weigh feeder training module

8/18/2019 Weigh Feeder Training Module

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Manufacturing Workforce Training

HGRS MASTER - MAINTENANCE

Training Module: Weigh Feeders

Presentation: Weigh Feeder Training Module!!t

Version: "#

Last Update: $%-#%-#%


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Weigh Feeder Training Module!!tHolci' Grou! Su!!ort Weigh Feeder

()*ecti+e

Weigh Feeder is intended to )e a co'!rehensi+etraining 'aterial for all technical staff ,ithin Holci'

Grou! co'!anies

It ,ill fa'iliarie .ou ,ith the general kno,ledge as

,ell as ,ith the 'aintenance re/uire'ents


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Weighfeeder Weighfeeder

Electrical componentsElectrical components

Calibration unctionCalibration unction

TroubleshootingTroubleshooting

Function (!erating 0rinci!le

Taring and 1ero Setting

Weight Check Cali)ration 2Test Weights3

(+er+ie,

Weigh Measuring Circuit

Flo, Control Circuit

4ri+ing Motor Circuit

Material Flo,

Mechanical Co'!onents

Tracing 5ack the 4efect

Material test

MaintenanceMaintenance Maintenance

Content of 0resentation

Mechanical componentsMechanical components

Set 0oint Increase 6 S.ste' Reaction

Changing of 5elt

5elt S!licing

Training of 5elt

S!eed Measuring Circuit

Cali)ration


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Function of a Weigh Feeder

Weigh feeders are designed to deli+er a designated rate of 'aterial

in a !rocess The. are used to con+e.7 ,eigh7 and control the flo,

rate of )ulk 'aterials ). +ar.ing the s!eed of the )elt

The. transfor' a +aria)le 'aterial flo, into a constant and

controlla)le flo,

A su)-function of a ,eigh feeder is to reduce the !ossi)ilit. of

s!illages7 leakages7 and dust e'issions


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The s!eed and load of the )eltand 'aterial deter'ines the flo,

5asic For'ula8

#PEE$ L%&$ L%W' (

In all cases8 9This is the first control

function of the flo,:

Weigh feeder continuousl. ,eighs and feeds )ulk solids The )elt load is

'easured through a ,eigh)ridge located under the con+e.or )elt A control

loo! ad*usts feed rate L%W to a !reset set !oint +ia )elt #PEE$ The ,eigh)ridge is li'ited ). t,o carr.ing idlers 5. 'eans of a centrall.

!ositioned ,eigher idler and a le+er s.ste'7 the load on the !latfor' e;erts a

force7 !latfor' L%&$7 on a load cell The out!ut +oltage of the load cell is

!ro!ortional to the !latfor' load and is transfor'ed into digital infor'ation

though an A4 con+erter

(!erating 0rinci!le of a Weigh Feeder


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(!erating 0rinci!le of a Weigh Feeder

In short8

The 'aterial flo,s fro' the ho!!er onto the 'o+ing )elt7 and o+erthe ,eigh )ridge

The 'aterial on the )elt e;erts a load on the ,eigh )ridge 2li'ited

). t,o idlers3

The out!ut signals of the ,eigh )ridge and the )elt s!eed is

con+erted into a flo, and co'!ared to a !reset +alue

Through a feed)ack loo! to the 'otor dri+e of the )elt7 the s!eed is

ad*usted to achie+e the desired flo,

Changes in its thickness and sha!e 'a. re+eal the !resence of

!ro)le's in the 'aterial flo, u!-line fro' the )elt


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A!!lications in the 0lant

Ra, Mill Feed

Ce'ent Mill Feed

Coal Mill Feed

Coal Feed

AFR 4osing


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Mechanical Co'!onents

Feeding Ho!!er

Manual Control Gate

Side Skirts

Cali)ration Weight

Idlers and Idler Su!!ort

4ri+ing 0ulle.

5elt Cleaning 4e+ice

Tensioning 4e+ice


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Feeding Ho!!er

Function8

The feeding ho!!er for's a s'all )uffer stock )et,een the 'aterialstorage and the !ro!ortional feeder It a)sor)s large flo,

fluctuations fro' !receding e/ui!'ent


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Manual Control Gate

Function8

It defines the initial setting of the )ed height to )e in the o!eratingrange of the load cell

This is si'!l. a thick steel !late !ositioned and fi;ed ,ith )olts 5.

ad*usting the gate !osition7 changes to the height of the 'aterial

)ed on the )elt is !ossi)le The gate is set during the initial

cali)ration of the ,eighing de+ice and is fi;ed once the o!ti'u'height has )een deter'ined The height of 'aterial )ed deter'ines

also the o!erating s!eed range of the ,eigh feeder 6 So'e ,eigh

feeders do not ha+e a control gate=


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Side Skirts

Function8

Side skirts contain the 'aterial ,ithin the )elt ,idth7 a+oidings!illages to the sides

The. are generall. 'ade of ru))er Care has to )e taken that the.

do not e;ert force on the load cell7 thus influencing the reading

In other designs the skirting ru))er is an integral !art of the )elt7a+oiding the a)o+e risk


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Cali)ration Weight

Function8

Cali)rated ,eights are hooked to the ,eighing 'echanis' to checkthe correct functioning of the load cell

The. 'ust )e re'o+ed after cali)ration ========


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Idlers and Idler Su!!ort

Function8

The ,eigh feeder )elt 'o+es on a series of idlers The idlersaround the load cell 'ust )e fi;ed ,ith !recision su!!orts

So'e idlers are 'ounted on a fra'e su!!orted ). the ,eighing

'echanis' on the load cell


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Mechanical 4ri+e 0arts

Function8

The dri+e is the 'echanical link )et,een the +aria)le s!eed 'otorand the dri+ing !ulle.

