raphical representation of the laminar and turbulent (=olebrook) flow equations.


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Fi%ure H the !oody dia%ram, a %raphical representation of the laminar flow equation and the =olebrook equation for the friction factor f.

Net Positi2e Suction 8ea! A2ailable "N*P*S*8*A*$: @et positi"e suction head a"ailable. &he head or specific ener%y at the pump suction flan%e less the "apor

pressure head of the fluid. [email protected]

7ee this calculator for @.7.5.0.

0lso for those who need to know about @750 but hate that stuffy word .

Net Positi2e Suction 8ea! Re5uire! "N*P*S*8*R*$: @et positi"e suction head required. &he manufacturers estimate on the @75 required for the pump at a

specific flow, total head, speed and impeller diameter. &his is determined my measurement. see [email protected]

&his ne/t fi%ure pro"ides an estimate for @75C for centrifu%al pumps (source: =entrifu%al ump 3esi%n N 0pplication by >al.7.


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Netonian flui!: 0 fluid whose "iscosity is constant and independent of the rate of shear (strain). For @ewtonian fluids, there is a linear relationship between the rate

of shear and the tan%ential stress between layers.



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Fi%ure * 7hearDstrain relationship for a @ewtonian fluid.

#f you want to understand what a non1@ewtonian fluid feels like and what it means for "iscosity to chan%e with the rate of shear, try this e/periment.

#n a lar%e shallow bowl make a solution of appro/imately part water and + parts corn starch, try mo"in% this fluid rapidly around with your fin%ers. When the fin%ers

are mo"ed slowly, the solution beha"es as e/pected, offerin% little resistance. &he faster you try to mo"e throu%h the fluid, the hi%her the resistance. 0t that rate of

shear, the solution almost beha"es as a solid, #f you mo"e your fin%ers fast enou%h they will skip o"er the surface. &his is what is meant by "iscosity bein% dependent

on rate of shear. =ompare this beha"ior to that of molassesQ you will find that e"en thou%h molasses is "iscous its "iscosity chan%es "ery little with the shear rate.

!olasses flows readily no matter how fast the mo"ement.

7ee a"ideo presentation of this e/periment .

Operatin# point: &he point (flow rate and total head) at which the pump operates. #t is located at the intersection of the system cur"eand the performance cur"e of

a pump. #t corresponds to the flow and head required for the process.

Fi%ure Eperatin% point on a pump performance cur"e.

Pac1in#: see stuffin% bo/.

Partial emission pump: see radial "ane pump.


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Perip0eral "re#e nerati2e$ pump: also known as re%enerati"e or re%enerati"e turbine pump. &hese are low capacity (A* %pm or ? m?Dh) hi%h head (A** ft or

BA m) pumps. &he impeller has short "anes at the periphery and these "anes pass throu%h an annular channel. &he fluid enters between two impeller "anes and is

set into a circular motion, this adds ener%y to the fluid particles which tra"el in a spiral like path from the inlet to the outlet. 8ach set of "anes continuously adds ener%y

to the fluid particles.

eripheral pumps are more efficient at these low flow hi%h head conditions than centrifu%al pumps, they also require much less @750 than an equi"alent centrifu%al

pump. &hey can also handle liquids with up to +*9 entrained %ases. &hey can be run in C8>8C78 which can sometimes be an interestin% ability in certain cases.

&hey are used in a wide ran%e of domestic and industrial applications.

For a %ood e/planation of the principal of operation see thispa%e from the !epco web site

and also from the Coth ump =o .

see also this newsletterfrom


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Performance cur2e: 0 plot of &otal 5ead "s. flow for a specific pump model, impeller diameter and speed (syn characteristic cur"e, water performance cur"e). see

Fi%ure

For more information on performance or characteristic cur"esee this tutorial

Pipe rou#0ness: 0 measurement of the a"era%e hei%ht of peaks producin% rou%hness on the internal surface of pipes. Cou%hness is measured in many locations and

then a"era%ed, it is usually defined in micro1inches C!7 (root mean square). 3ownload or "iew a pipe rou%hness chart in pdf format

Pipin# pressure "ma-imum$: it may be necessary in certain applications to check the ma/imum ratin% of your pipes to a"oid burstin% due to e/cessi"e pressure. &he

07!8 pressure pipin% code 2?.? pro"ides the ma/imum stress for pipes of "arious materials. 0lso the pipe flan%e ratin% will ha"e to be checked.

for more information see ma/Ipipin%IoperIpress.pdf

&able of allowable pipin% stress from the 07!8 pressure pipin% code 2?.?

