Cleaning grading & conveying

Cleaning, Grading and Conveying
By: Dr. (Mrs.) Seema Tanwar

CLEANING
• Cleaning in agricultural processing generally
means that removal of foreign and undesirable
matters from the desired grains/products.

• Cleaning can be done in two ways:-
i) Wet
ii) Dry
Principles of cleaning seeds
• Dimensional - width, thickness and length,
• Shape of particles,
• Aerodynamic (Terminal velocity)
• Surface texture,
• Frictional coefficients,
• Specific gravity-density,
• Affinity for liquid,
• Ferromagnetic,
• Electrical conductivity and
• Color-reflectivity

Method of cleaning Seeds:
Cleaning of the seeds can be conveniently discussed in the
following groups:
1. Preparing seeds for basics seed cleaning (pre-conditioning
and pre-cleaning operations )
2. Basics seed cleaning operation
3. Upgrading the quality of cleaned seed
1. Preparing seeds for basics seed cleaning
pre-conditioning refers to operations such as shelling,
debearding etc. that prepare seed lost for basic seed cleaning;
and also to the removal of particles such as pieces of trash,
stones, clods etc., larger in size than desirable crop seed, from
threshed seed lost.

Equipment used for pre-conditioning and pre-cleaning are:-
1. Scalper
2. Debearders
3. Huller-scarifier
4. Buckhorn machine
5. Pebble mill

Scalper
Description and Application
• Scalpers are used to remove large trash, stems, leaves, and
associated chaff prior to basic cleaning. There are numerous
types, but they basically use the same style of cleaning. Raw
material is metered onto a flat screen that is set at a slight
incline and vibrated mechanically. Trash is removed as the
seed fall through the holes in the screen and onto a second
screen. This screen traps the seeds and moves them to a
hopper as smaller trash falls through the holes and is sweep
away by an air current. Another style uses a round drum made
from a perforated metal screen set at a slight incline. As the
drum rotates, seed fall through the screen and trash remaining
in the drum is removed.

Scalper
• It removes the larger inert
matter from the seeds. If it
contains a single sieve it is
called as scalpers, two
sieves – rough cleaners.
• The unit consists of a
vibrating or rotating screen
or sieve having perforation
large enough to allow the
rough seed pass through
readily.
Photo courtesy of Loren St. John, USDA NRCS, Aberdeen PMC

Debeaders
• After excessive trash has been removed by scalping,
debearders are used to remove awns or beards and other
appendages from seed that are difficult to clean with air-screen
separators. Debearders use a beater that rotates inside a steel
cylinder. The beater uses projecting posts that are positioned
to move the seed mass through the cylinder. Stationary posts
on the steel cylinder prevent the seed mass from rotating with
the horizontal shaft and provide vigorous rubbing action
between the moving and stationary posts, other seed, and
appendages. A weighted discharge gate controls the amount of
time the seed mass remains in the unit. A debeader is a very
versatile machine that has been used successfully on many
types of seed. Its cleaning action is less aggressive than that of
a hammermill.

Debeaders
• The machine has horizontal
beater with arms rotating
inside a steel drum. When
the seeds pass through it do
the action of rubbing the
seeds and clip the seeds of
oats, debeard barley, thresh
white cap in wheat, remove
awns and beards, de hull
some grass seeds and polish
the seed.
• Capacity : 4mt/hr
• Power : 7.5kw

Huller - Scarifier
• Hullers and sacrifiers usually abrade the seeds between two
rubber-faced surfaces, or impel seeds against roughened
surfaces, such as sandpaper.
Working:
In huller-scarifier, the seeds fall from the feed hopper on to a
rotating distributing disc, where they are thrown against the
hulling and scarifying surface by centrifugal force either once
or twice, depending upon the machine. Hulling (removal of an
outer coat or husk ) and scarification (scratching of the seed
coat ) can be done separately or jointly with a huller-scarifier.