/t consists of a:

Cou!ling and a

Reducer or Chain 4ri+e

An. 'echanical !ro)le' ,ill o)+iousl. distur) the o!eration of the

,eighing de+ice


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4ri+ing 0ulle.

Function8

The dri+e !ulle. !ro+ides the force to 'o+e the )elt It is dri+en ). a+aria)le s!eed 'otor +ia a reducer or a chain


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5elt Cleaning 4e+ice

Function8

The )elt cleaners ensure that 'aterial does not )uild u! on the )eltand alter the cali)ration

The cleanliness of the area is highl. de!ended of the !ro!er

functioning

All con+e.ors are to )e e/ui!!ed ,ith a

suitable belt cleaning s0stem for re'o+ingthe 'a;i'u' a'ount of carr.-)ack 'aterialfro' the )elt>s surface !rior to e;iting thedischarge chute enclosure

In all a!!lications7 the 'ini'u' re/uire'ent

is a dual belt cleaning s0stem7 consistingof a !re-cleaner ? !ri'ar. cleaner and a'ulti-)laded secondar. cleaner


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Tensioning 4e+ice

Functions8

The T4 stretches the )elt7 in order to ha+e a defined ero load onthe load cell

It forces the )elt to re'ain centered on the !ulle.s 2so'eti'es

guiding idlers or li'it idlers are additionall. fitted on the sides3

The de+ice nor'all. consists

of a tensioning scre, on

each side of the tail !ulle.


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WE/1 MEU/41 C/CU/TWE/1 MEU/41 C/CU/T

2@(A4 MEASRE B AM0@IFIER32@(A4 MEASRE B AM0@IFIER3

L%W C%4T%L C/CU/TL%W C%4T%L C/CU/T

2F@(W MEASRING CIRCIT32F@(W MEASRING CIRCIT3

$/V/41 M%T%$/V/41 M%T%

C/CU/TC/CU/T

#PEE$ MEU/41 C/CU/T#PEE$ MEU/41 C/CU/T

2S0EE4 MEASRE32S0EE4 MEASRE3

Electrical Co'!onents of a Weigh Feeder


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Weight Measuring Circuit

So'e idlers are su!!orted ). a ,eighing 'echanis' on a load

cell The latter transfor's the load !ressure into an electric signal

The s'all signal of the load cell 'ust )e a'!lified )efore it can )eused for the s!eed control and accordingl. for flo, control

The circuit consists of:

@oad Cell 0o,er Su!!l.

@oad Cell

5elt @oad Indicator

Weight A'!lifier


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Electrical Feed of the @oad Cell 0o,er Su!!l.

Function8

It su!!lies the a!!ro!riate !o,er to the dc load cell It transfor'sthe net,ork +oltage 2$$#ac3 into a %# dc or ac de!ending on

the rectifier cell of the load cell


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4C su!!l. of the @oad Cell

Function8

It sta)ilies the +oltage feed to the load cell When the !o,ersu!!l. is an alternating +oltage 2%#+ac37 the signal goes through a

rectifier cell )efore )eing sta)ilied


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@oad Cell

Function8

The load cell con+erts the ,eight 'easure'ent fro' the )elt into a!ro!ortional electric current

0rinci!le8

The sta)ilied +oltage D " is a!!lied to a Wheatstone )ridge The

resistance +aries linearl. ,ith the load a!!lied on the load cell If no

load is a!!lied7 the +oltage difference )et,een the 'iddle !oints ofthe t,o )ranches fed in !arallel is ero If load is a!!lied7 a +oltage

!ro!ortional to the load is generated


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S,ing chord load cells 2ne, de+elo!'ent3

Al'ost no deflection under load 2##''3

High resolution

Fast sta)iliing

No h.steresis

Insensiti+e to,ards +i)ration

This s.ste' is not reco''ended ). Holci'


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5elt @oad Indicator

Function8

It indicates the ,eight 'easured 2con+ersion of the #- signal toa scale e;!ressed fro' # 6 "## could )e kg?'3

(ften not a+aila)le

in older s.ste's


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Weigh A'!lifier

Functions8

To a'!lif. the out!ut signal of the load cell fro' )et,een # and %#' and7

To con+ert it into a #- or a #-"# signal de!ending u!on the

e/ui!'ent


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In order to control the )elt s!eed it 'ust first )e 'easured A

tacho'eter is connected to the dri+en !ulle. The for'er !roduces

an electric signal The tacho'eter signal 'ust )e transfor'ed anda'!lified for use


Tacho'eter 2Re+olution Counter3

S!eed Signal A'!lifier

5elt S!eed Indicator

5elt Inde; Indicator 2(!tional3


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Tacho'eter 2Re+olution Counter3