Pitot pump: also know as rotatin% casin% pump. &his pumpRs specialty is low to medium flow rates at hi%h pressures. #t is frequently used for hi%h pressure shower

supply on paper machines.


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itot (Coto1et ) pump


see also this newsletterfrom


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where is the fluid density and is water density at standard conditions. 7ince

where is the fluid density in terms of wei%ht per unit "olume. &he constant %c is required to pro"ide a relationship between mass in lbm and force in lbf .

&he quantity ( B+.? lbmDft?for water at B* LF) is:

0fter simplification, the relationship between the fluid column hei%ht and the pressure at the bottom of the column is:

Pro#ressi2e ca2ity pump: a positi"e displacement pump. &hese pumps are ideal for fluids that are ust too tou%h for other pumps to handle. e.%. S pastes, %reases,

slud%e etc. &hey consist of only one dri"en metal rotor rotatin% within an elastomer lined (elastic) stator.


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>ane pump


see also this @ewsletterfrom


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#t is well established that ca"itation type of dama%e seen on the inlet "anes and not associated with inadequate @75 can be directly linked to the pump operatin% in

the suction recirculation one. 7imilar dama%e seen on the dischar%e "ane tips can also be associated with pump operation in the dischar%e recirculation one.

&he suction and dischar%e recirculation may occur at different points as shown on the characteristic cur"e below.


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Re#enerati2e pump: seeperipheral pump, also known as re%enerati"e turbine pump.

Reynol!s number: the Ceynolds number is proportional to the ratio of "elocity and "iscosity, the hi%her the number (hi%her than *** for turbulent flow) the more

turbulent the flow and the less "iscosityhas an effect. 0t hi%h Ceynolds numbers (see the transition line to complete turbulence in the !oody dia%ram) thepipe

rou%hnessbecomes the controllin% factor for friction loss. &he lower the Ceynolds number (less then +*** for laminar flow) the more the "iscosity of the fluid is

rele"ant. !ost applications are in the turbulent flow re%ime mode unless the fluid is "ery "iscous (for e/ample ?** c7t and up), the "elocity has to be "ery low to

produce the laminar flow re%ime.

R0eopectic: &he property of a fluid whose "iscosity increases with time.


Rubber pump liner: see slurry pump.

Scre impeller: &he screw centrifu%al impeller is shaped like a tapered 0rchimedes screw. Eri%inally de"elopped for pumpin% li"e fish, the screw centrifu%al pump

has become popular for

many solids handlin% applications.

for more information see this newsletter from


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7elf1primin% pump


S0rou!: see end1suction pump.

S0ut7off 0ea!: &he &otal 5ead correspondin% to ero flow on the pump performance cur"e.

Fi%ure + 7hut1off head and other points on a centrifu%al pump performance cur"e.

&he shut1off head is the &otal 5ead that the pump can deli"er at ero flow (see ne/t Fi%ure). &he shut1off head is important for + reasons.

. #n certain systems (admittedly unusual), the pump dischar%e line may ha"e to run at a much hi%her ele"ation than the final dischar%e point. &he fluid must first reach

the hi%her ele"ation in the system. #f the shut1off head is smaller than the static head correspondin% to the hi%h point, then flow will not be established in the system.

+. 3urin% start1up and checkout of the pump, a quick way to determine if the pump has the potential capacity to deli"er the head and flow required, is to measure the

shut1off head. &his "alue can be compared to the shut1off head predicted by the performance cur"e of the pump.


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Si!e c0annel pump: is a pump that pro"ides hi%h head at low flows with the added benefit of bein% able to handle %ases. &he principle of the pump is well e/plained

on the 7ero umpweb site. # ha"e included apdf "ersion of the web site material (as is) ust in case one day the 7ero web pa%e is chan%ed or disappears, my

thanks to 7ero for makin% this a"ailable.&he principal of the side channel is similar to the re%enerati"e (peripheral)pump.

6ou will find other e/amples and suppliers of side channel pumps in the pump data baseusin% pump type: side channel.

Sip0on: 0 system of pipin% or tubin% where the e/it point is lower than the entry point and where some part of the pipin% is abo"e the free surface of the fluid source.


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Fi%ure 0 siphon.

7ee this article for a description of how a siphon works.

Slu!#e pump: certain types of slud%es tend to settle "ery quickly and are hard to keep in suspension. &he


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Slurry pump: a ru%%ed hea"y duty pump intended for a%%ressi"e or abrasi"e slurry solutions typically found in the minin% industry with particles of "arious sies. #t

achie"es this by linin% the inside of the pump casin% as well as the impeller with rubber.

