BS ISO 2648 pdf free download
BS ISO 2648-2020 pdf free download.Wool – Determination of fibre length distribution parameters – Capacitance method.
In the analogue system, the record is a galvanometric recorder, which automatically traces the cumulative Hauteur diagram on squared paper during measurement.
In the digital system, the data are captured by a computer which is capable of outputting the results to either the screen or to a printer. The diagram ordinate gives the percentage of fibres (biased by crosssection) of length greater than the length indicated on the corresponding abscissa. (The percentage by cross-section is very close to the percentage by number).
5.2 Test specimen holder.
5.3 Extractor system.
5.4 Restraining strip.
6 Conditioning and testing atmosphere
6.1 Conditioning atmosphere
6.1.1 General
The sample, kept in the form of a twisted hank, is exposed to the conditioning atmosphere for a minimum period as indicated below. This period can vary according to the type of the material and the sampling conditions.
Generally, regardless of the origin of the sample of sliver, the preliminary conditioning period is 24 h in the standard atmosphere for testing as defined in ISO 139.
In order to standardize the procedure, this period of 24 h may be adopted for all cases where no urgency exists.
6.1.2 For slivers coming from a process involving soaking, drying or oiling, a conditioning period of
24 h in standard atmosphere is to be observed.
6.1.3 For tops sampled in the normal way at a passage following combing, and drawing slivers and rovings sampled from a machine where fibre lubricant is not applied, the period of conditioning in standard atmosphere can be reduced to a minimum of 4 h.
6.1.4 In some cases, this period can be reduced still further; for instance, if a rapid conditioning enclosure is available in which the sample hank can be placed for 30 mm followed by a further 30 mm in the standard atmosphere.
6.1.5 The conditioning period may be omitted or reduced to a precautionary 30 mm when a combination of the following conditions occurs.
a) Sampling has taken place approximately within the 4 h prior to the test during processing or from balls stored in a satisfactory atmosphere.
b) The sample hank has been transported in a sufficient airtight plastic bag, avoiding any excessive heat or cold.
6.2 Testing atmosphere
The test is to be performed in the standard atmosphere for testing as defined in ISO 139.
7 SamplIng and preparation of laboratory sample
7.1 Sampling
Samples shall be taken from bales distributed equally throughout a lot. Only one sample shall be taken from a bale, unless the lot is smaller than 5 bales when an equal number of samples shall be taken from each bale.
To characterize a lot, take at least one sample from each of S homogeneous portions of the lot to form the total sample. For masses greater than 5 000 kg, at least one sample shall be added per 5 000 kg portion.
NOTE Homogeneous portion of the lot is a ball or bump of sliver, a can of drawing sliver, a roving bobbin, a sliver or roving taken directly from a finisher.
Samples shall not be taken for measurement from the disturbed outer layer, or immediately next to the core of a package. Slivers having adventitious thickness faults (especially abnormal thick or thin places) are to be discarded. Slivers taken directly from a comb, cut or chopped slivers and those containing fibre bundles are also unsuitable. In such cases, the variation in fibre length between successive samplings is likely to be very large, potentially giving rise to significant errors.
7.2 Preparation of laboratory sample
7.2.1 General
To obtain a suitable laboratory sample, fibres shall be under semi-relaxed state. To achieve this form, pre-treat laboratory samples according to Annex A.
7.2.2 Slivers of combed wool weighing between 15 g/m and 30 g/m
For slivers of combed wool weighing between 15 g/m and 30 g/m, a length of about 1,2 m is broken off from the homogeneous portion of the lot. Immediately after sampling, the sample held under slight tension is given 36 turns of twist (30 turns/rn); held taut in this condition, it is doubled at its centre and its ends are brought together and held. See Annex A for details.
In this form, the sample can be stored indefinitely and can easily be sent by post in a plastic bag, or held fast on a tube of approximate diameter 40 mm in the twisted state, to the testing laboratory.
For in-mill management, the operation of twisting may be omitted only when the ball of combed sliver or of roving is available at the moment of testing and if the test is going to be carried out within 4 h of sampling.
NOTE This twisting operation is absolutely essential in order to obtain accurate test results.
7.2.3 Rovings or slivers weighing less than 15 g/m
In the case of rovings or slivers weighing less than 15 g/m, sufficient 1,2 m lengths of sliver are successively drawn to build up, by overlaying, a sliver which weight per metre is about 22 g (30 g maximum). At the time of the overlaying, the slivers shall always be laid in the same direction (for example, the leading end as delivered by the mill machine always to the left).BS ISO 2648 pdf download.