Function

The tacho'eter is a 'otor-cou!led de+ice that generates a +oltage

)et,een its ter'inals !ro!ortional to the rotation of the 'otor

T,o s.ste's are generall. used8

"st case 6 the tacho'eter generator ,hich generates a direct +oltage

$nd case 6 the rotation controller generates !ulse signals7 !ro!ortional to

the rotation s!eed These signals are transfor'ed into an analogue signal

!ro!ortional to the s!eed through a fre/uenc. to +oltage con+erter

emar5: /n latest de6elopments the speed is

directl0 ta5en from the V#$ 7Variable #peed $ri6e8


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S!eed Signal A'!lifier

Function8

It con+erts the s!eed 'easuring signal to the in!ut range of the'ulti!lier used for calculating the flo,

Generall.7 this is an attenuator since the s!eed 'easuring signal

can reach J# ,hile the in!ut signal of the 'ulti!lier cannot

e;ceed


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5ack to Main 'enu

5elt S!eed Indicator

Function8

It dis!la.s the )elt s!eed ). con+erting the in!ut signal #K to a

#K"## scale 2could )e '?s3

T,o standard signals are a+aila)le7 5elt @oad B 5elt S!eed7 their !roduct

gi+es the F@(W This 'ulti!lication is carried out in the flo, 'easuring

circuit

(ften not a+aila)le

in older s.ste's


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Function

A 'ark 2)elt inde;3 is attached to the )elt in one !osition The )eltinde; indicator is gi+ing a signal each ti'e the )elt has 'ade a

co'!lete turn

This de+ice is included in so'e ne,er a!!lication It is used for8

5elt S!eed Cali)ration

Sli! Warning for )elt Seg'ental taring of )elt

5elt Inde; Indicator 2(!tional3

5elt Inde;

Indicator

5elt

Inde; Tacho'eter


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Flo, Control Circuit

T,o signals are a+aila)le7 9ELT L%&$ and 9ELT #PEE$ Their !roductgi+es the L%W and is dis!la.ed as the effecti+e flo, This 'ulti!lication is

carried out in the flo, 'easuring circuit The effecti+e flo, is co'!ared tothe set !oint If the for'er is lo,er than the set !oint7 the flo, 'easuringcircuit sends a signal to increase the )elt s!eed and +ice +ersa


Integrator

Flo, Totalier

Multi!lier

Instantaneous Flo, Indicator

Set 0oint Indicator

Controller Co'!arator


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Integrator

Function

The integrator con+erts the +oltage signal fro' the ,eigh a'!lifierinto a !ulse signal ,ith a fre/uenc. !ro!ortional to it

The integration function is done ). the totalier ===


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Flo, Totalier

Function8

The flo, totalier counts the !ulse co'ing fro' the fre/uenc.con+erter 2integrator3 to gi+e a total ,eight indication of 'aterial

su!!lied ). the ,eighing de+ice since resetting


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Multi!lier

Function

The 'ulti!lier !roduces a +oltage 2L3 !ro!ortional to the !roduct of

the +oltages of the )elt s!eed 23 and of the 'aterial ,eight on the

)elt 203 L ; 0

I t t Fl I di t


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Instantaneous Flo, Indicator

Function8

It allo,s the +isualiation of instantaneous flo, ). con+erting the

out!ut signal of the 'ulti!lier 2#- 3 to a scale of #-"## 2could )e

kg?s3

(ften not a+aila)le

in older s.ste's

S t 0 i t I di t


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Set 0oint Indicator

Function

Ad*usting a set !oint in the controller-co'!arator ,ill change the

)elt s!eed after a co'!arison )et,een the actual and the set !oint

flo,s

C t ll C t


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5ack to Main 'enu

Controller Co'!arator

Function

To co'!are the actual 'easured flo, ,ith the set !oint and act u!on the

)elt dri+e to )ring the actual flo, to the le+el of the set flo,

The co'!arator calculates the difference )et,een the set !oint and the

actual flo, The resulting error signal is sent to the control 'odule of the

'otor

4 i i M t Ci it


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4ri+ing Motor Circuit

The signal co'ing fro' the flo, 'easuring circuit isused to 'odulate the )elt s!eed according to the set

flo, The dri+ing 'otor circuit transfor's the electricsignal co'ing fro' the flo, 'easuring circuit into'echanical action


5elt 4ri+ing Motor

A'!ere Meter

0o,er Su!!l.

Co''and Module of the Motor

5elt 4ri+ing Motor


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5elt 4ri+ing Motor

Function

It is the dri+ing force for the )elt

It is either a S4 2aria)le S!eed 4ri+e3 or in older a!!lications a

4C 24irect Current3 Motor

The direct current 'otor ,as es!eciall. ada!ted as +aria)le s!eed

'otor ). acting on the induced +oltage

E;a'!le of characteristics

of a 4C Motor

A'!ere Meter 2Intensit.38


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A'!ere Meter 2Intensit.38

4C Motor e;a'!le=

Function

The a'!ere 'eter is a digital or dial-t.!e indicating instru'ent for

dis!la.ing the current dra,n ). the induced coil of the direct

current 'otor that dri+es the )elt

0o,er Su!!l.


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0o,er Su!!l.

