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10/03/2006 - Chances of cleaning contamination (5 of 6)

5.Practical experiences

Theoretically it should be claimed that a sorter detects and eliminates all impurities.

This is, however, neither technically possible nor makes sense.

Technically there are two limits:

- the maximum frequency of air blasts which still guarantee the safe removal of the detected contamination

- the smallest contamination which can be detected.

It is obvious that the smaller the impurity is which can be detected, the more often it will occur. Soon the limit will, however, be reached which not any longer permit its secure removal.

5.1 Limit of secure removal

According to practical experiences 700 contaminations per hour are the maximum which can be reliably removed by individual air blasts. If this maximum is exceeded the blowing impulses following shortly one after another generate continuous air turbulences which will not allow any more a secure elimination. As a result a part of the impurity blown out will be rinsed back into the transport channel.

If 700 air blasts per hour are the limit for a safe removal, the question comes up if this is enough for all the contaminations to be found in the raw cotton. The answer depends on the degree of contamination. Most cotton produced in South Asia will, however, clearly exceed this limit.

Picture 5: Double testing

5.2 Limit of possibility of detection

In view of these conditions it doesn’t make sense to detect smallest impurities. In technical view detection in mm-range would certainly be possible. The problem, however, is that the number of detected impurities increases in such a way that their removal cannot be guaranteed any longer.

Due to this limitation the SORTER of Loptex focuses on the contamination with a size of about 1 square centimetre. The dimension itself, however, is not the only criterion. With the optical system besides dimension the feature brightness has also to be considered.

Dark impurities will be identified even though they may be smaller. In the case of the acoustic system besides dimension the feature surface is important. The denser the surface is the more the sound waves are reflected.

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	NEWS 10/03/2006 - Chances of cleaning contamination (5 of 6) 5.Practical experiences Theoretically it should be claimed that a sorter detects and eliminates all impurities. This is, however, neither technically possible nor makes sense. Technically there are two limits: - the maximum frequency of air blasts which still guarantee the safe removal of the detected contamination - the smallest contamination which can be detected. It is obvious that the smaller the impurity is which can be detected, the more often it will occur. Soon the limit will, however, be reached which not any longer permit its secure removal. 5.1 Limit of secure removal According to practical experiences 700 contaminations per hour are the maximum which can be reliably removed by individual air blasts. If this maximum is exceeded the blowing impulses following shortly one after another generate continuous air turbulences which will not allow any more a secure elimination. As a result a part of the impurity blown out will be rinsed back into the transport channel. If 700 air blasts per hour are the limit for a safe removal, the question comes up if this is enough for all the contaminations to be found in the raw cotton. The answer depends on the degree of contamination. Most cotton produced in South Asia will, however, clearly exceed this limit. Picture 5: Double testing 5.2 Limit of possibility of detection In view of these conditions it doesn’t make sense to detect smallest impurities. In technical view detection in mm-range would certainly be possible. The problem, however, is that the number of detected impurities increases in such a way that their removal cannot be guaranteed any longer. Due to this limitation the SORTER of Loptex focuses on the contamination with a size of about 1 square centimetre. The dimension itself, however, is not the only criterion. With the optical system besides dimension the feature brightness has also to be considered. Dark impurities will be identified even though they may be smaller. In the case of the acoustic system besides dimension the feature surface is important. The denser the surface is the more the sound waves are reflected. Torna all'elenco NEWS