A an average time of 47.58 seconds which implies

A
palm nut cracking machine with an efficiency of 74.2 percent, a throughput
capacity of 75.6 kg/hr has been successfully and economically designed and
developed. The machine was developed using locally sourced materials. Also,
Maximum loading of the hopper which is about 10.8 kg and 0.02m3 in
volume will be cracked in about 9 minutes. The average amount of palm nuts
cracked per day is about 1872kg by the cracking machine, it takes a normal
farmer about 144 kg per day. Therefore the cracking machine using locally
sourced materials will help increase productivity and efficiency in the palm
nut cracking process in the rural areas.

CONCLUSION

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The
average amount of palm nuts cracked per day is about 1872kg by the cracking
machine, it takes a normal farmer about 144 kg per day.

Based
on the average amount of cracked palm nuts supplied into the machine, it can be
said that the average efficiency of the machine is about 74.2%.The palm kernel
nut cracking machine has an average efficiency of about 74.2 %.

                                            (25)

By
utilising Gbabo et al. (2013) equation for efficiency which was adopted for the
dehulling efficiency for the Moringa dehulling machine by Ikubanni et al.
(2017), the cracking efficiency for the palm nut cracker was derived using
equation (25).

Therefore
10.8kg will take 514secs which is about 9mins.

Since
1kg of palm nut takes 47.58sec,

The
hopper has the shape of a frustum of a pyramid. The total mass of the palm nuts
that can be accommodated in the hopper is 10.8kg.

=
(0.021kg/sec) × 3600 sec = 75.6kg nuts/ hour

Therefore,
throughput capacity (nuts/hour) = shelling rate × 1hour                              (24)

The
experiment in evaluating the machine shows that 1kg of palm kernel nut cracks
at an average time of 47.58 seconds which implies that in 1 second the machine
will crack 0.021kg of palm kernel.

 

 

Mass of palm kernel Nuts (kg)

Cracking time taken (s)

Mass of Un-cracked nuts (kg)

Mass of cracked nuts

Mass of partially cracked Nuts (kg)

1

46.13

0.3

0.64

0.06

1

50.02

0.2

0.76

0.04

1

48.26

0.27

0.66

0.07

1

44.21

0.18

0.8

0.02

1

49.27

0.1

0.85

0.05

Average

47.578

0.21

0.742

0.048

 

 

 

 

Table
1:
Performance tests on the developed palm kernel
nuts cracking machine

Table 1 shows
the performance evaluation results for the developed palm kernel nuts cracking
machine, with speed of 1400 rpm. The experimental tests show that at the same
speed, 1kg of palm kernel nut will crack at an average time of 47.58 seconds.
The average mass for the un-cracked palm nuts, cracked palm nuts and partially
cracked palm nuts were 0.21 kg, 0.742 kg and 0.048 kg, respectively.

RESULTS AND DISCUSSION

Fig. 3: Pictorial
view of the machine

                                   

Fig. 2:
Isometric View of the machine

Part No.

Part Name

1

Hopper

2

Drum

3

Shaft

4

Collection
tray

5

Electric
motor stand

6

Frame/Stand

7

Drum
handle

 

 

 

 

 

 

 

Fig.1:
Orthographic Projection of the machine

                                   

The
driving unit consist of an electric motor and a pulley. The electric motor is
rated one horse power (1hp), with frequency of 50 Hz and revolves at 1400 rpm. The
pulley is of diameter of 80 mm connected to the driven pulley by a belt 480 mm
long, 12 mm wide and 9 mm thick.

The Driving Unit

The hammers are made of mild steel
plates of 50 mm width, 130 mm long and 8 mm thick. Each hammer has two
sections; one which is attached permanently to the shaft, and another attached
to the initial plate by a temporary joint. The section attached to shaft has a
length of 60 mm and is slotted at its centre to allow total change in length of
the hammer. The section is 100 mm long, and is drilled 15 mm from the bottom to
allow screws pass through (the same screws pass through the slot available on
the first section). The change in length is required in case of wear of the tip
of the hammer as a result of hitting the nuts at very high speed. The hammers
are placed in pairs horizontally along the length of the shaft and an angle of
1200 separating the shafts on the circumference of the shaft.