Function

It su!!lies the 'otor co''and 'odule ,ith alternating current

4C Motor e;a'!le= In case of a S4 it is integrated in the 'otor

co''and 'odule

4e!ending u!on the 4C 'otor !o,er7 the alternating +oltage that

,ill )e rectified ). the th.ristor control 'odule to su!!l. the +aria)le

induced +oltage7 ,ill )e greater than or e/ual to the +oltage that ,ill)e rectified ). the diode )ridge to su!!l. the induced +oltage

2constant3



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Function

The co''and 'odule su!!lies an ade/uate electric feed to the

'otor

4C Motor e;a'!le= In case of a S4 it is integrated in the 'otor

co''and 'odule

The inductor circuit is fed fro' $$# net,ork +ia a diode rectifier

,hile the induced circuit is fed fro' the high +oltage 2## 3through the th.ristor card The th.ristor triggers are fed through a

!ulse generator transfor'ing the #-"# 4C signal recei+ed fro'

the controller-co'!arator

Weigh Feeder Control ,ith 0CS


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There is a tendenc. ,ithin Holci' to integrate thecontrolling functions of a ,eigh feeder into the !lant

control s.ste' 20CS3

Main reason to use o,n 0CS s.ste'


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Weigh eeder a Variable #peed $ri6e 9elt Con6e0or ;ith

Weight Measurement

PCS

Process ControlSystem

Weight

Setpoint,Speed

Belt index

Re/uire'ents for the 0CS


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Re/uire'ents for the 0CS

An. 'odern 0CS can !erfor' a ,eigh feeder control

%# .ears ago the su!!liers used the 0I controller of the 4C dri+e

6 the 'ulti!lication ,as !erfor'ed using the load cell signalinstead of the s!eed feed)ack - su!!lier 'easure'entguarantee8 " accurac.

Standard Soft,are can )e used for 0I47 S47 integration7 alar'ingand +isualiation

S!ecial Soft,are is re/uired for cali)ration

In 'ost a!!lications the cali)ration can )e !erfor'ed fro' thecentral control !anel 2no local !anel re/uired3 Cali)rationgenerall. is no longer an issue 2!erfor'ed e+er. 'onth3

Further infor'ation in Hols!ace under Engineering Ser+ices ? Co0 0rocess

Control B Electrical

5ack to Main 'enu

Cali)ration


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Cali)ration

/t is important to understand that a ;eigh feeder is onl0

as reliable as the standard to ;hich it is calibrated

The need for cali)ration can co'e fro' different sources8

An inter+al gi+en ). the !lanned 'aintenance routine 20MRs3

When readings are sus!icious 2'ainl. fro' !rocess side3

After each inter+ention 2re!air3 to a co'!onent of the feeder

0re!aration for Cali)ration8

The 'echanical installation 'ust )e free of +i)ration

0ro!er dedusting has to )e assured

If a ).!ass de+ice is installed it needs to )e free of leaks

A cali)ration task is a 'easure'ent of the res!ecti+e !ara'eters (nl. if

the difference to the last 'easure'ent is too large the ne, !ara'etersshould )e used for further o!eration 2change cali)ration !ara'eters3

#tabilit0 is therefore the most important factor

Cali)ration 4ocu'entation


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Cali)ration 4ocu'entation

E6er0 Calibration has to be properl0 documented

There are three reasons8

Re/uire'ents fro' standards 2IS( O##;3

Internal follo, u! for 'aintenance !lanning 2drift trends7 etc3

5ase for correction of !lant re!orts

The docu'entation can

)e a !age including all the

necessar. details and

stored in a res!ecti+e folder

or

it can )e a data )ase 2for se+eral feeders3

Cali)ration Methods


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Cali)ration Methods

Weigh feeders can )e cali)rated off- or on-line

(ff-line cali)ration 'ethods include8

Taring 2,eigh feeders3 or 1ero Set 2)elt ,eighers3

5elt S!eed Cali)ration 2o!tional3

Weight Check Static test ,eights Test chains

Material test 2if ,eigh out 'ethod is a!!lied3

(n-line cali)ration is8

Material test 2if loss of ,eight 'ethod is a!!lied3

Material test ,ith loss of ,eight 'ethod is the 'ost accurate cali)ration

'ethod )ecause it uses kno,n standards under actual o!erating conditions

5ack to Main 'enu

Cali)ration 6 Taring 2reco''ended for ,eigh feeder3


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Cali)ration Taring 2 eco e ded o e g eede 3

With taring the d.na'ic reference is set It is carried out ,ith an

e'!t. )ut turning )elt

If a )elt inde; indicator is used 2as in 'odern e/ui!'ents37 the

taring can )e conditional to the )elt !osition With this it allo,s for

differences in the )elt seg'ent ,eight due to8

Initial discre!ancies in the )elt ,eight ne+en ,ear of the )elt S!lices (ther influences

All this can )e then electronicall. co'!ensated The sa'e

cali)ration run 'ight also )e used for the )elt s!eed cali)ration

Cali)ration 6 Taring 2reco''ended for ,eigh feeder3


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g 2 g 3

The follo,ing !rocedure is a t.!ical e;a'!le for a co''onl. used

,eigh feeder t.!e8

The ac/uired +alue is stored as tare 4 and deducted fro' gross +alue in

nor'al 'ode 0rogra' run ti'e is set ,ith 0ara'eter P .2


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g 2 g 3

4is!la. in su)-function distri)utor

Start !rogra' Running dis!la. sho,ing residual run ti'e of !rogra'