Pebble mill
• The mill is used for removing cob-webby hairs from blue grass
and similar seeds. It has a drum rotating about a shaft, inserted
off-centre at opposite ends. The mill is loaded with seeds and
smooth half-inch pebbles and turned at a slow speed until the
rubbing action of the pebbles rolls the fuzz from the seeds into
small round balls. The mixture of pebbles, seeds and matted
fuzz is then run over a scalper to remove the pebbles.

2. Basics seed cleaning operation
• Basic seed cleaning refers to actual cleaning and grading of
seeds.
• Basic seed cleaning is an essential process in the seed cleaning
operation.
• Basic seed cleaning is done over an air screen machine,
commonly referred to as an air screen cleaner.
• Air screen cleaner also the basic equipment in seed processing
plants.

Air screen machine
Principle of cleaning
The separation of undesirable material and seeds from
desirable seeds in an air screen machine is done on the basis
of different in seed size and weight. In some separations, seed
shape could also be used. The air screen machine uses three
cleaning elements : Aspiration, Scalping and Grading.
a) Aspiration: The light seeds and chaffy material is removed
from the seed mass through aspiration.
b) Scalping: In this operation, the good seeds are dropped
through screen openings, but the larger material (trash, clods
etc.) is carried over the screen into a separate spout.
c) Grading : In this operation, the good seed ride over screen
opening, while smaller particles(undersized, cut, shrivelled,
broken seeds) drop through.

Air-screen Separators
• The primary method of seed cleaning is the air-screen separator. It uses a
combination of air, gravity, and screens to separate seed based on size,
shape, and density. These widely-use units come in a variety of models
with two to eight vibrating screens. In all cases, the cleaning principles are
the same. The seed mass drops onto the top screen which scalps and
removes large trash and impurities. Seed and smaller trash pass through to
the next screen which retains the seed and allows the trash to pass
through. Multiple screens provide seed size and density separation. Air
streams remove the trash and impurities and the seed moves to bagging or
collection units. Numerous types and sizes of screen are available. The
rate of feed, airflow, oscillation of the screens, and screen pitch are
adjustable. With experience, an operator can set all the variables and
achieve excellent results.

Air-screen Separators
Photo courtesy of Loren St. John, USDA NRCS, Aberdeen PMC

Productivity of the equipment is 350-600 kg/h depending on the type of grain.
Pedal operated air screen grain cleaner

Pedal operated air screen grain cleaner
• The pedal-operated air screen grain cleaner is designed for the separation of
dust, dirt, stones, straw, chaff, broken and smaller size grains from granular
agricultural materials like foodgrains and oilseeds.
• It is a manually operated continuous machine in which separation takes
place due to the difference in size & weight of the product.
• The grains are kept in bulk in the hopper from where they drop to the top
scalping sieve by gravity, controlled by a feeding mechanism.
• Separation occurs and the cleaned & sound grains are retained over the
bottom screen and delivered outside through a spout.
• Length 1600mm. Width 500mm. Height 1000mm. Weight 100kg. Capacity
350-600kg/hr depending on grain to be handled.
• Cleaning efficiency 99.5-99.9%. Cost of cleaner Rs.2500(apprx).
• Cleaning cost/quital Rs1.00 for wheat, Rs0.60 for soyabean, Rs.0.70 for
bengal gram.
• Two persons required(one to operate & another to load & unload grains).

Parts of Air Screen Cleaner
Screen
For cleaning and separation of seeds the most widely used device.
When solid particles are dropped over a screen, the particles
smaller than the size of screen openings pass through it,
whereas larger particles are retained over the screen or sieve.
Types of screens:-
a) Rotary screen
i) Gyratory screen
ii) Circular screen
b) Vibratory screen
c) Horizontal screen

• a) Rotary screen: Rotary and gyratory screens are capable of
accurate and complete separation of very fine sizes but their
capacity is limited.
i) Gyratory screen: Singled decked machine in horizontal
plane motion, which is circular at feed end and reciprocating at
the discharge end.
ii) Circular screen : These are also rotary screens but their
motion in horizontal plane is circular over the entire surface.

