E/LMS 31200: Grain Conditioning and Cleaning System

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Foreign materials and dust must be removed to eliminate problems further down the grain storage and handling system. A grain conditioner, or scalper, removes foreign particles, weed seeds, small size grain, straw and husk. A dust extraction and collection system prevents dust entering the environment. All foreign metal objects must be detected and removed before they can cause damage. The main function of a cleaning or conditioning machine is to remove any large impurities, e.g. stones, stalks, leaves, ropes, etc. from the product during the intake process. This should be done at such a rate that the intake tempo is not slowed down.

Rotary Screen Air Cleaner is made up of a cylinder made of perforated steel sheets or spirally wound wires. The cylinder is mounted on a shaft suspended in bearings about which it slowly rotates when in operation. The perforations on the cylinder are of different sizes along the cylinder length. The inclination and rotational speed of the cylinder are adjustable. A fan, to provide aspiration is mounted on the cleaner – with facility for adjusting the air effect. Adjustment of air volume, speed of rotation of cylinder, feed, and moisture content all influence the performance of the cleaner.

Click here to view a video that demonstrates the rotary cleaner.

Flat Screen Air Cleaner consists of a screen boat with two screens mounted in it. The screen boat is connected to the drive mechanisms regulated by cams. The perforation on the top screen is larger than the grain while the perforation on the bottom screen is smaller than the grains. The screens are mounted inclined. On top of the screen boat is a feed metering device below which is a scalperating screen inclined and discharging onto the top screen. A fan is mounted on top of the cleaner. The grain to be cleaned is fed into the cleaner from an inlet hopper into the feed roller which regulates and spreads the grain evenly across the full working width of the machine.

First the grain is fed onto the scalperating screen which separates the large objects such as piece of cobs, straw, stones, twine and channels it to the side. The grain, then flows to the end of the scalperating screen and falls on to the top screen. The holes in the top screen allow grain and small particles to fall through onto the bottom screen. The large impurities are retained on the top screen and are channelled to the side and discharged. The holes in the bottom screen let all fines and other materials fall through onto a blank and discharge while the clean grain is retained on the bottom screen and flows to the end edge into the clean grain chute. As grain falls through the cleaner right from the feed miller and into the screens, the grain is aspirated, and all light particles and dust are removed by suction.

Click here to view a video that demonstrates the flat screen air cleaner.

Two types of pre-cleaning machines:

Impure Product Flows into a Moving Roll Sieve or Drum Screen

The product is fed into the interior of a rotating drum sieve in a closed casing via an inlet spout. It then revolves so that the coarse impurities are guided by means of the rotary effect as well as a guiding spiral of approximately 70mm near the front outlet, to be discharged through an outlet channel and fed via ducting to the tailings collection room.

The drum sieve is made of perforated sheet metal which is kept open by a scraper brush and has a screen size that varies according to tonnage requirements but is normally approximately 12 – 25mm in size. Smaller impurities as well as fines drop through the sieve and is funneled to the screening collection room. Only a very small amount of aspiration is required on this type of machine as it is totally enclosed.

Impure Product Flows Over the Sieve or Screen

In this case, product flows over a combination of sieves which separate the large-, smaller impurities from the product. Impurities is conveyed to the various collecting bins in the screenings room. With this type of machine, the speed of the sieve as well as the even distribution of the product over the sieves are of great importance.

In order to ensure even distribution of product over the sieves, a buffer bin above the machine is used from where the product is divided into two and then flows via two chutes, each provided with an adjustable slide over the sieve.

Even distribution is important as a stream of product which is too thick usually causes the product to “ride” over the sieves together with the impurities and then end up in the screenings. This is of course something that can result in large financial losses. The machine is also equipped with two weight-adjustable flaps which can assist in distributing the product evenly over the sieve area. Provision is also made in the machine for a discharge screw conveyor which conveys all strings and other types of waste to a separate outlet. A separate aspiration system, complete with fan and cyclone, is also provided with each machine. Separate drives are provided for the aspiration system and the sieve drums.