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Evaluation
of Cassava Processing Equipment developed by ESARC in
Uganda.
By
Sicco Kolijn, APO Post-Harvest Operations, FAO Regional
Office for Africa, Accra, Ghana.
&
Dr. Shaun Ferris, FOODNET Teamleader, ESARC/IITA, Kampala,
Uganda
1.
Objective of evaluation of equipment:
The ESARC team, together with researchers of the National
Cassava and Post-Harvest Programs of NARO, has made
some serious efforts to introduce new Cassava processing
technologies for Uganda. As the need of processing 'bitter'
cassava was a high priority in the period '95-'98 due
to the outbreak of the Cassava Mosaic Virus and therefore
the shortage of 'sweet' varieties the team initially
focused on small equipment. More recently the emphasis
has been on the setting up of in-come generating, sustainable
cassava processing enterprises operated by farmers,
groups and commercially oriented individual farmers.
Powered driven equipment enables people to process bulky
cassava in a more economically way providing them with
a income and high quality cassava flour.
The ESARC team and a few dedicated metal workshops in
Kampala and Soroti developed and kept modifying the
equipment. Several farmers' groups made feedback and
recommendations for modifications during the on-farm
test phase. The metal workshops are well motivated in
modifying the current designs and are trying to market
the models themselves during trade and farmers shows.
Main objective remained to come up with appropriate
and affordable equipment for farmers, providing them
with an incom-generating activity.
This equipment evaluation was carried out to document
the current existing processing equipment, identify
shortcomings and made recommendations for further improvements.
The tests were conducted late '99 at Namulonge (IITA's
Research Station) and with assistance of the dedicated
staff of Tonnet Enterprises in Kampala.
2. The need to modify equipment by ESARC during '97-'99
Various important reasons to keep improving and modifying
the equipment:
- Ideas
and recommendations obtained from abroad (e.g. West-Africa,
Brazil, Vietnam and literature)
-
Recommendations made by metal workshops and farmers
during construction and processing process
-
Need to reduce construction costs and availability
of materials
- Need
to improve processing performances
New ideas and findings made through doing research
3. The range of Equipment currently available in
Uganda
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MK
1 Cassava Grater
Design developed by IITA's Post-Harvest Engineering
Unit, Ibadan, Nigeria. This model has been widely
promoted in West-Africa among IITA partners (i.e.
Sasakawa/Global 2000) as a better alternative for
the local models graters used throughout West-Africa.
Grating surface is a punched metal sheet wrapped
on a cylinder/drum. The specially designed hopper
shape was designed to guarantee safe and fast feeding.
The grater can also be used to process fruits (i.e.
pineapple) to extract juice.
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MK
2 Cassava Grater
First modified prototype developed by ESARC team
and SAIMMCO Soroti. The hopper was re-designed to
allow faster feeding without using sticks and/or
operator's hands. The engine is lowered to reduce
noise and make the model more stable. |
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MK
3 Cassava Grater
This model is based on the MK 3 but constructed
with stronger materials and welds in order to reduce
vibration and improve durability. The hopper shape
was further improved to reduce the particles of
the cassava meanwhile maintaining its "non-intervention"
feeding system.The hopper is mounted on hitches
allowing easy and quick access to the metal grater
drum for cleaning and check-ups. |
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MK
4 Cassava Grater with Metal drum
These 2 models are similar to each apart from the
grating drum. The overall construction is simplified
and reduced in order to reduce costs, construction
weight and ease maintenance and cleaning. MK 5 is
equipped with a metal drum with hacksaw blades based
on a Brazil model.
MK 5 Cassava Grater with Wooden drum
The wooden grater is based on a Vietnamese design
using a wooden drum with small 'nails'. The nails,
4-6 mm long are made out of electric cable wire.
