Feed manufacturers should not have difficulty meeting requirements established by the regulatory
agencies if they adhere to rigid cleaning and operational procedures. When micro-ingredients and
premixes are being added, dust collection systems or other air suction systems should be carefully
balanced such that a minimum of air is drawn from the mixer. Fortunately, regulations have, in the
past, provided a broad range of concentrations in between which the feed manufacturer may operate.
However, in light of todayâ€™s improved detection techniques and consumer concern and awareness
of potentially harmful drug residue problems, such allowable variations are being reduced. Most feed
producers will not be satisfied with producing a feed having as broad a range as was once permitted.
The mixer should, of course, have good mixing efficiency, and allowing for sufficient time to thoroughly
blend the feed is an absolute MUST.
When using antibiotics and other micro-ingredients in mixes which are prepared intermittently for
poultry, swine, sheep, and cattle, the manufacturer should be sure:
1. That the mixer internals are clean and that it is cleaned out thoroughly between the mixing of the
different rations. This means stopping the mixer and removing excess materials in filler tubes and
2. That the mixer is grounded to bleed off static electricity.
3. That regulatory requirements are followed for:
a. Cleanout of accessory equipment
c. Recheck of ingredient weight and inclusion
d. Sampling, etc
Operational Comparison Of Standard Horizontal Batch Mixers And Drop-
Bottom Horizontal Batch Mixers
Operational procedures of the drop-bottom unit is very much like the operation of a normal single
or multiple discharge mixer, but it has an added advantage in that it discharges most rapidly; as fast
as ten seconds for opening, discharging, and closing of doors. The mixer is completely emptied and
clean with very little possibility of contamination. This rapid discharge feature reduces the total mixing
cycle time, and, since the feed mill capacity is based largely on mixing capacity, can possibly increase
plant capacity through savings in discharge time.
Sequence Of Ingredient Addition To Drop-bottom Mixers
We know that there is a decided advantage in following a particular sequence when charging
ingredients into the mixer. With the drop-bottom feature you do not have discharge pockets that can
possibly catch a few pounds of the first ingredient that is put into the mixer and hold it unmixed.
There are no pockets, but a smoothly contoured bottom formed to the contour of the ribbon itself.
This further reduces the possibility of segregation and "dead spots" .
Cleaning And Maintenance Requirements
Periodic cleaning of the drop-bottom mixer is no more difficult than the normal periodic cleaning of
a standard single or multiple discharge mixer. This can be accomplished through the top or by installing
access panels in the side of the catch hopper below the mixer and cleaning it from the bottom with
the doors swinging open. Normal cleaning of this unit in dry feed mixing consists of removal of strings
that might catch on the ribbon assembly. The only other additional maintenance that would be required
would be on the air cylinders themselves and, with proper installation of air supplies with traps and
filters, this should be no problem at all.
The self-cleaning non-contamination feature is a basic point in favor of this particular type of unit.
The possibility of contamination must always be considered when using drugs, and we know there
are many places in the feed plant where contamination can occur. By eliminating the problem here,
one contamination worry is removed.
I might mention, going a bit further, that if you are using bucket elevators to elevate your mixed feed,
you can eliminate another source of contamination by equipping your elevator legs with automatic
boot cleanout units. These, too, can be integrated into your semi- or fully- automatic batching system
to cycle between each batch if desired. Another way to reduce contamination is to use a gravity flow
system wherever possible.
With todayâ€™s high energy specialized feeds, with the necessity for feed mill efficiency, and with
contamination being the problem it is, we feel that the drop-bottom mixer will prove more and more
important in modern feed manufacturing operations.
Other Parts to this Article
A Perspective On Mixing And Mix Uniformity: Part 1 - Introduction, Current Situation, Value Of Feed Uniformity
A Perspective On Mixing And Mix Uniformity: Part 2 - Equipment Properties, Current and Future Aspects, Mixer Testing, Result Interpretation, Assay Selection
A Perspective On Mixing And Mix Uniformity: Part 3 - Mixing Equipment, Horizontal Batch Mixer, Short-Cycle Mixer
A Perspective On Mixing And Mix Uniformity: Part 4 - Problem Ingredients, Discharge And Cleanout Of Mixers, Liquid Addition
A Perspective On Mixing And Mix Uniformity: Part 6 - Summary