7lurry pump

see see detail drawin% for more information


and also Warman 7lurry umpin% 5andbook

Specific #ra2ity "SG$: the ratio of the density of a fluid to that of water at standard conditions. #f the 7; is then the density is the same as water, if it is less than

then the fluid is less dense than water and hea"ier than water if the 7; is bi%%er than . !ercury has an 7; of , %asoline has an 7; of *.K. &he usefulness of

specific %ra"ity is that it has no units since it is a comparati"e measure of density or a ratio of densities therefore specific %ra"ity will ha"e the same "alue no matter

what system of units we are usin%, #mperial or metric.

For more information see specific %ra"ity.pdf

7ee this e/periment on "ideo showin% that total head is independant of density or specific %ra"ity .


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the abo"e ima%e is from the =ameron 5ydraulic data book which contains a %reat deal of information on fluid properties. &o purchase %o to the Flow 7er"e web site.

Specific spee!: a number that pro"ides an indication what type of pump (for e/ample radial, mi/ed flow or a/ial) is suitable for the application. &he fi%ure below is

know as the &al


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&he picture for this pump is pro"ided courtesy of 0ce umps.

Stan!ar! 2olute pump separately couple!: &he "olute is the casin% which has a spiral shape. &he motor shaft is connected to the impeller with an intermediate

shaft with two couplin%s.

&he picture for this pump is pro"ided courtesy of 0llweiler.

Strain: &he ratio between the absolute displacement of a reference point within a body to a characteristic len%th of the body. see Fi%ure *.

Stress: #n this case refers to tan%ential stress or the force between the layers of fluid di"ided by the surface area between them.

Stuffin# bo-: the oint that seals the fluid in the pump stoppin% it from comin% out between the casin% and the pump shaft. &he followin% ima%e (source: the ump

5andbook by !c;raw15ill) shows a typical stuffin% bo/ with %land packin%. &he function of packin% is to control leaka%e and not to eliminate it completely. &hepackin% must be lubricated, and a flow from * to B* drops per minute out of the stuffin% bo/ must be maintained for proper lubrication. &his makes this type of seal

unfit for situations where leaka%e is unacceptable but they are "ery common in lar%e primary sector industries such a minin% and pulp and paper.

For more information see this ;oulds pump web pa%e.


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Submersion: 7ubmersion as used here is the hei%ht between the free surface of a suction tank and the pump intake pipe.

Fi%ure ? !inimum submersion to a"oid "orte/ formation.

&ry this calculator for minimum submersion hei%ht.

5ere's a nice picture of an a/ial flow pump with an suction intake submersion problem.


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see this "ideo on submersion

and for more information on this web site see this help file for the submersion calculation applet.

&he 5ydraulic #nstitutepublishes a %uide on ump #ntake 3esi%n that pro"ides detail recommendations.

&he ;oulds pump company pro"ides similarpump intake desi%n recommendations at no cost.

Suction flo splitter: a rib of metal across the pump suction that is installed on certain pumps. #t's purpose is to remo"e lar%e scale "orte/es so that the stream lines

are as parallel as possible as the fluid enters the impeller eye.

Suction #ui!e: a de"ice that helps strai%hten the flow ahead of a pump that has a H* de%ree elbow immediately ahead of it.

&here are two types of suction %udes as far as # know.

7uction %uide by 0rmstron%, see http:DDwww.armstron%pumps.com

&he other type of suction %uide is the =hen% "ane system


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&he =hen% "ane, see http:DDwww.chen%fluid.com

0nother manufacturer of standard suction %uide components from +$ to $ diameter is !etrafle/. 2ell ;ossett produce a suction %uide they call a suction diffuser

see the 2ell ;ossett sales brochure on suction diffusers

Suction 2ane: see suction %uide.

Suction specific spee!: a number that indicates whether the suction conditions are sufficient to pre"ent ca"itation. 0ccordin% to the 5ydraulic #nstitute the suction

specific speed should be less than KA**. Ether e/periments ha"e shown that the suction specific speed could be as hi%h as ***.

