Cleaning, Sorting and Grading Devices.pdf

Comprehensive and easy to understand concepts of food process engineering regarding cleaning, sorting and grading of food particles.

1. LECTURE 3 & 4
CLEANING, SORTING AND
GRADING DEVICES

2. Cleaning, Sorting & Grading
Cleaning
•Afterthreshing,grainsarecontaminatedbyimpurities(earth,small
pebbles,plantandinsectwaste,seedcases,etc.).
•Theseimpuritieshinderdryingoperationsandmakethemlonger
andmorecostly.
•Afterdrying,especiallybytraditionalmethodssuchasopen-air
drying,thegrainmaystillbecontaminatedbyimpurities.
•Theseimpuritieslowerthequalityoftheproductandalsocause
potentialinfestationduringstorage.
•"Cleaning"meansthephaseorphasesofthepost-harvestsystem
duringwhichtheimpuritiesmixedwiththegrainmassare
eliminated.
•Thecleaningmaybedonebywashing,screening,handpickingetc.

3. Cleaning, Sorting & Grading (contd.)
Sorting
•Sortingisdonemostlybyhandtoremovethefruitsand
vegetableswhichareunsuitabletomarketorstoragedueto
damagebymechanicalinjuries,insects,diseases,immature,
over-mature,misshapenetc.
•Thisisusuallycarriedoutmanuallyanddonebefore
washing.
•Byremovingdamagedproducefromthehealthyones,it
reduceslossesbypreventingsecondarycontamination.
•Sortingisdoneeitheratfarmlevelorinthepack-houses.In
sorting,onlysensoryqualityparametersaretakeninto
consideration.

4. Cleaning, Sorting & Grading (contd.)
Grading
•Theproduceisseparatedintotwoormoregradesonthebasisof
thesurfacecolor,shape,size,weight,soundness,firmness,
cleanliness,maturity&freefromforeignmatter/diseasesinsect
damage/mechanicalinjury.
•Aclassificationofthematerialonthebasisofcommercialvalue
andusage.
•e.g.AppleI.ExtraFancyII.FancyIII.StandardIV.Cull(for
processing).
•Gradingmaybedonemanuallyormechanically.Itconsistsof
sortingproductingradesorcategoriesbasedonweight/size.

5. Grade Factors
Grade factors are characterized by following
characteristics:
1.Physical
2.Biological
3.Chemical etc.
1. Physical Characteristics
i.Moisture Content
ii.Unit size
iii.Texture
iv.Color
v.Foreign matter
vi.Shape

6. Grade Factors (Contd.)
2. Chemical Characteristics
i.Analysis (Composition)
ii.Rancidity (refers to the spoilage), free fatty acid index
iii.Odor and flavor
3. Biological Characteristics
i.Germinations
ii.Type and amount of insect damage
iii.Type and amount of mold damage
iv.Bacteria count

7. Washing of Agricultural Produce
Theprimaryoperationofcleaningiswashing.It
hasfollowingtypes
1)Soakinginstillorinmovingwaterofotherfluids
2)Watersprayers
3)Rotarydrums
4)Rotatingbrushes
5)Shuffleorshakerwashers

8. Washing of Agricultural Produce
(Contd.)
1. Soaking
Adopted for loosely attached dirt particles and are in
small quantities.
2. Water Sprays
a)Itconsistsoflowpressuretoveryhighpressure
waterjetsdirectedatwideangles.
b)Itremovesfirmlyattachedparticlesdueto
agitationwhenplacedinwaterbath.
c)Theintensityofsprayorpressureshouldbe
carefullyadopted.

9. Washing of Agricultural Produce
(Contd.)
Soaking and Water Sprays

10. Washing of Agricultural Produce
(Contd.)
3.RotaryDrum
a)Commercialwashingdevice.
b)Minimumdamage,simple,highcapacitywashes.
c)Theperformancedependonspeedofrotation,theroughnessand
lengthoftimetheproductisretainedinwater.
d)Auxiliaryaidssuchasspraynozzlesmayfacilitatethejob.
e)Thewashingtimeiscontrolledbythepitchofthedrumor
helicalretainingfenceswhichscrewtheproductthroughthe
drum.

11. Washing of Agricultural Produce
(Contd.)
Rotary Drum Washer

12. Washing of Agricultural Produce
(Contd.)
4.BrushWashers
a)Effectiveforsandyorloamysoilspray
residues.
b)Washingtimecontrolledbyrotatingmotionof
brusheswhichmovestheproductthrougha
definitepath.
c)Brushesmadeoffiber,rubber,sponge,other
materialwhichmaybereplacedfrequently.

13. Washing of Agricultural Produce
(Contd.)
Brush Washers

14. Washing of Agricultural Produce
(Contd.)
5.ShakerWashers
a)Usedfordifficultwashingjobs.
b)Avigorousreciprocatingmotionisinvolvedso
itismaderobust.
c)Moreexpensivebuteffectiveandsometime
unsuitableforproductthatareeasilymanaged.