P total ti'eQ and de+iation fro' ero !oint P/NENNQ

End dis!la. sho,ing tare correction N P/NENNQ and

the de+iation fro' !re+ious +alue P/NENNQ

Store +alue A)ort !rogra'

U4CT/%4TW: T&E

TW: ''uence

&utomatic Weigh Chec5If auto'atic ,eigh check has )een selected7 additional 'essages are dis!la.ed

Cali)ration 6 1ero Set 2reco''ended for )elt ,eigher3


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The follo,ing !rocedure is a t.!ical e;a'!le for a

co''onl. used )elt ,eigher t.!e8

The ac/uired +alue is stored as 1ero Set and deducted fro' gross +alue in

nor'al 'ode 0rogra' run ti'e is set ,ith 0ara'eter P .2


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Start !rogra' Running dis!la. sho,ing residual run ti'e of !rogra'

P total ti'eQ and de+iation fro' ero !oint P/NENNQ

End dis!la. sho,ing 1ero Set correction N P/NENNQ

and the de+iation fro' !re+ious +alue P/NENNQ

Store?acce!t correction +alue A)ort !rogra'

U4CT/%4TW: ?E% #ET

TW: ''uence


Cali)ration 6 5elt S!eed 2o!tional3


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With )elt s!eed cali)ration the dri+e and control circuit are tested It

is carried out ,ith an e'!t. )ut turning )elt

5elt Inde;Indicator

5elt Inde;

Tacho'eter

5elt S!eed Cali)ration - Ste!s


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Calculate tra+el distance of )elt for one tacho'eter i'!ulse using

the 'echanical !ara'eters

Count nu')er of tacho'eter i'!ulses for one co'!lete turn of )elt

2one i'!ulse of )elt inde; indicator3

Calculate the )elt s!eed 2distance?ti'e3

Calculate the difference )et,een theoretical7 actual7 and 'easured

length 2should not e;ceed D "#3

A )elt s!eed cali)ration can also )e carried out ). using a sto!

,atch Mark the )elt and record the ti'e for se+eral turns 2di+ide it

after,ards ). the nu')er of turns3 This 'ethod is less accurate

Cali)ration 6 Weight Check


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In the ,eight check !rocedure the s!an of the load cell is tested

and cali)rated for It is carried out ,ith the )elt sto!!ed

#teps using #tatic Test Weights

0osition different kno,n ,eights on the central ,eigh )ridge

erif. that the ,eight indicated corres!onds to the actual ,eight

Read +alues into !rogra'

Re'ark8 The ,eigh )ridge

has to )e !ro!erl. aligned

The d.na'ic of the 'o+ing )elt

is not taken into consideration,ith this 'ethod

con6erter of pointsma'< Weight$elta

WeightCal<ange#cale ×=

Cali)ration 6 Weight Check


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The follo,ing !rocedure is a t.!ical e;a'!le for a co''onl. used,eigh feeder t.!e8

0rogra' 9CW: ac/uires 'ean +alue of !latfor' load for the check,eigh a!!lied The ,eight should not e;ceed the range of $?% toJ?% of the no'inal !latfor' load

Start-u! and (!erating Conditions8

Weigher (N 2local 'ode37

olu'etric Mode7

No Material on )elt7

Check Weight 20 #$#O3 in !osition

0rogra' End8

S!an correction


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Program #e>uence:

CW:

Eprog< &5ti6<

CW:

Position P1

0rogra' start is ackno,ledged after a!!ro;i'atel. & sec Check ,eigh is not in !osition 0rogra' is not started

Re'o+e check ,eigh



Start !rogra'

Running dis!la. sho,ing residual run ti'e of !rogra' P total

ti'eQ and indicating the relation of set !oint to 'easured +alue

!on !rogra' end running 'essage sto!s at #7 the lo,er line

sho,s the s!an correction


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5ack to Main 'enu

Using Test Chains

The +er. sa'e !rocedure as ,ith the test ,eights a!!lies

The difference is that8

Chains are used instead of the test ,eights

It is carried out ,ith a running and e'!t. )elt7 therefore the

d.na'ic of the 'o+ing )elt is not taken into consideration

,ith this 'ethod

Accurac. is lo,er than ,ith test ,eights

This method is old fashioned

and should no longer be applied

Cali)ration ). Material Tests


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Material test is the most accurate calibration method because

it uses 5no;n standards under actual operating conditions

In the 'aterial test cali)ration 'ethods7 a kno,n ,eight of 'aterial

is transferred through the 'achine and co'!ared to the total

'easured ). the integrator The cali)ration !ara'eters in the

integrator are then ad*usted to co'!ensate for an. difference



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Consideration to )e 'ade

5efore an. cali)ration ). 'aterial tests is to )e carried out7 the )elt

has to )e tarred !ro!erl. 2see nit )efore37 or it has to )e assu'ed

that the tarring did not change since the last ti'e this check ,as

!erfor'ed====

It is i'!ortant to note that all of the 5no;n ;eight of material

should pass through the ;eigh feeder So'eti'es the test'aterials can fall fro' the ,eigh feeder or )eco'e stuck in the )in

or in-feed section

This ;ill alter the calibration



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The kno,n ,eight of 'aterial can )e o)tained ). t,o 'ethods8