b) Vibratory screen
For cleaning, grading and separation of agricultural granular
materials vibratory screen cleaners are very popular.
Function of vibratory screen:
i) Helps in providing passage to particles through openings
ii) Restrict in clogging of screen
iii) Cause stratified over screen to meet each particles to opening
iv) Continuous flow of particles along screen possible

Horizontal screen: Special case of vibrating screen.
• Design for operation with low head room.
• Operates without the aid of gravity.
Manual Double Screen Cleaner
• Operated by hanging it an
any elevated point with
four rope
• Capacity 150-225kg/h
• Weight 14 kg
• Screen size 5-8.5 mm
• Price Rs1300
• Operating cost Rs 5/q
Manual Double Screen Cleaner

Screen openings: constructed with perforated sheet metal or woven
wire mesh.
• Perforated metal screens
i) Round openings: measured by diameter(mm or in.)- Eg.
ii) Oblong openings: dimension of width listed first then the length
as 1.8 x 20 mm. Eg.paddy,
iii) Triangular openings : side of the of each of the triangle in mm.
Round holes
(caster, mustard, green gram) Oblong holes
(Pddy)
Triangular holes

Wire mesh screens:
i) Square mesh:
The square opening in wire mesh are
measured by number of opening per inch
in each direction.
 A 9x9 screen has 9 openings per inch.
ii) Rectangular mesh:
iii) openings measured in same way as square mesh.
 A 3x6 rectangular wire mesh
screen will have 3opening per inch in
one direction and 6 opening per inch in
the other direction.

Effectiveness of screen
• Effectiveness of screen: The screen effectiveness may be defined
as the ability of a screen in closely separated the feed into
overflow and underflow according to its size.
• F = mass flow rate of feed
• D = mass flow rate of overflow
• B = mass flow rate of underflow
• xF = mass fraction of material A in feed
• xD = mass fraction of material A in overflow
• xB = mass fraction of material A in underflow

BD
BF
xx
xx
F
D



DB
DF
xx
xx
F
B



F = D + B
FxF = D xD + BxB
Mass balance over screen

Screen effectiveness
• It is measure of success of a screen is closely
separating materials A and B.
• If the screen functioned perfectly, all of
material A would be in overflow and all of
material B would be in underflow.

F
D
A
Fx
Dx
E  )1(
)1(
F
B
B
xF
xB
E



Screen efficiency for A and B
,
FBBD
BDFDBF
F
B
F
D
xxxx
xxxxxx
xF
xB
xF
xD
E
)1()(
)1())((
)1(
)1(
2





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


E = EA * EB

GRADING
• Grading refers to the classification of cleaned
products into various quality fractions
depending upon the various commercial values
and other usages.

Seed grader
• The function of this machine is to clean and grade the seeds
and grains.
• Seeds and grains have lot of dirt, inert matter, reject material,
stones, dust and plant parts when it is harvested and threshed.
• Only good quality seeds can give good crop and similarly
good quality grains that can be used to produce food material
for human consumption.
• To make this possible, it uses the principle of screening and
airflow to remove the unwanted material.
• The machine is electrically powered to operate at desired
speeds while maintaining quality.

Specification:
Sample Size: 1kg. ( In case of Wheat)
Screen Area: 38x25.4 cm.
Weight / size: 39kg / 80x54x75 cm.
(approx.)
Elec. Motor : ½ HP Single Phase
Supplied with a set of 10 Screens and 2
Trays
Seed grader

Salient features:
SCALPING DECK plus two cleaning
decks to suit specific process
requirement.
Optionally 3 decks can be provided for
grading of materials as required.
Totally closed cleaner shoe with easily
replaceable sieve panels.
BALL DECKS provided for efficient
sieve cleaning.
Sturdy tubular frame construction to
support the whole cleaner unit.
Dynamically balanced eccentric drive
arrangement ensures vibration free
reciprocating motion.
FEED HOPPER with material flow
control gate.
Groundnut grader