The
Hammers

 

The
driven unit consist of the shaft to which six hammers are attached and a
pulley. The pulley has a diameter of 175 mm. the shaft is made of mild steel,
and has a diameter of 25 mm for a length of 50 mm at one end of the shaft, a
diameter of 39 mm for a length of 150 mm (to which the hammers are attached) at
the centre, and a diameter of 25 mm at the other end of the shaft for a length
of 100 mm.

The Driven Unit

The
drum is the cracking unit of the machine made of mild steel plate. It is made
in the shape of a hollow cylinder with a diameter of 415 mm, has a height of
200 mm, and the plates are 10 mm thick. The cylinder is covered on both sides
with a circular plate 420 mm diameter which has circular openings of 50 mm
diameter for shafts to pass through. Inside the drum is a portion of the shaft
to which the hammers are attached. The rotating action of the hammers, as a
result of the rotation of the shaft, cracks the palm nuts fed into the chamber.
At the top of the drum is an opening 30 mm by 140 mm which opens up to the
hopper. At the bottom also are series of openings through which cracked nuts
fall out of the drum.

The Drum

The
hopper is the feed-in unit of the machine. It has the shape of a hollow frustum,
and is made of mild steel. It has a height of 300 mm, a length of 30 mm at the
bottom and 300 mm at the top of two of its plates. The other two plates have a
length of 140 mm at the bottom and 300 mm at the top. The four plates are
marked and cut out from a metal sheet of 3 mm thick, welded together using
electric arc welding. The hopper is placed vertically on a drum to allow the
nuts fall under gravity.

The Hopper

Machine Parts and Fabrication

 

Angle
of Lap

                                    = 419.67W

           

Power
transmitted by the belt

                                                         
= 47.72 N

Tension
in slack side T2 = 0.4 x T1 = 0.4 x 119.3

                                                                      
= 119.3N

Maximum
value of Tension in tight side T1 = 129.6 – Tc = 129.6 – 10.3

                                                                  =129.6N                                                                                                                                                                                                                       
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      

Maximum
safe belt tension = Max stress x cross sectional area

From
calculation,,
 and

Where
N1 = r.p.m of driving pulley; N2 = r.p.m of driven pulley;
d1 = diameter of driving pulley;         d2 = diameter of driven
pulley

Also,

Where
 is angular velocity and N is speed of rotation
in revolution per minute

 

Assume
maximum stress in belt is 1200 kN/m2, and tension in slack side is
40% of tension in tight side.

Mass
per unit length of belt, m =0.3kg/m; Belt Length = 48cm = 0.48m; Belt Breadth
=0.012m; Belt thickness = 9 x 103m;

where  is centripetal tension,  is mass and  is the speed.

Centripetal Tension,  

Design for Belts

However,
three (3) hammers were acting at a point; therefore, the point load was
determined to be .

Using
the above formula, the mass of a single hammer was calculated to be 0.628kg and
the weight was derived to be 6.16 N.

 

Density
of mild steel is 7850kg/m3, and

Torque
produced by electric motor, T=5.12N-m

Power
transmitted, 

Therefore,
an electric motor of one horse power (1hp), with speed of 1400 rpm and power
rating of 750W was chosen.

P=328.7W

The minimum power requirement,

Mechanical Power
requirement

T
= 3.537 Nm

Where

The
tangential force,

Where
 is the mass,  is the radius of gyration,  is the moment of inertia about x-axis, b and h
are the width and height of the hammer, respectively.

 

Moment
of inertia about x-axis

 

To
allow a gap of only 0.03mm between the hammer and the drum, a total hammer
height of 0.32 m is required.

where is the total height of the hammer.

  

Radius of gyration of hammer,

Shaft Requirement

 

 =14.869 m/sec

For Dura Nuts,

Hammer Requirement

 

Where
 is the deformation energy and is given as
0.9012 dura nuts

Hence,

Therefore
r = 2, and F = 2P

Where
 and

Where
P is the impact loads applied to kernels and r is the ratio of the stress under
impact to the direct stress or the deformation under impact to the
corresponding deformation.

     

Where
F is the force or load applied and x is the distance travelled.

 

Impact
energy on the cracking wall = Work required to deform a kernel

Kinetic energy of kernels = Impact energy
of kernels on the cracking wall

Cracking Requirement

DESIGN ANALYSIS

 

The materials selected
for the design and construction of the machine were majorly the stainless steel
and the mild steel. The criteria of
selecting these materials are: (i) durability of the material, (ii) strength of
the material, (iii) suitability of the material for cracking operation,      (iv) availability of the material and (v)
the cost of the material. 