This nail grater should produce a finer cassava
mash (i.e. starch). |
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MK
6 Horizontal Disc Grater
This model was designed to improve further the feeding
of tubers as the previous models still needed additional
operator's assistance (incl. the risk of injuries
and accidents). The disc is fitted with hacksaw
blades and the top-lid can be easily opened for
inspection and cleaning. The unit powered by a 4
Hp lane mower engine with a gear reduction to increase
traction. Due to the high speed this model should
be ideal for starch processing. |
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IITA
Chipper
This design and the Chipping disc is developed by
the IITA PHEU in Nigeria. It can be electric driven
or attached on the Power Grater. Chipping cuts out
the dewatering operation but unfortunately is only
appropriate for processing of sweet Cassava varieties
as it does not reduce the HCN levels considerable.Dried
chips dry within 2 sunny days and can be further
processed into high quality flour, animal feed and
snack products.
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Power
Chipper/Slicer
This ESARC's model is equipped with a 3.5 Hp Petrol
engine, speed reduction to improve the chip quality
and thickness.This model can be mounted with a slicing
disc for processing both cassava and sweet potato.Dried
sweet potato is common staple food and practice
in Teso, Eastern Uganda. |
4.
Testing Proceedings and Results
| Test
Proceedings |
| The
capacity of each machine was measured by processing
100 kg peeled Cassava by one single operator. The
Cassava, PDB, 18 months old was soaked 1 for logistic
reasons. Night. Samples of the various flours, chips
and slices were taken to analyze the cyanide levels
of the final product.Particle distribution was determined
with simple household sieves as more sophisticated
sieves were not available. The Starch was screened
through a cloth similar used for cassava screening
in Vietnam, using approx. 25 liters of water/batch.
1 Kg of wet grated cassava was screened and the
3 fractions (course, finer and starch) were oven
dried and afterwards weighted to calculate the starch
recovery efficiency. Dry matter content of the fresh
roots: 31%.Max rpm of Petrol engine: 3150 rpm. |
 |
| Test
Results |
Output
(kg/hours)
with one
Operator
|
Estimated
RPM
(range)
Of drum
|
Dry
Matter
Content of
dried flour
(%)
|
CN
levels
of dried
final
product
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Partical
distribution at low rpm
|
| Power Chipper |
600
|
410-773
|
89
|
19.3
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Fibers
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Finer
|
Starch
|
| Power Slicer |
650
|
410-775
|
87
|
17.3
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| MK 3 Power Grater |
1050
|
860-1800
|
84
|
8
|
33..3
|
6.1
|
60.6
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| MK 4 Hack Saw Blade Grater |
330
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1100-1150
|
84
|
12
|
33.8
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6.1
|
60.1
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| MK 5 Starch Grater |
325
|
1100-1150
|
86
|
18
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35.8
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5.2
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59.0
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| MK 6 Horizontal Disk Grater |
-
|
1150-3150
|
83
|
7
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25.3
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6.4
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68.3
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Observations
and recommendations for improvements:
1) The cover of the chipping box should
be wider: there is too little room for the chips
to get out without breaking trough impact with the
rotating disc.
2) The RPM could be lower in order as now the best
processing speed is when the engine runs on the
idle speed. Recommendation: reduce RPM disc by using
a intermediate, second shaft with a pair of polly
between the engine and disc?
3) The overall design could be simplified as the
construction is still too big: no need for table
at the top (why not incorporating a holder for a
plastic basket?).
4) Current chipping discs are imported through the
Post-harvest Engineering Unit, IITA, Ibadan, Nigeria
and difficult and expensive to obtain. Therefore
there is a strong need to establish a local source
of a similar chipping plate in East-Africa as sweet
varieties (and therefore chipping in particular)
will become more important and popular among farmers
and processors. The new fly-press installed soon
at TONNET Enterprise in Kalerwe could be a good
starting point for making them locally in Kampala
although this requires technical assistance/guidance
and financial assistance. |
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| MK
4 Hack Saw Blade Grater |
- Observations
and recommendations for improvements:
1) Current speed is too low; in stead of
a speed reduction of 1:3 (max. 1100 rpm) a reduction
of 1:2 or even 1: 1 will perform much better
(higher capacity and finer product).