Description/Specification :
Robust machine of all steel construction.
Dynamically balanced aspirator fan.
Feed hopper equipped with feed roller and
feed control gate.
Specially designed Rubber Balls / Nylon
Brushes to check sieve perforation clogging.
Belt guard provided Air Chamber, Sieve
Deck assembly and spouts are self cleaning
type.
Optional Accessories Available Dust
collector, Air Trunk, Surge Bin, Feeding
Elevator
Seed Grader

Indented Cylinder Separator
OPERATION
Raw material fed through the product inlet moves along the inner wall of the Indent Cylinder
towards the product outlet. Round grains, brokens, small seeds etc. that have a different shape
from the main stock get lifted by the indented pockets of the rotating cylinder and dropped
into the collecting trough. The screw inside the collection trough conveys this material
towards the outlet. The position of the collection trough can be regulated by a hand wheel for
proper separation.
APPLICATION
The Length Grader (or Indented Cylinder) is widely used for the separation of broken rice (i.e.
1/4 size, 1/2 size, 3/4 size) from full rice and long rice. Indented Cylinder Grader is also used
in Flour Mills, Seed Mills etc. for the separation of cockles and broken.
Features
Suitable for numerous grain processing applications,
•
Reliable separation through pocketed sorting cylinder,
•
Totally enclosed construction for safe operation,
•
Easy and rapid change of cylinder shell segments,
•
Safety measures as per international norms,
•
Low investment and operating costs,
•

Indented Cylinder Separator are used for length
grading of all granular materials such as wheat,
oat, maize, rice, fine, lentils,
stones from peas, sticks from sunflower
or sugar beet, plastic particles, etc.,
as well as for the extraction of unwanted
short or long admixtures.
Indented Cylinder Separator

Spiral separator
• The separator, which classifies seed according to its shape and rolling
ability, consists of sheet metal strips fitted around a central axis in the form
of a spiral.
• The unit resembles an open screw conveyor standing in a vertical position.
The seed is introduced at the top of the inner spiral.
• Round seeds roll faster down the incline than flat or irregularly shaped
seeds, which tend to slide or tumble.
• The orbit of round seed increases with speed on its flight around the axis,
until it rolls over the edge of the inner flight into the outer flight where it is
collected separately.
• The slower moving seed does not build up enough speed to escape form the
inner flight.
• Most spirals have multiple inner flights arranged one above the other to
increase the capacity.

This machine is used to separate round seeds from
other shaped seeds/parts.
E.g. separate ground from cabbage seeds, round
from sharp spinach seed and cleavers and very flat
seeds from radish.
The following weeds are removed from cabbage:
sine’s grass, triangular shaped seeds, black bind-
weed and sorrel.
SPIRAL SEED SEPARATORS

The winnower is used to utilise the
differences in specific weight between
the seeds and other parts.
A rough air separation separates the
seeds from the husks.
It is very suitable for cleaning small
seed lots
winnower

Specific gravity separation
• This method makes use of a combination of weight and surface
characteristics of the seed to be separated.
• The principle of floatation is employed here.
• A mixture of seeds is fed onto the lower end of a sloping perforated table.
Air is forced up through the porous deck surface and the bed of seeds by a
fan, which stratifies the seeds in layers according to density with the
lightest seeds and particles of inert matter at the top and the heaviest at the
bottom.
• An oscillating movement of the table causes the seeds to move at different
rates across the deck.
• The lightest seeds float down under gravity and are discharged at the lower
end, while the heaviest ones are kicked up the slope by contact with the
oscillating deck and are discharged at the upper end.
• This machine separates seeds of the same density but of different size and
seeds of the same size but of different densities.

