Journal of Engineering Research, Vol. 14, No. 1, March 2009. J.I. Orisaleye, S.J. Ojolo
and A.B. Fashina
DESIGN AND DEVELOPMENT OF A LIVESTOCK FEED PELLETING MACHINE
By
J.I. ORISALEYE*, S.J. OJOLO**, A.B. FASHINA***
* Mechanical Engineering Department, Lagos State University,
Epe Campus. Lagos. Nigeria.
** Mechanical Engineering Department, University of Lagos, Lagos. Nigeria.
***Agricultural Engineering Department, Ladoke Akintola University of Technology, Ogbomoso.
Nigeria.
ABSTRACT
Feeding pellets to livestock is advantageous to both the livestock and its farmer as it supplies the
required nutrients to the livestock and is also economical. However, livestock feed pelleting equipment
are known to be expensive and unaffordable particularly to the local farmer. A prototype of the pelleting
machine was designed and developed for affordability. The machine was also tested to evaluate its
performance. The machine consisted of a screw conveyor, die, barrel and hopper. It can be driven by an
electric motor or a prime mover. The machine was tested with broiler’s mash and at different levels of
moisture content using 500, 750 and 1000 cm3 each of water and starch binder as preconditioners. The
best pellets were formed using 750 cm3 of either starch or water. The average specific energy
consumption when 750 cm3 of starch binder was used was 0.69 kWh/kg while it was 0.93 kWh/kg when
water was used as preconditioner. The density of the pellets varied between 0.7 and 1 g/cm3. This
machine can be manufactured at a local machine shop for small-scale livestock farmers in developing
countries.
Key words: Development, livestock feed, pellets, machine
1.0
INTRODUCTION
Feed represents the major cost to animal
production. Thus, the efficiency of its use, or
quality control, can have a considerable impact
on the performance of an enterprise (Halley and
Scoffe, 1988; Hasting and Higgs, 2000; Elmer,
1990).
The value of a feed is dependent on how much
particular nutrients in the feed that the animal is
able to utilize to meet the requirements of
various body processes (Halley and Scoffe,
1988). The aim of processing livestock feed is
to increase the efficiency of utilization of the
nutrients (Tillman and Waldroup, 1986;
Kabuage, 1996).
For many years, simple and common techniques
have been used in processing livestock feeds,
which are basically cereal grains and their byproducts. They have been classified into hot or
cold processes depending on the requirement of
heat. Another classification is based on whether
the process is wet or dry. The techniques that
have been in use are grinding or particle size
reduction, crushing, rolling, steam-flaking,
micronisation, roasting, chopping, cracking or
crimping, popping, hot and cold pelleting
(Halley and Scoffe, 1988; Harris, 1990;
McDonald, 1987; FAO, 1997; Hasting and
Higgs, 2000).
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Journal of Engineering Research, Vol. 14, No. 1, March 2009. J.I. Orisaleye, S.J. Ojolo
and A.B. Fashina
Studies have revealed that feeding certain
livestock with pellets have great benefits.
Kabuage et al. (2000) noted that pelleting
amaranth diets improved the nutritional value
and was beneficial in improving growth of
chicks. Salmatec (2000) also stated that highly
compressed pellets facilitate storage and
transportation, they save space, extend storage
life and permit large quantities to be carried
economically. Galen et al. (2000) pointed out
that pelleting feeds produced many traits desired
by livestock producers which include decreased
feed wastage, reduced selective feeding,
improved feed efficiency, better handling
characteristics, destruction of undesirable
micro-organisms and increased bulk density.
They added that qualities added to the livestock
feed include complete pasteurization, improved
pellet quality (better durability and fewer fines),
increased feed utilization, increased starch
gelatinization and production of by-pass fat and
by-pass protein. Their views are shared by
McDonald (1987), MikroTechnik (2002),
Halley and Scoffe (1988), Salmatec (2000),
Eugene (2002) and FAO (1997).
The pelleting equipment have been classified
into two, based on the type of die: the disc die
and the ring die pelleters (FAO, 1997).
Generally, the pelleting equipment consist of a
pelleting device, a steam generator, an oil and
molasses doser, a cooling device, a separator
and a sieve (Galen et al., 2000).