Weigh out 'ethod (ff-line cali)ration Material can )e ,eighed )efore or after the test

@oss of ,eight 'ethod

(n-line cali)ration Test load in a )in su!!orted ). load cells

/t is critical that the ;eighing de6ice used for the test

load be accurate and calibrated to a reliable standard

Weigh out 'ethod


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The 'aterial is di+erted to a !lace ,here it can )e

,eight or a s!ecific a'ount of 'aterial is fed to the

,eigh feeder The a'ount of 'aterial is then co'!ared

to the flo, totalier of the ,eigh feeder

Most of the ti'e it is taken out of the circuit ). either a

di+erter chute or a re+ersi)le )elt and then loaded ontotrucks that are ,eight on a near). scale

The disad+antage is the additional effort for 'aterial

handling and ,eighing A critical !oint in the !rocedure is the start and sto!

se/uence of the cali)ration

@oss of Weight Method


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The a'ount of 'aterial flo,ing out of a )in 2,ithout

further feed3 is co'!ared to the flo, totalier of the

,eigh feeder during the sa'e !eriod

This is the onl. on-line cali)ration 'ethod

It includes all !ossi)le errors throughout the 'easuring

chain



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Follo,ing !arts of the ,eigh feeder ,ill )e used

Control

Module

5elt s!eed

Material B

5elt Weight

Motor @oss of Weight

@oad Cell

Shut off gate

Control

Module

5elt s!eed

Material B

5elt Weight

Motor @oss of Weight

@oad Cell

Shut off gate



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Ste! ). ste! !rocedure

The longer the calibration runsDthe more accurate it ;ill be

5ack to Main 'enu

Man< or autom< corr<

#hut off gate close

Control

Module

Control

Module

Weigh eeder running

Material

>uantit0 in

#ilo %uired

Maintenance


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The !roduction !erson in the !lant is the first line of defense against

)reakdo,ns7 since he is around the e/ui!'ent all da. and therefore kno,s it

)est He re!orts deficiencies using the !ro!er channel and tools

2notifications3 A check sheet ,ith the i'!ortant !oints to look at and thedescri!tion of the correct state is 'aking his ,ork easier

To assure relia)ilit. of the ,eigh feeder regular !laned 'aintenance tasks

20MR>s3 are to )e carried out These routines are descri)ed in the

'aintenance schedule There are different sources for the ela)oration8

Manufacturers reco''endation E;!erience fro' the !lant !ersonnel Failure Mode and Effect Anal.sis 2FMEA3 stud.

The )est structured a!!roach is using the FMEA 'ethod

Finall. there is the correcti+e 'aintenance carried out ). the res!ecti+e

s!ecialists

0MR>s - Mini'u' Guidelines


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5ack to Main 'enu

Check the ,eigh)ridge ,eekl. and re'o+e an. 'aterial )uildu! that couldinfluence the deflection of the scale

erif. dail. that the )elt is tracking !ro!erl. and that a!!ro!riate )elt tension is

'aintained

0erfor' a ero cali)ration ,eekl. 2i'!ortant ,eigh feeders37 or at least 'onthl.

Conduct a s!an cali)ration check once each 'onth during initial o!erationsThis inter+al can )e lengthened if7 o+er ti'e7 there is little de+iation )et,eenroutine s!an cali)rations

Ins!ect7 clean7 and a!!l. lu)ricants as needed to the chain7 s!rockets7)earings7 and dri+e asse')lies

Follo, the 'anufacturers reco''endations for 'aintaining the gear reducerand 'otor

0erfor' e;tra or s!ecific 'aintenance re/uired ). e;traordinar. cli'atic oren+iron'ental conditions

Check dail. for 'aterial lodged )et,een the skirting and )elt

Ad*ust'ent of Idlers

+ 1 mm


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Idlers around ,eigh )ridge are to )e aligned !ro!erl.8

A)out " '' a)o+e the rest of the idlers?!ulle.

For'ing a straight line ,ithin the'sel+es

Ad*usting5olts

+ 1 mm

E;a'!le of Chart of Align'ent Mistakes


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4ifferences in straight align'ent of idlers lead to 'istakes

in the ,eight 'easured 2E;a'!le fro' a s!ecific ,eigh feeder 'odel3

:.

Throughput

tBh

$iff< in Weight7=8

&lignment Mista5e . mm

&lignment Mista5e F.


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Weight feeder )elt training consist firstl. of eli'inating the rootcause of the !ro)le'

The second ste! is a !ro!er ad*ust'ent of the ,eight feederco'!onents to ensure the correct tracking

0ossi)le root causes are8

S!lice is not s/uare to the )elt Structure is not accuratel. aligned Idlers and !ulle.s are not aligned in all three a;es Material )uild-u! alters the !rofile of idlers or !ulle.s Friction forces are not s.''etric to centre I'!ro!er ,orking condition of aligning idlers 4eflection of !ulle.s

@oad is not centered 2root cause is then related to chute design3

Training of the )elt

A i ht f d h t d i idl d


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5ack to Main 'enu

As ,eight feeders are short7 and carr.ing idlers and

head !ulle.s are nor'all. not ad*usta)le7 )elt training

'ostl. consists of aligning the tail !ulle. Align in s'allste!s and ,ait for reaction of )elt

The )elt is tensioned on the side

it has the tendenc. to 'o+e outor

Res!ecti+el. un-tensioned on the side

it has the tendenc. to 'o+e in,ard

&fter each training of the belt the;eigh feeder has to be calibrated

Changing the )elt

Th ) lt f th i h f d ll li d t


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The )elts for the ,eigh feeders are nor'all. su!!lied to

a s!ecific length7 and in certain cases endless

The se/uence for changing a non endless )elt is8

Cut the old )elt 0ull the ne, )elt in Make the s!lice

Tension ade/uatel.