15. Sorting of Agricultural Produce
They can be sort out by the following procedures
i.Screening
ii.Diverging belts
iii.Roller sorter
iv.Weight sorter

16. Sorting of Agricultural Produce
(Contd.)
1. Screening
a)Vibratingscreensareusedforfruitsandvegetables
whicharemadeofcoper,stainlesssteelorother
materialswhicharenotchemicallyactive.
b)Theun-sizedmaterialpassesonavibratingscreenor
rotating,whichperforatestopass.
c)Thelargestmaterialwhichgoesovertheendofscreen.
d)Thematerialthatpassesthescreenisrescreenedand
intonewfractionsaremovedtotheotheroperations.

17. Sorting of Agricultural Produce
(Contd.)
Screen Sorter

18. Sorting of Agricultural Produce
(Contd.)
2.DivergingBelts
a)Widelyusedsorter,consistsoftwoormore
beltswhichdivergeastheytravel.
b)Thefruitiscarriedonandbetweenthebelts.
c)Sincethedistancebetweenthebeltsincreases
symmetrically,thesmallerpieceswilldrop
betweenthebeltsatthebeginningoftravel
whereasthelargerpieceswilldropfarther.

19. Sorting of Agricultural Produce
(Contd.)
Belt Sorters

20. Sorting of Agricultural Produce
(Contd.)
3.RollerSorters
a)Rollersortersarefast,accurateandcauselittledamageto
product.
b)Eachrollrotatesinacounter-clockwisedirection.
c)Thefruitiscontentiouslyrotatedsothatindividualpiece
hasanopportunitytoresisteritsminimumdimensionwith
thespaceinthesorter.
d)Therollersorterisdividedintomultiplerollunits,which
arehingedsothatthegaugingspaceincreasesprogressively
throughthesorter.
e)Whentherollerunitclosesthespaceattheendofitstravel
theturningrollerejectsanyfruittryingtopassthroughthe
spacewithoutdamage.

21. Sorting of Agricultural Produce
(Contd.)
3.RollerSorters(Contd.)
f)Rollerconveyerswithfixedspaceareusedforremoving
theleavesandtwigsandsmallfruits.
g)Therollersizerwhichgangsonminimumdiameteronly
workswellonobjectsofuniformgeometricproportions.
h)Ifproportioninalotvary,agivensizegradewillcontaina
greaterrangeofvolumesthanisdefinedbytheminimum
diameters.
i)Asetofrollswithaprofiledefinedbyspoolshasbeen
designedforgradeswhichgiveanimpressionofrelatively
uniformsizewithinagrade,evenwithfruitsofdifferent
proportions.

22. Sorting of Agricultural Produce
(Contd.)
Roller Sorters

23. Sorting of Agricultural Produce
(Contd.)
4.WEIGHTSORTERS
a)Theyoperateonthebasisofunitweightandareaccurate,
moderatelyfastanddamagetoproductisminimum.
b)Theycanbeusedonlargesizeproductsasapples,oranges,and
arealsoadoptedforeggshandling.
c)Thematerialisplacedintoindividualcupsbyanautomatic
indexingfees.
d)Asthecuptravelthroughthesorter,theyareindexedwithspring
loadedtrips.Thespringtensionisprogressivelyweakerfromthe
beginningtotheendofmovement.
e)Theheavierunitsovercomethespringreactionandare
dischargedatthebeginningoftravel.Thelighterunitsmoving
thegreaterdistancebeforebeingdischarged.

24. Sorting of Agricultural Produce
(Contd.)
Weight Sorters

25. Cleaning and Sorting of grains, nuts
and seeds
It depends upon the following characteristics of
materials
i.Size
ii.Shape
iii.Specific gravity
iv.Surface characteristics
It can be done by
i.Winnowing
ii.Screening

26. Cleaning and Sorting of grains, nuts
and seeds (Contd.)
1. Winnowing
a)Winnowingisatraditionalagriculturalmethoddeveloped
byancientculturesforseparatinggrainfromchaff.
b)Itcanalsobeusedtoremovepestsfromstoredgrain.
Winnowingusuallyfollowsthreshingingrainpreparation.
c)Initssimplestformitinvolvesthrowingthemixtureinto
theairsothatthewindblowsawaythelighterchaff,while
theheaviergrainsfallbackdownforrecovery.
d)Techniquesincludedusingawinnowingfan(ashaped
basketshakentoraisethechaff)orusingatool(a
winnowingforkorshovel)onapileofharvestedgrain.