It has been pointed out that the mean particle
size or grind of ingredient, and formulation play
a major role in producing high quality pellets
(Galen et al., 2000; FAO, 2000). However, there
is a limitation to the use of the livestock feed
pelleting machine because of the high cost of
the equipment for pellet processing (FAO, 1997;
Kabuage et al., 2000; Eugene, 2002). Hence, the
local livestock farmer, in Nigeria in particular,
cannot afford to utilize the sophisticated
livestock feed pelleting machine. This work
aims at designing and developing a livestock
feed pelleting machine and evaluating its
performance.
2.0
MATERIALS AND METHODS
2.1
Components
Description
and
Specifications
The parts that make up the livestock feed
pelleting machine are the frame, barrel, hopper,
screw conveyor or auger, die, pulley and motor.
The machined components were made of mild
steel (Figure 1).
Figure 1: Livestock feed pelleting machine
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Journal of Engineering Research, Vol. 14, No. 1, March 2009. J.I. Orisaleye, S.J. Ojolo
and A.B. Fashina
2.1.1 The Frame
The frame acted as a support to other
components. It was a rigid structure and was
designed to withstand dynamic stresses. Welded
to the base was the bearing support. The barrel
was also welded to the vertical part of the frame.
2.1.2 The Barrel
The barrel is a cylinder with internal diameter of
80 mm and thickness of 5 mm. It has a length of
300 mm. A flange was welded to the end of the
barrel to support the die plate.
2.1.3 The Hopper
The hopper is a funnel shaped frustum cut out of
a square pyramid. The height of the frustum is
150 mm and it has a square top of length 200
mm.
2.1.4 The Die Plate
The pelleting die is required to restrict the flow
of feed material and provide the cylindrical
shape of the pellet. The die plate had a thickness
of 5 mm. The effective diameter of the die plate
was 80 mm. Thirty-six die inserts of 8 mm were
drilled into the plate.
2.1.5 The Screw Conveyor
The screw conveyor was a worm wound round a
cylindrical shaft. The maximum outer diameter
of the worm was 78 mm to give clearance
between screw and barrel. The screw conveyor
was carried on a solid shaft of 25 mm which is
driven by a pulley.
(Singh, 2003)
2.2
DESIGN CONSIDERATIONS AND
SPECIFICATIONS
2.2.1 The Screw Conveyor
The parameters considered in the design of the
screw conveyor were obtained from design
specifications and relevant tables which give
parameters corresponding to the nominal screw
diameter and the material to be pelleted (the feed
in this case). The parameters obtained were
(Singh, 2003):
Nominal screw diameter, D = 80 mm
Length of the Screw Conveyor, L=300 mm
Pitch of the Screw, s = 80 mm
Maximum speed of screw, n = 170 rpm
Solid shaft diameter, d = 25 mm
Loading efficiency,  = 0.25
Friction factor for material,  = 0.6
Factor of inclination, C = 1 for horizontal
conveyors
Material Factor, Wo = 4
Angle of inclination of screw to the horizontal, 
=
Maximum density of material to be pelleted (the
feed),  = 800 kg/m3
1
(100%
Effeciency of gear reducer,  =
efficiency assumed)
The capacity of the screw conveyor was
calculated using:
The power required to drive the screw was evaluated using:
(Singh, 2003)
Sin = 0;  = 1. Hence,
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Journal of Engineering Research, Vol. 14, No. 1, March 2009. J.I. Orisaleye, S.J. Ojolo
and A.B. Fashina
The load propulsion speed is
(Singh, 2003)
The load per meter length of the screw is
(Singh, 2003)
The axial thrust experienced by the conveyor was evaluated by
(Singh, 2003)
2.2.2
Shaft Design
For the rotating shaft, pure torsion is assumed. Hence, the maximum shear stress due to torsion and the
angle of twist are considered.
(Burr, 1982; Khurmi and Gupta, 1979)
Diameter of shaft
= 0.025 m
Active length of shaft = 0.34 m
Maximum stress due to torsion is
(Burr, 1982; Khurmi and Gupta, 1979)
Angle of twist of the shaft is
(Burr, 1982; Khurmi and Gupta, 1979)
2.3
Testing of the Livestock Feed Pelleting
Machine
The livestock feed pelleting machine was
powered by an electric motor which rotated the
shaft carrying the screw conveyor. The rotation
of the shaft is such that the screw conveyor
moves the feed towards the die.