&fter each change of a belt the;eigh feeder has to be calibrated

Changing the )elt

The se/ ence for changing an endless )elt is


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5ack to Main 'enu

The se/uence for changing an endless )elt is8

Cut the old )elt out @oosen the tensioning s.ste' The u!!er !arts of the s.ste' ha+e to )e su!!orted Re'o+e all co'!onents situated )et,een the )elt to! and

)otto' on one side Shift the )elt in !osition

0lace )ack all co'!onents in the original !osition Tension ade/uatel.

&fter each change of a belt the;eigh feeder has to be calibrated

S!licing of the )elt - Methods

The follo,ing 'ethods for )elt s!licing e;ist8


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The follo,ing 'ethods for )elt s!licing e;ist8

Hot +ulcaniation is nor'all. not re/uired as the )elt

tension is lo,

Mechanical fastener are to )e strictl. a+oided

Cold +ulcanisation is the !referred solution

it is highl. cost-effecti+e and fast 2half e;!ensi+e and ti'econsu'ing than hot s!licing3

Cold ulcanisation +s Endless 5elt

Cold +ulcanisation is the !referred solution in co'!etition


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Cold +ulcanisation is the !referred solution7 in co'!etition

,ith endless )elts ,hich are alread. s!liced

The 'ost econo'ical solution according to the localcircu'stances shall )e a!!lied Factors to )e considered

are8

- 5elt costs 2higher for endless )elt3

- Cost of e/ui!'ent do,nti'e 2and re/uired a+aila)ilit.3

- @a)or for installation

&fter the ne; belt is in the ;eighfeeder has to be calibrated

Method 4escri!tion

9Cold ulcanisation: is a gluing 'ethod ,ith li/uid cold +ulcanisers or cold


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5ack to Main 'enu

Cold ulcanisation is a gluing 'ethod7 ,ith li/uid cold +ulcanisers7 or coldglues

It is *ointing the +ulcanised or gelatinised ru))er or 0C7 ,ith the )elt 'aterial

and fa)ric surfaces

Cold +ulcanisation !laces high de'ands on the /ualit. of the +ulcanisation'aterials and the skills of the !ersonnel

Cold +ulcanising fluids contain sol+ents ,hich 'ust )e ,ell +ented !rior to *ointing the gluing surfaces

The )elt 'ust )e longer than the final length needed 5oth ends are cut in diagonal and la.ers are re'o+ed to assure o+erla!!ing

of the )elt ,e)

Gluing and !ressing assure cohesion 2,aiting ti'e is at least J hours3de!ending on te'!erature and glue characteristic

The s!licing 'ust )e of high /ualit.7 ,ith no change of the )elt thickness in

the s!liced area

Trou)leshooting

Possible ;a0s of identif0ing the reason for a


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Possible ;a0s of identif0ing the reason for a

brea5do;n:

5. Con*ecture

5. S.ste'atic Testing of all the Co'!onents

5. Tracing 5ack the 4efect

GTracing bac5G is the recommended strateg0

/t is the method used b0 e'perts

Con*ecture

This is the strateg. of TRIA@ and ERR(R


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This is the strateg. of TRIA@ and ERR(R

In so'e cases7 con*ecture 'a. ra!idl. re+eal the cause

of a !ro)le'

5ut generall. this is a relati+el. unrelia)le a!!roach to

locate a )reakdo,n in a rather co'!le; 'achine

S.ste'atic Testing of all Co'!onents

Testing e+er. co'!onent in turn until .ou locate a defecti+e one is


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Testing e+er. co'!onent in turn until .ou locate a defecti+e one is

another !ossi)le strateg. for an e;!erienced user

This is a strateg. that can surel. lead to the result )ut it 'ight )e+er. slo, 2and therefore costl.3=


This is a 'ore effecti+e strateg. used ). !rofessionals to trace the source of


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-st ule: Find the co'!onent u!-strea' ,hich doesn>t o!erate

,ithin the nor'al range of !ara'eters and follo, its trace

2nd ule: Find the co'!onent l.ing u!-line ,hich o!erates ,ithin

the nor'al range of !ara'eters and e;clude in+estigation of,hat lies u!-strea' of this co'!onent

the )reakdo,n )ased on the s.'!to'

Ho,e+er this strateg. is not eas. as it re/uires a kno,ledge of the ,a. each

co'!onent o!erates and the interactions )et,een the different co'!onents

9Tracing 9ac5: is the reco''ended strateg. for this t.!e of !ro)le' sol+ing

/t is the MET%$ U#E$ 9H EIPET#

Here are the t,o rules to 9trace )ack: effecti+el.8


There is another reco''endation to follo, for finding the correct channel ra!idl.