Technical Specifications
Capacity : 100 Kg./Hr. (based on
wheat) and depending upon the
grading quality to be achieved
No. of Fans : One
Size of Deck : 855 x 550mm (W x L)
Electric Drive : 1.0 HP for Fan 0.5 HP
for Deck for manual speed control
0.25 HP fo DC drive for electronic
control
Specific gravity separator

This seed density separation unit is used for
accurate seed density grading using liquids (water
or liquids with certain osmotic pressures).
During separation the seeds should keep the same
moisture level content.
DENSITY SEPARATORS

Stone Separators
Capacity : 2 TPH
Power : 1/2 HP
Salient Features :
Silent and smooth operation.
Feed hopper with controlled feed
gate.
Practically vibrationless, finely
counter-balanced.
Air flow rate is adjustable in a
wide range resulting in accurate
final..
Tilt of the deck is adjustable in a
wide range.
Shaking speed of the deck is
adjustable in a wide range.
Dynamically Balanced Fan.

SPECIFICATIONS:
3 Phase 230/460V TEFC Motors
Cleaning Velocities to 4,500 fpm
HP Requirements: 3 to 20 HP, depending on
model and air requirements
Pneumatic separator

These machines use a magnetic force to
separate damaged seeds or other particles from
the good seeds. This is used to solve special
problems in seed lots that can not be taken out
with other basic seed cleaning equipment.
Most of the time it is used for vegetable and
field seeds that have problems in seed damage
(fish mouth in cucumber or melon seeds /
cracked radish or cabbage seeds), insect damage
(beetle holes in cotton seeds) or contamination
with soil or plant parts (white plant parts in
onion seed) etc.
Available with a belt width of 400, 600 or 800
mm.
MAGNETIC SEED SEPARATORS

Magnetic separator
• The magnetic separator separates seed according to its surface
texture or related seed characteristics.
• First, seed is treated with iron filings, which adhere to rough
surface alone.
• The treated seed lot is passed over a revolving magnetic drum
and separated from smooth, uncoated seed.
• It may help to add varied amounts of water while mixing seed
and powder, depending on the seed type.
• At any rate, the effectiveness of magnetic separation depends
on the components of the seed lot and on the powder and water
used in the treating operation.
• The greater the difference between surface textures of the seed
lot’s components, more effective will be the separation.

Magnetic separator
Principle of function

• Cyclonic separation is a method of removing particulates from
an air, gas or water stream, without the use of filters, through
vortex separation. Rotational effects and gravity are used to
separate mixtures of solids and fluids.
• A high speed rotating (air)flow is established within a
cylindrical or conical container called a cyclone.
• Air flows in a spiral pattern, beginning at the top (wide end) of
the cyclone and ending at the bottom (narrow) end before
exiting the cyclone in a straight stream through the centre of the
cyclone and out the top.
• Larger (denser) particles in the rotating stream have too much
inertia to follow the tight curve of the stream and strike the
outside wall, falling then to the bottom of the cyclone where
they can be removed.
Cyclonic separation

Colour separator
• The colour separator is used to separate discoloured seed,
greatly of lower quality.
• Separation based on colour is necessary because the density
and dimensions of discoloured seed are the same as those of
sound seed, so other machines are not effective for separation.
• Electronic colour separation uses photocells to compare the
seed colour with “background” which are selected to reflect
the same light as the good seed.
• Seed that differs in colour is detected by the photo cells, which
generate an electric impulse.
• The impulse activates an air jet to blow away the discoloured
seed.

These new generation colour sorters are
specially designed for the seed industry.
This machine makes a high capacity sort
based on the colour of the seed.
Contamination like discoloured, infected or
damaged seeds, soil and weeds can be
separated.
E.g. white plant parts out of onion, white
from black lettuce seeds, green carrot seeds,
yellow cabbage seeds etc.
These machines have many applications for
all kind of seeds, starting from very small
seeds like lettuce up to pumpkin.
COLOUR SEPARATORS

Material handling includes a number of operations that can be
executed either by hand or by mechanical devices to convey
material.
In earlier periods all these operations were manual. The grains
were threshed or bagged by human labour. Grains are transported
several times through the storage and milling plant, and milled
food product conveyed manually to consumers. Grains were
handled too much involving increased cost and human drudgery.
But in modern times, some mechanical devices have replaced
human labour, other supplement it or in some cases make possible
to handle larger quantities of grains per unit human labour.
The mechanical handling devices aim to lighten the work of
human labour
CONVEYING