2) The guard is to close to the V-belt and pouly
: needs enlargements and allowances for adjustment
of the engine.
3) Make the cover/lid of the drum easier assessable
by using a pair of hitches like MK2 and MK3.
The inlet of the hopper should be narrowed according
to the effective working width of the drum.
The strips on both sides are now just blocking
the tubers affecting the capacity of the machine.
The feeding tray should be divided in 2 compartments
by one guide/separator in the middle. As the
speeds increase there is also a need to cover
the top of the feeding tray as some tubers tend
to shoot upwards/back.
4) Need to reduce the vibrations by:· reducing
the cause of vibrations namely balancing the
drum, shaft and pouly (e.g. counter- bolts for
the locking of the pouly on the shaft rather
than one single bolt)· incorporating 2 cross-angles
in the support frame of the grater (lengthwise),·
attaching 2 fixed wheels under the at outlet
tray side and a two rubber shoes below the extended
feet on the other side. The wheels will ease
the movement of the machine and absorb vibrations.
On this side we could make a handle bar (square
bar in a bigger square bar, with locking pin
and handle at the end)
5) The hacksaw blades looked to be strong and
durable (hardened steel blades imported from
Brazil) but during the last test with Shea Nuts
two blades broke and came out. Questionable
is the ease of replacements of the blades, as
everything seems to be welded very firmly locked
and hidden away; making it very difficult to
carry out replacement/repairs.
6) Make the cover/lid of the drum easier to
open by using a pair of hitches (like MK2 and
MK3). The inlet of the hopper should be narrowed
according to the effective working width of
the drum. The guards on both sides are now just
blocking the tubers and therefore affecting
the capacity of the machine. As the speeds increase
there is also a need to cover the top of the
feeding tray as some tubers tend to shoot upwards/back
(discussed with Joseph Kavuma).
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| Observations
and recommendations for improvements: |
1)
During the tests at Sendusu the speed was set on
1075 rpm and the capacity and fines of the product
was very low. After changing the poulies (1: 1 transmission
rate) the speed went up to max. 3200 rpm. After
testing the machine again at different speeds, between
1700 up to 3200 rpm, we observed a strong relationship
between increased speed and quality. A good speed
is 2500 rpm as at this speed the Cassava is going
through the grater without assistance of the operator
(e.g. pushing). With the speed set around this design
is most likely the best machine among the MK grater
family for starch and flour processing.
2) Need to reduce the vibrations by:· reducing the
cause of vibrations namely balancing the drum, shaft
and poulie (e.g. counter- bolts for the locking
of the pouly on the shaft rather than one single
bolt)· incorporating 2 cross-angles in the support
frame of the grater (lengthwise),· attaching 2 fixed
wheels under the at outlet tray side and a two rubber
shoes below the extended feet on the other side.
The wheels will ease the movement of the machine
and absorb vibrations. On this side we could make
a handle bar (square bar in a bigger square bar,
with locking pin and handle at the end)
3) Enhance the accessibility of the wooden spacer
as this one is still hidden under the feeding tray
(by making the spacer wider; allowing the locking
bolts to be situated further from the drum).
4) Make the cover/lid of the drum easier to open
by using a pair of hitches like MK2 and MK3. The
inlet of the hopper should be narrowed according
to the effective working width of the drum. The
strips on both sides are now just blocking the tubers
affecting the capacity of the machine. The feeding
tray should be divided in 2 compartments by one
guide/separator in the middle. As the speeds increase
there is also a need to cover the top of the feeding
tray, as some tubers tend to shoot upwards/back.
5) The 'nails' are good attached in the wooden drum:
approx. 3 millimeter above the surface and 7-8 nails
per cm.
6) The guard is to close to the V-belt and pouly
: needs enlargements and allowances for adjustment
of the engine as the V-belt is some case touches
the guard. |
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