In order to have
efficient design, various design considerations were put into place. The
hopper, drum, the cracking mechanism parts (hammer), shaft and frame were from
mild steel. The thickness of the mild steel used for the hammer is more than
that used for the hopper. This is expected to be because the cracking of the
palm nuts require harder materials to crack the nuts and a designed speed of
rotation for the shaft.  

Design
Consideration and Material Selection for Production 

 

When the palm nuts are
fed into the hopper, they descend into the cracking chamber by gravity, aided
by vibration agitated by the prime mover. The high rotating hammer impacts
force on the nuts suddenly; the nuts are then thrown towards the wall of the
cracking drum. The nuts also impact energy on the wall of the cracking drum.
The sudden impact load of the hammer on the nuts lead to the breaking of the
nuts and the shells are fragmented into smaller parts due to centrifugal
action. The kernel and the fragmented shells are force driven out of the
cracking chamber to the collecting bowl at the outlet.

The palm nut cracking
machine is made up of about five units viz: the feed-in unit called the hopper;
the cracking unit called the drum; the driving unit consisting of an electric
motor, pulley and V-belt; the driven unit which consists of a rotating shaft
that bears the cracking hammers’ being driven by a V-belt connected to a prime
mover. The stand and the supporting frame is made of angle iron of gauge 50 mm
by 50 mm by 6 mm. The hopper is made of mild steel of 3 mm thickness and has a
capacity of 0.018 m3; and can accommodate palm nuts of about 10.8 kg
at its full capacity. The cracking drum is made of mild steel of 10 mm thick,
the rotating shaft is supported at both ends on bearings and it is of length
300 mm with a diameter of 25 mm for a length of 50 mm from one end and 25 mm
diameter for a length of 100 mm from the other end with 30 mm diameter for a
length of 150 mm at the centre, where the hammers are attached. The hammers are
made of mild steel of 8 mm thick, 50 mm wide and 130 mm long. The electric
motor of the driving unit is rated 1hp with frequency of 50 Hz, speed of 1400
rpm. The pulley has a diameter of 80 mm which is connected to a V-belt of
length 480 mm, 12 mm wide and 9 mm thick. The pulley attached to the rotating
shaft has a diameter of 175 mm.

Machine
Description and Working Principle

In the methodology for
this work, the design analysis of the palm nut cracking were done, material
selection for each component designed were determined, the design calculations
of the machine parts were done, operating description of the system was
discussed and the engineering drawings were shown. Electric motor serves as the
primary source of driving the machine so as to perform the required action of
cracking palm nuts.

MATERIALS
AND METHODS

 

In
order to mechanise cracking of palm nuts, a palm nut cracking machine was
developed in this work. Moreover, the performance evaluation of the developed
machine such as determination of the efficiency, throughput and processing rate
were done. The developed machine will help to reduce the laborious task and
time of cracking palm nut for other processes.

Due
to the ever increasing demand for products derived from processed palm kernel,
there is a need to improve on the traditional method of cracking through
mechanisation to ensure ready availability. The nut cracking is one of the most
time consuming activities of the palm kernel processing, therefore the
introduction of a machine to crack and separate palm kernel from its shell at a
faster rate will go a long way in speeding up the process, and helping to meet
demand.

Ismail
et al. (2015) developed and improved
palm kernel shelling and sorting machine with a shelling and sorting efficiency
of 90%, and throughput of 59 kg/h. The whole kernel recovery was 70 percent.
Adejuyigbe et al. (2017) designed an improved palm kernel shelling and sorting
machine which can be used to crack various sizes of palm kernel with an
incorporated sorting unit for separation. The efficiency of the machine was
determined to be 98% with 95 nuts per second as the processing rate. A
comparison was made with an existing palm kernel machine of 90% efficiency and
87 nuts per second processing rate without separation. A modified design of
palm kernel cracker was done by Asibeluo and Abu (2015) in which a cracking
rectangular channel was welded  to a
cracking flywheel with a centralized hole through which every nut must pass
through and capable of making contact with every nut; hence cracking nearly all
the nuts. This design was incorporated with two different separators. Oyebanji
et al. (2013) performed the evaluation of two different palm kernel nut cracker
designed.  It was stated that the
vertical centrifugal palm kernel cracker is more efficient than the centrifugal
impact approach palm kernel cracker considering their respective efficiencies
of 71.3% and 50.38%. Some other works on palm kernel cracking were done by
Jimoh and Olukunle (2013); Koya (2006) and many others.