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L%W ( %@

WE/1T #PEE$

Since the ,eigh feeder is a de+ice regulating the F@(W The s.'!to' of the

)reakdo,n generall. a!!ears ,hen reading the flo, indication

Follo,ing the logic of the s.ste'7 the channel 'a. either )e8

The ,eight or

The s!eed

That 'a. )e +isualied like a tree=

The !ro)le' 'a. co'e fro'

- an incorrect WEIGHT or

- an incorrect S0EE4

What e;actl. do ,e 'ean ). 9incorrect:


An incorrect signal 'a. )e a result of8


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A 5ad trans'ission of a signal

The cause of ,hich 'a. )e8 the 'easure'ent of the signal

the routing of the signal

the signal assess'ent

the dis!la. of the 'easured +alue

5 Incorrect 'easure'ent of a !h.sical +alue or of the !heno'enon itself

@et us e;a'ine ,hat this 'eansK

In the case of the flo, of a ,eigh feeder7 there are t,o !ossi)le

f i t i l

Trou)leshooting


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cause of an incorrect signal8

The actual flo, of 'aterial7 or the

indicator out!ut signal is incorrect

L%W

(ut!ut

signal at

the flo,

indicator

Actual

flo, of

'aterial

This can )e for'ulated in rule no%

Trou)leshooting


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In this ,a.7 .ou can i''ediatel. eli'inate fro' the in+estigations7 either8

the origin 2!h.sical +alue7 for e;a'!le the s!eed7 )elt load7 etc3 or

the connections )et,een the origin and the out!ut signal 2the ca)les7 theco'!onents7 either of transfor'ation or of signal trans'ission3

With the hel! of the %rd rule7 the tree diagra' of causes can )e e;tended Ifthe indicated WEIGHT is a)nor'al the cause 'a. )e8

at the origin8 a !ro)le' in the 'aterial flo,7 or in the connections8 the difference )et,een the actual load of the )elt and

the indicated load could )e due to8

- the 'easuring circuit of the ,eight

- the 'echanical construction of the ,eigh feeder

3rd ule: If a signal is incorrect7 first check the !h.sical +alue

that is at the origin of the 'easure'ent strea'

Trou)leshooting

Where could the cause of )reakdo,n )e located if the #PEE$ indication

i i t l


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L%W ( %@

WE/1T #PEE$

Material Flo,

Mechanical Construction

Weight Measure'ent Circuit

Motor S!eedMechanical Connection


gi+es an incorrect +alue

" At the origin8 'otor s!eed incorrect7 or

$ In the connections8 the difference )et,een the actual 'otor s!eed and the

s!eed indicated results fro' a !ro)le' in8

- the s!eed 'easuring circuit7 or - the 'echanical connection )et,een the 'otor and tacho'eter

The treediagram of causes no; appears as follo;s:

Trou)leshooting

With the tree-diagra' of causes in 'ind7 .ou can ra!idl. locate the circuit ,ere the

!ro)le' lies


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5ack to Main 'enu

!ro)le' lies

The treediagram of causes

To identif. the defecti+e co'!onent7 all .ou ha+e to do is a!!l. the three rules in

the res!ecti+e circuit

L%W ( %@

WE/1T #PEE$

Material Flo,

Mechanical Construction

Weight Measure'ent Circuit

Motor S!eed

Mechanical Connection


Set 0oint Increase 6 S.ste' Reaction 2"?$3

The lo; Controller records a deficit )et,een the 'easured flo,

and the re/uired flo,


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and the re/uired flo,

The Flo, Controller trans'its a signal to the Monitoring Module

of the $ri6ing Motor to increase the 'otor s!eed

The th.ristor card increases the induced +oltage and the Motor

)egins to accelerate

The increase of 'otor s!eed 'akes the )elt rotates faster7

e;tracting 'ore 'aterial fro' the ho!!er thus increasing the flo,

The increase of 'otor s!eed also corres!onds to an increase of

the out!ut +oltage of the Tachometer and of the &mpere Meter

The out!ut +oltage of the tacho'eter is a'!lified ). the &mplifier

and the ne, )elt s!eed is dis!la.ed ). the #peed Monitoring

Set 0oint Increase 6 S.ste' Reaction 2$?$3

The &mplifier is infor'ed of the s!eed increase The )elt load7relati+el. unchanged is then 'ulti!lied ). the ne, )elt s!eed to


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relati+el. unchanged7 is then 'ulti!lied ). the ne, )elt s!eed togi+e the ne, flo,

The 'easured flo, is co'!ared ,ith the set !oint If there is nodifference7 the 'otor sto!s accelerating and the )elt s!eedsta)ilies at the flo, set !oint

At all ti'es7 the 'easured flo, is dis!la.ed ). the #peed /ndicator and the /uantit. of the trans!orted 'aterial is accu'ulated ). the

Totalier 7 +ia the /ntegrator As soon as the )elt s!eed has sta)ilied to the ne, flo,7 the

dis!la.ed flo, and the set !oint are identical This 'arks the end ofan ad*ust'ent c.cle ,hich has !er'itted a flo, increase

An. ne, 'odification of the set !oint ). the o!erator ,ill start thead*ust'ent !rocess again A reduction of the set !oint ,ill o)+iousl.lead to a reduction of the flo,

weigh feeder training module

Documents