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Manufacturing Workforce Training
HGRS MASTER - MAINTENANCE
Training Module: Weigh Feeders
Presentation: Weigh Feeder Training Module!!t
Version: "#
Last Update: $%-#%-#%
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()*ecti+e
Weigh Feeder is intended to )e a co'!rehensi+etraining 'aterial for all technical staff ,ithin Holci'
Grou! co'!anies
It ,ill fa'iliarie .ou ,ith the general kno,ledge as
,ell as ,ith the 'aintenance re/uire'ents
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Weighfeeder Weighfeeder
Electrical componentsElectrical components
Calibration unctionCalibration unction
TroubleshootingTroubleshooting
Function (!erating 0rinci!le
Taring and 1ero Setting
Weight Check Cali)ration 2Test Weights3
(+er+ie,
Weigh Measuring Circuit
Flo, Control Circuit
4ri+ing Motor Circuit
Material Flo,
Mechanical Co'!onents
Tracing 5ack the 4efect
Material test
MaintenanceMaintenance Maintenance
Content of 0resentation
Mechanical componentsMechanical components
Set 0oint Increase 6 S.ste' Reaction
Changing of 5elt
5elt S!licing
Training of 5elt
S!eed Measuring Circuit
Cali)ration
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5ack to Main 'enu
Function of a Weigh Feeder
Weigh feeders are designed to deli+er a designated rate of 'aterial
in a !rocess The. are used to con+e.7 ,eigh7 and control the flo,
rate of )ulk 'aterials ). +ar.ing the s!eed of the )elt
The. transfor' a +aria)le 'aterial flo, into a constant and
controlla)le flo,
A su)-function of a ,eigh feeder is to reduce the !ossi)ilit. of
s!illages7 leakages7 and dust e'issions
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The s!eed and load of the )eltand 'aterial deter'ines the flo,
5asic For'ula8
#PEE$ 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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5ack to Main 'enu
(!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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5ack to Main 'enu
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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5ack to Main 'enu
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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S!eed Measuring Circuit
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
The circuit consists of:
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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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
The circuit consists of:
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
The circuit consists of:
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
Co''and Module of the Motor
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Co''and Module of the Motor
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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Weigh Feeder Control ,ith 0CS
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 Feeder Control ,ith 0CS
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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Weigh Feeder Training Module!!tHolci' Grou! Su!!ort Weigh Feeder
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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Weigh Feeder Training Module!!tHolci' Grou! Su!!ort Weigh Feeder
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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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 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
&utomatic Weigh Chec5If auto'atic ,eigh check has )een selected7 additional 'essages are dis!la.ed
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
&utomatic Weigh Chec5If auto'atic ,eigh check has )een selected7 additional 'essages are dis!la.ed
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 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
Cali)ration ). Material Tests
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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
Cali)ration ). Material Tests
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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
@oss of Weight Method
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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
@oss of Weight Method
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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=
Tracing 5ack the 4efect
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
Tracing 5ack the 4efect
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:
Tracing 5ack the 4efect
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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Weigh Feeder Training Module!!tHolci' Grou! Su!!ort Weigh Feeder
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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Weigh Feeder Training Module!!tHolci' Grou! Su!!ort Weigh Feeder
L%W ( %@
WE/1T #PEE$
Material Flo,
Mechanical Construction
Weight Measure'ent Circuit
Motor S!eedMechanical Connection
S!eed Measuring Circuit
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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Weigh Feeder Training Module!!tHolci' Grou! Su!!ort Weigh Feeder
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
S!eed Measuring Circuit
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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Weigh Feeder Training Module!!tHolci' Grou! Su!!ort Weigh Feeder
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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Weigh Feeder Training Module!!tHolci' Grou! Su!!ort Weigh Feeder
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,
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