Technical
article
Prillwitz SM (self-matting) milling rolls
test: Tests were carried out in 1998
in a 180 t / 24 h soft wheat mill in Poznan (western
Poland). Three pairs of self-matting rolls were
installed in roller mills, which had both pairs
of rolls working on the same passage. The trials
were therefore made on C2, C3 and C5. On one side
standard sandblasted rolls were installed (hardness
430-470 HB). On the other side the SM (self-matting)
rolls were installed. During the trials the basic
parameters of the mill, the wheat as well as the
products being obtained were unchanged. Trials
were continued and data collected over a period
of over 3 weeks.
Results:
1. Intensification of the milling process.
With a same gap setting on both sides the SM
rolls were producing slightly more flour. Taking
the B1 value as 100 % the increases obtain was
C2-2.1 %, C3-1.8%, and C5-1.3 %. In comparison
with the normal rolls the increased yield was
14%, 18 % and 23 % respectively. In the case of
the main fraction being produced –200 micron
– the quantities obtained using the SM rolls
were higher by 30%, 34 % and 37 % respectively.
This clearly shows that the milling process has
been intensified. The smaller the size of the
particles being milled and the greater the proportion
of bran they contain – the higher effectiveness
of the SM rolls. The intensification of the milling
process meant that one of two changes could be
made to the mill flows in existing mills.- Milling
results could be maintained at higher throughputs
( more product being fed onto the same length
of rolls )- fewer passages would be needed to
obtain high extractions of flourIn both cases
the end result should be an overall increase of
capacity of existing mills. The results obtained
in the mill in Poznan confirmed this. The capacity
and extraction levels were monitored over a period
of 2 years (1997 and 1998). In 1997 traditional
rolls on compression passages were used. In February
1998 all the traditional smooth rolls were replaced
with SM rolls. The quality of grain being processed
during the entire period was fairly uniform. The
milling process, the equipment installed and the
market situation were also similar during both
periods. The introduction of SM rolls was the
only major change made in the mill in 1998. Results
obtained during the entire 1998 showed that the
extraction of flour was 2.42 % higher then in
1997 and the capacity of the mill increased from
180 t / 24 h to 200 t / 24 h. Even if we assume
that some of the increase in extraction and capacity
were a result of other factors, there is little
doubt that the introduction of the SM rolls produced
a noticeable increase of both parameters.
2. Improved flour quality.
The flour produced has improved. The following
results were obtained.The level of sedimentation
(quality of gluten) rose by 3-5 pointsWater absorption
of flour increased by 0.8-1.4 %.The activity of
the alpha – amylase was unchanged.Tests
made in 1999 in Canada showed that the level of
protein increased by ca 0,25 % and base flours
were noticeable less speckled and lighter in colour.
In the tests in Poznan despite the 10 % increase
in the capacity of the mill the ash content is
practically unchanged. In Canada tests showed
that with a constant capacity of the mill the
ash contents fell by 0.16 %. 3. Lower consumption
of electric energy.
The energy consumption of the SM rolls in comparison
with standard rolls was lower by 2.5% -5.7 %.
In general the smaller the particle size of the
product being milled the lower the energy savings.
4. Lower milling temperature.
One of the characteristics of the smooth rolls
working on the compression passages is the relatively
high working temperature of the rolls. With the
SM rolls the working temperature of the rolls
was lower by 3.6-5.7 degrees C (6-10 degrees F).
Which in turn lowered the temperature of the product
by 2.5-3.4 degrees C (4-6 degrees F).
5. Lower maintenance cost.
For the past two years the rolls installed in
1998 have not required any maintenance as they
are still maintaining a “sandblast”
finish (May 2000). The results being obtained
have also not shown any noticeable deterioration.
During the last four years 1999 – 2003 over
2000 Prillwitz SM rolls of various lengths and diameters.
have been installed in mills in Poland, Germany,
The Netherlands, Italy, United Kingdom, USA, Canada
, Argentina, Chile, Peru, Colombia, India, Bangladesh
the Philippines Up till now the feedback we have
received from all these mills confirm the benefits
of the SM rolls in the milling process and their
superiority over the conventional sand blasted
milling rolls.
Prillwitz is carrying out further work on the development
of the SM rolls. Thanks to the co-operation of
Polish metallurgical institutes and the Central
Laboratory of Grain Processing in Poznan and in
Warsaw we are also learning more about the potential
benefits of this product. Prillwitz commitment
to quality and technological improvment is once
again stressed when it comes to choose those products
it comercialize under representation.
Milling rolls
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