Some years ago there was no doubt that any self-respecting bulk grain enterprise made efficient air/screen precleaning of cereals in connection with intake prior to drying and storing.

In the course of time the need for precleaning has decreased to some extent in some countries, including Denmark. The two main causes are:

1. A rapid increase in the use of chemicals in the field, which has resulted in cleaner crops and a falling tendency to lodged grain, which again means easier harvesting and cleaner harvested cereals.
2. Newer types of combine harvesters clean the cereals better than old models.

Therefore, during recent year, there has been a tendency in these countries not to take precleaning in a traditional sense into account when establishing new plants.

The risk
As the drying capacity of the bulk grain enterprises is often insufficient to keep up with the intake of cereals in the harvest period, they often choose to store the cereals, although they are not sufficiently dry for storage. Airing of the cereals will prevent heating.

If unprecleaned cereals are stored, "dead areas" will easily arise, where the blowing through of air is inefficient because of local concentration of impurities. Consequently there will be a risk of local heating.

Which degree of precleaning
The need for precleaning varies from country to country. In some countries precleaning is performed to the full extent by air and screens, whereas other countries have stopped precleaning cereals and other crops.

In the areas where precleaning is required to the full extent, the following DAMAS machines are used, dependent on e.g. the need for capacity: SIGMA and VIBAM.

No or slight precleaning
As mentioned in the first main paragraph some countries, including Denmark, are inclined not to preclean at intake. Owing to the resulting risk, mentioned in the second main paragraph, we recommend in these cases:

PULCO
PULCO differs in important respects from traditional aspirators in its technical construction. Therefore the quality of the aspiration is also beyond all comparison.

PULCO offers the following advantages for the user:

1. Efficient aspiration, which means elimination of the risk of "dead areas" in the cereals and consequently the possibility of efficient airing and elimination of the risk of heating.
2. Space-saving and consequently more possibilities of positioning.
3. No vibrations with a resulting increased flexibility as to positioning and cheap installation.
4. Possibility of system with recycling air, which means:
   • Need for less air change in the room, which is important to achieve an acceptable temperature in the room in case of low outdoor temperatures.
   • Decimation of the quantity of excess air to central aspiration plant or the like.

5. Obsolescence-proof solution, which means that PULCO can be provided with supplementary screen cleaning (see below) if required later.
6. Inexpensive solution, which means that the "cost/benefit" relation will be very favourable.

Future
With the progressive environment consciousness and increased interest in ecological farming the years to come will probably see much more unclean grain fields than before. This will increase the need for highly efficient precleaning, not only by air, but also by screens.

If a customer who has installed a PULCO aspirator later also needs screen cleaning, well, then there is no harm done, as the PULCO is identical with the air section of our SIGMA planet drum separator. I.e. given sufficient space, it is possible to supplement the PULCO with the screen section of a SIGMA. The result is a complete and efficient air/screen cleaning function.

Back to the present
It is not to be recommended to omit precleaning with the resulting risk. Instead we recommend for the present that the need should be met with the obsolescence-proof PULCO.

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