The feed was fed through the hopper and is
carried through the barrel length by the screw
conveyor. Between the screw conveyor and the
die is a space which allows for caking of the
feed. The feed then passes through the die where
the cylindrical shape of the pellets is formed.
2.4
Test Procedure for the Livestock Feed
Pelleting Machine
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Journal of Engineering Research, Vol. 14, No. 1, March 2009. J.I. Orisaleye, S.J. Ojolo
and A.B. Fashina
The livestock feed pelleting machine was
powered using a 3 kW electric motor and was
tested to determine the output of the machine and
quality of pellets produced by the machine under
varying conditions. The test materials were
Broiler’s mash, which was the feed mix used,
water and cassava starch. Cassava starch was
used as a substitute for molasses, which was to
serve as binder.
2.4.1
Procedure for Testing using Water
1.
Three parts of feed mix, each 1 kg, were
prepared.
2.
500 cm3 of water was added to one part
and was thoroughly mixed.
3.
The machine was powered and the moist
feed was fed through the hopper
gradually.
4.
The pellets resulting were collected on a
tray and dried.
5.
Ten pellets selected randomly were
weighed and their dimensions were taken.
6.
The test was repeated for the other two
parts using 750 and 1000 cm3 of water
respectively.
4.
500 cm3 of starch was added to one part
and was thoroughly mixed.
5.
The machine was powered and the moist
feed was fed through the hopper
gradually.
6.
The pellets formed were collected on a
tray and dried.
7.
Ten pellets selected randomly were
weighed and their dimensions were taken.
8.
The test was repeated for the other two
parts using 750 and 1000 cm3 of starch
respectively.
2.5
Pelleting
Parameters
Machine
Operation
The throughput or production rate of the
machine was calculated using:
The specific energy consumption of the machine
was evaluated using
2.4.2 Procedure for Testing using Starch as
binder
1.
100 g of starch was diluted in water at
room temperature and stirred until a
uniform mix was achieved.
2.
Hot water at 100 oC was added to the mix
and stirring was continued until the starch
mixture becomes viscous.
3.
3 parts of feed mix, each 1 kg, were
prepared.
3.0
RESULTS AND DISCUSSIONS
3.1
Results
The summary of results from the testing of the
livestock feed pelleting machine are presented in
Tables 1 and 2. Table 1 shows the average
length, diameter and masses of the samples of
pellets selected at random. Table 2 shows the
mass of pellets produced, time taken, throughput
and specific energy consumption of the machine.
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Journal of Engineering Research, Vol. 14, No. 1, March 2009. J.I. Orisaleye, S.J. Ojolo
and A.B. Fashina
Feed mix with
Table 1: Average dimensions, mass and density of samples of pellets produced by the Livestock Feed
Pelleting machine.
Average
Average
length
(mm)
Mass of 10
samples (g)
Average
mass (g)
Average
density
(g/cm3)
Length to
diameter
ratio
Diameter
(mm)
500 cm3
of starch
24.935
6.604
6.70
0.670
0.78
3.8
750 cm3
of starch
16.580
6.435
5.10
0.510
0.95
2.6
1000 cm3
of starch
12.485
5.715
4.95
0.495
1.55
2.2
500 cm3
of water
23.200
6.105
4.40
0.440
0.65
3.8
750 cm3
of water
17.105
6.440
3.85
0.385
0.69
2.7
1000 cm3
of water
No pellets formed
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Journal of Engineering Research, Vol. 14, No. 1, March 2009. J.I. Orisaleye, S.J. Ojolo
and A.B. Fashina
Table 2: Summary of test for each part of feed mix fed into the machine
Starch
Water
1st part
2nd part
3rd part
1st
part
2nd part
3rd part
1
1
1
1
1
1
Quantity of starch/water
added (cm3)
500
750
1000
500
750
1000
Mass of pellets formed
(kg)
0.90
0.95
1.01
0.90
0.90
0.95
Mass of unpelleted feed
in the caking section
(kg)
0.13
0.10
0.05
0.10
0.10
0.05
Time taken (hr)
0.50
0.22
0.14
0.48
0.28
0.06
Capacity / Throughput
of the machine (kgh-1)
1.80
4.32
7.21
1.88
3.21
No pellets
formed
Specific Energy
Consumption (kWhkg-1)
1.67
0.69
0.42
1.60
0.93
0.19
Mass of feed used (kg)
3.2
Discussions
When starch was used as binder, the pulse of
feed through the die was generally smooth for all
mixes as against when water alone was used to
condition the feed. The pellets formed with
starch binder were smooth and brightly coloured
but those formed with water were scorched and
pale. This was due to the friction and the heat
generated during the process which was higher
with just water being used as preconditioner.