When a pump has a hi%h suction specific speed "alue, it will also mean that the impeller inlet area has to be lar%e to reduce the inlet "elocity which is needed to enablea low @75C. 5owe"er, if you continue to increase the impeller inlet area (to reduce @75C), you will reach a point where the inlet area is too lar%e resultin% in

suction recirculation (hydraulically unstable causin% "ibration, ca"itation, erosion etc..). &he recommended ma/imum suction specifc speed "alue is to a"oid reachin%

that point. (para%raph contributed by !ike &an of thepump forum %roup).

eepin% the suction specific speed below KA** is also a way of determinin% the ma/imum speed of a pump and a"oidin% ca"itation.

For a double suction pump, half the "alue of 4 is used for calculatin% the suction specific speed.

7uction specific speed is calculated with this formula:

see also specific speed

&he con"ersion from metric to imperial suction specific speed 7mis %i"en below:

&he term @77is also used to represent the suction specific speed.

0ccordin% to the 5ydraulic #nstitutethe efficiency of the pump is ma/imum when the suction specific speed is between +*** and ***. When 7 lies outside this

ran%e the efficiency must be derated accordin% to the followin% fi%ure.


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source: ump N 7ystems ma%aine 0u%ust +**A

for an article on this topic see specific1speedIprimer.pdf

and here is a calculator for suction specific speed.

&he followin% chart pro"ides some more precise %uidelines on desirable suction specific speed operatin% ran%es.

7ource: rocess #ndustry ractices C87 ** 3esi%n of umpin% 7ystems that use =entrifu%al umps.

Suction Static 8ea!: &he difference in ele"ation between the liquid le"el of the fluid source and the centerline of the pump ( see Fi%ure ). &his head also includes

any additional pressure head that may be present at the suction tank fluid surface, for e/ample as in the case of a pressuried suction tank.

Suction Static Lift: &he same definition as the 7uction 7tatic head. &his term is only used when the pump centerline is abo"e the suction tank fluid surface.

System: as in pump system. &he system includes all the pipin%, includin% the equipment, startin% at the inlet point (often the fluid surface of the suction tank) and

endin% at the outlet point (often the fluid surface of the dischar%e tank).

System 3ur2e: 0 %raphical representation the pump &otal 5ead "s. flow. =alculations are done for the total head at different flow rates, these points are linked and

form a cur"e called the system cur"e. #t can be used to predict how the pump will perform at different flow rates. &he &otal head includes the static head which is

constant and the friction head and "elocity head difference which depends on the flow rate (see Fi%ure ). &he intersection of the system cur"e with the pump

characteristic cur"e defines the operatin% point of the pump.

=han%es to the system such as openin% or closin% "al"es or makin% the dischar%e pipe lon%er or shorter will chan%e the friction head which will chan%e the shape of

the system cur"e and therefore the operatin% point. #n the followin% fi%ure there is a system which has a static head of ** feet and a total system resistance of

appro/imately +* feet shown by cur"e 0. &here is a "al"e at the pumpdischar%e which is partially closed. #f the friction head is increased (i.e. "al"e is closed) then the

operatin% point will shift from 0 to point 2 and the flow will drop. #f the friction head is decreased (i.e. "al"e is opened) then the operatin% point will shift to point =

and the flow increases.


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System re5uirements: &hose elements that determine &otal 5ead: friction and the system inlet and outlet conditions (for e/ample "elocity, ele"ation and pressure).

Samee7:ain e5uation: an equation that can be used as a substitute for the =olebrook equation for calculatin% the friction factor f.

T0i-otropic: &he property of a fluid whose "iscosity decreases with time.

Total Dynamic 8ea!: #dentical to &otal 5ead. &his term is no lon%er used and has been replaced by the shorter &otal 5ead.

Total 8ea!: &he difference between the pressure head at the dischar%e and suction flan%e of the pump ( syn &otal 3ynamic 5ead.pump head, system head). see

also tutorial?.htm

Total Static 8ea!: &he difference between the dischar%e and suction static head includin% the difference between the surface pressure of the dischar%e and suction

tanks if the tanks are pressuried (see Fi%ure ). 7ee alsotutorial?.htm

Turbulent: &he beha"ior of fluid articles within a flow stream characteried by the rapid mo"ement of particles in many directions as well as the %eneral direction of

the o"erall fluid flow.

,acuum: pressure less than atmospheric pressure.

,anes "no*of$: see impeller.htm.


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,ane pass fre5uency: when doin% a "ibration analysis this frequency (no. of "anes times the shaft speed) and it's e"en multiples shows up as a peak which can

indicate a dama%ed or imbalanced impeller.

Fi%ure A @oise "ibration spectra showin% "ane pass frequency (source: &he ump 5andbook publ. by !c;raw5ill)

see articles on pump "ibration sources on this web pa%e:pumpworld.htm

,ane pump: see radial "ane pump.

