AGRICULTURAL MACHINERY AND FARM POWER ENGINEERING
CASE TEAM
Project Title: Improvement of crop production through design, construction
and evaluation of agricultural machinery and farm power technologies in
South western Oromia.
COMPONENT 1: Development and Evaluation of postharvest technologies.
Activity 1: Development and Performance evaluation of groundnut Sheller
INTRODUCTION
Groundnut is one of the five widely cultivated oilseed crops in Ethiopia (Wijnands et al., 2009).
Jimma Zone of Oromia region hold tertiary position, next to Eastern Hararghe Zone in producing
and supplying both domestic and export market (unpublished Ethiopia Export Promotion report,
EEP, 2004). Moreover, groundnut generates considerable cash income for several small scale
producers and foreign exchange earnings through export for the country (Geleta et al., 2007).
Even though, groundnut is the fourth most produced oilseed in Ethiopia, the potential and
prospect as source of income and its capacity to generating household income is constrained due
to lack of appropriate shelling machine.
Shelling, the first major postharvest operation, involves application of mechanical forces to open
pods and recover kernels. The applied forces fall on the pod at random, breaking the pods
stochastically, to free the enclosed kernels. The physical phenomena involved in shelling of
groundnut include breakage of the pod which depends on the intensity of the applied force, the
orientation of the pods, moisture content, freedom of the kernel from the pods and the passage of
the kernels and broken pods through the concave openings.
Groundnut shelling, in Ethiopia, at present is predominantly traditional, manual method, using a
short wooden stick to beat it, or by pounding with pestle in mortar. These methods of shelling
consume high man-hour with the associated fatigue and low output. The shelling operation is
particularly tasking due to the thickness and hardness of the nut. Singh (1993) reported that the
pod thickness influences shelling efficiency and percent kernel breakage.
According to studies made by Kebede (1997), farmers’ loss substantial amount of the kernel
produced during harvesting, shelling, transporting and storage due to use of obsolete practices.
The total loss has been estimated at about 20-40% of the total production. Out of the total
estimated loss 20-30% is due to poor land preparation, 30-40% is due to weeding infestation, 20-
25% is harvesting and 20-30% is during postharvest operation.
Traditional shelling methods do not support large-scale shelling of groundnut, especially for
commercial purposes. Locally, in Limmu Genet , Shabe Sombo Bunno Bedelle zone and Illu
Babor Zone . The Zone that produce the largest amount of groundnut in the Oromia Region, it
was observed that most shelling of groundnut was done manually using simple tools. This
practice usually takes a lot of time; causes great damage to the groundnut kernel and does not
separates kernels from the husks and broken stone. Hence, this study was initiated to design,
construct and evaluate groundnut sheller that would be affordable by farmers and decrease
damage and loss of groundnut kernel during shelling.
Objective
To design and evaluate appropriate type of ground nut shelling machine with high
productivity for rural farmers.
To evaluate the performance of constructed prototype at different levels of cylinder
speeds, feed rates and moisture contents.
To evaluate groundnut Sheller machine developed previously depending on variety.
To summarize recommendations for further studies in same fields.
MATERIALS AND METHODS
Material Selection: The materials used will be obtained locally at market, the materials will be
critically considered based on strength, availability, durability and corrosiveness to prevent
machine damage, ease construction work and maintenance and prevent rusting or corrosion of
the machine parts hence, mild steel angle iron will be used for the frame and stainless steel for
the shelling chamber.
Design Consideration
A number of points will be considered during the design. Such points include the cost of
construction, power requirement of the machine and labour requirement in operating the
machine. Also considered in the design will be the ease of replacement of component parts in
case of damage or failure. The design considerations included use of gravity and minimum
friction to reduce power requirement, economy and ergonomics, machine efficiency and product
quality, simple operational and maintenance requirements to meet the need of local farmers and
small scale industrialist, portability and detachability for easy transportation and low grain
damage. In addition to this the capacity, angle of repose of parchment groundnut and
environments are important factors considered.
2. LITERATURE REVIEW
2.1 Groundnut production
Groundnut originated between southern Bolivia and northern Argentina from where it spread
throughout the New World as Spanish explorers discovered its versatility (CGIAR, 2008).
Presently, groundnut is grown in nearly 100 countries. Major groundnut producers in the world
are: China, India, Nigeria, USA, Indonesia and Sudan. Developing countries account for 96% of
the global groundnut area and 92% of the global production. Asia accounts for 58% of the global
groundnut area and 67% of the groundnut production with an annual growth rate of 1.28% for
area, 2.00% for production and 0.71% for productivity. It is grown on 26.4 million ha worldwide
with a total production of 36.1 million metric Tons and an average productivity of 1.4 metric
Tons per ha (FAO, 2008).