This was evidenced by the temperature around
the caking section which was relatively hotter
when water was used as preconditioner than with
starch.
The pellets with 500 and 750 cm3 of starch or
water were properly formed. However, when
1000 cm3 of water was used, no pellets were
formed. This was due to the excessive moisture
in the feed which overcame the required friction
needed as feed passed through the die. Hence the
feed could not be caked as there were no
restrictions to keep it in the caking section. In
addition, the pellets derived when 1000 cm3 of
starch was used were poorly formed. This was
also due to the same reason as for 1000 cm3 of
water. Pellets were formed though, probably due
to the binding effect of the starch on the feed.
An acceptable standard by FAO (1996) proposes
that good pellets which are properly formed have
their lengths to be about two and a half times
their diameters. This was particularly so for
pellets formed using 750 cm3 of water as
preconditioner and 750 cm3 of starch as binder.
The length to diameter ratio was higher when
500 cm3 of either starch or water was used and
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Journal of Engineering Research, Vol. 14, No. 1, March 2009. J.I. Orisaleye, S.J. Ojolo
and A.B. Fashina
lower when 1000 cm3 of starch was used. The
results also show that the pellets formed using
binder were generally denser than those formed
when water was used as a preconditioner. This
may probably suggest the advantage of using a
binder.
When the feed was pelleted at sufficient and
reasonable moisture content, say 750 cm3 of
starch or water, it was observed that the specific
energy consumption was lower with starch as
binder. It was also observed that the throughput
of the pelleting machine that produced
acceptable pellets was higher when the starch
binder was used. Also, when a higher volume of
binder was used, the specific energy
consumption was reduced but at the expense of
the quality of the pellet as indicated earlier. This
is also true with using water as preconditioner.
The higher energy consumption was also noticed
in the response of the electric motor when the
machine was loaded.
The density of pellets produced varied between
0.7 and 1.0 g/cm3 which is higher than 0.5 to 0.6
g/cm3 obtained by Hasting and Higgs (FAO,
2008) and 0.55 to 0.65 g/cm3 obtained using a
typical Universal Pellet Cooker (Galen et al.,
2008). It, however, corresponds with 0.82 to 0.91
g/cm3 obtained in a design by Guillermo et al.
(2002).
The average capacity of the machine, taken at a
moisture content of 750 cm3 of starch or water,
was 4.32 kg/h when starch was used as binder
and 3.21 kg/h when water was used to
precondition the feed. This was much lower than
400 kg/h obtained by Guillermo et al. (2002).
Pelleting mills of various capacities (100, 250,
500, 650 kg/h) have been developed by
Zhecheng (1996). Groesbeck et al. (2007)
obtained an average capacity of 1200 kg/h. The
average specific power consumption with 750
cm3 of starch was 0.69 kWh/kg and 0.93 kWh/kg
with water as preconditioner. This is higher than
0.14 kWh/kg obtained by Rose and Miller
(1973). The total energy expended by a machine
used by Groesbeck et al. (2007) was less than
0.01 kWh/kg. The low capacity and high specific
power consumption may be improved with
accessories like the steam generator, oil and
molasses doser (FAO, 1996) and also with the
addition of additives like glycerol and soy oil as
was observed by Groesbeck et al. (2007).
3.3
Conclusion
A livestock feed pelleting machine has been
developed for the use of the local small scale
farmer. The machine has a capacity which suits
its purpose but can be improved and modified to
reduce the specific power consumption. The
machine can be fabricated affordably at small
workshops or machine shops in developing
countries.
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