Cracking
palm nuts is a critical step that can affect the quality of kernel oil
(Oyebanji et al., 2013).  The manual
(traditional) and mechanical (mechanized) method are the two commonly used
methods for cracking. In traditional processing, the nuts from the oil palm
fruits are cracked manually using a stone, or any other heavy and dense object
one at a time. As a result of this, the processing altogether takes excess time.
Moreover, this method is labour intensive, time consuming and cumbersome (Oke,
2007). In cases where demand is high, a large labour force is required to meet
up with such demand, which in turn increases the overall cost of the process as
a result of an increase in the amount paid as wages to workers; thereby
increasing the selling price of its final products. In areas where a palm nut
cracking machine exists, they are usually too expensive for local processors to
afford, as most of the machines are imported due to the lack/short supply of
locally fabricated palm nut cracking machine.

The
developed oil palm tree is typically single stemmed, around 20 m tall with a
stout trunk of around 75 cm in breadth, with an outside root framework. The
organic products (fruit) take around 5-6 months to develop from the onset of
fertilization to development.  The oil
palm organic product comprised of an external skin (exocarp), a mash (mesocarp)
containing the palm oil in a stringy framework, a focal nut comprising of a
shell (endocarp) and the bit which itself contains an oil (Udo et al. 2015).
The preparation of the palm natural product to get the palm kernel begins with
the extraction of palm oil from the palm organic product, the division of the
nuts from the fiber, drying the nuts, and afterward the popping of the nuts to
acquire the kernel which can then be handled to get palm kernel oil (Ismail
et al. 2015). Palm kernel oil discovers application in cleanser
producing enterprises, oil preparing businesses, nourishment handling ventures,
makeup enterprises and pharmaceutical ventures. Extraction of oil from palm
kernel is such a critical part of palm kernel processing, and as the palm oil
generation experiences a lot of mechanical improvement, the palm kernel oil
creation is still less motorized and this generation procedure really start
with the division of the fibre from the palm nuts from which kernel oil is
determined. Consequently, separating the palm nut to get the kernel is an
extremely significant part of kernel processing as the ability to crack open
the nut without causing harm to the kernel itself is important to limit waste, and
thereby increasing productivity.

The
palm organic product (Elaeis guineensis) stands out amongst the most imperative
wellsprings of oil for household and mechanical purposes in West Africa and the
whole world. As a drupe, it is comprised of three noteworthy layers: the
external layer known as epicarp; a beefy mesocarp from which palm oil is
removed and a hard endocarp (shell) which constitutes the nut (Okokon et al., 2015). The palm kernel is the
palatable seed of the oil palm organic product. The natural product yields two
unmistakable oils: palm oil and palm kernel oil. The palm oil is gotten from
the external piece of the natural product, while the palm kernel oil is gotten
from the nut. The oil palm tree is an enduring plant. It is initially from
Africa particularly the southern parts of Nigeria and Ghana (Ismail et al., 2015).

INTRODUCTION

Key words: Cracking, Development,
Evaluation, Machine, Palm nut

Palm nut cracking
machine is a mechanical device developed for the cracking of palm nut instead
of the traditional method. The traditional method involves raising a small
stone on a larger stone or any hard surface to crack the nuts placed in between
them. This method is tedious, time consuming and has a low production rate. The
cracking machine is developed using mild steel metal of 1mm thickness for the
hopper, angle iron of 1mm thickness for the stand, the cracking chamber
consists of a drum of 5mm thickness, the shaft of 39mm diameter, and the
cracking hammers made of mild steel metal plate of 10mm thick. The hopper has a
maximum capacity of about 0.02 m3. The inlet to the cracking chamber
is about 30mm wide. The machine is powered with electricity through an electric
motor of 1hp. The pulleys are 175mm and 80mm in diameter. The length of the
shaft bearing the cracking hammer is 300mm with 39mm diameter. The machine is designed
to operate at a power rating capacity of 420W. The machine cracks 1kg of palm
nuts 47.58 seconds and can crack 10.8 kg of palm nuts in 514 seconds. The
efficiency of the machine is averagely estimated to be 74.2%. The
throughput of the machine is determined to be75.6kg nuts/ hour. This mechanized
system of cracking is faster, less tedious with increased rate of production
compared to traditional (manual) cracking method.

ABSTRACT