The crop does well where average rainfall is from 600 to 1,200 mm and mean daily temperatures
are more than 20 degrees Celsius. Groundnut is a valuable cash crop for millions of small-scale
farmers in the semi-arid tropics. It generates employment on the farm and in marketing,
transportation and processing. According to Okumu (2000), groundnut should not be viewed
only as a cash crop but also as an input for improving soil fertility through Nitrogen fixation.
This makes Groundnut the 13th most important food crop of the world (CGIAR, 2008). It is the
world's 4th most important source of edible oil and 3rd most important source of vegetable
protein. Groundnut seeds contain high quality edible oil (50%), easily digestible protein (25%)
and carbohydrates (20%). The seeds yield a non-drying, edible oil, used ic cooking, margarines,
salads, canning, for deep- frying, for shortening in pastry and bread, and for pharmaceuticals,
soaps, cold creams, pomades and lubricants, emulsions for insect control and fuel for diesel
engines. The oil cake, a high-protein livestock feed, may be used for human consumption. Other
products include dyes, ice cream, massage oil, paints and peanut milk. Seeds are eaten raw,
whole roasted and salted or chopped in confectioneries or ground into peanut butter. Young pods
may be consumed as a vegetable. Young leaves and tips are suitable as a cooked green vegetable
(Martin and Ruberte, 1975). Groundnut hulls are used for fuel, as filler for fertilizers and for
livestock feed or sweeping compounds. Most U.S.A. production enters the peanut butter (50%),
salted peanuts (21%), and confectionery (16.5%) markets. Elsewhere peanuts are processed
mainly for oil (Duke, 1981a).
Design parameters and Calculation:
The following parameters will be some physical properties of the coffee seed used for the design
calculations; Density of the seed, Seed width , Seed length, arithmetic diameter, geometric
diameter, etc.
The pre-design stage included measurement of the physical and engineering properties of the
crop to determine appropriate design parameters for the threshing operation. The decorticating
and separation component will be designed using relevant engineering principles and theories.
Design of Shaft
The shaft is a rotating machine element used to transmit power from one point to another. The
shaft will be designed on the basis of strength, rigidity and stiffness. When designing the shaft, it
will be taken into consideration that it may be subjected to twisting and bending moment.
The formula used for the shaft design will be;
3 16 T
d=
√ πσ
d = shaft diameter (mm)
T = torque of the shaft (Nm)
σ = maximum permissible work stress (N/m)
Torsional Deflection of the Shaft
The tensional deflection of the shaft will be determined to know the angle of deviation of the
shaft and to ensure minimal angle of deviation. It will be determined by the following;
584 τl
α=
D4
Where
α =angular shaft deflection
l = length of the shaft
D = modulus elasticity of steel
Power Requirement of the Shaft
I. Power required to drive shaft
P=W ∗R
Where W= weight of the shaft
R=radius of shaft
W=mass of shaft∗gravity
Fan power requirement
The power required to drive the fan was calculated using Q and HT.
Q HT
Pf =
η
Where:
Pf =¿Power to drive the fan (watt)
Q = fan duty (m3/s)
H T =theoretical total pressure at head developed (Pa)
η=¿Transmission efficiency
Design of fan
The flow rate of the air is determined from area of fan discharge.
Q= A C Mean
Where: Q= air flow rate at fan discharge
A= area of fan discharge
C Mean=mean velocity
Selection of belt
Two belts will use to transmit power from engine to the cylinder and fan shaft. The length of belt
will calculate. The center distance was determined according to the following equation
(Maciejczyk and Zdziennicki, 2000) and designed distance between driving and driven pulley
center of the machine.
Efficiency of Sheller
The efficiency of Sheller machine indicates that the performance evaluation of the machine.
Moisture Content: The moisture content will be depend on the variety of groundnut available in
g Jimma ,Illubabor and Bunno Bedelle using conventional oven drying method with the aid of an
electric weighing balance, oven dryer instruments. The seed will compute on wet basis using
equation of:
Wwp−Wdp
Mcwb=
Wwp
Where: 𝑀𝑐𝑤𝑏 is the Moisture content in wet basis, 𝑊𝑤𝑝 is the Weight of wet product (g) and
𝑊𝑑𝑝 is the Weight of dry product (g).
This performance also includes the following parameters:
Qs
a) Shelling capacity (kg/h) =
Tm
Qd
b) Mechanical damage (%) = ×100
Qu+Qd
Qs
c) Shelling efficiency (%) = ×100
Qt
W hw
d) Cleaning efficiency (%) = × 100
Wt
Qt = Mass of Pod fed into the hopper, kg
Tm = time of shelling operation, h
Qs = quantity of shelled groundnut pods, kg
Qu = quantity of undamaged groundnut kernels, kg
Qd = quantity of damaged groundnut kernels, kg
Whw = quantity of winnowed husk, kg
Whk = quantity of husk goes with kernels , kg
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