27. Cleaning and Sorting of grains, nuts
and seeds (Contd.)
Winnowing

28. Cleaning and Sorting of grains, nuts
and seeds (Contd.)
2.Screening
a)Mostwidelyuseddeviceforgrains/seedsetc.isscreenor
sieve.
b)Sievesusedinconjunctionofairblastwillsatisfactory
cleanandsortmostgranularmaterials.
c)Thescreenunitiscomposedoftwoormorescreens
d)Thesescreensaresuspendedbyhangersinsuchawaythat
theyhaveahorizontaloscillatingmotionandasmaller
verticalmotion
e)Thecombinationofthesetwomotionsmovethegrain
downthescreenandatthesametimetossesitsufficiently
sothatthesheetofgrainisthoroughlystirred.

29. Cleaning and Sorting of grains, nuts
and seeds (Contd.)
Basic screen arrangement for sorting of grain

30. Cleaning and Sorting of grains, nuts
and seeds (Contd.)
Dual Screen Grain Cleaner/Sorter

31. Cleaning and Sorting of grains, nuts
and seeds (Contd.)
Dual Screen Grain Cleaner/Sorter

32. Cleaning and Sorting of grains, nuts
and seeds (Contd.)
This Slide
Contain
video of
Drum
Washer
-
Click and
PLAY

33. Cleaning and Sorting of grains, nuts
and seeds (Contd.)
2.Screening(Contd.)
f)Thescreenpitchisadjustablethiscontrolsthe
downwardtravelofthegrain.
g)Screensareavailablewithround,triangularor
slattedholes.Theslotsmaybeorientedinthe
directionoftravelperpendiculartoitorboth.
h)Performancedependsonscreenselectionand
pitchasasteeppitchworksbetter.
i)Thematerialshouldnotmoresofastthattheseis
insufficienttimeforeachindividualgrainto
registerwithahole.

34. Cleaning and Sorting of grains, nuts
and seeds (Contd.)
2.Screening(Contd.)
j)ThesieveAiscalledthescalperandisforscalpingoff
materiallargethanthattoberetained.
k)Generally,screenAshouldhaveroundholesthat
shouldbejustlargeenoughtopassthematerialtobe
retained.Butifthematerialisflatthanoblonghole
screenisrecommended.
l)ThescreenBshouldhaveholesjustsmallenoughto
retainthebestmaterial.IfthescreenAhasroundholes
thenlowerscreenshouldhaveslottedholesorVice
Versa.
m)FrequentlyscreenCisomittedthelightseedsandweed
seedsbeingpermittedtofallontothesolidPanD.

35. Cleaning and Sorting of grains, nuts
and seeds (Contd.)
2.Screening(Contd.)
n)Ontheotherhandifitismixtureofmaterialandistobe
sortedthenaremoreadditionalscreensarerequired.
o)Inthisarrangementthematerialisnotcontaminatedwith
thesmallfractionsrejectedbyD.
p)Thepitchofthelowerbankofscreencanbecarriedrelative
totheupperbankandalsothevibratingcharacteristicscan
bevariedbetweenthetwosetstoaccommodatethejobat
hand.
q)Whenafinedegreeofsoringisbeingmadegrainswill
frequentlylodgeintheholes.Soscreensarefittedwith
movingbrushesbeneathandpushesthelodgedseedsback
throughthescreen.

36. Aerodynamics of Small Particles
•Undesirablematerialssuchaslightgrains,weedseeds,
chaff,plantleavesandstalkscanberemovedwithairflow,
whengrains,fruitsandvegetablesaremechanically
harvested.
•Inaddition,agriculturalmaterialsareroutinelyconveyed
usingairstreaminpneumaticconveyers.Ifthesesystems
arenotusedproperly,theycouldcauseproblems.
•Forexample,inacombineharvester,iftheairspeedislow,
thematerialswouldnotbeseparatedfromeachotherand
therewillbeextraforeignmaterialwiththeproduct.
•Ifairspeedishigh,theproductwillbeexhaustedalongwith
extramaterialandproductlosswillincrease.

37. Aerodynamics of Small Particles
(Contd.)
•Forconveyingagriculturalmaterial,therangeof
properairstreamsshouldbeused.
•Withlowairspeed,thereisstagnationinthe
system,orwithhighairspeed,thereisnotonly
energylost,butalsograinsmaybebroken.
•Theproperairspeedcanbedeterminedfrom
aerodynamicpropertiesofagriculturalmaterials.
•Thesepropertiesareterminalvelocityanddrag
coefficient.

38. Aerodynamics of Small Particles
(Contd.)
•Ifanobjectisdroppedfromasufficientheight,theforceofgravitywillaccelerate
ituntilthedragforceexertedbytheair,balancesthegravitationalforce.Itwillthen
fallataconstantvelocitycalledtheterminalvelocity.
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1
2
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2
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•The drag coefficient of an object can be found from its terminal velocity:
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2????????????
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2
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Where:
m=ismassoftheobject(kg),
g=isgravitationalacceleration(m/s
2
),
C
d=isdragcoefficient,
ρ=isairdensity(kg/m
3
),
A=isprojectedarea(m
2
),and
V
t=isterminalvelocity(m/s).