2.Belt conveyor
3.Screw conveyor
4.Pneumatic conveyor
1.Bucket elevator
The most common types of mechanical
devices for grain handling

. The belt may flat fo rtransporting bagged material
Belt conveyor
A belt conveyor is an endless belt operating between two
pulleys with its load supported on idlers. The belt may be
flat for transporting bagged material or v-shaped or some
other enclosed shape for moving bulk grains.
The belt conveyor consists of belt, drive mechanism and
end pulleys, idlers and loading and discharge devices.
Belt conveyors have antifriction bearing, therefore, these
have a high mechanical efficiency.

. material
Material carried by belt conveyor lie still on
the surface of belt or there is no relative
motion between the product and belt. This
results in no damage to material.
Belt can be run at higher speeds so large
carrying capacities are possible.
Horizontally the material can be
transported to longer distance but there is a
limit to carry the material on elevation.
For longer distances, initial cost of belt
conveying system is competitive or low.

. The belt maybagged material
Design of belt conveyor
Available space, horizontal conveying length and
conveying lift, characteristic of material to be conveyed
and capacity requirement
On the basis of requirement and information, to design belt
conveyor, belt width and belt speed, required horsepower,
maximum belt tension and breaking strength of the belt,
diameter of pulleys and idlers and quality of belt
(thickness)
Belt speed and width of belt
For grain conveying belt speed of 2.5 to 2.8 m/s.
Belt speed selected for minimize belt spillage removal of fines due
velocity of belt.

.
Belt width
Capacity requirement, speed of operation, angle of inclination of belt
conveyor, trough angle and depth.
Capacity, m3/hr=area of cross section, m2 × belt speed, m/min×60
Trough angle 200 is best suited for grains
Idlers
It must be accurately made and provide a rigid framework and
maintain permanent, well balanced smooth running alignment.
Three types of belt carrying idlers which are used in handling bulk
materials
1. Flat belt idlers are used for granular materials having an angle of
repose of not less than 350 it preferred for low capacity
requirements.

photo0928
2.Troughing idlers with
200 trough. It used for
bulk materials
3.Troughing idlers with 300
and 450 trough it used for
carrying heavier, medium
size lumps like crushed
stones.

.e space between the sucessive
Idler spacing
The space between two successive
idlers should be equal to width of
belt. Upper and return idlers are
placed at equal distance from one
another.
Additional idlers are provided at
loading points to support product
load and to maintain the trough.
The spacing between the idlers
influences the retension of correct
troughing.

Photo0928
Belt tension
The tension developed at drive pulley in transmitting the
required power to move the loaded belt is known as effective
tension.
The effective tension is the sum of tension to move the empty
belt, the tension to move the load horizontally and tension to lift
the material.
Tripper
Grains are mostly discharge from the belt
conveyor over the end pulley or at any
other point along the conveyor by a
scraper plough or a throw-off-cariage
known as tripper.
The belt conveyor can be discharge at
various locations by means of a movable
tripper. It made of two pulleys supported
in a fixed or movable frame.

Photo0928
Selection of proper conveying system
 Conveying device selected according to the characteristics
of the product.
 The stability of the conveyor must be ensured under all
normal working and climatic conditions.
 The capacity of conveying and speed rating should be
maintained at specified limits.
 In conveying system possibility of use of gravity should be
taken into consideration.
 The capacity of handling/conveying equipment should
match with the capacity of processing unit.
 Spillage of conveyed products avoided. Pollution of the
environment due to noise or dust by conveying system
should be avoided.

Screw Conveyor
History of Screw Conveyor
•Archimedes (287 to 212 BC) a Greek mathematician, physicist and
inventor, invented for removing water from the ship built for King
Hiero of Syracuse. Later on which is called as Archimedian Screw.
•After about 1900 years, in 1790 , a American Mentor, John Fitch,
designed a steam boat to be propelled by a section of screw conveyor.
•In 1783, the man who might be called the patron saint of mechanized
materials handling, Oliver Evans laid out on paper his first mechanized
flour mill which incorporated not only screw conveyors but bucket
elevators and belt conveyors as well and eventually built it in 1785.
•The next technological advancement of importance in screw conveyor
design was patented in 1898 by Frank C. Caldwell.

