Rieter

Cleaning

Index

It has to be kept in mind that impurities can only be eliminated from surfaces of tufts. Within a progressive line of machines it is therefore necessary to create new surfaces continuously by  opening the material. And even then the best blowroom line is not able to eliminate all, or even almost all, of the foreign matter in the raw material. A blowroom installation removes approximately 40 - 70% of the impurities. The result is dependent on the raw material, the machines and the environmental conditions. The diagram by Trützschler in Fig. 3 illustrates the dependence of cleaning on raw material type, in this case on the level of impurities.

It is clear from this diagram that the cleaning effect cannot and should not be the same for all impurity levels, since it is easier to remove a high percentage of dirt from a highly contaminated material than from a less contaminated one. Looking at the machine, the cleaning effect is a matter of adjustment. However, as Fig. 4 shows, increasing the degree of cleaning also increases the negative effect on cotton when trying to improve cleaning by intensifying the operation, and this occurs mostly exponentially. Therefore each machine in the line has an optimum range of treatment. It is essential to know this range and to operate within it.

In an investigation by Siersch  [3], the quantity of waste eliminated on a cleaning machine by modifying settings and speeds was raised from 0.6% to 1.2%: while the quantity of foreign matter eliminated increased by only 41%, the quantity of fibers eliminated increased by 240%. Normally, fibers represent about 40 - 60% of blowroom waste. Thus, in order to clean, it is necessary to eliminate about as much fibers as foreign material. Since the proportion of fibers in waste differs from one machine to another, and can be strongly influenced, the fiber loss at each machine should be known. It can be expressed as a percentage of good fiber loss in relation to total material eliminated, i.e. in cleaning efficiency (CE):

C_E = \frac {A_T -A_F}{A_T} \times 100

AT = total waste (%); AF = good fibers eliminated (%).

For example, if AT = 2.1% and AF = 0.65%:

C_E = \frac {2.1 - 0.65}{2.1} \times 100 = 69 \%

Fig. 3 – Degree of cleaning (A) as a function of the trash content (B) of the raw material in %

Fig. 4 – Operational efficiency and side effects