hUNGARiAN AGRicUltURAl RESEARch

Table 2: Some recommendations based on the Hungarian Feed Codex published in 1990
Feed name Standard Particle size ranges
Feeds of animal origin MSZ 21340-86T 80% below 2 mm
20% between 2–3 mm
Feed meal from wheat MSZ 08-1358-81 100% below 0.67 mm
Ground rye for feed purposes MSZ 08-1367-81 100% between 0.32–1.6 mm
Feed meal from corn Feed Codex I. ’84 80% below 0.8 mm
Table 3: The effect of particle size on feed conversion of pigs [6]
Particle size (mm)
in order to ensure the improved
utilization and better homogeneity
of the feed mix.
In the case of a traditional
milling of agricultural products
farms apply the accustomed old
‘well proven’ settings with their
existing devices. However, in
connection with the changes that
have taken place in the energy
sector and in the field of food
safety, it is worthwhile to consider
the setting up of a more
economical and more flexibly
applicable system which can be
integrated with the existing one.
At greater farms, the electronic
machinery designed earlier with a
very great factor of safety requires
considerable financial resources in
advance on an annual basis. With a
minimal investment, regular
monthly expenses can be reduced
by equipping electric motors with
frequency drives. Thereby a softer
start and a controllable input/
output performance can be
achieved. There are a lot of
manufacturers on the market
offering these products in wide
ranges of performance.
In the case of conventional
arrangements a suitable screen is
fitted prior to the onset of milling
in order to set the output, i.e. the
desired particle size. For the
Feed conversion efficiency (kg/kg)
> 1 3.00
0.9–0.7 2.92
0.7–0.6 2.76
prevention of eventual
overloading during operation the
position of the bolt lock is
modified at the place where the
material enters, with the
intervention of the operator.
The modification of revolution
number is not a customary solution
in the field of milling of
agricultural products. Our
investigation aims at
demonstrating that through the
alteration of the peripheral
hammer speed the same particle
size can be produced as with the
traditional change of screen. For
the purpose of the measurements
P elec. [W]
a f0 [m 2 /kg]
w [%]
0 [kg/m 3 ]
size
…
Elec.
Motor
feeder
bolt lock
n 1
[rpm]
A incoming [m 2 ]
Drive
mechanism
the existing hammer mill was
equipped with measuring devices.
The input and output parameters of
the experiment are illustrated in
Figure 1. [4]
The original design was
completed with a frequency drive,
marked in bold in the figure,
suitable for changing the number
of revolutions, with devices
signalling the number of revolutions
(n 1 , n 2 ), a torque meter (M 2 ),
a thermometer (T), a bolt lock
position transducer (A incoming)
and with a load cell (m) for
measuring the weight of the meal
coming out. The conditions of the
gravity feed and discharge were
not changed and I used a sieve
with the same mesh size for the
same series of experiments.
Measurement results were
recorded using a data collector
measuring over eight parallel
channels with a high speed
Gear : v-belt
Continuously variable: frequency drive
M 2 [Nm]
n 2
[rpm]
(input of material)
Q 1 [kg/s]
Hammer
mill
Figure 1: Design of the experimental apparatus, input, output
variables and parameters
Q 2 [kg/s]
T 2 [ o C]
m [kg]
a f [m 2 /kg]
sieve analysis
Replaceable screen
size
live surface
profile
14 Hungarian Agricultural Research 2009/3–4