World Grain - October 2008 - 75

FEEDOPERATIONS

downloaded formulations storage and
parameters that are set externally for
liquid addition, mixing times, routing
to press and finished product bins, are
the norm in almost every mill. However, there are several modifications
available to most systems, many of
which can show enhanced profitability
for most mills. Blending accuracy, automatic adjustment of material in flight
tolerances, and statistical analysis of
actual ingredient inventory usage all
help to maximize weighing accuracy
and inventory controls.
Stochastics is a system of analyses
that some mills have adopted in recent
years, but it is mostly suited to mills
that manufacture a limited range of
feeds. It is ideally suited to mills making four or five poultry diets to supply
a given outlet chain, where weight for
age is crucial and can be varied according to how well finished chicken meat
sales are progressing. Being able to
dial in and adjust energy value in the
blending system and come out with an
instant change in the feed being placed
before the birds later in the day is a
luxury enjoyed by only a few, but one
that pays handsome dividends where it
is available.
Most millers use their formulation
package to reformulate monthly, some
weekly and a few daily. Formulae are
usually downloaded directly to the mill
batch control system either by direct
link or by insertion of a CD into the mill
PC. Whichever way data is transferred,
the methodology allows for a quick
change in recipes or formulations. By
the same token, mixing parameters can
also be changed quite quickly. Mixing
times rarely vary and most millers adopt
a three- or four-minute dwell time in a
horizontal mixing system with bomb
doors for effective cleanout.
Three-tier mixing systems are the
norm, especially where more than one
pelleting line is being fed. Some mills
operate with multiple mixing lines, but
these are invariably where multiple species are being fed through the one mill.
These types of mills are becoming few
76

and far between, principally because of
the cross-contamination risks associated
with multiple ingredients being processed through the same facility.
Most, if not all, mills have the facility for retaining detailed batch records,
showing the desired ingredient inclusion and the actual weight of inclusion
of each and every raw material into a

Incorrect blending and inaccurate mixing can be expensive,
and you must be on top of
the job at all times to survive
these difficult times of world
economics.

batch. Hand-tipped ingredients and micro additions are no exception, and in
these days when traceability is all important, batch numbers, serial numbers
and full details of ingredient origin can
be retained for several years on either
CDs or other simple storage devices.
Whatever your blending and mixing
system comprises, there will be a need
for effective and regular calibration of
scales, pumps, meters and all other control devices, including electrical timers.
Usually a simple manual schedule acts
as a prompt for us to carry out such routine calibrations, but increasingly the
use of automated calibration records are
being generated. These are useful and
can be done far more regularly than with
manual calibration checks.
The generation of "as found" data is
also becoming automated, precluding
the possibility of erroneous mixes being
dispatched without knowledge. Recall
procedures are becoming more transparent as end users of processed meat
become more sensitive to the public demand for perfect products.
USE OF PREMIXERS
With mixers also becoming more efficient in their design and mixing times
being reduced, there is a trend toward
premixing some ingredients, particu-

larly trace minerals and vitamins and
the smaller micro-ingredients that you
do not want to process through the
hammermills that are incorporated into
post-grinding systems.
The use of premixers and screens
before hammermills leads to a slightly
more sophisticated blending system
flow, but automated controls assist with
simplifying the controls and increasing
accuracy of mix and blend operations.
With the trend toward split mixing, it
does enable the miller to more accurately blend ingredients of much better
aligned particle size spectrums. This
subsequently assists with pellet mill
performance and cooling as will be discussed in part three of this series.
Liquids addition is still done at the
mixer in most mills, although the trend
toward splitting the addition of fats
and fat blends between the main mixer,
where it is incorporated internally to the
meal, and spraying a proportion externally to the pelleted feed continues to
be the source of debate. Where pellets
are coated with fats, the use of small
batch mixers is becoming more prevalent. Swift but gentle mixers mounted
on load cells in order to blend both fat
addition and pellets by weight have
largely replaced the volumetric systems
you first saw when fat spraying became
a feature of feed milling operations.
The use of stainless steel is the norm
in mixers that are used where corrosive
fats and other liquids are incorporated
into rations, but mild steel mixers can
still be seen in many mills. Stainless
steel price differentials are not what
they were a few years ago, and almost
all the mixers are now made of stainless steel.
Bearings generally have caused little
trouble, largely because of the slow
speed at which mixers operate. Gearboxes have had their usual leakage
problems, generally associated with the
pressures they are put under when moving several tonnes of meal around in a
closed environment. Bomb doors have
sorted the problems of mixer hang-ups,
and cleaning mixers out is almost a
October 2008 / World Grain / www.World-Grain.com
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World Grain - October 2008

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