,ane pump "0y!raulic$: a positi"e displacement pump. >ane pumps are used successfully in a wide "ariety of applications (see below). 2ecause of "ane stren%th

and the absence of metal1to1metal contact, "ane pumps are ideally suited for low1"iscosity, non lubricatin% liquids up to +,+** c7t D *,*** 77. 7uch liquids include

anes or blades fit within the slots of the impeller. 0s the impeller rotates (yellow arrow) and fluid enters the

pump, centrifu%al force, hydraulic pressure, andDor pushrods push the "anes to the walls of the housin%. &he ti%ht seal amon% the "anes, rotor, cam, and sideplate is

the key to the %ood suction characteristics common to the >ane pumpin% principle.

+. &he housin% and cam force fluid into the pumpin% chamber throu%h holes in the cam (small red arrow on the bottom of the pump). Fluid enters the pockets created

by the "anes, rotor, cam, and sideplate.

?. 0s the impeller continues around, the "anes sweep the fluid to the opposite side of the crescent where it is squeeed throu%h dischar%e holes of the cam as the "ane

approaches the point of the crescent (small red arrow on the side of the pump). Fluid then e/its the dischar%e port.

Ce/roth is a maor manufacturer of "ane pumps http:DDwww.boschre/roth.comD

see also http:DDwww.pumpschool.comDprinciplesD"ane.htm

,apor pressure: &he pressure at which a liquid boils for a specific temperature.


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Fi%ure B &he boundary between liquid and "apor phase of a fluid. 0 fluid can be "aporied by increasin% the temperature or decreasin% the pressure.

Fi%ure >apor pressure "s. temperature for "arious fluids.

>alues for "apor pressure of common liquidsis a"ailable in the ;oulds pump catalo%ue.

,enturi "&ernoulli=s la$: a "enturi is a pipe that has a %radual restriction that opens up into a %radual enlar%ement. &he area of the restriction will ha"e a lower

pressure than the enlar%ed area ahead of it. #f the difference in diameters is lar%e you can e"en produce a "ery hi%h "acuum (1+K feet of water). # use a cheap plastic

"enturi made by Fisher or =ole almer for an e/periment that # do to demonstrate "apor pressure durin% my trainin% seminars and it is "ery easy to create "ery hi%h

absolute "acuum.

#n certain locations # can't do this e/periment, because hey don't ha"e a source of water in hotel suites, too bad because it's always a winner, so # ha"e to re"ert to a


58/62

"ideo . #t's a !e% download so you better ha"e a fast connection to "iew it. #f you want to purchase this nifty plastic "enturi you can %et it here at Fisher

7cientific it only costs T*, and no, # don't %et a commission.

#t is not easy to understand why low pressure occurs in the small diameter area of the "enturi. # ha"e come up with this e/planation that seems to help.

#t is clear that all the flow must pass from the lar%er section to the smaller section. Er in other words, the flow rate will remain the same in the lar%e and small portions

of the tube. &he flow rate is the same, but the "elocity chan%es. &he "elocity is %reater in the small portion of the tube. &here is a relationship between the pressure

ener%y and the "elocity ener%y, if "elocity increases the pressure ener%y must decrease. &his is the principle of conser"ation of ener%y at work which is also

2ernoulli's law. &his is similar to a bicycle rider at the top of a hill. 0t the top or point (see Fi%ure K below), the ele"ation of the cyclist is hi%h and the "elocity low.

0t the bottom (point +) the ele"ation is low and the "elocity is hi%h, ele"ation (potential) ener%y has been con"erted to "elocity (kinetic) ener%y. ressure and "elocity

ener%ies beha"e in the same way. #n the lar%e part of the pipe the pressure is hi%h and "elocity is low, in the small part, pressure is low and "elocity hi%h.


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Fi%ure K &he "enturi effect.

2ernoulli's law is a relationship between two points within a system that states that the sum of the ener%ies that correspond to pressure, "elocity and ele"ation must be

conser"ed.

&he %eneral form of the law (ne%lectin% friction) is:

where pis the pressure, "the "elocity and hthe ele"ation at point and the same parameters are used at point +. ;amma is the fluid density and % the

acceleration due to %ra"ity.

#n the case of the cyclist there is no pressure and only the "elocity and ele"ation can "ary, so that 2ernoulli's law becomes:

as the cyclist %oes down the hill h+becomes smaller than hand to balance the equation then "+must be lar%er than ".