Single Inlet loading
Multiple Inlet Loading

5. Screw Pitch:
Commonly the screw pitch is taken equal to the diam
Of the screw D. However it may range 0.75 – 1.0 times the
diameter of the screw.
6. RPM of Screw:
The usual range of RPM of screw is 10 to 165.
It depends on the diameter of screw and the type of mater
(Max RPM of screw conveyor is 165)
7. Inclination Factor:
The inclination factor C is determined by the angle o
screw conveyor with the horizontal.
Angle of screw with the
horizontal
0° 5° 10° 15° 20°
Value of factor C 1 0.9 0.8 0.7 0.65

• Screw conveyors are capable of handling a great
variety of bulk materials from sluggish to free-flowing.
• Screw conveyors can have multiple inlet and
discharge points.
• Screw conveyors are very compact and adaptable to
congested locations.
• Screw conveyors are totally enclosed to contain the
product and prevent spillage.
• Screw conveyors can be utilized in the horizontal,
vertical or any inclined position depending upon the
characteristics of the product being conveyed.
• Screw conveyors can be used for mixing various
products together and for breaking up large lumps.
Advantages of Screw Conveyor

Drawbacks in Screw Conveyor
• Due to gap between edge of blade and trough it is not
possible to completely empty the horizontal conveyor
• If it used for conveying for different material , mixing of
product is possible.
• Pressing of Kernels between edge of blade and trough c
kernel damage.
• Kernels are also subjected to continuous friction with tro
walls.

Pneumatic Conveyor
The pneumatic conveyor moves granular materials in
a closed duct by a high velocity air stream. Pneumatic
conveyor is a continuous and flexible transportation method.
The material is carried out in pipelines either by
suction or blowing pressure of air stream.
In design of pneumatic conveyor two factors are
considered
1. Supply air pressure
The magnitude of air pressure depends on the
conveying length and properties of the product to be
conveyed.
2. Volumetric flow rate of air
It depends on necessary air velocity and pipe or duct
size used in the system.

Types of Pneumatic conveyor
There are two types of pneumatic conveyor
according to operating principle
1.Dilute Phase
2.Dense Phase
1. Dilute Phase Pneumatic Conveyor
• Particles are fully suspended in air and transported
at low pressure and high velocity
• This is most common method used for non abrasive,
non fragile material that have light bulk density
• This system used for conveying materials at short
distance at low capacity.
• It is ideal for conveying materials from multiple
source to a single destination

Dense Phase of Pneumatic Conveyor
• The particles are not suspended in air and are
transported at high pressure .
• It is suitable for conveying fragile or abrasive material
with particles ¾ inch and smaller over longer
distances (typically above 250 feet ).
• The material conveyed by this method is loaded in to
a pressure vessel.
• When material is full, it’s material inlet valve and vent
valve are closed and compressed air is metered in to
vessel.
• The compressed air extrudes the material from the
pressure vessel to conveying line and to destination.
• Once vessel and conveying lines are empty, the
compressed air turned off and the vessel is reloaded.

Photo0928
References
K. M. Sahay and K. K. Singh, textbook of Unit
operations of agricultural processing.
www.agri-systems.com/belt.php
www.youtube.com
www.rapat.com/pdf_files/drag/bktelv.pdf
www.alibaba.com/showroom/bucket-elevator-parts.html

• http://www.archimedes.net.au/general/screw-conveyor-
history
• http://www.kwsmfg.com/products/CEMA-Conveyor-
Equipment-Components.htm
• http://www.kwsmfg.com/engineering-
guide/horsepower.htm
• http://www.kwsmfg.com/engineering-guide/conveyor-
flight-pitch-types.htm
• http://www.kwsmfg.com/engineering-
guide/componentselect.htm

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