#n the case of the "enturi tube there is no ele"ation chan%e and only the "elocity and pressure can "ary, so that 2ernoulli's law becomes:

We can clearly see that if "+ is %reater than " then p+ must be smaller than " to balance the equation.

for an article on this and related subects seeunusualIaspects1pumps1syst.pdf

,iscosity: 0 property from which a fluid's resistance to mo"ement can be e"aluated. &he resistance is caused by friction between the fluid and the boundary wall and

internally by the fluid layers mo"in% at different "elocities. &he more "iscous the fluid the hi%her the friction loss in the system. =entrifu%al pumps are affected by

"iscosity and for fluids with a "iscosity hi%her than * c7t, the performance of the pump must be corrected. se this calculator to determine the correction for

"iscosity to the water performance cur"e of the pump.

&he followin% fi%ure which you can find in the ;oulds pump catalo%ue in the &echnical 7ection shows the effect of "iscosity on pump performance.


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&his ne/t fi%ure is a chart of "alues for "iscosity for different liquids which you can find in the =ameron 5ydraulic data book.

&he basic unit of "iscosity is known as the oise or centioise (c) named after the French scientist oiseuille who disco"ered a practical method of measurin%"iscosity. &he %reek letter is used to represent "iscosity. &here are two types of "iscosity, the first ust mentioned is known as absolute "iscosity and the other for

which the %reek letter nu is used is called the kinematic "iscosity. &he unit of kinematic "iscosity is the centi7toke (c7t) named after the 8n%lish scientist 7tokes.

&he relationship between the two is:

>iscosity data of common liquidscan also be found in the ;oulds pump catalo%ue.

,iscosity correction: see "iscosity.

,iscous !ra# pump: a pump whose impeller has no "anes but relies on fluid contact with a flat rotatin% plate turnin% at hi%h speed to mo"e the liquid.


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>iscous dra% pump


,olute: syn casin%.

,orte-: see submersion.

,orte- pump: see recessed impeller pump.

%ater 0ammer "pressure sur#e$: #f in systems with lon% dischar%e lines,(e.%. in industrial and municipal water supply systems ,in refineries and power stations) the

pumped fluid is accelerated or decelerated, pressure fluctuations occur owin% to the chan%es in "elocity. #f these "elocity chan%es occur rapidly , they propa%ate a

pressure sur%e in the pipin% system, ori%inatin% from the point of disturbance Q propa%ation takes place in both directions (direct wa"es),and these wa"es are reflected(indirect wa"es) at points of discontinuity ,e.%. chan%es of the cross sectional area ,pipe branches, control or isolatin% "al"es, pumps or reser"oir. &he boundary

conditions decide whether these reflections cause ne%ati"e or positi"e sur%es. &he summation of all direct and indirect wa"es at a %i"en point at a %i"en time produces

the conditions present at this point.

&hese pressure sur%es, in addition to the normal workin% pressure ,can lead to e/cessi"e pressure and stresses in components of the installation . #n se"ere cases such

pressure sur%es may lead to failure of pipe work, of fittin%s or of the pump casin%s. &he minimum pressure sur%e may, particularly at the hi%hest point of the

installation ,reach the "apor pressure of the pumped liquid and cause "aporiation leadin% to separation of the liquid column. &he ensuin% pressure increase and

collision of the separated liquid column can lead to considerable water hammer .&he pressure sur%es occurrin% under these conditions can also lead to the failure or

collapse of components in the installation.

For the ma/imum pressure fluctuation the JEEW76 pressure sur%e formula can be used:

Up V . a . U"

Where V density of the pumped liquid

a "elocity of wa"e propa%ation

U" chan%e of "elocity of the flow in the pipe.

&he full pressure fluctuation correspondin% to the chan%e of "elocity U" occurs only if the chan%e of "elocity U" takes place durin% the period.

t reflection time tr +.l Da

where l distance between the nearest discontinuity (point of reflection ) and the point of disturbance .

0 contribution from !oshe 7hayan of the pump discussion forum.

&his article titled 7ur%e =ontrol in umpin% 7tationby >al1!atic >al"e appeared in the umps N 7ystems ma%aine of !arch +**, it's a "ery %ood description of

how water hammer occurs and how it can be controlled.

6ou can oin the centrifu%al pump discussion forum at http:DDwww.pumpfundamentals.comDforum

0nother interestin% article from the ump1Xone http:DDwww.pump1one.comDarticle.phpOarticleid?B?


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&E

visual pump glossary.pdf

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